The Synergistic Effect of Azoles and Fluoxetine against Resistant Candida albicans Strains Is Attributed to Attenuating Fungal Virulence

ABSTRACTThis study evaluated the synergistic effects of the selective serotonin reuptake inhibitor, fluoxetine, in combination with azoles againstCandida albicansbothin vitroandin vivoand explored the underlying mechanism. MICs, sessile MICs, and time-kill curves were determined for resistantC. albicans.Galleria mellonellawas used as a nonvertebrate model for determining the efficacy of the drug combinations againstC. albicansin vivo. For the mechanism study, gene expression levels of theSAPgene family were determined by reverse transcription (RT)-PCR, and extracellular phospholipase activities were detectedin vitroby the egg yolk agar method. The combinations resulted in synergistic activity againstC. albicansstrains, but the same effect was not found for the non-albicans Candidastrains. For the biofilms formed over 4, 8, and 12 h, synergism was seen for the combination of fluconazole and fluoxetine. In addition, the time-kill curves confirmed the synergism dynamically. The results of theG. mellonellastudies agreed with thein vitroanalysis. In the mechanism study, we observed that fluconazole plus fluoxetine caused downregulation of the gene expression levels ofSAP1toSAP4and weakened the extracellular phospholipase activities of resistantC. albicans. The combinations of azoles and fluoxetine showed synergistic effects against resistantC. albicansmay diminish the virulence properties ofC. albicans.

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Effects of Echinocandins in Combination with Nikkomycin Z against Invasive Candida albicans Bloodstream Isolates and the fks Mutants

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00619-17 ◽

2017 ◽

Vol 61 (11) ◽

Cited By ~ 6

Author(s):

Yuk-Yam Cheung ◽

Mamie Hui

Keyword(s):

Candida Albicans ◽

Therapeutic Potential ◽

Synergistic Effects ◽

Rank Test ◽

Content Type ◽

Log Rank Test ◽

Echinocandin Resistance ◽

Nikkomycin Z

ABSTRACT We evaluated the in vitro and in vivo effects of nikkomycin Z combined with an echinocandin (anidulafungin or micafungin) against two Candida albicans isolates and their lab-derived echinocandin-resistant fks mutants with FKS1 S645Y and FKS1 S645P. Synergistic effects were observed in all tested strains (fractional inhibitory concentration index, <0.5). Enhanced survival was observed in an immunocompromised murine model (log-rank test, P < 0.02). Our study demonstrated the therapeutic potential of nikkomycin Z-echinocandin combinations in managing echinocandin resistance.

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Divergent Targets of Candida albicans Biofilm Regulator Bcr1In VitroandIn Vivo

Eukaryotic Cell ◽

10.1128/ec.00103-12 ◽

2012 ◽

Vol 11 (7) ◽

pp. 896-904 ◽

Cited By ~ 72

Author(s):

Saranna Fanning ◽

Wenjie Xu ◽

Norma Solis ◽

Carol A. Woolford ◽

Scott G. Filler ◽

...

Keyword(s):

Gene Expression ◽

Candida Albicans ◽

Stress Response ◽

Growth Conditions ◽

Gene Expression Measurement ◽

Content Type ◽

New Genes

ABSTRACTCandida albicansis a causative agent of oropharyngeal candidiasis (OPC), a biofilm-like infection of the oral mucosa. Biofilm formation depends upon theC. albicanstranscription factor Bcr1, and previous studies indicate that Bcr1 is required for OPC in a mouse model of infection. Here we have used a nanoString gene expression measurement platform to elucidate the role of Bcr1 in OPC-related gene expression. We chose for assays a panel of 134 genes that represent a range of morphogenetic and cell cycle functions as well as environmental and stress response pathways. We assayed gene expression in whole infected tongue samples. The results sketch a portrait ofC. albicansgene expression in which numerous stress response pathways are activated during OPC. This one set of experiments identifies 64 new genes with significantly altered RNA levels during OPC, thus increasing substantially the number of known genes in this expression class. Thebcr1Δ/Δ mutant had a much more limited gene expression defect during OPC infection than previously reported forin vitrogrowth conditions. Among major functional Bcr1 targets, we observed thatALS3was Bcr1 dependentin vivowhileHWP1was not. We used null mutants and complemented strains to verify that Bcr1 and Hwp1 are required for OPC infection in this model. The role of Als3 is transient and mild, though significant. Our findings suggest that the versatility ofC. albicansas a pathogen may reflect its ability to persist in the face of multiple stresses and underscore that transcriptional circuitry during infection may be distinct from that detailed duringin vitrogrowth.

