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Biomedical subjects

H W Smith

Publications and source records attributed to H W Smith.

At least 127 records · Page 7Linked to original sources
PubMed1973

The incidence of antibiotic resistance and other characteristics amongst Escherichia coli strains causing fatal infection in chickens: the utilization of these characteristics to study the epidemiology of the infection.

Of 173 epidemiologically unrelated strains of Escherichia coli isolated from the pericardial sac of chickens that had died from infection with these organisms in England in 1972, approximately 1 year after the introduction of legislation forbidding the routine use of feeds containing ;therapeutic' antibiotics, 83.8% were resistant to sulphonamides, 31.2% to tetracyclines, 20.8% to furazolidone, 18.5% to streptomycin, 2.9% to spectinomycin and 1.2% to ampicillin; none of the strains were resistant to chloramphenicol, neomycin, polymixin, trimethoprim or nalidixic acid. The sulphonamide resistance and possibly some of the resistance to other agents might have been the consequence of sulphonamides being exempted from the legislation. Much of the resistance, with the exception of that to furazolidone, was of the transferable type. Many strains possessed transfer factors in the absence of any known transferable characteristic. Colicine production was twice as common in the pathogenic strains as in a collection of strains isolated from the faeces of healthy chickens; about half of it was transferable.By means of serology, antibiotic resistance and other markers, it was found that several different kinds of E. coli were usually incriminated in any one outbreak of E. coli infection in broiler chickens. Sometimes the same kinds of E. coli were found in outbreaks in consecutive crops of chickens on the same farm. New kinds, too, appeared to be brought in by replacement chickens.

Ampicillin↗
PubMed1973

Replication of T4 DNA in Escherichia coli treated with toluene.

Deoxyribonucleoside triphosphates are incorporated into T4 DNA in infected cells treated with toluene. Under the proper conditions the incorporation is controlled by the known T4 DNA polymerase and proceeds by a semiconservative mechanism. Both strands of the phage DNA are replicated into a high molecular weight progeny molecule. The replication system is accessible to extracellular pancreatic DNase added to the reaction mixture. At early times after infection a second replication system, not under control of the gene 43 polymerase, has been detected which synthesizes T4 DNA in toluenized cells.

Adenosine Triphosphate↗