Activity of tannins from Stryphnodendron adstringens on Cryptococcus neoformans: effects on growth, capsule size and pigmentation

Background

Infections sustained by multidrug-resistant (MDR) and pan-resistant Acinetobacter baumannii have become a challenging problem in Intensive Care Units. Tigecycline provided new hope for the treatment of MDR A. baumannii infections, but isolates showing reduced susceptibility have emerged in many countries, further limiting the therapeutic options. Empirical combination therapy has become a common practice to treat patients infected with MDR A. baumannii, in spite of the limited microbiological and clinical evidence supporting its efficacy. Here, the in vitro interaction of tigecycline with seven commonly used anti-Acinetobacter drugs has been assessed.

Methods

Twenty-two MDR A. baumannii isolates from Intensive Care Unit (ICU) patients and two reference strains for the European clonal lineages I and II (including 3, 15 and 6 isolates that were resistant, intermediate and susceptible to tigecycline, respectively) were tested. Antimicrobial agents were: tigecycline, levofloxacin, piperacillin-tazobactam, amikacin, imipenem, rifampicin, ampicillin-sulbactam, and colistin. MICs were determined by the broth microdilution method. Antibiotic interactions were determined by chequerboard and time-kill assays. Only antibiotic combinations showing synergism or antagonism in both chequerboard and time-kill assays were accepted as authentic synergistic or antagonistic interactions, respectively.

Results

Considering all antimicrobials in combination with tigecycline, chequerboard analysis showed 5.9% synergy, 85.7% indifference, and 8.3% antagonism. Tigecycline showed synergism with levofloxacin (4 strains; 16.6%), amikacin (2 strains; 8.3%), imipenem (2 strains; 8.3%) and colistin (2 strains; 8.3%). Antagonism was observed for the tigecycline/piperacillin-tazobactam combination (8 strains; 33.3%). Synergism was detected only among tigecycline non-susceptible strains. Time-kill assays confirmed the synergistic interaction between tigecycline and levofloxacin, amikacin, imipenem and colistin for 5 of 7 selected isolates. No antagonism was confirmed by time-kill assays.

Conclusion

This study demonstrates the in vitro synergistic activity of tigecycline in combination with colistin, levofloxacin, amikacin and imipenem against five tigecycline non-susceptible A. baumannii strains, opening the way to a more rationale clinical assessment of novel combination therapies to combat infections caused by MDR and pan-resistant A. baumannii.     

In vitro activity of the lipopeptide PAL-Lys-Lys-NH2, alone and in combination with antifungal agents, against clinical isolates of Candida spp

Candida albicans is known to be the organism most often associated with serious fungal infection, but other Candida spp. are emerging as clinical pathogens associated with opportunistic infections. Among antimycotic treatments, increasing attention is currently given to anti-infective drugs based upon naturally occurring peptides, such as the short lipopeptide palmitoyl PAL-Lys-Lys-NH2 (PAL). The aim of this study is to evaluate the activity of this peptide compared to the traditional antifungal agents Fluconazole (FLU), amphotericin B (AMB) and caspofungin (CAS) on Candida spp. 24 clinical isolates of Candida spp. were tested against PAL_, FLU, AMB and CAS using in vitro susceptibility tests, time killing and checkerboard assay. All of the drugs studied showed good activity against clinical isolates of candida; in particular CAS and AMB which have MICs value lower than PAL and FLU. Moreover we observed synergistic interactions for PAL/FLU (81.25%), PAL/AMB (75%) and particularly for PAL/CAS (87.5). We think that our results are interesting since synergy between PAL and CAS might be useful in clinic trails to treat invasive fungal infections.     

