Biomedical subjects

O M Weinack

Publications and source records attributed to O M Weinack.

At least 19 recordsLinked to original sources

PubMedDate not supplied

Protecting chicks and poults from Salmonellae by oral administration of "normal" gut microflora.

Resistance of young chicks and poults to salmonella exposure was substantially increased by early oral administration of intestinal contents or feces from selected adult chickens. Protection was secured also by administering anaerobic broth cultures of intestinal microflora from selected donor birds. Protection, was substantial for 63 days, the longest period tested, although it could be overcome by severe exposure. The protective mechanism appears to be a consequence of competitive exclusion of salmonella by "normal" microflora of the gastrointestinal tract.

Administration, Oral↗

PubMedDate not supplied

Evaluation of several methods of detecting salmonellae in groups of chickens.

Chickens exposed experimentally to Salmonella agona, S. blockley, S. enteritidis, S. infantis, and S. typhimurium were tested serologically by microagglutination and microantiglobulin procedures and culturally by cloacal swabs and environmental samples. Chicks infected at one day old yielded the highest level of positive cloacal swab cultures, whereas exposure of older birds gave maximal serologic titers. Recovery of salmonella from environmental samples is dependent on a number of factors, including excretion rate by the population and survival rate of salmonellae in the environment. Serologic titers persisted after salmonellae could no longer be isolated from cloacal swabs or environmental samples. The possibility of false-positive serologic reactions was explored in two groups of chickens, one exposed to other Enterobacteriaceae, and one composed of eight specific-pathogen-free flocks. Occasional serologic microantiglobulin titers were observed only in the latter group. Extensive culturing of the environment from these flocks had negative results.

Agglutination Tests↗

PubMedDate not supplied

Large-scale trials to study competitive exclusion of salmonella in chickens.

Competitive exclusion of salmonella by native gut microflora was studied in 24 groups of 100 chickens each started in thoroughly cleaned and sanitized isolation facilities. During 53-day test periods, infection by both Salmonella infantis and S. typhimurium was greatly restricted in groups previously treated with native microflora compared with control groups. Feed and water starvation for 48 hours starting at either 23 or 51 days did not affect the incidence of infection in protected groups. The protective flora spread readily to adjacent untreated groups; infected groups given the protective flora at 11 days exhibited a more rapid elimination of infection than untreated control groups.

Animals↗

PubMedDate not supplied

Influence of temperature, social, and dietary stress on development and stability of protective microflora in chickens against S. typhimurium.

In the day-old chick, physiological stress in the form of high or low temperatures or feed and water deprivation either interfered with colonization or altered the protection provided by normal intestinal microflora against subsequent challenge with Salmonella typhimurium. The response was more obvious after individual exposure of chicks to salmonella than after exposure to infected seeders. Physiological and dietary stress at 2 weeks of age did not appreciably alter the S. typhimurium excretion pattern in treated chicks. The protective microflora appears to be quite stable under these stress conditions.

Animals↗

PubMedDate not supplied

Therapeutic trials with native intestinal microflora for Salmonella typhimurium infections in chickens.

Chicks infected with Salmonella typhimurium at 1 day of age were treated with normal intestinal flora starting 3 or 9 days later. Chicks were reared on the floor in isolated pens with wood shavings for litter. Cloacal-swab cultures were the main criteria for determining S. typhimurium infection. A single treatment reduced the infection period, but multiple treatments hastened the process considerably: after 6-8 weeks, birds given multiple treatments yielded sporadic or no isolations of S. typhimurium. It appears that litter from birds colonized by a protective microflora may serve as a vehicle for transmitting the flora to succeeding groups of birds.

Animals↗

PubMedDate not supplied

Further studies on competitive exclusion of Salmonella typhimurium by lactobacilli in chickens.

Competitive exclusion of Salmonella typhimurium by isolates of lactobacilli was studied in day-old chicks. Protection was evaluated by enumerating salmonella in feces and cloacal swab cultures from test chickens. Neither single nor multiple treatment with six morphologically distinct isolates of lactobacilli resulted in major protection against infection by S. typhimurium.

Animals↗

PubMedDate not supplied

A supplemental test system to measure competitive exclusion of Salmonellae by native microflora in the chicken gut.

