High prevalence of extended-spectrum -lactamase production in Enterobacter spp. bloodculture isolates in the Netherlands

Abstract number: P656

Cohen Stuart J., Al Naiemi N., Fluit A., Arents N., Diederen B.M., Thijsen S., Vlaminckx B., Mouton J., Leverstein-van Hall M.

Objective: In 2008 a guideline of the Dutch Society for Medical Microbiology for screening and confirmation of ESBLs in Enterobacteriaceae was issued. An optional recommendation in the guideline was to screen Enterobacter spp. for ESBLs (i.e. MIC > 1 mg/L for cefotaxime and/or ceftazidime) and to perform a confirmation test with cefepime ± clavulanic acid. Dutch microbiologists questioned this recommendation because no data were available indicating that Enterobacter spp. might be an important source for ESBLs.

The aim of this study was to determine the prevalence of ESBLs in Enterobacter spp. causing invasive infections and to obtain their susceptibility patterns.

Methods:Enterobacter cloacae and Enterobacter Aerogenes bloodculture isolates obtained in 2006 and 2007 in 12 hospitals throughout The Netherlands were collected (one isolate per patient). Susceptibly testing for 22 antimicrobial agents using broth microdilution (18) or Etest (4) was performed on all isolates as well as the ESBL confirmation Etest with cefepime/cefepime + clavulanic acid. EUCAST breakpoints were used.

Results: 272 isolates were obtained (83.5%E. cloacae). Of the total collection of 272 isolates 41.5% (113) was positive in the screentest of which 30% was positive in the confirmation test, reflecting an ESBL prevalence of 12.9% (35/272), ranging from 0% to 33% per hospital. E. cloacae isolates were ESBL positive in 14.5% and E. Aerogenes in 4.4%. The confirmation test was indeterminate in 2.9% (8/272) of the isolates. Molecular analysis of ESBL genes is pending.

Susceptibilty rates in ESBL positive versus ESBL negative isolates were as follows: for meropenem 97% vs 97%, respectively; for imipenem 91% vs 95% (NS); for ertapenem 43% vs 86% (p < 0.001); for cotrimoxazole 43% vs 93% (p < 0.001); for ciprofloxacin 20% vs 91% (p < 0.001); for tobramycin 20% vs 95% (p < 0.001); for amikacin 77% vs 97% (p < 0.001); for tigecyclin 40% vs 28% (NS) and for colistin 69% vs 69% (NS).

Conclusions: The prevalence of ESBL in Enterobacter spp. bloodculture isolates was 12.9%, showing that Enterobacter spp. are an important reservoir for ESBLs in the nosocomial setting. For optimal infection control, detection of ESBLs in Enterobacter spp. should be common practice in clinical microbiology laboratories. Phenotypic ESBL production in Enterobacter spp. is associated with increased resistance to ertapenem, ciprofloxacin, tobramycin, amikacin and cotrimoxazole.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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