摘要:

To facilitate monitoring of culture media, a simple quantitative streaking technique, implying ever‐decreasing numbers of colony‐forming units per surface area, as in spiral plating, was developed. The procedure evaluates, in quantitative terms, the ability of media (1) to support the formation of colonies by organisms that it was designed to grow and (2) to resist colonization by organisms that it is expected to suppress. The procedure was therefore termedecometricevaluation. The ecometric results appeared to agree well with observations made on productivity and selectivity of the media studied during routine examination of specimens.These encouraging results prompted further, rigorous standardization of ecometry. A template was developed to standardize inoculation and the depth of the agar was controlled to within ± 10%. Finally the attributes of the inocula used were accurately defined.The standardized ecometric technique has been found useful for the following purposes: (1) to assess the practical significance of the inhibitory effect of gentamicin observed in some moulds and yeasts (this was solved by replacing poorer basal media by one particular richer modification, viz. yeast morphology agar); (2) the development of a blood‐free selective enumeration medium forCampylobacter jejuni, i.e. sulphide iron motility agar plus the combination of antibiotics suggested by Skirrow (1977); and (3) verification of the absence of antimicrobial activity of enzyme preparations, e.g. catalase, used in culture media to remedy sublethal damage in certain groups of bacteria.Ecometric evaluation can now be recommended for (1) routine monitoring of consignments of dehydrated or ready‐to‐use, purchased media; and (2) in‐house checking of the functioning of medium preparation departments. Only occasionally is it necessary to use conventional counting techniques to confirm

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02623.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A quick and cheap method for selecting appropriate solid culture media has been devised. It consists in the rapid picking of fragments of test colonies with the aid of a rubber strip in which pins are fixed in parallel, dispensing up to 8 colonies simultaneously in the wells of a Microtiter plate and streaking 4 strains at the same time on square Petri dishes containing the media under comparison. The approximate diameters of well‐isolated colonies are measured with the aid of a series of calibrated spots. The results corresponded with those given by the spiral plate method used as a reference for colony count and diameter measur

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02624.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Pectins appear to be the main factors in tomato juice which are associated with the protection ofLactobacillus fermentumagainst destruction or injury by heat. Hydrolysis of pectins by enzymic action makes the cells more vulnerable to heat.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02625.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Studies were made of the prediction of intracellular water activity (aw) of microorganisms grown at reducedaw. These included the determination and prediction ofawof potassium L‐glutamate solutions and the prediction ofawin mixed solutions of various compatible solutes and macromolecules. Compatible solutes studied were L‐proline, glycerol, potassium chloride and D‐arabitol. The results indicate thatawpredictions of such mixtures may be done with acceptable accuracy by neglecting solute‐solute inter

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02626.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The antibacterial action of some polyhexamethylene biguanides uponEscherichia colihas been investigated. An amine ended dimer (AED) (n= 2), a polydisperse mixture sold by I.C.I. Limited as the active ingredient of Vantocil IB (PHMB,n= 5.5) and a high molecular weight (HMW) fraction (n≤ 10) of PHMB were used. PHMB and the high molecular weight fraction totally inhibited growth and motility ofEsch. coliin liquid culture, whilst amine ended dimer never totally inhibited either function, irrespective of concentration. Growth inhibition and bacteriocidal activity increased with increasing levels of biocide‐polymerization. The three compounds, whilst being active over different concentration ranges, possessed similar concentration exponents and temperature coefficients. Cytoplasmic membrane damage and disruption of the cell envelope, indicated by loss from the cells of 260 nm absorbing materials, inorganic phosphate, and changes in permeability towards the dye 2‐p‐toluidinylnaphthylene‐6‐sulphonate, was observed at concentrations which were markedly bactericidal whilst bacteristatic concentrations caused only loss of potassium. Loss of cytoplasmic materials from treated cells in all instances followed first‐order kinetics. This indicated that irreversible damage was initiated and completed within a short time of contact between cells and biocide. Alteration of cytoplasmic membrane permeability towards various cations was assessed by measuring rates of lysis of sphaeroplasts in isotonic solutions of Na, Li and Cs acetate. For a given biocide concentration, the rates of lysis were inversely proportional to the hydrated ionic radii of the cation. This indicated that the damage to the cytoplasmic membrane was non‐specific and proportional to biocide concentration. Temperature coefficients (Q10) of approximately 2.0 for the loss of 260 nm absorbing material, inorganic phosphate and potassium from treated cell‐suspensions and bacteriocidal activity suggested that death of cells and cytoplasmic membrane damage are directly associated and are a direct result of biocide action, rather than mediated through the induction of

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02627.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Methods for partitioning planktonic algal and bacterial populations were examined. If samples were filtered under gravity through a 1 μm pore size Nuclepore polycarbonate membrane the algae were retained on the filter and most (usually>80%) of the bacteria were found in the filtrate. The application of any vacuum or pressure during this process resulted in the appearance of chlorophyll in the filtrate. In radiotracer experiments this would lead to an overestimate of14C incorporation into the bacteria. There was excellent agreement between measurements of partition efficiency by epifluorescence direct counts of bacteria and by uptake of trace quantities of tritiated glucose. The methods were applied to the measurement of algal excretion of dissolved organic matter and its uptake by bacteria over light‐dark cycles. An illuminated water bath was adapted to provide shortened (3–24 h) light‐dark cycles which could be used to examine interactions between individual algal and bacterial species. Estimates of bacterial heterotrophic production based on the assimilation of labelled algal extracellular products were lower than those calculated from the incorporation of

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02628.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Variations in the numbers of total colonies ofKlebsiella pneumoniae, Acinetobacterspp. and pseudomonads were investigated in process waters of a paper mill in southern Finland. Variations were related to independent parameters, namely temperature, pH, redox potential and production of offset paper, by using multiple regression analysis. Temperature was the most significant regressor variable and was negatively correlated with bacterial counts. It accounted for up to about 80% of the variance in bacterial counts in various parts of the process. The significance of temperature was due to its fluctuations in a critical range, above and below the maxima for bacterial growth. The pH level was also significant for total colony count and forK. pneumoniae.Redox potential and the production of offset paper were of significance forAcinetobacterspp. Washing the paper machine with water and lye decreased the numbers of bacteria in process waters.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02629.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Of 36 strains of the ‘aizawai’ variety ofBacillus thuringiensis(H‐serotype 7) 16 were naturally associated with bacteriophages, 11 of which were isolated at titres of 106plaque‐forming units/ml and above. These 11 phages had varied host ranges amongBacillus cereusand five strains of the ‘aizawai’ variety ofB. thuringiensis.Host range, plaque morphology and differences in cold lability indicated dissimilarities between the phages, which could be used taxonomically to differentiate between strains of th

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02630.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The survival curves of cutaneous micro‐organisms in the presence of benzoyl peroxide were investigated. All the curves exhibited a shoulder prior to exponential cell death. Benzoyl peroxide was lethal to the cutaneous organisms tested and they varied in sensitivity increasing as follows:Propionibacterium acnes, Staphylococcus capitis, Staph. epidermidis, Staph. hominis, Prop, avidum, Prop. granulosum and Pityrosporum oval

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02631.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The minimum inhibitory concentration of sorbic acid has been determined forBacillus subtilis, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureusandCandida albicans.The inhibition was shown to be due to both undissociated and dissociated acid, and the effect of each has been calculated in accordance with a proposed mathematical model. Although the inhibitory action of undissociated acid was 10–600 times greater than that of dissociated acid, the latter caused more than 50% of the growth inhibition at pH levels above 6 for most of the organisms teste

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb02632.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY