Showing papers in "Applied and Environmental Microbiology in 1973"
TL;DR: A method for improving the original Galton microtechnique for detecting leptospiral antibodies has been developed and it is indicated that agreement between the original MA test and this new method exceeded 94%, whereas the originalGaltonmicrotechnique and the originalMA test agreed in a maximum of 77% of the tests.
Abstract: A method for improving the original Galton microtechnique for detecting leptospiral antibodies has been developed. Simultaneous titrations were performed on 281 animal and human sera and 17 hyperimmune sera with the microscopic agglutination (MA) test and the improved microtechnique. Reproducibility of the improved microtechnique was determined independently on 65 animal sera by two laboratory sections. The results obtained by comparing positive test data from human and animal sera indicated that agreement between the original MA test and this new method exceeded 94%, whereas the original Galton microtechnique and the original MA test agreed in a maximum of 77% of the tests. This study indicates that the results obtained with the improved microtechnique are much more comparable to results obtained with the original MA test than are those obtained with the original Galton microtechnique.
520 citations
TL;DR: Edwardsiella tarda, an enteric, gram-negative bacterium, causes gas-filled, malodorous lesions in muscle tissue of channel catfish and its incidence and epizootiology are presented.
Abstract: Edwardsiella tarda, an enteric, gram-negative bacterium, causes gas-filled, malodorous lesions in muscle tissue of channel catfish. Incidence and epizootiology of the disease are presented.
228 citations
TL;DR: A method is described for determining the number of bacteria in a solution by the use of a machine which deposits a known volume of sample on a rotating agar plate in an ever decreasing amount in the form of an Archimedes spiral.
Abstract: A method is described for determining the number of bacteria in a solution by the use of a machine which deposits a known volume of sample on a rotating agar plate in an ever decreasing amount in the form of an Archimedes spiral. After the sample is incubated, different colony densities are apparent on the surface of the plate. A modified counting grid is described which relates area of the plate of volume of sample. By counting an appropriate area of the plate, the number of bacteria in the sample is estimated. This method was compared to the pour plate procedure with the use of pure and mixed cultures in water and milk. The results did not demonstrate a significant difference in variance between duplicates at the α = 0.01 level when concentrations of 600 to 12 × 105 bacteria per ml were used, but the spiral plate method gave counts that were higher than counts obtained by the pour plate method. The time and materials required for this method are substantially less than those required for the conventional aerobic pour plate procedure.
216 citations
TL;DR: Various ammonium sulfate concentrations and reaction conditions were employed in the fractionation of sera from rabbits, sheep, horses, and goats, and crude globulins and fluorescein isothiocyanate-labeled Globulins were successfully refractionated by one precipitation in the optimal sulfate concentration for the appropriate animal species.
Abstract: Various ammonium sulfate concentrations and reaction conditions were employed in the fractionation of sera from rabbits, sheep, horses, and goats. Precipitates and supernatant fluids were analyzed by electrophoresis to study the effects of the controlled variables. At room temperature, the third precipitate in 35% saturated (NH(4))(2)SO(4) was the best fraction from both rabbit and sheep sera; 80 to 90% of the gamma globulins were recovered. The second and third precipitates of horse sera proteins in 30% saturated (NH(4))(2)SO(4) were both satisfactory, but only 44% of the gamma globulin was recovered after three precipitations. Goat sera yielded a very satisfactory fraction; 80% of the gamma globulin was recovered after two precipitations-the first in 30% and the second in 45% saturated (NH(4))(2)SO(4). The composition of these fractions was not influenced by the pH of the sulfate solutions (pH 5.8 and 7.2), by a range of normal room temperatures (20 to 30 C), or by diluting the sera before fractionation. Crude globulins and fluorescein isothiocyanate-labeled globulins were successfully refractionated by one precipitation in the optimal sulfate concentration for the appropriate animal species. The refractionated products contained considerably less beta and alpha globulins than did the original crude fractions and little or no albumin.
203 citations
TL;DR: Low concentrations of ozone were ineffective when organic matter was present to interfere with the action of ozone on the bacterial cells and spores of these organisms exhibited the "all-or-none" die-away phenomenon normally associated with ozone treatment.
