Frequency and diversity of Class A extended-spectrum beta-lactamases in hospitals of the Auvergne, France: a 2 year prospective study.

Objectives: To evaluate the frequency and diversity of extended-spectrum beta-lactamases (ESBLs) produced by Enterobacteriaceae and Pseudomonas aeruginosa in one French region.

Methods: During 2001-2002, all the non-duplicate isolates of P. aeruginosa resistant to ceftazidime and of Enterobacteriaceae intermediate or resistant to ceftazidime and/or cefotaxime and/or aminoglycosides with an AAC(6') I phenotype were collected in nine hospitals of the area. ESBL isoelectric points were determined, bla genes were amplified and sequenced and epidemic isolates were genotyped with ERIC2-PCR.

Results: ESBLs were observed in 297 Enterobacteriaceae (0.8%). The most frequent were TEM-3 like (n=152; 51.2%) and TEM-24 (n=115; 38.7%). Four new enzymes were observed, TEM-112 (pI 5.4), TEM-113 (pI 6.3), TEM-114 (pI 5.9) and TEM-126 (pI 5.4). Other TEMs were TEM-8, TEM-12, TEM-16, TEM-19, TEM-20, TEM-21, TEM-29 and TEM-71. The other ESBLs were SHV-4, SHV-5 and SHV-12, CTX-M-1, CTX-M-3, CTX-M-14 and CTX-M-15. In 37 P. aeruginosa (0.7%) only one ESBL was observed, PER-1. Five epidemic strains were detected, Serratia marcescens TEM-3 and four observed in several hospitals, Enterobacter aerogenes TEM-24, Citrobacter koseri TEM-3, Proteus mirabilis TEM-3 and P. aeruginosa PER-1.

Conclusion: ESBL frequency was lower than in 1998, and CTX-M-type frequency higher (2.1% of ESBLs in 2001, 4.9% in 2002). This long-term survey detected new sporadic enzymes (TEM-112, TEM-113, TEM-114 and TEM-126) and interhospital epidemic strains while avoiding any overestimation of ESBL frequency that may otherwise have occurred because of acute epidemics.