Identification of 'Haemophilus somnus' by rapid tests for pre-formed enzymes

In rapid tests for pre-formed enzymes, all strains of ' Haemophilus somnus ' examined gave positive reactions for alkaline phosphatase, cytochrome oxidase, β-glucosidase, β-glucuronidase and hippurate hydrolase but were negative for α-mannosidase, β-galactosidase and β-xylosidase, tributyrin esterase, cystine aminopeptidase and γ-glutamyl aminopeptidase. The pattern of results differed from those given by Actinobacillus, Haemophilus, 'Histophilus', Pasteurella and Taylorella species.     

Development of an improved selective agar medium for isolation of Yersinia pestis

Existing media designed for selective isolation of clinically important members of the genus Yersinia were found to be unsatisfactory for the growth and isolation of Yersinia pestis. We report the development of a new selective agar medium (termed BIN) that supports the growth of Y. pestis. The development of the formulation of this medium was based on a fluorescence screening system designed for monitoring bacterial growth on semisolid media, using a green fluorescent protein-expressing strain. High-throughput combinatorial experiments can be conducted for the quantitative evaluation of the effect of different medium components on growth. Generation of fluorescence plots in this system, using microplates, allowed the quantitative evaluation of the growth rate of Y. pestis EV76 cultures in different agar compositions. The final BIN formulation is based on brain heart infusion agar, to which the selective agents irgasan, cholate salts, crystal violet, and nystatin were introduced. It was found that BIN agar is more efficient in supporting colony formation and recovery of Y. pestis than are the conventional semisolid media MacConkey agar and Yersinia-selective agar (cefsulodin-irgasan-novobiocin agar). The advantage of BIN over other media has been also demonstrated in recovering virulent Y. pestis from the mixed bacterial populations found in decaying carcasses of infected mice. The BIN medium is suggested as a selective medium for isolation and recovery of Y. pestis from various backgrounds.     

An improved medium for the isolation of Cryptococcus neoformans from pigeon droppings

Isolation of Cryptococcus neoformans is enhanced when methyl violet at 2 mg l-1 is added to the usual Guizotia abyssinica medium. In preliminary tests the medium has also proved useful for isolating C. neoformans from other sources.     

Development of an improved chemically defined minimal medium for Listeria monocytogenes.

A chemically defined minimal medium for Listeria monocytogenes has been developed by modification of Welshimer's medium. The growth factors required by L. monocytogenes Scott A are leucine, isoleucine, arginine, methionine, valine, cysteine (each at 100 mg/liter), riboflavin and biotin (each at 0.5 micrograms/ml), thiamine (1.0 micrograms/ml), and thioctic acid (0.005 micrograms/ml). Growth was stimulated by 20 micrograms of Fe3+ per ml as ferric citrate. Glucose (1%) and glutamine (600 mg/liter) are required as primary sources of carbon and nitrogen. Glucose could not be replaced by various organic acids or amino acids. Of several sugars tested, fructose, mannose, cellobiose, trehalose, maltose (weak), glycerol (weak), and the amino sugars glucosamine, N-acetylglucosamine, and N-acetylmuramic acid supported growth in the absence of glucose. Evidence was found that chitin and cell walls of starter bacteria (Lactococcus lactis) supported survival of L. monocytogenes, which suggests that the pathogen may obtain carbon and energy sources during colonization of some foods, such as cheeses, by assimilating bacteria or molds that are present.     

An improved selective isolation medium for the recovery of Listeria monocytogenes from smoked fish

AIMS: The aim of this study was to improve the selective isolation of Listeria monocytogenes from smoked haddock fillets. METHODS AND RESULTS: Listeria selective agar (LSA)--Oxford formulation was supplemented with 25 microg x ml(-1) of colistin sulphate and 30 microg x ml(-1) of nalidixic acid. Inocula from four smoked haddock fillets produced colonies (approx. 2-13 bacteria x g(-1)), identified as L. monocytogenes, on LSA supplemented with antimicrobial compounds (MLSA). Moreover, there was only negligible evidence of bacteria which were not L. monocytogenes on MLSA. In contrast, LSA supported dense bacterial growth, which was not equated with L. monocytogenes. SIGNIFICANCE AND IMPACT OF THE STUDY: The modified medium permitted the recovery of L. monocytogenes from smoked haddock fillets and reduced the growth of contaminating bacteria.     

Malachite green pre-enrichment medium for improved salmonella isolation from heavily contaminated samples

V an S chothorst , M. & R enaud , A. M. 1985. Malachite green pre-enrichment for improved salmonella isolation from heavily contaminated samples. Journal of Applied Bacteriology 59 , 223–230.
Large numbers of competitive bacteria may hinder the isolation of salmonellas from food and environmental samples when a pre-enrichment method is used. The addition of 0.1 g/1 of malachite green (MG) to buffered peptone water (BPW) inhibited the multiplication of Gram-positive bacteria. Brilliant green had a similar effect but only when the normal recommended concentration of 0.02 g/1 was raised to 0.05 g/1. Pure strains of salmonellas were inhibited by MG in BPW, but addition of non fat dried milk (NFDM) (5 g/1 or more) counteracted this effect. MG did not affect the recovery of salmonellas injured by heat, freezing, low water activity or acidity in BPW with NFDM. It was concluded that addition of MG to BPW may improve the possibility of isolating salmonellas from heavily contaminated materials by limiting the competitive growth of Gram-positive bacteria and the subsequent lowering of the pH of the broth.     

