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Biomedical subjects

M Hinton

Publications and source records attributed to M Hinton.

At least 37 records · Page 2Linked to original sources
PubMed1991

Short-chain organic acids at ph 5.0 kill Escherichia coli and Salmonella spp. without causing membrane perturbation.

When strains of Escherichia coli K12 and Salmonella spp. were incubated with 0.5-0.7 mol/l formic or propionic acid at pH 5.0, propionic acid was more active than formic acid. It killed 90% of the cell population within 60 min compared with over 3 h for formic acid. Cell death was not associated with a reduction in culture turbidity or a loss of membrane integrity since morphologically normal membranes were observed by electron microscopy and only a small proportion of the cytoplasmic enzyme beta-galactosidase leaked into the supernatant fluid of acid-treated E. coli K12 cultures.

Cell Membrane↗
PubMed1990

Disease conditions diagnosed in culled adult cattle sent to an abattoir either with or without a veterinary certificate.

Lesions were detected in 208 culled cattle examined at a slaughterhouse. Eighty-two of them had a veterinary certificate, and 30 of these had been slaughtered on the farm. The principal diagnoses included lameness (88 cases), mastitis (35), chronic infections (32), complications of parturition (20) and fractures and dislocation (14). Most of the 126 animals sent for slaughter by farmers without a veterinary certificate were suffering from lameness (71), mastitis (29) or chronic infections (18). Over 90 per cent of the animals with complications of parturition or traumatic injury had a veterinary certificate. The carcases of 33 (26 per cent) of the animals sent for slaughter without a veterinary certificate were rejected by the meat inspector, and 29 (35 per cent) of those with a veterinary certificate were rejected; the difference was not statistically significant.

Abattoirs↗
PubMed1990

Effect of short-chain organic acids on macromolecular synthesis in Escherichia coli.

Incubating cultures of Escherichia coli with propionic acid (5 mmol/l) or formic acid (10 mmol/l) at pH 5.0 produced bacteriostasis lasting 30 and 120 min respectively. During this time rates of RNA, DNA, protein, lipid and cell wall synthesis were reduced. Growth resumed after continued incubation in the presence of acid, but cells from acid-treated cultures were larger than controls. DNA synthesis was particularly sensitive to the presence of the propionic or formic acid.

Bacterial Proteins↗
PubMed1990

The survival of streptococci and enterococci in animal feed and on straw with particular reference to Streptococcus uberis.

The survival of Streptococcus uberis, Strep. bovis, Enterococcus faecalis spp. faecalis and Ent. faecium in animal feed and on wheat straw was studied for one month. Streptococcus bovis survived the best in feed and Strep. uberis the worst while on straw Ent. faecium was the most resilient species and there was little to choose between the other three. The recovery of all species, excepting Strep. bovis, on selective and non-selective agar was comparable. The growth of Strep. bovis, on the other hand, was inhibited on both Edward's medium and inulin agar.

Animal Feed↗
PubMed1990

The invasiveness of different strains of Salmonella enteritidis phage type 4 for young chickens.

Five strains of Salmonella enteritidis phage type 4 (PT4) isolated in 1978, 1984 and 1988 were examined for their ability to colonise the caecum and invade the liver of day-old chickens. All strains were capable of caecal colonisation and there were no differences in their colonisation ability in this respect. In contrast there was a gradation in the ability of strains to invade the liver, with strains isolated in 1988 proving the most invasive. Absence of a 38 megadalton (Md) plasmid, which has been shown to be involved in the virulence of S. enteritidis PT4 for BALBc mice, had little effect on the ability of strains of this phage type to colonise the caecum or invade the liver of day-old chickens. These results suggest that recent isolates of PT4 may have enhanced virulence for chickens which is not necessarily associated with the carriage of a 38 Md plasmid.

Animals↗
PubMed1989

Microdialysis measurement of monoamine and amino acid release from the medial preoptic region of the sheep in response to heat exposure.

Concentrations of monoamines and metabolites and amino acids were measured in microdialysis samples taken from the medial preoptic area of 5 conscious sheep before, during and after exposure to an ambient temperature of 45 degrees C. Concentrations of dopamine, noradrenaline and aspartate significantly increased, and those of the serotonin metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA), significantly decreased during heat exposure and although panting was induced, body temperature did not change. Concentrations of noradrenaline and aspartate declined and 5-HIAA increased to preheat exposure levels during the 60 min after the ambient temperature was reduced but levels of dopamine and its metabolite, homovanillic acid, remained elevated. Dopamine, noradrenaline, 5-HIAA and aspartate concentrations were not significantly altered by isolation stress and did not show significant changes in the cortex following heat exposure. These experiments provide further support for the proposed roles of dopamine, noradrenaline, serotonin and aspartate in the neural control of autonomic thermoregulatory responses.

