Molecular Characterization of Enterohemorrhagic <i>Escherichia coli</i> Isolates from Cattle

Abstract

A total of 21 (4.3%) enterohemorrhagic E. coli strains were isolated by biochemical tests and identification of the eae+stx1+stx2+ genotype from 490 stool samples obtained from calves with diarrhea during 1-year period from a major farm in Tehran, Iran. All of the strains showed resistance to ampicillin, ciprofloxacin, trimethoprim, streptomycin, chloramphenicol and tetracycline, while 19% showed resistance to gentamicin. Out of 21 EHEC strains, 11 (53%) harbored class 1 integron. Two different amplification products, which were approximately 750 and 1,700 bp in size, were obtained from amplified variable regions (in-F/in-R primers) in 3 (14.3%) and 4 (19%) of the EHEC isolates, which corresponded to dfrA7(dihydrofolate reductase type I) and dfrA1/aadA1(dihydrofolate reductase/aminoglycoside adenyltransferase) resistance gene cassettes, respectively, and this was confirmed by sequencing. Genotyping analysis revealed a total of 16 pulsotypes that corresponded to 16 isolates with the similarity indices of 62% and 30% for the most and least similar isolates, respectively, 9 of which harbored class 1 integron. Analysis of pulsotypes showed an extensive diversity among the isolates harboring integron, which is indicative of a lack of any significant genetic relatedness among the isolates. No obvious relation could be deduced between integron content and special pulsotypes. The little data available on the genotyping patterns of EHEC isolates from cattle and their resistance gene contents emphasize the need to establish genotyping databases in order to monitor and source track the source of emergence and spread of new resistant and integron-carrying genotypes.

Molecular analysis of Shiga toxin-producing Escherichia coli O157:H7 and non-O157 strains isolated from calves

“…In the present study, class 1 integron was identified in 23 (36%) out of 71 STEC isolates. Our data revealed low distribution of class 1 integrons among STEC isolates from calves with diarrhoea in the south of Iran compared with a similar study in northern Iran in 2014 for which the authors found a higher percentage (53%) of the strains containing integron class 1 (Bakhshi et al 2014 ). The various percentages of class 1 integrons in different parts of the world could be attributed to the characteristics of the analysed collection and differences in the prevalence of antibiotic consumption in each country (Kargar et al 2014 ).…”

“…Epidemiological observations show high levels of antimicrobial resistance in bacterial pathogens from veterinary and human medicine (Zhao et al 2001 ). This has led to the discovery that these bacteria are able to acquire antibiotic resistance by resistance-conferring genes, many of which are carried on transposons, plasmids or integrons (Bakhshi, Najibi & Sepehri-Seresht 2014 ). An integron is mainly composed of an integrase gene that encodes a site-specific recombinase, by which an insertion site of integron is recognised.…”

“…Many studies in various countries including Iran have shown that the distribution of integrons among enteric bacteria has increased over time (Eftekhari et al 2013 ; Gonzalez et al 1998 ; Hamada, Oshima & Tsuji 2003 ; Martinez-Freijo et al 1998 , 1999 ; Najibi et al 2012 ). In Iran, only a few studies have reported antimicrobial resistance properties and virulence genes in the pathogenic E. coli (Bakhshi et al 2014 ; Shahrani et al 2014 ). Unfortunately, there is no conclusive data on the distribution of virulence genes and the antimicrobial resistance properties of STEC strains isolated from Iran, particularly from Fars, which is one of the major agricultural and animal husbandry areas in Iran, with nearly 400 000 cattle and 8 000 000 sheep and goats (Shams et al 2012 ).…”

Prevalence of class 1 integron in Escherichia coli isolated from animal sources in Iran: a systematic review and meta-analysis

“…The database search yielded 205 citations. Among them, 196 were removed by index, title, and abstract screening and 9 were retrieved in full text [16][17][18][19][20][21][22][23][24]. Of 9 reviewed studies, in a study, samples were collected from aquaculture water [16], and the results of three studies were unclear thus, four studies were excluded upon a full-text search [22][23][24].…”

“…Of 9 reviewed studies, in a study, samples were collected from aquaculture water [16], and the results of three studies were unclear thus, four studies were excluded upon a full-text search [22][23][24]. Finally, based on inclusion criteria, 5 studies were included to meta-analysis [17][18][19][20][21]. The searching process for collection of qualified studies is shown in Fig.…”