Evaluation of Culture Media for the Isolation of Salmonellae from Feces

Serial passage of the 64-2389 strain of type 3 parainfluenza virus in cercopithecus monkey kidney tissue cultures at low temperatures resulted in the selection of a variant which had a higher efficiency of plaque formation at 25 C than the parent line grown at 37 C. The cold variant, unlike the parent strain, plaqued readily at 25 C, and at 37 C it produced significantly larger plaques. Virus titers of the cold variant in hamster lungs were significantly lower and this was probably caused by the stimulation of interferon by the cold variant during the early phase of the infection. The cold variant, like the virus grown at 37 C, also induced the synthesis of interferon late in the infection. Hamsters responded to the intranasal inoculation of each virus line by the development of hemagglutinating-inhibiting antibodies in the sera.     

Evaluation of Three Media for Selective Isolation of Gram-Positive Bacteria from Burn Wounds

Three media, phenylethyl alcohol blood agar, esculin-mannitol agar, and Columbia CN blood agar, were studied for the selective isolation of gram-positive bacteria from swab cultures of burn wounds.     

Evaluation of Culture Media for the Isolation of Salmonellas from Sewage Sludge

Ten samples of sewage sludge were examined by various methods for the isolation of salmonellas using three types of enrichment broth: Muller-Kauffmann Tetrathionate Broth (MKTB), Selenite F Broth (SFB), and Brilliant Green Broth (BGB), two temperatures (37°C and 43°C) and three selective media: Deoxycholate Citrate Agar incubated aerobically (DCA), and anaerobically (DCA(N)), Brilliant Green Agar (BGA), and Bismuth Sulphite Agar (BSA). The results suggest that a combination of pre-enriched MKTB incubated at 37°C and plated on to BGA at 24 and 48 h was the best method, but when examining contaminated material such as sewage sludge, it appears unwise to rely on one single method.     

Comparison of Selective Media for Isolation of Presumptive Group D Streptococci from Human Feces

Pfizer Selective Enterococcus (PSE) agar, a medium containing bile, sodium azide, and esculin, was evaluated for its sensitivity and selectivity for detection and enumeration of presumptive group D streptococci in human feces. SF broth and SF broth plus agar (1.5%), representing selective media in common use, were studied simultaneously. Presumptive group D streptococci were recovered on PSE agar from the feces of all 25 subjects. No growth was observed in 8% of specimens in SF broth. No gram-negative organisms were recovered in any medium. PSE agar has the advantages of selecting out Streptococcus bovis, earlier appearance of distinctive reactions, and lack of requirement for special incubation temperature.     

Comparative Studies on Enrichment And Selective Media for Isolation of Salmonellae from Faecal Specimens

Enrichment media (tetrathionate, selenite and Rapp ap ort broths) and selective media (desoxycholate citrate agar and brilliant green agar) were tested in different combinations to ascertain their capacity for isolation of salmonella bacteria. The material consisted of 299 samples of cattle faeces from two herds infected with salmonella (Table 1), and of 111 artificially contaminated samples of pig faeces (Table 3). The tetrathionate and selenite broths were equally useful for the material as a whole, whereas the results varied between different species of salmonella which is of great practical interest. The number of salmonella isolations was much lower when enrichment with Rappaport broth was used. The rate of salmonella isolations can often be increased by parallel enrichments with two different media. Of the selective agar media tested, brilliant green agar was superior to desoxycholate citrate agar.     

A Comparison of Various Selective Media, including a New Selective Medium for the Isolation of Brucellae from Milk

S ummary : A comparative trial of a new medium for brucella was made on samples of milk from individual cows and herd samples of milk. The new medium gave a higher isolation rate than any of the other 3 selective media tested. There was no evidence that the new medium inhibited any of the biotypes of Brucella abortus , especially biotype 2; it was the only medium suitable for isolating from samples of herd milk strains of biotype 2 which are sensitive to antibiotics and aniline dyes.     

Performance of Selective and Differential Media in the Primary Isolation of Yeasts from Different Biological Samples

In view of the increase in yeast infections, especially polymicrobial ones, differential culture media have acquired increasing importance. The present study evaluated the Sabouraud chloramphenicol, Biggy agar, Pagano Levin agar and CHROMagar Candida media in terms of isolation, number of yeast colony forming units per plate, and inhibition of bacteria and filamentous fungi. To this end, we used 223 biological samples, including feces, and oral, vaginal and anal mucosae from 86 patients presenting or not symptoms of fungal infections. The four media did not differ significantly in terms of detection of yeast-positive cultures. The number of colony forming units per plate ranged from zero to 2.380, with a predominance of counts of 1 to 9 colonies per plate. No significant differences were observed among the four culture media in terms of number of colonies counted, for each kind of biological material. Fifteen species belonging to the genera Candida, Saccharomyces, Cryptococcus, Trichosporon and Rhodotorula were isolated, with C. albicans being the predominant species, followed by C. parapsilosis and R. rubra. CHROMagar Candida and Biggy agar were complementary in the isolation of the different species and favored a greater recovery of polymicrobial cultures. Pagano Levin agar isolated the smallest variety of species. Sabouraud chloramphenicol agar was the least effective in terms of bacterial inhibition and favored a greater development of filamentous fungi. The results suggest that more than one culture medium should be used for an adequate primary isolation.     

Isolation of Pure Cultures of Algae from Contaminated Cultures

Algal cultures have been freed of bacterial contamination by a procedure involving treatment with a detergent and phenol, followed by plating on an agar medium for selection of pure cultures.     

Comparison of Two Plating Media for the Isolation of Erysipelothrix rhusiopathiae from Enrichment Broth Culture

Sodium azide-crystal violet-agar and a modified blood-azide (MBA)-agar were used to isolate Erysipelothrix rhusiopathiae from swine tissues. There was no significant difference in the number of isolations. However, 78% of the isolants from modified blood-azide medium required only 24 hr of incubation, whereas all of the isolants obtained on sodium azide-crystal violet medium required 48 hr.     

Evaluation of Media for Selective Isolation of Yeasts from Oral, Rectal, and Burn Wound Specimens

Six media were evaluated to determine their ability to isolate yeasts and inhibit bacteria. The media included the following: Snyder, Snyder tellurite, Sabouraud tellurite, Littman-gentamicin, molybdate, and Mycosel (BBL). Doses of mixed intestinal gram-negative bacilli and enterococci were most effectively inhibited by Snyder tellurite agar. Klebsiella pneumoniae was the most common bacterial contaminant of the other media. All six media were comparable in isolating yeasts while preventing the growth of the oral bacterial flora. The selection of a basal fungal growth medium for tellurite incorporation to inhibit bacteria but permit growth of yeasts was affected by pH. The bacteriostatic effect of tellurite was decreased with increasing pH of media while fungistatic action was increased. The arbitrary selection of Snyder and Littman agars to isolate yeast from burn wound cultures demonstrated the need to include a selective medium for these specimens. Blood, phenylethyl alcohol blood agar, and Columbia CN blood agar were all inadequate for isolating yeasts from burns. Growth of a variety of filamentous saprophytic and pathogenic dimorphic fungi grew adequately on four of five selective media tested.     

Baird-Parker Medium Supplemented with Acriflavine, Polymyxins and Sulphonamide for the Selective Isolation of Staphylococcus aureus from Heavily Contaminated Materials

Acriflavine was found to be less inhibitory to Staphylococcus aureus than to other staphylococci. Advantage was taken of this selective effect and of the synergistic action of polymyxins and sulphonamides on Proteus strains to improve the selective capacity of Baird-Parker's Staph. aureus isolation medium. A supplement mixture containing acriflavine, sodium sulphamezathine and low levels of polymyxin in addition to the usual egg yolk and potassium tellurite is proposed for use with this medium.     

Isolation of Salmonellae by Selective Motility Systems

Salmonellae were isolated from naturally infected swine and human feces by means of selective migration through semisolid enrichment (SM) media in modified “U” tubes. Comparative studies showed that recovery of Salmonella by SM techniques was equal or superior to that of standard procedures employed in two routine diagnostic laboratories. Primary Salmonella isolations from SM enrichment were relatively free from normal fecal bacteria and often pure. The SM method required only 15% of the media and correspondingly less time and skill than the usual methods for isolating Salmonella.     

Isolation and Characterization of Four Gram-Positive Nickel-Tolerant Microorganisms from Contaminated Sediments

Microbial communities from riparian sediments contaminated with high levels of Ni and U were examined for metal-tolerant microorganisms. Isolation of four aerobic Ni-tolerant, Gram-positive heterotrophic bacteria indicated selection pressure from Ni. These isolates were identified as Arthrobacter oxydans NR-1, Streptomyces galbus NR-2, Streptomyces aureofaciens NR-3, and Kitasatospora cystarginea NR-4 based on partial 16S rDNA sequences. A functional gene microarray containing gene probes for functions associated with biogeochemical cycling, metal homeostasis, and organic contaminant degradation showed little overlap among the four isolates. Fifteen of the genes were detected in all four isolates with only two of these related to metal resistance, specifically to tellurium. Each of the four isolates also displayed resistance to at least one of six antibiotics tested, with resistance to kanamycin, gentamycin, and ciprofloxacin observed in at least two of the isolates. Further characterization of S. aureofaciens NR-3 and K. cystarginea NR-4 demonstrated that both isolates expressed Ni tolerance constitutively. In addition, both were able to grow in higher concentrations of Ni at pH 6 as compared with pH 7 (42.6 and 8.5 mM Ni at pH 6 and 7, respectively). Tolerance to Cd, Co, and Zn was also examined in these two isolates; a similar pH-dependent metal tolerance was observed when grown with Co and Zn. Neither isolate was tolerant to Cd. These findings suggest that Ni is exerting a selection pressure at this site for metal-resistant actinomycetes.     

