From <@VMS.DC.LSOFT.COM:owner-mednews@ASUVM.INRE.ASU.EDU> Sun Aug 20 14:52:19 1995 (LSMTP for OpenVMS v0.1a) with SMTP id BE224FCD ; Sun, 20 Aug 1995 14:43:14 - 1300 release 1.8b) with NJE id 8208 for MEDNEWS@ASUVM.INRE.ASU.EDU; Sun, 20 Aug 1995 11:41:06 -0700 (LMail V1.2a/1.8a) with BSMTP id 4281; Sun, 20 Aug 1995 11:41:05 - 0700 V2R3) with TCP; Sun, 20 Aug 95 11:41:01 MST (8.6.12/8.6.9) with UUCP id LAA01161 for mednews@asuvm.inre.asu.edu; Sun, 20 Aug 1995 11:18:38 -0700 mednews@asuvm.inre.asu.edu Comments: To: asumednews@stat.com HICNet Medical News Digest Sun, 20 Aug 1995 Volume 08 : Issue 26 Today's Topics: AIDS Summary The Differences in RK Surgery The Fundamentals of MRI and CT Scan [MMWR Jul14] Outbreak of Acute Gastroenteritis [MMWR] State Surveillance ... +------------------------------------------------+ ! ! ! Health Info-Com Network ! ! Medical Newsletter ! +------------------------------------------------+ Editor: David Dodell, D.M.D. 10250 North 92nd Street, Suite 210, Scottsdale, Arizona 85258-4599 USA Telephone +1 (602) 860-1121 FAX +1 (602) 451-1165 Internet: mednews@stat.com Bitnet: ATW1H@ASUACAD Mosaic WWW *Asia/Pacific: http://biomed.nus.sg/MEDNEWS/welcome.html *Americas: http://lab.xrt.upenn.edu:2000/hicn (good till June 1995) *Europe: http://www.dmu.ac.uk/ln/MEDNEWS/ Compilation Copyright 1995 by David Dodell, D.M.D. All rights Reserved. License is hereby granted to republish on electronic media for which no fees are charged, so long as the text of this copyright notice and license are attached intact to any and all republished portion or portions. The Health Info-Com Network Newsletter is distributed biweekly. Articles on a medical nature are welcomed. If you have an article, please contact the editor for information on how to submit it. 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Cross, B.S Health Care Admin, 882 Medical Trng Grp, USAF Albert Shar, Ph.D. CIO, Associate Prof, Univ of Penn School of Medicine Stephen Cristol, M.D. MPH, Dept of Ophthalmology, Emory Univ, Atlanta, GA Subscription Requests = mednews@stat.com anonymous ftp = vm1.nodak.edu; directory HICNEWS FAX Delivery = Contact Editor for information ---------------------------------------------------------------------- To: hicnews AIDS Daily Summary The Centers for Disease Control and Prevention (CDC) National AIDS Clearinghouse makes available the following information as a public service only. Providing this information does not constitute endorsement by the CDC, the CDC Clearinghouse, or any other organization. Reproduction of this text is encouraged; however, copies may not be sold, and the CDC Clearinghouse should be cited as the source of this information. Copyright 1995, Information, Inc., Bethesda, MD In this issue: ********************************************************************* "Providers Not Diagnosing HIV in Older Women" "Cyclosporin A" "PCP Therapy: Aerosolized Pentamidine vs. TMP-SMX" "Antiviral Conference Reports" "Herpesvirus-Like DNA Sequences in Non-Kaposi's Sarcoma Skin Lesions of Transplant Patients" "Exercise and HIV Infection" "HIV Risk-Related Behaviors among Injection Drug Users in Rome: Differences between 1990 and 1992" "Protection by Attenuated Simian Immunodeficiency Virus in Macaques Against Challenge with Virus-Infected Cells" "Itraconazole for Mild Histoplasmosis" "Search for HIV-1 Group O Infection in Nigeria" "Update: Trends in AIDS Among Men Who Have Sex with Men --United States, 1989-1994" "Transmission of HIV in Dialysis Centre" "Chinese Medicine: Where Does It Work Best in HIV/AIDS?" "Outcome of Patients with HIV Infection and Decreased Consciousness or Recurrent Seizures" "Outcome of Patients with HIV Infection and Decreased Consciousness or Recurrent Seizures" "Sensitization of T Cells to CD95-Mediated Apoptosis by HIV-1 Tat and gp120" "Mixed-Strain Infection with a Drug-Sensitive and Multidrug-Resistant Strain of Mycobacterium tuberculosis" ********************************************************************* "Providers Not Diagnosing HIV in Older Women" AIDS Alert (06/95) Vol. 10, No. 6, P. 77 The Centers for Disease Control and Prevention (CDC) in Atlanta reports that 10 percent of all women diagnosed with AIDS by June 1994 were more than 50 years old. "These are the invisible victims of the disease," says Patricia Fleming, head of the reporting and analysis division of the surveillance branch at the CDC's National Center for Infectious Diseases. Midlife-and-older women are not being diagnosed with AIDS until late in the disease process, sometimes not until death. According to Fleming, 43 percent of women over 65 with AIDS died within one month of diagnosis. A key factor for providers treating older women, she says, is to recognize that this group is now acquiring the disease through heterosexual contact, not just through transfusions. "Midlife and Older Women and HIV/AIDS" is the published report of an American Association of Retired Persons/Center for Women's Policy Studies seminar in 1993. The report raises the issues that--with older women and HIV--many behavioral and psychological risk factors are overlooked, diagnosis and treatment of HIV is complicated by other aging factors, and that socioeconomic and cultural factors limit patient access to care and treatment. "Cyclosporin A" Nature (05/18/95) Vol. 375, No. 6528, P. 198 Ho, David D.; Perelson, Alan S.; Shaw, George M. In response to letters to the editor of Nature, Ho et al. write that the letters' most important point concerns CD4 lymphocyte redistribution, rather than proliferation. Although lymphocyte re-trafficking is a possible explanation, several observations argue against it, the authors explain. First, the increases in CD4 levels were not temporary, but sustained as long as the antiviral effect was maintained. Second, studies have shown that increases in CD4 counts associated with viral suppression were associated with significant clinical improvement. Third, recent unpublished studies by the authors demonstrate that the surface-marker phenotypes of CD4 lymphocytes post-therapy differ greatly from those before treatment. Our preliminary findings reveal the expression of several activation markers on many of the CD4 lymphocytes after treatment--a finding which supports lymphocyte repopulation by cellular proliferation, but argues against lymphocyte redistribution, Ho et al. conclude. "PCP Therapy: Aerosolized Pentamidine vs. TMP-SMX" AIDS Clinical Care (06/95) Vol. 7, No. 6, P. 51 As part