摘要:

SUMMARY:Colony counts in 48 hr. at 37° were much higher in farm water supplies derived from rivers, streams, canals and unprotected wells than in water from springs, protected wells, upland surface waters and chlorinated supplies. Relatively few of the upland surface waters had counts exceeding 102/ml., but the counts for unprotected shallow wells were as high as those for rivers, streams and canals.There was a general association between colony counts at 37° and presumptive coli‐aerogenes counts, but high 37° colony counts could not always be accepted as an indication of sewage or faecal pollution and obviously polluted waters sometimes had low colony counts at 37°.Irrespective of the magnitude of the colony count, the majority (63%) of the colonies were Gram‐negative rods, though they formed a higher proportion of the flora in high than in low count waters. Aerobic spore‐forming rods constituted nearly 20% of the colonies and micrococci 10%, while Gram‐positive rods which did not form spores were present in small numbers at all colony count ranges. Streptococci were relatively rare, forming less than 2% of the colonies.Approximately 25% of the 1,912 cultures isolated from colonies at 37° produced acid and gas in MacConkey's broth at 37°, but 7% of the 488 presumptive coli‐aerogenes cultures were aerobic spore‐forming rods. Typical coli‐aerogenes bacteria constituted 38% of the Gram‐negative rods and 24% of all the colonies examined. Surprisingly few colonies resembledBact. colitype I in producing acid and gas in MacConkey's broth at 44°, and 13 (6.8%) of the 192 which did so were aerobic spore‐formers resemblingBacillus macerans.Slightly over a third of the cultures produced an acid or proteolytic reaction in litmus milk within 2 days at 22°.The results indicate that the colony count in 48 hr. at 37° does not contribute much useful information additional to that obtained from the presumptive coli‐aerogenes test at 37°

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04622.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

SUMMARY:While developing a standard mouse test for anti‐tuberculosis activity using intracerebral infection and a subjective criterion for assessing activity based on visual estimates of the extent of the lung lesions, young mice were found to be less resistant than older mice but male and female mice of similar ages and weights were equally susceptible. The bovine Ravenel and the human H418 strains ofM. tuberculosiswere selected as being more virulent and reliable than the H37Rv strain. Kirchner's medium was chosen out of three media equally good for yielding virulent cultures from which to grow cultures for inoculation. The ability of the standard mouse test devised, notwithstanding the use of a subjective criterion for assessment, to reveal activity in drugs whose effectiveness has been revealed by other methods, was demonstrated. A brief description is given of the disease produced in mice following intracerebral inoculatio

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04623.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

SUMMARY:An improved ion‐exchange column for producing stable silica sols is described. Best results were obtained with a sulphonic‐polystyrene resin. The storage life of sols so produced may be extended to as much as two months by refrigeration and acidification with hydrochloric acid. Silica sol has a buffering action in the region of pH 2. Silica gel media prepared from such sols are comparable in cost with agar me

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04624.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

SUMMARY:An apparatus is described in which sufficient microbe‐free timothy grass to make ‘silage’ on a laboratory scale was grown. In one experiment the chemical changes which occurred during the period of ensiling were measured. They could be attributed only to the metabolism of the plant

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04625.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

SUMMARY:In preliminary experiments with grass silage made in the laboratory under controlled conditions bacterial numbers reached a peak earlier in silage held at 30° than at 22°, although maximum numbers tended to be greater at the lower temperature. Wilting the grass before it was ensiled delayed bacterial action, while chopping the grass hastened the action and helped to ensure a low pH in the silag

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04626.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

SUMMARY:For the enumeration of lactobacilli on grass and in silage the following medium has shown promise: peptone, meat extract and glucose, 10 g. each; tomato extract, 200 ml.; yeast autolysate, 50 ml.; Tween 80, 0.5 ml.; agar, 15 g., in a final volume of 1 1. and containing acetic acid/sodium acetate buffer in 0.2M concentration; pH 5–4. The medium was adjusted to pH 5–4 before sterilization and the requisite amount of concentrated pH 5.4 acetate buffer added just before plating. Double laver plates were used.The only other silage organisms which in this medium formed colonies comparable in size with those of lactobacilli were heterofermentative streptococci and a micrococ

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04627.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

SUMMARY:The dominant anaerobes isolated from grass silage were proteolytic and lactate‐attacking species. Dilution methods for the enumeration of vegetative cells and spores of both types, using selective media, are describe

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04628.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

SUMMARY:Ignoring wasted material at the surface and sides, the variation in pH in six months old pit silage was smaller from side to side than from top to bottom. At the 2‐foot level, where the best quality silage was found, variation was very slight. A correlation was found between pH and the logarithm of the microscopical count of bacteria, the total number of bacteria falling with decreasing p

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04629.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04630.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

SUMMARY:A co‐ordinated experiment was carried out at two centres, in which colony counts from raw milk samples determined by the roll‐tube and Petri dish methods were compared. A bulk medium was standardized for both laboratories, as also were details of technique. Statistical analyses showed that roll‐tube counts were generally lower than the corresponding Petri dish counts, but the difference varied considerably from milk to milk. The variation between replicate sub‐samples was about the same for both methods. Experience and the results both indicate that roll‐tubes were slightly more difficult to count than Pet

ISSN:0370-1778    

DOI:10.1111/j.1365-2672.1951.tb04631.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY