Clinical characterization of breakthrough bacteraemia: a survey of 392 episodes

Background. Few data are available on the clinical features of patients who develop breakthrough bacteraemia, understood as positive blood cultures despite appropriate antibiotic therapy. Objectives. To determine the clinical significance and outcome of a large series of breakthrough bacteraemia. Design. Retrospective analysis of a prospectively collected database. Setting. Two university-affiliated hospitals in Catalonia, Spain. Subjects. A total of 392 individuals who suffered an episode of breakthrough bacteraemia recorded between 1997 and 2002. Interventions. Demographic characteristics, underlying diseases, origin of infection, sources of infection, microorganisms isolated, McCabe and Jackson prognostic criteria, and mortality were analysed. Results. Breakthrough bacteraemia was detected in 392 of 6324 (6.1%) episodes of bacteraemia. Eighty per cent of episodes were nosocomial. The most frequent source of infection in breakthrough bacteraemia was endovascular (70%). Coagulase-negative staphylococci, Staphylococcus aureus, and Pseudomonas aeruginosa were the most significant microorganisms involved. Nosocomial acquisition together with selected sources (central venous catheter, endocarditis and other endovascular foci), underlying conditions (neutropenia, polytraumatism, allogenic bone marrow and kidney transplantation), and particular microbial aetiologies (S. aureus, P. aeruginosa and polymicrobial) were independently associated with increased risk for developing breakthrough bacteraemia. Crude mortality rate was greater in patients with breakthrough bacteraemia (16% vs. 12.3%; P < 0.05), and this condition was an independent predictor of death (OR 1.4, 95% CI, 1-1.9; P = 0.04). Conclusions. In view of a case of breakthrough bacteraemia it is mandatory to search for an endovascular focus. Empiric treatment should be directed to cover S. aureus, coagulase-negative staphylococci and nonfermentative Gram-negative bacilli. Breakthrough bacteraemia is an independent predictor of death.