of a randomized study of treatments for Pneumocystis carinii pneumonia (PCP), researchers assigned 367 patients to 21 days of treatment with either aerosolized pentamidine or trimethoprim-sulfamethoxazole (TMP-SMX). Each group also received placebos imitating the opposite treatment. After 35 days, mortality in the TMP-SMX group was higher, but not enough to be statistically significant. However, significantly more TMP-SMX recipients changed therapy because of toxicity, while significantly fewer did so because of slow clinical response. The greatest difference in response was among patients with an initial alveolar-arterial oxygen gradient greater than 30 mm Hg. After six months, there were fewer PCP recurrences with TMP-SMX, but the survival rates for the two drugs were almost identical. The researchers concluded that TMP-SMX appears to lead to more rapid improvements in oxygenation, more treatment successes, and fewer relapses than aerosolized pentamidine, but they are not sure why it did not also reduce mortality. "Antiviral Conference Reports" AIDS Treatment News (05/19/95) No. 223, P. 4 James, John S. Following the Eighth International Conference on Antiviral Research, 256 abstracts of the drugs presented at this conference were submitted to the March 1995 issue of Antiviral Research, some of which are mentioned below. NIM 811, a derivative of cyclosporin, has no immune suppressive activity, but is still active against HIV, according to research conducted by Sandoz. Ingenol, a compound derived from the dried roots of Euphorbia Kansui Liou, inhibits HIV in extremely low concentrations of .1 nanomolar, which is thousands of times less than the amount of AZT required. Although chemically related to carbovir, Burroughs-Wellcome's 1592U89 is more active against HIV, more bioavailable, and can penetrate the brain more easily. PMEA is chemically related to the anti-CMV drug cidofovir (HPMPC); however, PMEA is active against HIV as well as CMV and other herpes viruses. In addition to treating alcoholism, Antabuse targets the "zinc fingers" in HIV proteins. PETT compounds in the non-nucleoside RT inhibitors (NNRT) series cause HIV resistance to develop ten times faster than they do with other non-nucleoside compounds. In addition, a new series of NNRTs was found to cause different mutations than known NNRTs and delay the development of resistant HIV in combination with other drugs. As an approved drug for treating CMV, foscarnet also has anti-HIV activity when combined with AZT and non-nucleoside RT inhibitors. Furthermore, different ratios AZT and ddI were tested for the biochemical activation of these drugs in cells. "Herpesvirus-Like DNA Sequences in Non-Kaposi's Sarcoma Skin Lesions of Transplant Patients" Lancet (05/27/95) Vol. 345, No. 8961, P. 1339 Rady, Peter L..; Yen, Angela; Rollefson, Janice L. et al. To determine whether herpesvirus-like DNA sequences (KSHV) were associated with proliferative skin lesions not caused by Kaposi's sarcoma in non-AIDS immunocompromised patients, Rady et al. tested 33 skin lesions from 4 HIV-negative organ-transplant patients receiving immunosuppressive therapy. Using polymerase chain reaction (PCR), KSHV sequences were identified in more than 80 percent of these lesions. The two most frequent lesions tested were actinic keratosis (AK) and squamous cell carcinoma (SCC). The prevalence of KSHV was 78 percent in AKs and was 93 percent in SCCs. The researchers concluded that KSHV is related to lesions other than KS in non-AIDS immunocompromised patients, and may also be implicated in the pathogenesis of various kinds of proliferative skin lesions in organ-transplant patients. "Exercise and HIV Infection" Advocate (05/30/95) No. 682, P. 49 Cohan, Gary R. Increasingly, studies of HIV-infected people indicate that regular physical exercise offers significant health benefits. Scientists have found that a lean body mass is strongly correlated with survival in people with AIDS. Indeed, the timing of death in AIDS patients has been found to be directly related to the amount of lean body weight loss--independent of T-cell levels or specific opportunistic infections. To date, most efforts to halt the wasting process have concentrated on treating underlying gastrointestinal disorders, stimulating the appetite with drugs, and providing extra calories. While these treatments do increase body weight, the gain is mostly fat and water. Common sense and current research, however, support the theory that one must perform some sort of physical activity to convert these calories and hormones into lean body mass. Exercise can also help HIV-infected people maintain or improve their ability to perform daily activities, increase energy, improve appetite, and elevate mood. Most experts agree that people at risk for HIV-related wasting syndrome should focus on resistance training, and avoid burning too many calories. "HIV Risk-Related Behaviors among Injection Drug Users in Rome: Differences between 1990 and 1992" American Journal of Public Health (06/95) Vol.85, No.6, P.829 Davoli, Marina; Perucci, Carlo A.; Abeni, Damiano D. et al. The primary risk factor for HIV-1 infection and AIDS in Italy is injection drug use, accounting for about two-thirds of the total AIDS cases reported by the end of June 1994. Between 1990 and 1992, Davoli et al. analyzed injection drug users (IDUs) to better understand the temporal trends in HIV risk-related behaviors. An understanding of these trends may help in verifying the effectiveness of prevention activities, planning more appropriate education and treatment interventions, and providing estimates for the future of the epidemic. From 1990 to 1992, syringe-sharing decreased among self-reported HIV-infected IDUs, although there was no change in their sexual behavior. By the end of the study, fewer HIV-seronegative IDUs reported sharing needles than in 1990. There was, however, no change in the percentage of seronegative users using previously used syringes, and a reduction in condom use with primary partners was seen. The researchers concluded that there is still a great potential for HIV transmission among IDUs and from IDUs to the general public. "Protection by Attenuated Simian Immunodeficiency Virus in Macaques Against Challenge with Virus-Infected Cells" Lancet (05/27/95) Vol. 345, No. 8961, P. 1342 Almond, N.; Kent, K.; Cranage, M. et al. Almond et al. of England's National Institute for Biological Standards and Control tried to determine if