Phenotypic and Genotypic Characterization of Staphylococcus aureus Isolated from Raw Camel Milk Samples from Libya and its Histopathological Effects on Mice Liver

Abstract

Although milk is a highly valuable food, raw milk is a good medium for the growth and multiplication of many microorganisms. S. aureus causes a variety of diseases in human and animals, the infections vary greatly in severity. There may be a mild skin infection to severe pneumonia and septicemia. The present study was intended for isolation and characterization of S. aureus from camel raw milk collected from different regions in Libya (Tubrak, Shahat, Alsafsaf, Omar Al Mokhtar, Makailie, Labrag, and Gardas). In this study, S. aureus were isolated from six milk samples out of 220. All the 6 isolates showed β-hemolysis on blood agar media enriched with 5% sheep blood. Gram-stained smears of the pure cultures exhibited clusters of Gram-positive cocci. The isolates also fermented mannitol with the color change of MSA and production of small yellow colonies. All the 6 isolates produced dark gray to black colonies on Baird-Parker agar media due to tellurite reduction. These isolates were positive for catalase and coagulase tests. In catalase test, hydrogen peroxide was broken-down into water and oxygen. Production of oxygen was indicated by bubble formation, whereas the negative control did not produce any bubble. The isolates were identified as S. aureus by coagulase test. The positive result of coagulase test was confirmed by the formation of curd like clotting compared to negative control.