An improved individual challenge test system is described for evaluation of competititve exclusion of salmonellae in day-old chicks by native gut microflora. Evaluation of salmonella protection is based on culture of cloacal and fecal samples by enrichment methods plus enumeration of salmonellae in fresh droppings collected from test groups. The use of a nalidixic-acid-resistant strain of salmonella allowed for ease of measurement. Comparative data are included that were developed by parallel tests by the seeder bird and this individual challenge test system on salmonella protection provided by microflora from a specific-pathogen-free population and from intestinal microflora propagated anaerobically in several media. The individual-bird challenge test system appeared to yield a more precise measurement of protection than the seeder-bird system and indicated that trypticase soy broth is as effective as VL broth for anaerobic culture of the protective microflora. Fresh fecal suspensions were somewhat more dependable than anaerobic cultures in providing a high level of protection against subsequent salmonella infection.

Animals↗

PubMedDate not supplied

Further studies on competitive exclusion for controlling Salmonellae in chickens.

A native intestinal microflora of chickens which is protective against salmonella readily transferred to penmates and apparently to birds in adjacent pens. The microflora not only minimized infection resulting from exposure following colonization of the gut with microflora, but significantly abbreviated the period of infection when introduced after a salmonella infection was established in chicks. A microflora with undiminished protective activity, sensitive to only a few commonly used antibacterials, was established in a SPF-Cofal/Marek-negative population. Intestinal microflora from mourning doves was at least partially effective in protecting chicks against a naladixic-acid-resistant strain of Salmonella infantis. In limited tests with 2 of 3 sources of protective microflora, the growth rate of chicks in the absence of salmonellae was significantly improved. A hypothesis involving specificity of attachment between the glycocalyces of the protective microflora and of the intestinal mucosa is offered as the likely mechanism of protection.

Animal Feed↗

PubMedDate not supplied

Influence of Mycoplasma gallisepticum, infectious bronchitis, and cyclophosphamide on chickens protected by native intestinal microflora against Salmonella typhimurium or Escherichia coli.

Chickens that have considerable resistance to Salmonella typhimurium or Escherichia coli infection by early development of a native intestinal microflora shed these bacteria following aerosol exposure to Mycoplasma gallisepticum and/or infectious bronchitis virus. Administration of cyclophosphamide to similarly treated chickens induced slight shedding of these bacteria, and the combination of cyclophosphamide and respiratory agents magnified the shedding rate. These agents also influenced the isolation rate of E. coli and S. typhimurium from the trachea and air sacs.

Air Sacs↗

PubMedDate not supplied

Strain of Mycoplasma synoviae of low transmissibility.

An infection with Mycoplasma synoviae that spread slowly within and among pens of chickens was observed in a brown-egg breeding population that had long been free of M. gallisepticum and M. synoviae. There were unusually long periods of time between the first serological evidence of infection in a pen of chickens and the time that most of the group became positive. Transmission to adjacent pens was also slow.

Agglutination Tests↗

PubMedDate not supplied

Comparative studies on competitive exclusion of three isolates of Campylobacter fetus subsp. jejuni in chickens by native gut microflora.

Resistance of young chicks to Campylobacter fetus subsp. jejuni was substantially increased by early exposure to native gut microflora. Protection was demonstrated against two human isolates and a chicken isolate of C. fetus subsp. jejuni. Significant protection against the chicken isolate was observed throughout a 91-day test period. Infection reached 100% (25/25) in the untreated group at 56 days of age and only 4% (1/25) in the group treated with native gut microflora. Campylobacter fetus subsp. jejuni was isolated from the ceca and less frequently from the gall bladder and liver of chicks that actively shed the bacteria. Cultures of feces from chicks reared on wood-shavings litter were often negative, suggesting that culturing litter as an indicator of infection has limited value.

Animals↗

PubMedDate not supplied

Establishment and competitive exclusion of Yersinia enterocolitica in the gut of monoxenic and holoxenic chicks.

Newly hatched chicks subcutaneously injected with or orally exposed to Yersinia enterocolitica were colonized in the gastrointestinal tract by this bacteria. Colonization did not take place when chicks were exposed to less than 10(8) colony-forming units. In monoxenic chicks, major colonization was detected in the crop, ceca, and cloaca; fewer numbers colonized other regions of the gastrointestinal tract, and there was little evidence of bacteremia. None of the chicks exhibited clinical signs, although colonization was demonstrated throughout the gastrointestinal tract over the 28-day test period. Prior colonization by native gut microflora prevented subsequent colonization by Y. enterocolitica in holoxenic chicks.