Electrophoretic karyotyping and antifungal susceptibility patterns of Candida parapsilosis clinical isolates causing deep and superficial fungal infections

Forty-six isolates of Candida parapsilosis, each from a single patient, were collected from July 1993 through March 1999 at the University of Ancona Hospitals and Clinics. Twenty-eight strains were isolated from superficial lesioned sites, including skin, nails and other sources while 18 strains were isolated from blood. The isolates were typed by electrophoretickaryotyping (EK) and tested for their susceptibility to fluconazole (FLC),itraconazole (ITC), flucytosine (5-FC), and amphotericin B (AMB). Ourdata confirmed that EK is a useful technique for DNA typing of isolates ofCandida parapsilosis and showed that the source of isolation is notassociated with a given DNA type. Although strains belonging to this speciesof Candida are susceptible to the most common antifungals, including the triazoles, the degree of ITC susceptibility was dose dependent (MIC rangingfrom 0.25–0.5 μg/ml) for 98% of the isolates. This revised version was published online in June 2006 with corrections to the Cover Date.     

In Vitro Interaction of Itraconazole with Amphotericin B,Caspofungin, and Terbinafine Against Clinical Isolates of <Emphasis Type="Italic">Trichosporon asahii</Emphasis>

Treatment of disseminated trichosporosis is still challenging. Itraconazole is a widely used broad-spectrum antifungal drug. In vitro interactions of itraconazole (ICZ) with amphotericin B (AMB), caspofungin (CAS), and terbinafine (TBF) against 18 clinical isolates of Trichosporon asahii were assessed by chequerboard microdilution method. ICZ combined with CAS showed the highest percentage of synergistic effect (72.2%), followed by ICZ/AMB (11%) and ICZ/TBF (11%) combination. Antagonistic effect was not observed. This study demonstrates that itraconazole can enhance the antifungal activity of CAS against T. asahii, suggesting that this combination may be a potential strategy for treating disseminated trichosporosis.     

Microbiological Characteristics and Susceptibility Patterns of Strains of Rhodotorula Isolated from Clinical Samples

The members of the genus Rhodotorula show a marked ubiquity. In man, they have been isolated from faeces, nails, skin, sputum, digestive tract and adenoids, forming part of the normal human flora, although in recent years cases have been reported of both local and systemic infection by this yeast. There are virtually no studies in the literature on the sensitivity of this genus to the antifungal agents in common clinical use. Therefore, it is considered of interest to study the microbiological characteristics and the susceptibility patterns of Rhodotorula isolated from clinical samples. A total of 35 different strains of Rhodotorula were studied. In vitro susceptibility testing to 5-fluorocytosine, amphotericin B, ketoconazole, fluconazole and itraconazole was performed. All the strains were considered sensitive to 5-fluorocytosine, amphotericin B, ketoconazole and itraconazole and resistant to fluconazole. As a conclusion, we can state that all the antifungal agents tested, except fluconazole, are useful medicaments for the treatment of infections by the Rhodotorula genus. This revised version was published online in June 2006 with corrections to the Cover Date.     

Distribution and identification of red yeasts in deep-sea environments around the northwest Pacific Ocean

We isolated 99 yeast strains, including 40 red yeasts, from benthic animals and sediments collected from the deep-sea floor in various areas in the northwest Pacific Ocean. Comparing the yeast isolates from animals and sediments collected from shallow locations, the proportion of red yeasts differed considerably, comprising 81.5% and 10.6% of the isolates from animals and sediments, respectively. All of the red yeast isolates belonged to the genera Rhodotorula and Sporobolomyces. On the basis of morphological and physiological characteristics, the isolates were identified as R. aurantiaca, R. glutinis, R. minuta and R. mucilaginosa of the genus Rhodotorula, and S. salmonicolor and S. shibatanus of the genus Sporobolomyces. Only R. glutinis and R. mucilaginosa were isolated from sediments. All of the others were isolated from animal sources. Phylogenetic analyses based on internal transcribed spacer (ITS) regions and 5.8S rRNA gene sequences allowed us to establish the precise taxonomic placement of each of the isolates and thereby investigate the intraspecific relationships among the isolates. Twenty-two strains identified as members of R. glutinis, which showed a wide distribution in the deep-sea, and five isolates identified as R. minuta, which were isolated only from benthic animals, showed substantial heterogeneity within the species. The isolates phenotypically identified as Sporobolomyces species and R. mucilaginosa phylogenetically occupied the placements corresponding to these species. Some strains assigned to known species on the basis of phenotypic features should be regarded as new species as suggested by the results of molecular analysis.     

