agar and brilliant-green

Topics: Aeromonas; Agar; Bacteriological Techniques; Carbanilides; Coloring Agents; Diarrhea; Feces; Gram-Negative Bacterial Infections; Humans; Quaternary Ammonium Compounds

Mannitol lysine crystal violet brilliant green agar (MLCB) is widely used in Japan for Salmonella isolation because the medium has been commercially available. Colonies of Salmonella on MLCB appear colorless with black centers due to H2S gas production; however, most Citrobacter freundii also produce H2S gas. In order to distinguish H2S-positive Salmonella from C. freundii we have improved MLCB. To MLCB was added 1% lactose (L-MLCB). The relation for pH and black center colony formation was examined. The pH of MLCB and L-MLCB inoculated with Salmonella species was slightly acid after 7 h, but the pH of L-MLCB inoculated with C. freundii did not become acid for 24 h. The colony of C. freundii did not have a black center because the production of acid from lactose lowers the pH below 10 where it is needed for H2S to react with iron to produce black pigments. Of 99 Salmonella strains including 13 serotypes tested, all strains had the same colony morphologies on MLCB and L-MLCB. When MLCB and L-MLCB were evaluated with 36 C. freundii strains isolated from foods, only colonies on MLCB had black centers. We conclude that L-MLCB is useful for detection of nonlactose-fermenting, H2S-positive Salmonella in food samples.

Topics: Agar; Citrobacter freundii; Colony Count, Microbial; Coloring Agents; Culture Media; Gentian Violet; Hydrogen Sulfide; Hydrogen-Ion Concentration; Indicators and Reagents; Lactose; Lysine; Mannitol; Quaternary Ammonium Compounds; Salmonella; Time Factors

A novel agar medium, chromogenic Salmonella esterase (CSE) agar, for the differentiation of salmonellae is described. The agar contains peptones and nutrient extracts together with the following (grams per liter unless otherwise specified): 4-[2-(4-octanoyloxy-3, 5-dimethoxyphenyl)-vinyl]-quinolinium-1-(propan-3-yl carboxylic acid) bromide (SLPA-octanoate; bromide form), 0.3223; lactose, 14. 65; trisodium citrate dihydrate, 0.5; Tween 20, 3.0; ethyl 4-dimethylaminobenzoate, 0.035% (wt/vol), novobiocin, 70 mg liter-1. The key component of the medium is SLPA-octanoate, a newly synthesized ester formed from a C8 fatty acid and a phenolic chromophore. In CSE agar, the ester is hydrolyzed by Salmonella spp. to yield a brightly colored phenol which remains tightly bound within colonies. After 24 h of incubation at 37 or 42 degreesC, colonies of typical Salmonella spp. were burgundy colored on a transparent yellow background, whereas non-Salmonella spp. were white, cream, yellow or transparent. CSE agar was evaluated by using a panel of strains including a high proportion of Salmonella and non-Salmonella strains giving atypical reactions on other differential agars. The sensitivity (93.1%) of CSE agar for non-typhi salmonellae compared favorably with those of Rambach (82. 8%), xylose-lysine-deoxycholate (XLD; 91.4%), Hektoen-enteric (89.7%), and SM ID (91.4%) agars. The specificity (93.9%) was also comparable to those of other Salmonella media (SM ID agar, 95.9%; Rambach agar, 91.8%; XLD agar, 91.8%; Hektoen-enteric agar, 87.8%). Strains of Citrobacter freundii and Proteus spp. giving false-positive reactions with other media gave a negative color reaction on CSE agar. CSE agar enabled the detection of >30 Salmonella serotypes, including agona, anatum, enteritidis, hadar, heidelberg, infantis, montevideo, thompson, typhimurium, and virchow, which accounted for 91.8% of the salmonella isolates recorded by the Public Health Laboratory Service (Colindale, London, England) for 1997.

Topics: Agar; Bacteriological Techniques; Caprylates; Chromogenic Compounds; Culture Media; Enterobacteriaceae; Esterases; Esters; Evaluation Studies as Topic; Novobiocin; Quaternary Ammonium Compounds; Salmonella; Sensitivity and Specificity

