Molecular Characterization of <i>Staphylococcus aureus</i> Isolates Associated with Nasal Colonization and Environmental Contamination in Academic Dental Clinics

Abstract

<b><i>Aim:</i></b> To determine the genetic makeup of methicillin-sensitive/methicillin-resistant <i>Staphylococcus aureus</i> (MSSA/MRSA) from nasal colonization and environmental contamination in dental clinics. <b><i>Materials and Methods:</i></b> Nasal swabs from students and health care workers and environmental swabs were obtained at two academic dental clinics in the United Arab Emirates. The StaphyType DNA microarray-based assay was used for molecular characterization. <b><i>Results:</i></b> Forty-eight <i>S. aureus</i> isolates were identified phenotypically (nasal: <i>n</i> = 43; environmental: <i>n</i> = 5), but 6 of these were assigned to <i>S. argenteus</i> by genotyping. These were CC_(argenteus)2596, CC_(arg)2250-MSSA, CC_(arg)2250-MSSA-(Panton Valentine leukocidin [PVL]+) (<i>n</i> = 2), and CC_(arg)2198-MSSA (<i>n</i> = 2). MRSA nasal colonization rate was 5.4% (n/<i>N</i> = 8/146) with the following strain affiliations: CC5-MRSA-[IV+<i>fus</i>+<i>ccrAB</i>], "Maltese Clone"; CC6-MRSA-IV, "WA MRSA-51"; CC22-MRSA-IV (PVL+/<i>tst+</i>); CC22-MRSA-[IV+<i>fus+ccrAA/(C)</i>]; and two each of CC5-MRSA-[VI+<i>fus</i>] and CC97-MRSA-[V/VT+<i>fus</i>]. The SCC-borne fusidic acid resistance (<i>fusC</i>) gene was detected in MRSA (<i>n</i> = 5) and MSSA (<i>n</i> = 1). Some MSSA strains, CC1-MSSA-[<i>fus</i>+<i>ccrAB1</i>] and ST1278-MSSA-[<i>ccrA1</i>], harbored recombinase genes. A CC30-MSSA harbored ACME locus/<i>arc</i>-genes, while ST1278-MSSA-[<i>ccrA1</i>] had an ACME-III element. Enterotoxin genes were commonly carried, but <i>tst-1</i> gene was found in only CC22, CC30, and CC34 strains, while <i>pvl</i> genes were identified in CC_(<i>arg</i>)2250 and CC22-MRSA-IV. Of the 51 noncoagulase staphylococci (CoNS) identified, 18 were <i>mecA</i> positive. <b><i>Conclusion:</i></b> The findings demonstrate the first report of rare strains (ST1278 MSSA, CC_(<i>arg</i>)2198, CC_(<i>arg</i>)2596, and PVL+CC_(<i>arg</i>)2250) in our region. Detection of MSSA with recombinase genes and ACME loci alongside <i>mecA</i>-positive CoNS is of clinical significance as this could provide a milieu for acquisition and transfer of SCC-elements, either with different ACME types, with <i>fusC</i> or the <i>mecA</i> gene resulting in conversion of MSSA into MRSA.