title: Clinical and Microbiological Factors Associated with High Nasopharyngeal Pneumococcal Density in Patients with Pneumococcal Pneumonia.
abstract: BACKGROUND
  We aimed to study if certain clinical and/or microbiological factors are associated with a high nasopharyngeal (NP) density of Streptococcus pneumoniae in pneumococcal pneumonia. In addition, we aimed to study if a high NP pneumococcal density could be useful to detect severe pneumococcal pneumonia.
  
  
  METHODS
  Adult patients hospitalized for radiologically confirmed community-acquired pneumonia were included in a prospective study. NP aspirates were collected at admission and were subjected to quantitative PCR for pneumococcal DNA (Spn9802 DNA). Patients were considered to have pneumococcal etiology if S. pneumoniae was detected in blood culture and/or culture of respiratory secretions and/or urinary antigen test.
  
  
  RESULTS
  Of 166 included patients, 68 patients had pneumococcal DNA detected in NP aspirate. Pneumococcal etiology was noted in 57 patients (84%) with positive and 8 patients (8.2%) with negative test for pneumococcal DNA (p<0.0001). The median NP pneumococcal density of DNA positive patients with pneumococcal etiology was 6.83 log10 DNA copies/mL (range 1.79-9.50). In a multivariate analysis of patients with pneumococcal etiology, a high pneumococcal density was independently associated with severe pneumonia (Pneumonia Severity Index risk class IV-V), symptom duration ≥2 days prior to admission, and a medium/high serum immunoglobulin titer against the patient's own pneumococcal serotype. NP pneumococcal density was not associated with sex, age, smoking, co-morbidity, viral co-infection, pneumococcal serotype, or bacteremia. Severe pneumococcal pneumonia was noted in 28 study patients. When we studied the performance of PCR with different DNA cut-off levels for detection of severe pneumococcal pneumonia, we found sensitivities of 54-82% and positive predictive values of 37-56%, indicating suboptimal performance.
  
  
  CONCLUSIONS
  Pneumonia severity, symptom duration ≥2 days, and a medium/high serum immunoglobulin titer against the patient's own serotype were independently associated with a high NP pneumococcal density. NP pneumococcal density has limited value for detection of severe pneumococcal pneumonia.
authors.affiliation: Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden; Unit of Infectious Diseases, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Helena
authors.initials: H
authors.lastname: Alpkvist
authors.affiliation: Department of Infectious Diseases, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: Simon
authors.initials: S
authors.lastname: Athlin
authors.affiliation: Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden; Unit of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Pontus
authors.initials: P
authors.lastname: Nauclér
authors.affiliation: Section of Clinical Bacteriology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Herrmann
authors.affiliation: Section of Clinical Bacteriology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden; Department of Medical Microbiology and Parasitology, Faculty of Medicine, Benghazi University, Benghazi, Libya.
authors.forename: Guma
authors.initials: G
authors.lastname: Abdeldaim
authors.affiliation: Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Hans-Christian
authors.initials: HC
authors.lastname: Slotved
authors.affiliation: Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden; Unit of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Hedlund
authors.affiliation: Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden; Unit of Infectious Diseases, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden; Department of Infectious Diseases, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Strålin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology; D058491:Bacterial Load; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009305:Nasopharynx / Q000382:microbiology*; D011018:Pneumonia, Pneumococcal / Q000175:diagnosis / Q000276:immunology / Q000382:microbiology* / Q000401:mortality; D016133:Polymerase Chain Reaction; D012307:Risk Factors; D012680:Sensitivity and Specificity; D065288:Serogroup; D012720:Severity of Illness Index; D013296:Streptococcus pneumoniae / Q000145:classification / Q000235:genetics / Q000276:immunology; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial