title: Detection of methicillin-resistant and methicillin-susceptible Staphylococcus aureus colonization of healthy military personnel by traditional culture, PCR, and mass spectrometry.
abstract: BACKGROUND
  Methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) Staphylococcus aureus colonization is associated with increased rates of infection. Rapid and reliable detection methods are needed to identify colonization of nares and extra-nare sites, particularly given recent reports of oropharynx-only colonization. Detection methods for MRSA/MSSA colonization include culture, PCR, and novel methods such as PCR/electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS).
  
  
  METHODS
  We evaluated 101 healthy military members for S. aureus colonization in the nares, oropharynx, axilla, and groin, using CHROMagar S. aureus medium and Xpert SA Nasal Complete PCR for MRSA/MSSA detection. The same subjects were screened in the nares, oropharynx, and groin using PCR/ESI-TOF-MS.
  
  
  RESULTS
  By culture, 3 subjects were MRSA-colonized (all oropharynx) and 34 subjects were MSSA-colonized (all 4 sites). PCR detected oropharyngeal MRSA in 2 subjects, which correlated with culture findings. By PCR, 47 subjects were MSSA-colonized (all 4 sites); however, 43 axillary samples were invalid, 39 of which were associated with deodorant/anti-perspirant use (93%, p < 0.01). By PCR/ESI-TOF-MS, 4 subjects were MRSA-colonized, 2 in the nares and 2 in the oropharynx; however, neither of these correlated with positive MRSA cultures. Twenty-eight subjects had MSSA by PCR/ESI-TOF-MS, and 41 were found to have possible MRSA (S. aureus with mecA and coagulase-negative Staphylococcus (CoNS)).
  
  
  CONCLUSIONS
  The overall 3% MRSA colonization rate is consistent with historical reports, but the oropharynx-only colonization supports more recent findings. In addition, the use of deodorant/anti-perspirant invalidated axillary PCR samples, limiting its utility. Defining MRSA positivity by PCR/ESI-TOF-MS is complicated by co-colonization of S. aureus with CoNS, which can also carry mecA.
authors: From the 1 San Antonio Military Medical Center, Fort Sam Houston , Texas.
authors: Ashley G
authors: AG
authors: Shaw
authors: Todd J
authors: TJ
authors: Vento
authors: Katrin
authors: K
authors: Mende
authors: Rachael E
authors: RE
authors: Kreft
authors: Garth D
authors: GD
authors: Ehrlich
authors: Joseph C
authors: JC
authors: Wenke
authors: Tracy
authors: T
authors: Spirk
authors: Michael L
authors: ML
authors: Landrum
authors: Wendy
authors: W
authors: Zera
authors: Kristelle A
authors: KA
authors: Cheatle
authors: Charles
authors: C
authors: Guymon
authors: Tatjana P
authors: TP
authors: Calvano
authors: Elizabeth A
authors: EA
authors: Rini
authors: Charla C
authors: CC
authors: Tully
authors: Miriam L
authors: ML
authors: Beckius
authors: Clinton K
authors: CK
authors: Murray
mesh_terms: D000293:Adolescent; D000328:Adult; D001431:Bacteriological Techniques / Q000379:methods*; D002353:Carrier State / Q000175:diagnosis* / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D013058:Mass Spectrometry / Q000379:methods*; D016106:Methicillin Resistance; D008889:Military Personnel; D016133:Polymerase Chain Reaction / Q000379:methods*; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D055815:Young Adult