Correlation between in vitro bacterial growth velocity of blood of patients with clinical parameters and prognosis in patients with Escherichia coli bacteremia

Abstract

To identify the clinical and laboratory parameters correlating with speed of bacterial growth in culture and independent risk factors of in-hospital mortality in patients with Escherichia coli bacteremia. This retrospective study was conducted at Beijing University Third Hospital. The medical records and microbiological database of the patients diagnosed as Escherichia coli bacteremia between January 2007 and December 2009 were collected. The parameter of time to positivity (TTP) was used to be a surrogate marker of bacterial growth. Univariate analysis was used to identify relationship between clinical parameters and the speed of bacterial growth. Logistic multivariate analysis was used to identify risk factors of in-hospital mortality. The medical records of 112 patients during the study period were collected, 25 patients died during hospital stay, the overall in-hospital mortality rate was 22.3%. Univariate analysis indicated the rapid-growth (TTP≤7 hours) group (n=20) had higher incidence of neutropenia (40.0% vs. 15.2%), higher incidence of primary bacteremia (40.0% vs. 18.5%) and higher in-hospital mortality rate (45.0% vs. 17.4%) than those with slow bacterial growth (TTP>7 hours) group (n =92, all P<0.05). The death group (n=25) was found to have a higher incidence of TTP≤7 hours (36.0% vs. 12.6%), higher incidence of active malignancies (44.0% vs. 24.1%), higher incidence of neutropenia (36.0% vs. 14.9%), higher rate of isolation of extended spectrum β lactamases (ESBL)-producing strains (48.0% vs. 24.1%) than the survival group (n=87, all P<0.05). Logistic multivariate analysis suggested the significant predictors of in-hospital mortality included TTP≤7 hours [odds ratio (OR)=3.412, 95% confidence interval (95% CI)=1.1819.856, P=0.023], ESBL-producing strains (OR=2.545, 95% CI=0.9776.625, P=0.056). In vitro Escherichia coli growth speed in the blood culture correlates with the incidence of neutropenia and primary bacteremia, and TTP≤7 hours and ESBL-producing strains may be the strong, independent risk factors of a worse prognosis in patients with Escherichia coli bacteremia.