Comparative Evaluation of Leukotoxic Activities of Indigenous Staphylococcus aureus Isolates from Subclinical and Clinical Mastitic Milk Samples of Buffalo and Cattle

Abstract

The present study was conducted for the comparative evaluation of leukotoxic activities of indigenous Staphylococcus aureus isolates issued from Institute of Microbiology University of Agriculture Faisalabad Pakistan. A total of 200 milk samples 100 each of buffalos (Nili Ravi) and cattle (Sahiwal) with subclinical and clinical mastitis were collected. Staphylococcus aureus isolates recovered were used for extraction of leukotoxins. Leukotoxic activities were determined against bovine Polymorphonuclear cells (PMNs) through Toxin Limit Concentration (TLC) assay. Overall positive percentage of mastitis was more important in cattle (32%) than for buffalos (22%). Overall and quarter based prevalence of subclinical mastitis were higher than clinical cases in both buffalos and cattle. In TLC assay, PMNs remained normal in control wells without leukotoxins after incubation at 37 0 C for 30 minutes, whereas, under the influence of leukotoxins, PMNs flattened and spread on the gelatin coated plastic surface. TLC titers in subclinical mastitis ranged from 4 to 16 with Geometric Mean Titer (GMT) at 6 in buffalos and 8 in cattle whereas, in clinical cases it ranged from 32 to 128 with GMT of 64 in buffalo and cattle.