Genotyping of Staphylococcus aureus associated with nasal colonization among healthcare workers using DNA microarray

Healthcare workers (HCWs) colonized with Staphylococcus aureus may serve as a reservoir of infection. This study was carried to determine the genetic make-up of S. aureus nasal colonizers in HCWs. Nasal swabs were obtained from 93 HCWs and molecular characterization of identified S. aureus isolates was carried out using the StaphyType DNA microarray (Alere Technologies GmbH, Jena, Germany). Twenty-nine HCWs (31%) were colonized with S. aureus (MSSA = 23; MRSA = 6). Thus the overall MRSA carriage rate was 6.5% (n/N = 6/93) and 20.7% (n/N = 6/29) of those colonized with S. aureus harboured MRSA. The S. aureus isolates belonged to 16 clonal complexes (CC). MSSA isolates included three each for CC15, CC188, ST2867; two each for CC5, CC97, CC367 as well as one each for CC1, CC8, CC30, CC45, CC101, CC121, ST291/813 and CC1153. The staphylococcal cassette chromosome recombinase genes ccrA-1; ccrB-1 and the fusidic acid resistance gene (fusC) were present in two MSSA isolates (CC1 and CC8). The six MRSA isolates included CC5-MRSA-[VI+fusC] (n = 2); one each of CC5-MRSA-V; CC22-MRSA-IV (tst1+); CC80-MRSA-IV [pvl+] ("European CA-MRSA Clone") and CC97-MRSA-[V+fusC]. There is wide clonal diversity of S. aureus colonizers with associated high MRSA carriage among the HCWs. The presence of genetically stable MSSA isolates with the capability to transform into MRSA isolates is of concern.