Increasing antimicrobial resistance in gram-negative bacilli isolated frompatients in intensive care units

Background: We investigated gram-negative bacilli from patients in intensiv e care units to determine whether antimicrobial resistance was increasing Methods: Minimal inhibitory concentrations were determined by broth microdi lution on 334 gram-negative bacilli collected in 1990, 1995, and 1998. Results: During the 3 study years, the types of gram-negative bacilli encou ntered in our intensive care units changed with proportional increases of P seudomonas sp and decreases of inducible enterics. Dramatic increases in re sistance for ceftazidime. cefotaxime, and piperacillin were paralleled betw een respiratory-tract isolates and inducible enterics. By 1998, ticarcillin was more active than piperacillin against most isolates except Escherichia coli and Klebsiella sp, and most isolates became more resistant to gentami cin and tobramycin. Conclusions: Continuous changes in the types of gram-negative bacilli and a ntimicrobial resistance complicate empirical selection of antimicrobials in the intensive care units. These complications will place more emphasis on communication and strategy formations among health care workers (nurses, ph ysicians, laboratorians, and pharmacists) in an effort to treat infections in a timely and effective manner.