Occurrence and detection of ampc b-lactamases among enterobacteriaceae isolates from patients at Ain Shams University Hospital

Abstract EN

AmpC b-lactamases are often plasmid mediated that hydrolyze all b-lactam antibiotics except cefepime and carbapenems.

Aim of the study: We aimed to evaluate the presence of AmpC b-lactamase among Enterobacteriaceae isolates separated from patients with nosocomial infections, and to detect the genetic basis for AmpC production in these strains.

Subjects and methods: 50 AmpC b-lactamase Enterobacteriaceae were analyzed for the presence of AmpC production.

Three phenotypic AmpC confirmation assays (AmpC E test, the disk approximation test, Amp C EDTA disc) were able to detect the majority of AmpC-positive strains correctly.

Molecular detection of plasmid mediated AmpC by multiplex PCR was conducted on them.

Results: The results show that from the 148 total isolates obtained from ICU admitted patients with suspected nosocomial infections, 50 (33.8%) were AmpC b-lactamase isolates.

For the 50 AmpC isolates, all phenotypic Amp C tests gave a positive result.

Among these isolates, plasmid encoded AmpC genes were detected by multiplex PCR in 46 (92%) isolates, which included Klebsiella pneumoniae (n=22) (47.8%), Escherichia coli (n=15) (32.6%), and Proteus mirabilis (n= 9) (19.6%).

One E.

coli, one K.

pneumoniae, and two P.

mirabilis isolates showed no AmpC gene.

The most prevalent AmpC gene was that belonging to family CMY-1 which was detected in 73.9% (34/46) of all isolates.

Conclusion: It could be concluded that: Amp C producing isolates among Enterobacteriaceae strains have been increasingly recognized in the Ain Shams University Hospital.

Thus, molecular identification of the genes encoding AmpC would be essential for a reliable epidemiological investigation of their transmission in hospitals.