The incidence of Weeksella- and Bergeyella-like bacteria in the food environment.

Eighty-five catalase- and oxidase-positive Gram-negative rods and cocci susceptible to penicillin G were isolated from a variety of food sources. The phenotypic relationships of these isolates with reference cultures of Bergeyella-like, Chryseobacterium, Empedobacter, Myroides, Moraxella, Sphingobacterium and Weeksella-like strains were examined by numerical taxonomy. Seventy-three isolates were recovered in five groups; 80% of the isolates clustered in groups 1, 2 and 3 and produced indole, bearing a strong resemblance to Weeksella and Bergeyella. They could not, however, be regarded as belonging to the known species of W. virosa and B. zoohelcum. It is suggested that three species may be necessary to accommodate the environmental Weeksella- or Bergeyella-like bacteria. The isolates in groups 4 and 5 had white colonies and were unable to produce indole, in this way resembling the Moraxella genus.

The taxonomic relationship of certain environmental flavobacteria to the genus Weeksella.

Forty environmental strains and reference cultures of Flavobacterium, Cytophaga and Weeksella spp. were examined by numerical taxonomy. Twenty-seven strains were recovered in four phena. Phena 1A and 1B comprised 48% of the strains and were sufficiently similar to the genus Weeksella as to suggest possible inclusion in this genus. They could not be accommodated in the existing species W. virosa and W. zoohelcum. Strains from phenon 2 appear to belong neither in the Flavobacterium or the Weeksella genus. Although no reference strains were included in phena 3 and 4 they appear phenotypically to be most similar to F. breve and F. odoratum respectively.

Determination of Bacterial ATP in Milk - The Influence of Adenosine Triphosphate-Hydrolyzing Enzymes from Somatic Cells and Pseudomonas fluorescens.

Presence and origin of adenosine triphosphate (ATP) hydrolyzing enzymes in milk and their effect on the ATP assay were determined. Somatic cells, when present in large numbers, produced sufficient enzyme to hydrolyze extracted ATP. This was illustrated by the relationship which existed between ATPase activity and somatic cell counts (polynominal correlation coefficient (R) = 0,82; n = 39). A highly significant relationship [linear correlation coefficient (r) = 0,91; number of observations (n) = 81] was found between the count of a Pseudomonas fluorescens strain and the resultant ATPase activity. This activity, however, did not appear to influence the ATP assay, the enzymes being produced in the late exponential phase and early stationary phase of growth. At this stage the psychrotrophic counts has reached a level of 1 × 108 CFU/ml which could result in off flavors in the milk. Researchers encountering high somatic cell counts in milk are advised to interpret the results of the ATP assay with care.