Amino Acids↗
PubMed1988

Aerosol infection of calves and mice with Salmonella typhimurium.

The likelihood of airborne spread and infection by Salmonella typhimurium was studied in calves and mice. S typhimurium survived in air sufficiently long to present a significant hazard of airborne spread. In a dry climate (32 per cent relative humidity) its predicted viability five minutes after aerosolization was 4 per cent relative to its initial value. This increased to 24.8 per cent in a humid atmosphere (72 per cent relative humidity). Inhalation of S typhimurium by mice caused disease and death at times dependent upon the dose. Even the lowest dose of about 150 colony forming units (cfu) produced disease. Inoculation of approximately 10(4) to 10(6) cfu S typhimurium by either 'mouth and nose only' or 'whole body' aerosol exposure caused infection in calves. The consequences for the control of salmonellosis in intensive calf husbandry are discussed in the light of this demonstration that airborne transmission can be a primary mode of infection of S typhimurium.

Aerosols↗
PubMed1988

Control of salmonella infections in broiler chickens by the acid treatment of their feed.

In three experiments a solution of formic acid (Bioadd) was added to feed 'naturally' contaminated with salmonellas. In two of them no salmonella infections were demonstrated in broiler chickens given feed containing 0.6 per cent (w/w) of the formic acid solution for seven weeks and in the third the infection rate was reduced considerably. In four other experiments the feed was contaminated artificially with between 1 and 47 Salmonella kedougou/g and a second product (BPO12), consisting of a mixture of formic acid and propionic acid, was evaluated. When it was added at 0.5 to 0.68 per cent (w/w) only one of 30 groups of 10 to 12 birds became infected with S kedougou by two weeks of age, compared with 22 of 27 control groups. The treatment of the feed with BPO12 one week before the addition of the salmonellas prevented the establishment of infection in chicks given the treated feed, indicating that acid treatment will provide protection against subsequent recontamination of the feed with the organisms. The isolation rate of S kedougou from artificially contaminated feed treated with BPO12 was reduced only slightly but the feed was apparently 'safe' for the birds which consumed it.

Animal Feed↗
PubMed1988

Salmonella infection in chicks following the consumption of artificially contaminated feed.

Poultry feed was contaminated artificially with either Salmonella kedougou or S. livingstone using a two-stage mixing process. Intestinal infection became established in a small proportion of birds when feed containing between 0.1 and 0.3 salmonellas/g was given continuously for 2 or 3 weeks from the day of their purchase as 'day-olds' while nearly all birds became infected when the feed contained 100-300 salmonellas/g. Between these limits a dose response was demonstrated in that the proportion of birds becoming colonized with salmonellas increased as the numbers of salmonellas added to feed was increased. Nalidixic acid-resistant strains of both serotypes were used to facilitate the recovery of organisms. The isolation rate was higher from dilutions of caecal contents inoculated directly onto brilliant green agar supplemented with nalidixic acid than it was from swabs of cloacal faeces, even when an enrichment technique was used. This observation confirms that the incidence of salmonella carriage in flocks will be under-estimated if only cloacal faeces are cultured. Of the two serotypes used S. kedougou proved the more efficient colonizer although for both serotypes variation in infection rates was demonstrated in different groups of birds given feed containing comparable numbers of salmonellas.

Animal Feed↗
PubMed1988

The effect of growth-promoting antibiotics on the faecal enterococci of healthy young chickens.

Small groups of chickens were given feed containing either avoparcin, nitrovin, virginiamycin or zinc bacitracin from the day of their purchase as day-olds. Differences between the birds receiving growth promoters and the untreated controls were observed during the last third of the 23 d survey period. The enterococcal population of the 'dosed' birds contained a greater proportion of Enterococcus faecium than did that of the control birds while the converse was true for Ent. gallinarum. This apparent selection of Ent. faecium by the growth-promoting antibiotics had an influence on the incidence of resistance to therapeutic antibiotics among the enterococcal population as a whole. This was because this species was generally more resistant than Ent. gallinarum to cephalothin, the MLS antibiotics (erythromycin, lincomycin and tylosin) and tetracycline.

Animal Feed↗
PubMed1988

Salmonella colonization in young chickens given feed supplemented with the growth promoting antibiotic avilamycin.

The feed given to young broiler chickens was contaminated artificially with Salmonella kedougou, a serotype associated with both subclinical infections in commercially reared chickens and food poisoning in humans. No evidence was obtained to suggest that the growth promoting antibiotic avilamycin, added to the feed at the rate of either 2.5 ppm or 10 ppm, had the undesirable side-effect of favouring the colonization of the intestinal tract of the birds with Salmonella kedougou when they were challenged with this organism in the feed.

Animal Nutritional Physiological Phenomena↗
PubMed1987

Epidemiology of Salmonella typhimurium infection in calves: excretion of S typhimurium in the faeces of calves in different management systems.

Twenty-five batches of market-purchased calves, comprising 589 animals on 11 farms, were examined for the excretion of salmonellas for at least 28 days after their arrival. Salmonellas were found in 217 (51 per cent) of 423 calves from 18 of 21 batches on nine farms. The calves were housed in single pens on eight farms and in groups on the others. The trends in new excreters and the proportion of Salmonella typhimurium excreters were similar in both types of housing, a peak of excretion which was slightly higher in single penned calves, being reached 18 to 19 days after arrival. New excreters were found at most samplings in both types of housing, but the peak of new excreters appeared earlier and declined sooner in single penned calves. On average, single penned animals excreted salmonellas longer. Salmonella dublin was found only in single-penned calves, and the trend in excretion was similar to that for S typhimurium in single-penned calves except that the peak was at about 28 days. Prophylactic feeding of antibiotics was practised on nine farms, but appeared to have no influence on the excretion of salmonellas. Salmonellas were isolated from the environment in six of nine farms studied, even after cleaning and disinfection. It is suggested that the persistence of salmonellas in the environment deserves more attention in the formulation of control programmes.

Animals↗
PubMed1987

The effect of ampicillin and tylosin on the faecal enterococci of healthy young chickens.

Enterococcal isolates from young chickens were differentiated into one of three species, namely Enterococcus faecalis, Ent. faecium and Ent. gallinarum. The proportion of each species among the enterococcal population changed with time in birds not dosed with antibiotics. This pattern of change was modified in birds dosed with either tylosin or ampicillin even though ampicillin did not select for ampicillin resistance among the enterococcal population. A gradual increase in tylosin resistance was recorded with time among the enterococci of the 'undosed' control birds. This was associated with an increase in the proportion of Ent. faecium, a species commonly resistant to tylosin, among the enterococci of the birds as they grew older.

Ampicillin↗
PubMed1987

Influence of continuous challenge via the feed on competitive exclusion of salmonellas from broiler chicks.

In three replicate trials, chicks were treated orally with a culture of caecal contents from an adult hen and then exposed to continuous challenge from a strain of Salmonella kedougou incorporated in feed at a level of ca 10(2)/g. The contaminated feed was introduced at intervals from 0 to 48 h after treatment. Under these conditions, only one of 119 chicks in 12 separate groups was salmonella-positive at 7 d, compared with 36 of 119 controls, but thereafter protection was less consistent and in some cases the subsequent incidence of infected birds increased during the 3-week rearing period. At 21 d, 14 of 60 treated chicks were positive and 32 of 59 controls. Protection was more evident in chicks challenged 24 or 48 h after treatment than in those groups which received the salmonella-contaminated feed at 0 or 5 h and even untreated, control chicks showed greater resistance to salmonella infection from 24 h onwards. In some control and treated groups containing salmonella-positive birds, contamination of the litter reached ca 10(6) salmonellas/g, thus providing a considerable secondary challenge. Introduction of salmonellas via contaminated feed probably reduces the efficacy of protective treatment under field conditions and helps to explain the more limited success in commercial use.

Animal Feed↗
PubMed1986

The influence of dietary protein and antimicrobial feed additives on salmonella carriage by broiler chickens.

Salmonella carriage in broiler chickens was not apparently influenced by the protein concentration of the ration, pelleting or by the coccidiostat monensin. The inclusion of penicillin in the diet was associated with an increase in salmonella shedding, particularly in the first half of the rearing period, but did not influence the lactobacillary count in the crop or the pH of the contents of the crop, gizzard and caecum. Furazolidone medication (150 mg/kg food) for the first 10 days had no effect on salmonella carriage at the time of slaughter (seven weeks) and studies into the influence of growth promoting antibiotics (avoparcin, bacitracin and virginiamycin) on salmonella shedding were inconclusive. Circumstantial evidence indicated that the food was the most probable source of infection for the birds studied in these experiments.

Animals↗