Synergistic Effect Between Two Bacteriocin-like Inhibitory Substances Produced by Lactobacilli Strains with Inhibitory Activity for <Emphasis Type="Italic">Streptococcus agalactiae</Emphasis>

Group B streptococci (GBS) are bacterial species that colonize the vagina in pregnant women and as such may cause serious infections in neonates that passed through the birth channel. The objective of this work was to study the inhibitory activities produced by each bacteriocin-like inhibitory substance (BLIS) of Lactobacillus rhamnosus L60 and Lactobacillus fermentum L23, and the effects of the combined BLIS-es of these lactobacilli on GBS. The interactions between the BLIS-es were assessed by qualitative and quantitative methods on agar plates. The minimum inhibitory concentrations (MICs) and fractional inhibitory concentrations (FICs) were determined by a modification of the broth microdilution and checkerboard methods, respectively. Antibiotic susceptibilities of all S. agalactiae strains were assayed and the results of these tests were evaluated for statistical significance. A 7.5% of GBS isolates were recovered from 760 pregnant women and 91% of those strains were susceptible to each BLIS produced by L. fermentum, L. rhamnosus, and also to a mixture of them. The comparisons among the BLIS-es showed statistically significant differences, with a combination of the BLIS-es from the two Lactobacillus species being better than the BLIS of each one alone (P < 0.05) as GBS growth inhibitors. Synergistic activities between the BLIS-es were found on 100% of susceptible GBS strains, MICs ranges of BLIS of L23 and L60 were 80–160 and 160–320 UA ml⁻¹, respectively. By the checkerboard method, the BLIS-es combination showed synergistic effect on all sensitive strains tested, with values of FICs ranging from 0.131 to 0.218. The BLIS-es produced by these lactobacilli of vaginal origin were able to inhibit S. agalactiae isolates. The results indicate that these strains may have probiotic potential for the control of GBS in women and may consequently prevent GBS infections in newborns.     

In Vitro Activity of Berberine Alone and in Combination with Antifungal Drugs Against Planktonic Forms and Biofilms of <Emphasis Type="Italic">Trichosporon Asahii</Emphasis>

Trichosporon asahii (T. asahii) is an opportunistic pathogen that can cause life-threatening infections in immunocompromised patients, with high mortality rates up to 80% despite treated with antifungal drugs. The biofilms-forming ability of T. asahii on indwelling medical devices may account for the resistance to antifungal drugs. Berberine (BBR) has been demonstrated to have antifungal activity and synergistic effects in combination with antifungal drugs against pathogenic fungi. In the present study, the in vitro activities of BBR alone or combined with fluconazole (FLC), itraconazole (ITC), voriconazole (VRC), caspofungin (CAS) and amphotericin B (AMB) against planktonic forms and biofilms of 21 clinical T. asahii isolates were evaluated using checkerboard microdilution method and XTT reduction assay, respectively. The fractional inhibitory concentration index (FICI) was used to interpret drug interactions. BBR alone did not exhibit significant antifungal activities against both T. asahii planktonic cells (MICs, 32 → 128 μg/ml) and T. asahii biofilms (SMICs, >128 μg/ml). However, BBR exhibited synergistic effects against T. asahii planktonic cells in combination with AMB, FLC and CAS (FICI ≤ 0.5) and exhibited synergistic effects against T. asahii biofilms in combination with AMB and CAS (FICI ≤ 0.5). BBR/ITC and BBR/VRC combinations yielded mainly indifferent interactions against T. asahii planktonic cells. BBR/FLC, BBR/ITC and BBR/VRC combinations also yielded indifferent interactions against T. asahii biofilms. Our study highlights the therapeutic potential of BBR to be used as an antifungal synergist in combination with antifungal drugs against T. asahii infections, especially BBR/AMB combination. Further in vivo studies are needed to validate our findings.     

Molecular Identification and Antifungal Susceptibility of Clinical Isolates of Sporothrix schenckii Complex in Medellin,Colombia

Background

Sporotrichosis is a subcutaneous mycosis that affects humans and other animals. Infection prevails in tropical and subtropical countries. Until a few years ago, it was considered that two varieties of Sporothrix schenckii caused this mycosis, but by applying molecular taxonomic markers, it has been demonstrated that there are several cryptic species within S. schenckii complex which varies in susceptibility, virulence, and geographic distribution.

