Occurrence of AmpC chromosomally b-lactamase ACT-1 and extended spectrum b-lactamases type TEM, SHV and CTX-M in clinical isolates of Enterobacter cloacae

Abstract number: 1733_89

Biendo M., Manoliu C., Canarelli B., Thomas D., Hamdad-Daoudi F., Rousseau F., Laurans G., Eb F.

Objectives: The primary purpose of this investigation was, (i) to study the main drug-resistant mechanism, (ii) to determine the genetic relatedness of strains recovered from different separated sites using pulsed-field gel electrophoresis (PFGE) and, (iii) to describe the molecular epidemiology of the outbreaks.

Methods and Results: We tested 70 consecutive nosocomial E. cloacae isolates recovered from patients admitted in Amiens University Hospital (61 patients), Abbeville General Hospital Center (7 patients), and Iasi Pediatric University Hospital [(Romania) (2 patients)]. Based on phenotypic methods, 100% of isolates produced AmpC b-lactamases, 90% produced ESBLs and 10% were ESBL-nonproducers. 100% of AmpC producers carried AmpD enzyme and blaACT-1 while 7.2% harboured blaFOX-5. PCR amplified, 395 pb and 1,1184 pb segments respectively corresponding to b-lactamases with a pI of 9.0 (ACT-1), and 7.5 (FOX-5) respectively according to IEF and sequencing results. 90% of ESBL-producers carried bla TEM-24, bla SHV-4, blaCTX-M-1 and bla CTX-M-9. PCR amplified 972 pb, 785 pb, and 900 pb segments respectively corresponding to b-lactamases with a pI of 6.5 (TEM-24), 7.8 (SHV-4), 8.4 (CTX-M-1) and 8.0 (CTX-M-9). The 7 ESBL-nonproducers harboured blaTEM-1 and blaSHV-1 encoding b-lactamases with a pI of 5.4 (TEM-1) and 7.6 (SHV-1). Four isolates for which the minimum inhibitory concentrations (MICs) of cefoxitin (FOX), cefotaxime (CTX), ceftazidime (CAZ) and aztreonam (ATM) were of >256 ug/mL and those of imipenem (IPM) were between 12–48 ug/mL showed a diminished level or no expression of a 37- and 38 kDa outer membrane proteins.

Conclusion: It is concluded that the high level of resistance to FOX, CTX, CAZ and ATM and the increase of the MICs of IPM for AmpC b-lactamase- and the ESBL-producing E. cloacae isolates studied are associated with porin deficiency. PFGE analysis showed that these isolates exhibited high genetic diversity (39 different pulsotypes). There was great phenotypic heterogeneity (5 different biotypes), 6 b-lactam R-patterns, and 3 aminoglycosides R-patterns.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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