Survival of Enterobacter cloacae and Pseudomonas paucimobilis in yoghurts manufactured from cow's milk and soymilk during storage at different temperatures.

The survival of two microbial contaminants, Enterobacter cloacae and Pseudomonas paucimobilis, in yoghurts manufactured from cow's milk and soymilk was investigated during storage for 45 days at 4 and 12 degrees C. Sensory panel tests performed before microbiological investigation, showed that the flavor of soy-yoghurts made with cocoa powder or malt added did not have the beany taste of soy beans. Both contaminants were significantly resistant to low pH values during storage for 32 days at 4 degrees C. The survival at 4 degrees C was remarkable in both plain and flavored yoghurts and a population close to 10(2) C.F.U./ml was observed after 38 days of storage. Experiments performed with soymilk yoghurts showed an enhanced survival of P. paucimobilis at 4 degrees C compared to the storage in cow's milk yoghurts; microbial values were close to 7-8 x 10(6) C.F.U./ml after 16 days. Soymilk exhibited a protective effect on L. delbrueckii subsp. bulgaricus and S. thermophilus at 12 degrees C and, compared to the survival in cow's milk yoghurts, a larger number of viable cells of both probiotic microorganisms (10(6) and 10(8) C.F.U./ml, respectively) were observed after 36 days of storage.

Note: susceptibility to chlorine of Aeromonas hydrophila strains.

The susceptibility of five Aeromonas hydrophila strains and one Escherichia coli strain to chlorine was studied under carefully controlled laboratory conditions. Of the Aer. hydrophila strains, two were from untreated water, two from tap water (immediately downstream of a water treatment plant) and one from the DSM collection. The study included disinfectant concentration (0.1, 0.2 and 0.5 mg l-1), pH (6, 7 and 8) and temperature (4, 21 and 32 degrees C) as controlled variables. The results indicated that the untreated water strains, the DSM strain and the E. coli strain were inactivated within 1 min of chlorine treatment. The strains from chlorinated water (TW11 and TW27) showed a different susceptibility to chlorine disinfection, the rate of inactivation being greater at pH6 than at pH8 for both strains. Under the standard conditions of temperature 21 degrees C, pH7 and chlorine concentration 0.2 mg l-1, an increase or decrease of approximately 1 log unit in the number of bacteria did not affect the kill rate of the strains TW11 and TW27.

Protection of young chicks against Salmonella kedougou by administration of intestinal microflora.

One-day old chickens were treated with a faecal suspension and faecal samples were cultivated either in non-selective broth (Viande Levure broth) or in broths selective for Lactobacillus spp., Bacteroides spp., faecal enterococci and coliforms. The chickens were infected 48 h later with 10(4) colony-forming units of nalidixic-acid resistant Salmonella kedougou and examined seven days later. Faecal suspensions and faecal samples cultivated in non-selective broth exerted a protection against Salmonella infection; no protection was obtained with faecal samples cultivated in selective broths, administered either alone or in combination.

A microbiology investigation on probiotic pharmaceutical products used for human health.

Many and different probiotic pharmaceutical products are presently commercialised in the world. On this regard, a microbiological investigation was carried out to screen the microorganisms incorporated into these products, commonly used for human health. After determination of the cell number and viability of bacteria, several experiments were performed in vitro in order to characterise the microorganisms and to evaluate their probiotic value. Among all the strains identified, best results were obtained with Lactobacillus rhamnosus, Enterococcus faecium and Saccharomyces cerevisiae as far as regards growth rates, pH and bile salts tolerance. Moreover, the identification profiles of microorganisms showed a better reliability for the products containing a single species whereas the ones composed of different strains were usually not satisfactory. In some cases, the presence of Lactobacillus and Saccharomyces species was in disagreement with the claimed composition of the product and some species of lactobacilli, bifidobacteria and streptococci were found not viable. In defined mixed cultures experiments, the antagonism of Lactobacillus acidophilus and Enterococcus faecium versus Yersinia enterocolitica was demonstrated and explained as acid and/or antimicrobials production.

The effect of some antibiotics on Enterococcus faecium SF 68 inoculated in germ-free mice.

A strain of Enterococcus faecium SF 68 (sensitive to penicillin, tetracycline, virginiamicin and tylosin, but resistant to streptomycin) was administered to five groups of germ-free mice. Each group was subsequently given 40 micrograms/ml and then 80 micrograms/ml of a single antibiotic. The following determinations were made: a) colonization of the bacterial strain before and after administration of the antibiotic and b) the MICs in the original strain and after administration of the antibiotic (80 micrograms Iml). The results show that in the mice treated with streptomycin, colonization is not influenced by the antibiotic treatment; in mice treated with antibiotics to which the strain is sensitive, the colonization increases in proportion to the level of the antibiotic resistance (tylosin and tetracycline).

