Relationships between development of ropy condition and the initial viable population, incubation temperature, incubation period, viable cell counts, pH, gas production in steamed whole milk inoculated with Klebsiella planticola isolated from ropy milk were investigated. The results obtained were as follows: (1) The period required to develop detectable ropiness in milk when incubated at 10°C was reduced in inverse proportion to the viable population of the inoculum, (2) The K. planticola isolate developed ropiness in milk when incubated at 10°C to 25°C, whereas they did not at 30°C. (3) The period required to develop detectable ropiness in milk was prolonged as the incubation temperature was lowered. (4) The rope length became longer as the incubation period was prolonged. After attaining the maximum length, however, the rope became shorter as the incubation was prolonged. (5) Ropy condition became detectable when the viable cell count of K. planticola in milk reached 10⁷/ml, reached the maximum when it reached 10⁸/ml, and then disappeared when it became more than 10⁸/ml. (6) The rope became longer as the pH of milk was lowered. After reaching the maximum length, however, the rope became shorter as the pH of milk was further lowered. (7) The ropy condition disappeared when gas production was observed in milk when incubted at 15°C to 25°C. When incubted at 10°C, however, no gas production was observed for 168 hours.

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Seventy-two Salmonella strains including eight serovars isolated from 12 outbreaks of human enteritis during the period from 1980 through 1990 were characterized on the basis of their plasmid profiles and antibiotic resistance. Out of 72 isolates, a total of 42 including four serovars from six outbreaks carried plasmids; however, no plasmid was found in any of the isolates from the remaining six outbreaks. The plasmid profiles of the isolates carrying plasmids showed the identical or similar patterns except those from two outbreaks. In these two outbreaks, one gave some isolates not carrying any plasmid and the other caused by S. Litchfield gave two different plasmid profiles, although all the isolates demonstrated the same antibiotic resistance. Thus, we concluded that the isolates in the latter outbreak belong to different bacterial clones. In these results, plamid analysis proved to be a useful tool for epidemiological investigation. Among the 72 isolates, twenty strains were resistant to two or more antibiotics, although the antibiotic resistance was not transferable by conjugation among these strains.

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Extracts of tea leaves, mushrooms and vegetables were examined for the antibacterial activity against staphylococci. “Bancha”, “sencha” and “gyokuro” inhibited the growths of most of 25 staphylococcal strains (13 species) tested. The antibacterial activity was found also in “hojicha”, “matcha”, oolong tea, pu-erh tea and black tea, but to a lesser extent. Among mushrooms, “matsutake” showed an antibacterial activity against staphylococci with a considerable broad spectrum. “Shiitake”, “nameko” and “hiratake” were effective on a few staphylococcal strains. Among vegetables, garlic bulb, “gyoja ninniku”, “nira” and burdock showed antibacterial activities. Garlic bulb was effective on many strains of staphylococci. Many of the extracts showing antibacterial activities against staphylococci were effective also on micrococci and Streptococcus pyogenes. A few extracts were effective on Bacillus cereus, Salmonella Typhymurium and some other micro-organisms. The antibacterial activity of tea leaf extracts against Staphylococcus aureus Cowan I was bacteriocidal and resistant to heating at 100°C for 15 min, while that of “matsutake” extract was bacteriostatic and heat labile.
The antibacterial activity of extracts of garlic bulb, “gyoja ninniku” and “nira” was bacteriostatic and heat labile against Micrococcus varians.

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[in Japanese]

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