Abstract: THE MINIMAL LETHAL CONCENTRATION OF OZONE IN WATER WAS DETERMINED FOR THREE BACTERIAL SPECIES: Escherichia coli, Bacillus cereus, and Bacillus megaterium. A contact period of 5 min was selected. The lethal threshold concentration for the cells of B. cereus was 0.12 mg/liter while that for E. coli and B. megaterium was 0.19 mg/liter. Low concentrations of ozone were ineffective when organic matter was present to interfere with the action of ozone on the bacterial cells. Also determined during the study was the sensitivity of spores of B. cereus and B. megaterium to ozone in water. The threshold concentration required to kill the spores of both species was 2.29 mg/liter. The cells and spores of these organisms exhibited the "all-or-none" die-away phenomenon normally associated with ozone treatment.
201 citations
TL;DR: Results of a brining experiment indicated that oleuropein is degraded to antibacterial compounds when unheated olives are brined, a possible explanation for the previously reported observation that heating olives prior to brining renders them more fermentable by lactic acid bacteria.
Abstract: Oleuropein, the bitter glucoside in green olives, and products of its hydrolysis were tested for antibacterial action against certain species of lactic acid bacteria involved in the brine fermentation of olives. Oleuropein was not inhibitory, but two of its hydrolysis products, the aglycone and elenolic acid, inhibited growth of the four species of lactic acid bacteria tested. Another hydrolysis product, β-3,4-dihydroxyphenylethyl alcohol, was not inhibitory. The aglycone of oleuropein and elenolic acid were much more inhibitory when the broth medium contained 5% NaCl; 150 μg of either compound per ml prevented growth of Lactobacillus plantarum. A crude extract of oleuropein, tested by paper disk bioassay, was inhibitory to 3 of 17 species of bacteria screened, none of which were lactic acid bacteria. The acid hydrolysate of the extract was inhibitory to 11 of the bacteria, which included four species of lactic acid bacteria and other gram-positive and gram-negative species. Neither crude preparation was inhibitory to growth of the seven species of yeasts tested. A possible explanation is given for the previously reported observation that heating (3 min, 74 C) olives prior to brining renders them more fermentable by lactic acid bacteria. Results of a brining experiment indicated that oleuropein is degraded to antibacterial compounds when unheated olives are brined.
195 citations
TL;DR: Interspecies interactions are models for the rumen ecosystem interactions involved in the production of succinate by one species and its decarboxylation to propionate by a second species.
Abstract: Succinate is formed as an intermediate but not as a normal end product of the bovine rumen fermentation. However, numerous rumen bacteria are present, e.g., Bacteroides succinogenes, which produce succinate as a major product of carbohydrate fermentation. Selenomonas ruminantium, another rumen species, produces propionate via the succinate or randomizing pathway. These two organisms were co-cultured to determine if S. ruminantium could decarboxylate succinate produced by B. succinogenes. When energy sources used competitively by both species, i.e. glucose or cellobiose, were employed, no succinate was found in combined cultures, although a significant amount was expected from the numbers of Bacteroides present. The propionate production per S. ruminantium was significantly greater in combined than in single S. ruminantium cultures, which indicated that S. ruminantium was decarboxylating the succinate produced by B. succinogenes. S. ruminantium, which does not use cellulose, grew on cellulose when co-cultured with B. succinogenes. Succinate, but not propionate, was produced from cellulose by B. succinogenes alone. Propionate, but no succinate, accumulated when the combined cultures were grown on cellulose. These interspecies interactions are models for the rumen ecosystem interactions involved in the production of succinate by one species and its decarboxylation to propionate by a second species.
187 citations
TL;DR: A mycotoxin responsible for vomiting in swine has been isolated from Fusarium-contaminated field corn and has been given the trivial name vomitoxin.
Abstract: A mycotoxin responsible for vomiting in swine has been isolated from Fusarium-contaminated field corn. The compound was tentatively identified as a trichothecene, 3,7,15-trihydroxy-12,13-epoxy-trichothe-9-en-8-one, and has been given the trivial name vomitoxin.
