miércoles, 24 de octubre de 2012

Nasopharyngeal Bacterial Interactions in Children - - Emerging Infectious Disease journal - CDC

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Nasopharyngeal Bacterial Interactions in Children - - Emerging Infectious Disease journal - CDC


Nasopharyngeal Bacterial Interactions in Children

Qingfu Xu, Anthony Almudervar, Janet R. Casey, and Michael E. PichicheroComments to Author 
Author affiliations: Author affiliations: Rochester General Hospital Research Institute, Rochester, New York, USA (Q. Xu, M.E. Pichichero),; University of Rochester Medical Center, Rochester (A. Almudervar); Legacy Pediatrics, Rochester (J.R. Casey)
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Antimicrobial treatments and vaccines can alter bacterial interactions in the nasopharynx, thereby altering disease processes. To better understand these interactions, we examined colonization rates of 3 respiratory bacterial pathogens among 320 children when healthy and at onset of acute otitis media (AOM). Bacterial interactions were analyzed with a repeated measures logistic regression model. Among healthy children, Streptococcus pneumoniae and Moraxella catarrhalis were synergistically (positively) associated. Colonization with S. pneumoniae when healthy, but not at onset of AOM, was competitively (negatively) associated with Staphylococcus aureus. Among children with AOM, competitive associations were found between Haemophilus influenzae and S. pneumoniae and between H. influenzae and M. catarrhalis; rates of colonization with H. influenzae were higher. Bacterial interactions result in differing pathogen prevalence during periods of health and at onset of AOM. H. influenzae might become a more common cause of AOM among children who receive pneumococcal conjugate vaccine.

Respiratory bacterial infections, including pneumonia, acute exacerbations of bronchitis, acute sinusitis, and acute otitis media (AOM) among children and adults create major clinical concerns (1,2). The most common bacteria that cause upper respiratory tract infections are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis (2). The human nasopharynx is an ecologic reservoir of these and other bacteria. A broad variety of commensal bacteria and potential bacterial pathogens colonize the nasopharynx (3,4). Colonization of the nasopharynx is a first, and essential, step toward development of respiratory bacterial infections (3). Viruses can join the microbial mix as a prelude to secondary bacterial infections of the respiratory tract (57).
More information about microbial interactions in the nasopharynx is needed (8). These interactions can be altered by therapeutic (e.g., antimicrobial drug) and vaccine (e.g., pneumococcal conjugate vaccination) interventions, resulting in synergistic or competitive outcomes. Information about interactions of the major bacterial respiratory pathogens in the nasopharynx and the conditions conducive to progression to infection (e.g., concurrent viral upper respiratory infections) is limited.
Microbial species can interact synergistically to promote persistence of colonization (positive, or synergistic, association) or they can compete (negative, or competitive, association) (4,9). Interactions between bacteria can alter the composition of a microbial community and affect incidence of disease (4). Several studies have reported competitive associations between colonized S. pneumoniae and S. aureus in the nasopharynx of children, raising concerns that eradication of S. pneumoniae from the nasopharynx by the heptavalent pneumococcal conjugate vaccine (PCV7) might lead to increased S. aureus colonization and subsequent infections (1013). The introduction of the 13-valent pneumococcal conjugate vaccine will probably exacerbate this effect. Other variables that alter nasopharynx colonization patterns in children include age, gender, daycare attendance, history of having been breast-fed, environmental exposure to tobacco smoke, and otitis-prone condition (14,15).
Several recent reports have described interactions among the 3 major pathogens—S. pneumoniae, H. influenzae, and M. catarrhalis—in young children (8,10,11,16), but the results were contradictory (9). We investigated the interactions of these 3 pathogens in the nasopharynx of young children while healthy (healthy visits) and at onset of AOM (AOM visits). Our aims were to understand differences in nasopharynx colonization rates and bacterial interactions according to the child’s health status.

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