Assessment of multi-contaminant exposure in a cancer treatment center: a 2-year monitoring of molds, mycotoxins, endotoxins, and glucans in bioaerosols.

Indoor air quality in health care facilities is a major public health concern, particularly for immunocompromised patients who may be exposed to microbiological contaminants such as molds, mycotoxins, endotoxins, and (1,3)-ß-D-glucans. Over 2 years, bioaerosols were collected on a monthly basis in a cancer treatment center (Centre F. Baclesse, Normandy, France), characterized from areas where there was no any particular air treatment. Results showed the complexity of mycoflora in bioaerosols with more than 100 fungal species identified. A list of major strains in hospital environments could be put forward due to the frequency, the concentration level, and/or the capacity to produce mycotoxins in vitro: Aspergillus fumigatus, Aspergillus melleus, Aspergillus niger, Aspergillus versicolor, Cladosporium herbarum, Purpureocillium lilacinum, and Penicillium brevicompactum. The mean levels of viable airborne fungal particles were less than 30.530 CFU per m3 of air and were correlated to the total number of 0.30 to 20 µm particles. Seasonal variations were observed with fungal particle peaks during the summer and autumn. Statistical analysis showed that airborne fungal particle levels depended on the relative humidity level which could be a useful indicator of fungal contamination. Finally, the exposure to airborne mycotoxins was very low (only 3 positive samples), and no mutagenic activity was found in bioaerosols. Nevertheless, some fungal strains such as Aspergillus versicolor or Penicillium brevicompactum showed toxigenic potential in vitro.

Safety assessment of dairy microorganisms: Geotrichum candidum.

Geotrichum candidum is a ubiquitous filamentous yeast-like fungus commonly isolated from soil, air, water, milk, silage, plant tissues, digestive tract in humans and other mammals. This species is widely used as adjunct culture in the maturation of cheese. The genus Geotrichum is composed of 18 species. A recent taxonomic revision concluded that the old Galactomyces geotrichum/G. candidum complex contained four separate species of which Galactomyces candidus sp. nov./G. candidum. M13 primer can be used for identifying species of the Geotrichum genus. Used in combination, RAPD-PCR and RAM-PCR permit strains to be differentiated. The species can be unambiguous differentiated from the two species most frequently described in human pathology: Geotrichum clavatum (reclassified Saprochaete clavata) and Geotrichum capitatum (reclassified Magnusiomyces capitatus/Saprochaete capitata). Sources of exposure are food ingestion--cheese consumption playing a major role--inhalation and contact. A bibliographic survey was conducted to assess corresponding hazards and risks. G. candidum infections (mainly pulmonary or bronchopulmonary, but also cutaneous, oral, disseminates) are very rare: fewer than 100 cases reported between 1842 and 2006. Moreover, cases were not all confirmed by repeated isolations and demonstration of the fungus' presence in tissues, a prerequisite to establish a true diagnosis of geotrichosis. Immunocompromised population was recently shown as a target for opportunistic infection. The most effective treatments include either azole drogs as ketonazole, iconazole and clotrimazole, or polyene antibiotics as amphotericin B, nystatin and pimaricin, or voriconazole-amphotericin B association. Less than 1 case/year of disease was possibly caused by G. candidum and it never included dairy products or foodborne infection. The risk of developing an infection due to G. candidum in connection with its technological use and consumption of dairy products is virtually nil. For these reasons, G. candidum should be proposed for QPS status.

Development of primers for detecting dominant yeasts in smear-ripened cheeses.

PCR primers were developed for the specific detection of Clavispora lusitaniae, Debaryomyces hansenii var hansenii, Geotrichum candidum, Kluyveromyces lactis and K. marxianus and Yarrowia lipolytica, yeast species commonly found on the surface of smear cheese. Forty eight representative strains frequently found in smear cheeses or taxonomically related to the target yeasts were used as templates, to validate the designed primers. The specific and selective detection of these yeasts was effective in situ, in Livarot smear, without yeast isolation and culture and was comparable with data obtained with a conventional method. The primers described here have thus potential for PCR studies applied to cheese. It should also be possible to use some of these primers with other substrates.

Levels of cystathionine gamma lyase production by Geotrichum candidum in synthetic media and correlation with the presence of sulphur flavours in cheese.

Geotrichum candidum is a cheese-ripening agent with the potential to produce sulphur flavour compounds in soft cheeses. We aimed to develop an alternative test for predicting the aromatic (sulphur flavours) potential of G. candidum strains in soft cheese. Twelve strains of G. candidum with different levels of demethiolase activity (determined by a chemical method) in YEL-met (yeast extract, lactate methionine) medium were studied. We investigated cgl (cystathionine gamma lyase) gene expression after culture in three media - YEL-met, casamino acid and curd media - and then carried out sensory analysis on a Camembert cheese matrix. We found no correlation between demethiolase activity in vitro and cgl gene expression. Sensory analysis (detection of sulphur flavours) identified different aromatic profiles linked to cgl expression, but not to demethiolase activity. The RT-PCR technique described here is potentially useful for predicting the tendency of a given strain of G. candidum to develop sulphur flavours in cheese matrix. This is the first demonstration that an in vitro molecular approach could be used as a predictive test for evaluating the potential of G. candidum strains to generate sulphur compounds in situ (Camembert cheese matrix).

Intra-species chromosome-length polymorphism in Geotrichum candidum revealed by pulsed field gel electrophoresis.

Geotrichum candidum is an ascomycetous anamorph yeast-like fungus found in various habitats. It is a component of the natural flora of milk and is used as a maturing agent for both soft and hard cheeses. This microorganism displays phenotypic variability and may act as an opportunist pathogen, causing geotrichosis. Cytological analysis of G. candidum strain ATCC 204307 showed this strain to have eight chromosomes. We prepared chromosomal DNA from 13 strains of G. candidum differing in habitat and morphotype. We used pulsed field gel electrophoresis (PFGE) in two sets of conditions to determine the size of the chromosomal DNA molecules. The strains investigated had five to eight chromosomes, 0.6 to 4.5 Mb in size. We estimated genome size in these 13 strains to be between 11 and 19 Mb. Pulsed-field gel electrophoresis profiles showed a high degree of polymorphism, indicating considerable variability between strains. Genome size and the presence of large chromosomes appeared to be correlated with morphotype. Strains with a mold-like or intermediate morphotype tended to have larger genomes than strains with a yeast-like morphotype did.