In vitro combination between antifungals and diphenyl diselenide against Cryptococcus species.

Cryptococcus species are an encapsulated fungal pathogen that cause cryptococcal meningitis. There are limited therapeutic options for this infection. The management includes the use of different antifungals such as amphotericin B, flucytosine, or fluconazole, either alone or in combination. However, numerous therapeutic failures, as well as the limited effectiveness of such therapeutics, have been described. Diphenyl diselenide is a chemically synthesised molecule with was found to have antimicrobial activity. In this study, we evaluated the antifungal activities of fluconazole, amphotericin B and flucytosine, in combination with diphenyl diselenide against 30 clinical isolates of Cryptococcus spp. using CLSI M27-A3 method and the checkerboard microdilution technique. Our results show that the combination of flucytosine and diphenyl diselenide displayed 100% of synergism. However, when we analysed (PhSe)2 plus AMB or FLZ we observed around 70% of indifference. Our results suggest that the combination of diphenyl diselenide with other antifungal agents deserves attention as a new option for the development of alternative therapies for cryptococcosis.

In vitro interaction of antifungal and antibacterial drugs against Cryptococcus neoformans var. grubii before and after capsular induction.

This study evaluated the synergistic interactions between amphotericin B (AMB) and azithromycin (AZM), daptomycin (DAP), linezolid (LNZ), minocycline (MINO), fluconazole (FLZ), flucytosine (5FC), linezolid (LZD), or tigecycline (TIG) against clinical isolates of Cryptococcus neoformans var. grubii before and after capsule induction. High synergism (>75%) was observed for the combinations, AMB+5FC, AMB+TIG, AMB+AZM, AMB+LZD and AMB+MINO but only in the strains after capsule induction. The results show that the presence of the capsule may lower the minimum inhibitory concentrations (MICs) of antifungal agents, but antimicrobial activity can be improved by combining antifungal and antibacterial agents.

SUSCEPTIBILITY OF Candida spp. ISOLATED FROM BLOOD CULTURES AS EVALUATED USING THE M27-A3 AND NEW M27-S4 APPROVED BREAKPOINTS / Suscetibilidade de Candida spp. isoladas de hemocultivos, avaliadas pelos breakpoints dos documentos M27-A3 e M27-S4 do CLSI

The high mortality rates associated with candidemia episodes and the emergence of resistance to antifungal agents necessitate the monitoring of the susceptibility of fungal isolates to antifungal treatments. The new, recently approved, species-specific clinical breakpoints (SS-CBPs)(M27-S4) for evaluating susceptibility require careful interpretation and comparison with the former proposals made using the M27-A3 breakpoints, both from CLSI. This study evaluated the susceptibility of the different species of Candida that were isolated from candidemias based on these two clinical breakpoints. Four hundred and twenty-two isolates were identified and, among them, C. parapsilosis comprised 46.68%, followed by C. albicans (35.78%), C. tropicalis (9.71%), C. glabrata (3.55%), C. lusitaniae (1.65%), C. guilliermondii (1.65%) and C. krusei (0.94%). In accordance with the M27-A3 criteria, 33 (7.81%) non-susceptible isolates were identified, of which 16 (3.79%) were resistant to antifungal agents. According to SS-CBPs, 80 (18.95%) isolates were non-susceptible, and 10 (2.36%) of these were drug resistant. When the total number of non-susceptible isolates was considered, the new SS-CBPs detected 2.4 times the number of isolates that were detected using the M27-A3 interpretative criteria. In conclusion, the detection of an elevated number of non-susceptible species has highlighted the relevance of evaluating susceptibility tests using new, species-specific clinical breakpoints (SS-CBPs), which could impact the profile of non-susceptible Candida spp. to antifungal agents that require continuous susceptibility monitoring.

As elevadas taxas de mortalidade associadas com episódios de candidemia e a emergência da resistência aos antifúngicos, requerem o monitoramento da suscetibilidade de Candida spp., isoladas das candidemias, frente aos agentes antifúngicos. Os novos breakpoints, chamados “espécie-específicos,” foram recentemente aprovados (M27-S4) requerendo, pois, cuidadosa interpretação e comparações com aqueles até agora utilizados (M27-A3); ambos são propostos pelo Clinical Laboratory Standard Institute (CLSI). O presente estudo avaliou a suscetibilidade de espécies de Candida isoladas de candidemias baseando-se nestes dois breakpoints. Quatrocentos e vinte e dois isolados de Candida foram identificados e assim distribuídos: C. parapsilosis (48,68%), C. albicans (35,78%), C. tropicalis (9,71%), C. glabrata (3,55%), C. lusitaniae (1,65%), C. guilliermondii (1,65%), C. krusei (0,94%). Com base nos critérios do M27-A3, um total de 33 (7,81%) isolados foram julgados não-sensíveis, dos quais 16 (3,79%) como resistentes aos antifúngicos. De acordo com os breakpoints espécie-específicos (M27-S4) um total de 80 (18,95%) isolados foram considerados não-sensíveis, dos quais 10 (2,36%) resistentes a algum dos antifúngicos testados. Com base nos novos breakpoints espécie-específicos, o número de isolados não-sensíveis foi 2,4 vezes maior do que o número de não-sensíveis detectado pelos breakpoints do documento M27-A3. A detecção de um elevado número de isolados não-sensíveis através dos breakpoints propostos pelo M27-S4 destaca a importância dos testes de suscetibilidade, os quais trarão impactos no reconhecimento de isolados de Candida spp. não-sensíveis em episódios de candidemias, requerendo, portanto, continua avaliação.

