Multidrug-resistant and difficult-to-treat Acinetobacter baumannii may be responsible for nosocomial infections. The production of carbapenem-hydrolyzing class D b-lactamases (CHDLs) and extendedspectrum b-lactamase (ESBLs) of the GES type possessing a carbapenemase activity has been increasingly reported worldwide in A. baumannii. The aim of this study was to analyze the resistance mechanisms of two carbapenem resistant A. baumannii clinical isolates recovered in a neonatology center in the center-east of Tunisia.Two carbapenem resistant A. baumannii isolates were recovered. The first isolate co-harbored the bla GES-11 ESBL gene and the bla OxA-23 CHDL gene. Analyses of the genetic location indicated that the bla GES-11 gene was plasmid located (Gr6). However, the bla OxA-23 gene was located on the chromosome. The second strain had only the bla OxA-23 CHDL gene, which was plasmid located.This study showed the first description of the GES-type b-lactamase in A. baumannii in Tunisia.
Extended-spectrum beta-lactamases (ESBLs) in Pseudomonas aeruginosa are increasingly reported worldwide. In our study, a total of 70 clinical isolates of multidrug-resistant P. aeruginosa were studied. Isoelectric focusing electrophoresis, PCR, and PCR product sequencing were designed to characterize the contained ESBLs. The Double Disk Synergy Test in Cloxacillin (250 microg/ml)-containing Mueller-Hinton agar plates with a 20 mm distance between disks was the most reliable ESBL-screening method. Seven out of 70 multidrug-resistant P. aeruginosa clinical isolates were positive for ESBL and have the bla(SHV-2a) ESBL gene. The bla(SHV-2a)-positive isolates were clonally related according to Enterobacterial Repetetive Intergenic Consensus-PCR (ERIC-PCR) results. The bla(SHV-2a) gene was found to be chromosomally located, and the flanking IS26 sequence in the immediate upstream region of the bla(SHV-2a) gene was detected in all SHV-2a-producing isolates. This is the first report of SHV-2a-producing P. aeruginosa isolates from Tunisia.
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