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

Diagn Microbiol Infect Dis. 1997 Nov;29(3):187-92. doi: 10.1016/s0732-8893(97)81808-1.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter / drug effects
  • Acinetobacter / genetics
  • Acinetobacter / isolation & purification
  • Anti-Bacterial Agents / pharmacology*
  • Bacteremia / drug therapy*
  • Bacteremia / epidemiology
  • Bacteremia / microbiology*
  • Bacterial Proteins*
  • Cross Infection / drug therapy*
  • Cross Infection / epidemiology
  • Cross Infection / microbiology*
  • DNA, Bacterial / genetics
  • Drug Resistance, Microbial
  • Gram-Negative Bacteria / drug effects*
  • Gram-Negative Bacteria / genetics
  • Gram-Negative Bacteria / isolation & purification*
  • Gram-Negative Bacterial Infections / drug therapy*
  • Gram-Negative Bacterial Infections / epidemiology
  • Gram-Negative Bacterial Infections / microbiology*
  • Humans
  • Microbial Sensitivity Tests
  • Molecular Epidemiology
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / genetics
  • Pseudomonas aeruginosa / isolation & purification
  • Xanthomonas / drug effects
  • Xanthomonas / genetics
  • Xanthomonas / isolation & purification
  • beta-Lactamases / genetics

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • DNA, Bacterial
  • beta-Lactamases