Resistance and virulence factors in Escherichia coli from meat and milk

This study focused on the comparison and characterisation of Escherichia coli ( E. coli) isolates obtained from the meat of slaughtered animals (n = 34) and from raw cow’s milk (n = 33). Resistance to important antimicrobial substances and the presence of virulence factors were determined. Resistance to antimicrobials was tested using a disk diffusion method, while a polymerase chain reaction was used for the detection of selected genes encoding virulence – eaeA, hly, stx1, stx2. More than half the isolates of meat origin were resistant to at least one antimicrobial substance (67.7%). Resistance to ampicillin (50%) and tetracycline (41%) was found most frequently. Of 34 isolates from meat, 13 (38.2%) were multi-resistant. No stx1, hly or eaeA genes were detected in any of the E. coli isolates from meat. The stx2 gene was detected in one isolate. Only 4 (12.1%) isolates of milk origin were resistant to at least one antimicrobial substance – resistance to tetracycline was found in all cases. No virulence genes were detected in milk isolates. The results of our study indicate that resistance to antimicrobial substances is more common in isolates from meat than in isolates from milk. The only virulence gene stx2 detected in our study was found in an E. coli isolate of meat origin.