Quinacrine Inhibits Candida albicans Growth and Filamentation at Neutral pH

Candida albicans is a common cause of catheter-related bloodstream infections (CR-BSI), in part due to its strong propensity to form biofilms. Drug repurposing is an approach that might identify agents that are able to overcome antifungal drug resistance within biofilms. Quinacrine (QNC) is clinically active against the eukaryotic protozoan parasites Plasmodium and Giardia. We sought to investigate the antifungal activity of QNC against C. albicans biofilms. C. albicans biofilms were incubated with QNC at serially increasing concentrations (4 to 2,048 μg/ml) and assessed using a 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay in a static microplate model. Combinations of QNC and standard antifungals were assayed using biofilm checkerboard analyses. To define a mechanism of action, QNC was assessed for the inhibition of filamentation, effects on endocytosis, and pH-dependent activity. High-dose QNC was effective for the prevention and treatment of C. albicans biofilms in vitro. QNC with fluconazole had no interaction, while the combination of QNC and either caspofungin or amphotericin B demonstrated synergy. QNC was most active against planktonic growth at alkaline pH. QNC dramatically inhibited filamentation. QNC accumulated within vacuoles as expected and caused defects in endocytosis. A tetracycline-regulated VMA3 mutant lacking vacuolar ATPase (V-ATPase) function demonstrated increased susceptibility to QNC. These experiments indicate that QNC is active against C. albicans growth in a pH-dependent manner. Although QNC activity is not biofilm specific, QNC is effective in the prevention and treatment of biofilms. QNC antibiofilm activity likely occurs via several independent mechanisms: vacuolar alkalinization, inhibition of endocytosis, and impaired filamentation. Further investigation of QNC for the treatment and prevention of biofilm-related Candida CR-BSI is warranted.     

In Vitro Analysis of Finasteride Activity against Candida albicans Urinary Biofilm Formation and Filamentation

Candida albicans is the 3rd most common cause of catheter-associated urinary tract infections, with a strong propensity to form drug-resistant catheter-related biofilms. Due to the limited efficacy of available antifungals against biofilms, drug repurposing has been investigated in order to identify novel agents with activities against fungal biofilms. Finasteride is a 5-α-reductase inhibitor commonly used for the treatment of benign prostatic hyperplasia, with activity against human type II and III isoenzymes. We analyzed the Candida Genome Database and identified a C. albicans homolog of type III 5-α-reductase, Dfg10p, which shares 27% sequence identity and 41% similarity to the human type III 5-α-reductase. Thus, we investigated finasteride for activity against C. albicans urinary biofilms, alone and in combination with amphotericin B or fluconazole. Finasteride alone was highly effective in the prevention of C. albicans biofilm formation at doses of ≥16 mg/liter and the treatment of preformed biofilms at doses of ≥128 mg/liter. In biofilm checkerboard analyses, finasteride exhibited synergistic activity in the prevention of biofilm formation in a combination of 4 mg/liter finasteride with 2 mg/liter fluconazole. Finasteride inhibited filamentation, thus suggesting a potential mechanism of action. These results indicate that finasteride alone is highly active in the prevention of C. albicans urinary biofilms in vitro and has synergistic activity in combination with fluconazole. Further investigation of the clinical utility of finasteride in the prevention of urinary candidiasis is warranted.     

Sustained Nitric Oxide-Releasing Nanoparticles Induce Cell Death in Candida albicans Yeast and Hyphal Cells,Preventing Biofilm Formation In Vitro and in a Rodent Central Venous Catheter Model

Candida albicans is a leading nosocomial pathogen. Today, candidal biofilms are a significant cause of catheter infections, and such infections are becoming increasingly responsible for the failure of medical-implanted devices. C. albicans forms biofilms in which fungal cells are encased in an autoproduced extracellular polysaccharide matrix. Consequently, the enclosed fungi are protected from antimicrobial agents and host cells, providing a unique niche conducive to robust microbial growth and a harbor for recurring infections. Here we demonstrate that a recently developed platform comprised of nanoparticles that release therapeutic levels of nitric oxide (NO-np) inhibits candidal biofilm formation, destroys the extracellular polysaccharide matrices of mature fungal biofilms, and hinders biofilm development on surface biomaterials such as the lumen of catheters. We found NO-np to decrease both the metabolic activity of biofilms and the cell viability of C. albicans in vitro and in vivo. Furthermore, flow cytometric analysis found NO-np to induce apoptosis in biofilm yeast cells in vitro. Moreover, NO-np behave synergistically when used in combination with established antifungal drug therapies. Here we propose NO-np as a novel treatment modality, especially in combination with standard antifungals, for the prevention and/or remediation of fungal biofilms on central venous catheters and other medical devices.     

High-Throughput Screening of a Collection of Known Pharmacologically Active Small Compounds for Identification of Candida albicans Biofilm Inhibitors

Candida albicans is the most common etiologic agent of systemic fungal infections with unacceptably high mortality rates. The existing arsenal of antifungal drugs is very limited and is particularly ineffective against C. albicans biofilms. To address the unmet need for novel antifungals, particularly those active against biofilms, we have screened a small molecule library consisting of 1,200 off-patent drugs already approved by the Food and Drug Administration (FDA), the Prestwick Chemical Library, to identify inhibitors of C. albicans biofilm formation. According to their pharmacological applications that are currently known, we classified these bioactive compounds as antifungal drugs, as antimicrobials/antiseptics, or as miscellaneous drugs, which we considered to be drugs with no previously characterized antifungal activity. Using a 96-well microtiter plate-based high-content screening assay, we identified 38 pharmacologically active agents that inhibit C. albicans biofilm formation. These drugs were subsequently tested for their potency and efficacy against preformed biofilms, and we identified three drugs with novel antifungal activity. Thus, repurposing FDA-approved drugs opens up a valuable new avenue for identification and potentially rapid development of antifungal agents, which are urgently needed.     

Modulation of the Substitution Pattern of 5-Aryl-2-Aminoimidazoles Allows Fine-Tuning of Their Antibiofilm Activity Spectrum and Toxicity

We previously synthesized several series of compounds, based on the 5-aryl-2-aminoimidazole scaffold, that showed activity preventing the formation of Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa biofilms. Here, we further studied the activity spectrum of a number of the most active N1- and 2N-substituted 5-aryl-2-aminoimidazoles against a broad panel of biofilms formed by monospecies and mixed species of bacteria and fungi. An N1-substituted compound showed very strong activity against the biofilms formed by Gram-negative and Gram-positive bacteria and the fungus Candida albicans but was previously shown to be toxic against various eukaryotic cell lines. In contrast, 2N-substituted compounds were nontoxic and active against biofilms formed by Gram-negative bacteria and C. albicans but had reduced activity against biofilms formed by Gram-positive bacteria. In an attempt to develop nontoxic compounds with potent activity against biofilms formed by Gram-positive bacteria for application in antibiofilm coatings for medical implants, we synthesized novel compounds with substituents at both the N1 and 2N positions and tested these compounds for antibiofilm activity and toxicity. Interestingly, most of these N1-,2N-disubstituted 5-aryl-2-aminoimidazoles showed very strong activity against biofilms formed by Gram-positive bacteria and C. albicans in various setups with biofilms formed by monospecies and mixed species but lost activity against biofilms formed by Gram-negative bacteria. In light of application of these compounds as anti-infective coatings on orthopedic implants, toxicity against two bone cell lines and the functionality of these cells were tested. The N1-,2N-disubstituted 5-aryl-2-aminoimidazoles in general did not affect the viability of bone cells and even induced calcium deposition. This indicates that modulating the substitution pattern on positions N1 and 2N of the 5-aryl-2-aminoimidazole scaffold allows fine-tuning of both the antibiofilm activity spectrum and toxicity.     

Efficacy of Ethanol against Candida albicans and Staphylococcus aureus Polymicrobial Biofilms

Candida albicans, an opportunistic fungus, and Staphylococcus aureus, a bacterial pathogen, are two clinically relevant biofilm-forming microbes responsible for a majority of catheter-related infections, with such infections often resulting in catheter loss and removal. Not only do these pathogens cause a substantial number of nosocomial infections independently, but also they are frequently found coexisting as polymicrobial biofilms on host and environmental surfaces. Antimicrobial lock therapy is a current strategy to sterilize infected catheters. However, the robustness of this technique against polymicrobial biofilms has remained largely untested. Due to its antimicrobial activity, safety, stability, and affordability, we tested the hypothesis that ethanol (EtOH) could serve as a potentially efficacious catheter lock solution against C. albicans and S. aureus biofilms. Therefore, we optimized the dose and time necessary to achieve killing of both monomicrobial and polymicrobial biofilms formed on polystyrene and silicone surfaces in a static microplate lock therapy model. Treatment with 30% EtOH for a minimum of 4 h was inhibitory for monomicrobial and polymicrobial biofilms, as evidenced by XTT {sodium 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide inner salt} metabolic activity assays and confocal microscopy. Experiments to determine the regrowth of microorganisms on silicone after EtOH treatment were also performed. Importantly, incubation with 30% EtOH for 4 h was sufficient to kill and inhibit the growth of C. albicans, while 50% EtOH was needed to completely inhibit the regrowth of S. aureus. In summary, we have systematically defined the dose and duration of EtOH treatment that are effective against and prevent regrowth of C. albicans and S. aureus monomicrobial and polymicrobial biofilms in an in vitro lock therapy model.     

