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Cited by 4 publications
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Reviews of the progress of dairy sciencepreformed enzymes, are added to chemically defined substrates, giving clear-cut results. A clockwork automatic bacteriological inoculating device has been devised by Fuson & Marcus (20). An ingenious device(2i), patented in the U.S.A., for counting bacterial colonies, consists of a fountain pen connected to an electro-magnetic counter which registers each time the pen touches the Petri dish or roll-tube. Hannay (22) has described a new type of laterally illuminated colony counting chamber. British Standards for Petri dishes (23) have been issued recently. A microtechnique for the growth of many cultures, particularly for assay work, in one Petri dish has been developed by Turner-Graff(24). Newbould's(25) roll-tube spinner is designed to use cheap, easily obtainable vials or bottles. A suggestion contributing, in the long run, to economy is that of using rigid, seamless tubes of Kraft paper instead of the paper wrappings commonly used for individual sterile pipettes (26); Lack (27) has described a hot box for microcultures, which dispenses with a water jacket since the heating element consists of glass electrothermal heating tape. From America have come details of a simple large-scale anaerobic culture apparatus (28) utilizing a milk can as the main container, and of the uses to which spun glass (29) may be put as an air-filtering medium for bacteriological purposes.The text of the papers read, and the discussion, at a Symposium of the Institute of Biology in London in 1951 have been published under the title Freezing and Drying^); diversity of opinion and lack of collaboration and understanding between bacteriologist and vacuum engineer was apparent concerning even such vital factors as the plugs for drying tubes. Fry & Greaves (31), working mainly with a paracolon bacillus over a 3-year period, have shown that the nature of the suspending medium is one of the most important factors determining the survival rate of bacteria dried in vacuo; the addition of 5-10% of glucose or lactose increased the percentage survival. Young cultures were less resistant to drying than older cultures, but the cell concentration appeared to be of little consequence. ' Mist desiccans' (1 part broth, 3 parts serum with 7-5% added glucose) proved a satisfactory suspending medium for sensitive organisms such as Neisseria gonorrhoea. Briggs' observations (32) on the freeze-drying of lactobacilli are in almost complete agreement with those of Fry & Greaves; using strains of Lactobacillus acidophilus and L. bulgaricus, which were particularly sensitive to freeze-drying, she obtained with her suspending media survival rates of over 10% after 18 months' storage; her work is being continued with other species of lactobacilli subsequently tested to determine whether selection has taken place, although this should not be a danger except where very low survival rates are experienced. Sharpe (33) has tested the precipitin and agglutination reactions of cultures of L. acidophilus and L. bulgaricus which had b...
Reviews of the progress of dairy sciencepreformed enzymes, are added to chemically defined substrates, giving clear-cut results. A clockwork automatic bacteriological inoculating device has been devised by Fuson & Marcus (20). An ingenious device(2i), patented in the U.S.A., for counting bacterial colonies, consists of a fountain pen connected to an electro-magnetic counter which registers each time the pen touches the Petri dish or roll-tube. Hannay (22) has described a new type of laterally illuminated colony counting chamber. British Standards for Petri dishes (23) have been issued recently. A microtechnique for the growth of many cultures, particularly for assay work, in one Petri dish has been developed by Turner-Graff(24). Newbould's(25) roll-tube spinner is designed to use cheap, easily obtainable vials or bottles. A suggestion contributing, in the long run, to economy is that of using rigid, seamless tubes of Kraft paper instead of the paper wrappings commonly used for individual sterile pipettes (26); Lack (27) has described a hot box for microcultures, which dispenses with a water jacket since the heating element consists of glass electrothermal heating tape. From America have come details of a simple large-scale anaerobic culture apparatus (28) utilizing a milk can as the main container, and of the uses to which spun glass (29) may be put as an air-filtering medium for bacteriological purposes.The text of the papers read, and the discussion, at a Symposium of the Institute of Biology in London in 1951 have been published under the title Freezing and Drying^); diversity of opinion and lack of collaboration and understanding between bacteriologist and vacuum engineer was apparent concerning even such vital factors as the plugs for drying tubes. Fry & Greaves (31), working mainly with a paracolon bacillus over a 3-year period, have shown that the nature of the suspending medium is one of the most important factors determining the survival rate of bacteria dried in vacuo; the addition of 5-10% of glucose or lactose increased the percentage survival. Young cultures were less resistant to drying than older cultures, but the cell concentration appeared to be of little consequence. ' Mist desiccans' (1 part broth, 3 parts serum with 7-5% added glucose) proved a satisfactory suspending medium for sensitive organisms such as Neisseria gonorrhoea. Briggs' observations (32) on the freeze-drying of lactobacilli are in almost complete agreement with those of Fry & Greaves; using strains of Lactobacillus acidophilus and L. bulgaricus, which were particularly sensitive to freeze-drying, she obtained with her suspending media survival rates of over 10% after 18 months' storage; her work is being continued with other species of lactobacilli subsequently tested to determine whether selection has taken place, although this should not be a danger except where very low survival rates are experienced. Sharpe (33) has tested the precipitin and agglutination reactions of cultures of L. acidophilus and L. bulgaricus which had b...
Incidence and Significance of Thermoduric Bacteria in Farm Milk Supplies: A Reappraisal and Review
CONTENTS PAGE 26'i r i 1 hermoduric bacteria in farm milk supplies miportance of using a suitable brand of peptone in the plating medium, w liich should be at a pH of 7.5, while iiicubation should preferably be a t 28" for 96 h. The results of these findings should be incorporated in future revisions of standard techniques. Donovan & Vincent (1955) recommended the use of a double indicator (broniocresol purple and phenol red) agar medium for estimating the numbers and types of thermodurics, while Leali (1958) used a TTC medium which he claimed facilitated and reduced the error of counting colonies of thermoduric bacteria.
Summary The results of five experiments designed to show the magnitude and rate of build‐up of thermoduric organisms on dairy equipment indicate that:— (1) Milk rinses of both hand milking utensils and milking machine clusters may contain over 10,000 thermoduric organisms per ml. within 2 to 4 days of absolute sterilisation, when the equipment is simply washed after milking in hot water or hot detergent and where the conditions of milking allow the introduction of a few thermoduric organisms into the milk at each milking. (2) The build‐up of thermoduric organisms on utensils is mainly due to multiplication of the organisms in the milk‐scale or milky‐film and is hardly affected by cumulative additions during milking. (3) The thermoduric flora increased more rapidly and attained greater numbers on the rough surfaces of a galvanized pail than on a smooth, seamless pail. (4) There was no appreciable build‐up of thermoduric bacteria within a month on hand milking utensils consistently sterilised by steam or hypochlorite. (5) Washing milking pails in warm water at 120°F. led to a rapid build‐up of non‐heat‐resisting organisms, but not to such a rapid build‐up of thermoduric organisms. (6) Washing milking pails in hot detergent solution at 160°‐170°F. did not result in anything like as marked a build‐up of heat‐labile organisms, but the build‐up of thermoduric organisms was appreciable by the third week. (7) Under the conditions of our experiments there was no more rapid or greater build‐up of thermoduric organisms on pails held between milking at summer temperatures than at winter temperatures. This conclusion is tentative and further information should be obtained under varied farm conditions. Our experiments were in the main confined to hand milking utensils and we have no direct evidence to decide whether the thermoduric build‐up is more rapid or of a greater magnitude on inefficiently sterilised milking machine clusters.
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