Conditions affecting growth and enterotoxin production by Staphylococcus aureus on temperature-abused chicken meat

Growth of Staphylococcus aureus at 15°C, with and without addition of representative spoilage bacteria, was studied in cooked, whole chicken meat and chicken broth. In the absence of competitors, the organism grew better in broth culture than on whole meat, but multiplied more slowly in broth when other organisms were present, even from twice the previous level of inoculum. The presence of competitors had no marked effect on the growth of Staph. aureus on whole meat. Enterotoxin A was not produced at 15°C on either whole meat or in broth, and occurred at 20°C only in pure culture. At 30° and 37°C, toxin was produced whether or not competitors were present. Toxin production by Staph. aureus appeared to be influenced more by growth temperature than by bacterial competition.     

Listeria contamination at a poultry processing plant

Escherichia coli grown in broth initially at pH 5.0 (pH 5.0-grown organisms) survived exposure to inorganic acid or to acid pH plus organic acid which prevented subsequent growth by pH 7.0-grown organisms. This resistance of pH 5.0-grown organisms to organic acids was observed at acid pH with lactic, propionic, benzoic, sorbic, trans-cinnamic and acetic acids. Such resistance might allow acid-habituated organisms to survive in acid foods or at body sites such as the urinary tract where organic acids are present at acid pH.     

Steroid metabolism in corpora lutea of the western spotted skunk (Spilogale putorius latifrons)

The present study reports steroid metabolism by corpora lutea (CL) obtained from skunks with diapausing embryos ('delay' CL) and with activated embryos (activated CL). CL from both reproductive periods were incubated with various radioactive precursors. Control incubations without any tissue or with 50 microliter of packed skunk blood cells were also conducted simultaneously. Incubation of skunk CL with [3H]-pregnenolone for 3 h resulted in 36% of the precursor accumulating as progesterone. Metabolism of [3H]dehydroepiandrosterone (DHEA) to androstenedione proceeded with approximately the same amount of product accumulating (34-46%) as was observed in the conversion of pregnenolone to progesterone. These results suggest that delta 5 isomerase, 3 beta-hydroxysteroid dehydrogenase, is the most prominent enzyme in skunk CL. Metabolism of [3H]pregnenolone to 17 alpha-hydroxypregnenolone and [3H]progesterone to 17 alpha-hydroxyprogesterone occurred at low rates (1-7%), suggesting the presence of C21 steroid 17 alpha-hydroxylase in skunk CL. Aromatase activity, as estimated by measuring accumulation of oestradiol-17 beta from [3H]testosterone, was demonstrated in activated CL. These results suggest that skunk CL appear to metabolize steroids in a manner similar to CL of other mustelids such as the ferret and American badger.     

Developmental changes in Hymenolepis citelli and Hymenolepis diminuta during patency

Stem cell frequency, wet weight, proglottid number, and egg production were measured in Hymenolepis citelli at specific intervals between 20 and 120 days postinfection in an effort to correlate changes in stem cell frequency to other developmental parameters. Considerable variability was seen in wet weight and proglottid number, but differences did not seem to reflect any relation between these parameters and stem cell frequency. Significant differences were observed in egg production at specific postinfection periods. These appeared to correspond to changes seen in stem cell frequency during patency. Similar changes in egg production which also correspond to measured changes in stem cell frequency were recorded for Hymenolepis diminuta. Differences were also seen in number of eggs contained within gravid proglottids at various times postinfection for both species.     

Improvement of Disease Prediction and Modeling through the Use of Meteorological Ensembles: Human Plague in Uganda

Climate and weather influence the occurrence, distribution, and incidence of infectious diseases, particularly those caused by vector-borne or zoonotic pathogens. Thus, models based on meteorological data have helped predict when and where human cases are most likely to occur. Such knowledge aids in targeting limited prevention and control resources and may ultimately reduce the burden of diseases. Paradoxically, localities where such models could yield the greatest benefits, such as tropical regions where morbidity and mortality caused by vector-borne diseases is greatest, often lack high-quality in situ local meteorological data. Satellite- and model-based gridded climate datasets can be used to approximate local meteorological conditions in data-sparse regions, however their accuracy varies. Here we investigate how the selection of a particular dataset can influence the outcomes of disease forecasting models. Our model system focuses on plague (Yersinia pestis infection) in the West Nile region of Uganda. The majority of recent human cases have been reported from East Africa and Madagascar, where meteorological observations are sparse and topography yields complex weather patterns. Using an ensemble of meteorological datasets and model-averaging techniques we find that the number of suspected cases in the West Nile region was negatively associated with dry season rainfall (December-February) and positively with rainfall prior to the plague season. We demonstrate that ensembles of available meteorological datasets can be used to quantify climatic uncertainty and minimize its impacts on infectious disease models. These methods are particularly valuable in regions with sparse observational networks and high morbidity and mortality from vector-borne diseases.     

Action of the diaphragm on the rib cage inferred from a force-balance analysis

Displacements of the rib cage are determined by the intrinsic passive properties of the rib cage, rib cage musculature, pleural and abdominal pressures, and the diaphragm. The diaphragm's mechanical actions on the rib cage are inferred from a force-balance analysis in which the diaphragm is seen to cause expansion of the rib cage by pulling cephalad at its insertions on the lower ribs (insertional component) and by raising intra-abdominal pressure, which pushes outward on the diaphragm's zone of apposition to the rib cage (appositional component). Goldman and Mead suggested that the diaphragm, acting alone, could drive both the rib cage and abdomen on their passive characteristics. The force-balance analysis shows that the diaphragm's inspiratory action on the rib cage is less than predicted by Goldman and Mead, but that in the special circumstances of their experiment (low lung volumes), the appositional component is large and the rib cage can be driven close to its passive characteristics. The force-balance analysis is consistent with recent observations by other investigations and is incompatible with the model proposed by Macklem and colleagues and with the Goldman-Mead hypothesis. Experiments on three subjects produced data consistent with the force-balance analysis, showing that the inspiratory action of the diaphragm on the rib cage is greatest at low lung volumes.     

Stability of unsaturated methyl esters of fatty acids on surfaces

The stability of unsaturated methyl esters is greater when they are adsorbed on silica gel than when a glass surface is used. Storage of small samples adsorbed on silica gel may be a convenient addition to conventional methods of protecting labile fats against autoxidation.