Fungal β-1,3-Glucan Increases Ofloxacin Tolerance of Escherichia coli in a Polymicrobial E. coli/Candida albicans Biofilm

In the past, biofilm-related research has focused mainly on axenic biofilms. However, in nature, biofilms are often composed of multiple species, and the resulting polymicrobial interactions influence industrially and clinically relevant outcomes such as performance and drug resistance. In this study, we show that Escherichia coli does not affect Candida albicans tolerance to amphotericin or caspofungin in an E. coli/C. albicans biofilm. In contrast, ofloxacin tolerance of E. coli is significantly increased in a polymicrobial E. coli/C. albicans biofilm compared to its tolerance in an axenic E. coli biofilm. The increased ofloxacin tolerance of E. coli is mainly biofilm specific, as ofloxacin tolerance of E. coli is less pronounced in polymicrobial E. coli/C. albicans planktonic cultures. Moreover, we found that ofloxacin tolerance of E. coli decreased significantly when E. coli/C. albicans biofilms were treated with matrix-degrading enzymes such as the β-1,3-glucan-degrading enzyme lyticase. In line with a role for β-1,3-glucan in mediating ofloxacin tolerance of E. coli in a biofilm, we found that ofloxacin tolerance of E. coli increased even more in E. coli/C. albicans biofilms consisting of a high-β-1,3-glucan-producing C. albicans mutant. In addition, exogenous addition of laminarin, a polysaccharide composed mainly of poly-β-1,3-glucan, to an E. coli biofilm also resulted in increased ofloxacin tolerance. All these data indicate that β-1,3-glucan from C. albicans increases ofloxacin tolerance of E. coli in an E. coli/C. albicans biofilm.     

Potent drugs that attenuate anti-Candida albicans activity of fluconazole and their possible mechanisms of action

Fluconazole (FLCZ) is a first-line drug for treating Candida albicans infections, but clinical failure due to reduced sensitivity is a growing concern. Our previous study suggested that certain drug combinations pose a particular challenge in potently reducing FLCZ's anti-C. albicans activity, and cyclooxygenase inhibitors formed the major group of these attenuating drugs in combination with FLCZ. In this study, we examined the effects of diclofenac sodium (DFNa) and related compounds in combination with FLCZ against C. albicans, and investigated their possible mechanisms of interaction. DFNa, ibuprofen, and omeprazole elevated the minimum inhibitory concentration (MIC) of FLCZ by 8-, 4-, and 4-fold, respectively; however, loxoprofen sodium and celecoxib did not. An analogue of DFNa, 2,6-dichlorodiphenylamine, also elevated the MIC by 4-fold. Gene expression analysis revealed that diclofenac sodium induced CDR1 efflux pump activity, but not CDR2 activity. In addition, an efflux pump CDR1 mutant, which was manipulated to not be induced by DFNa, showed less elevation of MIC compared to that shown by the wild type. Therefore, DFNa and related compounds are potent factors for reducing the sensitivity of C. albicans to FLCZ partly via induction of an efflux pump. Although it is not known whether such antagonism is relevant to the clinical treatment failure observed, further investigation of the molecular mechanisms underlying the reduction of FLCZ's anti-C. albicans activity is expected to promote safer and more effective use of the drug.     