Objective

This study aimed to identify the clinical isolates of Sporothrix spp. from patients with sporotrichosis in Medellin, Colombia, using two markers and to evaluate the in vitro susceptibility to itraconazole.

Methods

Thirty-four clinical isolates of Sporothrix spp. from Colombia, three from Mexico, and one from Guatemala were identified through sequencing of the noncoding region ITS-1?+?5.8SDNAr?+?ITS-2 and of the fragment containing exons 3 and 4 of the β-tubulin gene. Clinical isolate sequences were compared with GenBank reference sequences using the BLASTN tool, and then, phylogenetic analysis was performed. Besides, the in vitro susceptibility to itraconazole was evaluated by determining the minimum inhibitory concentrations according to the CLSI M38-A2 method.

Results

Clinical isolates were identified by morphology as Sporothrix spp. Using the molecular markers, ITS and β-tubulin, isolates were identified as S. schenckii sensu stricto (25) and Sporothrix globosa (13). Susceptibility to itraconazole was variable among clinical isolates.

Conclusion

This is the first scientific publication that identifies species that cause sporotrichosis in Colombia, along with the antifungal susceptibility to itraconazole.

     

Discrepancies between MIC and MLC values of amphotericin B against isolates ofAspergillus species

There is little information addressing the phenomena of discrepancy between minimal inhibitory concentrations (MIC) and minimal lethal concentrations (MLC) values of amphotericin B (AMB) to clinical isolates of fungi. This study assessed in vitro activity of AMB against 70 clinical isolates of aspergilli: 30 strains ofAspergillus fumigatus, 20 strains ofAspergillus flavus and 20 strains ofAspergillus niger. Susceptibility tests were accomplished using a macro broth dilution procedure, with special emphasis on ascertainment of MLCs. AMB exhibited low MIC values against all clinical isolates. While we did not identify any AMB resistant isolates among 70Aspergillus spp. studied as judged by MIC levels, analysis of the data demonstrated a clear discrepancy between the MIC and MLC levels of AMB obtained against clinical isolates ofAspergillus spp. The MLC values of AMB were significantly higher than the MIC values with MIC 50 and MIC 90 of 0.29 and 0.5 µg/ml, respectively, at the second reading time, and MLC 50 and MLC 90 of 2.31 and 9.24 µg/ml, respectively (p<0.001). Additionally, minimal lethal concentrations in 36/70 (51%) of aspergillal isolates studied produced drug concentrations above those which can usually be sustained in patient plasma or tissue.     

Oxacillinases and antimicrobial susceptibility of Ralstonia pickettii from pharmaceutical water systems in Croatia

This study evaluated antibiotic susceptibility and presence of bla_OXA22 and bla_OXA60 genes in 81 isolates of Ralstonia pickettii obtained from different purified and ultra-pure water systems in two different geographical areas of Croatia. E-test and disc diffusion test were performed to determine antibiotic susceptibility. Polymerase chain reaction was applied to detect genes encoding OXA-22 and OXA-60 oxacillinases previously identified in R. pickettii. The isolates were genotyped by pulsed-field gel electrophoresis. The results revealed variable susceptibility/resistance profiles. Our isolates exhibited high susceptibility rates to ceftriaxone, cefotaxime, piperacillin-tazobactam, ciprofloxacin, imipenem, cefepime and in lesser extent to ceftazidime. High rates of susceptibility were also observed for sulphamethoxazole-trimethoprim and piperacillin. High resistance rates were noticed for ticarcillin-clavulanate, aztreonam and meropenem, as well as for all aminoglycosides tested. Modified Hodge test was positive in 51·9% strains, indicating production of carbapenemases. bla_OXA22 and bla_OXA60 genes were detected in 37·0 and 80·3% strains, respectively. Pulsed-field gel electrophoresis identified three major clusters containing subclusters. R. pickettii should be taken seriously as a possible cause of nosocomial infections to ensure adequate therapy, to prevent the development of resistant strains and to try to reduce the possibility of R. pickettii surviving in clean and ultra clean water systems.     

