Clinical importance of "breakthrough" bacteremia

Fifty-one episodes of bacteremia and a single episode of fungemia occurred during treatment with seemingly adequate doses of appropriate antibiotics. Clinical findings in these "breakthrough" bacteremias and fungemia were compared with those in 448 non-breakthrough episodes. Breakthrough was more likely to be caused by facultative or aerobic gram-negative rods (e.g., Enterobacteriaceae and Pseudomonas species) than by anaerobes. Of the underlying conditions examined, immunosuppressive doses of glucocorticosteroids, diabetes mellitus, and moderate renal failure were significantly more frequent in patients with breakthrough. A significant association was also observed between an intra-abdominal primary focus of infection (abscesses, biliary tract or bowel infections) and the occurrence of breakthrough. Mortality in breakthrough bacteremia was 61 percent compared with 40 percent in non-breakthrough episodes. The phenomenon of breakthrough bacteremia shows the potential limitations of antibiotic therapy alone.