Antimicrobial activity of 12 broad-spectrum agents tested against 270 nosocomial blood stream infection isolates caused by non-enteric gram-negative bacilli: occurrence of resistance, molecular epidemiology, and screening for metallo-enzymes.
A total of 270 recent nosocomial blood stream isolates of non-Enterobacteriaceae Gram-negative bacilli representing nearly 50 U.S. medical centers were characterized. The numbers of isolates of individual organisms were: Pseudomonas aeruginosa (n = 204), Acinetobacter spp. (n = 48), and Stenotrophomonas maltophilia (n = 18). MICs were determined using the broth microdilution susceptibility method with 12 antimicrobial agents: piperacillin, piperacillin/tazobactam, ceftriaxone, ceftazidime, cefepime, imipenem, ciprofloxacin, ofloxacin, amikacin, gentamicin, tobramycin, and trimethoprim/sulfamethoxazole. Based on current National Committee for Clinical Laboratory Standards breakpoints, rates of resistance to cefepime, ceftazidime, and imipenem were as follows: P. aeruginosa, 3, 9, and 5%; Acinetobacter spp., 2, 37, and 0%; and S. maltophilia, 88.7, 35.3, and 100%, respectively. Trimethoprim/sulfamethoxazole was the most active agent against S. maltophilia (100% susceptible). Twenty-eight isolates of P. aeruginosa that expressed high levels of resistance to ceftazidime (MIC, > 256 micrograms/mL) and imipenem (MIC, > 32 micrograms/mL) were examined for potential metallo-beta-lactamase production by polymerase chain reaction and were found to be negative. Molecular typing of P. aeruginosa isolates revealed many patient-unique strains, but also noted clustering of infections due to isolates of the same DNA type, suggesting possible nosocomial transmission in 9 of 14 medical centers. Given the resistance profile and pathogenic potential of these non-enteric Gram-negative bacilli, considerable effort should be exerted to develop and enforce infection control and antimicrobial utilization practices that will limit the spread of these organisms in the hospital environment.
Jones
R N
RN
Department of Pathology, University of Iowa College of Medicine, Iowa City 52242, USA.
Pfaller
M A
MA
Marshall
S A
SA
Hollis
R J
RJ
Wilke
W W
WW
D000150:Acinetobacter / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology*; D001426:Bacterial Proteins; D003428:Cross Infection / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D004352:Drug Resistance, Microbial; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D014974:Xanthomonas / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D001618:beta-Lactamases / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D001618:beta-Lactamases