Enhanced activity of antifungal drugs using natural phenolics against yeast strains of Candida and Cryptococcus

Aims: Determine whether certain, natural phenolic compounds enhance activity of commercial antifungal drugs against yeast strains of Candida and Cryptococcus neoformans. Methods and Results: Twelve natural phenolics were examined for fungicidal activity against nine reference strains of Candida and one of C. neoformans. Six compounds were selected for synergistic enhancement of antifungal drugs, amphotericin B (AMB), fluconazole (FLU) and itraconazole (ITR). Matrix assays of phenolic and drug combinations conducted against one reference strain, each, of Candida albicans and C. neoformans showed cinnamic and benzoic acids, thymol, and 2,3‐ and 2,5‐dihydroxybenzaldehydes (‐DBA) had synergistic interactions depending upon drug and yeast strain. 2,5‐DBA was synergistic with almost all drug and strain combinations. Thymol was synergistic with all drugs against Ca. albicans and with AMB in C. neoformans. Combinations of benzoic acid or thymol with ITR showed highest synergistic activity. Of 36 combinations of natural product and drug tested, none were antagonistic. Conclusions: Relatively nontoxic natural products can synergistically enhance antifungal drug activity, in vitro. Significance and Impact of the Study: This is a proof‐of‐concept, having clinical implications. Natural chemosensitizing agents could lower dosages needed for effective chemotherapy of invasive mycoses. Further studies against clinical yeast strains and use of animal models are warranted.     

Antagonism against Rhizoctonia solani and fungitoxic metabolite production by some Penicillium isolates

A number of Penicillium isolates were recovered in association to Rhizoctonia solani strains pathogenic on tobacco and from soil on plates pre-colonized by the pathogen itself. Their antagonism toward R. solaniAG-2-1 was evaluated in dual cultures in vitro. Inhibition of growth was evident to some extent in most pairings, while hyphal interactions referable to mycoparasitic relationships were not observed. However, the occurrence of plasmolysis and/or vacuolisation and the induction of monilioid cells were indicative of the release of bioactive compounds. Therefore, production of fungitoxic metabolites was tested by adding concentrated culture filtrates of each Penicillium isolate to the growth medium of R. solani. Complete and lasting inhibition was incited by culture filtrates of some isolates belonging to P. brevicompactum, P. expansum, and P. pinophilum. Three purified compounds, respectively mycophenolic acid, patulin and 3-O-methylfunicone, which were extracted from culture filtrates, were able to inhibit R. solani in vitro. Their production was also detected in dual cultures of the same Penicilliumstrains with R. solani prepared in sterilized soil and when the Penicilliumstrains were cultured directly on R. solani mycelium harvested from liquid cultures. The possible role of such metabolites in antagonism of the above-mentioned Penicilliumspecies against R. solani is discussed.     

Fungicidal activity of the human peptide hepcidin 20 alone or in combination with other antifungals against Candida glabrata isolates

Candida glabrata infections are often difficult to eradicate due to the intrinsically low susceptibility to azoles of this species. In addition, C. glabrata has also been shown to be insensitive to several cationic peptides, which have been shown to be promising novel therapeutic candidates for the treatment of fungal infection. In this study, the in vitro fungicidal activity of the human cationic peptide hepcidin 20 (Hep-20) was evaluated against clinical isolates of C. glabrata with different levels of fluconazole susceptibility. Interestingly, all isolates were susceptible to Hep-20 (100–200 μg/ml) at pH 7.4, whereas the fungicidal effect of the peptide was higher (50 μg/ml) at acidic pH values. In addition, an increased antifungal activity was observed for Hep-20 with amphotericin B and a synergistic effect was demonstrated for the Hep-20/fluconazole and Hep-20/caspofungin combinations.     

