DOI: 10.36347/sjams.2016.v04i02.028

Pages: 444-450

The objective of present study is to investigate the prevalences of AmpC enzyme and compared to the phenotypic tests in clinical isolates of Escherichia coli and Klebsiella pneumoniae. A total of 226 isolates (cefoxitininsucceptible: 96, cefoxitin-susceptible: 130) were included in this study. Screen positive isolates were selected for boronic acid-clavulonic acid inhibition test (BA-CA test), AmpC disk test (Tris-EDTA impregnanted), modified three dimensional test (M3DT), spot inoculation test, three dimensional extract test(3DET), and multiplex PCR were used. BA-CA test yielded positive result in 53 (55,2 %) of 96 cefoxitin-insusceptible isolates and 17 (13 %) of 130 cefoxitininsusceptible clinical isolates. Fourty-three (44,7 %) of 96 cefoxitin-insusceptible clinical isolates were confirmed as AmpC producers. Fourty-three (81,1 %) of 53 BA-CA positive isolates harbored ampC genes as demostrated by multiplex PCR. When used multiplex PCR as reference test; the sensitivities of AmpC disk test and modified three dimensional test were 67,5 % and 70 % respectively. The specifiticies of both of them were 60 %. Spot inoculation test, yielded positive result in 1 (2,3 %) of 43 AmpC enzyme producers. Three dimensional extract test yielded positive result in 2 of 4 AmpC enzyme producers. Used combination disk method of CLSI for detection of Extended Spectrum Beta Lactamase (ESBL) yielded positive result in 21 isolates. When BA was added to this test, the number of positive isolates of ESBL increased to 25 due to inhibition of AmpC with BA. BA-CA inhibition test is simple to perform and easy to interpret for the detection of AmpC beta-lactamases and ESBL.