Objective: To assess the prevalence and determinants of colonisation with S. aureus and S. pneumoniae in HIV infected adult persons compared to healthy controls and to determine if bacterial interference between S. aureus and S. pneumoniae plays a role in HIV infected adults.
Methods: Between March 2007 and July 2007 248 HIV infected persons and 239 HIV negative controls were included in this cross-sectional, case-controlled study. A questionnaire was filed in both groups with potential determinants of S. aureus and S. pneumoniae carriage. Two nasal swabs were obtained with one week interval, to determine S. aureus carrier state. One nasopharyngeal swab was taken to determine S. pneumoniae carriership. All the swabs were done according standard operating procedures. SPSS 12.0 was used for statistical analysis.
Results: Persistent carrier rates (both nasal cultures positive) for S. aureus were comparable for both groups (19% HIV cases, 18% controls, p=0.670). Carriage with S. pneumoniae was found in only 4 cases in each group (p=0.953). No interference between S. aureus and S. pneumoniae and no association between carriage with both bacteria and HAART and HIV viral load was demonstrated. Increasing CD4 cell counts by 100 cells/μl showed to have significant association with persistent S. aureus carriage (p=0.004, OR 1.243, 95% CI 1.073-1,441).
Conclusion: In contrast to earlier non-controlled observational studies, no significant differences were found in the carrier rates of S. aureus and S. pneumoniae between HIV infected persons and healthy controls. Increasing CD4 cell count was the only determinant associated with increased persistent carriage rates with S. aureus. None of the other previous stated determinants of carriage for either bacteria were associated with carriage in this study. Furthermore, no evidence for bacterial interference between the two bacteria could be demonstrated.