synergisric effects of bacteriophages and antibiotics against shiga toxigenic escherichia coli isolatrd from diarrheic calves

This study investigated the potential of coliphages as a means of decreasing the amount of antibiotics needed for treatment. shigatoxigenic e.coli (stec) strains were isolated from diarrheic calves within the hama governorate, syria. isolation was done with differential and selective media and biochemical confirmation. the presence of genes encoding shiga toxins (stx1 and stx2) was confirmed through multiplex polymerase chain reaction (pcr). antibiotic susceptibility testing of the bacterial isolates was also done. in addition, bacteriophages from wastewater from cattle barns were isolated and their synergistic potential was assessed when combined with the antibiotics streptomycin, oxytetracycline, and neomycin. the stec isolates were resistant to antibiotics. the highest resistance rates were observed against amoxicillin (88%) and penicillin g (92%). notably, the phage-antibiotic combination therapy proved highly effective since the addition of bacteriophages reduced the minimum inhibitory concentration (mic) of streptomycin, oxytetracycline, and neomycin. in streptomycin, the combination mic was significantly lower than that of streptomycin alone (40 µg/ml streptomycin + 6 log₁₀ pfu/ml phages versus 250 µg/ml streptomycin alone). similarly, the mic for the oxytetracycline-phage combination (40 µg/ml + phages) was markedly lower than that of oxytetracycline alone (250 µg/ml). for neomycin, the combination (10 µg/ml + phages) also showed a significant mic reduction compared to neomycin alone (200 µg/ml).