title: Time to positivity in blood cultures of adults with Streptococcus pneumoniae bacteremia.
abstract: BACKGROUND
  previous studies have established that bacterial blood concentration is related with clinical outcome. Time to positivity of blood cultures (TTP) has relationship with bacterial blood concentration and could be related with prognosis. As there is scarce information about the usefulness of TTP, we study the relationship of TTP with clinical parameters in patients with Streptococcus pneumoniae bacteremia.
  
  
  METHODS
  TTP of all cases of Streptococcus pneumoniae bacteremia, detected between January 1995 and December 2004 using the BacT/Alert automated blood culture system in a teaching community hospital was analyzed. When multiple cultures were positive only the shortest TTP was selected for the analysis.
  
  
  RESULTS
  in the study period 105 patients with Streptococcus pneumoniae bacteremia were detected. Median TTP was 14.1 hours (range 1.2 h to 127 h). Immunosuppressed patients (n = 5), patients with confusion (n = 19), severe sepsis or shock at the time of blood culture extraction (n = 12), those with a diagnosis of meningitis (n = 7) and those admitted to the ICU (n = 14) had lower TTP. Patients with TTP in the first quartile were more frequently hospitalized, admitted to the ICU, had meningitis, a non-pneumonic origin of the bacteremia, and a higher number of positive blood cultures than patients with TTP in the fourth quartile. None of the patients with TTP in the 90th decile had any of these factors associated with shorter TTP, and eight out of ten patients with TTP in the 10th decile had at least one of these factors. The number of positive blood cultures had an inverse correlation with TTP, suggesting a relationship of TTP with bacterial blood concentration.
  
  
  CONCLUSIONS
  Our data support the relationship of TTP with several clinical parameters in patients with Streptococcus pneumoniae bacteremia, and its potential usefulness as a surrogate marker of outcome.
authors.affiliation: Internal Medicine Service, Sierrallana Hospital, Barrio de Ganzo s/n, 39120 Torrelavega, Cantabria, Spain. gpf@mundivia.es
authors.forename: Galo
authors.initials: G
authors.lastname: Peralta
authors.forename: María José
authors.initials: MJ
authors.lastname: Rodríguez-Lera
authors.forename: Jose Carlos
authors.initials: JC
authors.lastname: Garrido
authors.forename: Luis
authors.initials: L
authors.lastname: Ansorena
authors.forename: María Pía
authors.initials: MP
authors.lastname: Roiz
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000175:diagnosis* / Q000382:microbiology; D001431:Bacteriological Techniques; D001769:Blood / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D008586:Meningitis, Pneumococcal / Q000097:blood / Q000175:diagnosis; D008875:Middle Aged; D010403:Penicillin Resistance; D011008:Pneumococcal Infections / Q000097:blood / Q000175:diagnosis*; D011018:Pneumonia, Pneumococcal / Q000097:blood / Q000175:diagnosis; D011379:Prognosis; D012189:Retrospective Studies; D018805:Sepsis / Q000097:blood / Q000175:diagnosis; D013296:Streptococcus pneumoniae / Q000254:growth & development* / Q000302:isolation & purification; D013997:Time Factors