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Combating antimicrobial resistance using antimicrobial combination therapy and β–lactamase inhibitors

The Journal of Infection in Developing Countries ◽

10.3855/jidc.10099 ◽

2018 ◽

Vol 12 (02.1) ◽

pp. 14S

Author(s):

Bassam El-Hafi ◽

Sari Shawki Rasheed ◽

Noor A Salloum ◽

Antoine Abou Fayad ◽

George F Araj ◽

...

Keyword(s):

Gene Expression ◽

Antimicrobial Resistance ◽

Combination Therapy ◽

Bacterial Infections ◽

Antimicrobial Agents ◽

Treatment Approaches ◽

Expression Levels ◽

Gene Expression Levels

Introduction: The range of antimicrobial agents used to treat bacterial infections is becoming limited with the constant increase in antimicrobial resistance (AMR). Several genetic factors underlie AMR, including β-lactamase-encoding genes such as blaCTXM-15 that confers resistance to third-generation cephalosporins, and blaOXA-48, blaNDM-1, and blaKPC-2 that confer resistance to carbapenems. Remaining treatment approaches for such resistant infections include antimicrobial combination therapy and the use of β-lactamase inhibitors. This study assesses the molecular effects of such treatment approaches on antimicrobial resistant Enterobacteriaceae clinical isolates in vitro and in vivo. Methodology: Nine clinical Enterobacteriaceae isolates were included in the study. One harboring blaCTXM-15, one harboring blaOXA-48, one harboring blaKPC-2, two harboring blaNDM-1 and blaCTXM-15, and four harboring blaOXA-48 and blaCTXM-15. Minimal inhibitory concentrations were determined for carbapenems with β-lactamase inhibitors: avibactam, Ca-EDTA, and relebactam. Synergism between antibiotic combinations was determined by double disc diffusion when using colistin with several antibiotics. In vitro and in vivo gene expression levels were done on these combinations with and without inhibitors. Results: The use of meropenem, imipenem, and ertapenem with the selected β-lactamase inhibitors restored isolate susceptibility in 100%, 87.5%, and 25% of the cases, respectively. Antimicrobial synergism was mostly detected between colistin and meropenem, fosfomycin, or tigecycline. Survival studies revealed the survival of most mice receiving antimicrobial combination therapy with inhibitors as compared to the controls. Overall gene expression levels of resistance genes were variable depending on treatment. Conclusions: The threat of antibiotic resistant bacterial infections remains viable; however, different approaches to therapy are available.

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Effects of Phage Endolysin SAL200 Combined with Antibiotics on Staphylococcus aureus Infection

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00731-18 ◽

2018 ◽

Vol 62 (10) ◽

Cited By ~ 17

Author(s):

Nak-Hyun Kim ◽

Wan Beom Park ◽

Jeong Eun Cho ◽

Yoon Jeong Choi ◽

Su Jin Choi ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Bacterial Infections ◽

