Comparison of the effect of antibiotic treatment on the possibility of diagnosing invasive pneumococcal disease by culture or molecular methods: a prospective, observational study of children and adolescents with proven pneumococcal infection.

BACKGROUND: Detection of Streptococcus pneumoniae in culture specimens in invasive pneumococcal disease (IPD) may be hampered by antibiotic treatment administered before hospital admission. Realtime polymerase chain reaction (RT-PCR) assays do not require viable bacteria and are therefore less influenced by antimicrobial therapy. It is not known how long results of culture or molecular tests remain positive after antibiotic therapy is begun.
OBJECTIVE: The goal of the current study was to assess, in a pediatric population with a diagnosis of IPD confirmed by laboratory tests (culture and/or RT-PCR assay), the relationship between use of antibiotic therapy before hospital admission and the result of diagnostic methods (culture or molecular techniques) after admission.
METHODS: This prospective, observational study was conducted from April 2006 through March 2009. All children and adolescents aged 0 to 16 years, admitted to the hospital with a diagnosis of IPD confirmed by culture and/or molecular methods, were included in the study. Previous antibiotic treatment (drug, duration of therapy) was recorded. Primers and probes designed from the pneumococcal autolysin gene (lytA) were used in an RT-PCR assay for detection of S pneumoniae. Antibiotic tolerability, permanent sequelae (after a 6-month follow-up), and deaths were recorded.
RESULTS: Eighty-three patients (50 males, 33 females; 80 white, 3 Asian; mean age, 4.6 years; median age, 4.0 years; age range, 10 days-16 years) were included in the study. Fifty-four patients presented with pneumonia, 26 with meningitis/sepsis (meningitis, 19; sepsis, 7), and 3 with arthritis. Results of RT-PCR assays were positive in all 83 patients (100.0%), and 28 of the 83 patients (33.7%) also had culture-positive findings. Forty-two of the 83 patients (50.6%) had received antibiotic treatment before hospital admission, and 41 (49.4%) had not received antibiotics. Results of cultures were positive in 9 of the 42 patients with IPD (21.4%) who had received antibiotic treatment and in 19 of the 41 patients with IPD (46.3%) who had not received antibiotics (odds ratio, 3.2; 95% CI, 1.1-9.3; P = 0.03). Molecular methods appeared more sensitive than culture in any type of disease studied but particularly in patients with pneumonia, in whom the difference was statistically significant (P = 0.043). The mean length of antibiotic therapy was 1.4 days (median, 1 day; SD, 0.53 day; range, 1-2 days) for culture-confirmed cases and 4.5 days (median, 4 days; SD, 3.08 days; range, 1-15 days) for cases confirmed by RT-PCR assay (P = 0.002). No adverse reactions to the antibiotics used during home or hospital treatment were found. Two patients with meningitis suffered permanent, severe neurologic sequelae, and 1 girl died of sepsis 3 days after hospital admission. No permanent sequelae were recorded in patients with pneumonia or arthritis.
CONCLUSION: In these children and adolescents with IPD, the molecular methods used appeared to be more sensitive than culture in any IPD patient, with a higher statistical significance in patients previously treated with antibiotics and in patients with pneumonia.