Dormancy Induces the Formation of Persisters in the Candida Albicans-staphylococcus Epidermidis Mixed Species Biofilm

Background: Persisters make biofilm infections difficult to cure, the low content of persisters in biofilm and the difficulty of obtaining them are outstanding problems in research, finding a reliable method to obtain a sufficient amount of persisters is the key to research. Methods: In this study, C.albicans strain ATCC10231 and S.epidermidis ATCC35984 were used to culture mixed biofilms on the surface of a titanium metal coupon. Tetracycline, gentamicin, 5-fluorocytosine(5-Fc), caspofungin, rifampicin, fluconazole and carbonyl cyanide m-chlorophenylhydrazone (CCCP) were used to induce the dormancy of biofilms to produce persisters. Ciprofloxacin and amphotericin B were used to kill the non dormant bacteria, and then the persisters were screened. Results:The study showed that dormancy induced by tetracycline and 5-Fc could significantly increase the persister levels of S.epidermidis and C.albicans, respectively. After the induced persisters were re-cultured, there was no significant change in antibiotic sensitivity compared with before induction.Scanning electron microscope(SEM) observations showed that after dormancy induction, the surface morphology of C.albicans in the mixed biofilm showed convex changes, and the volume of S.epidermidis decreased. Confocal laser scanning microscope (CLSM)observation showed that the mixed biofilm with high content of persisters did not dissolve under the killing of antibiotics, and the biofilm with low content of persisters dissolved in large area. Conclusions: Induction of dormancy is a reliable method for the formation of persistent bacteria in C.albicans-S.epidermidis mixed biofilm.