Galleria Mellonella ◽

Synergistic Effects ◽

Splenic Tissue ◽

Bacterial Density ◽

Content Type ◽

Time Kill

ABSTRACT Phages and their derivatives are increasingly being reconsidered for use in the treatment of bacterial infections due to the rising rates of antibiotic resistance. We assessed the antistaphylococcal effect of the endolysin SAL200 in combination with standard-of-care (SOC) antibiotics. The activity of SAL200 when it was combined with SOC antibiotics was assessed in vitro by checkerboard and time-kill assays and in vivo with murine bacteremia and Galleria mellonella infection models. SAL200 reduced the SOC antibiotic MICs and showed a ≥3-log10-CFU/ml reduction of Staphylococcus aureus counts within 30 min in time-kill assays. Combinations of SAL200 and SOC antibiotics achieved a sustained decrease of >2 log10 CFU/ml. SAL200 significantly lowered the blood bacterial density within 1 h by >1 log10 CFU/ml in bacteremic mice (P < 0.05 versus untreated mice), and SAL200 and SOC antibiotic combinations achieved the lowest levels of bacteremia. The bacterial density in splenic tissue at 72 h postinfection was the lowest in mice treated with SAL200 and SOC antibiotic combinations. SAL200 combined with SOC antibiotics also improved Galleria mellonella larva survival at 96 h postinfection. The combination of the phage endolysin SAL200 with SOC antistaphylococcal antibiotics showed synergistic effects in vitro and in vivo. The combination of SAL200 with SOC antibiotics could help in the treatment of difficult-to-treat S. aureus infections.

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Regulatory Role of Glycerol in Candida albicans Biofilm Formation

mBio ◽

10.1128/mbio.00637-12 ◽

2013 ◽

Vol 4 (2) ◽

Cited By ~ 40

Author(s):

Jigar V. Desai ◽

Vincent M. Bruno ◽

Shantanu Ganguly ◽

Ronald J. Stamper ◽

Kaitlin F. Mitchell ◽

...

Keyword(s):

Gene Expression ◽

Candida Albicans ◽

Cell Surface ◽

Biofilm Formation ◽

Regulatory Role ◽

Content Type ◽

Upregulated Genes ◽

Implanted Devices

ABSTRACTBiofilm formation byCandida albicanson medically implanted devices poses a significant clinical challenge. Here, we compared biofilm-associated gene expression in two clinicalC. albicansisolates, SC5314 and WO-1, to identify shared gene regulatory responses that may be functionally relevant. Among the 62 genes most highly expressed in biofilms relative to planktonic (suspension-grown) cells, we were able to recover insertion mutations in 25 genes. Twenty mutants had altered biofilm-related properties, including cell substrate adherence, cell-cell signaling, and azole susceptibility. We focused on one of the most highly upregulated genes in our biofilm proles,RHR2, which specifies the glycerol biosynthetic enzyme glycerol-3-phosphatase. Glycerol is 5-fold-more abundant in biofilm cells than in planktonic cells, and anrhr2Δ/Δ strain accumulates 2-fold-less biofilm glycerol than does the wild type. Underin vitroconditions, therhr2Δ/Δ mutant has reduced biofilm biomass and reduced adherence to silicone. Therhr2Δ/Δ mutant is also severely defective in biofilm formationin vivoin a rat catheter infection model. Expression profiling indicates that therhr2Δ/Δ mutant has reduced expression of cell surface adhesin genesALS1,ALS3, andHWP1, as well as many other biofilm-upregulated genes. Reduced adhesin expression may be the cause of therhr2Δ/Δ mutant biofilm defect, because overexpression ofALS1,ALS3, orHWP1restores biofilm formation ability to the mutantin vitroandin vivo. Our findings indicate that internal glycerol has a regulatory role in biofilm gene expression and that adhesin genes are among the main functional Rhr2-regulated genes.IMPORTANCECandida albicansis a major fungal pathogen, and infection can arise from the therapeutically intractable biofilms that it forms on medically implanted devices. It stands to reason that genes whose expression is induced during biofilm growth will function in the process, and our analysis of 25 such genes confirms that expectation. One gene is involved in synthesis of glycerol, a small metabolite that we find is abundant in biofilm cells. The impact of glycerol on biofilm formation is regulatory, not solely metabolic, because it is required for expression of numerous biofilm-associated genes. Restoration of expression of three of these genes that specify cell surface adhesins enables the glycerol-synthetic mutant to create a biofilm. Our findings emphasize the significance of metabolic pathways as therapeutic targets, because their disruption can have both physiological and regulatory consequences.