Anaerobic facultative bacteria isolated from the gut of rabbits fed different diets.

Anaerobic facultative bacteria colonizing the intestinal tract of conventional rabbits fed three different diets (standard pellet, hay and pellet/hay mixture) were enumerated in brain heart infusion agar. Colony counts recovered from homogenized samples of small intestine, caecum and rectum differed with reference to the diet given. Among anaerobic groups, identified from rabbit fed pellet/hay mixture, Enterococci (E. faecalis, E. avium, E. faecium and E. durans) represented the predominant flora. Enterobacters (E. cloacae and E. aerogenes) accounted for about 10 to 25% of the bacteria in the rectum and colon respectively, whereas Staphylococci (S. intermedius, S. epidermidis and S. lentus) represented 11% of the bacteria isolated from colon.

Survival of bifidobacteria from human habitat in acidified milk.

Some industrial preparations from milk, such as yogurt, contain bifidobacteria as an additional probiotic element. The acidic environment of these products affects the viability of the bifidobacteria. The survival in acidic environment of one-hundred and ten bifidobacterial strains from human habitat was tested.

The incidence of Listeria spp. in soft cheeses, butter and raw milk in the province of Bologna.

Samples of soft cheese, butter and raw milk were examined for Listeria species. Listeria monocytogenes (serotype 1, haemolytic and virulent for mice) and L. innocua (the only other Listeria sp. isolated) were each found in 2/21 (1.6%) of soft cheese samples. Five per cent of butter samples were contaminated with L. innocua. No Listeria spp. were detected in 40 raw milk samples. The results were compared with similar studies in Italy and abroad.

Microbiological quality of fresh pasta dumplings sold in Bologna and the surrounding district.

The microbiological quality of fresh pasta dumplings sold in Bologna and the surrounding district was evaluated. A total of 60 lots (300 subsamples) of fresh pasta dumplings, both 'home-made' and manufactured, were analysed for aerobic plate count (APC), coliforms (total and fecal), Staphylococcus aureus, Clostridium perfringens and Salmonella spp. Thirty one of the 39 lots of 'home-made' pasta were found to exceed APC standards and six lots exceeded S. aureus standards. Five (24%) and six (29%) lots of the manufactured pasta were found to be unsatisfactory as regards APC standards and S. aureus standards respectively. The results obtained indicated that a high percentage of samples had a contamination of fecal origin. No Cl. perfringens or Salmonella spp. were found.

Isolation of Yersinia enterocolitica and related species from river water.

One hundred and twenty samples of river water collected from sampling sites in the period between December 1986 and December 1987 were examined for the presence of Yersinia enterocolitica and related species. Among a total of 26 Yersinia strains isolated the following species were recognized: Y. enterocolitica, 12 strains, Y. intermedia, 5 strains, Y. frederiksenii, 2 strains, Y. kristensenii and Y. aldovae, 1 strain each; 5 were atypical Yersinia strains (rhamnose+, citrate+, alpha-methyl-D-glucoside+). Although the Yersinia isolates belong to the so-called "environmental" serotypes, which are usually considered as non-pathogenic for humans, Y. enterocolitica biotype 1, serotype 0:7.8, lysotype X0, which has previously been associated with gastro-intestinal infection in Italy, was found to be present. Statistical evaluation of our data showed that the presence of Yersinia spp. and the presence of total or fecal coliforms are unrelated.

Species of the genus Bifidobacterium in the feces of human adults.

In order to obtain information about the intestinal bifid microflora of human adults, a total of 288 strains of bifidobacteria isolated from 29 out of 36 fecal specimens were studied. Their assignment to known species of the genus Bifidobacterium was based on polyacrylamide gel electrophoretic analyses of soluble cellular proteins. The strains were classified as B. adolescentis, B. bifidum, B. catenulatum, B. longum, B. pseudocatenulatum. The distribution of these species is reported.

Species of the Bifidobacterium in the feces of infants.

A total of 907 strains of bifidobacteria isolated from the feces of breast-fed and artificial milk-fed infants were studied. Their assignment to known species of the genus Bifidobacterium was primarily based on DNA homology relationships. The strains were classified as B. bifidum, B. breve, B. catenulatum, B. dentium, B. infantis, B. longum and B. pseudocatenulatum. The distribution of these species is reported.

Presence of bifidobacteria in the rumen of calves fed different rations.

A study was made on the numbers and species of bifidobacteria present in the rumen of calves fed high-roughage and high-concentrate diets. With the roughage ration the bifidobacteria were not detectable in a 10(-3) dilution, whereas with the concentrate ration their number was high, usually in the order of 10(8) to 10(9)/ml of rumen fluid. The species most represented, identified by means of deoxyribonucleic acid-deoxyribonucleic acid hybridization tests, included Bifidobacterium ruminale, Bifidobacterium globosum, and an apparently new species.