Nasopharyngeal co-colonization with Staphylococcus aureus and Streptococcus pneumoniae in children is bacterial genotype independent.

Bacterial interference between Staphylococcus aureus and Streptococcus pneumoniae in the nasopharynx has been observed during colonization, which might have important clinical implications for the widespread use of pneumococcal conjugate vaccine in young children. This study aimed to determine whether the capacity of Staph. aureus to compete with Strep. pneumoniae is dependent on bacterial genotype. Demographic and microbiological determinants of carriage of specific genotypes of Staph. aureus in children were also studied. Children (n=3198) were sampled in the nasopharynx to detect carriage of Staph. aureus, Strep. pneumoniae and Neisseria meningitidis. Staph. aureus genotypes and pneumococcal sero- and genotypes were determined. Age, gender, zip code, active smoking and co-colonization with N. meningitidis or Strep. pneumoniae, both vaccine- and non-vaccine types, were not associated with colonization by specific Staph. aureus genotypes. Based on the whole-genome typing data obtained, there was no obvious correlation between staphylococcal and pneumococcal genotypes during co-colonization. Passive smoking showed a significant association (P=0.003) with carriage of a specific Staph. aureus cluster. This study suggests that there are no major differences between Staph. aureus clones (with different disease-invoking potential) in their capacity to compete with Strep. pneumoniae subtypes. Further studies should demonstrate whether differences in bacterial interference are due to more subtle genetic changes.