Quantitation of Clostridium perfringens in foods

A procedure is described for identifying and enumerating Clostridium perfringens in foods by means of a simplified agar plating method, followed by confirmation of black colonies in tubes of motility-nitrate medium and sporulation broth. The test is routinely completed within 48 hr. Under experimental conditions, the procedure has been used to quantitatively recover various levels of C. perfringens contamination in a variety of foods and has recovered as few as ten C. perfringens per g without interference from food constituents and associated flora. Under practical conditions of field application, the method has been used to investigate five food-poisoning outbreaks, and C. perfringens was implicated as the etiological agent in two of these outbreaks.

Sporulation of Clostridium botulinum types A, B, and E, Clostridium perfringens, and putrefactive anaerobe 3679 in dialysis sacs

Schneider, Morris D. (Quartermaster Food and Container Institute for the Armed Forces, U.S. Army, Chicago, Ill.), Nicholas Grecz, and Abe Anellis. Sporulation of Clostridium botulinum types A, B, and E, Clostridium perfringens, and Putrefactive Anaerobe 3679 in dialysis sacs. J. Bacteriol. 85:126-133. 1963.-Concentrated cultures of spores of Clostridium botulinum type A (33A, 37A), B (41B, 51B), and E (strain VH), C. perfringens (strain E), and Putrefactive Anaerobe 3679 were prepared in intussuscepted cellulose dialysis tubing. The apparatus consisted of a telescoped cellulose bag immersed into a suitable sporulation medium in a large Pyrex tube. The initial inoculum was a heavy suspension in physiological saline solution of either vegetative cells or heat-shocked spores. The seed material was introduced into the interior of the dialysis bag. Maximal spore populations were obtained within 10 to 12 days. Strains of C. botulinum type E and C. perfringens, known for their poor sporulation in conventional cultures, gave good spore crops in the dialysis bag. Some crops were of the order of 10(10) and 10(11) viable spores per liter of medium. The spores produced in the dialysis bag were conspicuously large, particularly after incubation for 20 to 30 days. Observations of the characteristics of spores formed in telescoped bags indicate that two highly resistant strains of C. botulinum, 33A and 41B, were apparently less resistant to gamma rays than spores of the same strains produced in identical media in conventional cultures.

Characterization of Clostridium perfringens (welchii) isolated from market poultry

Strains of Clostridium perfringens capable of producing heat-resistant spores, characteristic of the food-poisoning types, were not recovered in a random survey of feces and livers of market poultry. Favorable growth response with a known food-poisoning strain indicated that the media and methods employed were adequate. Spores produced in vitro from this strain survived at 100 C for several hours. Animal feeding experiments with this strain showed that heat-resistant spores (surviving for 1 hr at 100 C) could be readily demonstrated 24 hr after oral instillation of vegetative cells in mouse feces, but not in chicken feces. One experiment suggests that this strain might adapt to the environment of the intestinal tract of chickens, but not all of the spores recovered were as heat resistant as those of the parent culture.

Fate of partially purified C-14-labeled toxin of Clostridium perfringens

Ellner, Paul D. (University of Florida, Gainesville). Fate of partially purified C(14)-labeled toxin of Clostridium perfringens. J. Bacteriol. 82:275-283. 1961.-A study was made of the fate of Clostridium perfringens toxin in susceptible animals. Labeled toxin was prepared by growing C. perfringens type A in a complex casein hydrolyzate medium containing a tryptic hydrolyzate of C(14)-labeled algal protein. The toxin was purified about 30-fold (in terms of lecithinase activity) by ammonium sulfate and acetone precipitations. The tagged toxin was injected intravenously into mice and rabbits, and the disappearance from the blood stream, deposition in organs and appearance in urine and expired air determined by measurement of radioactivity. Experimental data showed that toxin disappears rapidly from the bloodstream following intravenous injection, with radioactivity appearing in the urine and expired air shortly thereafter (10 to 20 min). The organs primarily responsible for the uptake of toxin from the blood are the liver (72%), lungs (15%), kidney (8%), and spleen (5%). The toxin is not bound to skeletal muscle. Fractionation of the liver into subcellular particles by centrifugation showed the radioactivity to be concentrated in the mitochondrial fraction. These experiments indicate that the toxin is rapidly removed from the circulating blood, is metabolized, and breakdown products excreted in the urine, with 1 carbon fragments eliminated as CO(2) in the expired air.

