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.
Antibiotic resistant Escherichia coli on a commercially prepared chicken carcass colonized the gut of a human volunteer handling the raw meat. Strains from both sources, identified on the basis of serotype and characterization of plasmids carried, were found to be identical.
The distribution of O-antigen types of Escherichia coli in calves over a ten-month period has been determined. A total of 400 calves from separate farms located over a wide area of England and Wales have been surveyed. Of the 148 0-types recognized, 93 were found in calves, compared with 107 in a previous survey in man; 42 of these were common to both hosts. In calves 60% of isolates were resistant to at least one antibiotic. Of these, 71 belonged to ten O-types, 9 of which were found in man. It is concluded that calves form a potential reservoir of R plasmid carrying E. coli.
The 0-antigen types of 600 independently isolated Escherichia coli strains from human feces have been determined, and the types have been related to the antibiotic resistance pattems of the strains. The relative abundance of each 0-antigen type differed in the susceptible and resistant series of strains. The majority (86%) of the resistant strains carried R plasmids. Resistant E. coli (20.3%) were found associated with 0-antigen types 8, 9 and 101, whereas the susceptible strains covered a wide range of 0-antigen types. Examination of 174 resistant strains isolated from calf feces also showed a prevalence of 0-antigen types 8, 9, 101 (24.1%), and it seems probable that strains expressing these three 0-antigen types commonly carry R plasmids in the alimentary tracts of man and calves. The number of strains not typeable with the 0 sera available were similar in the human (12.5%) and the calf (11.5%) series. There are no grounds for distinguishing "human" from "calf' E. coli on the basis of their 0-antigen reactions.
Some antibiotic-resistant bacteria occur naturally in the environment but many arise by contamination with human and animal excreta in sewage, slurry and manure. These may be ingested as contaminants of water, animal feeds and cultivated foods or, in the case of animals, by licking their environment. Gene transfer has been demonstrated in voided calf faeces and the resultant transconjugants, subsequently ingested, colonized the calf gut. Identified strains of antibiotic-resistant Escherichia coli have been traced from the gut contents of pigs, calves and chickens to carcasses at slaughter and ultimately shown to colonize the gut of a human volunteer handling and eating the meat. Similarly, antibiotic-resistant strains of Salmonella typhimurium phage type DT204c, have been isolated from calves and humans indicating a possible zoonotic spread. The significance of these observations is discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.