A clinical investigation on the prevalence of ceftazidime-resistant Klebsiella pneumoniae and Escherichia coli isolates

Sixteen thousand nine hundred and fifteen clinical isolates of Klebsiella pneumoniae and 23,568 clinical isolates of Escherichia coli were isolated during the period September 1994 through August 1995, and were subjected to susceptibility testing against ceftazidime (CAZ), aztreonam (AZT), latamoxef (LMOX), sulbactam/cefoperazone (SBT/CPZ), cefpirome (CPR), cefminox (CMNX), ceftizoxime (CZX), and piperacillin (PIPC). Forty one of the 16,915 K. pneumoniae strains (0.24%) were found to be resistant to CAZ. Among the 41 CAZ-resistant strains, 30 were isolated from 5 hospitals in Kanagawa, 5 were from a hospital in Shizuoka, 5 were from 2 hospitals in Tokyo, and 1 strain was from a hospital in Yamaguchi. All 41 of these strains also demonstrated high-level resistances to both AZT and PIPC, and a portion of these strains showed additional moderate- to low-level resistances to the remaining 5 agents. Of the E. coli isolates tested, 25 strains demonstrating CAZ- resistance were identified from 8 hospitals throughout Japan. These isolates also demonstrated high-level resistance against AZT and PIPC. However, in contrast to the CAZ-resistant K. pneumoniae strains, CAZ-resistant E. coli strains exhibited higher-levels of resistance to the remaining 5 agents. Finally, a disturbing trend noted in this study was that in some hospitals, CAZ-resistant strains were isolated repeatedly from patients who were hospitalized in the same ward, suggesting the presence of nosocomial outbreaks. Thus, the choice of appropriate antimicrobial agents based on timely and accurate antimicrobial susceptibility testing is thought to be critical for the containment of CAZ-resistant strains.