Effect of antimicrobial use on pneumococcal diagnostic tests in elderly patients with community-acquired pneumonia
A Saukkoriipi1, A A Palmu, J Jokinen
1Department of Vaccination and Immune Protection, National Institute for Health and Welfare (THL), P.O. Box 310, 90101, Oulu, Finland, annika.saukkoriipi@thl.fi.
Abstract:
Antimicrobial treatment decreases bacterial culture yields. We assessed the impact of antimicrobial treatment on pneumococcal assays in a prospective study of community-acquired pneumonia (CAP) in the elderly. We enrolled 323 cases aged ≥65 years with radiologically confirmed CAP and collected detailed data on antimicrobial exposure and pneumococcal assays on various samples. Complete antimicrobial use data were available for 303 (94%) cases; 61% had no antimicrobial exposure, 19% had received antibiotics at the acute visit only, and 20% within 2 weeks before the acute visit (15% ongoing and 5 % completed treatment). Ongoing use before the visit reduced pneumococcal detection by culture (nasopharyngeal swab 2 vs. 16% in the unexposed; high-quality sputum 0 vs. 25%) and sputum lytA polymerase chain reaction (PCR) (0 vs. 25%). Urine antigen test and serology were not affected. Among those who had received antibiotics only at the acute visit before study sampling, serology (29 vs. 15%), urine antigen (19 vs. 8%), and blood culture (9 vs. 2%) were more often positive than among the unexposed. Antimicrobial exposure before the visit reduced both culture and PCR-based detection. Patients given antibiotics at the visit had higher proportions of positive blood culture, serology, and urine antigen tests, suggesting higher pneumococcal CAP prevalence.
Insights
Antimicrobial treatment significantly reduces pneumococcal detection using culture and PCR methods. However, urine antigen tests and serology remain unaffected, while early antibiotic use may increase positive results in other tests.
Area of Science:
- Infectious Diseases
- Microbiology
- Clinical Diagnostics
Background:
- Community-acquired pneumonia (CAP) is a significant health concern in the elderly.
- Accurate diagnosis of bacterial pneumonia, particularly pneumococcal pneumonia, is crucial for effective treatment.
- Antimicrobial therapy can impact the yield of diagnostic tests for bacterial infections.
Purpose of the Study:
- To evaluate the effect of antimicrobial treatment on the detection of Streptococcus pneumoniae in elderly patients with CAP.
- To compare the performance of different diagnostic assays (culture, PCR, urine antigen, serology) under various antimicrobial exposure scenarios.
Main Methods:
- Prospective study of 323 elderly patients (≥65 years) with radiologically confirmed CAP.
- Collection of detailed data on antimicrobial exposure (timing and duration).
- Performance assessment of pneumococcal assays on nasopharyngeal swabs, sputum, blood, urine, and serum samples.
Main Results:
- Ongoing antimicrobial use before the study visit reduced pneumococcal detection by nasopharyngeal swab culture and sputum PCR.
- Urine antigen tests and serology were not significantly affected by prior antimicrobial exposure.
- Antibiotic administration at the acute visit increased positive results for serology, urine antigen, and blood culture compared to unexposed patients.
Conclusions:
- Antimicrobial exposure prior to diagnostic sampling negatively impacts culture-based and PCR-based detection of pneumococcus.
- Urine antigen tests and serology appear more robust in the presence of recent antibiotic use.
- Findings suggest that antibiotic administration at the time of presentation may be associated with a higher prevalence of pneumococcal CAP.
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