Society for Healthcare Epidemiology of America Meeting Coverage
The following is an overview of some presentations at the annual meeting of the Society for Healthcare Epidemiology of America. — Robert Muder, MDE faecium
At the Montefiore Medical Center in New York City, the prevalence of Quinupristin/Dalfopristin (Q/D)-resistant E faecium isolates increased from 8.3% in 2000 to 18.4% in 2001. Fifty-seven percent of Q/D resistant isolates were resistant to Q/D alone; 25% of these appeared to be community acquired. There was poor correlation between usage rates of Q/D, clindamycin and macrolides, and the rate of Q/D resistance. Only 16% of patients appeared to have acquired Q/D resistance during Q/D therapy (Daoura NJ. Investigation of the determinants of quinupristin-dalfopristin resistance among Enterococcus faecium isolates at a single medical center in NYC. [Abstract 55]).
This report raises the possibility of the widespread occurrence of Q/D resistance in E faecium independent of antimicrobial usage. The clinical implication is that Q/D susceptibility should not be assumed, and appropriate antimicrobial susceptibility testing should be performed when using Q/D to treat E faecium infection.Sepsis Due to Contaminated Endoscopes
Two patients became bacteremic with a cefotaxime-resistant E coli after undergoing endoscopic retrograde cholangiopancreatography (ERCP). Because cefotaxime resistance was rare in the facility, Arends and colleagues undertook an investigation. Both patients underwent the procedure with the same ERCP-duodenoscope. The surveillance cultures taken after the endoscope left the automated disinfector were negative; however, a subsequent culture taken by reverse flushing of the fluid through the endoscope grew cefotaxime-resistant E coli. The clinical and endoscope isolates were identical by PFGE. Cultures obtained by reverse flushing of additional endoscopes yielded other pathogens, including Staphylococcus aureus, Enterobacter cloacae, E faecalis, and Candida parapsilosis (Arends JP, et al. Sepsis with a cefotaxime-resistant E coli related to a contaminated endoscope: Failure of routine cultures to detect the problem [Abstract 76]).
Three patients developed infection due to multidrug-resistant P aeruginosa following ERCP. The same endoscope had been used on all 3. Although cultures of the endoscope were negative, all 3 clinical isolates were identical by PFGE. No additional cases occurred after the implicated device was removed from service (Fraser TG, et al. An outbreak of multidrug-resistant Pseudomonas aeruginosa after ERCP: Successful control due to rapid assistance from the molecular epidemiology lab. [Abstract 77]).
Cholangitis and bacteremia are known complications of ERCP. An isolated case of Gram-negative biliary infection after ERCP would typically not point to an infection control issue. In each of these 2 outbreaks, the endoscope was suspected due to the occurrence of multiple cases of infection with organisms with unusual antimicrobial susceptibility patterns. In neither outbreak could the investigators identify any break in technique or malfunction of the endoscope or disinfecting equipment. These outbreaks point to the difficulty in adequately disinfecting endoscopes used for ERCP. The occurrence of multiple cases of infection in patients undergoing ERCP warrants a microbiologic and epidemiologic investigation to determine if contaminated endoscopes are the source.MRSA
Although S aureus has been cited as a cause of antibiotic-associated diarrhea (AAD), it is seldom recognized by clinicians. Boyce and colleagues investigated the possible role of MRSA in causing AAD. They defined a case of MRSA-ADD as a patient with 1 or more stool specimens with heavy growth or MRSA, few if any normal flora, no growth of enteric pathogens, and 1 or more negative assays for Clostridium difficile toxin. They identified 13 case patients; all had received previous antimicrobials, and 92% had received fluoroquinolones. Patients experienced 4-11 loose stools daily. Eleven of the cases had more than 1 negative assay for C difficile toxin (range, 2-7). Quantitative stool cultures from 2 patients yielded > 108 colony-forming units per gram of stool. Nine of the 13 MRSA isolates were identical by pulse-field gel electrophoresis; all of the 9 produced staphylococcal enterotoxins A and/or B. Of the remaining 4 isolates, 1 produced enterotoxin D, and the rest were enterotoxin negative (Boyce JM, et al. Nosocomial antibiotic-associated diarrhea caused by methicillin-resistant Staphylococcus aureus [Abstract 270]).
While not proving causation, this study suggests that enterotoxin-producing MRSA may be a relatively common cause of C difficile-negative ADD. Clearly, more clinical and epidemiologic investigation into the possible role of MRSA in causing ADD is warranted.
Dr. Muder is Hospital Epidemiologist Pittsburgh VA Medical Center Pittsburgh Section Editor, Hospital Epidemiology.