PREVALENCE AND CHARACTERIZATION OF EXTENDEDSPECTRUM β-LACTAMASE- PRODUCING ENTEROBACTERIACEAE ISOLATED FROM HOSPITAL ENVIRONMENTSDEBABZA MANEL, MECHAI ABDELBASSET, AND CHETTIBI HOURIAAbstract Bacteria producing extended-spectrum β-lactamase (ESBL) among clinical isolates have been reported in many countries. However, data concerning the role of environmental contamination in the dissemination of (ESBL)-producing Enterobacteriaceae are currently lacking. In this context, the aim of this study was to investigate and characterise Enterobacteriaceae strains isolated from different places in a hospital and to determine the occurrence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae. The bacterial isolates were identified on the basis of standard cultural, morphological and biochemical characteristics. Antibiotic susceptibility of the isolates was tested by disk diffusion method. A total of 637 strains of Enterobacteriaceae were isolated between 2007-2012. Susceptibility study showed that the imipenem was the most active antibiotic against overall enterobacteria with resistance rate of 2.51%, however the high resistance rates were observed to ampicilin (98.11%) and cephalixin (78.65%). The prevalence of ESBL was 136 (21.35%) and ESBL-producing strains were K. pneumoniae 66 (28.45 %), E. coli 31 (25.41%), S. marcescens 18 (19.15%), K. oxytoca 9 (17.31%), En .cloacae 5 (5.43%), C. freundii 04 (16%) and P. mirabilis 03 (15%). ESBL production was confirmed by double disk screening, combination disk method and E-test ESBL strip. All selected isolates harbored from one to four different plasmids with molecular sizes ranging from 5-170 kb. In general, most transconjugants acquired ceftazidime resistance by an ESBL gene encoded on the largest plasmid (>125 kb) found in the respective isolate. In addition, these transconjugants co-expressed other antibiotic resistance markers such as amikacin and ciprofloxacin.
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