Comparison of Several Selective Media for Isolation and Differentiation of Coagulase-Positive Strains of Staphylococcus aureus

Six coagulase-positive strains of Staphylococcus aureus which had been cultivated in Brain Heart Infusion broth, milk, and brine were plated on seven isolation media. A significant difference in the growth patterns of the individual strains was found as well as a significant effect resulting from the previous cultivation history before plating. Brine and, to a lesser extent, milk were found to reduce maximal cell concentrations attained, but strains grown in brine and milk showed greater ability to withstand the selective action of the isolation media. Fibrinogen applied to the surface of five of the media allowed the formation of characteristic halos by coagulase-positive strains of S. aureus. Only half of the strains studied produced a zone of precipitation on SM110-Egg Yolk agar. The isolation medium containing cycloheximide and a high level of polymxin B was most inhibitory to the organisms.     

Bioremediation of Heavy Metals in Liquid Media Through Fungi Isolated from Contaminated Sources

Wastewater particularly from electroplating, paint, leather, metal and tanning industries contain enormous amount of heavy metals. Microorganisms including fungi have been reported to exclude heavy metals from wastewater through bioaccumulation and biosorption at low cost and in eco-friendly way. An attempt was, therefore, made to isolate fungi from sites contaminated with heavy metals for higher tolerance and removal of heavy metals from wastewater. Seventy-six fungal isolates tolerant to heavy metals like Pb, Cd, Cr and Ni were isolated from sewage, sludge and industrial effluents containing heavy metals. Four fungi (Phanerochaete chrysosporium, Aspegillus awamori, Aspergillus flavus, Trichoderma viride) also were included in this study. The majority of the fungal isolates were able to tolerate up to 400 ppm concentration of Pb, Cd, Cr and Ni. The most heavy metal tolerant fungi were studied for removal of heavy metals from liquid media at 50 ppm concentration. Results indicated removal of substantial amount of heavy metals by some of the fungi. With respect to Pb, Cd, Cr and Ni, maximum uptake of 59.67, 16.25, 0.55, and 0.55 mg/g was observed by fungi Pb3 (Aspergillus terreus), Trichoderma viride, Cr8 (Trichoderma longibrachiatum), and isolate Ni27 (A. niger) respectively. This indicated the potential of these fungi as biosorbent for removal of heavy metals from wastewater and industrial effluents containing higher concentration of heavy metals.     

Isolation of Myelin Basic Protein from Whole Tissue Extracts by Selective pH-Dependent Solubilization

ABSTRACT

A previous study¹ of the selective solubility of myelin basic protein (MBP) of tissue extracts at pH 9.0 has raised issues of its quantitative recovery, and the differential solubility of its charge isomers. The pH-dependent solubility of proteins of acid extracts of delipidated tissue of bovine spinal cord was therefore reexamined. MBP of whole extracts was completely soluble up to pH 8.0 only, and less so by 25 % at pH 9.0, and 43 % at pH 10.0. The proteins other than MBP were virtually insoluble between pH 5.0 to 6.0, and 9.0 to 10.0. The solubility of the main charge isomers I to III of MBP of 18.5 kDa was found not to be affected by pH. Either pH 5.0 or 9.0 is therefore suitable for the selective isolation of MBP from whole tissue extracts, only pH 5.0 providing for the complete recovery of MBP. The pH-dependent solution behaviour was also examined following the separation of proteins of whole extracts by anion exchange chromatogra phy at pH 10.4. Purified MBP and several related minor cationic components of lower molecular weight were soluble throughout. In contrast, the anionic proteins were only partly soluble between pH 4.0 to 10.0, i.e. by 4 to 20%. The results are consistent with specific protein-protein interactions of the proteins of whole extracts, either enhancing the solubility of non-MBP proteins, e.g. at pH 7.0, or impairing that of MBP between pH 8.0 to 10.0.     

Stimulation of Bacteriocin Production by Dialyzed Culture Media from Different Lactic Acid Bacteria

The cross-effects of dialyzed postincubates (with a cut-off at 1000 Da) on the biomass and bacteriocin production of six strains of lactic acid bacteria were studied, and a predominance of stimulating responses was found, the characteristics of which suggested merely nutritional effects or the presence of precursor fragments of the bacteriocins. Additionally, cluster analysis of the detected responses provides an approach to define groups of highly compatible (potential consortia) or doubtfully compatible strains of lactic acid bacteria. Such a definition, which does not claim taxonomic value, has practical interest, however, in cases (e.g., silage production) in which it is convenient to use mixed inocula including strains able to establish positive interactions.