Antimicrobial Susceptibility Patterns of Enteroaggregative E. coli, as the Most Common Diarrheagenic E. coli, Associated to Gastroenteritis Outbreaks in Iran

Acute diarrhea, a leading cause of morbidity and mortality worldwide, still remains a major global health problem, especially among children in the developing countries. Diarrheagenic E. coli represent one of the most common etiological causes of diarrhea in children worldwide.
This study was conducted in order to determine the rate of Enteroaggregative E. coli (EAEC) among 50 E. coli isolates as well as its antimicrobial resistance patterns.
A total of 50 Escherichia coli strains had been isolated among children under 5 years of age during 75 reported outbreaks in various provinces of Iran from October 2013 to May 2014. PCR was employed for the identification of different groups of diarrheagenic E. coli. Antimicrobial susceptibility testing was performed using disc diffusion methods. In addition, extended spectrum beta-lactamase (ESBL) production ability was checked by way of combination disc methods of CLSI. Minimum inhibitory concentration of cefotaxime, ceftriaxone, and ceftazidime in EAEC with the ability of ESBL production was determined using the micro-broth dilution method of CLSI.
Out of the 50 E. coli isolates, 17 were identified as Enteroaggregative E. coli (EAEC) in that they were positive for at least 1 of the 2 tested virulent genes: agg and aap. ESBL production ability was observed in 4/17 (23.5%) EAEC isolates. MIC of cefotaxime and ceftriaxone in ESBL positive EAEC varied between 8 - 32 µg/mL and 8 - 64 µg/mL, respectively. Resistance to ampicillin and nalidixic-acid (47.1%), trimethoprim/sulfamethoxazole (41.2%), and ciprofloxacin (11.8%) was observed among the EAEC isolates. No evidence of resistance to gentamycin and meropenem was detected.
This research has revealed that the most common type of diarrheagenic E. coli among children, who were affected in the diarrheal outbreak in different cities of the country, is Enteroaggregative E. coli (34%). The rate of ESBL positive cases in EAEC isolates were 23.5 %.