Properties and partial genetic characterization of Nepean phage and other lytic phages of Brucella species.

Nepean (Np), a new brucellaphage, was associated with atypical Brucella abortus strains from Ontario cattle. Carriage of Np was associated with loss of smooth lipopolysaccharide, changes in some protein bands in acrylamide gel electrophoresis profiles, increased susceptibility to colistin, and increased resistance to ultraviolet killing. Nepean (Np) was compared with brucellaphages Tb, Fi, Wb, Iz and R/C. All were morphologically identical, with icosahedral capsids (50-65 nm diameter) and short tails (15-25 nm long), but Np had a more restricted host range, replicating only in smooth strains of B. abortus. All six brucellaphages were generally similar in resistance to chemical and physical agents. Brucellaphage DNA was double stranded and unmethylated; its molecular size was 38 kilobase pairs. The DNAs of Tb, Fi, Wb, Iz and R/C could not be differentiated by restriction endonuclease digest profiles produced by BgII, EcoRI, HindIII or PvuII. Nepean (Np) DNA was very similar to that of the other brucellaphages, but with every enzyme used its profile differed in the number and/or position of at least one fragment. However, there was complete cross-hybridization of Tb and Np DNAs. Hybridization techniques failed to detect Brucella DNA in Dp or Tb phages, or phage DNA in Brucella cells. Extrachromosomal plasmid DNA was not detected.

Improved immunological membrane filter method for detection of food-borne Salmonella strains.

An improved membrane filter method that involves the use of an enzyme-labeled antibody stain has been developed for the rapid detection of Salmonella species in foods. The procedure is carried out directly on a hydrophobic grid-membrane filter without requiring transfer by blotting to nitrocellulose. Pure cultures of 54 Salmonella species and 10 foods artificially contaminated with Salmonella colindale gave a positive reaction in which Salmonella colonies were visible as purple dots. Of 11 nonsalmonella organisms, only Citrobacter freundii reacted with Spicer-Edwards antiserum. Of 22 naturally contaminated food samples, 10 were positive for both the hydrophobic grid-membrane filter procedure of the Association of Official Analytical Chemists and the improved enzyme-labeled antibody stain method, and there was perfect agreement between the methods. Of these 10 positive samples, one was negative by the Health Protection Branch method; of the negative samples, two were positive by this latter method. The improved enzyme-labeled antibody stain method allows detection of Salmonella spp. in foods within 48 h, requires little equipment, and is inexpensive, easy to perform, and suitable for automated detection.

Pesquisa de alguns grupos de microrganismos em saladas com maionese adquiridas em restaurantes, lanchonetes e "rotisseries". / Research of some groups of microrganisms in salads with mayonnaise acquired in restaurants, snack bars and rotisseries

Em vinte amostras de saladas com maionese foram efetuadas as contagens de bacterias mesofilas e psicrofilas. Staphylococcus aureus, Bacillus cereus, bolores e leveduras, a determinacao do numero mais provavel (NMP) de bacterias coliforme totais de Escherichia coli e de estreptococos fecais, bem como a pesquisa de salmonelas.A contagem de bacterias mesofilas variou de 2,64 x l0 elevado a 4 a > ou igual a 3 x l0 elevado a 7 /g do produto. Quanto as bacterias psicrofilas, as contagens variaram de < 10 a > ou igual 3 x 10 elevado a 7 /g. Para S. aureus, as contagens oscilaram de < 10 elevado a 2 a 4 x 10 elevado a 5 /g do alimento, enquanto que para B. cereus os numeros minimo e maximo foram < 10 elevado a 2 e > ou igual 3 x 10 elevado a 4 /g, respectivamente. Para bolores e leveduras, as contagens variaram de 7,l x 10 elevado a 2 a 3,7 x 10 elevado a 6 /g. Com relacao ao NMP de coliformes totais e estreptococos fecais, os resultados obtidos mostraram-se compreendidos entre < 0,03 e > ou igual 4,3 x 10 elevado a 5 /g. Quanto ao NMP de E. coli os numeros minimo e maximo obtidos foram respectivamente de < 0,03 e > ou igual 2,4 x 10 elevado 4 /g de salada com maionese. Tais constatacoes indicam a ocorrencia de contaminacao inclusive por microrganismos de origem fecal.Todas as amostras revelaram-se negativas para bacterias do genero Salmonella