Efficacy of Ethanol against Candida albicans and Staphylococcus aureus Polymicrobial Biofilms

Abstract

dCandida albicans, an opportunistic fungus, and Staphylococcus aureus, a bacterial pathogen, are two clinically relevant biofilmforming 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.

Antifungal Lock Therapy

“…C. albicans enhanced S. aureus vancomycin resistance in a polymicrobial biofilm, whereas S. aureus did not alter C. albicans d-AmB susceptibility (61). In a silicone disk model of C. albicans-S. aureus biofilms, 30% EtOH was sufficient to prevent C. albicans regrowth, whereas 50% EtOH was required to prevent S. aureus regrowth within monomicrobial or polymicrobial biofilms (63). This is an area of current research interest (44, 54), which is needed to define the optimal approach for treatment or prevention of polymicrobial biofilms.…”

Searching for new strategies against polymicrobial biofilm infections: guanylated polymethacrylates kill mixed fungal/bacterial biofilms

“…coagulasenegative staphylococci) 47 and has been studied in vitro against monomicrobial and polymicrobial biofilms formed by C. albicans or S. aureus. 18,48,49 Although ethanol has advantages, there are concerns about side effects when used as an antimicrobial lock solution, such as systemic toxicity, damage to the catheter materials and the related intraluminal obstruction and thrombosis. 43,47 Given this, it is of interest to develop new approaches, such as what we demonstrate here with guanylated polymethacrylates.…”

“…Ethanol has been reported as an effective lock solution against C. albicans/S. aureus polymicrobial biofilms, 18 but its application in antimicrobial lock therapy has been hindered by side effects. 43 To test the potential of guanylated polymethacrylates as catheter lock agents, we assayed regrowth of biofilms after exposure of the pre-formed biofilm to PG3 or PG4 for 18 h. PG3 at 128 mg/L or PG4 at 256 mg/L were effective in salvaging infected biomaterials, effectively eradicating C. albicans/S.…”

Contribution of Host Signaling and Virome to the Mycobiome

“…S. aureus and C. albicans colonize or sequentially colonize individuals with cystic fibrosis, burn wounds, cystitis and diabetic foot ulcers, in addition to biofilmassociated prosthetic infections, e.g. dentures, voice prostheses, implants, endotracheal tubes, feeding tubes, and catheters [38][39][40]. There are also indications that S. aureus enhances onset of fungalmediated allergic sinusitis [41][42][43].…”