Efficacy of liposomal amphotericin B against four species of Candida biofilms in an experimental mouse model of intravascular catheter infection

The formation of Candida biofilms on implanted medical devices is crucial to the development of infections and an important clinical problem because of elevated resistance to antifungals. The aim of this study was to compare the in vitro activity of liposomal amphotericin B (L-AMB) and micafungin (MCFG) against four species of Candida biofilms, and the efficacy of systemic plus lock therapy with L-AMB and MCFG in a Candida biofilm-associated catheter infection model. An XTT-reduction assay was used to measure the metabolic activity of the biofilms to evaluation of in vitro antibiofilm activity. MCFG had better in vitro activity than L-AMB against Candida glabrata biofilms, whereas L-AMB had better activity than MCFG against Candida albicans and Candida tropicalis biofilms. L-AMB and MCFG had comparable efficacy against Candida parapsilosis biofilms. In an in vitro lock therapy model, 2 mg/ml L-AMB, unlike 2 mg/ml MCFG, significantly reduced the metabolic activity of all the strains of biofilms by >96%. Systemic and intraluminal lock treatment with L-AMB for 3-days resulted in more than about 2 log₁₀ reduction of Candida compared with that of systemic treatment and the control group in the C. albicans SP-20012, C. glabrata SP-20040, C. glabrata SP-20131, C. parapsilosis SP-20137, and C. tropicalis SP-20047 infection models. L-AMB was more effective at eradicating Candida biofilms in 3-day course of systemic and lock therapy than MCFG. L-AMB may be useful for the treatment of catheter-related Candida biofilm infections, but this finding will need to be confirmed by further studies including a long treatment duration.     

In vitro time-kill kinetics of dalbavancin against Staphylococcus spp. biofilms over prolonged exposure times

Staphylococcus aureus and Staphylococcus epidermidis are leading pathogens of biofilm-related infections and represent the most common cause of osteomyelitis and biomedical implants infections. Biofilm-related infections usually require long-term antibiotic treatment, often associated to surgical interventions. Dalbavancin is a newer lipoglycopeptide approved for the treatment of acute skin and skin-structure infections caused by Gram-positive pathogens. In addition, dalbavancin has recently been considered as a potential option for the treatment of staphylococcal osteomyelitis and orthopedic implant infections.In this study, time-kill kinetics of dalbavancin against S. aureus and S. epidermidis biofilms were determined over prolonged exposure times (up to 7 days), using both a standardized biofilm susceptibility model and biofilms grown onto relevant orthopedic biomaterials (i.e. titanium and cobalt-chrome disks). Dalbavancin (at concentrations achievable in bone and articular tissue) showed a potent activity against established staphylococcal biofilms in both tested models, and was overall superior to the comparator vancomycin.     

Species-Specific and Drug-Specific Differences in Susceptibility of Candida Biofilms to Echinocandins: Characterization of Less Common Bloodstream Isolates

Candida species other than Candida albicans are increasingly recognized as causes of biofilm-associated infections. This is a comprehensive study that compared the in vitro activities of all three echinocandins against biofilms formed by different common and infrequently identified Candida isolates. We determined the activities of anidulafungin (ANID), caspofungin (CAS), and micafungin (MFG) against planktonic cells and biofilms of bloodstream isolates of C. albicans (15 strains), Candida parapsilosis (6 strains), Candida lusitaniae (16 strains), Candida guilliermondii (5 strains), and Candida krusei (12 strains) by XTT [2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] assay. Planktonic and biofilm MICs were defined as ≥50% fungal damage. Planktonic cells of all Candida species were susceptible to the three echinocandins, with MICs of ≤1 mg/liter. By comparison, differences in the MIC profiles of biofilms in response to echinocandins existed among the Candida species. Thus, C. lusitaniae and C. guilliermondii biofilms were highly recalcitrant to all echinocandins, with MICs of ≥32 mg/liter. In contrast, the MICs of all three echinocandins for C. albicans and C. krusei biofilms were relatively low (MICs ≤ 1 mg/liter). While echinocandins exhibited generally high MICs against C. parapsilosis biofilms, MFG exhibited the lowest MICs against these isolates (4 mg/liter). A paradoxical growth effect was observed with CAS concentrations ranging from 8 to 64 mg/liter against C. albicans and C. parapsilosis biofilms but not against C. krusei, C. lusitaniae, or C. guilliermondii. While non-albicans Candida planktonic cells were susceptible to all echinocandins, there were drug- and species-specific differences in susceptibility among biofilms of the various Candida species, with C. lusitaniae and C. guilliermondii exhibiting profiles of high MICs of the three echinocandins.     

