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Throat swabs are necessary to reliably detect carriers of Staphylococcus aureus

Abstract number: 1732_15

Mertz D., Frei R., Jaussi B., Flückiger U., Widmer A.

Background: The anterior nares are considered to be the primary colonisation site of Staphylococcus aureus (S. aureus) and approximately 30% of healthy people carry the bacteria in their anterior nares. However, recent studies indicate that the throat may be an additional important site of colonisation (Nilsson P. J Clin Microbiol 2006). Most screening programmes for S. aureus including methicillin-resistant S. aureus (MRSA) require a swab from the nose only, and a swab of the throat is not considered as standard.

Objectives: To determine the frequency of positive S. aureus cultures with positive samples from the throat and negative from the nares.

Methods: Specimens were obtained with a sterile polyester fiber-tipped swab moistened with sterile saline from the anterior nares (5 rotations in each anterior nostril), the posterior wall of the pharynx, and the soft palate. Swabs were transported to the laboratory in a transport tube (M40 Transystem, Copan, Brescia, Italy) and put in selective enrichment broth (Chapman broth containing brain heart infusion broth with 6% NaCl, Biomedics, Madrid, Spain).

Results: A total of 905 individuals were screened for S. aureus between 2000 and 2005. Complete data were unavailable from 54 individuals who were excluded. Overall, S. aureus was isolated in 386/851 (45.4%) individuals from any site.

Screening resultsNo. of individuals% of overall positive
NaresThroat
pospos19650.8%
posneg11930.8%
negpos7118.4%
  386100%
negneg465 

Conclusion: Limiting S. aureus screening to the nares fails to identify 18.4% of carriers. Additional cost can be avoided by pooling the specimens while maintaining the higher sensitivity. Therefore, optimal screening for S. aureus should include swabs from both the nares and the throat. This may be even more important if screening is focused on MRSA carriage.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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