Density Interactions Among Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus in the Nasopharynx of Young Peruvian Children

Abstract

Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus are commonly carried in the nasopharynx (NP) of young children, and have been speculated to interact with each other. Although earlier studies used cultures alone to assess these interactions, the addition of real-time quantitative polymerase chain reaction (qPCR) provides further insight into these interactions. We compared results of culture and qPCR for the detection of these three bacteria in 446 NP samples collected from 360 healthy young children in a prospective cohort study in the Peruvian Andes. Patterns of concurrent bacterial colonization were studied using repeated measures logistic regression models with generalized estimating equations. Spearman correlation coefficients were employed to assess correlations among bacterial densities. At a bacterial density <105 colony forming units (CFU)/ml measured by qPCR, culture detected significantly less carriers (P<0.0001) for all three pathogens, than at a bacterial density >105 CFU/ml. In addition, there was a positive association between S. pneumoniae and H. influenzae colonization measured by both culture (OR 3.11 – 3.17, p < 0.001) and qPCR (OR 1.95 – 1.97, p < 0.01). The densities of S. pneumoniae and H. influenzae, measured by qPCR, were positively correlated (correlation coefficient 0.32, p < 0.001). A negative association was found between the presence of S. pneumoniae and S. aureus in carriage with both culture (OR 0.45, p = 0.024) and qPCR (OR 0.61, p < 0.05). The impact of density on detection by culture and the observed density-related interactions support use of qPCR in additional studies to examine vaccine effects on diverse bacterial species.

Streptococcus pneumoniae Colonization Disrupts the Microbial Community within the Upper Respiratory Tract of Aging Mice

“…Old mice are unable to clear bacterial colonization as effectively as their young counterparts. We observed a number of interspecies interactions between S. pneumoniae and the existing mouse microbiome (e.g., Staphylococcus) that have been reported previously only in experimental models (16)(17)(18)(19)(20)(21)(22)(23)(24). In particular, Streptococcus interacted competitively with Staphylococcus and synergistically with Haemophilus.…”

“…Contrary to S. pneumoniae's interaction with Staphylococcus, Haemophilus facilitates S. pneumoniae's survival, as shown in previous studies using nasopharyngeal samples of children between 0 and 35 months of age (23). Although the exact mechanisms are unclear, it has been suggested that this phenomenon is related to the downregulation of pneumococcal autolysis and fratricide genes, as well as an increase in pneumococcal biofilm formation (19,23,24). As a result, there is decreased production of pneumococcal cell wall hydrolase and a subsequent decrease in pneumococcal lysis during the presence of Haemophilus influenzae.…”

“…It has been suggested that the hydrogen peroxide produced by S. pneumoniae inhibits a variety of competing organisms in the aerobic environment of the URT, including Staphylococcus (16,17,20). Contrary to S. pneumoniae's interaction with Staphylococcus, Haemophilus facilitates S. pneumoniae's survival, as shown in previous studies using nasopharyngeal samples of children between 0 and 35 months of age (23). Although the exact mechanisms are unclear, it has been suggested that this phenomenon is related to the downregulation of pneumococcal autolysis and fratricide genes, as well as an increase in pneumococcal biofilm formation (19,23,24).…”

“…For example, by sensing peptides released by neighboring bacterial species, S. pneumoniae stops replication, initiates a stress response (including the induction of competence), and becomes more adept at maintaining pneumococcal colonization in mouse models (52). Many clinical studies in children demonstrate that pneumococcal carriage is positively associated with Haemophilus influenzae carriage but negatively associated with the carriage of Staphylococcus aureus (17,23). Furthermore, adults who had more diverse nasal microbiota with a lower number of dominant species, such as Corynebacterium, were more likely to be natural S. pneumoniae carriers and more likely to become experimentally colonized by the pneumococcus (53).…”

Impaired Innate Mucosal Immunity in Aged Mice Permits Prolonged Streptococcus pneumoniae Colonization

“…Accelerating pneumococcal clearance is therefore also a goal of new vaccines (51); however, success of such prevention strategies in the elderly will require intact innate signaling, including epithelial responses, lymphoid tissue function, and phagocyte function. So far, there is no clear evidence of a longer duration of human carriage in the elderly compared to young adults, although this might be a consequence of scarce longitudinal colonization data for adults and the elderly or of the relatively low sensitivity of conventional detection methods (52)(53)(54).…”