different attenuated, or weakened, strains of simian immunodeficiency virus (SIV) could protect against pathogenic isolates, and if such protection would be effective against cell-associated and cell-free virus challenge. In the study, eight cynomolgus macaques were vaccinated with attenuated cell-free and cell-associated SIV. These eight were protected, while the eight controls became infected after the challenge. According to the researchers, the results demonstrate that a live-attenuated vaccine can offer protection from SIV in macaques. For use in humans, however, this method will require an extensive study of the safety of human retroviruses. Alternatively, the mechanism of this protection must be understood and reproduced in a less hazardous fashion. "Itraconazole for Mild Histoplasmosis" AIDS Clinical Care (06/95) Vol. 7, No. 6, P. 51 In an uncontrolled study of 59 AIDS patients, researchers found that oral itraconazole can be an effective alternative to the toxic and expensive amphotericin B for the treatment of mild histoplasmosis. Compared to the historical controls given for amphotericin B, the rate of clinical response with clearance of positive cultures was 85 percent for itraconazole. Although fungemia cleared quickly with itraconazole, resolution of fever and clearance of antigen were slower compared to amphotericin B. The researchers concluded that itraconazole is safe and effective induction therapy for mild histoplasmosis, but that it may be better to continue using amphotericin initially, especially in patients with any of the risk factors associated with itraconazole failure. "Search for HIV-1 Group O Infection in Nigeria" Lancet (06/03/95) Vol. 345, No. 8962, P. 1436 Dada, Abinbola; Olumide, Yetunde M.; Henrard, Denis R. et al. Dada et al. selected 248 serum samples from commercial sex workers and patients seen at clinics in Lagos to be tested for HIV-1 group O. Of the 182 samples that were reactive to an enzyme-linked immunoassay (EIA), 61 were HIV western-blot positive, 73 were indeterminate, and 48 tested negative. The other 66 tested EIA negative but had varying numbers of bands. The samples were sent to Chicago's Abbott Laboratories and to the Centers for Disease Control and Prevention (CDC) for HIV-1 group O testing. At Abbott Laboratories, the samples were tested by the Clonatech HIV (1+2) EIA, which is generally non-reactive with group O. A total of 94 had negative Clonatech results. Forty of these 94 were further analyzed for type O reactivity using "consensus" group O specific peptides for the gp41 area of HIV-1, but none had group O peptide reactivity. At the CDC, the samples were screened by Genetic System's HIV 1/2 EIA. Sixty-two tested positive for HIV. These samples also had no group O reactivity when tested with EIAs based on synthetic peptides derived from the V3 loop of the envelope proteins representing group O. "Update: Trends in AIDS Among Men Who Have Sex with Men --United States, 1989-1994" MMWR(06/02/95) Vol. 44, No. 21, P. 401 Almost 35,000 cases of AIDS among men whose only reported exposure to HIV was sexual contact with other men were reported to the Centers for Disease Control and Prevention in 1994. Between 1989 and 1994, rates of AIDS-defining opportunistic infections (AIDS-OIs) for men who have sex with men (MSM) rose more than 30 percent from 12.1 to 15.9 cases per 100,000 males over the age of 13. Geographically, there were significant increases in the Midwest and South, while smaller increases were seen in the West and the Northeast during that five year period. There were also varying increases by race and ethnicity. Proportionately, the greatest leaps were seen among black, Hispanic, American Indian/Alaskan Native, and Asian/Pacific Islander males with 79 percent, 61 percent, 77 percent, and 55 percent increase, respectively. Finally, there were substantial differences in rates according to the size of the metropolitan statistical area (MSA). During 1989, for example, the rates were lowest in rural areas. These areas, as well as MSAs with populations between 50,000 and 1 million, had the highest percentage increase. ·_ "Transmission of HIV in Dialysis Centre" Lancet (06/03/95) Vol. 345, No. 8962, P. 1417 Velandia, Martha; Fridkin, Scott K.; Cardenas, Victor et al. Between January 1992 and December 1993, Velandia et al. conducted a cohort study to determine the risk factors for HIV seroconversion at a dialysis center in Colombia, South America. The investigation was prompted by the discovery of 13 HIV-infected patients at the center in August 1993. Of the 23 patients studied, 12 tested positive for the HIV antibody during the epidemic period. The rate of seroconversion was higher among patients dialysed at the center while a new HIV seropositive patient received treatment there, or when the center reprocessed access needles, dialysers, and bloodlines. Only two of the nine HIV seroconverters had HIV risk factors--both having had sex with prostitutes. The researchers verified that HIV transmission took place at the dialysis center. The probable method of transmission, they said, was improperly reprocessed patient-care equipment, most likely access needles. They cautioned that because this outbreak was discovered accidentally, similar transmission could be occurring in many other countries where low-level disinfectants are used to sterilize critical patient-care equipment. "Chinese Medicine: Where Does It Work Best in HIV/AIDS?" AIDS Treatment News (06/02/94) No. 224, P. 8 For three years, Chinese medical treatment in San Francisco has been funded by the Ryan White CARE Act, and the American College of Traditional Chinese Medicine there has treated more than 300 symptomatic HIV-positive individuals in long-term care. The conditions which appear to be the most responsive to Chinese medicine are weight loss, diarrhea/loose stools, abdominal pain, nausea, headaches, enlarged lymph nodes, and neuropathy. Many insurers and other third-party payers are now covering "alternative" methods, such as traditional Chinese medicine. Alternative care usually costs much less than Western medicine, and companies can save money by paying for it. "Outcome of Patients with HIV Infection and Decreased Consciousness or Recurrent Seizures" JAMA (06/14/95) Vol. 273, No. 22, P. 1738 Bedos, Jean-Pierre In response to a letter to the editor of the Journal of the American Medical Association, Jean-Pierre Bedos asserts that "neurological failure" is the correct term for his