A STUDY OF THE EXTENDED-SPECTRUM β LACTAMASES PRODUCED BY ENTEROBACTERIACEAE VERSUS DIFFERENT CEPHALOSPORINS

Abstract

In the present study, a total of seventy five Enterobacteriaceae and Pseudomonas spp. isolates were collected from different clinical sources and subjected to biochemical tests. These isolates were found to be forty one Klebsiella pneumoniae, twenty one Escherichia coli, eight Pseudomonas aeruginosa, two Enterobacter cloacae, two Citrobacter freundii and one Proteus mirabilis. Thirteen isolates were selected for further identification using the API 20E kits. These 75 isolates were subjected to antibiotic sensitivity testing by the agar disc diffusion technique against 21 antibiotic discs and to the determination of minimum inhibitory concentration (MIC) using the agar dilution technique against 16 antibiotics belonging to different classes with special emphasis on the four cephalosporin generations. The data were analyzed for MIC range, MIC,o and MIC,o as well as for S (sensitive) -- R (resistant) patterns. The results revealed that 64% of the isolates were multiresistant, among them 2.7% demonstrated resistance up to eighteen antibiotics. The percentages of susceptibility of the tested isolates to first, second, third and fourth generation cephalosporins were 36%, 73%, 76% and 83%, in order. Moreover, an obvious co-resistance between cephalosporins and non-{-lactam antibiotics was detected.