title: Effect of antimicrobial use on pneumococcal diagnostic tests in elderly patients with community-acquired pneumonia.
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.
authors.affiliation: Department of Vaccination and Immune Protection, National Institute for Health and Welfare (THL), P.O. Box 310, 90101, Oulu, Finland, annika.saukkoriipi@thl.fi.
authors.forename: A
authors.initials: A
authors.lastname: Saukkoriipi
authors.forename: A A
authors.initials: AA
authors.lastname: Palmu
authors.forename: J
authors.initials: J
authors.lastname: Jokinen
authors.forename: V
authors.initials: V
authors.lastname: Verlant
authors.forename: W P
authors.initials: WP
authors.lastname: Hausdorff
authors.forename: T M
authors.initials: TM
authors.lastname: Kilpi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000652:urine; D017714:Community-Acquired Infections / Q000175:diagnosis*; D003955:Diagnostic Tests, Routine; D005260:Female; D006801:Humans; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D011018:Pneumonia, Pneumococcal / Q000175:diagnosis*; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000302:isolation & purification; D016482:Urinalysis
chemical_list: D000900:Anti-Bacterial Agents; D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial