Polyclonal bacteremia due to gram-negative rods

The frequency of, risk factors for, and outcome of polyclonal gram-negative bacteremia are still unknown. We investigated them in a prospective cohort study of patients for whom a blood culture yielded greater than or equal t o1 species of gram-negative aerobic rod. For each patient, pulsed field gel electrophoresis (PFGE) was performed on 4 colonies of each morphologic typ e. Episodes of bacteremia were considered polyclonal if caused by >1 PFGE t ype of the same species. Ten (6.5%) of 153 investigated patients had polycl onal bacteremia. Bacteremia due to nonfermenting rods was the single signif icant risk factor for polyclonal bacteremia. Complications were equally fre quent in all patient groups. However, patients with polyclonal bacteremia r eceived more extensive antibiotic therapy than did patients with monoclonal bacteremia. Nearly 20% of episodes of bacteremia due to nonfermenting rods were polyclonal, but it remains unclear why nonfermenting rods were more l ikely to cause polyclonal bacteremia than were other gram-negative rods.