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In Vitro Synergy and In Vivo Activity of Tigecycline-Ciprofloxacin Combination Therapy against Vibrio vulnificus Sepsis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00310-19 ◽

2019 ◽

Vol 63 (10) ◽

Author(s):

Seong Eun Kim ◽

Hee Kyung Kim ◽

Su-Mi Choi ◽

Yohan Yu ◽

Uh Jin Kim ◽

...

Keyword(s):

Survival Rate ◽

Mortality Rate ◽

Combination Therapy ◽

Combination Treatment ◽

Vibrio Vulnificus ◽

Antibiotic Regimen ◽

Content Type ◽

Time Kill

ABSTRACT The mortality rate associated with Vibrio vulnificus sepsis remains high. An in vitro time-kill assay revealed synergism between tigecycline and ciprofloxacin. The survival rate was significantly higher in mice treated with tigecycline plus ciprofloxacin than in mice treated with cefotaxime plus minocycline. Thus, combination treatment with tigecycline-ciprofloxacin may be an effective novel antibiotic regimen for V. vulnificus sepsis.

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The Novel Arylamidine T-2307 MaintainsIn VitroandIn VivoActivity against Echinocandin-Resistant Candida albicans

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04228-14 ◽

2014 ◽

Vol 59 (2) ◽

pp. 1341-1343 ◽

Cited By ~ 14

Author(s):

Nathan P. Wiederhold ◽

Laura K. Najvar ◽

Annette W. Fothergill ◽

Rosie Bocanegra ◽

Marcos Olivo ◽

...

Keyword(s):

Body Weight ◽

Candida Albicans ◽

Invasive Candidiasis ◽

Placebo Control ◽

The Novel ◽

Content Type ◽

Fungal Burden ◽

Potential Use

ABSTRACTWe evaluated thein vitroandin vivoactivities of the investigational arylamidine T-2307 against echinocandin-resistantCandida albicans. T-2307 demonstrated potentin vitroactivity, and daily subcutaneous doses between 0.75 and 6 mg/kg of body weight significantly improved survival and reduced fungal burden compared to placebo control and caspofungin (10 mg/kg/day) in mice with invasive candidiasis caused by an echinocandin-resistant strain. Thus, T-2307 may have potential use in the treatment of echinocandin-resistantC. albicansinfections.

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Antimicrobial Photodynamic Inactivation Inhibits Candida albicans Virulence Factors and ReducesIn VivoPathogenicity

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01451-12 ◽

2012 ◽

Vol 57 (1) ◽

pp. 445-451 ◽

Cited By ~ 41

Author(s):

Ilka Tiemy Kato ◽

Renato Araujo Prates ◽

Caetano Padial Sabino ◽

Beth Burgwyn Fuchs ◽

George P. Tegos ◽

...

Keyword(s):

