Efficacy of Green Silver Nanoparticles (GAbNPs) against Multidrug Resistance in Staphylococcus aureus from Mastitis-infected Cows

Abstract

Background: Antimicrobial resistance being the major emerging problem for management of mastitis in cow hence, the research work was undertaken in a geographical area around Shirwal town in Satara district of Western Maharashtra, India to investigate the occurrence of multidrug resistance in Staphylococcus aureus (MDRSA) isolated from mastitic cow milk samples. Further assessment was carried out for antimicrobial efficacy of formulation of Green Silver Nanoparticles (GAgNPs) synthesized from Azadirechta indica against MDRSA of mastitis origin. Methods: A total of 250 milk samples from cows suspected of mastitis were screened by the California Mastitis Test (CMT). The CMT-positive samples were subjected to bacteriological investigation for the presence of S. aureus as an etiological agent. The isolates identified as S. aureus were further authenticated by the molecular method targeting 16s-rRNA and nuc gene. All isolates of S. aureus were subjected to an antimicrobial susceptibility test. The randomly selected MDRSA isolates were subjected to antimicrobial susceptibility testing with GAgNPs formulation were prepared from silver nitrate by reducing with Azadirachta indica leaf extract. Result: Out of 250 cow milk samples suspected for having mastitis were screened with CMT, 170 tested positive. From these milk samples 145 isolates of S. aureus were isolated and bacteriologically identified. When processed for antibiotic sensitivity 60 were detected having multidrug resistance. Maximum resistance was shown against beta-lactam antibiotics. GAgNP synthesized and characterized with visual appearance, spectroscopy and TEM (Transmission electron microscopy) and tested for in vitro antimicrobial efficacy against MDRSA showed significant antimicrobial property.