180 citations
TL;DR: A battery of morphological, physiological, and biochemical tests, including paper chromatographic analysis of whole cell hydrolysates, was used to study 177 cultures of aerobic actinomycetes and a flow chart was devised to permit the step by step identification of unknown clinical isolates of these organisms.
Abstract: A battery of morphological, physiological, and biochemical tests, including paper chromatographic analysis of whole cell hydrolysates, was used to study 177 cultures of aerobic actinomycetes. One hundred thirty-five of the 177 were submitted as diagnostic laboratory specimens; of these, 129 were identified as belonging to 1 of 10 genus or species groups. The tests and procedures used were found to be relatively easy to perform and interpret. On the basis of the results, a flow chart was devised to permit the step by step identification of unknown clinical isolates of these organisms.
175 citations
TL;DR: A new differential medium, Rimler-Shotts, was tested with 109 isolates representing 13 genera of bacteria obtained from aquatic environments and animals and was effective in presumptive identification of the strains of Aeromonas hydrophila examined, with 94% accuracy.
Abstract: A new differential medium, Rimler-Shotts, was tested with 109 isolates representing 13 genera of bacteria obtained from aquatic environments and animals. This medium was effective in presumptive identification of the strains of Aeromonas hydrophila examined, with 94% accuracy. Strains of Citrobacter which were hydrogen sulfide-variable could not be separated from A. hydrophila. This medium was designed to facilitate diagnosis of A. hydrophila infections in animals and humans.
151 citations
TL;DR: The procedure for biological and chemical detection of trichothecene-type mycotoxins and its application to the screening of Fusarium for toxic strains were described.
Abstract: The procedure for biological and chemical detection of trichothecene-type mycotoxins and its application to the screening of Fusarium for toxic strains were described
TL;DR: The amino acid profile of this yeast protein indicates that it could serve as a good source of food protein and feeding studies with rats show the yeast to have no toxic effects.
Abstract: A yeast capable of growth on methanol as its sole carbon-energy source was isoalted from soil samples and identified as a strain of Hansenula polymorpha. A continuous enrichment culture at 37 C with a simple mineral salts medium was used to select this organism. The isolate, designated DL-1, has a maximal specific growth rate of 0.22 per h, at pH 4.5 to 5.5 and temperatures of 37 to 42 C, in simple mineral salts medium with methanol (0.5%), biotin, and thiamine. Growth occurred in a chemostat at temperatures up to 50 C, with strong growth at 45 C. The maximal growth yield of the yeast on methanol was 0.36 g of dry cell weight per g of methanol, and the yield on oxygen was 0.37 g of dry cell weight per g of O2. Protein content of the isolate is 46%, and total nucleic acid content varies from 5.0 to 7.0% with increasing growth rate from 0.08 to 0.20 per h. The amino acid profile of this yeast protein indicates that it could serve as a good source of food protein. Feeding studies with rats show the yeast to have no toxic effects.
TL;DR: A selective medium containing Todd-Hewitt broth, sheep blood, nalidixic acid, and gentamicin sulfate was found to enhance significantly the isolation of group B streptococci from vaginal cultures.
Abstract: A selective medium containing Todd-Hewitt broth, sheep blood, nalidixic acid, and gentamicin sulfate was found to enhance significantly the isolation of group B streptococci from vaginal cultures. Preparation of the medium, which is stable for up to 4 weeks at 4 C, is simple and inexpensive. Use of such a medium should facilitate identification of vaginal colonization with group B streptococci.
TL;DR: Increasing the initial temperature of the rice fermentation of Aspergillus parasiticus NRRL 2999 from 15 to 21 C after 24 h of incubation and then to 28 C after 48 h resulted in about a fourfold increase in total aflatoxin over the usual fermentation.
Abstract: Increasing the initial temperature of the rice fermentation of Aspergillus parasiticus NRRL 2999 from 15 to 21 C after 24 h of incubation and then to 28 C after 48 h resulted in about a fourfold increase in total aflatoxin over the usual fermentation which is held constant at 28 C for 6 days. The percentage of aflatoxin B1, the most toxic component, in the total aflatoxin was also increased.
