Molecular characterization of Eschericha coli isolated from raw milk samples with emphasis on their antibiotic resistance and virulence markers

Abstract EN

In the present study (10) E.coli strains previously isolated from (450) raw milk samples of different sources were analyzed for the determination of their antibiogram and screened for the presence of alkaline phosphatase gene (phoA) and virulence markers for Shiga toxin producing E.coli (STEC); stx1, stx2, and the occurrence of antibiotic resistance genes; nonspecific TEM β-Lactamase (blaTEM),Tetracycline A (tetA), which were investigated by Polymerase chain reaction.

Ten E.coli strains were tested for the antibiotic resistance by using the AST card of the VITEK2.

The antibiotic sensitivity test showed a high resistance towards Ampicillin (100 %), Tetracycline (80 %), Piperacillin(50 %) and Chloramphenicol, Cephaexin and Sulfamethaxole-Trimethoprim (40 %) for each and 30 % of the isolates showed intermediate resistance toward Amoxicillin and Clavulinic acid.

The polymerase chain reaction (PCR) was used to detect the genes encoding for alkaline phosphatase (phoA) , Shiga toxin type 1(stx1),Shiga toxin type 2( stx2) , Nonspecific TEM β-Lactamase (blaTEM),Tetracycline A (tetA).The results showed that all the investigated E.coli strains(n =10) harbored the alkaline phosphatase gene(phoA),100 %.The Shiga toxin type one encoding gene(stx2) was found in one E.coli strain (O158), while none of E.coli strains has the Shiga toxin type 1 gene (stx1).One hundred percentage of the screened E.coli strains carried the blaTEM gene, while 80% of the strains harbored the tetA gene.