Malachite green pre-enrichment medium for improved salmonella isolation from heavily contaminated samples

Large numbers of competitive bacteria may hinder the isolation of salmonellas from food and environmental samples when a pre-enrichment method is used. The addition of 0.1 g/l of malachite green (MG) to buffered peptone water (BPW) inhibited the multiplication of Gram-positive bacteria. Brilliant green had a similar effect but only when the normal recommended concentration of 0.02 g/l was raised to 0.05 g/l. Pure strains of salmonellas were inhibited by MG in BPW, but addition of non fat dried milk (NFDM) (5 g/l or more) counteracted this effect. MG did not affect the recovery of salmonellas injured by heat, freezing, low water activity or acidity in BPW with NFDM. It was concluded that addition of MG to BPW may improve the possibility of isolating salmonellas from heavily contaminated materials by limiting the competitive growth of Gram-positive bacteria and the subsequent lowering of the pH of the broth.     

Development of novel Alicyclobacillus spp. isolation medium

AIM: To develop a new isolation medium with higher recovery rates of Alicyclobacillus spp. METHODS AND RESULTS: SK agar was developed with optimized incubation temperature, pH, acidulant, Tween 80 concentration and divalent cation addition. Results indicate that detection of Alicyclobacillus spp. by SK agar was significantly higher (P > 0.05) than those obtained by K agar, orange serum agar, and potato dextrose agar. CONCLUSIONS: Current media used for Alicyclobacillus spp. isolation still resulted in high numbers of false negative products. The sensitivity of SK agar to Alicyclobacillus spp. allows detection of low numbers of Alicyclobacillus spp. and also provides a more higher isolation results compared with currently used media. SIGNIFICANCE AND IMPACT OF THE STUDY: SK agar will be useful to the fruit juice industry to obtain more accurate numbers of contaminant Alicyclobacillus spp. With this media, false negative samples can be reduced, and the likelihood of exported products being rejected can be greatly reduced.     

An improved solid medium for isolation,enumeration and genetic investigations of autotrophic iron-and sulphur-oxidizing bacteria

An improved solid medium using Gelrite as a supporting gel for isolation and enumeration of acidophilic chemolithotrophic Thiobacillus strains was tested. Dark-brown circular colonies, which were robust and well-differentiated, developed on this medium within 72–96 h. The plating efficiency of T. ferrooxidans strains was 92.1±5.8%. Linear correlations with an optical density (OD) at 400 nm of 0.5, corresponding to 7·10⁶ and 5·10⁷ cells·ml^–1 for strains ATCC 13661 and TMB, respectively, were obtained. Linear correlations between OD, total bacterial protein, dry biomass and cell number were also determined. These data can be used for modelling and scale-up design of microbial leaching operations. With this plating technique, one prerequisite for selection of different mutants of T. ferrooxidans has been fulfilled. Correspondence to: A. M. Khalid     

Growth medium for Neisseria meningitidis isolation

Growth medium for isolation of N. meningitidis, which do not require addition of serum and based on previously developed medium for cultivation of bacteria from Haemophilus genus (without growth factors V and X) was constructed. Selective properties of the medium in relation to meningococci were determined by addition of vancomycin and colistin--antibacterial supplement inhibiting growth of nonpathogenic Neisseria and outside microflora. Developed medium was successfully approved during examination of children for nasopharyngeal carriage of meningococci.     

Nutrient medium for the isolation and cultivation of pneumococcus

A culture medium for the isolation and cultivation of pneumococci, produced in a solid or liquid form and based on raw material unsuitable for use as foodstuff (human placenta), has been developed. The amino acid composition of the medium has been studied. The medium has been found to contain 19 amino acids, to be free from ballast serum proteins and blood, and to ensure the good growth of pneumococci isolated from pathological material, the formation of the normal capsule, as well as active biological properties. The medium has proved to create elective and selective conditions enhancing the effectiveness of investigations and simplifying the isolation of pneumococci in the microbiological examination of patients.     

A medium for the selective isolation of Edwardsiella ictaluri

A selective medium, called Edwardsiella ictaluri medium (EIM), has been formulated for the isolation of Edwardsiella ictaluri. The medium inhibits the growth of most gram-negative bacteria, except Proteus sp., Serratia marcescens and some isolates of Aeromonas hydrophila and Yersinia ruckeri. The bacteria that grow on the EIM are easily differentiated from E. ictaluri based on colony morphology. The EIM inhibits gram-positive bacteria with the exception of enterococci. The addition of fungizone to EIM suppressed the growth of most fungi. The EIM allows the evaluation of environmental reservoirs, levels of contamination and carrier states of E. ictaluri.     

Selective nutrient medium for the isolation of Bacillus cereus

A selective dried medium for the isolation of B. cereus from clinical material and foodstuffs has been developed. The medium has high selective properties which ensure the isolation of B. cereus from microbial association in pure culture, thus making it possible to accelerate further identification of the microorganisms.     

A selective medium for the isolation of wood-rotting basidiomycetes

A selective medium for growing wood-rotting basidiomycetes is described. The medium is based on a mixture of benomyl and 2-phenylphenol which suppresses the growth of lower fungi and Sistotrema brinkmannii, a basidiomycete of frequent occurrence in timber but one which cannot decay wood. Use of the medium in isolation studies permits a higher recovery of wood-rotting basidiomycete fungi than can be achieved by the use of other selective media.