Molecular epidemiology of an outbreak due to extended-spectrum beta-lactamase-producing enterobacteria in a French hospital

Between June 1992 and June 1993, 128 extended-spectrum beta-lactamase-producing enterobacteria (123 Klebsiella pneumoniae, 3 Escherichia coli, 1 Enterobacter aerogenes, and 1 Citrobacter diversus) were collected in a French university hospital. These isolates were recovered mainly from patients hospitalized in intensive care and neurosurgery units. The 128 strains were divided into 14 antibiotypes (ATBs; ATB1 to ATB14); 102 of 103 nonredundant isolates were shown to produce an SHV-4-related extended-spectrum beta-lactamase (pI 7.8, hybridization with a bla(SHV) probe); the remaining strain (Kp 2108) produced a TEM-3-related extended-spectrum beta-lactamase (pI 6.3, hybridization with a bla(TEM) probe). For representative isolates, five plasmid profiles (PI to PII-4), eight ribotypes (E1 to E8), and seven arbitrarily primed polymerase chain reaction profiles (A1 to A7) were obtained. The results suggest the spread of an epidemic strain of Klebsiella pneumoniae (E1, A1, PI, various ATBs) from an intensive care unit throughout the hospital. Another epidemic strain (E2, A2, PI, ATB4) was confined to the neurosurgery unit. Other extended-spectrum beta-lactamase-producing Klebsiella pneumoniae of ribotypes distinct from E1 or E2 might result from the spread of an epidemic plasmid, such as reported for isolates of other enterobacterial species. Conversely, they might represent imported cases, such as the strain Kp 2108, which produced a TEM-3-related beta-lactamase.