An Improved Stone Medium for the Isolation and Testing of Food‐poisoning Staphylococci

Abstract

Rapid bacteriological study of food-poisoning outbreaks is essential for the prevention of recurrences. Direct application of the coagulase test, Chapman (1944a), to suspected foods and handlers has proved useful for rapid presumptive field investigation, Chapman and Domingo (1946), but the results must be confirmed by cultural methods. The in vivo demonstration of gastroenterotoxigenicity is desirable to add weight to the scientific evidence but it does not lend itself to routine testing of the numerous complaints of "food poisoning" received by health authorities and, because so many strains not associated with outbreaks also produce gastroenterotoxin, the results are not as conclusive as is generally thought [e.g., Fulton (1943) 1. For epidemiological purposes, therefore, a rapid, simple, highly reliable bacteriological procedure would be of inestimable value to the busy sanitarian. The development of such a method will be described here. No claim is made for identification of food-poisoning staphylococci "with certitude,'' indeed absolute accuracy is a biological rarity.Stone (1935) proposed a culture-medium technic by which food-poisoning staphylococci give a clear zone of gelatinolysis around the colonies on a special gelatin-agar medium. As originally applied the method proved to be nonspecific because many strains from outbreaks gave a negative reaction and many pathogenic and nonpathogenic strains from other sources produced considerable zoning. Later, Stone (1938) maintained that, if the test is applied promptly after isolation, nearly all implicated staphylococci show this zoning. Chapman, Lieb, and Cnrcio (1937) pointed out that the reaction is applicable only to pigmented strains. They found that, in addition to the Stone reaction, typical f ood-poisoning staphylococci produce pigment, coagulate plasma, and ferment mannitol and have other properties that are characteristic of pathogenic staphylococci. Other investigators claimed that many f ood-poisoning staphylococci do not give these reactions but a survey of the literature, Chapman (1942), showed that about 95 per cent of the published results of these tests were positive. Most of the organisms that were reported as negative were shown either to have had no established relation to the outbreak or t o have been tested by methods other than those specified. The more recent literature shows a similar high proportion of positive reactions to these tests, Chapman (1947a). I n a series of studies in which the Stone reaction was applied directly to an improved isolation medium [Chapman (1946a) and Chapman and Domingo (1946) ] all strains incriminated in local outbreaks showed considerable zoning in addition to producing pigment, coagulating blood, and 100

Influence of raw milk microflora on the characteristics of Swiss-type cheeses. / Evolution of microflora during ripening and characterization of facultatively heterofermentative lactobacilli

“…Ali the measures were made in duplicate. To differentiate the microflora, the following media were used: -mesophilic aerobic microflora: plate count agar (PCA, Difco); aerobic incubation at 30 oC for 3 days (AFNOR V08-011, 1978); -enterocococci: kanamycin esculin agar (KEA, Merck); aerobic incubation at 37 "C for 2 days (Isenberg et al, 1970); -Micrococcaceae: mannitol salt agar (MSA, Difco); aerobic incubation at 30 "C for 3 days (Chapman, 1948); -coliforms: violet red bile agar (VRBA, Difco); aerobic incubation at 30 "C for 24 h (AFNOR V08-054,1993); -yeasts: glucose chloramphenicol agar; aerobic incubation at 25 -c for 3 days (FIUIDF 94B, 1991); -propionibacteria: sodium lactate agar and cloxacillin (SlAC); anaerobie incubation at 30 "C du ring 6 days (Drinan and Cogan, 1992); -spores of butyric acid bacteria: Bryant-Burkey broth modified by Bergère (Biokar); anaerobic incubation at 37 "C du ring 7 days; spores of butyric acid bacteria were counted in tubes according to the most probable number method (CNERNA,1987); -thermophilic streptococci: medium 17 (M17); aerobic incubation at 42 "C for 3 days (Terzaghi and Sandine, 1975); -thermophilic lactobacilli: de Man, Rogosa, Sharpe (MRS, Difco); anaerobic incubation at 42 oC for 3 days (de Man et al, 1960); -facultatively heterofermentative lactobacilli: Facultativ Heterofermen-tativen laktobazillen or FH agar (Isolini et al, 1990); anaerobie incubation at 38 oC during 3 days. To increase the selectivity of the medium, nalidixic acid was added (40 mg/Llo…”

Studies With Staphylococcal Toxins: I. A Reappraisal of the Validity of the "Kitten Test" as an Indication of Staphylococcal Enterotoxin

“…On the other hand, the conclusion of Dolman and Wilson (7) and Dolman (6) that no relation exists between the a-lysin or P-lysin and enterotoxin has been upheld by a number of other investigators whose work is discussed by Surgalla and Hite (24). Nevertheless, reviews of the evidence relative to the validity and significance of the kitten test all reveal conflict of opinion and uncertainty (2,3,4,5,12,13,17,26).…”

THE OCCURRENCE AND GROWTH OF STAPHYLOCOCCI ON PACKED BACON, WITH SPECIAL REFERENCE TO STAPHYLOCOCCUS AUREUS

“…When this work was done four selective media were in common use: mannitol-salt agar (Chapman, 1945), staphylococcus medium no. 110 (Chapman, 1946), Chapman-Stone medium (Chapman, 1948), and tellurite-glycine agar (Zebowitz, Evans & Niven, 1955) or modifications of it. The first three media depend largely for their selectivity on the ability of pathogenic staphylococci to grow in the presence of 7.5% of NaCl (Koch, 1942), or of 5.5% of NaCl plus 7.5% of ammonium sulphate, and to ferment mannitol: but salt is clearly of no value in the detection of pathogenic staphylococci when they are mixed with much larger numbers of salt tolerant bacon micrococci.…”