Efficacy of green silver nano particles of Azadirachta indica against Staphylococcus aureus isolated from bovine mastitis

Abstract

Background: Staphylococcus aureus being the major etiological agent of bovine mastitis causing huge economic loss of dairy sector in India, the research work was undertaken in and around Shirwal village of Satara district by screening of unorganized and organized farms for bovine mastitis to isolate, identify and to perform antibiogram studies of Staphylococcus aureus, furthermore green synthesis of Silver nanoparticles carried out using green leaves of Azadirachta indica and its characterization was performed by SEM, TEM and UV visible spectrophotometry. Efficacy of green silver nanoparticles against Staphylococcus aureus was investigated by Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) test.Method: A total of 270 milk samples of cow were screened for mastitis by using California mastitis test (CMT). The CMT positive milk samples were processed for isolation of erization Staphylococcus aureus and its identification was carried out with different biochemical tests. The antibiogram studies were undertaken to know the antibiotic susceptibility of isolated Staphylococcus aureus. The Green synthesis of nanoparticles was undertaken using fresh green neem leaves extract in which 0.1 N AgNO3 was added. Characterization was done by TEM, SEM and UV visible spectrophotometry. The In-vitro efficacy studies of GAgNP were carried out against Staphylococcus aureus isolated from bovine mastitis by microdilution MIC test for which the bacterial count in bacterial culture was maintained at 105 CFU/ml by serial dilution method. The combination with lowest MIC was used for MBC test.Result: Out of total 270 milk samples screened by California mastitis test (CMT) 200 samples were CMT positive in which prevalence of clinical, sub-clinical mastitis and chronic mastitis was 18%,71.5% and 10.5% respectively. 90 Staphylococcal isolates were obtained from CMT positive milk samples. Antibiogram studies of Staphylococcus aureus isolates revealed that all 90 isolates were methicillin resistant (MRSA) with highest sensitivity for Gentamicin. Green synthesis of Siver nanoparticles using green leaves of Azadirachta indica was confirmed with characterization by Transmissible Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Spectrophotometry. The in-vitro efficacy of green silver nanoparticles against Staphylococcus aureus using tests like Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) revealed the antimicrobial effect of Green Silver nanoparticles of Azadirachta indica against Staphylococcus aureus.