title: Detection of viral and bacterial pathogens in acute respiratory infections.
abstract: OBJECTIVE
  The role of bacteria in acute respiratory illnesses (ARI) of adults and interactions with viral infections is incompletely understood. This study tested the hypothesis that bacterial co-infection during ARI adds to airway inflammation and illness severity.
  
  
  METHODS
  Two groups of 97 specimens each were randomly selected from multiplex-PCR identified virus-positive and virus-negative nasal specimens obtained from adults with new onset ARI, and 40 control specimens were collected from healthy adults. All specimens were analyzed for Haemophilus influenzae(HI), Moraxella catarrhalis(MC) and Streptococcus pneumoniae(SP) by quantitative-PCR. General linear models tested for relationships between respiratory pathogens, biomarkers (nasal wash neutrophils and CXCL8), and ARI-severity.
  
  
  RESULTS
  Nasal specimens from adults with ARIs were more likely to contain bacteria (37% overall; HI = 28%, MC = 14%, SP = 7%) compared to specimens from healthy adults (5% overall; HI = 0%, MC = 2.5%, SP = 2.5%; p < 0.001). Among ARI specimens, bacteria were more likely to be detected among virus-negative specimens compared to virus-positive specimens (46% vs. 27%; p = 0.0046). The presence of bacteria was significantly associated with increased CXCL8 and neutrophils, but not increased symptoms.
  
  
  CONCLUSIONS
  Pathogenic bacteria were more often detected in virus-negative ARI, and also associated with increased inflammatory biomarkers. These findings suggest the possibility that bacteria may augment virus-induced ARI and contribute to airway inflammation.
authors.affiliation: Department of Family Medicine, University of Wisconsin-Madison, School of Medicine and Public Health, 1100 Delaplaine Ct., Madison, WI 53715, USA. Electronic address: cobasi@wisc.edu.
authors.forename: Chidi N
authors.initials: CN
authors.lastname: Obasi
authors.affiliation: Department of Family Medicine, University of Wisconsin-Madison, School of Medicine and Public Health, 1100 Delaplaine Ct., Madison, WI 53715, USA.
authors.forename: Bruce
authors.initials: B
authors.lastname: Barrett
authors.affiliation: Schools of Nursing, Medicine and Public Health, Research Design & Statistics Unit, University of Wisconsin-Madison, USA.
authors.forename: Roger
authors.initials: R
authors.lastname: Brown
authors.affiliation: School of Medicine, Departments of Pediatrics and Medicine, University of Wisconsin-Madison, USA.
authors.forename: Rose
authors.initials: R
authors.lastname: Vrtis
authors.affiliation: Department of Family Medicine, University of Wisconsin-Madison, School of Medicine and Public Health, 1100 Delaplaine Ct., Madison, WI 53715, USA.
authors.forename: Shari
authors.initials: S
authors.lastname: Barlow
authors.affiliation: Department of Medicine - Rheumatology, University of Wisconsin-Madison, School of Medicine and Public Health, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Muller
authors.affiliation: School of Medicine, Departments of Pediatrics and Medicine, University of Wisconsin-Madison, USA.
authors.forename: James
authors.initials: J
authors.lastname: Gern
mesh_terms: D000328:Adult; D001424:Bacterial Infections / Q000378:metabolism / Q000382:microbiology* / Q000821:virology; D015415:Biomarkers / Q000378:metabolism; D016009:Chi-Square Distribution; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007249:Inflammation; D016209:Interleukin-8 / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012141:Respiratory Tract Infections / Q000378:metabolism / Q000382:microbiology* / Q000821:virology*; D016896:Treatment Outcome; D014777:Virus Diseases / Q000378:metabolism / Q000382:microbiology / Q000821:virology*
chemical_list: D015415:Biomarkers; C508606:CXCL8 protein, human; D016209:Interleukin-8
keywords: Bacteria; Common cold; Inflammation; Upper respiratory infections