Action of Visking Sausage‐casing Material on Bacterial Growth

Abstract

About a year ago I had occasion to investigate an outbreak of carbonmonoxide poisoning which was, in my opinion, erroneously attributed to the eating of cervelat summer sausages, Hall (1939). This investigation led to a study of the remarkable resistance of these sausages to spoilage; they will not spoil either at room temperature or at 37"C.(98.6"F.) in many weeks. Bacillus botulinus fails to grow and produce its toxin in them even when considerable numbers of viable spores are inoculated in several places and the sausages are incubated at 37°C. for as long as eight weeks. They spoil within a few hours, however, if placed in water at 37°C. and if inoculated with B. botulinus and placed in water at 37OC., strong toxin is produced within a few days, Hall (1940).Summer sausages are covered with a patented casing called "Visking" which resembles cellophane in appearance. This material protects the sausages against contamination but not against evaporation. Although cervelat summer sausages apparently keep just as well when the casings are stripped off, the question was raised whether the casings play any important role in excluding air, thus favoring the growth of anaerobic bacteria, such as B. botulinus. Knowing that the casings are pervious to moisture, the writer believed that they were also pervious to air and that anaerobic bacteria would not grow in the sausages immediately under the casing material. It was decided to test this hypothesis in plates of peptone agar protected with squares of Visking sausage casing in comparison with thin glass covers in a series of experiments similar to those of Sanfelice (1893) and Braatz (1895).Robert Koch is said to have been the first to cultivate anaerobic bacteria on slabs of agar medium covered with thin pieces of sterile mica, but I have been unable to find an accurate reference to Koch's work. Sanfelice in 1893 cultivated anaerobes in agar between pieces of glass, while Braatz in 1895 showed that obligately aerobic bacteria were inhibited by thin slips of broken glass laid on agar plates. Trenkmann (1898) cultivated Bacillus tetalti, Bacillus chazcvoei, and the "bacillus of malignant oedema" in gelatin and agar media between watch glasses, while Streng (1903) used nested glass dishes of a special type for several anaerobes. Then Liefmann (1908) showed that methylene-blue remained decolorized in agar plates covered with thin pieces of glass and that B. tetani, B. botulinus, and other anaerobic bacilli could readily be grown

BOTULINUM TOXIN FORMATION IN LIVER SAUSAGEa

“…Little work dealing with the effect of plastic casings on growth of obligate anaerobes has been reported. Hall ( 4 ) showed that these organisms would not grow on the surface of agar covered with "Visking" film," ,but this does not necessarily mean that they would fail to grow within a mass of sausage cased in Visking. The low permeability of Sarana indicates that this plastic film might permit growth of obligate anaerobes.…”