Role of antigen-۴۳ on biofilm formation andhorizontal antibiotic resistance gene transfer in non-O۱۵۷ Shiga toxin producing Escherichia coli strains

Background and Objectives: The objectives of this study were to evaluate the antibioticresistance profiles, biofilm for- mation, presence of antigen ۴۳ (Ag۴۳) gene, and transfer ofantibiotic resistance phenotype among non-O۱۵۷ Shiga toxin producing Escherichia coli(STEC).Materials and Methods: Total of ۲۷۶ stool samples were collected from healthy calves,goats and ۳۹۵ patients with the sign of nonbloody diarrhea and screened for presence of stxand serotype O۱۵۷ genes by polymerase chain reaction (PCR) technique. Susceptibility to ۱۴antibiotics was determined as per CLSI guideline. Pres- ence of Ag۴۳ and intimin (eaeA) geneswere detected by PCR. Biofilm formation was measured by microtiter plate method.Conjugation was carried out by membrane filter technique.Results: We isolated ۷۴ (۹۳.۶%) non-O۱۵۷ STEC strains from ۴۱ calves, ۳۳ goats and ۵(۶.۳%) patients’ stools, however, no O۱۵۷ serotype was detected in our study. Resistance wasobserved most commonly to tobramycin (۶۶.۲%), kanamycin (۴۸.۶%), and amikacin (۲۹.۷%)and less frequently to ciprofloxacin (۴.۱%), amoxicillin-clavulanic acid (۵.۴%), and cef- triaxone(۹.۵%) in isolates recovered from calves and goats fecal samples, whereas, all human isolateswere sensitive to ceftazidime, ciprofloxacin, tobramycin and imipenem, respectively.Furthermore, Ag۴۳ was detected in ۶۰ STEC isolated from animals and ۵ human origins (noeaeA gene was found in this study). Biofilm formation from Ag۴۳+ and Ag۴۳- colonies showed ۲۰ isolates with strong biofilm activities. Cefotaxime resistance phenotype was transferred toE. coli ATCC ۲۵۹۲۲.۱ (Nalr) by conjugation at a frequency of ۱.۶×۱۰-۴.Conclusion: From the above results we concluded that, human infections with non-O۱۵۷STEC were significantly low in Kerman. Ag۴۳ was insignificant with biofilm quantity in mostcases