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The diagnostic utility of lytA real-time PCR in sputum and nasopharyngeal swabs for pneumococcal pneumonia and colonization in HIV-infected adults

Abstract number: P1847

Albrich W., Adrian P.V., van Niekerk N., Wong M., Khoosal M., Zhao P., Deatly A., Pride M., Sidhu M., Jansen K., Madhi S.A., Klugman K.P.

Objective: Pneumococcal aetiology is underestimated in patients with pneumonia as specimens are unavailable from lung tissue. We evaluated the diagnostic accuracy of real-time PCR in HIV-infected South African adults who either had X-ray confirmed pneumonia with pneumococci identified on at least one diagnostic specimen or were asymptomatic outpatients serving as controls.

Methods: lytA real-time PCR was applied on sputum and nasopharyngeal (NP) swabs of HIV-infected patients with X-ray confirmed pneumonia; and on NP swabs in HIV-infected asymptomatic controls. Pneumonia was assumed pneumococcal if Streptococcus pneumoniae was identified in blood culture, sputum culture or Gram stain or urinary Binax® Now.

Results: In 91 pneumonia patients with evidence of pneumococcal aetiology, sensitivity of lytA PCR in sputum was 92.3%, and 97.3% in patients who had pneumococci identified by sputum culture. lytA PCR from NP swabs was positive in 90 of 100 (90%) pneumonia patients and in 79/83 (95.2%) of those with a positive NP swab culture; in comparison, it was positive in 57 of 288 (19.8%; RR: 4.55, p < 0.001) asymptomatic controls, and in 23/29 (79.3%; RR: 1.20, p = 0.02) of controls with a positive NP swab culture. Among those with positive lytA PCR from NP swabs, log10 copies/ml were significantly higher in patients (mean: 6.86; 95% CI: 6.18, 6.52) than controls (mean: 4.02; 95% CI: 3.59, 4.45; p < 0.001). There were significant correlations between log10 of quantitative NP colony counts achieved by microbiological culture and of lytA PCR copies/ml (r: 0.7, p < 0.001). The AUC-ROC of lytA PCR for pneumococcal aetiology in pneumonia patients was 0.7 for both sputum and NP swab.

Conclusion: lytA real-time PCR from sputum and NP swab is highly sensitive for detection of both pneumococcal colonization and pneumonia in South African HIV-infected adults with a large burden of pneumococcal disease. Higher copy numbers correlate with clinical disease and higher bacterial loads as identified by standard microbiological tests. Quantitative lytA real-time PCR on sputum or NP swab may be a promising tool for diagnosis of pneumococcal pneumonia, both for clinical diagnostic and epidemiologic purposes.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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