study, which involved HIV-infected patients treated in an intensive care unit (ICU). Although the phrase is imprecise and simplistic in a diagnostic setting, Bedos believes that his inclusion criteria were logical and well-suited to the patients in whom altered consciousness and convulsions were the two primary neurological reasons for hospital admission. Patients with isolated neurological disorders--such as aphasia, hemiparesis, and hemianopsia--who were not part of the group of patients admitted to the ICU with altered consciousness were not the focus of the study. Bedos concludes that, while nonspecific, the term "neurological failure" can be appropriate inclusion criterion for prognostic studies of HIV-positive patients admitted to ICUs. "Sensitization of T Cells to CD95-Mediated Apoptosis by HIV-1 Tat and gp120" Nature (06/08/95) Vol. 375, No. 6531, P. 497 Westendorp, Michael O.; Frank, Rainer; Ochsenbauer, Christina et al. The reduction of CD4 T cells in AIDS is associated with the rapid turnover of HIV-1 and apoptosis. Although the molecular mechanism of HIV-related apoptosis is unknown, T-cell apoptosis may be affected by viral proteins--such as HIV-1 Tat and gp120--and T-cell-receptor (TCR)-induced apoptosis was recently shown to involve the CD95 (APO-1/Fas) receptor. Westendorp et al. demonstrate that HIV-1 Tat strongly sensitizes TCR- and CD4(gp120)-induced cell death by upregulation of CD95 ligand expression. They observed that Tat concentrations that were effective in cultures of HIV-1-infected cells were also found in blood samples from HIV-infected patients. The findings suggest that HIV-1 Tat and gp120 hasten CD95-mediated, activation-induced T-cell apoptosis, a mechanism which may contribute to AIDS-related CD4 T-cell depletion. "Mixed-Strain Infection with a Drug-Sensitive and Multidrug-Resistant Strain of Mycobacterium tuberculosis" Lancet (06/10/95) Vol. 345, No. 8963, P. 1512 Theisen, A.; Reichel, C.; Rusch-Gerdes, S. et al. In a letter to the editor published in the Lancet, Theisen et al. present the case of a patient infected with two different strains of Mycobacterium tuberculosis, one drug-sensitive and one multidrug-resistant (MDR). After being diagnosed with M. tuberculosis, a 24-year-old Nepalese patient was administered quadruple therapy with isoniazid, rifampicin, ethambutol, and pyrazinamide. After 29 days, therapy with pyrazinamide was stopped because of substantial hepatoxicity. The sensitive strain was repeatedly cultured until day 57 of treatment, at which time the specimens tested negative. On day 100, a sputum sample was again positive for tuberculosis (TB), and was now resistant to rifampicin and isoniazid. DNA fingerprinting with the mixed-linker polymerase chain reaction (PCR) technique showed the isolate to be completely different from the initial drug-sensitive one. The patient improved significantly after being switched to triple therapy with pyrazinamide, ethambutol, and prothioamide. The researchers believe that the incidence of MDR TB was due to coinfection with two wholly different strains. They recommend repeated resistance testing, particularly in patients with delayed response to therapy and in those who come from high prevalence areas for MDR TB. ------------------------------ To: hicnews [Image] The Differences in Radial Keratotomy Surgery Refractive surgery has received tremendous attention by the press, produced wide interest among patients, and has embraced a large percentage of the ophthalmic community. The main focus (no pun intended) is to correct myopia or nearsightedness, a condition that affects nearly one-fourth of the world's population. In refractive surgery we change the optical properties so that patients no longer require spectacles to see at distance. Figure 1 is a schematic of a normal or emmetropic eye (no correction necessary for clear distance vision). In myopia the aberrant optical system results in the light rays being focused in front of the retina. Myopia can be corrected by flattening the cornea so that is has less converging power. Radial keratotomy and excimer laser are the two most popular approaches. In radial keratotomy a series of deep, radial incisions are made in the cornea and result in peripheral steeping and central flattening. The desired refractive change is typically controlled by adjusting the number or the length of the incisions. The objective is to obtain the desired effect without causing an overcorrection and thus pushing patients into an over corrected or farsighted state. Surgical decisions are based on statistical analysis of a large number of previous surgical procedures. RK can now be done in a relatively precise manner with rather early visual rehabilitation of the patients. The excimer is currently an investigational device. The laser is currently under clinical study in the United States (FDA approval anticipated by many within the next 3-12 months), while it is estimated that over 200,000 cases have been performed throughout the world. This laser emits energy at 193 nanometers which causes photochemical breakdown of the corneal tissue and thus ablates or vaporizes tissue with minimal surrounding thermal damage. Delivery systems have been designed which permit the laser to shape the surface of the cornea much like one would lathe a correction on a contact lens. This allows the surgeon to flatten the central cornea and decrease the optical power of the cornea in a relatively precise manner. At present we have an ongoing clinical study in radial keratotomy and are performing basic research studies with the Summit excimer laser. We anticipate that we will participate in an FDA sponsored trial of a new "second generation" excimer laser (the Schwind Keratom distributed by Coherent, Inc) in the fall of 1995. Our research interests focus on evaluating the safety and effectiveness of both modalities of surgery. In our radial keratotomy study, we have three objectives: 1) We are studying the effects of RK on visual performance as measured by contrast sensitivity testing (the ability to distinguish sinusoidal wave patterns of increasing frequency). This addresses a different aspect of visual performance than tested with the high contrast Snellen acuity ("E") chart as typically used in the doctor's office. 2) We are measuring the surface topography of the cornea to determine whether problems of under correction can be ascribed to individual incisions so that any additional surgery to "enhance" the effect can focus on the individual under corrected incisions. 3) Finally, we are taking the topographical analysis data and performing sophisticated ray tracing analysis. We compute the actual position on the retina of individual light rays that are refracted by the eye. This allows us to predict the visual performance based on the corneal topography and centration of the procedure on the cornea. Our overall outcomes with RK have been favorable with 100 percent of patients 20/40 or better without correction and no major complications. We have shown that centration of the procedure on the entrance pupil is important for optimizing visual performance in the mid-range frequency of contrast sensitivity testing. This is contrary to what some experienced surgeons have taught and should provide a scientific basis for developing optimum centering procedures. We have also been very active in the basic investigation (non-clinical use) of the excimer laser. Although our Summit excimer has recently been approved for therapeutic keratectomy (removal of scars and surface irregularities) and FDA approval for refractive keratectomy has not yet occurred. Worldwide reports of clinical results with the first generation lasers are very similar to RK. Approximately 92 percent of eyes are 20/40 or better without correction. However, there is room for improvement. Approximately 3 percent of patients lose a significant amount of best corrected visual acuity and 8 percent remain significantly over or under corrected. We have been involved with Coherent Lasers in the development of their new second generation laser, the Keratom. This laser can treat myopia as well as astigmatism. A number of advances, such as computer centration of the procedure, intraoperative eye tracking and enlarged ablation zones, should provide more precise surgery with more consistent results in a greater range of myopes. The early data from foreign countries with the Schwind Keratom Laser shows 98 percent of the patients are 20/40 or better, with less than 1 percent loss of two lines or more best corrected visual acuity. A second major advance that is planned to be incorporated in the upcoming clinical trial of the Coherent Laser is LASIK (laser assisted in situ keratomieleasus). In this procedure, a thin flap of tissue is sectioned from the surface of the cornea and left attached with a thin adherent rim or hinge of tissue. The underlying stromal tissue is then treated very precisely with the laser and the superficial flap is then replaced back on top of the cornea. This results in a very predictable refractive correction with minimal scarring and pain with almost immediate visual rehabilitation. Patients with low to moderately high myopia can be corrected. Our personal experience with this technique is limited to patients we examined in Mexico. These patients did not experience pain and had excellent outcomes. Their surfaces were healed within 24 hours and it was difficult to even find the incision. The results from elsewhere in the world are outstanding. I believe that this may be the best refractive technique that the future holds and anxiously await the results of new FDA sponsored clinical trials. Robert W. Snyder, M.D., Ph.D. The University of Arizona Head, Department of Ophthalmology ------------------------------ To: hicnews [Image] Understanding the Fundamentals of Magnetic Resonance Imaging and Computed Tomography There are three principle cross-sectional diagnostic imaging techniques, ultrasound, magnetic resonance imaging (MR) and computed tomography (CT). Cross-sectional imaging refers to techniques which produce planar images as cross-sections of the patients' anatomy. Conventional radiographic images are projections where many anatomic structures are superimposed (e.g. heart, mediastinum, lung tissue, spine and soft tissues on a chest X-ray). As such, overlapping shadows on radiographs may obscure disease processes. Cross-sectional images eliminate overlapping shadows to produce images rivalling anatomic dissections. Briefly, ultrasound uses high frequency sound wherein the reflected sound is used to create anatomic images. The technique is portable, relatively inexpensive and sensitive to vascular flow. Ultrasound needs an acoustic window for transmitting the sound; it cannot effectively transmit through air (e.g. the lung) nor through bone. MR uses a strong magnetic field (e.g. 10,000 X stronger than the earth's magnetic field to energize the protons in water). Radiofrequency (RF) pulses are applied to force the hydrogen nuclei into a higher energy state, and when the protons return to the ground state, signals are emitted from the hydrogen nuclei. These signals are received by a coil, in essence an antenna, and formatted into an image by a computer. The rate at which signals grow is related to T1, the longitudinal relaxation time of the protons, and the rate at which the signals decay is described by T2, the transverse relaxation time. The other principal variable is proton density the concentration of mobile protons available to create signal. We make the image using different pulse sequences (the timing at which the RF and electrical gradients are applied) to maximize image contrast for selected applications. On T1 weighted images, structures with the shortest T1 appear brightest. Short T1 confers high signal. Fat is usually the brightest structure on T1 weighted images and tumors usually appear dark. On T2 weighted images, the structures with the longest T2 will appear brightest the longer the T2 the more slowly the signal decays. Pure water has the longest T2. Tumors tend to have increased water relative to other tissues and therefore generally appear bright on T2 weighted images. MR is non-invasive and has been shown to be a safe imaging technique. MR produces images in any scan plane (e.g. sagittal, coronal or axial). For neurological (CNS) applications MR has mainly replaced CT for oncologic imaging. For the body outside of the CNS, MR is often ancillary to CT because MR takes a few minutes to acquire the images. During this time physiological motion occurs and degrades the images. The CNS moves much less than the abdomen or chest and accordingly the images are generally better in the CNS. At this time MR is still useful in the chest, abdomen and pelvis for selected applications (e.g. in the liver to diagnose hemangioma MR is probably the exam of choice). MR is currently getting faster and MR angiography more robust. Functional