Background and Aim: Uropathogenic Escherichia coli (UPEC) isolates are the causative agents in the vast majority of all community and hospital-acquired urinary tract infections (UTI). Recent studies revealed that resistance to antimicrobial drugs in UPEC is increasing nowadays. In order to obtain a reasonable therapeutic effect, it is suggested that regarding to antibiogram patterns of frequent pathogens, local information should be established, revised and renewed as a reference for the selection of antimicrobial drugs. The aim of this study was to evaluate antimicrobial susceptibility patterns among UPEC isolated from UTI patients referred to an important referral hospital of Tehran, Iran.
Methods: UPEC isolates were collected from hospitalized patients (including adults and children) of all wards, plus referred outpatients, at Imam Khomeini Hospital in Tehran, Iran, during November 2013 and May 2014. Antimicrobial susceptibilities were evaluated by means of disk diffusion method according to CLSI (Clinical Laboratory Standards Institute) guidelines. For statistical analysis, the Chi-square test was used. Statistical significance was defined as a P value of < 0.05.
Results: A total number of 264 UPEC isolates were recovered from urine samples; out of them, 21 (7.4%) were children, 143 (50.7%) were adults and 100 (35.5%) were over 65 years old. Among the studied antibiotics, the highest level of susceptibility was documented to imipenem (99.6 %). In addition, susceptibility to amikacin and nitrofourantoin was also high (97.4% and 96.1% respectively). Moreover, the highest rate of resistance was notified in sulfamethoxazole/trimethoprim (61.0%). Resistance to ceftriaxone, ceftazidime and ciprofloxacin was high too. However, significant age-related differences were identified in the antibiotic susceptibility patterns. For instance, while all the isolated UPECs of the patients under 18 were susceptible to nitrofourantoin, the susceptibility rate of this antibiotic was significantly lower in the samples of older patients. On the other hand, the rate of resistance to ciprofloxacin among the patients over 18 was high, whereas in the younger patients a significantly lower resistance rate (9.5%) was noted. Meanwhile, there were statistically significant differences between the outpatients (with lower resistance rate) and the hospitalized patients and the patients admitted to emergency unit (with higher resistance rate) for sulfamethoxazole/trimethoprim, ciprofloxacin and ceftazidime. For example, the rate of resistance to ceftazidim among the samples of the outpatients was low (8.3%), while the isolated UPEC from the hospitalized patients and the emergency department patients revealed the significantly higher rate of resistance (34.1% and 44.7%, respectively).
Conclusion: By comparing the results of this study with previous ones, it seems that resistance pattern in UPEC is changing and antibiotic resistance in some antibacterial agents such as sulfamethoxazole/trimethoprim has increased. In addition, it seems that for choosing the appropriate antibiotic against UPEC, the age of patient and the source of UTI are important and should be considered by physicians.