Early detection of bacteria in bloodstream infections: implications for patient care.

Blood stream infections have a high mortality, up to 25%. Since quick adequate therapy reduces mortality, broad spectrum antibiotics are used as empirical therapy. However, this strategy may lead to problems such as selection of antibiotic resistant bacteria, higher risk of drug toxicity and the risk of not covering the causative micro-organism. Early identification of the causative micro-organism and rapid determination of the antibiotic susceptibility pattern will narrow down the antibiotic therapy and reduce the time that broad antibiotic therapy is given.

The objective of this randomised, blinded clinical trial is to evaluate the influence of a PCR-based diagnostic test for antibiotic susceptibility in bacteraemia patients.

All patients 18 years and older admitted to the Maastricht University Medical Center with grown blood cultures are eligible for inclusion. Exclusion criteria are: a blood culture containing streptococci, coagulase-negative staphylococci, anaerobes or multiple species or a positive blood culture in the previous 3 days.
Patients are randomised for antibiotic therapy according to either the rapid PCR-based method or the conventional method (conventional culture techniques).

Primary endpoint is reduction in time that a broad-spectrum or inappropriate antibiotic is used. Secondary outcomes are implementation of the antibiotic advice, length of hospital stay, adverse effects of antibiotic use, mortality and economic evaluation.

We hypothesize that earlier diagnosis in bloodstream infections results in earlier initiation or adaptation of the empirically started broad-spectrum antibiotics and may lead to an improved patient outcome, decrease in costs and reduction of selection of antibiotic-resistant bacteria.

1. At inclusion, baseline characteristics, signs of infection (lab results, X-rays, previous cultures), reason for taking a blood culture, previous infections and previous use of antibiotics will be recorded;

2. 9 hours after inclusion: reporting of results of the new methods;

3. 24 hours after inclusion: registration of signs of infection and reporting of the results of the conventional method;

4. At discharge or death of the patient: registration of antibiotics used during hospital stay, side-effects of antibiotics, infections during hospital stay and length of stay or cause of death.

In patients randomised for the intervention group, a new, rapid method for antibiotic susceptibility testing directly on positive blood cultures will be used. This method combines culture and PCR. The PCR is used to assess growth of bacteria in medium in the presence of an antibiotic. In this group, the results of this rapid method will be reported to the attending physician. In the control group, results of conventional methods (i.e. BD Phoenix (automated antibiotic susceptibility testing), E-test and disk diffusion) will be reported.