MR imaging has evolved as a tool for mapping the cerebral cortex and studying tissue oxygenation. MR is also being developed as a technique for minimally invasive surgery. CT is an older and more mature imaging technology than MR. CT uses X- rays to create axial images. The X-ray tube rotates around the patient within the CT scanner gantry. In conventional CT the tube rotates around the patient once with the table position fixed. After tube rotation, the table is advanced a fixed distance (e.g. 8 or 10 mm) and the next slice is acquired. The slice thickness is controlled by collimators which define the thickness of the X-ray beam. In CT, contrast depends upon the electron density of the subject being scanned. Air has the lowest density and hence the lowest attenuation and appears black on CT. Cortical bone is generally the most attenuating structure and hence appears the densest or whitest on CT. Density on CT is often described by Hounsefield Units (Sir Hounsefield, a British scientist invented CT). Pure water measures 0 Hounsefield Units or HU and air - 1,000 HU. Very dense structures such as cortical bone might approach +1,000 HU. Occasionally we use HU values to characterize a tissue, for example a benign renal cyst should be near water density (0 HU) but for practical purposes would probably be no more than 20 HU. Benign granulomas in the lung are generally diffusely calcified and over 175 HU on CT. As stated above, on CT, density depends upon electron density of the tissue, and for soft tissues CT density is directly proportional to the specific gravity of the tissue. This holds for soft tissues where the dominant nuclei are hydrogen, oxygen and nitrogen. In bones however, calcium causes much greater absorption of X-rays. Calcium and other heavy atomic elements interact with the X-rays differently than soft tissues. Heavy nuclei absorb the X-rays through a process called the photoelectric effect; this is proportional to the atomic number of the element cubed. Because of its high atomic number, iodine is a very effective X-ray absorber. Iodinated biocompatible compounds are therefore used as X-ray contrast agents to increase contrast between vascularized and less well vascularized tissues on CT. The speed of conventional CT is limited by the time it takes to perform each scan to acquire a slice as well as the time necessary for table incrementation. A fast conventional CT scanner might take a second to acquire a scan and two seconds for table incrementation. Therefore, much of the imaging time is spent not scanning but waiting in between scans. It is desirable to scan quickly for several reasons. When X-ray contrast is used, as is most often the case on CT, it rapidly washes out into the other tissues. When this happens, the image contrast is lost (e.g. ability to detect tumors is impaired). When time occurs in between scans, we may miss an important lesion, for example in a cancer patient who breathes differently between two scans, a nodule might be missed. To maximize contrast and minimize motion it is best to scan as quickly as possible. Spiral CT uses continuous table feed with continuous X-ray tube rotation to scan much more quickly than conventional CT. Other than these changes and some software and minor hardware modifications, spiral CT functions similarly to conventional CT. Because of its speed and ability to capture the X-ray contrast while it is in its arterial phase, spiral CT can be used to perform CT angiography (CTA). Although the images are acquired axially, they can be reformatted into any plane. CTA is already making a significant clinical impact. CTA can be performed with intravenous injections of contrast which is less invasive than standard arteriography. Also, CTA can readily be correlated with the anatomic CT images. The fastest CT technique is cine CT (Imatron). Cine CT uses an electron beam which is swept around a fixed anode target ring positioned around the patient. There are no moving parts as in the X-ray tube in the conventional ·_ or spiral CT scanners. Cine CT can acquire up to 4 slices simultaneously in under 50 msec per image. The technique has robust cardiac and pulmonary applications. In conclusion, we are fortunate in modern medicine to have cross- sectional imaging techniques such as ultrasound, MR and CT. These techniques allow us to non-invasively see inside the bodies of our patients. Each technique has its own advantages and limitations. We as radiologists must work together with our clinical colleagues to select the best exam and to perform it appropriately. Evan Unger, M.D. Associate Professor of Radiology Director Cross Sectional Imaging ------------------------------ To: hicnews Outbreak of Acute Gastroenteritis Attributable to Escherichia coli Serotype O104:H21 -- Helena, Montana, 1994 During February-March, 1994, four persons in Helena, Montana (1995 population: 24,569), developed bloody diarrhea and severe abdominal cramps. Stool cultures for Salmonella, Shigella, Campylobacter, and Escherichia coli O157:H7 were negative; however, sorbitol-negative E. coli colonies were identified in stools from all four patients. Isolates from three patients were identified at CDC as a rare serotype--E. coli O104:H21 that produced Shiga-like toxin II. This report summarizes the epidemiologic and laboratory investigations of this outbreak by the Lewis and Clark County Department of Health and Environmental Sciences, the Montana Department of Health and Environmental Sciences (MDHES), and CDC. A confirmed case was defined as acute infection with E. coli O104:H21 during February 20-May 25, 1994--based on stool culture or serologic evidence--in a resident of or a visitor to the Helena area. A suspected case was defined onset of bloody diarrhea or abdominal cramps during the same period in a resident of or visitor to the Helena area. MDHES and county health departments contacted clinicians, laboratories, and the public through news media reports and requested that suspected cases be reported. Eleven confirmed and seven suspected case-patients were identified (Figure 1). Manifestations included abdominal cramps (18 [100%]), diarrhea (17 [94%]), bloody stools (16 [89%]), vomiting (10 [56%]), and fever (six of 15 [40%] for whom information was available). The median age was 36 years (range: 8-63 years), and 12 (67%) were female. Four (22%) persons were hospitalized. Potential sources and risk factors for illness were assessed by a case-control study that included 17 case-patients and three age-, sex-, and neighborhood-matched controls for each case-patient. A history of milk consumption during the 7 days before illness was reported by all 17 case-patients compared with 40 (83%) of 48* controls (matched odds ratio [OR]=undefined). One brand of milk (Brand A) was significantly associated with illness: of those persons who drank milk at home, 11 (92%) of 12 case-patients compared with 17 (47%) of 36 controls reported drinking Brand A (matched OR=16.0; 95% CI=1.3-492.7). Within this brand, no specific type of milk product was associated with illness. Factors not associated with illness included consumption of other brands of milk, other foods or drinks, and dining in specific restaurants. On May 16, the local and state health departments, the Food and Drug Administration, and CDC inspected the dairy plant where Brand A milk was produced. Based on review of the plant's records for internal microbiologic quality-control testing, on 12 days during February 1-May 13, 1994, the coliform count exceeded the state regulation limiting maximum coliform levels in milk products to less than or equal to 10 coliforms per 100 mL on at least one ready-for-sale milk product. Cultures from selected post-pasteurization piping and equipment surfaces in contact with finished milk products yielded fecal coliforms; however, E. coli O104:H21 was not isolated from any culture samples obtained at the dairy. Two farms provided raw milk for this dairy; rectal swabs obtained from a sample of cattle from these farms did not yield E. coli O104:H21. Reported by: K Moore, Lewis and Clark County Dept of Health and Environmental Sciences; T Damrow, PhD, State Epidemiologist, Montana Dept of Health and Environmental Sciences; DO Abbott, PhD, Montana State Public Health Laboratory. S Jankowski, Microbiology Dept, St. Peter's Community Hospital, Helena. Foodborne and Diarrheal Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC. Editorial Note: Shiga-like toxin-producing E. coli (SLTEC) are well-recognized causes of gastrointestinal illness, including both bloody and nonbloody diarrhea. E. coli O157:H7, the most common SLTEC, was recognized as a human pathogen in 1982 during the investigation of two outbreaks of bloody diarrhea associated with consumption of commercially sold hamburgers (1). In addition to causing bloody diarrhea, E. coli O157:H7 is the most common cause of hemolytic uremic syndrome (HUS) in children. Although other SLTECs also have been identified in sporadic cases of diarrhea and HUS, the findings in this report document the first reported outbreak of a non-O157 SLTEC in the United States, and the first documentation of illness attributable to Shiga-like toxin-producing E. coli O104:H21. The clinical manifestations of infection in this outbreak were similar to those reported for patients infected with E. coli O157:H7 (2). Although HUS is a well-recognized complication of E. coli O157:H7 infection, no patients developed HUS in this outbreak, possibly reflecting the limited size of the outbreak and the age distribution of patients. Although most outbreaks of E. coli O157:H7 infection have been associated with consumption of ground beef, raw milk also transmits this pathogen (3). Healthy cattle may serve as a reservoir for E. coli O157:H7 and other serotypes of SLTEC (4). The implication of milk in the outbreak in Montana suggests that cows were the original source of this specific strain of E. coli O104:H21. Although the investigation documented post-pasteurization contamination of milk products with fecal coliforms, E. coli O104:H21 was not isolated from cultures obtained at the dairy, possibly because not all post-pasteurization equipment surfaces were sampled or because of the absence of the pathogen within the dairy at the time of the inspection. Because the techniques used to identify non-O157 SLTEC are not available in most laboratories (3), infections caused by this pathogen are most likely to be unrecognized. Most clinical laboratories that test for E. coli O157:H7 screen stools on a special medium (sorbitol-MacConkey agar [SMAC]) because E. coli O157:H7 isolates do not ferment sorbitol after overnight incubation (5), and most laboratories routinely discard sorbitol-positive colonies and sorbitol-negative colonies that do not agglutinate in O157 antiserum. Therefore, isolates of E. coli O104:H21 and other non-O157 SLTEC are not recognized. The increased availability in clinical laboratories of techniques such as testing for Shiga-like toxin or the genes encoding this protein may enhance the detection of disease attributable to non-O157 SLTEC. When evaluating clusters of patients with bloody diarrhea and other severe diarrheal illness, health-care providers also should consider the potential roles of E. coli O104:H21 or another non-O157 SLTEC. When cultures of stool are negative for specific pathogens, the state health department can be contacted to determine whether specimens should be examined further for SLTEC. When advised, health-care providers should freeze fecal specimens and store isolates from patients with bloody diarrhea; such specimens may assist in a subsequent investigation. References 1. Riley LW, Remis RS, Helgerson SD, et al. Hemorrhagic colitis associated with a rare Escherichia coli serotype. N Engl J Med 1983;308:681-5. 2. Griffin PM, Ostroff SM, Tauxe RV, et al. Illnesses associated with Escherichia coli O157:H7 infections. Ann Intern Med 1988;109:705-12. 3. Griffin PM. Escherichia coli O157:H7 and other enterohemorrhagic Escherichia coli. In: Blaser MJ, Smith PD, Ravdin JI, Greenberg HB, Guerrant RL, eds. Infections of the gastrointestinal tract. New York: Raven Press, 1995:739-61. 4. Wells JG, Shipman LD, Greene KE, et al. Isolation of Escherichia coli serotype O157:H7 and other Shiga-like toxin-producing E. coli from dairy cattle. J Clin Microbiol 1991;29:985-9. 