Showing papers in "Journal of Applied Microbiology in 1959"
TL;DR: The plate count of bacteria in the root region increased during the growing period of the plants; superphosphate produced a greater increase, which was probably due to increased plant growth, as no such effect was observed in uncropped soil.
Abstract: SUMMARY: The bacteriology of the root region of oat plants grown under controlled conditions has been studied by means of improved techniques for separate estimation of the microfloras of the rhizosphere soil and of the root surface. The plate count of bacteria in the root region increased during the growing period of the plants; superphosphate produced a greater increase, which was probably due to increased plant growth, as no such effect was observed in uncropped soil.
The numbers of acid producing and dicalcium phosphate dissolving bacteria were increased in the root region, but the latter were not preferentially stimulated. Dressings of superphosphate and dicalcium phosphate also did not preferentially stimulate either group. No evidence was obtained, by the plate method used, of the presence of organisms capable of dissolving variscite, strengite, or gafsa rock phosphate, although the plants showed appreciable response to gafsa rock phosphate.
115 citations
TL;DR: In this article, over a hundred isolates which produced haloes around their colonies on dilution plates containing calcium carbonate or dicalcium phosphate have been obtained in pure culture from the root region of the oat plant.
Abstract: SUMMARY: Over a hundred isolates which produced haloes around their colonies on dilution plates containing calcium carbonate or dicalcium phosphate have been obtained in pure culture from the root region of the oat plant. Of these, more than 50% were pleomorphic, and this group had the highest proportion of isolates which could produce clear zones on agar media containing either calcium carbonate, dicalcium phosphate, tricalcium phosphate, freshly precipitated hydroxyapatite or basic slag. None of the isolates showed dissolving ability on agar media containing gafsa rock phosphate, variscite, strengite or taranakite. However, when an analytical method was used, 82% of the isolates tested proved able to release phosphate from gafsa rock phosphate, though to a much lesser extent than from dicalcium phosphate. None of the isolates tested by this method released phosphate from variscite, strengite or taranakite.
The nature of the organic acids produced from glucose by 26 of the isolates was also investigated. The majority produced mainly lactic acid, but a few also gave an acid with chromatographic properties similar to those of 2-keto-gluconic acid.
105 citations
TL;DR: From various chilled meats, twenty-eight strains of coli-aerogenes bacteria and one Aeromonas were isolated which grew well at +1±5° and some at −1± 5°, and the optimum growth temperature for most of these strains was nearer 37° than 30°.
Abstract: SUMMARY: From various chilled meats, twenty-eight strains of coli-aerogenes bacteria and one Aeromonas were isolated which grew well at +1±5° and some at −1±5°. The optimum growth temperature for most of these strains was nearer 37° than 30°. Nine strains (including the Aeromonas) fermented lactose rapidly, the remainder slowly or not at all. All the strains which fermented lactose rapidly with the production of gas gave positive presumptive coli-aerogenes tests in MacConkey's broth at 30°, but only five were positive at 37°; none was positive at 44°. Because such organisms can attain populations of millions/cm2, they could confuse the interpretation of presumptive coli-aerogenes tests made on chilled meat.
43 citations
TL;DR: Although the soil had been inoculated with effective rhizobia and the clover plants were effectively nodulated only one of the 318 isolates was capable of nodulating subterranean clover, and the majority of the isolates were chromogenic and Gram-negative, produced acid from glucose and ammonia from peptone, and grew best aerobically.
Abstract: SUMMARY: A study of the bacteria from the surfaces of roots of subterranean clover (T. subterraneum L.) and Wimmera rye-grass (L. rigidum Gaud.) revealed that 21 genera were represented among the isolates from clover and 16 genera among those from rye-grass. Bacteria showing branched forms predominated and accounted for 63% of the 151 clover isolates and 78% of the 167 grass isolates. Most of these were identified as Arthrobacter, but from clover a significant proportion were Nocardia-like types. Members of the genera Mycoplana, Micromonospora, Mycobacterium, and Mycococcus were also identified among the branching forms.
Although the soil had been inoculated with effective rhizobia and the clover plants were effectively nodulated only one of the 318 isolates was capable of nodulating subterranean clover. The majority of the isolates were chromogenic and Gram-negative, produced acid from glucose and ammonia from peptone, were catalase-positive and grew best aerobically. Approximately half the isolates liquefied gelatin and produced hydrogen sulphide from peptone.
36 citations
TL;DR: The established techniques for counting mesophilic sulphate-reducing bacteria were inadequate for counting Clostridium nigrificans and attempts to improve the viable counts by using different reducing agents and by altering the basal medium achieved only limited success.
Abstract: SUMMARY: The established techniques for counting mesophilic sulphate-reducing bacteria were inadequate for counting Clostridium nigrificans Attempts to improve the viable counts by using different reducing agents and by altering the basal medium achieved only limited success
31 citations
25 citations
TL;DR: From the mortality curves of Escherichia coli cells heated at 55° in Ringer's solution both Decimal Reduction Times (DRTs) and 99–9% mortality times were obtained, and it was observed that the heat resistance was minimal during that phase.
Abstract: SUMMARY: From the mortality curves of Escherichia coli cells heated at 55° in Ringer's solution both Decimal Reduction Times (DRTs) and 99–9% mortality times were obtained. In terms of these measures of heat resistance, cells harvested from broth cultures 0–8 hr old were more susceptible than those from more mature cultures. The time of commencement and the approximate duration of the logarithmic phase of growth of the organism in broth were determined from growth curves, and it was observed that the heat resistance was minimal during that phase.
Death rates were not always uniform for the whole of a given population. Particularly among young cultures, a period of rapid death was frequently followed by the slower death of a relatively small number of survivors. In one instance only was an initial period of slow death followed by one of more rapid death.
24 citations
TL;DR: On investigating sources of contaminated milk, it was found that the organism was derived chiefly from cans which, after being emptied of milk, had been allowed to stand for a long time before being washed properly and ‘sterilized’.
Abstract: SUMMARY: In a survey of milk obtained from individual farms and creameries, 87% of samples were found to contain fewer than one cell of Bacillus cereus/ml. The remaining 13%, although they all yielded low counts, showed that the organism tended to occur in milk received from particular farms and creameries. On investigating sources of contaminated milk, it was found that the organism was derived chiefly from cans which, after being emptied of milk, had been allowed to stand for a long time before being washed properly and ‘sterilized’. The vegetative cells of B. cereus were shown to form spores readily in thin films of diluted milk, such as may occur in a rinsed can.
24 citations
TL;DR: The tests for faecal contamination in foods, based on ‘indicator species’, should be reconsidered for the following reasons:.
Abstract: SUMMARY: The tests for faecal contamination in foods, based on ‘indicator species’, should be reconsidered for the following reasons. First, in Europe, Escherichia coli is regarded as a specific index of such contamination; but, apparently through the use of antibiotics, the proportion of human faeces containing Klebsiella has risen from 5.2% in 1947 to 48.4% in 1956–7. Moreover, E. coli and other coli-aerogenes organisms may be absent from the gut of certain animals, notably the pig. Second, while the usual methods of counting coli-aerogenes bacteria do not permit the isolation of strains which ferment lactose slowly or not at all (i.e. paracolons), these occur in 35.6% of samples of human faeces. Further, the recommended methods of detecting such strains are not wholly satisfactory. Third, the origin of the coli-aerogenes bacteria is uncertain.
It is thus necessary to consider other organisms which normally inhabit the intestinal tract of humans and other animals. As to Clostridium perfringens, its source is doubtful, for it may come from faeces or from soil, and many foods contain only soil strains. The group D streptococci, on the other hand, are excellent indicators of faecal contamination. They are constant or frequent in the intestines of man and animals, and often more numerous there than coli-aerogenes bacteria. Their specificity as an index of faecal contamination is high and their investigation is easy with the selective media now available. Associated with the coli-aerogenes bacteria, they justify the diagnosis of faecal contamination in a foodstuff.
22 citations
TL;DR: The use of electronic computation in the objective analysis of the chromato-graphic patterns of 90 strains of heterofermentative lactobacilli showed that there was such a spread of properties among the different strains that a division into species was not justifiable.
Abstract: SUMMARY: The use of electronic computation in the objective analysis of the chromato-graphic patterns of 90 strains of heterofermentative lactobacilli is described. The results showed that there was such a spread of properties among the different strains that a division into species was not justifiable.
19 citations
TL;DR: The cleaning efficiency of hosing wooden market fish boxes with cold water, the usual commercial practice, was very low, even when high pressure jets were used, and the internal surfaces could still carry up to 20 × 106 bacteria/cm2 after washing.
Abstract: SUMMARY: The cleaning efficiency of hosing wooden market fish boxes with cold water, the usual commercial practice, was very low, even when high pressure jets were used. After washing, the internal surfaces could still carry up to 20 × 106 bacteria/cm2. Even prolonged steaming failed to sterilize the surfaces. Coryneform organisms accounted for over 50% of the total bacterial flora, although these have usually been reported as present in only low proportions on both fresh and spoiling fish. The major subsidiary groups were species of Achromobacter and Pseudomonas, constituting about 18% and 14% of the population respectively. A few micrococci and flavobacteria were also present.
The conditions of counting, i.e. whether roll tubes or Petri dishes were used, whether incubation was at 0°, 20° or 37°, and whether the media were based on sea or tap water, could markedly influence both the magnitude of the count and the proportions of the different types of bacteria which could be isolated.
TL;DR: Manometric determinations of the 5 day biological oxygen demand of effluents after treatment showed good agreement with the values obtained by the conventional method, the manometric values being usually somewhat higher.
Abstract: SUMMARY: Mixed cultures of bacteria grown in spent gas liquor readily oxidized phenol, o-, m- and p-cresol, catechol, 3-methyl catechol, 4-methyl catechol, resorcinol, 2-methyl resorcinol, and 4-methyl resorcinol. Quinol, pyrogallol and phloroglucinol were more resistant. The optimum temperature was 30° and the best pH range 6·5–7·8. Yeast extract and sterile sewage sludge both increased the rate of growth of organisms in liquor when the inoculum was small. Five phenol oxidizing organisms were isolated in pure culture. Copper in concentrations greater than 1 p/m inhibited both growth and phenol oxidation by one of these.
Mixed cultures grown in an ammonium thiocyanate medium originally inoculated with Thiobacillus thiocyanoxidans oxidized potassium thiocyanate and sodium thiosulphate. Chloride inhibited thiocyanate oxidation in concentrations above 5,000 p/m, although adaptation to 15,000 p/m was possible. Phenol inhibited thiocyanate oxidation in concentrations of 300 p/m or more. Mixed cultures grown on sodium thiosulphate oxidized sodium trithionate and tetrathionate, potassium pentathionate and hexa-thionate, and potassium and ammonium thiocyanate
Manometric determinations of the 5 day biological oxygen demand of effluents after treatment showed good agreement with the values obtained by the conventional method, the manometric values being usually somewhat higher.
TL;DR: Comparative studies with routine faeces specimens showed that selenite broth was an efficient selective medium with MacConkey's agar; but much better results were obtained when it was combined with deoxycholate-citrate agar.
Abstract: SUMMARY: Studies of growth curves of enterobacteria in selenite broth containing different carbohydrates showed that whereas mannitol and lactose brought about a steep fall in coli-aerogenes bacteria, mannitol improved the growth of Salm. typhi-murium. With mixed cultures of Cit. freundii I and Salm. typhi-murium the presence of lactose, utilizable by the former, adversely affected the viable count of the latter.
Comparative studies with routine faeces specimens showed that selenite broth was an efficient selective medium with MacConkey's agar; but much better results were obtained when it was combined with deoxycholate-citrate agar. Gentian violet introduced into selenite broth improved its selectivity for most Salmonella types when MacConkey's agar was used for final isolation.
TL;DR: Comparisons are given of the output of sorbose from 3 litre cultures of Acetobacter suboxydans grown in a sorbitol medium in batch and continuous culture.
Abstract: SUMMARY: Comparisons are given of the output of sorbose from 3 litre cultures of Acetobacter suboxydans grown in a sorbitol medium in batch and continuous culture. An estimate is given of the investment value of a continuous process of sorbose production relative to the batch process.
TL;DR: The action of various concentrations of nisin on the development of cells and spores from untreated and heated suspensions of Clostridium welchii added to gelatine has been investigated, using a tube colony count technique.
