Effect of Various Concentrations of Brilliant Green and Bile Salts on Salmonellae and Other Microorganisms

A study of the inhibitory effect of 24 different combinations of brilliant green and bile salts concentrations was conducted, using seven species of microorganisms capable of fermenting mannitol. The inhibitory effect of brilliant green decreased as the bile salts concentration was increased. Staphylococcus aureus and Proteus rettgeri were inhibited by all test media. Escherichia coli was inhibited in all but two combinations of brilliant green and bile salts. Aerobacter aerogenes generally followed a pattern of growth similar to that of three species of salmonellae. Three of the 24 combinations of brilliant green and bile salts showed little or no inhibition of salmonellae but did inhibit the other organisms studied.     

Variation in Plating Efficiency of Salmonellae on Eight Lots of Brilliant Green Agar

The plating efficiency of Salmonella anatum, S. cubana, S. dublin, S. tennessee, and S. typhimurium was determined for eight lots of Brilliant Green Agar made by two manufacturers. Washed cells were used as the inoculum and cultures were incubated at 41.5 C. All lots of Brilliant Green Agar were supplemented with 12 mg of sulfadiazine per 100 ml of medium. Of the eight lots of Brilliant Green Agar tested, average recovery of the test salmonellae in three did not differ from recoveries with Trypticase Soy Agar, which was used as a control to indicate the number of viable salmonellae in the test suspension capable of growth on a nonselective medium. Two lots of Brilliant Green Agar gave salmonellae recoveries with geometric means about 25% lower than, and significantly different from, those of the control agar. The remaining three lots of Brilliant Green Agar were generally unproductive.     

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.     

Comparison of Brilliant Green Agar and Hektoen Enteric Agar Media in the Isolation of Salmonellae from Food Products

Brilliant Green (BG) agar and Hektoen enteric (HE) agar media were compared for their efficiency in isolating salmonellae from various food products. Of the 11,226 food specimens examined, 1,662 (or 14.9%) yielded salmonellae. Of this number, 1,475 (88.7%) were recovered from BG agar and 1,315 (79.1%) were recovered from HE agar media. The results indicate that BG agar is more effective in isolating salmonellae from food products. A smaller subsidiary study showed HE agar to be more selective than BG agar. Four hundred ten specimens yielded 92 nonlactose-fermenting isolants other than salmonellae on BG agar and only 11 such isolants on HE agar.     

Effect of Heat on the Antimicrobial Activity of Brilliant Green Dye

Antimicrobial activity of brilliant green dye in Trypticase soy broth (BBL) is reduced and ultimately destroyed by prolonged autoclaving at 121 C. Loss of antimicrobial activity is accompanied by decolorization of the dye. This is consistent with other evidence that antimicrobial activity of brilliant green resides in the colored dye ion. The dye is not decolorized when heated in distilled water or peptone, but is decolorized by heating in glucose, glycine, or sodium dodecyl sulfate, showing that decolorization results from reaction with components of the medium. To ensure optimal results, it is recommended that bacteriological media be sterilized by heat prior to addition of brilliant green dye.     

Factors Affecting Selectivity of Brilliant Green-Phenol Red Agar for Salmonellae

Commercial brilliant green (BG)-sulfa agar was found to be nonselective toward a test series of Enterobacteriaceae. Various formulations of BG were prepared by using Trypticase soy agar (BBL) as a base. Results were more reproducible when BG dye was added after sterilization than before. Sulfonamides improved selectivity as compared with brilliant green alone. Sulfanilamide (SN) was slightly more selective for salmonellae than other sulfonamides tested. Bile salts and sodium dodecyl sulfate markedly reduced the toxicity of BG to all the test bacteria. Enterobacter strains were most difficult to inhibit. A combination of 5 mg of BG and 1 g of SN/liter prevented growth of Proteus mirabilis and Escherichia coli and retarded growth of Enterobacter strains. The BG-SN agars were superior in selectivity to a series of commercial agars tested, and numbers of salmonellae recovered on BG-SN agar and Trypticase soy agar (BBL) were the same. Brilliant green agars with various degrees of selectivity are described.     