A new medium, called novobiocin-brilliant green-glucose (NBG) agar, was developed for the isolation of Salmonella spp. and evaluated against other conventionally used media including bismuth sulfite, xylose-lysine decarboxylase, brilliant green-sulfa, hektoen enteric, and salmonella-shigella agars. NBG had recovery rates comparable to the other enteric media tested with pure cultures as well as with naturally contaminated amphibian and reptile waters and fecal specimens. However, NBG, hektoen enteric, and salmonella-shigella agars failed to differentiate Salmonella typhi from a fecal specimen even after enrichment in selenite F. Although Citrobacter freundii could grow and resembled salmonellae on NBG, at no time was the recovery of Salmonella spp. colonies jeopardized by the presence of C. freundii in either seeded or naturally contaminated samples. Confirmation rates of typical colonies from NBG agar also compared favorably to the other media tested; however, bismuth sulfite, although selective, was found to have varied differential characteristics for Salmonella spp. As a result, many more colonies had to be picked, which caused bismuth sulfite agar to have the lowest confirmation rate of the media tested. The distinct advantage that NBG agar offers over the conventional method tested, including bismuth sulfite, is the consistent differential reaction of all Salmonella subgroups including biochemically atypical strains. The medium is inexpensive, easy to prepare, and can be stored for at least 2 weeks at 4 degrees C without loss of selective or differential properties.

Topics: Agar; Animals; Culture Media; Feces; Glucose; Humans; Novobiocin; Quaternary Ammonium Compounds; Salmonella; Water Microbiology

Two solid selective media, xylose deoxycholate citrate agar (XDCA) and bile salts brilliant green agar (BBG) and an enrichment broth-alkaline peptone water, were evaluated for the isolation of Aeromonas hydrophila and Plesiomonas shigelloides. Alkaline peptone water and XDCA are useful for recovery of Aeromonas but not Plesiomonas, whereas BBG is satisfactory for both organisms.

Topics: Aeromonas; Agar; Bacteria; Bacteriological Techniques; Bile Acids and Salts; Citrates; Citric Acid; Culture Media; Deoxycholic Acid; Feces; Humans; Inositol; Peptones; Quaternary Ammonium Compounds; Vibrionaceae; Water; Xylose

Salmonellae in the environment remain a potential source of disease. Low numbers of salmonellae have been detected and enumerated from environmental samples by most-probable-number methods which require careful colony selection from a plated agar medium. A modified xylose lysine brilliant green medium was prepared to control the loss of selectivity caused by heating the brilliant green component. Added agar reduced colony spreading. The medium contained 47 g of xylose lysine agar base per liter; the agar content was adjusted to 2%, autoclaved, cooled to 50 degrees C, and then amended just before pouring to include H2S indicator and 7 ppm (7 ml of 1:1,000 brilliant green per liter) of unheated brilliant green dye. H2S-positive salmonellae were easily detected from sewage sludge compost to the exclusion of most other gram-negative bacteria. As a result, fewer non-salmonellae were picked for further most-probable-number analysis, greatly reducing the work load associated with the most-probable-number method. Direct plating was possible for enumerating salmonellae in laboratory composts containing ca. 10(3) or more salmonellae.

Topics: Agar; Bacteriological Techniques; Culture Media; Lysine; Quaternary Ammonium Compounds; Salmonella; Tetrathionic Acid; Xylose

Twenty duplicate cloacal swabs and the intestines of 98 broilers were cultured using Rappaport-Vassiliadis and tetrathionate as enrichment broths. These were plated to brilliant green and modified dulcitol brilliant green agars at one, two and seven days. Salmonellae were recovered with greater frequency from tetrathionate plated to modified dulcitol brilliant green than the other combinations.

Topics: Agar; Animals; Anti-Infective Agents, Local; Chickens; Culture Media; Galactitol; Intestines; Quaternary Ammonium Compounds; Salmonella; Species Specificity; Tetrathionic Acid

The development of Rappaport's enrichment medium and elevated temperature incubation as methods of salmonella isolation is traced. The recent recording of a merger of the two techniques by means of Rappaport--Vassiliadis medium is noted (RV medium). In Cardiff, we have found an earlier modification of Rappaport's enrichment (R25) by Vassiliadis to be efficient in salmonella recovery from environment samples. The current study compares the two media using sewage polluted natural water as test material. Under the conditions of experiment, R25 was more successful in salmonella isolation than RV, although the later medium inhibited competitive organisms better. R25 is a convenient enrichment broth for routine use. In combination with pre-enrichment it allows the use of a loop for subculture rather than a pipette. This increases safe manipulation. It also produces a high proportion of positive isolations at the 24 h subculture time in contrast to other enrichment broths. For these reasons it forms an integral part of salmonella isolation methodology in our laboratory.

Topics: Agar; Citrates; Citric Acid; Coloring Agents; Culture Media; Deoxycholic Acid; Quaternary Ammonium Compounds; Rosaniline Dyes; Salmonella; Sewage; Temperature; Water Microbiology; Water Pollution

Topics: Agar; Coloring Agents; Culture Media; Deoxycholic Acid; Food Microbiology; Quaternary Ammonium Compounds; Salmonella

Topics: Agar; Campylobacter fetus; Humans; Male; Penis; Quaternary Ammonium Compounds; Vibrio