Complex Clonal Diversity of Nasal Colonization Among Community Personnel, Healthcare Workers, and Clinical Students in the Eastern Province, Saudi Arabia

Here, 210 healthy participants including community personnel (70), clinical students (68), and healthcare workers (HCWs) (72) from the eastern region of Saudi Arabia were studied. Sixty-three isolates were obtained from the nares of 37% of the community personnel and 26% of the clinical students and HCWs. Methicillin-resistant (MRSA) was found in 16% (10 isolates) of the 63 isolates; six were from HCWs. Molecular characterization revealed high clonal diversity among the isolates, with 19 different types, 12 clonal complexes (CCs), and seven sequence types (STs) detected. The most common strain type was USA900, CC15, and t084, seen in 11 methicillin-susceptible (MSSA) isolates. Moreover, three novel types in six isolates and one novel ST in two isolates were identified, most from HCWs. Interestingly, 29 isolates were A positive by PCR, whereas only 10 isolates were MRSA by disk diffusion (cefoxitin resistant). Of the 19 MSSA A-positive isolates, 16 were PBP2a negative, leaving three unique isolates from HCWs that were A and PBP2a positive yet cefoxitin susceptible. Our findings highlight the importance of phenotypically and genotypically characterizing strains isolated from healthy communities to monitor the risk of possible cross-transmission to hospitalized patients. The identified strains showed a clonal lineage relationship with previously reported and MRSA strains acquired from hospital settings.