Pneumococcal colonisation density: a new marker for disease severity in HIV-infected adults with pneumonia

BMJ Open. 2014 Aug 11;4(8):e005953. doi: 10.1136/bmjopen-2014-005953.

Abstract

Objective: A high genomic load of Pneumococcus from blood or cerebrospinal fluid has been associated with increased mortality. We aimed to analyse whether nasopharyngeal colonisation density in HIV-infected patients with community-acquired pneumonia (CAP) is associated with markers of disease severity or poor outcome.

Methods: Quantitative lytA real-time PCR was performed on nasopharyngeal swabs in HIV-infected South African adults hospitalised for acute CAP at Chris Hani Baragwanath Hospital, Soweto, South Africa. Pneumonia aetiology was considered pneumococcal if any sputum culture or Gram stain, urinary pneumococcal C-polysaccharide-based antigen, blood culture or whole blood lytA real-time PCR revealed pneumococci.

Results: There was a moderate correlation between the mean nasopharyngeal colonisation densities and increasing CURB65 scores among all-cause patients with pneumonia (Spearman correlation coefficient r=0.15, p=0.06) or with the Pitt bacteraemia score among patients with pneumococcal bacteraemia (p=0.63). In patients with pneumococcal pneumonia, nasopharyngeal pneumococcal colonisation density was higher among non-survivors than survivors (7.7 vs 6.1 log10 copies/mL, respectively, p=0.02) and among those who had pneumococci identified from blood cultures and/or by whole blood lytA real-time PCR than those with non-bacteraemic pneumococcal pneumonia (6.6 vs 5.6 log10 copies/mL, p=0.03). Nasopharyngeal colonisation density correlated positively with the biomarkers procalcitonin (Spearman correlation coefficient r=0.37, p<0.0001), proadrenomedullin (r=0.39, p=0.008) and copeptin (r=0.30, p=0.01).

Conclusions: In addition to its previously reported role as a diagnostic tool for pneumococcal pneumonia, quantitative nasopharyngeal colonisation density also correlates with mortality and prognostic biomarkers. It may also be useful as a severity marker for pneumococcal pneumonia in HIV-infected adults.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Adrenomedullin / blood
  • Adult
  • Bacteremia / microbiology
  • Biomarkers / blood
  • Calcitonin / blood
  • Calcitonin Gene-Related Peptide
  • Community-Acquired Infections / complications
  • Community-Acquired Infections / microbiology
  • HIV Infections / complications*
  • Hospitalization
  • Humans
  • Nasopharynx / microbiology*
  • Pneumonia
  • Pneumonia, Pneumococcal / complications
  • Pneumonia, Pneumococcal / microbiology*
  • Protein Precursors / blood
  • Real-Time Polymerase Chain Reaction
  • Severity of Illness Index*
  • South Africa
  • Streptococcus pneumoniae / growth & development*

Substances

  • Biomarkers
  • CALCA protein, human
  • Protein Precursors
  • proadrenomedullin
  • Adrenomedullin
  • Calcitonin
  • Calcitonin Gene-Related Peptide