Abstract: SUMMARY: The action of various concentrations of nisin on the development of cells and spores from untreated and heated suspensions of Clostridium welchii added to gelatine has been investigated, using a tube colony count technique. The development of vegetative cells was prevented by the presence of 2 Reading Units (R.U.) of nisin/ml of the final culture medium, although the effective concentration may have been 6 R.U./ml. Approximately 40 R.U./ml prevented colony formation from spores. Gelatine containing nisin was dried. A considerable proportion of the activity of the antibiotic was still present after storage for 5 weeks.
TL;DR: Neither Bacteroides nor Bifidibacterium can be considered suitable as an indicator of the contamination of foods with bacteria of faecal origin and of the subsequent growth of these bacteria therein.
Abstract: SUMMARY: The suitability, as indicators of the faecal contamination of foods, of two types of obligately anaerobic nonsporeforming bacteria which are very numerous in faeces, viz. members of the genera Bacteroides and Bifidibacterium, was tested. For the counting of Bacteroides, Beerens’bile-azide agar (1957) enriched with 10% (v/v) of blood, and incubated in oval cross section tubes, was found useful. Bifidibacterium could be counted very well in Frisell's tomato-azide agar (1951), incubated in the same way. Both media being not too selective, confirmation of representative numbers of colonies was necessary. After microscopical examination, the biochemical study of properties such as catalase reaction, oxygen tolerance, carbohydrate fermentation and nitrate reduction may be required.
The 3 Bacteroides strains tested died off rather rapidly when present in sterile ice cream under conditions where Enterobacteriaceae and faecal streptococci increased in numbers. Accordingly they were never found in considerable numbers in some 25 samples of food which appeared to contain very high numbers of other bacteria of faecal origin. The 8 Bifidibacterium strains investigated appeared more resistant. However, under conditions permitting growth, they increased less than the Enterobacteriaceae and faecal streptococci; and where the latter did not increase but did survive, the Bifidibacterium decreased in numbers. In line with these findings Bifidibacterium was not even found in numbers of the order of 10/g in the 25 samples of food mentioned above. Neither Bacteroides nor Bifidibacterium can therefore be considered suitable as an indicator of the contamination of foods with bacteria of faecal origin and of the subsequent growth of these bacteria therein.
TL;DR: The resistance to drying under atmospheric conditions of Escherichia coli cells suspended in water, broth and horse serum was investigated and it was unlikely that the clearer chromatin staining obtained with cells from young than from old cultures could be attributed to the occurrence of less disruption of the former during drying of the films.
Abstract: SUMMARY: The resistance to drying under atmospheric conditions of Escherichia coli cells suspended in water, broth and horse serum was investigated. Cells from cultures in the early (logarithmic) growth phase were more susceptible than older cells, and this, together with the fact that the strain of E. coli used was very sensitive to drying, even in a protective menstruum such as horse serum, made it unlikely that the clearer chromatin staining obtained with cells from young than from old cultures could be attributed to the occurrence of less disruption of the former during drying of the films.
TL;DR: The results for a series of fortnightly samples from 11 farm water supplies showed a marked seasonal variation in the incidence of different types isolated at 30°; E. coli I formed a higher proportion in summer than in winter, while 37° negative strains of Klebsiella and Citrobacter formed aHigher proportion in winter than in summer.
Abstract: SUMMARY: A series of 825 cultures of coli-aerogenes bacteria isolated at 30° and a series of 735 cultures isolated at 37° from 645 samples of farm water supplies were classified according to the recommendations of the Coliform Sub-Committee of the Society for Applied Bacteriology (Report, 1949). Klebsiella constituted 50% of the cultures isolated at 30°, whereas Escherichia coli I was the dominant type, forming 57%, among the cultures isolated at 37°. It would thus appear that isolation at 30° is as selective for Klebsiella as isolation at 37° is for Escherichia. Coli-aerogenes organisms, mainly 37° negative strains of Citrobacter freundii I and K. cloacae, were found in waters of high sanitary quality derived from protected springs and wells; but the coli-aerogenes microflora of polluted water was dominated by E. coli I, which formed 43% of the isolates at 30° and 76% of those at 37°. The results for a series of fortnightly samples from 11 farm water supplies showed a marked seasonal variation in the incidence of different types isolated at 30°; E. coli I formed a higher proportion in summer than in winter, while 37° negative strains of Klebsiella and Citrobacter formed a higher proportion in winter than in summer.
TL;DR: While some strains of all the coli-aerogenes types isolated showed growth, though sometimes scanty, on yeast-dextrose agar in 5 days at 3—5°, the majority of the strains of K. cloacae showed luxuriant growth under these conditions and can be considered as typical facultative psychrophiles of milk.
Abstract: SUMMARY: When 108 samples of individual farm milk supplies were held at 3—5° for 72 hr, 35·2% showed increases in coli-aerogenes organisms of over one-hundredfold and 10·2% increases of more than one-thousandfold The coli-aerogenes microflora after refrigeration was dominated by Klebsiella cloacae and K aerogenes I While some strains of all the coli-aerogenes types isolated showed growth, though sometimes scanty, on yeast-dextrose agar in 5 days at 3—5°, the majority of the strains of K cloacae showed luxuriant growth under these conditions and can be considered as typical facultative psychrophiles of milk
TL;DR: In this paper, the physical processes occurring when cotton articles are sterilized in metal drums or bare packages in an autoclave are discussed, with special reference to the case where a good vacuum is drawn before the admission of steam.
Abstract: SUMMARY: In this paper some of the physical processes occurring when cotton articles are sterilized in metal drums or bare packages in an autoclave are discussed, with special reference to the case where a good vacuum is drawn before the admission of steam. It is shown that under these conditions the heating will be quick, uniform, regular and reversible, and that no separate drying-off period should be needed. Calculation of the temperatures and moisture contents reached during the ‘quasiequilibrium’period shows that the ‘superheating’of the cotton is self-limiting, can never exceed a few degrees Centigrade, and will not give rise to serious weakening of the cotton. Calculation of the rate of irreversible penetration of moisture into the contents of the drum shows that this can easily be limited to the wrapping layer. Information is given on the ‘heat-tendering’of cotton, and the advantages of using a good vacuum are summarized.
TL;DR: The difference between parallel plating on these media and on the high sugar medium yielded useful information about sources of casual contamination, and it is suggested that the above would also be largely applicable to other sugar-rich concentrates of not less than 50° Brix.
Abstract: SUMMARY: To select and count the sugar tolerant yeasts which ferment sixfold concentrated orange juice, a high sugar agar medium was developed which contains 50% of glucose, 1% of citric acid and 1% of Tryptone; it is incubated for 4–5 days at 25°.
The medium has disadvantages: it is troublesome to prepare, and colonies grow slowly and are translucent. These properties result directly' from the high sugar concentration, on which the selective action of the medium depends.
Counts on this medium have been compared with those on potato dextrose or nutrient dextrose agars (with 2% and 1% of glucose respectively), with yeasts isolated from fermenting concentrate, in pure culture, and under various practical conditions. As a rule, the counts were virtually the same on the different media; nutrient dextrose agar occasionally failed to record small numbers of these yeasts. If the two low sugar media were acidified to pH 3·5 the counts were reduced.
Potato dextrose agar recorded, besides the above yeasts, sugar intolerant yeasts entering from dirty machines or through bad canning practice: nutrient dextrose agar recorded bacteria in addition. The difference between parallel plating on these media and on the high sugar medium thus yielded useful information about sources of casual contamination.
It is suggested that the above would also be largely applicable to other sugar-rich concentrates of not less than 50° Brix.
TL;DR: Mass lysis of lactic streptococci infected with baeteriophage at 30° was prevented at pH 5·10, while host cell properties were apparently unchanged by adsorption of phage particles in acid whey.
Abstract: SUMMARY: Mass lysis of lactic streptococci infected with baeteriophage at 30° was prevented at pH 5·10. At lower pH values no multiplication of phage followed infection, and prolonged incubation at 30° resulted in loss of phage particles from unlysed samples. Adsorption of phage particles on host cells was unaffected by acidity, but no phage penetration of host cells took place. Host cell properties were apparently unchanged by adsorption of phage particles in acid whey.
TL;DR: In this paper, composite morning milk samples were taken once weekly for 9 weeks from 24 dairy farms and 208 samples were tested, and coagulase positive staphylococci (aureus, albus and citreus) were isolated from 127 (61%).