5. March SB, Rutnam S. Sorbitol-MacConkey medium for detection of Escherichia coliO157:H7 associated with hemorrhagic colitis. J Clin Microbiol 1986;23:869-72. * Persons who responded "Don't know" to any question were excluded from the analysis. ------------------------------ To: hicnews Statewide Surveillance for Antibiotic-Resistant Bacteria -- New Jersey, 1992-1994 The increasing occurrence of infection with antibiotic-resistant microorganisms and other emerging infectious diseases has required the development of flexible and timely surveillance systems for monitoring these problems (1,2). To determine the extent of antibiotic resistance in New Jersey, in 1991 the New Jersey State Department of Health (NJSDOH) initiated a hospital laboratory isolate-based surveillance system for antimicrobial-resistant bacteria. This report describes the surveillance system and summarizes findings during 1992-1994 for vancomycin-resistant enterococci (VRE)--the most rapidly increasing antibiotic-resistant bacteria reported by New Jersey hospitals. The surveillance system includes the 95 acute-care hospitals licensed by the state of New Jersey. Organisms targeted for surveillance include gram-positive cocci resistant to vancomycin, including VRE; methicillin-resistant Staphylococcus aureus (MRSA); gram-negative rod-shaped bacteria (GNRs) resistant to imipenem; GNRs resistant to amikacin; and pneumococcal and other streptococcal isolates resistant to penicillin. Hospitals submit to NJSDOH monthly a surveillance report form, which includes the number of in-patient bloodstream isolates of these organisms and MRSA isolates from any body site. The New Jersey Administrative Code, which addresses communicable diseases, and state hospital licensure standards were modified in 1990 to require hospitals to submit these data to NJSDOH. Hospitals are contacted by the surveillance system coordinator to ensure monthly reporting; since the surveillance system was initiated, all hospitals have submitted monthly reports (3). During 1992-1994, a total of 5916 (81%) bloodstream isolates reported to this system were MRSA. Of the 1398 non-MRSA bloodstream isolates, 663 (47%) were VRE. During this period, both the number of hospitals reporting VRE blood isolates and the number of VRE isolates increased steadily: in 1992, 33 hospitals reported 99 isolates, while in 1994, 54 hospitals reported 278 isolates (Figure 1). Most of the monthly reports (73%) represent only one reported isolate per hospital. In 1992, hospitals in 13 of the 21 counties reported VRE isolates, compared with 20 of 21 counties in 1994. Reported by: SM Paul, MD, L Finelli, DrPH, G Crane, MPH, KC Spitalny, MD, State Epidemiologist, New Jersey State Dept of Health. National Center for Infectious Diseases, CDC. Editorial Note: The recent national emphasis on emerging infectious diseases has underscored the problem of antibiotic resistance involving a variety of nosocomial and community-acquired infections and has focused attention on the importance of microbiology laboratories as sources of surveillance information for antibiotic resistance (1,2). For example, in New Jersey, the increase in both the number of VRE blood isolates and the number of hospitals reporting VRE blood isolates from 1992 through 1994 suggests the emergence of the problem of VRE in that state. Careful monitoring of such trends in antibiotic resistance in enterococci and other organisms assists clinicians in selecting antibiotics for their patients and public health agencies in the development and implementation of prevention efforts. In New Jersey, laboratory-based surveillance for VRE and other antibiotic-resistant isolates has been developed through collaboration between the NJSDOH, hospitals, and infectious disease professionals in the state and because of modification of reporting regulations. The New Jersey system uses data that are routinely collected and collated by hospital laboratories and requires few additional resources. Because this surveillance system is isolate-based, it does not directly measure changes in the rate of infection in persons, and NJSDOH has used this system primarily for sentinel purposes to guide further investigation. For example, early detection and geographic tracking of VRE in New Jersey through this system have facilitated collaborative efforts involving public and private sector and academic organizations to evaluate risk factors for VRE, treatment options, VRE in vitro susceptibility to antimicrobial agents before clinical trials, and the effectiveness of infection-control practices (4-7). These efforts have, in turn, enabled the NJSDOH to collaborate with professional organizations (the Infectious Diseases Society of New Jersey and the New Jersey chapters of the Association for Professionals in Infection Control and Epidemiology) to develop recommendations to prevent VRE transmission and have provided a source of bacterial isolates to assist in research efforts to develop effective antimicrobial agents against VRE. References 1. Institute of Medicine. Emerging infections: microbial threats to health in the United States. Washington, DC: National Academy Press, 1992. 2. CDC. Addressing emerging infectious disease threats to health: a prevention strategy for the United States. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, 1994. 3. Paul SM, Finelli L, Crance GL, Spitalny KC. A statewide surveillance system for antimicrobial resistant bacteria--New Jersey. Infect Control Hosp Epidemiol 1995;16 (in press). 4. Paul SM, Silber JL, Crane G, Kupersmit A, Spitalny K. Vancomycin-resistant enterococcal (VRE) blood isolates in New Jersey (NJ) hospitals: an 18 month study. In: Proceedings of the fourth annual meeting of the Society for Hospital Epidemiology of America. West Deptford, New Jersey: Society for Hospital Epidemiology of America, 1994. 5. Paul SM, Noveck H, Silber JL, Wartenberg D, Crane G, Spitalny K. A statewide study of patient risk factors for vancomycin-resistant enterococcal bacteremia. In: Proceedings of the fourth annual meeting of the Society for Hospital Epidemiology of America. West Deptford, New Jersey: Society for Hospital Epidemiology of America, 1994. 6. Silber JL, Patel M, Paul SM, Kostman JR. Statewide surveillance of isolates of vancomycin-resistant gram-positive cocci: genotyping of vancomycin resistance and activity of Quinupristin/Dalfopristin (RP59500) and other antimicrobials. In: Proceedings of the 34th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy. Washington, DC: American Society for Microbiology, 1994. 7. Cronan J, Silber J, Schwarz G, Paul SM. Infection control practices and the prevalence of vancomycin-resistant enterococci (VRE) in New Jersey hospitals. In: Proceedings of the 34th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy. Washington, DC: American Society for Microbiology, 1994. ------------------------------ End of HICNet Medical News Digest V08 Issue #26 *********************************************** --- Editor, HICNet Medical Newsletter Internet: david@stat.com FAX: +1 (602) 451-6135