Aims:  To study the interactions between Candida albicans and 12 other species of Candida and bacteria in biofilms. Methods and Results:  The number of cells within growing biofilms in a polystyrene tube model was measured after adding C. albicans to preformed biofilms of other micro‐organisms and vice versa. It was also measured after simultaneous biofilm formation of C. albicans and other micro‐organisms. The number of cells of C. albicans within the growing biofilms decreased significantly (P < 0·05) when the fungus was added to preformed biofilms of Candida spp. and bacteria except, with C. parapsilosis, Torulopsis glabrata and the glycocalyx producer Pseudomonas aeruginosa. When C. parapsilosis, Staphylococcus epidermidis (nonglycocalyx producer) or Serratia marcescens was added to preformed biofilms of C. albicans, the number of cells of these micro‐organisms increased in the growing biofilms. Conclusions:  Biofilms of C. albicans are capable of holding other micro‐organisms and more likely to be heterogeneous with other bacteria and fungi in the environment and on medical devices. Significance and Impact of the Study:  Recognition of the heterogeneity of biofilm‐associated organisms can influence treatment decisions, particularly in patients who do not respond to initial appropriate therapy.

Candida albicans occupies a microniche on mucosal surfaces where diverse microbial populations interact within a biofilm. Because C. albicans is intimately involved with other microbes in this environment we studied the interactions of C. albicans with other fungi and bacteria that form mixed microbial aggregates. Once aggregation is initiated, aggregates form rapidly and incorporate fungal as well as bacterial cells. The fungus formed mixed microbial aggregates with homotypic cells (i.e., self to self, e.g., C. albicans or Als1p-expressing yeast cells aggregating with cells bearing Als1p); with heterotypic cells (i.e., self to non-self, e.g., C. albicans or Alsp-expressing yeast cells aggregating with other Candida species); and with xenotypic cells (e.g., C. albicans or Alsp-expressing yeast cells forming aggregates with bacteria). When either of the C. albicans adhesins Als1p or Als5p was displayed on the surface of non-adherent Saccharomyces cerevisiae cells, the S. cerevisiae also mediated these mixed microbial interactions. Thus the Als adhesins are potentially important for the co-adhesion of mixed microbial communities in biofilms and on mucus surfaces.

Hepatitis C is one of the most widespread infectious diseases worldwide and hepatitis C virus (HCV)-induced chronic inflammation is highly associated with progredient liver damage. It was shown that HCV infection increases levels of pro-inflammatory cytokines via activation of NOD-like receptor (NLRP3) inflammasomes, yet the underlying mechanism is still under question. We propose modulation of intracellular pH by p7, a 63 residue ion channel produced by the hepatitis C virus as a possible pathomechanism for hepatitis C-associated inflammation. Recombinant constructs corresponding to HCV genotypes 1-4 were expressed in HEK 293 and RAW 264.7 cells and changes of intracellular pH were monitored using pH-sensitive fluorescent probes as well as production of inflammatory cytokines. Presence of p7 induced general loss of vesicular acidity as well as producing a significant increase in the levels of interleukin-1β (IL-1β). Effects showed a genotype-dependent pattern of IL-1β production, in agreement with the pH-response profile of p7 channels corresponding to hepatitis C genotypes. Lowering the pH of the extracellular medium increased activity of p7 channels as well as production of IL-1β for genotypes 1, 3, and 4, but less for genotype 2. Our data are in agreement with the hypothesis that p7 activity can trigger intracellular signaling cascades that are involved in HCV-associated cytopathy.

BackgroundSilver nanoparticles (AgNPs) are potential antimicrobials agents, which can be considered as an alternative to antibiotics for the treatment of infections caused by multi-drug resistant bacteria. The antimicrobial effects of double and triple combinations of AgNPs, visible blue light, and the conventional antibiotics amoxicillin, azithromycin, clarithromycin, linezolid, and vancomycin, against ten clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) were investigated.MethodsThe antimicrobial activity of AgNPs, applied in combination with blue light, against selected isolates of MRSA was investigated at 1/2–1/128 of its minimal inhibitory concentration (MIC) in 24-well plates. The wells were exposed to blue light source at 460 nm and 250 mW for 1 h using a photon emitting diode. Samples were taken at different time intervals, and viable bacterial counts were determined. The double combinations of AgNPs and each of the antibiotics were assessed by the checkerboard method. The killing assay was used to test possible synergistic effects when blue light was further combined to AgNPs and each antibiotic at a time against selected isolates of MRSA.ResultsThe bactericidal activity of AgNPs, at sub-MIC, and blue light was significantly (p < 0.001) enhanced when both agents were applied in combination compared to each agent alone. Similarly, synergistic interactions were observed when AgNPs were combined with amoxicillin, azithromycin, clarithromycin or linezolid in 30–40 % of the double combinations with no observed antagonistic interaction against the tested isolates. Combination of the AgNPs with vancomycin did not result in enhanced killing against all isolates tested. The antimicrobial activity against MRSA isolates was significantly enhanced in triple combinations of AgNPs, blue light and antibiotic, compared to treatments involving one or two agents. The bactericidal activities were highest when azithromycin or clarithromycin was included in the triple therapy compared to the other antibiotics tested.ConclusionsA new strategy can be used to combat serious infections caused by MRSA by combining AgNPs, blue light, and antibiotics. This triple therapy may include antibiotics, which have been proven to be ineffective against MRSA. The suggested approach would be useful to face the fast-growing drug-resistance with the slow development of new antimicrobial agents, and to preserve last resort antibiotics such as vancomycin.