Occurrence of CTX-M-I Type β-lactamases Gene in Certain Gram Negative Bacteria
Iraqi Postgraduate Medical Journal,
2013, Volume 12, Issue 2, Pages 306-311
The CTX-M-type β-lactamases represent a group with a typical extended-spectrum β-lactamase
(ESBL)-resistance phenotype. These enzymes, encoded by transferable plasmids. They have a
preferential hydrolysis of Cefotaxime over Ceftazidime. The CTX-M-type β-lactamases have been
described in species of Enterobacteriaceae and Pseudomonas aeruginosa.
This study was designed to investigate of the occurrence of CTX-M-I type in some Gram negative
bacteria species isolated from clinical cases of in Iraq.
A group of Gram negative bacteria were isolated from different sources.Plasmid DNA extraction,
and electrophoresis were performed. Using specific primers, CTX-M-I enzyme genes were
amplified by PCR.
Plasmid profile of the tested isolates reveals the presence of relatively large plasmids, their Wight
was more than 10 kb some isolates posses’ 3-4 kb plasmids. The results of PCR amplification
showed the presence of CTX-I genes. All isolates of Salmonella enterica serovar Typhimurium
(100%) are negative for CTX-M-I gene as well as most of P. aeruginosa isolates (86.7%). In
contrast, all of E. coli (100%) and most of Proteus Spp isolates were positive for CTX-M-I gene.
CTX-M genes are predominant in E.coli followed by Proteus Spp. while Salmonella enterica
serovar Typhimurium and P. aeruginosa isolates showed low incidence of blaCTX-M genes
occurrence. The alarming situation with dissemination of CTX-M producing isolates highlights the
need for their epidemiological monitoring and prudent use of antimicrobial agents
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