Characterization of T Cells Specific for CFP-10 and ESAT-6 in Mycobacterium tuberculosis-Infected Mauritian Cynomolgus Macaques.

Nonhuman primates can be used to study host immune responses to Mycobacterium tuberculosis Mauritian cynomolgus macaques (MCMs) are a unique group of animals that have limited major histocompatibility complex (MHC) genetic diversity, such that MHC-identical animals can be infected with M. tuberculosis Two MCMs homozygous for the relatively common M1 MHC haplotype were bronchoscopically infected with 41 CFU of the M. tuberculosis Erdman strain. Four other MCMs, which had at least one copy of the M1 MHC haplotype, were infected with a lower dose of 3 CFU M. tuberculosis All animals mounted similar T-cell responses to CFP-10 and ESAT-6. Two epitopes in CFP-10 were characterized, and the MHC class II alleles restricting them were determined. A third epitope in CFP-10 was identified but exhibited promiscuous restriction. The CFP-10 and ESAT-6 antigenic regions targeted by T cells in MCMs were comparable to those seen in cases of human M. tuberculosis infection. Our data lay the foundation for generating tetrameric molecules to study epitope-specific CD4 T cells in M. tuberculosis-infected MCMs, which may guide future testing of tuberculosis vaccines in nonhuman primates.

In vitro responses of Acinetobacter baumannii to two- and three-drug combinations following exposure to colistin and doripenem.

We compared in vitro killing of colistin, doripenem, and sulbactam by time-kill methods against Acinetobacter baumannii isolates collected from patients before and after colistin-doripenem treatment (initial and recurrent isolates, respectively). Colistin-doripenem bactericidal activity against recurrent isolates was attenuated (mean log10 kill, -5.74 versus -2.88; P = 0.01) but was restored by adding sulbactam. Doripenem MICs rather than colistin MICs correlated with the activity of colistin-doripenem. Among colistin-resistant isolates, colistin-doripenem-sulbactam combinations achieved greater killing than colistin-doripenem alone (-5.65 versus -2.43; P = 0.04).

Anidulafungin and micafungin MIC breakpoints are superior to that of caspofungin for identifying FKS mutant Candida glabrata strains and Echinocandin resistance.

By CLSI interpretive criteria, anidulafungin and micafungin MICs determined by various methods were sensitive (60 to 70%) and highly specific (94 to 100%) for identifying FKS mutations among 120 Candida glabrata isolates. Anidulafungin and micafungin breakpoints were more specific than CLSI's caspofungin breakpoint in identifying FKS mutant strains and patients with invasive candidiasis who were likely to fail echinocandin treatment (P ≤ 0.0001 for both). Echinocandin MICs were most useful clinically when interpreted in the context of prior echinocandin exposure.

Caspofungin MICs correlate with treatment outcomes among patients with Candida glabrata invasive candidiasis and prior echinocandin exposure.

Mutations in Candida glabrata FKS genes, which encode the echinocandin target enzyme, are independent risk factors for treatment failures during invasive candidiasis. We retrospectively compared the ability of caspofungin susceptibility testing methods to identify C. glabrata FKS mutant isolates and predict outcomes among patients at our center. Eight percent (10/120) of sterile-site C. glabrata isolates harbored FKS1 (n = 3) or FKS2 (n = 7) mutations, including 32% (10/32) recovered from patients with prior echinocandin exposure. Median echinocandin exposures for mutant and nonmutant isolates were 55 (range, 7 to 188) and 13 (3 to 84) days, respectively (P = 0.004). Sensitivity and specificity of the CLSI caspofungin resistance breakpoint MIC (>0.12 µg/ml by broth microdilution using RPMI medium [BMD-RPMI]) were 90% (9/10) and 3% (3/110), respectively, for identifying FKS mutants. Sensitivity and specificity of receiver-operator characteristic (ROC) curve-derived breakpoints by BMD-RPMI, BMD-antibiotic medium 3, Etest, and YeastOne ranged from 70 to 100% and 89 to 95%, respectively; susceptibility rates varied from 83 to 90%. The 14-day echinocandin treatment success rate was 67% (44/66); failure was more likely with prior echinocandin exposure (P = 0.002) or infection with an FKS mutant (P = 0.0001) or echinocandin-resistant isolates by BMD-AM3, Etest, and YeastOne (P ≤ 0.03). The failure rate among patients with prior exposure and infection with a resistant isolate was 91% (10/11); it was 22% (12/55) among others (P < 0.0001). In conclusion, ROC-derived caspofungin MIC breakpoints by several methods were sensitive and specific for identifying C. glabrata FKS mutant isolates. Mutations were seen exclusively among patients with prior echinocandin exposure. A paradigm that considers prior echinocandin exposure and caspofungin MICs accurately classified treatment outcomes for C. glabrata invasive candidiasis.