An MRSA outbreak (I:E clone) in a University Hospital Burn Center

The Burn Center at New York Hospital is a 46 bed unit with over 1200 admissions annually. During an 18 month period from January 1995 to July 19%, 109 single patient MRSA isolates were identified and 104 isolates (95%) were available for DNA fingerprinting. 99 isolates (95%) had the mec A:Tn 554 genotype of I:E. Pulsed-field electrophoresis (PFGE) identified 8 patterns of which 59 isolates (60%) were 1a. Antibiograms revealed that the I:E clonal type had a stable multidrug resistant phenotype with 100% concordance (sensitive only to TMP/SMX and vancomycin). The specimen sources of I:E isolates were sputum 49%, blood 23%, wound 16%, urine 7% and intravascular catheter tip 5%. 54% of these patients had smoke inhalation injury; 51/53 required intubation or tracheostomy. 43 isolates (43%) were considered invasive (positive blood culture). 81% of patients received vancomycin and the mortality was 28%. PFGE pattern la was the predominant pattern during the first 10 months of the outbreak (52/58-90%). Overall when pattern la was compared to other PFGE patterns, no differences in various clinical parameters were observed. Despite infection control measures, the I:E clone continued to be recovered during the 18 months of study. This outbreak is the first report of the Iberian MRSA clone I:E in the United States. In the clinical setting of burn patients, this clone may be difficult to eradicate and can be associated with bacteremia and a significant mortality.