Nasal carriage of Staphylococcus aureus among a healthy suburban population: genotypic diversity and frequency of pathogenicity genes

We analyzed the frequency and genotypic diversity of Staphylococcus aureus nasal carriage in a healthy suburban population in the state of New Jersey, United States of America, from 2011 to 2018, and the presence of virulence and antibiotic resistance genes. A total of 77 isolates were analyzed by phenotypic tests and PCR testing using genes coding for S. aureus 16S rRNA, methicillin resistant ( mecA ), vancomycin resistant ( vanA ), tetracycline resistant ( tetM ), macrolide resistant ( ermA ), Panton Valentine Leukocidin ( lukF ), arginine catabolic element (ACME), enterotoxin A ( sea ), staphylococcal protein A ( spa ), and toxic shock syndrome ( tst ). Percentage of nasal carriers of S. aureus was 11% and 3% for MRSA. Based upon spa gene typing, 41 different genotypes were found. The most common types were t008, t012, and t363. Frequencies in S. aureus for spa and ACME genes were 100% and 62%. However, percentages for sea, tst, and lukF genes were 38%, 27% and 22%, respectively. The ermA and tetM were detected in 57% and 13% of isolates. None of the mecA positive isolates showed the presence of vanA . Staphylococcal cassette chromosome (SCC) mec typing was performed using a multiplex PCR. SCC mec type IV was the most common among all MRSA isolates. In conclusion, healthy individuals carried a genetically diverse population of S. aureus with different virulence and antibiotic resistance genes in the nasal cavities representing an unrecognized and understudy human reservoir for antimicrobial resistance and genotypic diversity.