RESUMEN
Antimicrobial susceptibility testing (AST) of clinical isolates of Nocardia is recommended to detect resistance to commonly used antimicrobial agents; such testing is complicated by difficulties in inoculum preparation and test interpretation. In this study, six laboratories performed repetitive broth microdilution testing on single strains of Nocardia brasiliensis, Nocardia cyriacigeorgica, Nocardia farcinica, Nocardia nova, and Nocardia wallacei. For each isolate, a total of 30 microdilution panels from three different lots were tested at most sites. The goal of the study was to determine the inter- and intralaboratory reproducibility of susceptibility testing of this group of isolates. Acceptable agreement (>90% agreement at ±1 dilution of the MIC mode) was found for amikacin, ciprofloxacin, clarithromycin, and moxifloxacin. After eliminating MIC values from single laboratories whose results showed the greatest deviation from those of the remaining laboratories, acceptable agreement was also found for amoxicillin-clavulanic acid, linezolid, minocycline, and tobramycin. Results showed unsatisfactory reproducibility of broth microdilution testing of ceftriaxone with N. cyriacigeorgica and N. wallacei, tigecycline with N. brasiliensis and N. cyriacigeorgica, and sulfonamides with N. farcinica and N. wallacei. N. nova ATCC BAA-2227 is proposed as a quality control organism for AST of Nocardia sp., and the use of a disk diffusion test for sulfisoxazole is proposed as a check of the adequacy of the inoculum and to confirm sulfonamide MIC results.
Asunto(s)
Antibacterianos/farmacología , Pruebas de Sensibilidad Microbiana/normas , Nocardia/efectos de los fármacos , Ensayos de Aptitud de Laboratorios , Pruebas de Sensibilidad Microbiana/métodos , Reproducibilidad de los ResultadosRESUMEN
Combination antifungal therapy is widely used but not well understood. We analyzed the spectrophotometric readings from a multicenter study conducted by the New York State Department of Health to further characterize the in vitro interactions of the major classes of antifungal agents against Candida spp. Loewe additivity-based fractional inhibitory concentration index (FICi) analysis and Bliss independence-based response surface (BIRS) analysis were used to analyze two-drug inter- and intraclass combinations of triazoles (AZO) (voriconazole, posaconazole), echinocandins (ECH) (caspofungin, micafungin, anidulafungin), and a polyene (amphotericin B) against Candida albicans, C. parapsilosis, and C. glabrata. Although mean FIC indices did not differ statistically significantly from the additivity range of 0.5−4, indicating no significant pharmacodynamic interactions for all of the strain−combinations tested, BIRS analysis showed that significant pharmacodynamic interactions with the sum of percentages of interactions determined with this analysis were strongly associated with the FIC indices (Χ2 646, p < 0.0001). Using a narrower additivity range of 1−2 FIC index analysis, statistically significant pharmacodynamic interactions were also found with FICi and were in agreement with those found with BIRS analysis. All ECH+AB combinations were found to be synergistic against all Candida strains except C. glabrata. For the AZO+AB combinations, synergy was found mostly with the POS+AB combination. All AZO+ECH combinations except POS+CAS were synergistic against all Candida strains although with variable magnitude; significant antagonism was found for the POS+MIF combination against C. albicans. The AZO+AZO combination was additive for all strains except for a C. parapsilosis strain for which antagonism was also observed. The ECH+ECH combinations were synergistic for all Candida strains except C. glabrata for which they were additive; no antagonism was found.
