Occurrence of yeasts, pseudomonads and enteric bacteria in the oral cavity of patients undergoing head and neck radiotherapy

Abstract

The aim of this study was to evaluate the occurrence of yeasts, pseudomonads and enteric bacteria in the oral cavity of patients undergoing radiotherapy (RT) for treatment of head and neck cancer. Fifty patients receiving RT were examined before, during and 30 days after RT. Saliva, mucosa, and biofilm samples were collected and microorganisms were detected by culture and polymerase chain reaction (PCR). The most prevalent yeasts in patients submitted to RT were Candida albicans, C. tropicalis, C. krusei, C. glabrata and C. parapsilosis. Citrobacter, Enterobacter, Enterococcus, Klebsiella, Proteus, and Pseudomonas were the most frequently cultivated bacteria. Before RT, targeted bacteria were cultivated from 22.2% of edentulous patients and 16.6% of dentate patients; 30 days after RT, these microorganisms were recovered from 77.8% edentulous and 46.8% dentate patients. By PCR, these microorganisms were detected from all edentulous patients, 78.1% of dentate patients. The presence of Gram-negative enteric roads and fungi was particularly frequent in patients presenting mucositis level III or IV. Modifications in the oral environment due to RT treatment seem to facilitate the colonization of oral cavity by members of family Enterobacteriaceae, genera Enterococcus and Candida.

Oral microbiota and mucositis in patients with head and neck cancer undergoing radiotherapy: literature review

“…Patients presenting the highest populations of these yeasts prior to RT are also the first to develop clinically detectable infection 7,20 , which reinforces the need for antifungal preventive approach for oral candidiasis in irradiated patients 20,21 . On the other hand, as opportunistic pathogens, the high prevalence and populations of fungi also reflect the poor conditions of oral hygiene and deterioration along the RT 34 , as well nutritional deficiencies and loss of weight in irradiated patients.…”

“…Mucositis is associated with ulcerated areas, hinder nutrition and might facilitate the deployment of local or systemic infections 5 , usually caused by opportunistic microorganisms, such as enteric pathogens, anaerobic Gramnegative rods and yeasts 7,19,20,41,42 sometimes already present in higher proportions in cancer patients before RT 23 . The presence, severity and persistence of xerostomia seem to be the main factors associated with the presence of candidiasis in irradiated patients, facilitating the colonization of surfaces that previously did not harbor these fungi, allowing the growth of yeast populations 43,44 .…”

“…However, literature has failed to discover any advantage for non-albicans Candida during or after RT 23,34,44,46,47 . The prevention/control of oral candidiasis, by improving oral hygiene standards, use of antifungal solutions and nutritional support, could also be a measure with impact on mucositis intensity in irradiated patients 7,34 , particularly the systemic use of fluconazole and aqueous solution of nystatin 20,21,34,47 .…”

“…The development of xerostomia and mucositis is followed by several changes in oral microbiota, but the significance of such phenomenon remains unclear 19 . Some evidences suggest that oral environment might act as reservoirs of classical and opportunistic pathogens, facilitating the establishment of opportunistic infections, particularly in patients receiving chemotherapy and undergoing RT simultaneously 19,20 . In addition, it is evident the deterioration of dental health due to mucositis and radiation caries associated with the aggravation of xerostomia, amplifying the numbers of cariogenic cocci, reducing the pH of biofilm and cooperate, exacerbating the adhesion and proliferation of Candida on oral mucosa.…”

“…The presence of exogenous Gram-negative bacteria in the biofilm could affect the inflammatory conditions of the mucosa, allowing new pressures to the development of radiation induced mucositis 20,21 . Thus, the aim of this study was discuss the role played by microorganisms in the development and evolution of mucositis in patients with head and neck cancer undergoing RT.…”