title: Nasopharyngeal bacterial burden and antibiotics: Influence on inflammatory markers and disease severity in infants with respiratory syncytial virus bronchiolitis.
abstract: OBJECTIVE
  Animal studies suggest that RSV increases nasopharyngeal (NP) bacterial colonization facilitating bacterial infections. We investigated the influence of antibiotic treatment and colonization with potentially pathogenic bacteria on inflammatory markers and disease severity in RSV-infected in infants.
  
  
  METHODS
  Healthy young infants hospitalized with RSV bronchiolitis (n = 136) and age-matched healthy controls (n = 23) were enrolled and NP samples cultured for potentially pathogenic bacteria including: Gram-positive bacteria (GPB): Staphylococcus aureus, Streptococcus pneumoniae, β-hemolytic Streptococcus; and Gram-negative bacteria (GNB): Moraxella catarrhalis and Haemophilus influenzae. Clinical parameters and plasma IL-8, IL-6 and TNF-α concentrations were compared according to the bacterial class and antibiotic treatment.
  
  
  RESULTS
  Antibiotic treatment decreased by 10-fold NP bacterial recovery. Eighty-one percent of RSV infants who did not receive antibiotics before sample collection were colonized with pathogenic bacteria. Overall, GNB were identified in 21% of patients versus 4% of controls who were mostly colonized with GPB. Additionally, in RSV patients NP white blood cell counts (p = 0.026), and blood neutrophils (p = 0.02) were higher in those colonized with potentially pathogenic bacteria versus respiratory flora. RSV patients colonized with GNB had higher plasma IL-8 (p = 0.01) and IL-6 (p < 0.01) concentrations than controls, and required longer duration of oxygen (p = 0.049).
  
  
  CONCLUSIONS
  Infants with RSV bronchiolitis colonized with potentially pathogenic bacteria had increased numbers of mucosal and systemic inflammatory cells. Specifically, colonization with GNB was associated with higher concentrations of proinflammatory cytokines and a trend towards increased disease severity.
authors.affiliation: Center for Vaccines and Immunity, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA. Electronic address: mcarmen1981@yahoo.com.
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Suárez-Arrabal
authors.affiliation: Center for Vaccines and Immunity, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Division of Critical Care Medicine, Nationwide Children's Hospital and The Ohio State University School of Medicine, Columbus, OH, USA. Electronic address: cfmella@texaschildrens.org.
authors.forename: Cesar
authors.initials: C
authors.lastname: Mella
authors.affiliation: Center for Vaccines and Immunity, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA.
authors.forename: Santiago M
authors.initials: SM
authors.lastname: Lopez
authors.affiliation: Center for Biostatistics, The Ohio State University, Columbus, OH, USA.
authors.forename: Nicole V
authors.initials: NV
authors.lastname: Brown
authors.affiliation: Division of Critical Care Medicine, Nationwide Children's Hospital and The Ohio State University School of Medicine, Columbus, OH, USA.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Hall
authors.affiliation: Department of Pathology, Nationwide Children's Hospital and The Ohio State University School of Medicine, Columbus, OH, USA.
authors.forename: Sue
authors.initials: S
authors.lastname: Hammond
authors.affiliation: Department of Radiology, Nationwide Children's Hospital and The Ohio State University School of Medicine, Columbus, OH, USA.
authors.forename: William
authors.initials: W
authors.lastname: Shiels
authors.affiliation: Section of Ambulatory Pediatrics, Nationwide Children's Hospital and The Ohio State University School of Medicine, Columbus, OH, USA.
authors.forename: Judith
authors.initials: J
authors.lastname: Groner
authors.affiliation: Department of Microbiology and Laboratory Medicine, Nationwide Children's Hospital and The Ohio State University School of Medicine, Columbus, OH, USA.
authors.forename: Mario
authors.initials: M
authors.lastname: Marcon
authors.affiliation: Center for Vaccines and Immunity, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Division of Infectious Diseases, Nationwide Children's Hospital and The Ohio State University School of Medicine, Columbus, OH, USA.
authors.forename: Octavio
authors.initials: O
authors.lastname: Ramilo
authors.affiliation: Center for Vaccines and Immunity, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Division of Infectious Diseases, Nationwide Children's Hospital and The Ohio State University School of Medicine, Columbus, OH, USA. Electronic address: Asuncion.Mejias@nationwidechildrens.org.
authors.forename: Asuncion
authors.initials: A
authors.lastname: Mejias
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D058491:Bacterial Load / Q000187:drug effects; D015415:Biomarkers; D001990:Bronchiolitis, Viral / Q000503:physiopathology* / Q000821:virology; D016207:Cytokines / Q000097:blood; D005260:Female; D006090:Gram-Negative Bacteria / Q000302:isolation & purification*; D006094:Gram-Positive Bacteria / Q000302:isolation & purification*; D006193:Haemophilus influenzae / Q000302:isolation & purification; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D008297:Male; D001936:Moraxella catarrhalis / Q000302:isolation & purification; D009305:Nasopharynx / Q000382:microbiology*; D011446:Prospective Studies; D018357:Respiratory Syncytial Virus Infections / Q000503:physiopathology* / Q000821:virology; D012720:Severity of Illness Index; D013211:Staphylococcus aureus / Q000302:isolation & purification; D013291:Streptococcus / Q000302:isolation & purification / Q000472:pathogenicity; D013296:Streptococcus pneumoniae / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D015415:Biomarkers; D016207:Cytokines
keywords: Antibiotics; Bronchiolitis; Disease severity; Gram-negative bacteria; Nasopharyngeal bacterial colonization; RSV