Distribution of class d oxacillinases amongst third generation cephalosporin resistant nosocomial uropathogenic escherichia coli isolates, their phylogenetic background and clonal analysis

Wide diversity of β-lactamases causes resistance to third-generation cephalosporins (3GCs) in uropathogenic E. coli (UPEC) the frequently encountered nosocomial pathogen creating treatment complications. In the present study incidence of OXA type ß-lactamase in 3GC resistant UPEC was explored. Phylogenic background and genetic relatedness between the isolates was also analyzed. 40.5% E. coli resistant to 3GCs were isolated from 190 urine culture positive samples from hospitalized patients clinically diagnosed for urinary tract infection (UTI). Highest resistance was observed against non-β-lactams; ciprofloxacin(100%), levofloxacin(90%), cotrimoxazole(95%) and intermediate resistance against amikacin(55%). ESBL(44.15%) production and β-lactamase inhibitor resistance (BLIR;55.84%) was observed with varied imepenem(100%, 88.37%) susceptibility respectively. Multiple β-lactamases (OXA group I, II, III, TEM, CTX-M) were prevalent. Occurrence of OXA group I, III and TEM was highest amongst ESBL(44.1%) compared to BLIR(32.6%) isolates. OXA group I, II and III β-lactamases either alone or in combinations with other β-lactamases were carried on IncF type plasmid (IncFrepB, IncFIB). Majority of the UPEC belonged to B2(75.32%) and D(22.07%) and their ERIC-PCR profiles indicated genetic homogeneity. This study for the first time demonstrated high distribution of OXA group I and III in 3GC resistant nosocomial UPEC isolates of homogeneous genetic origin from the eastern region of India.