TL;DR: In rhesus monkeys a wide dosage range of 17D yellow fever (YF) vaccine extending to a level even below that recommended for vaccination of man elicited an immune response providing solid protection to challenge with virulent Asibi strain YF virus.
Abstract: In rhesus monkeys a wide dosage range of 17D yellow fever (YF) vaccine extending to a level even below that recommended for vaccination of man elicited an immune response providing solid protection to challenge with virulent YF virus. Forty-three of 45 monkeys vaccinated with 102.3 or greater weanling mouse mean lethal doses of 17D vaccine were resistant to challenge 20 weeks later with virulent Asibi strain YF virus. Monkeys given graded doses of lesser amounts of vaccine were progressively more susceptible to challenge. With a vaccine dose ≥ 102.3 weanling mouse mean lethal doses, plaque neutralization (PN) seroconversion rates were 90% or greater, whereas hemagglutination-inhibiting (HI) and complement-fixing (CF) seroconversion rates were unrelated to vaccine dosage and were generally in the range of 20 to 80%. Ninety-six percent (51 of 54) of immune monkeys had PN titers ≥0.7 log10 (fivefold) neutralization index as compared to approximately 55 to 65% who showed HI or CF titers ≥2 log2 (fourfold) neutralization index. After challenge with Asibi strain YF virus, antibody titers of all three tests increaed equally. In rhesus monkeys PN antibody titers were well correlated with YF immunity, whereas HI and CF antibody titers were not.
TL;DR: A rapid and simple procedure is described for analysis of fermentation products from anaerobic bacteria grown in glucose broth for volatile fatty acids as well as for lactic, pyruvic, and succinic acids.
Abstract: A rapid and simple procedure is described for analysis of fermentation products from anaerobic bacteria grown in glucose broth. A 1-ml sample of the culture is drained through cation-exchange resin in a Pasteur pipette. The effluent fluid is directly analyzed isothermally in a gas chromatograph for volatile fatty acids (C2 to C6) as well as for lactic, pyruvic, and succinic acids. This procedure is considered to be suitable for routine use in clinical bacteriology.
TL;DR: This article corrects the article on p. 528 in vol.
Abstract: Several factors were found to influence the growth inhibition test. Inoculum size and amount of antiserum are well known variables, but the method of applying the antiserum, the incubation temperature, and the pH of the agar medium also play significant roles. The growth inhibition test modified according to these findings was found to be specific and well suited for the classification and identification of human T-mycoplasmas.
TL;DR: A nitrite actidione polymyxin agar was developed for the enumeration of lactic acid bacteria and was effective in recovering organisms from pure cultures and from foods.
Abstract: A nitrite actidione polymyxin agar was developed for the enumeration of lactic acid bacteria. It was effective in recovering organisms from pure cultures and from foods.
TL;DR: In this paper, three strains of Pseudomonas cepacia isolated and maintained in distilled water and on a laboratory-subcultured strain transferred to distilled water were investigated.
Abstract: Studies were conducted on three strains of Pseudomonas cepacia isolated and maintained in distilled water and on a laboratory-subcultured strain transferred to distilled water Optimum growth rates and maximum population yields of the four strains in distilled water were obtained at 37 C, although high population levels (106-107/ml) were reached and maintained over extended incubation periods at temperatures from 18 C to 42 C Two strains were able to grow in distilled water at temperatures ranging from 12 C to 48 C and to survive 48 h and 21 days at 50 C and 10 C, respectively Cells from distilled water cultures inoculated into Trypticase soy broth showed an immediate two- to three-log drop at upper and lower temperature limits; survivors were able to initiate logarithmic growth Results obtained in morphological, biochemical, and antibiotic tests affirmed the strain differences noted in growth studies Images
TL;DR: A nitrogen-deficient medium and m-Endo agar were employed in the isolation of members of the tribe Klebsielleae from surfaces of vegetables and seeds, finding that vegetables containing K. pneumoniae may constitute a potential reservoir for human nosocomial genitourinary or other infections.
