Study on the nasal colonization of Staphylococcus aureus among healthcare workers in a hospital in Shaanxi Province / 中国热带医学

ABSTRACT

@#Abstract Objective　To determine the rate of nasal carriage Staphylococcus aureus among healthcare workers in Department of Infectious Diseases department of the First Affiliated Hospital of Xi'an Jiaotong University Hospital, and to perform characterization on isolated strains. Methods　A cross-sectional study was performed on 86 healthcare workers from February 2022 to June. Nasal swabs were collected from the healthcare workers, and S. aureus were identified after incubation. Antibiotic susceptibility, including chlorhexidine and mupirocin, was assessed by disk diffusion and minimal inhibitory concentration method. The PCR technique was used to detect the biocide resistance genes (qacAB, smr, lmrS mepA, and sepA), virulence genes (pvl, fnbA/fnbB, sea, seb, sec, sed, tst, eta, etb) and mecA gene. SCCmec typing and multilocus sequence typing was performed. For mupirocin-resistant strains, PCR amplification and sequencing were used to identify whether the strains had ileS gene mutations or carried resistant genes (mupA and mupB). Results　S. aureus was isolated from 37 of the 86 healthcare workers (43.02%) , including 13 methicillin-resistant Staphylococcus aureus (MRSA) strains. The strains showed low resistance rates to levofloxacin (2.70%, 1/37), chloramphenicol (8.11%, 3/37), tetracycline (8.11%, 3/37), gentamicin (10.81%, 4/37), and ciprofloxacin (10.81%, 4/37). A total of 17 strains were identified as multidrug-resistant strains. Four SCCmec types were identified in MRSA strains, with the type II being the most frequent (53.85%, 7/13), followed by type IV (30.77%, 4/13). ST59 (46.15%, 6/13) was the most frequent among MRSA strains, while ST5 (41.67%, 10/24) was the most frequent among methicillin-susceptible S. aureus (MSSA) strains. sea was the most frequent virulence gene (56.76%, 21/37). sepA and mepA were detected in all 37 isolates. One Staphylococcus aureus strain was not sensitive to chlorhexidine, two strains had the missense mutation V588F (G1762T) and showed low level resistance to mupirocin, and one strain carrying mupA gene was highly resistant to mupirocin. Conclusion　The nasal colonization rate of Staphylococcus aureus among healthcare worker in the investigated hospital was high, indicating a risk for nosocomial infections. Strengthened monitoring and decolonization treatment should be carried out to reduce these risks.