Impact of antibiotic resistance and of adequate empirical antibiotic treatment in the prognosis of patients with Escherichia coli bacteraemia.

Peralta G, Sánchez MB, Garrido JC, et al. J Antimicrob Chemother 2007;60:855–863.

Summary:

Peralta and colleagues performed a retrospective cohort study in an adult acute-care centre in Spain, exploring 663 patients with Escherichia coli bacteraemia. The investigators studied the impact of multi-drug resistant (MDR) E. coli bacteraemia with respect to the frequency of correct empiric antibiotic treatment and outcome. The purpose of this analysis was not simply to describe outcomes but also to identify variables predictive of survival.

E. coli is the most frequent Gram-negative organism causing bacteraemia. Such bacteraemia is a serious medical condition, which in this study was associated with an overall mortality of 5.4%.

In the multivariate analysis used by the investigators, variables with poor outcome were; age, the presence of severe sepsis or shock and a non-urinary origin of the bacteraemia. Moreover, after adjustment for other significant risk factors and confounders, the inadequacy of empiric antibiotic treatment was associated with increased mortality.

Finally, the authors detected an association between the number of antibiotics to which the isolated E. coli was resistant, the adequacy of empiric antibiotic therapy and mortality. When E. coli isolates were not resistant to antibiotics, the likelihood of initial antibiotic therapy being adequate was over 95% and mortality in this patient group was below 5%. When isolated E. coli demonstrated resistance to three or more antibiotics, the likelihood of initial empiric therapy being inadequate was over 30% and correspondingly, mortality rose to 13.8%.

The conclusions from this study are:

• The adequacy of empiric antibiotic treatment is an independent risk factor for mortality in patients with E. coli bacteraemia
• MDR E. coli bacteraemia has a worse prognosis, partly owing to a lower frequency of correct empiric treatment.

AIM core principles supported:

• Antibiotic choice: Empiric antibiotic regimens should be designed to cover the likely pathogens. The above Peralta study emphasises that getting it right first time is essential for better outcomes
• Resistance: The empiric antibiotic regimen should be based on likely susceptibility data. The present study by Peralta and colleagues certainly proves what we all believed to be true; the greater the resistance, the more likely it is that inadequate initial empiric therapy is initiated, and the greater the likelihood of an adverse outcome.

Learning points:

• Appropriate antibiotic therapy is associated with improved survival.