Abstract: A nitrogen-deficient medium and m-Endo agar were employed in the isolation of members of the tribe Klebsielleae from surfaces of vegetables and seeds. With m-Endo agar at an incubation temperature of 37 C, nearly 50% of the vegetables and seven out of seven seed samples yielded organisms which biochemically and serologically were identified as Klebsiella pneumoniae, Viable counts were generally in the range of 103 cells per g of vegetable peel or seed. Organisms classified as K. pneumoniae exhibited seven different IMViC patterns, with the --++, ++++, and -+++ patterns most common. Seven of the eleven K. pneumoniae serotypes encountered have previously been isolated from human urinary tract and other infections. Fifty percent of the 40 K. pneumoniae examined exhibited positive acetylene-reducing activity, i.e., they possessed the capability for fixing N2. Vegetables containing K. pneumoniae may constitute a potential reservoir for human nosocomial genitourinary or other infections.
TL;DR: Disodium phosphonoacetate when administered orally or topically to mice experimentally infected with herpes simplex virus was able to significantly reduce the mortality associated with the agent.
Abstract: Disodium phosphonoacetate when administered orally or topically to mice experimentally infected with herpes simplex virus was able to significantly reduce the mortality associated with the agent. In addition, this compound was able to reduce herpesvirus lesions on the corneas of infected rabbits.
TL;DR: Oleuropein and its aglycone had similar threshold levels for detection of bitterness, whereas elenolic acid and beta-3,4-dihydroxyphenylethyl alcohol were not judged to be bitter.
Abstract: Oleuropein, an intensely bitter glucoside, was isolated from green olives. Hydrolysis products obtained from oleuropein in sufficient quantity for further tests were: (i) β-3,4-dihydroxyphenylethyl alcohol prepared by acid hydrolysis of oleuropein; (ii) elenolic acid obtained by methanolysis of oleuropein, isolation of the intermediate acetal, and subsequent acid hydrolysis; and (iii) oleuropein aglycone formed by the action of β-glucosidase on the parent glucoside. Mass spectral verification of the isolated compounds and ultraviolet absorption data are given. Oleuropein and its aglycone had similar threshold levels for detection of bitterness, whereas elenolic acid and β-3,4-dihydroxyphenylethyl alcohol were not judged to be bitter.
TL;DR: Kinetics of growth for the wild-type, red S. marcescens and a white mutant were identical when incubated at 27 C, but the wild type produced abundant pigment, suggesting that prodigiosin is a secondary metabolite.
Abstract: Prodigiosenes (prodigiosin and prodigiosin-like pigments) are known to be synthesized by only one genus of Eubacteriales and by two genera of Actinomycetales. Biosynthesis by Serratia marcescens occurs over a relatively narrow range of temperatures, although the bacteria grow over a broad range. When cultures of S. marcescens were incubated at 27 C in 1.0% casein hydrolysate, viable count and protein attained maximal values within 24 to 48 h, whereas prodigiosin did not reach a maximum until 96 h. The greatest amount of pigment was synthesized when cultures were in the senescent phase of growth. Suspensions of nonproliferating bacteria incubated at 27 C in only L-alanine also synthesized prodigiosin, although at a slower rate than growing cultures. Kinetics of growth for the wild-type, red S. marcescens and a white mutant were identical when incubated at 27 C, but the wild type produced abundant pigment. These results plus other data obtained from the literature suggest that prodigiosin is a secondary metabolite. The importance of this proposal to understanding the function of prodigiosin in S. marcescens is discussed.
