Prevalence and Antibiogram profiles of STEC strains isolated from raw cow's milk in New-Valley Governorate, Egypt

A cross sectional study was conducted to isolate and identify Shiga toxinproducing Escherichia coli (STEC) from raw cow milk. A total of 267 milk samples were collected from apparently healthy cattle in 7 different dairy farms. Thirty-nine STEC isolate were identified out of 86-positive E. coli strains (56.98%). The prevalence of E. coli and STEC was 32.2% and 18.4%, respectively. Antimicrobial susceptibility of the isolated STEC was determined by disc diffusion method. A total of 16 antimicrobials of seven antimicrobial classes were used. Commercially available antibiotic disc namely aminoglycosides [Erythromycin (15 μg), Clindamycin (2μg, Kanamycin (30 μg, Amikacin (30 μg) , Gentamicin (10 μg), cephalosporins (Cefepime (30 μg, Cefotaxime (30μg), Cefazolin (30μg], Fluoroquinolones [Naladixic acid (30 μg), Ciprofloxacin (5 μg), Levofloxacin (5μg)], penicillin (Ampicillin 10 μg),Tetracycline (tetracycline 30 μg), Sulphonamides (Sulphamethoxazol 30 μg, and Carbapenems [Meropenem 10 μg, Imipenem 10 μg] were used. E. coli strain ATCC25922 was used as a control strain in the experiment. Highest resistance was observed against erythromycin (100%) followed by cefepime (97.4%) and clindamycin (82.1%), Nalidixic acid (61.5%), sulphamethazon (48.7%), tetracycline (41.0), kanamycin (33.3%), and cefotaxime (33.3%). Carapenems were found to be the most effective antimicrobial group where the examined STEC isolates were susceptible to Imipinem at 97.4% (38/39), followed by Meropenem at 94.9% (37/39). Results showed that multidrug resistance STEC isolates were 81.25% of the tested antimicrobial (13/16). In conclusion, high prevalence of STEC in raw milk indicate insufficient hygienic measures adopted during milking and handling and verify that raw milk is potential source of these multidrug resistant strains.