EFFECTS OF CARBOHYDRATES, PROTEINS, AND BACTERIAL CELLS IN THE HEATING MEDIA ON THE HEAT RESISTANCE OF CLOSTRIDIUM SPOROGENES
It is well known that the heat resistance of bacterial spores is influenced markedly by the nature of the medium in which the spores are heated. This fact is an important problem relating to the practical sterilization in bacteriology and in the food industry. Hence voluminous data on the heat resistance of Clostridium botulinum and Clostridium porogenes in various kinds of foods or food juices have been published (Townsend et al., 1938; Reed et al., 1951; Reynolds et al., 1952). From these data, it can be easily pointed out that the resistance value of a strain in a food is larger than that in phosphate buffer, whereas in another food the resistance value of the same strain is smaller than that in neutral phosphate buffer. Although the pH of the heating media has a marked influence on the thermal death rate of bacteria, it appears that the cause of such a difference in resistance values of a strain cannot be attributed wholly to the variation of pH values of the foods (Sognefest et al., 1948). In fact, there are evidences that some of the ingredients of food might exert a protective effect or a death accelerating effect for the organism during the heating. Weiss (1921) reported that the longer survival time was obtained when the spores of C. botulinum were suspended and heated in the foods with the higher sugar concentration. The similar protective effect of sugars on the bacterial spores has been demonstrated by Anderson et al. (1949) and Sugiyama (1951). Murray and Headlee (1931) found that the presence of peptone in the heating medium had shown sometimes a protective effect for the spores of C. tetani. Recently, Kawai and Tanaka (1952) have shown that several kinds of higher molecular substances, such as gelatin, starch, gum arabic, and alginic acid, have the protective effects for the spores of Bacillus mesentericus and Bacillus brevis. The test organisms used by these workers are relatively less resistant than the most resistant food spoilage bacteria, and the kinds of the substances tested on each strain are rather limited. Thus it seemed important to study the effects of various substances on the most resistant strain. Using the spores of Cameron's putrefactive anaerobe 3679 (Clostridium sporogenes, ATCC 7955), the effects of various carbohydrates, proteins, and bacterial cells were studied. In the previous papers Amaha (1952a,b, 1953) has clearly indicated that the thermal death time of spores of certain strains is influenced markedly by the nature of the recovery media. In general the more favorable was the nature of a medium for the development of heated spores, the longer was the survival time. Hence, it should be considered that the substances added in the basal heating medium have the two stages in their action to the spores; the first, during the heating time, and the second, after the substances were transferred in the subculture medium. In this paper an attempt was made to distinguish the two effects, i.e., the first effect, a true protection, and the second effect, a false protection, of each of substances tested.
Quantitative analysis of residual protein contamination of podiatry instruments reprocessed through local and central decontamination units
BackgroundThe cleaning stage of the instrument decontamination process has come under increased scrutiny due to the increasing complexity of surgical instruments and the adverse affects of residual protein contamination on surgical instruments. Instruments used in the podiatry field have a complex surface topography and are exposed to a wide range of biological contamination. Currently, podiatry instruments are reprocessed locally within surgeries while national strategies are favouring a move toward reprocessing in central facilities. The aim of this study was to determine the efficacy of local and central reprocessing on podiatry instruments by measuring residual protein contamination of instruments reprocessed by both methods.MethodsThe residual protein of 189 instruments reprocessed centrally and 189 instruments reprocessed locally was determined using a fluorescent assay based on the reaction of proteins with o-phthaldialdehyde/sodium 2-mercaptoethanesulfonate.ResultsResidual protein was detected on 72% (n = 136) of instruments reprocessed centrally and 90% (n = 170) of instruments reprocessed locally. Significantly less protein (p < 0.001) was recovered from instruments reprocessed centrally (median 20.62 μg, range 0 - 5705 μg) than local reprocessing (median 111.9 μg, range 0 - 6344 μg).ConclusionsOverall, the results show the superiority of central reprocessing for complex podiatry instruments when protein contamination is considered, though no significant difference was found in residual protein between local decontamination unit and central decontamination unit processes for Blacks files. Further research is needed to undertake qualitative identification of protein contamination to identify any cross contamination risks and a standard for acceptable residual protein contamination applicable to different instruments and specialities should be considered as a matter of urgency.
Genetics of the phenotypic evolution in sheep: a molecular look at diversity-driving genes
Background After domestication, the evolution of phenotypically-varied sheep breeds has generated rich biodiversity. This wide phenotypic variation arises as a result of hidden genomic changes that range from a single nucleotide to several thousands of nucleotides. Thus, it is of interest and significance to reveal and understand the genomic changes underlying the phenotypic variation of sheep breeds in order to drive selection towards economically important traits. Review Various traits contribute to the emergence of variation in sheep phenotypic characteristics, including coat color, horns, tail, wool, ears, udder, vertebrae, among others. The genes that determine most of these phenotypic traits have been investigated, which has generated knowledge regarding the genetic determinism of several agriculturally-relevant traits in sheep. In this review, we discuss the genomic knowledge that has emerged in the past few decades regarding the phenotypic traits in sheep, and our ultimate aim is to encourage its practical application in sheep breeding. In addition, in order to expand the current understanding of the sheep genome, we shed light on research gaps that require further investigation. Conclusions Although significant research efforts have been conducted in the past few decades, several aspects of the sheep genome remain unexplored. For the full utilization of the current knowledge of the sheep genome, a wide practical application is still required in order to boost sheep productive performance and contribute to the generation of improved sheep breeds. The accumulated knowledge on the sheep genome will help advance and strengthen sheep breeding programs to face future challenges in the sector, such as climate change, global human population growth, and the increasing demand for products of animal origin.