Evolution, incidence, and susceptibility of bacterial bloodstream isolates from 519 bone marrow transplant patients

Bacteria remain an important cause of infection in bone marrow transplants. To examine shifts in the etiology and susceptibility of bacterial isolates from transplants, we reviewed the incidence and susceptibility of blood isolates during a 7-year period. The infection rate fell dramatically during this time. Gram-positive organisms were isolated more often than gram-negative organisms, but the trend is reversing. Streptococci surpassed staphylococci for 5 years as the leading pathogen. Increasing resistance to penicillin, ciprofloxacin, and imipenem was noted in Streptococcus species. With the exception of type 1 beta-lactamase-producing bacteria and Pseudomonas aeruginosa, gram-negative isolates remained overall susceptible to ceftazidime. Increased antibiotic prophylaxis coincided with the reduction in percentage of infected patients and increase in resistance to beta-lactam antibiotics. Mortality attributed to bacteremia was low except for infections caused by P. aeruginosa and the Enterobacter, Serratia, Citrobacter group. There was no mortality attributable to gram-positive organisms such as Staphylococcus aureus and viridans streptococci.