Susceptibility of Candida spp. isolated from blood cultures as evaluated using the M27-A3 and new M27-S4 approved breakpoints.

The high mortality rates associated with candidemia episodes and the emergence of resistance to antifungal agents necessitate the monitoring of the susceptibility of fungal isolates to antifungal treatments. The new, recently approved, species-specific clinical breakpoints (SS-CBPs)(M27-S4) for evaluating susceptibility require careful interpretation and comparison with the former proposals made using the M27-A3 breakpoints, both from CLSI. This study evaluated the susceptibility of the different species of Candida that were isolated from candidemias based on these two clinical breakpoints. Four hundred and twenty-two isolates were identified and, among them, C. parapsilosis comprised 46.68%, followed by C. albicans (35.78%), C. tropicalis (9.71%), C. glabrata (3.55%), C. lusitaniae (1.65%), C. guilliermondii (1.65%) and C. krusei (0.94%). In accordance with the M27-A3 criteria, 33 (7.81%) non-susceptible isolates were identified, of which 16 (3.79%) were resistant to antifungal agents. According to SS-CBPs, 80 (18.95%) isolates were non-susceptible, and 10 (2.36%) of these were drug resistant. When the total number of non-susceptible isolates was considered, the new SS-CBPs detected 2.4 times the number of isolates that were detected using the M27-A3 interpretative criteria. In conclusion, the detection of an elevated number of non-susceptible species has highlighted the relevance of evaluating susceptibility tests using new, species-specific clinical breakpoints (SS-CBPs), which could impact the profile of non-susceptible Candida spp. to antifungal agents that require continuous susceptibility monitoring.

Synergysm of voriconazole or itraconazole with other antifungal agents against species of Fusarium.

BACKGROUND: Infections caused by Fusarium are difficult to treat because these fungi show in vitro and in vivo resistance to practically all the antifungal agents available, which explains the high mortality rates. An attempt to overcome fungal resistance is the combination of antifungal agents, especially those with different mechanisms of action. AIMS: Evaluate the in vitro interactions of combinations of voriconazole or itraconazole with other antifungal agents against 32 isolates of Fusarium spp.: Fusarium chlamydosporum, Fusarium oxysporum, Fusarium proliferatum and Fusarium solani. METHODS: Drug interactions were assessed by a checkerboard microdilution method that also included the determination of the MIC of each drug alone according to CLSI (Clinical and Laboratory Standards Institute) document M38-A2, 2008. RESULTS: The best combinations were voriconazole+terbinafine which showed synergism against 84% of Fusarium strains. Other synergistic combinations were voriconazole+itraconazole (50%), voriconazole+fluconazole (50%), voriconazole+miconazole (38%), voriconazole+flucytosine (22%) and voriconazole+ketoconazole (25%). The synergisms observed with itraconazole combinations were itraconazole+terbinafine (25%) and itraconazole+flucytosine (9.37%). The antagonisms observed were: voriconazole+fluconazole (3%) and itraconazole+flucytosine (12.5%). CONCLUSIONS: The synergism showed by voriconazole+terbinafine was remarkable. To better elucidate the potential usefulness of our findings, new in vivo and in vitro studies deserve be performed.

In vitro synergisms obtained by amphotericin B and voriconazole associated with non-antifungal agents against Fusarium spp.

Fusarium spp is an opportunistic fungal pathogen responsible for causing invasive hyalohyphomycosis in immunocompromised patients. Due to its susceptibility pattern with a remarkable resistance to antifungal agents the treatment failures and mortality rates are high. To overcome this situation, combination therapy may be considered which must be subjected to in vitro tests. In vitro activities of amphotericin B, itraconazole, and voriconazole associated with azithromycin, ciprofloxacin, fluvastatin, ibuprofen, metronidazole, and also the combination of amphotericin B plus rifampin against 23 strains of Fusarium spp. through the checkerboard technique based on M38-A2 [Clinical and Laboratory Standards Institute (2008). Reference method for broth dilution antifungal susceptibility testing of filamentous fungi; approved standard, 2nd ed. (CLSI document M38-A2) (ISBN 1-56238-668-9). Wayne, PA: CLSI] were evaluated. The best synergistic interactions with amphotericin B were with ibuprofen (43.5%) (FICI [fractional inhibitory concentration index] range = 0.25-2). Combinations with voriconazole showed synergism, mainly with ciprofloxacin (30.4%) (FICI range = 0.25-3) and metronidazole (30.4%) (FICI range = 0.1-4); however, all the combinations with itraconazole were indifferent. In general, antagonistic interactions were not registered. Our results showed that in vitro synergisms obtained by some combinations studied deserve attention since they were better than those showed by the antimycotic.