Molecular epidemiology of the nasal colonization by methicillin-susceptible Staphylococcus aureus in Swiss children.
Nasal carriage of Staphylococcus aureus contributes to an increased risk of developing an infection with the same bacterial strain. Genetic regulatory elements and toxin-expressing genes are virulence factors associated with the pathogenic potential of S. aureus. We undertook an extensive molecular characterization of methicillin-susceptible S. aureus (MSSA) carried by children. MSSA were recovered from the nostrils of children. The presence of Panton-Valentine leukocidin (PVL), exfoliatins A and B (exfoA and exfoB), and the toxic-shock staphylococcal toxin (TSST-1) and agr group typing were determined by quantitative PCR. A multiple-locus variable-number of tandem repeat analysis (MLVA) assay was also performed for genotyping. Five hundred and seventy-two strains of MSSA were analysed. Overall, 30% were positive for toxin-expressing genes: 29% contained one toxin and 1.6% two toxins. The most commonly detected toxin gene was tst, which was present in 145 (25%) strains. The TSST-1 gene was significantly associated with the agr group 3 (OR 56.8, 95% CI 32.0-100.8). MLVA analysis revealed a large diversity of genetic content and no clonal relationship was demonstrated among the analysed MSSA strains. Multilocus sequence typing confirmed this observation of diversity and identified ST45 as a frequent colonizer. This broad diversity in MSSA carriage strains suggests a limited selection pressure in our geographical area.
Department of Paediatrics, University of Geneva Hospitals, Geneva, Switzerland.
C
C
Mégevand
A
A
Gervaix
U
U
Heininger
C
C
Berger
C
C
Aebi
B
B
Vaudaux
C
C
Kind
H-P
HP
Gnehm
M
M
Hitzler
G
G
Renzi
J
J
Schrenzel
P
P
François
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001427:Bacterial Toxins / Q000235:genetics; D015373:Bacterial Typing Techniques; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D008297:Male; D008712:Methicillin / Q000494:pharmacology; D018598:Minisatellite Repeats; D017720:Molecular Epidemiology; D058889:Molecular Typing; D009666:Nose / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D013557:Switzerland / Q000453:epidemiology; D037521:Virulence Factors / Q000235:genetics
D000900:Anti-Bacterial Agents; D001427:Bacterial Toxins; D037521:Virulence Factors; D008712:Methicillin