Time to positivity of blood cultures in patients Escherichia coli bacteraemia

Abstract number: 1733_440

Peralta G., Ceballos B., García-Mauriño L., Roiz M.P., Garrido J.C., De Benito I., Ansorena L., Sanchez M.B.

Objectives: Bacterial blood concentration is associated with prognosis of patients with bacteraemia caused by some microorganisms. However quantitative blood cultures are not performed in clinical practice. Time from the starting of incubation to a positive reading of blood cultures has been considered a surrogate marker of bacterial blood concentration and can be associated with prognosis. We analyze time to positivity (ttp) relationships with clinical parameters in patients with E. coli bacteraemia.

Methods: charts of all patients with monomicrobial E. coli bacteraemia attended at our hospital between January 1997 and December 2004 were identified by using the Microbiology laboratory database and reviewed. BacT/ALERT (bioMérieux) microbial detection system, was used for blood cultures and TTP detection. When multiple cultures were positive only the shortest TTP was selected for the analysis. Mann-Whiney U test was used for the comparison of median values, chi square test and Fisher`s exact test for the comparison of categorical data.

Results: during the study period we identified 567 cases of E. coli monomicrobial bacteraemia, with a mortality of 4.9%. Median (interquartile range) TTP was: 11.3 h (10.2 h–11.8 h). Significant correlation among TTP and the number of positive blood cultures was found (Spearman`s coefficient = -0.5, p < 0.0001). No differences in TTP were detected depending on the comorbidities, or nosocomial or postsurgical acquisition. However TTP was longer in patients treated with antibiotics when blood cultures were performed (21.2 h±27.4 h vs 14.01 h±12.06 h, p = 0.01), and shorter in patients with a non urinary origin of the bacteraemia (12.5±10.1 h vs 16±16.8 h, p < 0.0001), severe sepsis or shock (9.7±3.3 h vs 15.2±1.3 h, p < 0.0001), or patients who died (10.7±5.4 h vs 14.9±15 h, p = 0.006). ROC analysis revealed that a time to positivity of 10.4 h was associated with the best sensitivity and specificity for predicting dead (70% and 59%, respectively).

Conclusions: in patients with E. coli bacteraemia TTP is influenced by antibiotic treatment and has relationship with relevant clinical parameters as the origin of the bacteraemia, the presence of severe sepsis or shock and with the outcome. Its usefulness as a prognostic marker should be explored.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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