Diversity and assessment of potential risk factors of Gram-negative isolates associated with French cheeses

Abstract

The goal of this study was to identify at the species level a large collection of Gram-negative dairy bacteria isolated from milks or semi-hard and soft, smear-ripened cheeses (cheese core or surface samples) from different regions of France. The isolates were then assessed for two risk factors, antibiotic resistance and volatile and non-volatile biogenic amine production in vitro. In total, 173 Gram-negative isolates were identified by rrs and/or rpoB gene sequencing. A large biodiversity was observed with nearly half of all Gram-negative isolates belonging to the Enterobacteriaceae family. Overall, 26 different genera represented by 68 species including potential new species were identified among the studied Gram-negative isolates for both surface and milk or cheese core samples. The most frequently isolated genera corresponded to Pseudomonas, Proteus, Psychrobacter, Halomonas and Serratia and represented almost 54% of the dairy collection. After Pseudomonas, Chryseobacterium, Enterobacter and Stenotrophomonas were the most frequently isolated genera found in cheese core and milk samples while Proteus, Psychrobacter, Halomonas and Serratia were the most frequently isolated genera among surface samples. Antibiotic resistance profiles indicated that resistances to the aminosid, imipemen and quinolon were relatively low while more than half of all tested isolates were resistant to antibiotics belonging to the monobactam, cephem, fosfomycin, colistin, phenicol, sulfamid and some from the penam families. Thirty-six% of isolates were negative for in vitro biogenic amine production. Among biogenic amine-producers, cadaverine was the most frequently produced followed by isoamylamine, histamine and putrescine. Only low levels (<75 mg/l) of tyramine were detected in vitro.

Facility-Specific “House” Microbiome Drives Microbial Landscapes of Artisan Cheesemaking Plants

“…Using a culture-based approach, Mounier et al (14) detected a similar "house" microbiota in a washed-rind cheesemaking plant, dominated by Debaryomyces hansenii, Corynebacterium spp., and Staphylococcus saprophyticus, suggesting that this same functional community may generalize across facilities producing similar styles of cheese. Several of the halotolerant Gammaproteobacteria detected on aging surfaces and cheeses in this study have been isolated previously from European washed-rind cheeses, including Pseudoalteromonas (50), Halomonas (50)(51)(52)(53), and Vibrio (49,52), so likewise appear to be part of the style-specific microbiome enriched by washed-rind processing techniques and likely play a role in the maturation phenomena of these cheeses. The coryneform Actinobacteria detected on aging-room and cheese surfaces, particularly in facility A, have likewise been isolated from washed-rind cheeses previously, including Brevibacterium (50)(51)(52)54), Corynebacterium (50)(51)(52)54), and Brachybacterium (50,54,55).…”

Cow Teat Skin, a Potential Source of Diverse Microbial Populations for Cheese Production

“…FD differed from the other farms by its hygiene practices, which were not as stringent as in the other farms and could promote these species. The following species, less frequently detected on the surface of cow teats, were (13). Gram-negative bacteria may have a positive or negative effect on the flavor of cheeses, depending on their ratio in the microbial community (41,42).…”

Characterization of the bacterial biodiversity in Pico cheese (an artisanal Azorean food)

“…Spoilage-related, psychrotrophic γ-proteobacterial sequences (Pseudomonas, Stenotrophomonas and Aeromonas) have been found in other artisanal cheeses (Masoud et al, 2011). Marinomonas,a halotolerant γ-proteobacterium, was present in artisanal cheeses (Coton et al, 2012), but no clear association between cheese spoilage and its presence was found in the literature. Halotolerant bacteria may be transferred to the cheeses by the salt (Ishikawa et al, 2007).…”