RESUMEN
Global spread of antimicrobial multidrug resistance (MDR) in human and veterinary medicine relies upon diagnostics, surveillance and stewardship to guide mitigation. Utilizing surveillance of fecal samples from our service area for detecting MDR Escherichia coli carriage in humans (2143), dogs (627), and cattle (130), we found isolates resistant to third/fourth generation cephems present in 3.7 %, 13.1 %, and 51.5 %, respectively. CMY-2, CTX-M-15-like and CTX-M9 group genes in descending order were predominant in all hosts and accounted for 83.3 % of non-wild-type gene targets. MDR carriage mirrored cephem non-susceptibility rates as published in annual antibiograms for humans and dogs; notably, no carbapenem-resistant carriage isolates were detected. Given the scale of MDR E. coli carriage in cattle (14X) and dogs (3.5X) compared to humans, bench-marking of the resistance gene pool by host species utilizing regional One Health surveillance may aid in assessing occupational and geographic risks for acquiring resistance and for monitoring of mitigation strategies.
Asunto(s)
Antiinfecciosos , Enfermedades de los Bovinos , Enfermedades de los Perros , Infecciones por Escherichia coli , Animales , Antibacterianos/farmacología , Bovinos , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Perros/epidemiología , Perros , Escherichia coli , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/veterinaria , Humanos , Pruebas de Sensibilidad Microbiana/veterinaria , beta-Lactamasas/genéticaRESUMEN
There are few multilaboratory studies of antifungal combination testing to suggest a format for use in clinical laboratories. In the present study, eight laboratories tested quality control (QC) strain Candida parapsilosis ATCC 22019 and clinical isolates Candida albicans 20533.043, C. albicans 20464.007, Candida glabrata 20205.075, and C. parapsilosis 20580.070. The clinical isolates had relatively high azole and echinocandin MICs. A modified CLSI M27-A3 protocol was used, with 96-well custom-made plates containing checkerboard pairwise combinations of amphotericin B (AMB), anidulafungin (AND), caspofungin (CSP), micafungin (MCF), posaconazole (PSC), and voriconazole (VRC). The endpoints were scored visually and on a spectrophotometer or enzyme-linked immunosorbent assay (ELISA) reader for 50% growth reduction (50% inhibitory concentration [IC(50)]). Combination IC(50)s were used to calculate summation fractional inhibitory concentration indices (FICIs) (ΣFIC) based on the Lowe additivity formula. The results revealed that the IC(50)s of all drug combinations were lower or equal to the IC(50) of individual drugs in the combination. A majority of the ΣFIC values were indifferent (ΣFIC = 0.51 to 2.0), but no antagonism was observed (ΣFIC ≥ 4). Synergistic combinations (ΣFIC ≤ 0.5) were found for AMB-PSC against C. glabrata and for AMB-AND and AMB-CSP against C. parapsilosis by both visual and spectrophotometric readings. Additional synergistic interactions were revealed by either of the two endpoints for AMB-AND, AMB-CSP, AMB-MCF, AMB-PSC, AMB-VRC, AND-PSC, CSP-MCF, and CSP-PSC. The percent agreements among participating laboratories ranged from 37.5% (lowest) for AND-CSP and POS-VOR to 87.5% (highest) for AMB-MCF and AND-CSP. Median ΣFIC values showed a wide dispersion, and interlaboratory agreements were less than 85% in most instances. Additional studies are needed to improve the interlaboratory reproducibility of antifungal combination testing.
Asunto(s)
Antifúngicos/farmacología , Candida glabrata/efectos de los fármacos , Candida/efectos de los fármacos , Anfotericina B/farmacología , Anidulafungina , Caspofungina , Combinación de Medicamentos , Equinocandinas/farmacología , Ensayo de Inmunoadsorción Enzimática , Concentración 50 Inhibidora , Lipopéptidos/farmacología , Micafungina , Pruebas de Sensibilidad Microbiana , Pirimidinas/farmacología , Triazoles/farmacología , VoriconazolRESUMEN
We investigated if CLSI M27-A2 Candida species breakpoints for fluconazole MIC are valid when read at 24 h. Analysis of a data set showed good correlation between 48- and 24-h MICs, as well as similar outcomes and pharmacodynamic efficacy parameters, except for isolates in the susceptible dose-dependent category, such as Candida glabrata.
