Coexistence of SHV-4-and TEM-24-producing Enterobacter aerogenes strains before a large outbreak of TEM-24-producing strains in a French hospital

In 1996, a monitoring program was initiated at the teaching hospital of Ami ens, France, and carried out for 3 years. All extended-spectrum beta -lacta mase (ESBL)-producing Enterobacter aerogenes isolates recovered from clinic al specimens were collected for investigation of their epidemiological rela tedness by pulsed-field gel electrophoresis and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and determination of the type of ESBL h arbored by isoelectric focusing and DNA sequencing. Molecular typing reveal ed the endemic coexistence, during the first 2 years, of two clones express ing, respectively, SHV-4 and TEM-24 ESBLs, while an outbreak of the TEM-24- producing strain raged in the hospital during the third year, causing the i nfection or colonization of 165 patients. Furthermore, this strain was iden tified as the prevalent clone responsible for outbreaks in many French hosp itals since 1996, This study shows that TEM-24-producing E. aerogenes is an epidemic clone that is well established in the hospital's ecology and able to spread throughout wards, The management of the outbreak at the teaching hospital of Amiens, which included the reinforcement of infection control measures, failed to obtain complete eradication of the clone, which has bec ome an endemic pathogen.