Susceptibility of Salmonellae to Cephalosporins and to Nine Other Antimicrobial Agents

Three cephalosporin-related antibiotics and nine other antimicrobial agents were studied for in vitro effectiveness against 54 recently isolated strains of Salmonella. Minimal inhibitory concentrations determined by the plate dilution method demonstrated the following percentages of resistance: ampicillin, 6%; tetracycline, 13%; streptomycin, 52%; sulfadiazine, 94%; cephaloglycin, 96%; and lincomycin, 100%. No strains were resistant to cephalothin, cephaloridine, chloramphenicol, colistimethate, kanamycin, and polymyxin B. The commonest serotype studied, S. typhimurium, showed the greatest antibiotic resistance, with 21% resistant to ampicillin, 36% resistant to tetracycline, and 71% resistant to streptomycin. Cephalothin and cephaloridine were highly effective in vitro but inhibitory concentrations of 20 to 40 mug of cephaloglycin per ml were required for the majority of Salmonella strains.     

Viability of Selected Microorganisms in Hydrocarbon Fuels

A laboratory study of the viability of selected microorganisms in a hydrocarbon fuel medium was carried out on 19 species of microorganisms, representative of the types found as natural contaminants in aircraft fuels. More species remained viable when inoculated in pure cultures than when inoculated in mixed (composite) cultures. Of the 19 species selected, 10 were still viable after 3 months and 5 were viable after 4 months in the pure culture inoculants. In the complete composite culture inoculant, the bacterial species which were viable at the end of 4 months were the same as those found in the pure culture inoculant. No fungi remained viable in the complete composite cultures after a 3-week period. The microorganisms which remain viable in a hydrocarbon fuel medium are considered indicative of a satisfactory inoculum to be used as a test culture in laboratory analysis of mechanical control techniques.     

Observation of Microorganisms in Soil and Other Natural Habitats

A procedure is described for visually observing and following the activities and interactions of bacteria, actinomyctes, fungi, protozoa, nematodes, and plant roots in masses of soil. Specific microscope components and objectives are used, and the numerical apertures are adjusted such that light diffraction colors are produced to allow differentiation of the various biological entities and their habitat materials. Strains or other alterations in the organisms and their habitat are not employed, and time-lapse photography can be used to follow the activities of soil microorganisms and plant roots. As a result of the use of this technique, it is apparent that in situ indigenous soil microorganisms differ from similar organisms grown in the laboratory, but that, under the proper conditions, the state of the organism in either habitat can be altered to match that which occurs in the contrasting habitat.     

The Effect of Sugars and Polyols on the Heat Resistance of Salmonellae

S ummary . The heat resistance at 65° of 3 strains of salmonellae in solutions of sugars or polyols was enhanced as the concentration of the solutes increased. There was no linear relationship between heat resistance and water activity ( a_w ), but for all solutes except glycerol there was a linear relationship between log D ₆₅ and concentration (% w/w) of solute. Comparison of D ₆₅ at a particular a_w or percentage (w/w) solute concentration showed that the value decreased in the order: sucrose > glucose > sorbitol > fructose > glycerol. In glycerol, D ₆₅ values were always very much lower than in any other solute. With sucrose–glycerol or sucrose–glucose mixtures, heat resistance depended both on the total concentration (% w/w) of solutes present and also on the a_w of the solution.     

Differential Dynamic Microscopy: A High-Throughput Method for Characterizing the Motility of Microorganisms

We present a fast, high-throughput method for characterizing the motility of microorganisms in three dimensions based on standard imaging microscopy. Instead of tracking individual cells, we analyze the spatiotemporal fluctuations of the intensity in the sample from time-lapse images and obtain the intermediate scattering function of the system. We demonstrate our method on two different types of microorganisms: the bacterium Escherichia coli (both smooth swimming and wild type) and the biflagellate alga Chlamydomonas reinhardtii. We validate the methodology using computer simulations and particle tracking. From the intermediate scattering function, we are able to extract the swimming speed distribution, fraction of motile cells, and diffusivity for E. coli, and the swimming speed distribution, and amplitude and frequency of the oscillatory dynamics for C. reinhardtii. In both cases, the motility parameters were averaged over ∼ 10⁴ cells and obtained in a few minutes.     

