Colonization Density of the Upper Respiratory Tract as a Predictor of Pneumonia-Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Pneumocystis jirovecii.
Background.
There is limited information on the association between colonization density of upper respiratory tract colonizers and pathogen-specific pneumonia. We assessed this association for Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Pneumocystis jirovecii.


Methods.
In 7 low- and middle-income countries, nasopharyngeal/oropharyngeal swabs from children with severe pneumonia and age-frequency matched community controls were tested using quantitative polymerase chain reaction (PCR). Differences in median colonization density were evaluated using the Wilcoxon rank-sum test. Density cutoffs were determined using receiver operating characteristic curves. Cases with a pathogen identified from lung aspirate culture or PCR, pleural fluid culture or PCR, blood culture, and immunofluorescence for P. jirovecii defined microbiologically confirmed cases for the given pathogens.


Results.
Higher densities of H. influenzae were observed in both microbiologically confirmed cases and chest radiograph (CXR)-positive cases compared to controls. Staphylococcus aureus and P. jirovecii had higher densities in CXR-positive cases vs controls. A 5.9 log10 copies/mL density cutoff for H. influenzae yielded 86% sensitivity and 77% specificity for detecting microbiologically confirmed cases; however, densities overlapped between cases and controls and positive predictive values were poor (<3%). Informative density cutoffs were not found for S. aureus and M. catarrhalis, and a lack of confirmed case data limited the cutoff identification for P. jirovecii.


Conclusions.
There is evidence for an association between H. influenzae colonization density and H. influenzae-confirmed pneumonia in children; the association may be particularly informative in epidemiologic studies. Colonization densities of M. catarrhalis, S. aureus, and P. jirovecii are unlikely to be of diagnostic value in clinical settings.
['Park|Daniel E|DE|', 'Baggett|Henry C|HC|', 'Howie|Stephen R C|SRC|', 'Shi|Qiyuan|Q|', 'Watson|Nora L|NL|', 'Brooks|W Abdullah|WA|', 'Deloria Knoll|Maria|M|', 'Hammitt|Laura L|LL|', 'Kotloff|Karen L|KL|', 'Levine|Orin S|OS|', 'Madhi|Shabir A|SA|', 'Murdoch|David R|DR|', "O'Brien|Katherine L|KL|", 'Scott|J Anthony G|JAG|', 'Thea|Donald M|DM|', 'Ahmed|Dilruba|D|', 'Antonio|Martin|M|', 'Baillie|Vicky L|VL|', 'DeLuca|Andrea N|AN|', 'Driscoll|Amanda J|AJ|', 'Fu|Wei|W|', 'Gitahi|Caroline W|CW|', 'Olutunde|Emmanuel|E|', 'Higdon|Melissa M|MM|', 'Hossain|Lokman|L|', 'Karron|Ruth A|RA|', 'Maiga|Abdoul Aziz|AA|', 'Maloney|Susan A|SA|', 'Moore|David P|DP|', 'Morpeth|Susan C|SC|', 'Mwaba|John|J|', 'Mwenechanya|Musaku|M|', 'Prosperi|Christine|C|', 'Sylla|Mamadou|M|', 'Thamthitiwat|Somsak|S|', 'Zeger|Scott L|SL|', 'Feikin|Daniel R|DR|', '|||']
D002675:Child, Preschool D005260:Female D006192:Haemophilus Infections D006193:Haemophilus influenzae D006801:Humans D007223:Infant D008297:Male D001936:Moraxella catarrhalis D045828:Moraxellaceae Infections D009305:Nasopharynx D009960:Oropharynx D045363:Pneumocystis carinii D018410:Pneumonia, Bacterial D011020:Pneumonia, Pneumocystis D011023:Pneumonia, Staphylococcal D016133:Polymerase Chain Reaction D012372:ROC Curve D012141:Respiratory Tract Infections D013211:Staphylococcus aureus
colonization density pneumonia PERCH.