Detection of Amp C beta lactamases production in clinical isolates of Escherichia coli and Klebsiella pneumoniae using Inhibitor based method

Amp c enzymes can be delineated from extended spectrum beta lactamases by their ability to hydrolyse cephamycins as well as extended spectrum cephalosporins. They are reported with increasing frequency, but the rate of its occurrence remains unclear. This study was undertaken to determine the occurrence of AmpC enzymes harbouring Escherichia coli and Klebsiella pneumoniae clinical isolates from our hospital. A total of 150 clinical isolates were subjected to susceptibility test with cefoxitin and third generation cephalosporin (3GC) antibiotics ampicillin, amikacin, cotrimaxazole, gentamycin, meropenem, imipenem, ertapenem and tetracycline by disc diffusion method. Those isolates which were resistant to 3GC and cefoxitin were tested with Amp c disc method, Modified three dimension test, Inhibitor based method using Boronic acid for confirming AmpC beta lactamase. Among the 150 isolates 9 (6) isolates were cefoxitin resistant indicating AmpC production. Plasmid mediated AmpC was detected in 8 (88.8) of the 9 isolate which were cefoxitin resistant by Inhibitor base method using boronic acid. AmpC producers (77.7) were also ESBL enzyme producers. AmpC production was observed in total 10.66 E.coli and 1.3 K.pneumoniae. The Inhibitor based method using boronic acid is useful in identifying AmpC producers. Among the 150 isolates 99 (66.6) of them were Extended spectrum beta lactamase producers.