Abstract: SUMMARY: Composite morning milk samples were taken once weekly for 9 weeks from 24 dairy farms. In all 208 samples were tested, and coagulase positive staphylococci (aureus, albus and citreus) were isolated from 127 (61%). The week by week recovery of these staphylococci from individual farm samples varied between 11% and 88% Penicillin resistant coagulase positive strains were recovered from 20 samples (10%).
TL;DR: Sodium benzylpenicillin, contaminated with Bacillus subtilis spores by freeze-drying a suspension of spores in an aqueous penicillin solution, was exposed to gamma radiation and a 70-tube dilution method was used to determine the surviving spores after various doses.
Abstract: SUMMARY: Sodium benzylpenicillin, contaminated with Bacillus subtilis spores by freeze-drying a suspension of spores in an aqueous penicillin solution (c. 50% w/v), was exposed to gamma radiation and a 70-tube dilution method was used to determine the surviving spores after various doses. The correlation coefficient between log10 percentage survival and dose was −0.9523. The regression of the former on the latter was calculated and the decimal reduction dose found to be 20.2 × 104 rads. The regression and the decimal reduction dose were similar to those obtained when suspensions of spores in distilled water were irradiated.
TL;DR: The self-sterilizing activity was markedly diminished at 40% r.h. and the inclusion of blood in the deposited bacterial particle was then completely protective, so repeated washing in water with gentle rubbing quickly inactivated Cetavlon paint films.
Abstract: SUMMARY: A method is described for testing the self-sterilizing activity of surfaces coated with paints containing bactericidal agents. The most active coating consisted of 10% (w/w) Cetavlon dissolved directly in urea-formaldehyde:alkyd resin. The recovery of viable organisms from such surfaces infected with Streptococcus faecalis, Staphylococcus aureus, Aerobacter aerogenes and Chromobacterium prodigiosum was less than 10% of that from painted control surfaces after exposure for 1 hr at atmospheric relative humidity of 70% and temperature of 20°. Bacillus subtilis spores were not affected until they became heat-sensitive. The self-sterilizing activity was markedly diminished at 40% r.h. and the inclusion of blood in the deposited bacterial particle was then completely protective. Repeated washing in water with gentle rubbing quickly inactivated Cetavlon paint films.
TL;DR: Forty mould species, 30 of which were from the genera Aspergillus, Penicillium, Fusarium and Mucor, were examined for their ability to utilize the lactose in whey and to produce fat in the mycelium in stationary cultures, finding the most promising species were A. ustus, P. frequentans, and P. notatum.
Abstract: SUMMARY: Forty mould species, 30 of which were from the genera Aspergillus, Penicillium, Fusarium and Mucor, were examined for their ability to utilize the lactose in whey and to produce fat in the mycelium in stationary cultures.
In terms of lactose consumed and weight of mycelial felt produced the most promising species were A. ustus, P. frequentans, P. oxalicum and P. notatum. The first three of these warrant further study as fat producers.
TL;DR: The MSO test (3 days, 22°) was a more sensitive indicator of the presence of milk spoilage organisms than the coli-aerogenes test, and is recommended for routine use.
Abstract: SUMMARY: The results obtained during the examination of 2,310 advisory rinses of farm dairy equipment by means of colony count on Yeastrel milk agar at 30°, coli-aerogenes test at 30° and milk spoilage organisms (MSO) test at 22°, are discussed in relation to attainment of proposed satisfactory colony count levels. A much higher proportion of rinses of milking machine clusters gave unsatisfactory results than those of metal equipment. The MSO test (3 days, 22°) was a more sensitive indicator of the presence of milk spoilage organisms than the coli-aerogenes test, and is recommended for routine use. Results for milking machine clusters sterilized with steam were much better than those for clusters claimed to have been cleansed by chemical methods.
TL;DR: Early gelling of a lightly phage-infected culture of lactic streptococci in milk gave protection against phage attack and depended on the formation of isolated foci of infection in the gel structure.
Abstract: SUMMARY: Early gelling of a lightly phage-infected culture of lactic streptococci in milk gave protection against phage attack. This protection was necessary only at acidities of less than 0·33% lactic acid (pH 5·36) and depended on the formation of isolated foci of infection in the gel structure.