Virulence factors, serogroups and antimicrobial resistance properties of Escherichia coli strains in fermented dairy products.
BACKGROUND
From 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.


METHODS
Six 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.


RESULTS
Fifty 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.


CONCLUSIONS
Fermented 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.
Young Researchers Club and Elite, ShahreKord Branch, Islamic Azad University, P,O, Box 166, ShahreKord, Iran. Dr.Farhads@yahoo.com.
Farhad Safarpoor
FS
Dehkordi
Farshad
F
Yazdani
Jalal
J
Mozafari
Yousef
Y
Valizadeh
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003611:Dairy Products / Q000382:microbiology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D005285:Fermentation; D005516:Food Microbiology; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007492:Iran; D008826:Microbial Sensitivity Tests; D012703:Serotyping; D054323:Shiga-Toxigenic Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification* / Q000472:pathogenicity; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D037521:Virulence Factors