Neutralization of the Bactericidal Effect of Cocoa Powder on Salmonellae by Casein

Four pre-enrichment media (nutrient broth, lactose broth, reconstituted non-fat dry milk and nutrient broth containing 5% (w/v) casein) were evaluated for the recovery of salmonellae from cocoa powder. Addition of 5% cocoa powder to nutrient broth and to lactose broth proved to be bactericidal to salmonellae. Heat-damaged Salmonella typhimurium were more sensitive than undamaged cells to cocoa powder and agitation increased the bactericidal effect. The bactericidal effects were minimized in pre-enrichment media that contained either 5% casein or nonfat dry milk.     

Effect of Viscosity on Bacterial Motility

The behavior of a number of motile flagellated bacteria toward viscosity characteristics of their fluid environments was observed. All showed an increase in velocity (micrometers per second) in more viscous solutions. Velocity reached a maximum at a characteristic value, however, and thereafter decreased with higher viscosities. Peritrichously flagellated bacteria had maximum velocities at higher viscosities than polarly flagellated bacteria. Effects of temperature, and possible utilization of chemical constituents in the viscous solutions, were studied and found to be negligible factors under the experimental conditions used. Different agents produced the same phenomenon, thus indicating that there probably were no chemically induced metabolic effects. Loss of available water and the possibility of a variable energy supply to the flagellar propulsive system were considered but are believed minimal. Theoretically derived thermodynamic equations were utilized and suggest that the conformation of the flagellar helix affects efficiency of propulsion. Such a relationship between helix waveform and velocity was experimentally observed with Thiospirillum jenese.     

Lipid Patterns of Selected Microorganisms as Determined by Gas-Liquid Chromatography

The cellular lipid patterns of seven strains of microorganisms were examined by gas-liquid chromatography in this preliminary study. The chloroform methanol-soluble lipids were extracted by the Soxhlet method from dried cultures which had been grown at 25 +/- 2 C for 18 hr with mechanical shaking. The cellular extract was methylated by use of a low temperature sulfuric acid method, and the resulting methyl esters were chromatographed. Considerable differences in the lipid patterns among the seven microorganisms tested indicated that this method might be useful for the identification of closely related microbial genera, and possibly for species differentiation.     

金属催化剂有效快速裂解SARS冠状病毒和其他微生物

目的研究两种金属催化剂Ag/Al2O3和Cu/Al2O3对SARS冠状病毒和其他呼吸道疾病传播的阻断作用。方法100μL 106TCID50/mL SARS-CoV,100μL 106PFU/mL。表达重组仓鼠朊蛋白的杆状病毒和106大肠杆菌分别缓慢地滴加至两种圆形金属催化剂的表面,吸附5~20 min。使用不同培养液洗涤金属催化剂表面,检测洗涤物的病毒感染性和细菌的增殖。结果病毒和细菌分别吸附5和20 min后,SARS-CoV和杆状病毒的病毒滴度下降到非常低的水平,甚至难以检测到;大肠杆菌组经培养后无克隆生长。5 min吸附后,杆状病毒表达的重组PrP的表达下降到21.8%;20 min吸附后,没有PrP的表达。电镜检测发现大肠杆菌的细胞壁崩解,细胞破碎。结论与金属催化剂Ag/Al2O3和Cu/Al2O3表面接触后,破坏了SARS-CoV,杆状病毒和大肠杆菌的复制增殖能力。两种金属催化剂利用空气中的氧分子有效的杀灭吸附于其表面的病毒和细菌,有希望用来作为医院、家庭和公共场所的空气消毒。     

Effect of Light on Nonphotosynthetic Microorganisms

The effect of light on the pigmentation of various strains belonging to the genus Streptomyces was investigated. It was revealed that six species of streptomycetes, S. massasporeus, S. phaeopurpureus, S. chibaensis, S. salmonicida, S. fluvissimus and S. longispororuber, were photochromogenic, i.e., these strains can be photoinduced to synthesize pigments. On the basis of these results, pigmentation in Streptomyces is discussed.