Prevalence of extended spectrum beta-lactamase production among uropathogens in south Mumbai and its antibiogram pattern

Abstract

β-lactams are the most widely used group of antimicrobials. However, increasing resistance to these valuable drugs in uropathogens, mediated principally by β-lactamases, has become a major concern. The present study was undertaken to determine the prevalence of Extended Spectrum β-Lactamase (ESBL) producers in clinical isolates of urine specimens, collected from various healthcare centres across south Mumbai. A total of 195 gram negative urine isolates were identified as Pseudomonas aeruginosa (13), Proteus mirabilis (21), Klebsiella pneumoniae (29), Escherichia coli (96), Enterobacter aerogenes (1), Enterobacter cloacae (1), Enterococcus fecalis (1), Morganella morganii (1), Citrobacter diversus (16), Citrobacter amalonaticus (5) and Proteus vulgaris (11). Antimicrobial Susceptibility Testing (AST) by Kirby-Bauer method showed 43.07 % (84/195) of the isolates were resistant to more than 70 % of the antibiotics used. Confirmatory screening using a combination of Double Disk Synergy Test (DDST), Phenotypic Confirmatory Disc Diffusion Test (PCDDT) and E-test revealed the overall prevalence of ESBL producers to be 34.71 % (68/195). The study showed 72.05 % of the ESBL producers to be resistant to fluoroquinolones, highlighting its extensive use in the region of south Mumbai. All ESBL producers were found to be sensitive to Imipenem whereas 82.36 % showed susceptibility to Amikacin making these 2 antibiotics the most effective choice of drug against ESBLs. In order to ensure rational treatment of highly resistant pathogens, the occurrence of ESBL and its primary studies may serve as a base for further research and findings.

Keywords: ESBL; beta-lactam; drug resistance; uropathogens.

Table 1. Standard zone sizes of antibiotics for ESBL screening as per CLSI guidelines (CLSI, 2012)

Table 2. ESBL producing uropathogens

Figure 1. Antibiotic sensitivity test (AST) showing highly resistant strain of Citrobacter diversus (resistant to 20 of the 24 tested antibiotics)

Figure 2. Isolate 70 (E. coli.) showing: (a) Positive PCDDT when swabbed on MH Agar and incubated with Ceftazidime (left) and Ceftazidime-Clavulanate (right). (b) Positive DDST when swabbed on MH Agar and incubated with (clockwise from top-left) Ceftazidime, Ceftriaxone, Cefotaxime, Aztreonam, and Amoxycillin-Clavulanate at the centre. (c) E-test showing positive ESBL production, with a ratio of Antibiotic: Antibiotic-Clavulanic acid > 8

Figure 3. Antibiogram showing resistance pattern of ESBL and non-ESBL-producing uropathogens towards different antibiotics