Evaluation of phenotypic tests for the detection of AmpC beta-lactamase in clinical isolates of Escherichia coli.
BACKGROUND
AmpC beta lactamases are cephalosporinases that confer resistance to a wide range of beta lactam drugs thereby causing serious therapeautic problem. As there are no CLSI guidelines for detection of AmpC mediated resistance in Gram negative clinical isolates and it may pose a problem due to misleading results, especially so in phenotypic tests. Although cefoxitin resistance is used as a screening test, it does not reliably indicate AmpC production.


METHODS
We planned a study to determine the occurrence of AmpC beta lactamase in hospital and community, clinical isolates of Escherichia coli and simultaneously evaluate different phenotypic methods for detection of AmpC beta lactamases.


RESULTS
It was observed that 82.76% isolates were ESBL positive and 59% were cefoxitin screen positive. Using phenotypic confirmatory tests the occurrence of Amp C beta lactamases was found to be 40% and 39% by inhibitor based method using boronic acid (IBM) and modified three dimensional test (M3D) respectively.


CONCLUSIONS
Both the test showed concordant result. Co-production was observed in 84.62% isolates Screening of ESBL and Amp C can be done in routine clinical microbiology laboratory using aztreonam and IBM respectively as it is a simple, rapid and technically less demanding procedure which can be used in all clinical laboratories.
Department of Microbiology, Subharti Medical College, Meerut, Uttar Pradesh, India.
Deepika
D
Handa
Anita
A
Pandey
Ashish Kumar
AK
Asthana
Ashutosh
A
Rawat
Seemant
S
Handa
Bhaskar
B
Thakuria
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism*; D017714:Community-Acquired Infections / Q000382:microbiology; D003428:Cross Infection / Q000382:microbiology; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D001618:beta-Lactamases / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D047090:beta-Lactams; C048795:AmpC beta-lactamases; D001618:beta-Lactamases