Candida Albicans ◽

Virulence Factors ◽

Sodium Dodecyl ◽

Systemic Infection ◽

Tube Formation ◽

Photodynamic Inactivation ◽

Content Type ◽

Daughter Cells

ABSTRACTThe objective of this study was to evaluate whetherCandida albicansexhibits altered pathogenicity characteristics following sublethal antimicrobial photodynamic inactivation (APDI) and if such alterations are maintained in the daughter cells.C. albicanswas exposed to sublethal APDI by using methylene blue (MB) as a photosensitizer (0.05 mM) combined with a GaAlAs diode laser (λ 660 nm, 75 mW/cm2, 9 to 27 J/cm2).In vitro, we evaluated APDI effects onC. albicansgrowth, germ tube formation, sensitivity to oxidative and osmotic stress, cell wall integrity, and fluconazole susceptibility.In vivo, we evaluatedC. albicanspathogenicity with a mouse model of systemic infection. Animal survival was evaluated daily. Sublethal MB-mediated APDI reduced the growth rate and the ability ofC. albicansto form germ tubes compared to untreated cells (P< 0.05). Survival of mice systemically infected withC. albicanspretreated with APDI was significantly increased compared to mice infected with untreated yeast (P< 0.05). APDI increasedC. albicanssensitivity to sodium dodecyl sulfate, caffeine, and hydrogen peroxide. The MIC for fluconazole forC. albicanswas also reduced following sublethal MB-mediated APDI. However, none of those pathogenic parameters was altered in daughter cells ofC. albicanssubmitted to APDI. These data suggest that APDI may inhibit virulence factors and reducein vivopathogenicity ofC. albicans. The absence of alterations in daughter cells indicates that APDI effects are transitory. The MIC reduction for fluconazole following APDI suggests that this antifungal could be combined with APDI to treatC. albicansinfections.

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Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Applied and Environmental Microbiology ◽

10.1128/aem.02582-16 ◽

2016 ◽

Vol 83 (5) ◽

Cited By ~ 25

Author(s):

Min-Jeong Kim ◽

Hyun-Gyun Yuk

Keyword(s):

Gene Expression ◽

Gene Regulation ◽

Light Emitting Diode ◽

Dna Oxidation ◽

Uptake System ◽

Antibacterial Mechanism ◽

Content Type ◽

Light Emitting ◽

Expression Levels ◽

Gene Expression Levels

ABSTRACT The aim of this study was to elucidate the antibacterial mechanism of 405 ± 5-nm light-emitting diode (LED) illumination against Salmonella at 4°C in phosphate-buffered saline (PBS) by determining endogenous coproporphyrin content, DNA oxidation, damage to membrane function, and morphological change. Gene expression levels, including of oxyR, recA, rpoS, sodA, and soxR, were also examined to understand the response of Salmonella to LED illumination. The results showed that Salmonella strains responded differently to LED illumination, revealing that S. enterica serovar Enteritidis (ATCC 13076) and S. enterica subsp. enterica serovar Saintpaul (ATCC 9712) were more susceptible and resistant, respectively, than the 16 other strains tested. There was no difference in the amounts of endogenous coproporphyrin in the two strains. Compared with that in nonilluminated cells, the DNA oxidation levels in illuminated cells increased. In illuminated cells, we observed a loss of efflux pump activity, damage to the glucose uptake system, and changes in membrane potential and integrity. Transmission electron microscopy revealed a disorganization of chromosomes and ribosomes due to LED illumination. The levels of the five genes measured in the nonilluminated and illuminated S. Saintpaul cells were upregulated in PBS at a set temperature of 4°C, indicating that increased gene expression levels might be due to a temperature shift and nutrient deficiency rather than to LED illumination. In contrast, only oxyR in S. Enteritidis cells was upregulated. Thus, different sensitivities of the two strains to LED illumination were attributed to differences in gene regulation. IMPORTANCE Bacterial inactivation using visible light has recently received attention as a safe and environmentally friendly technology, in contrast with UV light, which has detrimental effects on human health and the environment. This study was designed to understand how 405 ± 5-nm light-emitting diode (LED) illumination kills Salmonella strains at refrigeration temperature. The data clearly demonstrated that the effectiveness of LED illumination on Salmonella strains depended highly on the serotype and strain. Our findings also revealed that its antibacterial mechanism was mainly attributed to DNA oxidation and a loss of membrane functions rather than membrane lipid peroxidation, which has been proposed by other researchers who studied the antibacterial effect of LED illumination by adding exogenous photosensitizers, such as chlorophyllin and hypericin. Therefore, this study suggests that the detailed antibacterial mechanisms of 405-nm LED illumination without additional photosensitizers may differ from that by exogenous photosensitizers. Furthermore, a change in stress-related gene regulation may alter the susceptibility of Salmonella cells to LED illumination at refrigeration temperature. Thus, our study provides new insights into the antibacterial mechanism of 405 ± 5-nm LED illumination on Salmonella cells.

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