The microbial composition of smear-ripened cheeses is not very clear. A total of 194 bacterial isolates and 187 yeast isolates from the surfaces of four Irish farmhouse smear-ripened cheeses were identified at the midpoint of ripening using pulsed-field gel electrophoresis (PFGE), repetitive sequence-based PCR, and 16S rRNA gene sequencing for identifying and typing the bacteria and Fourier transform infrared spectroscopy and mitochondrial DNA restriction fragment length polymorphism (mtDNA RFLP) analysis for identifying and typing the yeast. The yeast microflora was very uniform, and Debaryomyces hansenii was the dominant species in the four cheeses. Yarrowia lipolytica was also isolated in low numbers from one cheese. The bacteria were highly diverse, and 14 different species, Corynebacterium casei, Corynebacterium variabile, Arthrobacter arilaitensis, Arthrobacter sp., Microbacterium gubbeenense, Agrococcus sp. nov., Brevibacterium linens, Staphylococcus epidermidis, Staphylococcus equorum, Staphylococcus saprophyticus, Micrococcus luteus, Halomonas venusta, Vibrio sp., and Bacillus sp., were identified on the four cheeses. Each cheese had a more or less unique microflora with four to nine species on its surface. However, two bacteria, C. casei and A. arilaitensis, were found on each cheese. Diversity at the strain level was also observed, based on the different PFGE patterns and mtDNA RFLP profiles of the dominant bacterial and yeast species. None of the ripening cultures deliberately inoculated onto the surface were reisolated from the cheeses. This study confirms the importance of the adventitious, resident microflora in the ripening of smear cheeses.Surface-ripened cheeses can be divided into mold-ripened cheeses, such as Camembert and Brie, and bacterium-ripened cheeses, such as Reblochon, Tilsit, and brick. The latter cheeses are also called smear or red smear cheeses because of the development of viscous, red-orange smears on their surfaces during ripening. The smear is a microbial mat composed of bacteria and yeast, and these microorganisms are mainly responsible for the development of the flavor characteristics of the cheeses (5, 27). The ripening process starts with the development of yeast cells, which metabolize lactate to CO 2 and H 2 O and form alkaline metabolites, such as ammonia (5,30), that lead to deacidification of the cheese surface, enabling the growth of salt-tolerant but less acid-tolerant gram-positive catalase-positive bacteria, such as Micrococcaceae and coryneform bacteria.The microbiology of these cheeses is poorly understood. In the past, Brevibacterium linens was considered to be the major organism found on the cheese surface. However, more recent investigations show that other bacteria are also important. found that Arthrobacter nicotianae, B. linens, Corynebacterium ammoniagenes, Corynebacterium variabile, and Rhodococcus fascians were the dominant organisms in 21 brick cheeses from six German dairies, while Eliskases-Lechner and Ginzinger (7) found that although B. linens ac...

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Enterococci are widely distributed in raw-milk cheeses and are generally thought to positively affect flavor development. Their natural habitats are the human and animal intestinal tracts, but they are also found in soil, on plants, and in the intestines of insects and birds. The source of enterococci in raw-milk cheese is unknown. In the present study, an epidemiological approach with pulsed-field gel electrophoresis (PFGE) was used to type 646 Enterococcus strains which were isolated from a Cheddar-type cheese, the milk it was made from, the feces of cows and humans associated with the cheese-making unit, and the environment, including the milking equipment, the water used on the farm, and the cows' teats. Nine different PFGE patterns, three of Enterococcus casseliflavus, five of Enterococcus faecalis, and one of Enterococcus durans, were found. The same three clones, one of E. faecalis and two of E. casseliflavus, dominated almost all of the milk, cheese, and human fecal samples. The two E. casseliflavus clones were also found in the bulk tank and the milking machine even after chlorination, suggesting that a niche where enterococci could grow was present and that contamination with enterococci begins with the milking equipment. It is likely but unproven that the enterococci present in the human feces are due to consumption of the cheese. Cow feces were not considered the source of enterococci in the cheese, as Enterococcus faecium and Streptococcus bovis, which largely dominated the cows' intestinal tracts, were not found in either the milk or the cheese.

Aims:  To determine the relationships between the major organisms from the cheese‐making personnel and environment and the surface of a smear cheese. Methods and Results:  360 yeast and 593 bacteria from the cheese surface, the dairy environment and the hands and arms of personnel were collected. Pulsed‐field gel electrophoresis, repetitive sequence‐based polymerase chain reaction and 16S rDNA sequencing were used for typing and identifying the bacteria, and mitochondrial DNA restriction fragment length polymorphism and Fourier‐transform infrared spectroscopy for typing and identifying the yeast. The three most dominant bacteria were Corynebacterium casei, Corynebacterium variabile and Staphylococcus saprophyticus, which were divided into three, five and seven clusters, respectively, by macrorestriction analysis. The same clones from these organisms were isolated on the cheese surface, the dairy environment and the skin of the cheese personnel. Debaryomyces hansenii was the most dominant yeast. Conclusions:  A ‘house’ microflora exists in the cheese plant. Although the original source of the micro‐organisms was not identified, the brines were an important source of S. saprophyticus and D. hansenii and, additionally, the arms and hands of the workers the sources of C. casei and C. variabile. Significance and Impact of the Study:  This is the first time that the major contribution of the house microflora to the ripening of a smear‐ripened cheese has been demonstrated.