Candida albicans and Staphylococcus aureus Form Polymicrobial Biofilms: Effects on Antimicrobial Resistance

Candida albicans readily forms biofilms on the surface on indwelling medical devices, and these biofilms serve as a source of local and systemic infections. It is estimated that 27% of nosocomial C. albicans bloodstream infections are polymicrobial, with Staphylococcus aureus as the third most common organism isolated in conjunction with C. albicans. We tested whether S. aureus and C. albicans are able to form a polymicrobial biofilm. Although S. aureus formed poor monoculture biofilms in serum, it formed a substantial polymicrobial biofilm in the presence of C. albicans. In terms of architecture, S. aureus formed microcolonies on the surface of the biofilm, with C. albicans serving as the underlying scaffolding. In addition, S. aureus matrix staining revealed a different phenotype in polymicrobial versus monomicrobial biofilms, suggesting that S. aureus may become coated in the matrix secreted by C. albicans. S. aureus resistance to vancomycin was enhanced within the polymicrobial biofilm, required viable C. albicans, and was in part mediated by C. albicans matrix. However, the growth or sensitivity to amphotericin B of C. albicans is not altered in the polymicrobial biofilm.There is increasing evidence in the literature for the importance of polymicrobial infections in which microorganisms interact in a synergistic or inhibitory fashion, impacting pathogenesis and the health of the patient. It was originally estimated that over half of infections originated from biofilms (12). However, the NIH currently estimates that biofilms account for over 80% of all infections in the body (NIH SBIR/STTR Study and Control of Microbial Biofilms program announcement, release date 21 April 1999, http://grants.nih.gov/grants/guide/pa-files/PA-99-084.html). Biofilms are communities of microbes embedded in a polysaccharide matrix adhered to a biotic or abiotic surface. The biofilm-associated microorganisms are refractory to both antimicrobial agents and the host immune response. Polymicrobial biofilms represent an understudied and clinically relevant health problem, with the potential to serve as an infectious reservoir for a variety of microorganisms, including bacteria and fungi.Biofilms can form on indwelling medical devices and serve as a source of nosocomial bloodstream infections, which prolong hospitalization and are the 10th leading cause of death in the United States (30). Candida albicans is the fourth leading cause of bloodstream infections and the third most commonly isolated organism from intravascular catheters and is associated with the highest incidence of mortality (13, 30). C. albicans readily forms biofilms on a wide variety of polymers used to make indwelling medical devices, such as dental materials, stents, shunts, prostheses (voice, heart valve, knee, etc.), implants (lens, breast, denture, penile, etc.), endotracheal tubes, pacemakers, and catheters (reviewed in reference 23). There is some evidence to suggest that a large proportion of device-related Candida albicans infections involve biofilms (14, 15, 23). In a prospective study of catheter colonization, C. albicans ranked second in the ratio of colonization to invasive disease (13). C. albicans biofilms have a unique gene expression pattern (18, 24, 31) and are more resistant to antifungal treatment than planktonic cells (23, 26). A unique feature of C. albicans biofilms is the morphological heterogeneity of the biofilm cells, which results in a complex three-dimensional biofilm architecture (11). C. albicans biofilm formation is initiated upon contact with an appropriate polymeric surface under morphogenesis-inducing growth conditions. Serum is the classical clinically relevant inducer of morphogenesis, although other media can be used in vitro. During early biofilm formation, yeast cells adhere to an appropriate surface and initiate germ tube formation. The intermediate phase is characterized by continued hyphal elongation and extracellular matrix production, which is composed primarily of glucose along with proteins and other sugars (2). Mature biofilms consist of a yeast base, with hyphal elements encased in matrix extending away from the surface forming a sticky net-like structure (11). Newly formed daughter yeast cells grow out of hyphal elements and are released, seeding new niches for biofilm formation or infection.It is estimated that 27% of nosocomial C. albicans bloodstream infections are polymicrobial, with Staphylococcus aureus as the third most common organism isolated in conjunction with C. albicans (22). Interestingly, the combined effect of C. albicans and S. aureus results in synergism and increased mortality in mice (5-9). Although the infectious parameters of polymicrobial infections in humans are not well characterized, eliminating the infection may involve a more complex antimicrobial regimen. It has previously been demonstrated that a mixed species biofilm of C. albicans and Staphylococcus epidermidis enhances the growth of S. epidermidis and increases the resistance of S. epidermidis to vancomycin (1, 16). It is worth mentioning that biofilm formation in S. epidermidis and biofilm formation in S. aureus are not equivalent. Compared with S. epidermidis, S. aureus does not form biofilms as readily on abiotic surfaces, requiring precoating and nutrient supplementation (10). However, S. aureus is a more clinically important pathogen, with higher rates of device-related systemic infection and mortality (reviewed in references 20 and 25). Therefore, we sought to determine whether C. albicans and S. aureus could form polymicrobial biofilms and whether these biofilms exhibited altered antimicrobial sensitivity.     