TL;DR: The sporicidal properties of hydrogen peroxide were evaluated at concentrations of 10 to 41% and at temperatures of 24 to 76 C as discussed by the authors, and the organisms tested and their relative resistance at 24 C to 25.8% H2O2 were: Bacillus subtilis SA 22 > B. subtILis var. globigii, B. stearothermophilus > Clostridium sp. putrefactive anaerobe 3679 > S. aureus, with "D" values of 7.3, 2, 1.8
Abstract: The sporicidal properties of hydrogen peroxide were evaluated at concentrations of 10 to 41% and at temperatures of 24 to 76 C. The organisms tested and their relative resistance at 24 C to 25.8% H2O2 were: Bacillus subtilis SA 22 > B. subtilis var. globigii > B. coagulans > B. stearothermophilus > Clostridium sp. putrefactive anaerobe 3679 > S. aureus, with “D” values of 7.3, 2, 1.8, 1.5, 0.8., and 0.2 min, respectively. Heat shocking spores prior to hydrogen peroxide treatment decreased their resistance. Wet spores were more resistant than dry spores when good mixing was achieved during hydrogen peroxide treatment. Inactivation curves followed first-order kinetics except for a lag period where the inactivation rate was very slow. Increasing the H2O2 concentration and the temperature reduced the lag period.
TL;DR: It was found that, by acidification, viruses in large volumes of water could be efficiently adsorbed to epoxy-fiber-glass and nitrocellulose filters in the absence of exogenously added salts.
Abstract: An improved method for concentrating viruses from large volumes of clean waters is described. It was found that, by acidification, viruses in large volumes of water could be efficiently adsorbed to epoxy-fiber-glass and nitrocellulose filters in the absence of exogenously added salts. Based upon this finding, a modified version of our previously described virus concentration system was developed for virus monitoring of clean waters. In this procedure the water being tested is acidified by injection of N HCl prior to passage through a virus adsorber consisting of a fiber-glass cartridge depth filter and an epoxy-fiber-glass membrane filter in series. The adsorbed viruses are then eluted with a 1-liter volume of pH 11.5 eluent and reconcentrated by adsorption to and elution from a small epoxy-fiber-glass filter series. With this method small quantities of poliovirus in 100-gallon (378.5-liter) volumes of tapwater were concentrated nearly 40,000-fold with an average virus recovery efficiency of 77%. Images
TL;DR: Volatile compounds produced by Pseudomonas putrefaciens, P. fluorescens, and an Achromobacter species in sterile fish muscle were identified by combined gas-liquid chromatography and mass spectrometry.
Abstract: Volatile compounds produced by Pseudomonas putrefaciens, P. fluorescens, and an Achromobacter species in sterile fish muscle (Sebastes melanops) were identified by combined gas-liquid chromatography and mass spectrometry. Compounds produced by P. putrefaciens included methyl mercaptan, dimethyl disulfide, dimethyl trisulfide, 3-methyl-1-butanol, and trimethylamine. With the exception of dimethyl trisulfide, the same compounds were produced by an Achromobacter species. Methyl mercaptan and dimethyl disulfide were the major sulfur-containing compounds produced by P. fluorescens.
TL;DR: A heat-stable, extracellular proteolytic enzyme was isolated from Pseudomonas fluorescens P26 by growth of organisms in broth, centrifugation, sterilization by filtration, ammonium sulfate precipitation, dialysis, and protein separation by passage through a Sephadex G-100 column.
Abstract: A heat-stable, extracellular proteolytic enzyme was isolated from Pseudomonas fluorescens P26. Brain heart infusion broth (Fisher Scientific Co.), pH 7.5, and incubation at 21 C provided the optimal conditions for bacterial growth for enzyme production. The organism had a D value of 2.6 min at 62.8 C (145 F). The enzyme, however, was quite heat-stable, requiring 15 hr at 62.8 C, 8 hr at 71.4 C, and 9 min at 121 C for complete inactivation. Milk, whey, and casein each had a protective effect on the enzyme against heat inactivation. Purification was accomplished by growth of organisms in broth, centrifugation, sterilization by filtration, ammonium sulfate precipitation (55% saturation), dialysis (against six changes of water), and protein separation by passage through a Sephadex G-100 column. Ultracentrifugation revealed a single band with a sedimentation coefficient of 1.51 which suggested a molecular weight of approximately 23,000. As little as 0.2 unit of the purified enzyme caused detectable flavor defects during 30 days of storage at 4 C, and the Hull test for liberation of tyrosine compared favorably in sensitivity with the sensory method in milk.
TL;DR: The reproducibility of results and the variety and number of auxotypes indicate the potential value of the auxotyping system as an epidemiological tool.
