Molecular Detection and Antimicrobial Resistance Patterns of Shiga Toxigenic Escherichia coli Isolated from Bovine Subclinical Mastitis Milk Samples in Kurdistan, Iran

Document Type: Original Articles

Authors

1 Department of Pathobiology, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

2 Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran

3 Department of Basic Sciences, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

Abstract

Bovine subclinical mastitis is regarded as a devastating disease due to the economic costs imposed on dairy husbandry. Moreover, it is a hazard in the public sector in the cases of zoonotic bacteria because of the potential role of unpasteurized milk and dairy products to propagate the infectious agent to the human food chain. The present study aimed to evaluate the frequency, virulence content, and antimicrobial resistance profile of Shiga toxin-producing Escherichia coli (STEC) strains isolated from bovine subclinical mastitis in Kurdistan Province, West of Iran. A total of 400 bovine subclinical mastitis milk samples recognized in the California Mastitis Test were collected aseptically and analyzed for the presence of E. coli phenotypically and molecularly. The isolates were genotypically screened for stx1, stx2, and eae genes. Furthermore, O157:H7 STEC strain was searched among the isolates in a duplex polymerase chain reaction. The antimicrobial resistance scheme of the isolates was determined using the agar disk diffusion method. In general, 173 (43.25%) E. coli isolates were detected among which 39 (22.54%) isolates were STEC. The frequency of STEC virulence genotypes was stx2 (25 isolates, 64.10%), stx2+eae (6 isolates, 15.38%), stx1+stx2 (6 isolates, 15.38%), and stx1+stx2+eae (2 isolates, 5.12%). In addition, three O157: H7 strains were identified with the genetic content of stx1+stx2+eae (2 isolates) and stx1+stx2 (1 isolate). The most prevalent antimicrobial resistance was observed against streptomycin, tetracycline, and ampicillin. Gentamycin, amoxicillin-clavulanic acid, and trimethoprim-sulfadiazine were the most effective antibiotics against O157 strains, whereas gentamycin, ciprofloxacin, and nitrofurantoin were effective against non-O157 strains. The results revealed the significant role of STEC in bovine subclinical mastitis in the studied region. In addition, the distribution of O157:H7 strain and high prevalence of multidrug resistance among the isolates is a matter of concern. Therefore, there is a potential threat of human infection following the consumption of contaminated milk with STEC in Kurdistan Province, Iran. 

Keywords


Article Title [French]

Détection Moléculaire et Modèles de Résistance aux Antimicrobiens de Escherichia coli Productrices de Shiga Toxines Isolés d'Échantillons de Lait de Mammite Subclinique de Boviné au Kurdistan, Iran

Abstract [French]

La mammite subclinique du boviné est considérée comme une maladie dévastatrice en raison des coûts économiques imposés à l'industrie laitière. De plus, c'est un danger dans le secteur public dans le cas des bactéries zoonotiques en raison du rôle potentiel du lait et des produits laitiers non pasteurisés dans la propagation des agents infectieux dans la chaîne alimentaire humaine. Cette étude visait à évaluer la fréquence, la virulence et le profil de résistance aux antimicrobiens des souches d'Escherichia coli productrices de Shiga-toxines (STEC) qui ont été isolées de la mammite subclinique des bovinés dans la province du Kurdistan, à l'ouest de l'Iran. Un total de 400 échantillons de lait de mammite subclinique de boviné, identifiée par le test de mammite de Californie, a été prélevé aseptiquement et analysé pour la présence d'E. Coli phénotypiquement et moléculairement. Les isolats ont été sélectionnés génotypiquement pour les gènes stx1, stx2 et eae. En outre, la présence de la souche O157: H7 STEC a été explorée parmi les isolats par le biais d’une réaction en chaîne par polymérase duplex. Le profil de résistance aux antimicrobiens des isolats a été déterminé en utilisant la méthode de diffusion sur disque d'agar.Au total, 173 isolats d'E. Coli (43,25%) ont été détectés, dont 39 (22,54%) étaient des STEC. La fréquence des génotypes de virulence STEC était stx2 (25 isolats, 64,10%), stx2+eae (6 isolats, 15,38%), stx1+stx2 (6 isolats, 15,38%) et stx1+stx2+eae (2 isolats, 5,12 %). En outre, trois souches O157:H7 ont été identifiées avec le contenu génétique correspondant au stx1+stx2+eae (2 isolats) et stx1+stx2 (1 isolat). La résistance antimicrobienne la plus répandue a été observée contre la streptomycine, la tétracycline et l'ampicilline. La gentamycine, l'amoxicilline-acide clavulanique et la triméthoprime sulfadiazine étaient les antibiotiques les plus efficaces contre les souches O157, tandis que la gentamycine, la ciprofloxacine et la nitrofurantoïne étaient efficaces contre les souches non-O157. Les résultats ont révélé le rôle important des STEC dans la mammite subclinique du boviné dans la région étudiée. De plus, la distribution de la souche O157:H7 et la forte prévalence de la résistance aux médicaments multiples parmi les isolats est un sujet de préoccupation. Par conséquent, il existe une menace potentielle d'infection humaine suite à la consommation de lait contaminé par STEC dans la province iranienne du Kurdistan.

Keywords [French]

  • Boviné
  • Résistance aux médicaments
  • Mammite
  • Escherichia coli productrices de Shiga-toxines (STEC)
  • virulence
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