S.aureus bloodstream infection and time-to-positivity

Abstract number: P1175

Martin Y., Alava J.A., Unzaga M.J., Ezpeleta C., Busto C., Cisterna R.

Objective: The aim to this study is to asses if the time to positivity (TTP) in blood culture of S. aureus bacteraemia correlates with the source of infection and the outcome of the patient.

Methods: We performed a prospective, observational study involving patients who had S. aureus bacteraemia between November 2003 and July 2008. When multiple cultures were positive only the shortest TTP was selected for the analysis.

Results: A total of 461 episodes of S. aureus bacteraemia were reported from 347 patients with ages between 0–92 years (median age, 67 years). 329 were methicillin sensible S. aureus (MSSA) and 132 were methicillin resistant S. aureus (MRSA). The mean age of this last group was higher (P= 0.029). The source of infection was identified in 414 bacteraemias. The most frequent source of bloodstream infection was catheter related 102 (24.6%), primary bacteraemias 77 (18.6%), skin and soft tissues infection 63 (15.2%), respiratory 37 (8.9%), urinary tract 34 (8.2%), surgical wound 16 (3.9%) and 8 (1.9%) gastrointestinal, other sources of bacteraemias were 77 (18.6%). Catheter related bacteraemia was the most common source of infection in both cases MRSA (21.9%) and MSSA infection (25.7%).

The TTP was 13.18 h (range from 51 minutes to 30.58 hours). The median time of MSSA (12.78 h) was shorter than MRSA (15.02 h) although this difference was not significant (P = 0.08). The TTP was significantly shorter from patients with endocarditis (6.62 h) compared with the rest of sources (15.2 h) (P = 0.0001). However, in patients with catheter related infection compared with the rest of sources the TTP was shorter but not statistically significant (P = 0.064). If the TTP is divided into two groups, early TTP (<12 h), this group is associated with endocarditis (median time 5.2 h), catheter related (8.94 h), respiratory (8.11 h) and urinary (8 h). The overall mortality rate was 20.6%: MRSA 19.3% and MSSA 21.1%. The sources with higher mortality were gastrointestinal tract 50%, respiratory 48.6%, other bacteraemias named group 26%, primary 20.8% and catheter related 12.7%.

Conclusions: Patients in the group of MRSA bacteraemia are older than patients in MSSA group. Our data support the relationship of TTP with endocarditis and catheter related infection. Growth of S. aureus within 12 hours after the initiation of incubation may identify patients with a high likelihood of endocarditis, catheter infection and possible complications.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
Back to top