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Biomedical subjects

W R Mitchell

Publications and source records attributed to W R Mitchell.

33 records · Page 2Linked to original sources
PubMed1974

Drug resistance among pathogenic bacteria from animals in Ontario.

Prevalence of antimicrobial drug resistance among over 3000 clinical isolates of animal pathogens in Ontario during 1971-72 has been studied. A high number of multiple resistance patterns is prevalent among members of Enterobacteriaceae, especially Escherichia coli and Salmonella typhimurium. The most common resistance pattern among bovine strains was against not less than six drugs in common use. Among different animal species the bovine population was found to be the source of a high percentage of chloramphenicol resistant E. coli and S. typhimurium organisms. All the isolates resistant to this drug were in addition resistant to three or more other antibiotics of established therapeutic value. All the multiple resistant isolates of S. typhimurium tested had R factors and they transferred most of the resistance determinants including that for chloramphenicol to a recipient E. coli in vitro.Penicillin resistance among Staphylococcus aureus of bovine mammary origin did not appear to be high. Antimicrobial drug susceptibility patterns of staphylococci, streptococci and Corynebacterium sp indicate effective in vitro activity with many antimicrobial agents.

Ampicillin↗
PubMed1973

Marble spleen disease of pheasants in Ontario.

Two outbreaks of marble spleen disease were observed in pen-raised pheasants in Ontario on the same farm in the summer of 1971 and in 1972. In both instances, a mortality of 3% per day lasted for approximately 14 days. Fifteen birds were necropsied and tissues removed and examined histologically and by electron microscopy. In addition splenic material was injected into adult pheasants. The gross lesions, characterized by enlarged greyish-white mottled spleens and acute congestion and oedema in the lungs, were identical to those described by previous authors. Histological examination of livers, lungs, spleens and proventriculi revealed some reticular-type cells which contained either an eosinophilic or a basophilic intranuclear inclusion. Electron microscopy of the affected spleens revealed cells with massive intranuclear accumulations of virus particles. Although transmission trials failed, the evident histological and electron microscopy lesions confirm the suggestion by other authors that this is a viral disease affecting the reticulo-endothelial system.

Animals↗
PubMedDate not supplied

Effect of chlorination of drinking water on experimental salmonella infection in poultry.

The type of drinker used for poults influenced the level of free available chlorine (FAC) in chlorinated water as well as the total plate count, fecal coliform count, and number of salmonellae in chlorinated and non-chlorinated drinking water. Nipple drinkers maintained higher levels of FAC in drinking water than Swish-cups, Swish-cups maintained higher levels than MarkIII, and MarkIII maintained higher levels than trough drinkers. The level of FAC retained in the water in trough drinkers was insufficient to exert a bactericidal effect against coliforms and salmonellae. Chlorination of drinking water and the resulting diminished number or absence of salmonellae in the drinking water did not lower the number of salmonellae per gram of cecal contents in challenged or unchallenged but exposed poults. The number of salmonellae per gram of cecal contents decreased significantly (P less than 0.01) in poults between 14 and 21 days of age, irrespective of whether or not the poults drank chlorinated water.

Animals↗
PubMedDate not supplied

Practical aspects of competitive exclusion for the control of Salmonella in turkeys.

In laboratory trials, a fourth-passage culture of adult chicken cecal contents was protective against challenge with Salmonella typhimurium in turkey poults raised on wood-shavings poultry litter. The culture was not protective against pre-treatment exposure to hatchery-introduced S. bredeney and was inhibited in poults that had received an antibiotic injection at the hatchery. The inhibitory effect of the hatchery antibiotic could be avoided if the cecal-culture treatment was delayed by 3 to 4 days after antibiotic injection. Under field conditions, there was a significant reduction in the salmonella contamination of turkeys and their environment when cecal culture was given to poults raised on wood-shavings litter sprayed with a quaternary ammonium compound. When used alone, both the cecal culture and the litter disinfectant were ineffective in preventing the establishment of S. heidelberg infection. Further studies are required to confirm the possibility of a synergistic effect between the two treatments. For the control of salmonella in turkeys, use of cecal cultures may be limited by the interference of antibiotics and by their failure to protect against pretreatment exposure to salmonella.

Animals↗