The fungal species Candida albicans and the bacterial species Staphylococcus aureus are responsible for a majority of hospital-acquired infections and often coinfect critically ill patients as complicating polymicrobial biofilms. To investigate biofilm structure during polymicrobial growth, dual-species biofilms were imaged with confocal scanning laser microscopy. Analyses revealed a unique biofilm architecture where S. aureus commonly associated with the hyphal elements of C. albicans. This physical interaction may provide staphylococci with an invasion strategy because candidal hyphae can penetrate through epithelial layers. To further understand the molecular mechanisms possibly responsible for previously demonstrated amplified virulence during coinfection, protein expression studies were undertaken. Differential in-gel electrophoresis identified a total of 27 proteins to be significantly differentially produced by these organisms during coculture biofilm growth. Among the upregulated staphylococcal proteins was l-lactate dehydrogenase 1, which confers resistance to host-derived oxidative stressors. Among the downregulated proteins was the global transcriptional repressor of virulence factors, CodY. These findings demonstrate that the hyphae-mediated enhanced pathogenesis of S. aureus may not only be due to physical interactions but can also be attributed to the differential regulation of specific virulence factors induced during polymicrobial growth. Further characterization of the intricate interaction between these pathogens at the molecular level is warranted, as it may aid in the design of novel therapeutic strategies aimed at combating fungal–bacterial polymicrobial infection.

Farnesol, a precursor in the isoprenoid/sterol pathway, was recently identified as a quorum-sensing molecule produced by the fungal pathogen Candida albicans. Farnesol is involved in the inhibition of germination and biofilm formation by C. albicans and can be cytotoxic at certain concentrations. In addition, we have shown that farnesol can trigger apoptosis in mammalian cells via the classical apoptotic pathways. In order to elucidate the mechanism behind farnesol cytotoxicity in C. albicans, the response to farnesol was investigated, using proteomic analysis. Global protein expression profiles demonstrated significant changes in protein expression resulting from farnesol exposure. Among the downregulated proteins were those involved in metabolism, glycolysis, protein synthesis, and mitochondrial electron transport and the respiratory chain, whereas proteins involved in folding, protection against environmental and oxidative stress, actin cytoskeleton reorganization, and apoptosis were upregulated. Cellular changes that accompany apoptosis (regulated cell death) were further analyzed using fluorescent microscopy and gene expression analysis. The results indicated reactive oxygen species accumulation, mitochondrial degradation, and positive terminal deoxynucleotidyltransferasemediated dUTP-biotin nick end labeling (TUNEL) in the farnesol-exposed cells concurrent with increased expression of antioxidant-encoding and drug response genes. More importantly, the results demonstrated farnesol-induced upregulation of the caspase gene MCA1 and the intracellular presence of activated caspases.In conclusion, this study demonstrated that farnesol promotes apoptosis in C. albicans through caspase activation, implying an important physiological role for farnesol in the fungal cell life cycle with important implications for adaptation and survival.

The aim of this retrospective study was to describe the oral health status of patients before, during, and after radiotherapy (RT) for the treatment of head and neck cancer (HNC). Before RT, the following data was collected: presence of unrecoverable teeth, residual roots, unerupted teeth, use of dentures, periodontal alterations, caries, candidiasis, and xerostomia. Mucositis, candidiasis, and xerostomia were evaluated during RT. Patients continued to be followed after RT for evaluation of mucositis, candidiasis, xerostomia, radiation caries, and osteoradionecrosis. For statistical analysis, 95% confidence intervals (CI) were determined using sample size, population, and percentages. Before RT, 120 (57.9%) patients presented with alterations in the oral cavity namely, 85 (41.0%) with periodontal disease, 44 (21.2%) with residual roots, 25 (12.0%) with caries, 15 (7.2%) with candidiasis, and 12 (5.8%) had an unerupted tooth present. Xerostomia was a complaint of 19 patients (9.1%). Restorations were indicated for 33 patients (15.9%), whereas extraction was indicated for 104 (50.2%) patients. During RT, mucositis was found in 80 (61.7%) patients, candidiasis in 60 (45.8%), and xerostomia was a complaint of 82 patients (62.6%). After RT, mucositis persisted in 21 patients (19.2%), candidiasis was identified in 23 patients (21.1%), and xerostomia was reported by 58 patients (53.2%). Radiation caries developed in 12 patients (11.0%), whereas six patients (5.5%) developed osteoradionecrosis. The demographic profile herein presented will be useful as baseline data to provide additional epidemiological information and to determine future measures for prevention and treatment of RT-induced complications and sequelae.

Summary Osteonecrosis of the jaw secondary to bisphosphonate infusion (zoledronic acid‐ZA) is assumed to be a bone disease. This study investigated the effects of ZA on soft tissues using oral mucosal cells as an in vitro model of soft tissue cell death in the pathogenesis of bone necrosis. Human gingival fibroblast and keratinocyte cell lines were exposed to different concentrations of ZA (0·25–3 μmol/l), using 1 μmol/l as the expected baseline concentration. A dose–response effect on apoptosis and cell proliferation [Terminal deoxynucleotidyl transferase‐mediated dUTP‐Biotin End Labelling and Annexin V or Coulter counter and 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium), respectively] was observed with increasing ZA concentrations; both reversed using siRNA against caspase 3 or 9. Gene expression analysis using RT2 Profiler polymerase chain reaction Arrays demonstrated the differential expression of multiple genes involved in apoptosis including those that encode TNF, BCL‐2, Caspase, IAP, TRAF and Death Domain families. Western blot analysis confirmed the presence of activated forms of caspase 3 and 9 and underexpression of survivin protein expression. This study demonstrated that low concentrations of ZA rapidly and directly affected the oral mucosal tissues though the induction of a gene‐regulated apoptotic process. These findings support the potential for soft tissue injury as an initiating/potentiating event for osteonecrosis.

Oropharyngeal candidiasis is an opportunistic infection considered to be a harbinger of AIDS. The etiologic agent Candida albicans is a fungal species commonly colonizing human mucosal surfaces. However, under conditions of immune dysfunction, colonizing C. albicans can become an opportunistic pathogen causing superficial or even life-threatening infections. The reasons behind this transition, however, are not clear. In the oral cavity, salivary antimicrobial peptides are considered to be an important part of the host innate defense system in the prevention of microbial colonization. Histatin-5 specifically has exhibited potent activity against C. albicans. Our previous studies have shown histatin-5 levels to be significantly reduced in the saliva of HIV+ individuals, indicating an important role for histatin-5 in keeping C. albicans in its commensal stage. The versatility in the pathogenic potential of C. albicans is the result of its ability to adapt through the regulation of virulence determinants, most notably of which are proteolytic enzymes (Saps), involved in tissue degradation. In this study, we show that C. albicans cells efficiently and rapidly degrade histatin-5, resulting in loss of its anti-candidal potency. In addition, we demonstrate that this cellular activity is due to proteolysis by a member of the secreted aspartic proteases (Sap) family involved in C. albicans pathogenesis. Specifically, the proteolysis was attributed to Sap9, in turn identifying histatin-5 as the first host-specific substrate for that isoenzyme. These findings demonstrate for the first time the ability of a specific C. albicans enzyme to degrade and deactivate a host antimicrobial peptide involved in the protection of the oral mucosa against C. albicans, thereby providing new insights into the factors directing the transition of C. albicans from commensal to pathogen, with important clinical implications for alternative therapy. This report characterizes the first defined mechanism behind the enhanced susceptibility of HIV+ individuals to oral candidiasis since the emergence of HIV.