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The in vitro activity of cefepime was compared versus that of 10 antimicrobial agents commonly used in the treatment of serious infections caused by common aerobic gram-negative bacteria: aztreonam, cefoperazone, ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, piperacillin, ticarcillin-clavulanic acid, and tobramycin. We tested 30 clinical isolates representing a cross section of Klebsiella and Enterobacter species and Pseudomonas aeruginosa collected at our tertiary-care university hospital. The most potent beta-lactams were imipenem and cefepime, which demonstrated significant activity against the majority of strains in all 3 genera of bacteria tested, as did ciprofloxacin and tobramycin. Ceftazidime was active against Pseudomonas aeruginosa but was less potent against Klebsiella and Enterobacter spp. Cefoperazone and ceftriaxone were less active than ceftazidime against Pseudomonas aeruginosa. Cefepime was found to be highly active against many resistant organisms that traditionally have been difficult to treat.

Objective: To report a pseudoepidemic of Pseudomonas aeruginosa infections discovered during an investigation of postoperative joint infections., Design: A retrospective review of case patients' hospital charts, operative reports, and laboratory data, as well as environmental culturing, polymerase chain reaction (PCR) ribotyping of outbreak isolates, and in vitro analysis of P aeruginosa growth characteristics., Setting: A 510-bed, university-affiliated adult tertiary care hospital., Results: Between October 1 and December 1, 1992, seven postsurgical joint infections were diagnosed, including four caused by P aeruginosa. A bottle of "sterile" saline used to process tissue specimens was found to be contaminated with P aeruginosa. Further investigation revealed that P aeruginosa had grown from seven additional tissue cultures, all of which had been processed with the contaminated saline. PCR ribotypes of the contaminant matched those of the clinical isolates. In vitro, P aeruginosa strains were viable in commercial nonbacteriostatic saline, but never caused visible turbidity. Six patients received antibiotics for their presumed infections; four patients had peripherally inserted central catheters placed, and one experienced severe anaphylactic reactions to several antibiotics., Conclusions: Pseudoepidemics due to common organisms are often difficult to detect, and delayed recognition can result in substantial morbidity. This outbreak investigation illustrates the potential for contamination of diluents in the microbiology laboratory and emphasizes the need for meticulous quality control.

The use of rapid, automated technologies for assessment of antimicrobial susceptibility and determination of minimum inhibitory concentrations has been evolving for over a decade. We compared the Vitek AutoMicrobic system and Bauer-Kirby disk diffusion with the National Committee for Clinical Laboratory Standards methods of serial plate agar dilution for qualitative and quantitative susceptibilities of 301 hospital isolates of Klebsiella spp., Enterobacter spp., and Pseudomonas aeruginosa. Antibiotics tested were aztreonam, cefoperazone, ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, piperacillin, ticarcillin-clavulanic acid, and tobramycin. Agar dilution and Bauer-Kirby results were more strongly correlated for all three genera than were the results for agar dilution and Vitek. If agar dilution is presumed to be the "gold standard," Bauer-Kirby disk diffusion had only half the number of false susceptibles as did the Vitek. Thus, the Vitek AutoMicrobic system seems to be somewhat less reliable for both qualitative and quantitative measurement of susceptibility and resistance than is Bauer-Kirby disk diffusion.

We studied the susceptibilities of 77 strains of Neisseria gonorrhoeae to four antibiotics: cefpodoxime, ceftriaxone, penicillin, and tetracycline. All strains were susceptible to ceftriaxone. Cefpodoxime MICs (range, 0.001 to 0.125 micrograms/ml) were parallel to and approximately four times those of ceftriaxone, and all strains will probably be considered susceptible to cefpodoxime. Disk diffusion zone diameters for cefpodoxime ranged from 35 to 57 mm. Of the strains, 32% were penicillin resistant and 51% were tetracycline resistant (MIC, greater than or equal to 2 micrograms/ml). Susceptibility measurements were consistent for disk diffusion zone diameter and MIC, with an overall agreement of 215 of 225 (96%) for ceftriaxone, penicillin, and tetracycline combined. On the basis of these in vitro data, cefpodoxime should be evaluated in the treatment of gonorrhea.