Synergistic Antimicrobial Activity of Camellia sinensis and Juglans regia against Multidrug-Resistant Bacteria

Synergistic combinations of antimicrobial agents with different mechanisms of action have been introduced as more successful strategies to combat infections involving multidrug resistant (MDR) bacteria. In this study, we investigated synergistic antimicrobial activity of Camellia sinensis and Juglans regia which are commonly used plants with different antimicrobial agents. Antimicrobial susceptibility of 350 Gram-positive and Gram-negative strains belonging to 10 different bacterial species, was tested against Camellia sinensis and Juglans regia extracts. Minimum inhibitory concentrations (MICs) were determined by agar dilution and microbroth dilution assays. Plant extracts were tested for synergistic antimicrobial activity with different antimicrobial agents by checkerboard titration, Etest/agar incorporation assays, and time kill kinetics. Extract treated and untreated bacteria were subjected to transmission electron microscopy to see the effect on bacterial cell morphology. Camellia sinensis extract showed higher antibacterial activity against MDR S. Typhi, alone and in combination with nalidixic acid, than to susceptible isolates.” We further explore anti-staphylococcal activity of Juglans regia that lead to the changes in bacterial cell morphology indicating the cell wall of Gram-positive bacteria as possible target of action. The synergistic combination of Juglans regia and oxacillin reverted oxacillin resistance of methicillin resistant Staphylococcus aureus (MRSA) strains in vitro. This study provides novel information about antimicrobial and synergistic activity of Camellia sinensis and Juglans regia against MDR pathogens     

Nosocomial infection caused by vancomycin‐susceptible multidrug‐resistant Enterococcus faecalis over a long period in a university hospital in Japan

Compared with other developed countries, vancomycin‐resistant enterococci (VRE) are not widespread in clinical environments in Japan. There have been no VRE outbreaks and only a few VRE strains have sporadically been isolated in our university hospital in Gunma, Japan. To examine the drug susceptibility of Enterococcus faecalis and nosocomial infection caused by non‐VRE strains, a retrospective surveillance was conducted in our university hospital. Molecular epidemiological analyses were performed on 1711 E. faecalis clinical isolates collected in our hospital over a 6‐year period [1998–2003]. Of these isolates, 1241 (72.5%) were antibiotic resistant and 881 (51.5%) were resistant to two or more drugs. The incidence of multidrug resistant E. faecalis (MDR‐Ef) isolates in the intensive care unit increased after enlargement and restructuring of the hospital. The major group of MDR‐Ef strains consisted of 209 isolates (12.2%) resistant to the five drug combination tetracycline/erythromycin/kanamycin/streptomycin/gentamicin. Pulsed‐field gel electrophoresis analysis of the major MDR‐Ef isolates showed that nosocomial infections have been caused by MDR‐Ef over a long period (more than 3 years). Multilocus sequence typing showed that these strains were mainly grouped into ST16 (CC58) or ST64 (CC8). Mating experiments suggested that the drug resistances were encoded on two conjugative transposons (integrative conjugative elements), one encoded tetracycline‐resistance and the other erythromycin/kanamycin/streptomycin/gentamicin‐resistance. To our knowledge, this is the first report of nosocomial infection caused by vancomycin‐susceptible MDR‐Ef strains over a long period in Japan.     

Accuracy of the disk method for determining antimicrobic susceptibility of common Gram-negative bacilli

A standardized disk susceptibility test was evaluated by comparing results with minimal inhibitory concentrations obtained with agar dilution methods. The agar overlay method was used to test 152 Gram-negative bacilli against eight different antimicrobial agents. One to 3% of the isolates were resistant to an antimicrobic by the MIC method, but appeared to be susceptible by the disk method. Most very major discrepancies involved disk tests withProteus sp., a microorganism notoriously difficult to test reproducibly.Serratia sp. vs. the polymyxins andKlebsiella sp. vs. nitrofurantoin accounted for most other major discrepancies. With other microorganism-drug combinations, the disk test was a reasonably accurate technique for classifying bacteria into resistant or susceptible categories. Gentamicin disk tests were unsatisfactory, but when an intermediate zone category of 13–16 mm was applied, the false susceptible test results were reduced to 2.6%. Intermediate zone sizes were obtained with 6% of the disk tests; most of those isolates were resistant or susceptible but not intermediate in susceptibility. About 11% of the strains had intermediate MICs (5–20% with different drugs), but most of those strains were fully susceptible by the disk technique. *** DIRECT SUPPORT *** A01R4011 00007     