Abstract: A system is described for differentiating clinical isolates of Neisseria gonorrhoeae based on their growth or absence of growth on a set of 11 chemically defined agar media. The complete medium, NEDA, contains all of the compounds required for gonococcal growth; but isolates differ in their ability to grow on NEDA from which selected compounds are individually omitted. The differential compounds include L-proline, L-arginine, L-ornithine, L-methionine, hypoxanthine, uracil, thiamine, and thiamine pyrophosphate. A distinctive pattern of growth responses on the standard media defines an auxotype. Twenty auxotypes were found among a group of 251 gonococci which were isolated from patients examined in the clinics of one city during a 3-month span of time. Another collection of 74 strains from several different countries yielded two additional auxotypes. The stability of the nutritional requirements on which the auxotyping depends was verified in two ways. Cultures isolated from different anatomic sites of a patient or from sexual partners represented the same auxotype, as did cultures which were repeatedly isolated from cases of presumptive treatment failures. Also, the auxotypes of gonococci remained the same after numerous subcultures. The reproducibility of results and the variety and number of auxotypes indicate the potential value of the auxotyping system as an epidemiological tool.
TL;DR: Results indicated that nitrite effectively inhibited botulinal toxin formation at commercially employed levels in wieners and that detectable quantities of nitrosamines were not produced during preparation and processing of the product for consumption.
Abstract: Wieners were formulated and processed approximating commercial conditions as closely as possible. Twenty-four batches of product were made with the addition of six levels of sodium nitrite (0, 50, 100, 150, 200, and 300 μg/g), four levels of sodium nitrate (0, 50, 150, and 450 μg/g), and two levels of Clostridium botulinum (0 and 620 spores/g). After formulation, processing, and vacuum packaging, portions of each batch were incubated at 27 C or held for 21 days at 7 C followed by incubation at 27 C for 56 days. The latter storage condition approximated distribution of product through commercial channels and potential temperature abuse at the consumer level. Samples were analyzed for botulinal toxin, nitrite, and nitrate levels after 3, 7, 14, 21, 28, and 56 days of incubation. When nitrite was not added, toxic samples were detected after 14 days of incubation at 27 C. At the lowest level of nitrite added (50 μg/g), no toxic samples were observed until 56 days of incubation. Higher levels of nitrite completely inhibited toxin production throughout the incubation period. Nine uninoculated samples, representing various levels and combinations of nitrite and nitrate, were evaluated organoleptically. The flavor quality of wieners made with nitrite was judged significantly higher (P = 0.05) than of wieners made without nitrite. The nine samples were negative for 14 volatile nitrosamines at a sensitivity level of 10 ng/g. The results indicated that nitrite effectively inhibited botulinal toxin formation at commercially employed levels in wieners and that detectable quantities of nitrosamines were not produced during preparation and processing of the product for consumption.
TL;DR: Variability in the susceptibility of group D non-enterococcal streptococci to oxacillin and methicillin sensitivity disks limited the usefulness of these tests for presumptive identification of either enterococci or group D streptitisci.
Abstract: Bile-esculin (Difco), modified bile-esculin (Difco), selective enterococcus (Pfizer Co.), and eosin-methylene blue agar media were evaluated for accuracy in identifying group D streptococci. The regular and modified bile-esculin media performed equally well, but the selective enterococcus and eosin-methylene blue agars did not accurately differentiate the group D from non-group D streptococci. A modified 6.5% NaCl broth was compared with unmodified 6.5% NaCl broth and Streptococcus faecalis (SF; Difco) broth for accuracy in differentiating enterococci from non-enterococci. The modified and unmodified broths worked equally well in the salt tolerance test, but the lot-to-lot variability of SF broth made this medium unusable as an indicator for enterococci. With all seven media, the number of strains giving positive tests decreased when the tests were incubated at 45 C as compared with 35 C, and the number of strains giving negative tests increased. Thus, the number of false-positive identifications decreased, but the number of false-negative identifications increased. Variability in the susceptibility of group D non-enterococcal streptococci to oxacillin and methicillin sensitivity disks limited the usefulness of these tests for presumptive identification of either enterococci or group D streptococci.