Antibiotic resistance and virulence patterns of pathogenic Escherichia coli strains associated with acute gastroenteritis among children in Qatar
Abstract
Background: The treatment of Enterobacteriaceae family including diarrheagenic E. coli (DEC) has been increasingly
complicated due to the emergence of resistant strains. Here we report on the phenotypic resistance profiles and
ESBL genotype and virulence profiles of Enteroaggregative E. coli (EAEC) and Enteropathogenic E. coli (EPEC)
isolated from children hospitalized with acute gastroenteritis in Qatar (AGE).
Results: E. coli were isolated and characterized from 76 diarrheagenic stool positive samples, collected from
hospitalized children less than 10 years old. Isolates were tested for antibiotic susceptibility against eighteen
clinically relevant antibiotics using E-test method. Conventional PCR was performed to detect genes encoding ESBL
and virulence factors. Chi-square test was performed to compare the individual antibiotic resistance between EPEC
and EAEC.
A significant percentage (73.7%) of isolates were resistant to at least one antibiotic. Overall, high resistance (70%)
was reported to the first-line antibiotics such as ampicillin, tetracycline (46.4%), and sulfamethoxazole-trimethoprim
(42.9%). Further, 39.5% of the isolates were multidrug resistant (MDR), with 22.4% being ESBL producers. On the
other hand, all isolates were susceptible to carbapenem, fosfomycin, amikacin and colistin. The incidences of
resistance to the 18 antibiotics between EPEC and EAEC were not significantly different by Pearson chi -square test
(P > 0.05). Genetic analysis revealed that 88.23% of ESBL production was bla CTX-M-G1 (bla CTX-M-15, bla CTX-M-3) -
encoded. Several different combinations of virulence markers were observed, however, there was no specific trend
among the isolates apart from absence of the bundle-forming pilus (bfpA) gene, which encodes the type IV
fimbriae in EPEC adherence factor (EAF) plasmid (pEAF), among all EPEC (atypical). 15% of the EAEC strains were
positive for a combination of astA, aap & capU, while 10% were positive for three different combinations. The aap,
aatA, capU and aggR virulence genes showed the highest frequency of 65, 60, 55 and 55% respectively. Others
genes, east, astA, and aai, showed frequencies of 35, 30 and 20% respectively.
Conclusions: Atypical EPEC and EAEC were the primary etiological agents of diarrhea in children among DEC
pathotypes. Our results indicated high rate of antimicrobial resistance pattern of DEC strains, which necessities the
development of regulatory programs and reporting systems of antimicrobial resistance in DEC and other AGEassociated
bacteria to insure effective control of diarrheal diseases. Results from this study demand a further
research on identifying the phenotypic and genotypic profiles of more DEC pathotypes in various clinical samples.
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