Purification and characterization of Staphylococcus aureus enterotoxins for subsequent detection.

Abstract

Staphylococcus aureus is a food-borne pathogen mainly detected in finished dairy products and the direct detection of pathogens from food is possible with careful attention to sample preparation. It is a leading cause of bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device-related infections. S. aureus causes a wide range of infections commonly involving the skin, soft tissue, bone, joints, and infections associated with indwelling catheters or prosthetic devices. S. aureus is a common commensal of the skin and mucosal membranes of humans, with estimates of 20–30% for persistent and 60% for intermittent colonization. Because S. aureus does not compete well with indigenous microbiota in raw foods, contamination is mainly associated with improper handling of cooked or processed foods, followed by storage under conditions which allow growth of S. aureus and production of the enterotoxin (s). Air, dust, and food contact surfaces can also serve as vehicles in the transfer of S. aureus to foods. In this work 68 S. aureus isolated from mastitic cows (n=48), camel milk (n=5) and human samples (urine n = 4, abscesses aspiration n = 3, sputum n = 2, nasal swabs n = 2, vaginal swab n = 1 and wound swabs n = 3) were investigated using phenotypic and molecular identification to detect the occurrence of enterotoxins. Eighteen out of 48 S. aureus isolated from mastitic cows and 5 out of 15 S. aureus isolated from human samples were enterotoxin producers. All toxigenic S. aureus isolated from clinical mastitic cows (13) were toxin type D producer while seband sed were detected from subclinical mastitic cows. Among human isolates, 2 isolates produced mixed toxins A and E, 2 isolates produced mixed toxins C and D and one isolate produced type C toxin. No toxin was detected from camel isolates. Five S. aureus crude enterotoxin type D were investigated by protein SDS-PAGE. It was clear that all isolates had from 7 to 9bands. All the isolates had a band at 147-159 kDa, 35-42 kDa, 28-30 kDa, 23-26 kDa, 20-22 kDa and 18-19 kDa. 4 isolates had a band at 48-55 kDa, 3 isolates had a band at 39-42 kDa, 3 isolates had a band at 31-34 kDa and one isolate had a band at 17kDa.