Susceptibility patterns of Escherichia coli: prevalence of multidrug-resistant isolates and extended spectrum beta-lactamase phenotype.

OBJECTIVE: To study Escherichia coli (E. coli) susceptibility, prevalence of multidrug-resistant isolates and possible role of extended spectrum beta-lactamases (ESBL) in E. coli resistance. SETTING: Department of Medicine, Shifa College of Medicine, Islamabad. METHODS: Three hundred and seventy eight E. coli isolates from different sources were identified during six-month period. Susceptibility to various antibiotics was checked using standard methods. Multidrug-resistant isolates were separated. Isolates resistant to cefpodoxime and aztreonam were considered as ESBL phenotype, indicating ESBL production. RESULTS: Most of isolates were resistant to ampicillin and trimethoprim/sulfamethoxazole. Overall resistance to ciprofloxacin, ceftriaxone, cefotaxime and cefpodoxime was 49%, 34%, 36% and 38% respectively. Resistance to fourth generation cephalosporins was lower. Almost all Isolates were sensitive to amikacin, imipenem and tazobactam. Aztreonam resistance was found in 25% isolates. Similar pattern was observed for urinary E. coli isolates; 45% E. coli isolates were found to be multidrug-resistant. Nitrofurantoin showed low-level resistance both to multidrug-resistant as well as urinary isolates. Resistance to both cefpodoxime and aztreonam was found in 25% isolates suggesting ESBL production. CONCLUSION: E. coli resistance in Pakistan is much higher than reported from western literature. Multidrug-resistant isolates, including third generation cephalosporins and quinolones, are very common. ESBL production may contribute to this high level resistance against beta-lactams.