The synergy of honokiol and fluconazole against clinical isolates of azole‐resistant Candida albicans

Aims: To evaluate the interaction of fluconazole (FLC) and honokiol (HNK) in vitro and vivo against azole‐resistant (azole‐R) clinical isolates of Candida albicans. Methods and Results: A checkerboard microdilution method was used to study the in vitro interaction of FLC and HNK in 24 azole‐R clinical isolates of C. albicans. In vivo antifungal activity was performed to further analyse the interaction between FLC and HNK. In the in vitro study, synergism was observed in all 24 FLC‐resistant strains tested as determined by fractional inhibitory concentration index (FICI), and in 22 strains by ΔE models. No antagonistic activity was observed in any of the strains tested. These positive interactions were also confirmed by using the time‐killing test for the selected strain C. albicans YL371, which shows strong susceptible to the combination of HNK and FLC. In the in vivo study, the mice with candidiasis were treated successfully by a combination therapy of HNK with FLC, the results showed a decrease of the colony forming unit in infected and treated animals compared to the controls, at the conditions of the treatment used in this study. Conclusions: Synergistic activity of HNK and FLC against clinical isolates of FLC‐resistant C. albicans was observed in vitro and in vivo. Significance and Impact of the Study: This report might provide a potential therapeutic method to overcome the problem of drug‐resistance in C. albicans.     

The High Diversity and Variable Susceptibility of Clinically Relevant Acremonium-Like Species in China

Acremonium-like fungi are emerging as important opportunistic pathogens in cutaneous, subcutaneous and serious invasive infections, especially in immunocompromised and debilitated individuals, and Acremonium infections are usually resistant to antifungal therapy. Several molecular studies have demonstrated that many species in the genus Acremonium are polyphyletic, and currently, the genus is restricted to the family Bionectriaceae (Hypocreales). Molecular identification and in vitro antifungal susceptibility tests of Acremonium-like fungi isolated from human clinical specimens in China were performed in this study. Three genetic loci: the large subunit ribosomal RNA gene (LSU), ribosomal internal transcribed spacer and elongation factor 1-α (EF1-α), were used to assess their taxonomic position for correct identification among various species. The multilocus study of twenty-eight strains showed that these strains were distributed in three main lineages: egyptiacum, Cordycipitaceae and Sarocladium; Acremonium egyptiacum and Sarocladium kiliense were the main species of these strains, and three isolates were too phylogenetically distant to be considered undescribed species. Relatively low minimum inhibitory concentrations (MICs) of 0.25–2 and 0.031–0.5 μg/mL were found for voriconazole and terbinafine for most species, respectively. Varied antifungal activities of ciclopirox olamine, amorolfine and posaconazole were found in our study. However, no antifungal effect of sertaconazole, itraconazole or fluconazole was observed against most strains. This is the first study on Acremonium-like species diversity by multilocus sequence analyses and antifungal susceptibility of clinically relevant isolates in China.

     

Cross‐species discovery of syncretic drug combinations that potentiate the antifungal fluconazole

Resistance to widely used fungistatic drugs, particularly to the ergosterol biosynthesis inhibitor fluconazole, threatens millions of immunocompromised patients susceptible to invasive fungal infections. The dense network structure of synthetic lethal genetic interactions in yeast suggests that combinatorial network inhibition may afford increased drug efficacy and specificity. We carried out systematic screens with a bioactive library enriched for off‐patent drugs to identify compounds that potentiate fluconazole action in pathogenic Candida and Cryptococcus strains and the model yeast Saccharomyces. Many compounds exhibited species‐ or genus‐specific synergism, and often improved fluconazole from fungistatic to fungicidal activity. Mode of action studies revealed two classes of synergistic compound, which either perturbed membrane permeability or inhibited sphingolipid biosynthesis. Synergistic drug interactions were rationalized by global genetic interaction networks and, notably, higher order drug combinations further potentiated the activity of fluconazole. Synergistic combinations were active against fluconazole‐resistant clinical isolates and an in vivo model of Cryptococcus infection. The systematic repurposing of approved drugs against a spectrum of pathogens thus identifies network vulnerabilities that may be exploited to increase the activity and repertoire of antifungal agents.