title: Impact of preceding flu-like illness on the serotype distribution of pneumococcal pneumonia.
abstract: BACKGROUND
  Even though the pathogenicity and invasiveness of pneumococcus largely depend on capsular types, the impact of serotypes on post-viral pneumococcal pneumonia is unknown.
  
  
  RESULTS
  This study was performed to evaluate the impact of capsular serotypes on the development of pneumococcal pneumonia after preceding respiratory viral infections. Patients with a diagnosis of pneumococcal pneumonia were identified. Pneumonia patients were divided into two groups (post-viral pneumococcal pneumonia versus primary pneumococcal pneumonia), and then their pneumococcal serotypes were compared. Nine hundred and nineteen patients with pneumococcal pneumonia were identified during the study period, including 327 (35.6%) cases with post-viral pneumococcal pneumonia and 592 (64.4%) cases with primary pneumococcal pneumonia. Overall, serotypes 3 and 19A were the most prevalent, followed by serotypes 19F, 6A, and 11A/11E. Although relatively uncommon (33 cases, 3.6%), infrequently colonizing invasive serotypes (4, 5, 7F/7A, 8, 9V/9A, 12F, and 18C) were significantly associated with preceding respiratory viral infections (69.7%, P<0.01). Multivariate analysis revealed several statistically significant risk factors for post-viral pneumococcal pneumonia: immunodeficiency (OR 1.66; 95% CI, 1.10-2.53), chronic lung diseases (OR 1.43; 95% CI, 1.09-1.93) and ICI serotypes (OR 4.66; 95% CI, 2.07-10.47).
  
  
  CONCLUSIONS
  Infrequently colonizing invasive serotypes would be more likely to cause pneumococcal pneumonia after preceding respiratory viral illness, particularly in patients with immunodeficiency or chronic lung diseases.
authors.affiliation: Department of Pathology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America; Division of Infectious Diseases, Department of Internal Medicine, Korea University College of medicine, Seoul, Republic of Korea.
authors.forename: Joon Young
authors.initials: JY
authors.lastname: Song
authors.affiliation: Department of Pathology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America; Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Moon H
authors.initials: MH
authors.lastname: Nahm
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Korea University College of medicine, Seoul, Republic of Korea.
authors.forename: Hee Jin
authors.initials: HJ
authors.lastname: Cheong
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Korea University College of medicine, Seoul, Republic of Korea.
authors.forename: Woo Joo
authors.initials: WJ
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D005260:Female; D006801:Humans; D007223:Infant; D007251:Influenza, Human / Q000150:complications*; D008297:Male; D008875:Middle Aged; D011018:Pneumonia, Pneumococcal / Q000453:epidemiology* / Q000209:etiology*; D012307:Risk Factors; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000145:classification*; D014777:Virus Diseases / Q000150:complications*; D055815:Young Adult