Histamine and 5-hydroxytryptamine in the intestinal tract of germ-free animals, animals harbouring one microbial species and conventional animals

Histamine and 5-hydroxytryptamine were determined in the intestinal tract of germfree and conventional rats and mice. Comparable histamine data were collected in Clostridium perfringens mono-associated rats, while 5-hydroxytryptamine determinations were extended to include the chicken. In rats and mice harbouring an intestinal microflora, bacterial formation of histamine occurs mainly in the caecum. Compared to values found in germ-free animals, histamine levels in the wall of the small intestine of the conventional animal tend to be higher, though in the rat the data are not consistent. Mono-association (harbouring of one microbial species) of germ-free rats with a histamine-producing strain of Clostridium perfringens resulted in high histamine concentrations in the caecal contents, but failed to increase the histamine levels in the wall of the small intestine. 5-Hydroxytryptamine levels in the intestinal wall in the presence of an intestinal flora were generally lower than those in germ-free animals. Modification of the flora by dietary administration of penicillin to mice partly abolished its depressing effect.

Rearing of germfree and monocontaminated chicks in rigid plastic isolators

A Plexiglas isolator for rearing germfree vertebrates is described. Plastic components were precut and finished by a Plexiglas supplier. This equipment is relatively inexpensive; moreover, neither special facilities nor skills are required in their construction. Advantages of this type of isolator are: readily dismantled for cleaning, durable, excellent visibility of the interior, and minimal maintenance. In 30 separate groups of animals, 27 of these yielded germfree chicks. Many of these chicks were reared germfree for 4 weeks; and several were maintained for about 2 months, without microbial contamination. Pure cultures of Candida albicans, Streptococcus faecalis, and Clostridium perfringens were established as monocontaminations in the intestinal tracts of chickens. In contrast, Alcaligenes faecalis ATCC 9220 failed to grow in the gut of chicks, following peroral administration of this organism. All chicks described were employed on other experiments, and were killed for various assays at times specified.

Incidence of Clostridium perfringens in American foods

Food samples were examined for the presence of Clostridium perfringens. A medium described by Mossel and later modified by Angelotti et al. was used for the detection and enumeration of C. perfringens. The incidence of C. perfringens observed in the foods examined was 6.1%. C. perfringens was recovered from 2.7% of the commercially prepared frozen foods, 3.8% of fruits and vegetables, 5.0% of spices, 1.8% of home-prepared foods, and 16.4% of raw meat, poultry, and fish.

RESPONSE OF CLOSTRIDIUM PERFRINGENS SPORES AND VEGETATIVE CELLS TO TEMPERATURE VARIATION

The vegetative cells and spores of four strains of Clostridium perfringens were examined to determine the effect of lowered and elevated temperatures. Spores were produced by following the method of Ellner, and vegetative cells were obtained from thioglycolate cultures. After exposure to freezing or refrigeration temperatures (-17.7 and 7.1 C, respectively), only small numbers of the vegetative cells were recovered. After similar treatment, 16 to 58% of the spores were recovered. Essentially no vegetative cells and few spores survived holding at 80 C for 10 min. Although all strains were isolated from food, only one strain of the four studied had its origin in a food-poisoning outbreak, and it had been carried on laboratory media for approximately 10 years.

BACTERIAL NUCLEOTIDASES

Kohn, J. (Queen Mary's Hospital, London, England) and J. L. Reis. Bacterial nucleotidases. J. Bacteriol. 86:713-716. 1963.-The 3- and 5- nucleotidase activity in various bacterial species was investigated. Both enzymes were found in bacterial extracts in varying proportions. The nucleotidases were found to be very active in Proteus vulgaris, in which organism they were studied in detail. The relative activities, the pH optima, and the effect of metal ions were investigated. It was concluded that bacterial 3- and 5-nucleotidases are distinct and separate enzymes.

SEROLOGICAL GROUPING OF THE PATHOGENIC CLOSTRIDIA

Ellner, Paul D. (University of Vermont, Burlington), and Stanley S. Green. Serological grouping of the pathogenic clostridia. J. Bacteriol. 86:1098-1100. 1963.-By use of the soluble antigens of ten species of pathogenic clostridia and specific globulins, it has been possible to divide these organisms into a number of groups based upon the presence or absence of precipitin lines in agar gel. A scheme for such a grouping is presented, and the utility of this method is discussed.