Asunto(s)
Antifúngicos/farmacología , Candida/efectos de los fármacos , Fluconazol/farmacología , Pruebas de Sensibilidad Microbiana/normas , Animales , Antifúngicos/administración & dosificación , Candida/aislamiento & purificación , Candidiasis/tratamiento farmacológico , Candidiasis/microbiología , Bases de Datos Factuales , Fluconazol/administración & dosificación , Humanos , Pruebas de Sensibilidad Microbiana/métodos , Pruebas de Sensibilidad Microbiana/estadística & datos numéricos , Modelos Biológicos , Factores de TiempoAsunto(s)
Antibacterianos/farmacología , Bacterias Gramnegativas/efectos de los fármacos , Cocos Grampositivos/efectos de los fármacos , Minociclina/análogos & derivados , Polisorbatos/farmacología , Tensoactivos/farmacología , Farmacorresistencia Bacteriana , Humanos , Pruebas de Sensibilidad Microbiana/métodos , Pruebas de Sensibilidad Microbiana/normas , Minociclina/farmacología , Estándares de Referencia , TigeciclinaRESUMEN
Candida krusei ATCC 6258 was tested by eight laboratories using 96-well plates containing checkerboard pairwise combinations of amphotericin B (AMB), posaconazole (PSC), caspofungin (CSP), and voriconazole (VRC). The methodology led to reproducible results across the laboratories. All drug combinations yielded MICs lower than the MICs of any two drugs tested singly, and combinations of AMB, PSC, CSP, and VRC were indifferent (no antagonism) by summations of fractional inhibitory concentration.
Asunto(s)
Antifúngicos/farmacología , Candida/efectos de los fármacos , Laboratorios , Control de Calidad , Anfotericina B/farmacología , Candida/aislamiento & purificación , Caspofungina , Quimioterapia Combinada , Equinocandinas/farmacología , Humanos , Lipopéptidos , Pruebas de Sensibilidad Microbiana/métodos , Pruebas de Sensibilidad Microbiana/normas , Pirimidinas/farmacología , Triazoles/farmacología , VoriconazolRESUMEN
Sensititre YeastOne colorimetric antifungal panels were compared with the CLSI (formerly NCCLS) M38-A reference method for testing the susceptibility of filamentous fungi to posaconazole; agreement (+/-2 log2 dilutions) between the two methods was 97%. These data confirm the utility of YeastOne panels for measuring the susceptibility of filamentous fungi to posaconazole.
Asunto(s)
Antifúngicos/farmacología , Colorimetría/métodos , Hongos/efectos de los fármacos , Hongos Mitospóricos/efectos de los fármacos , Triazoles/farmacología , Colorimetría/instrumentación , Humanos , Pruebas de Sensibilidad Microbiana/instrumentación , Pruebas de Sensibilidad Microbiana/métodos , Estándares de ReferenciaRESUMEN
Performance of antimicrobial susceptibility tests with new agents requires careful consideration of the properties of the antimicrobial to ensure that the tests are standardized, reproducible, and reflect the true potency of the drug. Dalbavancin is a new glycopeptide with potent activity against gram-positive bacterial species. The investigations described here demonstrated that methodologic modifications of procedures are necessary to ensure consistent test results, both for quality control and for routine testing of clinical isolates. Dimethyl sulfoxide is the preferred primary solvent. The addition of 0.002% polysorbate-80 (a surfactant) to dalbavancin-containing wells in the reference broth microdilution assay resulted in consistent and reproducible MIC results for three quality control strains: Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, and Streptococcus pneumoniae ATCC 49619. The same degree of consistency was observed among clinical isolates of gram-positive bacterial species tested in several clinical laboratories. These results indicate that the addition of 0.002% (final concentration) of the surfactant in broth microdilution tests produces optimal dalbavancin MICs required for accurate and reproducible clinical laboratory tests, without untoward influences of substrate binding or media constituents.