Genetic aspects of Ambler class C, extended spectrum and metallo-beta-lactamases among beta-lactam resistant Escherichia coli and Klebsiellae pneumonia
Al- Anbar Medical Journal,
2005, Volume 5, Issue 1, Pages 40-47
AbstractObjective : To detect the role of Ambler class C(AmpC), Extended Spectrum (ESBL) and metallo-B-lactamases in the resistance of Escherichia coli and Klebsiellae pneumonia to P-lactams and whether the genetic expression of these enzymes are encoded by conjugative plasmids DNA or chromosomal DNA .Method : The National Committee for Clinical Laboratory standard AmpC and ESBLs screening and phenotypic confirmatory tests were performed for 25 isolates of Escherichia coli and 18 isolates of Klebsiellae pneumonia . Plasmid profile analysis and curing experiments were performed . Plasmid DNA recombination for resistant genes was carried out by conjugation . Results : Initially, 17(68.0%), 11(61.1%) isolates off coli and K pneumonia respectively demonstrated a clavulanic acid (CA) effect by double disk synergy and 15(60.0%), 10(55.6%) isolates of Escherichia coli and Klebsiellae pneumonia respectively demonstrated a CA effect by broth microdilution technique . The genes encoding for ESBL in 13 (86.7%), 9(90.0%) isolates of ESBL producing Escherichia coli and Klebsiellae pneumonia respectively were carried by conjugative plasmids while this genetic elements were encoded for 3(30.0%), 3(37.5%) of AmpC plasmids isolates of Escherichia coli and Klebsiellae pneumonia respectively . Further, the resistant genes encoding for metallo-p-lactamase in one isolate of Escherichia coli was carried by conjugative plasmid.
Conclusions: The study concluded that ESBLs and AmpC cephalosporinases play an essential role in the resistance of Escherichia coli and Klebsiellae pneumonia to P-lactams and in the lesser extent metallo-p-lactamase. Further, isolation of plasmid DNA revealed that most of the isolates examined harbored more than one plasmid Furthermore, conjugative plasmids were found to be the main genetic elements encoding for ESBLs produced by Escherichia coli followed by Klebsiellae pneumonia and the lesser extent to AmpC producing strains of the same bacteria respectively while the B-lactamases production for the remaining isolates is suggested to be under non-conjugative plasmids or chromosomal control .
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