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

Abstract

Shiga toxin-producing Escherichia coli (STEC) O157 and non-O157 are food-borne pathogens and contaminants of foods of animal origin. This study was conducted to investigate the presence of virulence and integrase genes in STEC isolates from diarrhoeic calves in Fars Province, Iran. Five hundred and forty diarrheic neonatal calves were randomly selected for sampling. Rectal swabs were collected and cultured for isolation and identification of E. coli following standard methods. The isolates were analysed for the presence of class 1 integrons and bacterial virulence factors using polymerase chain reaction (PCR). Antimicrobial susceptibility testing was performed using the Kirby–Bauer disc diffusion method. Out of 540 diarrhoeic faecal samples, 312 (57.7%) harboured E. coli and 71 (22.7%) of them were identified as STEC: 41(69.5%) carried the stx2 gene, 21 (35.6%) carried the stx1 gene and 3 (5%) carried both. Twenty-six (44%) of the isolates showed the eae gene. Among the STEC isolates examined for susceptibility to eight antimicrobial agents, erythromycin and penicillin (96.8%) resistance were most commonly observed, followed by resistances to ampicillin (71.8%), tetracycline (62.5%) and trimethoprim/sulfamethoxazole (39%). Integrons were detected by PCR in 36% of the STEC tested isolates, 57 (89%) of which showed resistance to at least three antimicrobial agents. Our findings should raise awareness about antibiotic resistance in diarrhoeic calves in Fars Province, Iran. Class 1 integrons facilitate the emergence and dissemination of multidrug-resistance (MDR) among STEC strains recovered from food animals.

Hazard assessment and resistance profile of Escherichia coli strains isolated from bovine carcasses at the main slaughterhouses of Dakar, Senegal

“…The E. coli strains were resistant to tetracyclines (32%), colistin 26%, cefoxitin and cefepime12%, ampicillin, gentamicin and amoxicillin+clavulanic acid 11% and kanamycin 9%. These percentages are significantly lower than those reported by Kohansal and Ghanbari (2018) who obtained on a total of 52 isolates of bovine origin a resistance to ampicillin of 73% and tetracycline of 65%. The present results are not similar with those of Kohansal and Ghanbari (2018) because, in their study they have tested clinical strains from sick cows, which had probabily been in contact with antibiotics.…”

“…These percentages are significantly lower than those reported by Kohansal and Ghanbari (2018) who obtained on a total of 52 isolates of bovine origin a resistance to ampicillin of 73% and tetracycline of 65%. The present results are not similar with those of Kohansal and Ghanbari (2018) because, in their study they have tested clinical strains from sick cows, which had probabily been in contact with antibiotics. The resistance to tetracyclines can be explained by their wide range of uses in treating animal diseases due to their broad spectrum of activity.…”

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“…The overall prevalence of STEC in all samples and farms was 53%. Different prevalence of STEC among calves was studied and was 20% by Shaw et al, [23] 37.5% by Fukushima and Seki [24] 12.14% by Tahamtan et al, [25] 17.7% by Irshad et al, [26] and 22.7% by Kohansal and Asad [27].…”

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.…”