Multi-drug resistance induced by β-1actamases and class Ⅰ integrons with deficiency of Omp genes in Enterobacter cloacae

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WANG Feng-xia(Clinical Laboratory, Tianjin Medical University General Hospital, Tianjin 300052, China)
HU Zhi-dong(Clinical Laboratory, Tianjin Medical University General Hospital, Tianjin 300052, China)
HU Qiao-juan(Clinical Laboratory, Tianjin Medical University General Hospital, Tianjin 300052, China)
TIAN Bin(Clinical Laboratory, Tianjin Medical University General Hospital, Tianjin 300052, China)
YANG Hua(Clinical Laboratory, Tianjin Medical University General Hospital, Tianjin 300052, China)
LI Jing(Clinical Laboratory, Tianjin Medical University General Hospital, Tianjin 300052, China)
Journal Title:
Chinese Journal of Clinical Infectious Diseases
Volume 04, Issue 06, 2011
Key Word:
Integrons;AmpC β-1actamase;β-1actamase;Polymerase chain reaction;Bacterial outer membrane proteins

Abstract: Objective To investigate the drug resistance and its distribution induced by β-lactamases and class Ⅰ integrons with the deficiency of Omp genes in Enterobacter cloacaes.Methods Totally 112 strains of Enterobacter cloacaes were isolated during January 2008 and May 2011.The identification of strains was performed by using Vitek-2 Compact automatic system; and antibiotic susceptibility was determined by K-B method.Isolates of E.cloacae were screened for carbapenemases by modified Hodge test,improved three dimensional test and EDTA-meropenem synergy test.Genes encoding AmpC β-lactamase,metallo-β-1actamases (MBLs) and OXA-like β-1actamases were screened by multiple PCR.Single PCR was used to detect ISEcpl,OmpK35/36,NDM-1 and OXA-48.The variable regions of class Ⅰ integrons were amplified and sequenced.Results Among 112 isolates,6 (5.4%) demonstrated positive in the modified Hodge test and 14 ( 12.5% ) were positive in the improved three-dimensional test.No carbapenemases gene was found.There were 29(25.9% ) strains positive for ESBLs genes,ISEcpl was found in the upstream of all the CTX-M-type ESBLs; OXA-1 ESBLs were detected in 2 isolates.AmpC β-lactamase genes were positive in 45 (40.2%) strains,and 82.2% (37/45) were MIR-3 type.Twenty two isolates carried class Ⅰ integrons,and four different cassettes arrangements were identified within 16 strains:9 isolates harbored aadB-aadA2 ( 1 000 bp),5 isolates with dfrAl5 (700 bp),2 isolates with aadAl ( 1 000 bp).One isolate harbored all the above gene cassettes.The deficiency of OmpK35/36 was found in all strains.Conclusion ESBL,AmpC β-lactamase and the deficiency of OmpK35/36 are correlated with the resistance to carbapenems in Enteobacter clocace,and class Ⅰ integrons may also partly account for the multidrug-resistance.

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