During 1997-1999, a total of 70,067 isolates (6631 Pseudomonas aeruginosa isolates) were analyzed in the SENTRY program by geographic region and body site of infection. The respiratory tract was the most common source of P. aeruginosa. P. aeruginosa isolation rates increased during the study interval. Europe was the only region to show a significant decline in beta-lactam and aminoglycoside susceptibility rates. There was a reduction in the rates of susceptibility of Canadian isolates to imipenem and of Latin American isolates to meropenem. A total of 218 multidrug-resistant P. aeruginosa isolates (MDR-PSA; resistant to piperacillin, ceftazidime, imipenem, and gentamicin) were observed; MDR-PSA occurrence rates (percentages of all isolates) ranged from 8.2% (Latin America) to 0.9% (Canada). No antimicrobial inhibited >50% of MDR-PSA strains. Molecular characterization of selected, generally resistant strains was performed. Isolates showing unique ribogroups were found in Europe, Latin America, and the United States, but clonal spread was documented in several medical centers.

The evolution of drug resistance has a profound impact on human health. Candida glabrata is a leading human fungal pathogen that can rapidly evolve resistance to echinocandins, which target cell wall biosynthesis and are front-line therapeutics for Candida infections. Here, we provide the first global analysis of mutations accompanying the evolution of fungal drug resistance in a human host utilizing a series of C. glabrata isolates that evolved echinocandin resistance in a patient treated with the echinocandin caspofungin for recurring bloodstream candidemia. Whole genome sequencing identified a mutation in the drug target, FKS2, accompanying a major resistance increase, and 8 additional non-synonymous mutations. The FKS2-T1987C mutation was sufficient for echinocandin resistance, and associated with a fitness cost that was mitigated with further evolution, observed in vitro and in a murine model of systemic candidemia. A CDC6-A511G(K171E) mutation acquired before FKS2-T1987C(S663P), conferred a small resistance increase. Elevated dosage of CDC55, which acquired a C463T(P155S) mutation after FKS2-T1987C(S663P), ameliorated fitness. To discover strategies to abrogate echinocandin resistance, we focused on the molecular chaperone Hsp90 and downstream effector calcineurin. Genetic or pharmacological compromise of Hsp90 or calcineurin function reduced basal tolerance and resistance. Hsp90 and calcineurin were required for caspofungin-dependent FKS2 induction, providing a mechanism governing echinocandin resistance. A mitochondrial respiration-defective petite mutant in the series revealed that the petite phenotype does not confer echinocandin resistance, but renders strains refractory to synergy between echinocandins and Hsp90 or calcineurin inhibitors. The kidneys of mice infected with the petite mutant were sterile, while those infected with the HSP90-repressible strain had reduced fungal burden. We provide the first global view of mutations accompanying the evolution of fungal drug resistance in a human host, implicate the premier compensatory mutation mitigating the cost of echinocandin resistance, and suggest a new mechanism of echinocandin resistance with broad therapeutic potential.

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Interpretive agreements among the results of fluconazole broth microdilution tests, Etests, and disk diffusion tests were documented by evaluating 495 Candida spp. Microdilution reference test results were in agreement with 96% of the Etest results; most discrepancies were minor differences. Fluconazole resistance of Candida krusei strains often required a full 48 h of incubation in order to be observed by the standard method. For the disk diffusion tests that were performed on Mueller-Hinton agar with glucose and methylene blue, 97% of results were in agreement with those of the reference test, especially when zones of inhibition were measured after the first 24 h of incubation. Some Candida glabrata isolates failed to grow satisfactorily until a full 48 h of incubation was completed. Precision was determined by testing 50 selected isolates in triplicate in each of three laboratories. The reproducibility of results of disk diffusion tests was comparable to that of the reference method. With all procedures, determination of test results was particularly challenging with some strains, and new methods are needed in order to improve endpoint definition.Compromised patients, such as those infected with human immunodeficiency virus, are often colonized by and/or infected with fungi, especially Candida spp. Consequently, they frequently receive antifungal agents such as fluconazole for relatively long periods of time during hospitalization. Prolonged exposure to an azole such as fluconazole can select strains with diminished susceptibilities (6, 7), and consequently, increasing doses may be necessary. For this reason, the susceptibilities of isolates recovered from compromised patients receiving prolonged fluconazole treatment should be monitored in order to determine when strains with decreased susceptibilities have been selected (3). In order to do this in a cost-effective way, simple, inexpensive testing procedures are needed, but such tests must be accurate and precise. The purpose of this report is to document the relative levels of accuracy and precision of three procedures for testing fluconazole: broth microdilution, Etest, and disk diffusion. The accuracy of each procedure was assessed by comparing the results to those obtained by the 48-h microdilution reference method of the National Committee for Clinical Laboratory Standards (NCCLS) (8). Precision was measured by performing replicate tests in three separate laboratories. MATERIALS AND METHODSMicroorganisms. For this study, M. A. Pfaller selected 495 clinical isolates of Candida spp. for which there was a broad range of fluconazole MICs. The five species that were represented are shown in Table 1. For testing reproducibility, 50 of the 495 isolates were selected in order to maximize the number of strains for which MICs were near the interpretive breakpoints of Յ8.0 g/ml (susceptible) and Ն64 g/ml (resistant). This subset of strains included 26 strains of Candida albicans and 6 strains each of Candida glabrata, Candida krusei, Candida parapsilosis, and Cand...

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The activity of omiganan pentahydrochloride (formerly MBI 226; a synthetic cationic peptide) was assessed against 1,437 recent clinical bacterial isolates and 214 recent clinical yeast isolates. The omiganan was highly active, and minimal bactericidal concentrations or minimal fungicidal concentrations were either equal to or two-to fourfold higher than MICs. Kill curve experiments showed a clear pattern of bactericidal activity.