Minnesota Department of Health (MDH) Bug Bytes
January 22, 2001
Vol. 2: No. 2
1. College Student Dies from Community-Acquired MRSA
Two weeks ago, a 21-year-old college student died from necrotizing pneumonia and disseminated intravascular coagulation that was caused by community-acquired methicillin-resistant Staphylococcus aureus (MRSA). He had been previously healthy and had no recent hospitalizations or medical procedures. MRSA strains first appeared in the United States in the early 1960s. Since then an increasing number and percentage of nosocomial S. aureus infections have been methicillin resistant. However, until recently MRSA infections were confined to patients with well-defined risk factors, such as recent hospitalization, surgery, residence in nursing homes, or dialysis. Nosocomial MRSA strains have rarely "spread" into healthy members of the general population. For example, healthcare workers - who take care of many MRSA patients and who can transmit MRSA from patient to patient via their hands - are not themselves at increased risk for MRSA infections. In the past five years, Minnesota and several surrounding midwestern states have started to see MRSA infections in healthy individuals, particularly children, with no known MRSA risk factors. This has led to a handful of well-publicized deaths over the past four years and hundreds of other infections, some of which were of a very serious nature. Are these "escaped" hospital strains? We don't think so, based on genetic fingerprinting and antimicrobial susceptibility results, but we are still addressing this question. Physicians in Minnesota should be aware of this emerging problem. In particular, MRSA infection should be considered in children who present with life-threatening infections (especially pneumonia or sepsis) or in children or young adults with recurrent boils/abscesses that have not responded to antibiotics. Physicians should have a low threshold to obtain cultures from infected sites, especially when those infections might be staphylococcal in origin. Physicians should be aware that all MRSA strains are intrinsically resistant to all penicillins and cephalosporins, which are among the most common antibiotics prescribed for outpatients and inpatients. Fortunately, the vast majority of community MRSA strains are susceptible to trimethoprim-sulfamethoxazole, clindamycin, and quinolones so treatment with vancomycin should not be routinely required. Serious (i.e. sterile site or fatal) community-acquired MRSA infections (defined as infections in those patients without traditional MRSA risk factors mentioned above) have been reportable in Minnesota since 1999. In addition, 13 hospital laboratories have kindly agreed to report all MRSA infections to us so we can compare community-acquired MRSA cases with traditional nosocomial cases. We thank the ever-alert infectious disease clinician who reported this case and the hospital laboratory that promptly sent the isolate for typing and toxin testing. For questions about community-acquired MRSA contact (612) 676-5414.
2. Foodborne Illness Outbreak An outbreak of foodborne illness associated with a restaurant in Blaine recently hit the news. Testing of stool specimens from ill patrons by MDH revealed that the culprit was Norwalk-like virus (NLV) (named after an outbreak of gastroenteritis that occurred in Norwalk, OH in 1972), also known as calicivirus. This virus causes diarrhea and vomiting with an incubation period of 12 to 48 hours and a duration of 24 to 60 hours. Outbreaks are often caused by person-to-person transmission of NLV in settings such as nursing homes and by foodborne transmission, commonly traced back to ill food handlers (as appeared to occur in this situation). From 1981-1999, 144 (43%) of 335 confirmed outbreaks of foodborne disease in Minnesota were due to NLV, compared to 67 (20%) caused by the major bacterial foodborne pathogens (Salmonella, Campylobacter, E. coli O157:H7, Shigella, and Listeria). Therefore, over this 19-year period the combined number of foodborne outbreaks due to NLV was more than twice the number of foodborne outbreaks due to bacterial agents. Since 1996, the MDH laboratory has routinely used reverse transcription-polymerase chain reaction (RT-PCR) to detect NLV in stool specimens from outbreaks with epidemiologic features of NLV gastroenteritis. Gene sequencing of isolates has been used to link apparently unrelated outbreaks and to better understand the transmission of this virus in the community. If you identify a possible outbreak of compatible illness, please contact the Acute Disease Epidemiology Section at (612) 676-5414 to arrange for testing of specimens.
3. PFGE Subtyping of Salmonella Typhimurium
In last week's New England Journal of Medicine (2001; 344:189-95) was an article from our group; the lead author was Dr. Jeff Bender (who is now at the University of Minnesota, although we don't hold that against him). It demonstrated that routine PFGE molecular subtyping of Salmonella Typhimurium isolates at MDH was a useful public health tool; 10 of 16 outbreaks in due to S. Typhimurium in Minnesota between 1994 to 1998 were identified this way. Routine subtyping allowed us to identify outbreaks that would have gone undetected as well as to confirm outbreaks that would have been detected by traditional means since we could identify cases as being outbreak-associated or unrelated sporadic cases. In one of these outbreaks, our detection lead to a recall of a contaminated commercial product. Once again, this demonstrates the value of a robust surveillance system which includes timely reporting by clinicians, isolate submission by laboratories, and routine molecular subtyping and patient interviewing at MDH. When public health actions were taken (i.e. product recall, restrictions on licensed food facilities), further morbidity was undoubtedly averted.
4. Emerging Infections Program (EIP) Update
We have just received notice that our Emerging Infections Program has received renewal funding of $2.3 million from the Centers for Disease Control and Prevention. Minnesota is one of 9 sites across the U.S. that serves as a sentinel and a place to conduct population-based studies for emerging infections. Two new studies being started this year are an efficacy study of the newly licensed pediatric pneumococcal vaccine and a study of culture-negative bacterial meningitis. We've said it before, but the success of EIP is the result of all of the work you do with us.
Bug Bytes is a combined effort of the Infectious Disease Epidemiology, Prevention and Control Division and the Public Health Laboratory Division of MDH. We provide Bug Bytes as a way to say THANK YOU to the infection control professionals, laboratorians, local public health professionals, and health care providers who assist us.
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