Conventional and Rapid Methods for Identification of Staphylococcus aureus from Clinical Specimens

Abstract

Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium whose incidence ranges from skin, soft tissue, respiratory, bone, joint, endovascular to wound infections. The purpose of this study was to identify Staphylococcus aureus from clinical specimens using routine conventional and rapid tests. Gram staining, catalase test, coagulase test, DNase test, haemolysis on blood agar and Microgen™ STAPH-ID kit tests were carried out. A total of 125 Gram positive cocci were tested. The Gram staining technique yielded 100 (80.00%) Staphylococcus spp (Gram positive cocci in clusters). 89(71.20%) isolates were positive to haemolysis on blood agar. Mannitol Salt Agar, DNase agar and Catalase test correctly identified 69 (55.2%) of the Gram positive cocci to be S. aureus as was confirmed by the Microgen™ STAPH-ID kit test. Coagulase test yielded 66 (52.8%) positive results. The Microgen™ STAPH-ID kit test identified three non-coagulase Staphylococcus aureus isolates. The Microgen™ STAPH-ID kit test was the most reliable of the tests, with accuracy comparable to any other rapid test. However, it is the most expensive of the tests. This study established that conventional tests can be used for direct identification of S. aureus to species level if the battery of tests is increased.