Synergistic effect of ofloxacin and fluconazole against azole-resistant Candida albicans

We investigated the combination effects of ofloxacin and fluconazole against azole-resistant Candida albicans strains in vitro and in vivo. Ofloxacin alone showed no efficacy against the azole-resistant C. albicans strain, C26. The in-vitro combination effects were evaluated by the checkerboard method, calculated as the fractional inhibitory concentration (FIC) index, but there was no synergistic effect of the combination. The activity of the drug efflux pump in the azole-resistant C. albicans strains was measured by intracellular rhodamine 6G concentration. When the cells were incubated with ofloxacin or grepafloxacin, the intracellular rhodamine 6G concentration was significantly increased in the azole-resistant C. albicans strain. In-vivo combination effects were evaluated in murine disseminated candidiasis. The survival of the mice was not prolonged, but counts of the yeast cells in the kidney and spleen were reduced following treatment with the combination of ofloxacin (20 mg/kg) and fluconazole (20 mg/kg). The combination of ofloxacin and fluconazole may represent an effective strategy to treat infections caused by azole-resistant C. albicans. Received: March 10, 2000 / Accepted: May 17, 2000     

Quercetin Sensitizes Fluconazole-Resistant Candida albicans To Induce Apoptotic Cell Death by Modulating Quorum Sensing

Quorum sensing (QS) regulates group behaviors of Candida albicans such as biofilm, hyphal growth, and virulence factors. The sesquiterpene alcohol farnesol, a QS molecule produced by C. albicans, is known to regulate the expression of virulence weapons of this fungus. Fluconazole (FCZ) is a broad-spectrum antifungal drug that is used for the treatment of C. albicans infections. While FCZ can be cytotoxic at high concentrations, our results show that at much lower concentrations, quercetin (QC), a dietary flavonoid isolated from an edible lichen (Usnea longissima), can be implemented as a sensitizing agent for FCZ-resistant C. albicans NBC099, enhancing the efficacy of FCZ. QC enhanced FCZ-mediated cell killing of NBC099 and also induced cell death. These experiments indicated that the combined application of both drugs was FCZ dose dependent rather than QC dose dependent. In addition, we found that QC strongly suppressed the production of virulence weapons—biofilm formation, hyphal development, phospholipase, proteinase, esterase, and hemolytic activity. Treatment with QC also increased FCZ-mediated cell death in NBC099 biofilms. Interestingly, we also found that QC enhances the anticandidal activity of FCZ by inducing apoptotic cell death. We have also established that this sensitization is reliant on the farnesol response generated by QC. Molecular docking studies also support this conclusion and suggest that QC can form hydrogen bonds with Gln969, Thr1105, Ser1108, Arg1109, Asn1110, and Gly1061 in the ATP binding pocket of adenylate cyclase. Thus, this QS-mediated combined sensitizer (QC)-anticandidal agent (FCZ) strategy may be a novel way to enhance the efficacy of FCZ-based therapy of C. albicans infections.     

Activity of Gallidermin on Staphylococcus aureus and Staphylococcus epidermidis Biofilms

Due to their abilities to form strong biofilms, Staphylococcus aureus and Staphylococcus epidermidis are the most frequently isolated pathogens in persistent and chronic implant-associated infections. As biofilm-embedded bacteria are more resistant to antibiotics and the immune system, they are extremely difficult to treat. Therefore, biofilm-active antibiotics are a major challenge. Here we investigated the effect of the lantibiotic gallidermin on two representative biofilm-forming staphylococcal species. Gallidermin inhibits not only the growth of staphylococci in a dose-dependent manner but also efficiently prevents biofilm formation by both species. The effect on biofilm might be due to repression of biofilm-related targets, such as ica (intercellular adhesin) and atl (major autolysin). However, gallidermin''s killing activity on 24-h and 5-day-old biofilms was significantly decreased. A subpopulation of 0.1 to 1.0% of cells survived, comprising “persister” cells of an unknown genetic and physiological state. Like many other antibiotics, gallidermin showed only limited activity on cells within mature biofilms.