Extended-spectrum β-lactamase-producing Serratia marcescens outbreak in a Bulgarian hospital

We describe a nosocomial outbreak of extended-spectrum β-lactamase (ESBL)-producing Serratia marcescens in a Bulgarian university hospital affecting nine patients on four wards. Phenotypic and genotypic (plasmid profile, randomly amplified polymorphic DNA analysis and amplified ribosomal DNA restriction analysis) analysis of the isolates indicated a single clone. The epidemic strain was resistant to oxyimino β-lactams, aztreonam, aminoglycosides, tetracycline and chloramphenicol. It produced CTX-M-3 ESBL as demonstrated by isoelectric focusing, CTX-M PCR-RFLP and gene sequencing. The isolate was also found in the environment and from a nurse's hands, suggesting transmission by staff handling. The outbreak was controlled by patient isolation and intensified hand washing. This is the first report from Bulgaria describing a hospital outbreak caused by CTX-M-3 ESBL-producing S. marcescens.