Cross- sectional study of urinary pathogens and their antibiotic susceptibility pattern with refernce to extended spectreum beta lactamase (ESBL) producing strains in Kathmandu model hospital

Abstract

Extended spectrum β-lactamases (ESBLs) hydrolyse expanded spectrum cephalosporins like ceftazidime, cefotaxime and monobactam aztreonam. ESBL producing bacteria may not be detectable in the routine disc diffusion susceptibility tests leading to inappropriate use of antibiotics and treatment failures. Thus, in order to detect antibiotic susceptibility pattern of urinary tract isolates of family enterobacteriaceae with reference to extended spectrum β-lactamase (ESBL) producing strain, a study was conducted among patients attending the outpatient department and hospitalized patients of Kathmandu Model Hospital, who were suspected of urinary tract infection (UTI) during the six months from 1-March-2006 to 31-August-2006. Altogether, 435 urine samples collected were investigated by conventional semi-quantitative culture technique, microscopy, antibiotic susceptibility test and ESBL detection test. Out of 435 urine samples, only 23.91% (104/435) showed significant growth. The highest percentage of growth positive samples 29.81% (31/104) belonged to the age group 20-30 years. Status of bacteriuria was found slightly higher in females (26.10%i.e.71/272) than in males (20.25% i.e.33/163) and higher in inpatients (28.17% i.e.20/71) than in outpatients (23.08% i.e. 84/364). Among 104 isolates, E. coli (88.46%) was found to be the most predominant isolate followed by Enterobacter aerogens (3.85%), Acinetobacter species (1.92%), Pseudomonas aeruginosa (0.96%), Proteus vulgaris (0.96%), Citrobacter freundii (1.92%) and Staphylococcus aureus (1.9%). Out of 104 isolates, 63 (60.6%) were MDR. And also among 104 isolates 16 (15.38%) were ESBL producing strain. The prevalence of ESBL strains was found to be higher (20.00% i.e. 4/20 ) in admitted patient than in outpatient 14.29% i.e. 12/84 and also the prevalence of ESBL strain was found to be higher in male (18.18% i.e. 6/33) than female (10/71). Out of 92 E. coli isolates, 16.30%i.e. 15/92 were ESBL strains while 25% i.e. ¼ of E. aerogenes were found to be ESBL strains. Based on invitro susceptibility test and phenotypic Double Disc Synergy Test (DDST), it was concluded that a significant number of urinary isolates are MDR and often co-produce ESBL, which can result in unavoidable treatment failures. No doubt the reporting of MDR and ESBLs and other β-lactamases should continue to challenge treatment strategy for years to come.

Key Words: MDR, ESBL, Double Disc Synergy test