In vitro activity of temocillin against extended spectrum beta-lactamase-producing Escherichia coli

Temocillin is a semi-synthetic 6-alpha-methoxy derivative of ticarcillin. It is highly stable to most bacterial beta-lactamases. However, data concerning its activity against extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae are limited. We have analysed the in vitro activity of temocillin against clinical isolates of ESBL-producing Escherichia coli over the past 4 years in a university hospital in Brussels, Belgium.

Strains were screened for ESBL production using the double-disc synergy test. The MIC of 12 antimicrobial agents was determined for ESBL-producing E. coli isolates (n = 162) using the agar dilution method. ESBLs were characterized by isoelectric focusing; multiplex PCR for bla genes of the SHV, TEM and CTX-M families; and DNA sequencing.

ESBL-producing E. coli isolates harboured CTX-M+TEM (35%), TEM alone (44%), CTX-M alone (6%), CTX-M+SHV (2%) and other ESBL combinations (10%). The proportion of temocillin-susceptible isolates was 92%, with MIC(50) and MIC(90) values of 8 and 32 mg/L, respectively. Co-resistance to ciprofloxacin and co-trimoxazole in ESBL-producing E. coli was frequent (39%). The proportion of isolates not susceptible to aminoglycosides was 55, 37 and 4% for tobramycin, gentamicin and amikacin, respectively. The proportion of isolates not susceptible to ceftazidime, cefotaxime, cefepime and piperacillin/tazobactam was 70, 52, 37 and 11%, respectively. No resistance to meropenem was observed. The proportion of strains exhibiting resistance to temocillin by year was stable over the study period.

These data indicate good in vitro activity of temocillin against multiresistant ESBL-producing E. coli. Prospective clinical studies are necessary to examine temocillin's potential role in the treatment of non-complicated infections caused by ESBL-producing E. coli.