Purpose: To investigate the distribution of plasmid-encoded extended spectrum beta-lacatamases
(ESBLs) in Lahore, Pakistan using different phenotypic and molecular methods.
Methods: Escherichia coli
and
Klebsiella
spp were obtained over a period of nineteen months (June
2007 to December 2008). Both were tested by the double disk synergy test, combined disk test and
Epsiometer-test (E-test) to evaluate their ability to detect ESBLs. The genotypes of ESBLs were
analyzed by monoplex polymerase chain reaction (PCR), multiplex PCR, DNA sequencing and
isoelectric focusing.
Results: 662
E. coli and 153
Klebsiella spp were analyzed. Among these isolates, 39.3 %
E. coli and
26.1 %
Klebsiella spp were positive for extended spectrum beta-lactamases (ESBLs).71.9 %
E. coli and
79.6 %
Klebsiella spp showed minimum inhibitory concentration (MIC) in the range > 32/0.064 = 500
μl/mL for cetatzidime/cetatzidime + clavulanic acid, while 66.5 %
E. coli and 69.1 %
Klebsiella spp
revealed MIC in the range of > 16/0.016 = 1000 μl/mL for cefotaxime/cefotaxime + clavulanic acid.
Antibiotic susceptibility testing revealed that imipemem, meropenem and tazocine were the most
effective in the management of such infections. The most frequent genotype of ESBL was OXA (19.2
%) for
E. coli and SHV (92.5 %) for
Klebsiella spp. The highest genotypic combination found was the
combination of TEM/OXA (44.2 %) for
E. coli.
Conclusion: The resistance of
E. coli and
Klebsiella spp-producing ESBLs in Pakistan is a serious
issue, and TEM, OXA and SHV type ESBL were the most common genotypes. Some isolates produced
two or three genotypes at a time. Multiplex PCR of ESBL may help in early detection as well as
phenotypic antibiotic therapy of these infections.