Antimicrobial susceptibility of bacteremic isolates from cancer patients with or without neutropenia at a medical center in southern Taiwan

Background: Few studies focus on comparison of antimicrobial susceptibility for bacteremic isolates in neutropenic and nonneutropenic cancer patients. The purpose of this study was to elucidate the antimicrobial susceptibility of bacteremic isolates from cancer patients. Methods: We collected bacterial isolates causing bloodstream infections in cancer patients at a tertiary care hospital from 2003 to 2005 and performed in vitro antimicrobial susceptibility of these pathogens by the disc diffusion method. Results: A total of 588 bacterial isolates were identified from 476 episodes of bloodstream infections in cancer patients. Major pathogens were Escherichia coli (22.4%), Klebsiella pneumoniae (17.6%), and Pseudomonas aeruginosa (14.1%) in neutropenic patients and E coli (13.3%), K pneumoniae (10.1%), and Staphylococcus aureus (9.7%) in nonneutropenic patients. Of S aureus, 55.8% were resistant to methicillin, and of coagulase-negative Staphylococcus 87.0%. Cefepime, cefpirome, piperacillin/tazobactam, meropenem, or imipenem in combination with or without an aminoglycoside, were active against more than 85% of gram-negative bacilli (GNB). Ceftazidime, piperacillin, or ciprofloxacin plus an aminoglycoside were also active against more than 85% of GNB. The susceptibility rate of GNB or gram-positive cocci to any agent was not different between the isolates from neutropenic and nonneutropenic patients, but more GNB isolates from the former were susceptible to imipenem or meropenem plus an aminoglycoside. Conclusion: GNB remained dominant among bacteremic isolates in cancer patients. Antimicrobial agents, especially aminoglycoside-containing combination regimens, as recommended by Infectious Diseases Society of Taiwan for febrile neutropenia, were active against more than 85% of GNB isolates.