Animals↗

PubMedDate not supplied

Gastrointestinal colonization by salmonellae and pathogenic Escherichia coli in monoxenic and holoxenic chicks and poults.

Chicks monocolonized by either salmonellae or pathogenic strains of Escherichia coli had persistent and undiminished colonization of all levels of the gastrointestinal tract and frequently had bacteremia during test periods ranging to 35 days. Poults monocolonized by salmonellae or Arizona hinshawii 7:"1,7,8 developed a similar pattern of colonization. Conventionally reared chicks and poults had rather variable colonization by these pathogens, and it was most persistent in the ceca. Groups treated with a native protective microflora were infrequently colonized. Differences in colonization are explainable by lack of competing bacteria in the monocolonized group and by various degrees of protection provided by microflora colonizing the other groups.

Animals↗

PubMedDate not supplied

Adherence of salmonellae and native gut microflora to the gastrointestinal mucosa of chicks.

Adherence of salmonellae to the mucosa of the cecum was demonstrated using scanning electron microscopy. In the absence of other microflora, adherence was also shown at all other levels of the alimentary tract tested. Comparative development of native gut microflora in the ceca was also investigated in chicks treated with selected fecal microflora and in untreated chicks using scanning electron microscopy. In the treated chicks, there was early colonization by adherent bacteria interconnected with fibers, forming a mat of microflora. This mat of microflora may be responsible for preventing colonization of salmonellae in the ceca.

Adhesiveness↗

PubMedDate not supplied

Reciprocal competitive exclusion of salmonella and Escherichia coli by native intestinal microflora of the chicken and turkey.

Both the native intestinal microflora of chickens that protected chicks against salmonellae and Escherichia coli and native turkey intestinal microflora were evaluated for their reciprocal protective capacity in both species against Salmonella typhimurium and a pathogenic strain of E. coli. Nalidixic-acid-resistant forms of the S. typhimurium and E. coli strains were used in seeder-bird and individual-bird challenge tests. Reciprocal protection was provided by native chicken and turkey intestinal microflora in chicks and poults against S. typhimurium and the pathogenic strain of E. coli. The chicken and turkey microflora appeared to be equally effective in protecting the two species from S. typhimurium, but protection against E. coli was somewhat greater in the chicken than in the turkey.

Animals↗

PubMedDate not supplied

Pheasant susceptibility at different ages to Eastern encephalitis virus from various sources in Massachusetts.

Thirteen isolates of Eastern encephalitis (EE) virus recovered from various hosts in Massachusetts differed significantly in pathogenicity for pheasants, 21 days old or older, inoculated subcutaneously with graded doses of virus. Among the least pathogenic were two isolates from Culiseta melanura mosquitoes, and among the most pathogenic isolates was one of pheasant origin. Nine-day-old pheasant chicks were highly susceptible to EE virus. Mortality did not appear to be totally dose-related, for inocula larger than an infecting dose did not increase mortality substantially.

Age Factors↗

PubMedDate not supplied

Immunization of pheasants for Eastern encephalitis.

Pheasants vaccinated twice with as much as one-half horse dose of a commercial Eastern-Western encephalitis adjuvanted cell-culture vaccine did not develop significant hemagglutination-inhibition titers and were not protected against artificial challenge by an Eastern encephalitis virus.

Animals↗

PubMedDate not supplied

Competitive exclusion of intestinal colonization of Escherichia coli in chicks.

A native gut microflora of chickens that protected chicks against Salmonella was evaluated against six pathogenic strains of Escherichia coli using similar methodology. Nalidixic-acid-resistant forms of the E. coli strains were derived for use in seeder-bird and individual-bird challenge tests. A substantial degree of exclusion of intestinal colonization of each of the six pathogenic strains of E. coli was secured in chicks that had been treated with native gut microflora. E. coli appeared to colonize chiefly the crop and cecum. Native gut microflora limited to a much lesser degree the "normal" E. coli present in the intestinal tract of test chicks. The mechanism of protection appears to be similar to that for Salmonella: native gut microflora and E. coli competed for sites of attachment.

Animals↗