CLOSTRIDIUM PERFRINGENS IN MEAT AND MEAT PRODUCTS

A total of 262 specimens of meat and meat dishes were examined for the presence of Clostridium perfringens. Of this total, 161 were raw, unprocessed beef, veal, lamb, pork, or chicken; 101 were processed meats and meat dishes. C. perfringens was isolated from 113 (43.1%) of these specimens. The highest percentage of contamination (82%) was found in veal cuts, and the lowest (4.7%) in sliced sandwich meats and spreads. Only 2 of the 113 isolates were shown to produce heat-resistant spores, which indicates a very low incidence (0.8%) of contamination. These findings indicate that outbreaks of C. perfringens food-borne disease in the Cincinnati area are caused principally by the contamination of the food with vegetative cells or spores of the organism after cooking. Studies of the effects of various holding temperatures on the growth of C. perfringens indicated that, in the range of 5 to 15 C, no multiplication would occur, but that viable cells would still be present at the end of a 5-day holding period. Extremely rapid growth occurred at temperatures around 45 C, and complete inhibition of growth was accomplished between 49 and 52 C.

RAPID TECHNIQUE FOR THE ENUMERATION OF CLOSTRIDIUM PERFINGENS

A new medium, Tryptone-sulfite-neomycin (TSN) agar, and an incubation procedure for the enumeration of Clostridium perfringens are described. Tolerance to neomycin, optimal growth at 46 C, and sulfite-reducing properties of C. perfringens were used as a basis for development of the medium. Comparisons were made between sulfite-polymyxin-sulfadiazine (SPS) agar and TSN agar at 37 and 46 C with C. perfringens and other organisms. These studies indicate the quantitative and selective superiority of TSN agar, incubated at 46 C, over SPS agar.

ANTIMICROBIAL ACTION OF NITROGEN-CONTAINING STEROIDS

Smith, Rodney F. (University of Maryland, Baltimore), Donald E. Shay, and Norman J. Doorenbos. Antimicrobial action of nitrogen-containing steroids. J. Bacteriol. 85:1295-1299. 1963.-A new group of 16 synthetic nitrogen-containing steroids have been tested against a variety of microorganisms for antimicrobial properties. The gradient plate screening method, serial dilution, and dry weight techniques were used in the studies. The organisms tested consisted of 14 gram-negative bacteria, 10 gram-positive bacteria, 2 actinomycetes, 7 yeasts, and 8 molds. Inhibitory properties were found to be specific and potent in four compounds, with inhibitory concentrations as low as 0.37 mug/ml. Three of the active steroids are 4-aza cholestanes and one is a 4-nor-3,5-secocholestane amide. Sensitivity to the compounds was greatest in the gram-positive bacteria, followed by the yeasts and molds. The gram-negative bacteria were not inhibited. All 16 steroids interfered to some extent with pigmentation in Serratia marcescens but not with pigment production in Pseudomonas aeruginosa. In a few instances, some of the molds were stimulated by the steroids at a concentration of 250 mug/ml.

SEROLOGY OF THE SOLUBLE ANTIGENS OF THE PATHOGENIC CLOSTRIDIA

Ellner, Paul D. (University of Vermont, Burlington), and Stanley S. Green. Serology of the soluble antigens of the pathogenic clostridia. J. Bacteriol. 86:1084-1097. 1963.-Soluble antigens of 42 strains, representing nine species of clostridia commonly occurring in human infections, were prepared by growing the organisms in a nonantigenic medium. Serological studies demonstrated the occurrence of considerable strain variation within each species. Interactions among the nine species, as well as with the previously characterized Clostridium perfringens, were also investigated. Extreme heterogeneity was observed among the species studied, with many cross-reactions due to common antigens, although species-specific antigens were also found in some cases. Occasional weak reactions were also demonstrated between certain clostridial antisera and the soluble antigens of three of the four species of Bacillus studied.

