Identification of multiple strains of Staphylococcus aureus colonizing nasal mucosa of food handlers Original Research Article

The occurrence of multiple strains of Staphylococcus aureus colonizing the nasal mucosa of food handlers was investigated. Samples were collected from the anterior nares of 47 food handlers and were streaked on plates of Baird-Parker agar. From each plate, three typical colonies of S. aureus, with similar morphologies, were picked up and identified by biochemical tests. S. aureus isolates were typed by antibiotic susceptibility and pulsed-field gel electrophoresis (PFGE). Results indicated nasal carriage of S. aureus in 14 (30%) of the personnel. The isolated micro-organisms were resistant to penicillin and amoxicillin+clavulanic acid (70% and 45% of the isolates, respectively). All isolates were sensitive to vancomycin, rifampicin, cephalothin, oxacillin, chloramphenicol, gentamycin, and ofloxacin. Typing methods indicated that 11 among the 14 food handlers harbored multiple strains of S. aureus per carrier. Such results demonstrate that multiple isolates of S. aureus need to be strain-typed per food handler when attempts are made to identify sources of food poisoning, in epidemiological studies and in investigations of food contamination sources.