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BMC Research Notes

, 7:217

First Online: 07 April 2014Received: 24 October 2013Accepted: 27 March 2014DOI: 10.1186-1756-0500-7-217

Cite this article as: Dehkordi, F.S., Yazdani, F., Mozafari, J. et al. BMC Res Notes 2014 7: 217. doi:10.1186-1756-0500-7-217


BackgroundFrom a clinical perspective, it is essential to know the microbial safety of fermented dairy products. Doogh and kashk are fermented dairies. These products are used by millions of people but their microbial qualities are unknown. Shiga toxin producing Escherichia coli STEC is one of the most commonly detected pathogens in the cases of food poisoning and food-borne illnesses. The present investigation was carried out in order to study the molecular characterization and antimicrobial resistance properties of STEC strains isolated from fermented dairy products.

MethodsSix hundred fermented dairy samples were collected and immediately transferred to the laboratory. All samples were cultured immediately and those that were E. coli-positive were analyzed for the presence of O157 , O26, O103, O111, O145, O45, O91, O113, O121 and O128 STEC serogroups, tetA, tetB, blaSHV, CITM, cmlA, cat1, aadA1, dfrA1, qnr, aac 3-IV, sul1 and ereA antibiotic resistance genes and stx1, stx2, eaeA, ehly, cnf1, cnf2, iutA, cdtB, papA, traT, sfaS and fyuA virulence factors using PCR. Antimicrobial susceptibility testing was performed also using disk diffusion methodology with Mueller–Hinton agar.

ResultsFifty out of 600 8.33% dairy samples harbored E. coli. In addition, yoghurt was the most commonly contaminated dairy. O157 26% and O26 12% were the most commonly detected serogroups. A significant difference was found between the frequency of Attaching and Effacing E. coli and Enterohaemorrhagic E. coli P <0.05. Stx1 44%, eae 36%, papA 32% stx2 30%, and ehly 28% were the most commonly detected virulence factors. The genes encode resistance against tetracycline tetA and tetB 76% and 70%, respectively, cephalothin blaSHV 38%, ampicillin CITM 36% and gentamicin aac 3-IV 32% were the most commonly detected. High resistance levels to tetracycline 84%, penicillin 46%, ampicillin 38% and streptomycin 36% were observed.

ConclusionFermented dairy products can easily become contaminated by antibiotic resistant STEC strains. Our findings should raise awareness about antibiotic resistance in Iran. Clinicians should exercise caution when prescribing antibiotics, especially in veterinary treatments.

KeywordsShiga toxin-producing Escherichia coli Virulence factors Antibiotic resistance properties Fermented dairy products Iran AbbreviationsE. coliEscherichia coli

STECShiga toxin producing Escherichia coli

EHECEnterohemolysin or Enterohaemorrhagic Escherichia coli

PCRPolymerase chain reaction

StxShiga Toxin



Cnf1Cytotoxic Necrotizing Factor

HUSHemolytic Uremic Syndrome

CDTCytolethal Distending Toxin

SPSSStatistical Package for the Social Sciences.

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Author: Farhad Safarpoor Dehkordi - Farshad Yazdani - Jalal Mozafari - Yousef Valizadeh


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