EFFECT OF HIGH FAT DIETS ON INTESTINAL MICROFLORA AND SERUM CHOLESTEROL IN RATS

Graber, C. D. (Baylor University College of Medicine, Houston, Tex.), R. M. O'Neal, and E. R. Rabin. Effect of high fat diets on intestinal microflora and serum cholesterol in rats. J. Bacteriol. 89:47-51. 1965.-Differential bacterial counts of feces and total plasma cholesterol determinations were performed on 60 Wistar rats fed several high lipid diets for a period of approximately 6 months. Fecal flora remained relatively stable irrespective of diet, but cholesterol levels rose in animals fed butter and sodium cholate. The six most commonly cultured organisms in all diets were enterococci, Proteus, lactobacilli, Escherichia coli, Staphylococcus aureus, and other micrococci. No enteric pathogens which did not ferment lactose or fermented it slowly were grown. Fungi and yeasts were rare. Aerobes generally outnumbered anaerobes in proportions which were sometimes as high as 300:1. Clostridium perfringens isolations were consistently high in animals given the butter diets, particularly when sodium cholate was added. Evidence is reviewed which indicates that this organism may play a role in bile salt and cholesterol metabolism. This experiment would seem to demonstrate that differences in plasma-cholesterol levels among the various dietary groups of rats were the result of dietary factors rather than alteration in intestinal flora.

RESISTANCE OF CLOSTRIDIUM PERFRINGENS TYPE A SPORES TO GAMMA-RADIATION

The radiation resistance of the spores of a classical strain and of an atypical, heat-resistant strain of Clostridium perfringens was determined. Spores were produced in Ellner's and in a Trypticase broth medium. Approximately 10(6) viable spores per milliliter were suspended in 0.06 m phosphate buffer and irradiated with gamma rays from cobalt-60; the survivors were counted in Tryptone-yeast extract-agar by the Prickett-tube technique. Radiation D values for spores of the atypical strain in phosphate buffer and in cooked-meat broth were 0.23 and 0.30 Mrad, respectively, and the D value of the classical strain was 0.25 Mrad in phosphate buffer. Spores of the classical and atypical strains of C. perfringens type A are characterized by differences in heat resistance; yet, all strains tested demonstrated similar radiation resistance. Also, the spores were more resistant to ionizing radiation in cooked-meat broth than in phosphate buffer.

THE SIZE DISTRIBUTION OF AIRBORNE PARTICLES CARRYING MICRO-ORGANISMS

Values are given for the median equivalent diameters and for the inter-quartile range, of airborne particles carrying a variety of micro-organisms.

Organisms associated with human disease or carriage were usually found on particles in the range 4–20 μ equivalent diameter.

Many fungi appeared to be present in the air as single spores.

We should like to acknowledge the collaboration of Dr Yvonne M. Clayton in the collection and examination of the fungal samples.

CHARACTERISTICS OF CLOSTRIDIUM PERFRINGENS STRAINS ASSOCIATED WITH FOOD AND FOOD-BORNE DISEASE

Hall, Herbert E. (Robert A. Taft Sanitary Engineering Center, Cincinnati, Ohio), Robert Angelotti, Keith H. Lewis, and Milton J. Foter. Characteristics of Clostridium perfringens strains associated with food and food-borne disease. J. Bacteriol. 85:1094-1103. 1963.-A total of 83 strains of Clostridium perfringens-30 from England, Europe, and Asia, associated with food-poisoning outbreaks; 28 from the United States, associated with outbreaks or contaminated foods; and 25 from natural or pathological sources-have been studied to determine their serological relationships, sporulation and heat-resistance of spores, and their hemolytic activity on mammalian bloods. A comparison of the results obtained with these three groups of strains reveals that the Eurasian group is characterized by serological typability, poor sporulation with the production of heat-resistant spores, and a hemolytic activity limited to the production of partial hemolysis on horse, ox, and sheep bloods, whereas the strains from natural and pathological sources in this country are not serologically typable, sporulate well but the spores are not heat-resistant, and are hemolytically active, producing both partial and complete hemolysis on horse, ox, and sheep bloods. The American food-poisoning strains have a wide variety of characteristics. Some strains resemble the Eurasian in their serological typability and the production of heat-resistant spores, but sporulation and hemolytic activity are more like the strains from classical sources. On the basis of these data, it appears unlikely that C. perfringens food-poisoning outbreaks in the United States are restricted to strains meeting the criteria of classification described by British workers and that the isolation of large numbers of any strain of this organism from an incriminated food must be considered as having a possible bearing on the etiology of the outbreak.