Candida albicans biofilm can retain and release Human Herpes simplex virus type 1 in vitro

Microorganisms universally attach to surfaces and produce extracellular polymeric saccharides (EPS), resulting in the formation of a biofilm. Biofilms can pose a serious problem for public health because of the increased resistance of biofilm-associated organisms to antimicrobial agents and the potential for these organisms to cause infections in patients with indwelling medical devices. Moreover, involvement of enteric viruses with a variety of biofilms has been reported, although very little is known about this phenomenon. The presence of some pathogenic viruses in water biofilms underlines the ability of viruses to attach and cling to biofilms retaining their infectivity. No information is available so far on interactions between pathogenic viruses and Candida albicans biofilm. This biofilm is responsible for severe device-related disseminated infections causing invasive candidemias with a very high rate of mortality. The aim of this in vitro study was to ascertain whether Herpes Simplex Virus type 1 (HSV-1) can be encompassed in Candida biofilm produced in cell culture plates and/or on silicone and PVC catheters. HSV-1 was added to mature biofilms and the amount of infectious virus embedded in biofilm matrix detached by washing and energetic scratching was titrated on VERO cells 24-48 h later. Experiments with planktonic Candida were carried out in parallel, as well as in the absence of Candida. According to our results, free virus particles of HSV-1, as well as HSV-1 infected cells, remain embedded in Candida biofilm on tissue cell culture plates as well as on both types of catheter with a significantly higher load than in the presence of planktonic Candida or in the negative controls. These results provide the first evidence that infectious viruses, after being entrapped in Candida biofilms, can retain their infectivity and be released posing a health risk for patients with implanted medical devices. Interactions between HSV-1 embedded in Candida biofilm and disinfectants as well as neutralizing antibodies and drugs are discussed.