Assessing the Antimicrobial Resistance Patterns and in Vitro Efficacy of three Disinfectants as teat dip against Iodine (0.5%) Resistant Mastitogenic Pathogens

Dairy animals are facing a new challenge of increase bacterial resistance to some of the existing antibacterial agents. This study aimed to determine the antimicrobial resistance patterns and to evaluate in vitro efficacy of three teat dips, "chlorine dioxide, iodine glycerin (0.8%) and lactic acid /emollient (2%)" disinfectants against mastitogenic bacteria resistant to iodine (0.5%) in dairy herds. A cross sectional study was conducted in dairy cattle farm had a previous history of mastitis problem with high culling rate. All the udders of lactating cows were examined clinically and bacteriologically for isolation of mastitis causing bacteria then identified biochemically and serologically. All the bacteria isolated were subjected to antimicrobial susceptibility test by broth macro dilution method to iodine (0.5%) then forty five bacterial isolates showed iodine resistant were re-tested for their sensitivity to three tested disinfectants. Results revealed that the total prevalence of mastitis at cow and quarter levels were (30.0% and 18.67% resp.,). The most prevalent pathogens isolated were Coagulase negative staphylococci (CNS) (45.53%) followed by S.aureus (42.86%) and E.coli (O166) (11.61%). Regarding, antimicrobial sensitivity test, iodine (0.5%) showed the lowest bactericidal effect at different exposure times compared to tested disinfectants, Moreover, E.coli (O166) isolates showed highest resistant to iodine at 5 minutes exposure (50 %) followed by S.aureus and CNS & (30 % & 25% resp.,), Comparing the bactericidal effect of three tested disinfectants against bacterial isolates in vitro revealed that at 60 sec, both of iodine glycerin (0.8%) & lactic acid/emollient(2%) exhibited a highest lethal effect against CNS & S.aureus isolates (100%) compared to Chlorine dioxide (87% &85% resp.,) at 5 minutes exposure meanwhile, lactic acid/emollient (2%) had the highest effect against E.coli followed by iodine glycerin(0.8%) at 60 sec & 5 min then chlorine dioxide . In conclusion, in vitro testing of teat disinfectant resistance patterns against mastitogenic bacteria must be done regularly in dairy herds accompanied with application of disinfectant with lowest resistant such as lactic acid/emollient (2%) or iodine glycerin (0.8%) provide approaches to minimize the further development of antimicrobial resistance and improve the efficacy of bovine mastitis prevention programs.