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Biomedical subjects

H W Smith

Publications and source records attributed to H W Smith.

At least 109 records · Page 6Linked to original sources
PubMed1976

The virulence of trimethoprim-resistant thymine-requiring strains of Salmonella.

A thymine-requiring (thy-), trimethoprim-resistant (tmpr) mutant isolated from the faeces of chickens experimentally infected with salmonella typhimurium and treated with mixture of trimethoprim and sulphadiazine was less virulent for chickens than the parent strain and a thy+tmps revertant prepared in vitro from the mutant. The difference in chicken-virulence was more noticeable when the strains were administered orally than when they were administered subcutaneously. All tmpr mutants prepared in vitro from four other salmonella strains were also thy-; those tested were less virulent for chickens and mice than their parent strains. After oral infection, thy- salmonella organisms were found much less commonly in the alimentary tract of chickens then were thy+ organisms. This was especially so in the caeca, the principal site of colonization of both the thy+ and thy- organisms. Relatiely high concentrations of thymine or related compounds were found in the contents of all regions of the alimentary tract of chickens except the caeca; the caeca usually contained low or undetectable concentrations. The thy- salmonella strains would not grow on one brand of briliant green agar because of its deficiency in thymine; their colonial and appearance on other kinds of media used for isolating salmonellae from clinical material was often 'un-salmonella-like'.

Administration, Oral↗
PubMed1976

Further observations on the association of the colicine V plasmid of Escherichia coli with pathogenicity and with survival in the alimentary tract.

A high proportion of invasive strains of Escherichia coli produced colicine V. This property was easily eliminated from 20 of 21 of these strains by 'curing' agents, especially sodium lauryl sulphate, indicating that the genes determining it were located on a plasmid (ColV) which was transmitted from ten of the strains by conjugation. Inoculated intramuscularly, the ColV- forms of all 17 strains tested were less pathogenic for chickens than the corresponding ColV+ forms. The pathogenicity of the ColV- forms of four strains was increased, usually to that of the ColV+ form from which they were derived, by implanting other ColV determinants in them. Much higher concentrations of organisms were found in the blood and liver of chickens infected with ColV+ forms than in chickens infected with ColV- forms. Inoculated intraperitoneally, the ColV+ form of one of the strains, BI88, was more pathogenic for mice than the ColV- form; much higher concentrations of organisms were found in the peritoneal fluid and blood of ColV+-inoculated mice than of ColV--inoculated mice. Inoculated orally and intravenously, ColV+ forms were more pathogenic for colostrum-deprived calves than the corresponding ColV- forms. After mixtures of ColV+ and ColV- organisms of the same strain in ratios of 1:10,1:100 or 1:1000 were given orally, they were found in a similar ratio in the contents of the alimentary tract 1 to 2 days later, when the calves were near to death. Many more ColV+ than ColV- organisms were found in the mesenteric lymph nodes, the deeper tissues and the blood; in the urinary and gall bladders, locations remote from the defence mechanisms of the body, the numbers of ColV- organisms sometimes exceeded those of ColV+ organisms. Colicine V, although demonstrated in the blood at death, did not appear adversely to influence the concentration of ColV- organisms in these calves. Several days after mixtures of ColV+ and ColV- organisms of strain BI88 were taken orally by two human beings, the ColV+ organisms became much more numerous in their faeces than the ColV- ones. Similar results were obtained when colVr organisms of BI88 were included in the inoculum or when a strain whose ColV- form was completely colicine V-resistant was studied. A ColE+ form of BI88 ColV- was no more pathogenic for chickens, mice or colostrum-deprived calves than was a ColE- form of this strain, and it did not persist in the faeces of the two human beings for longer than the ColE- form.

Animals↗
PubMed1976

A transmissible plasmid determining lactose fermentation and multiple antibiotic resistance in a strain of Klebsiella pneumoniae.

In a wild strain of Klebsiella pneumoniae the plasmid that determined lactose fermentation also determined resistance to chloramphenicol, ampicillin, tetracyclines, streptomycin, spectinomycin, and sulphonamides. The plasmid transferred at a very low rate to Escherichia coli K12 and Salmonella typhi. By implanting other transfer factors in the strain the rate of transfer and the recipient range were increased. Plasmid transfer from the modified strain to Salm. typhimurium and Salm. gallinarum was detected in the alimentary tract of experimentally infected chicks fed diets containing ampicillin.

Ampicillin↗
PubMed1976

Radiology of the normal maxillary sinus and related structures.

The radiographic anatomy of the maxillary sinus and related structures as shown in the Waters, lateral, submentovertical, and Caldwell views has been presented. A number of structures, which are of clinical importance but infrequently emphasized, are discussed. Careful study of these four standard sinus projections should provide an excellent knowledge of the radiographic anatomy of the maxillary sinus and its normal variants.

Humans↗
PubMed1976

X-ray crystallographic studies of cyclophosphamide (NSC-26271) derivatives.

Molecular structures of 4-hydroperoxycyclophosphamide (4-hydroperoxy-CP) and of two stereoisomers of 4-hydroperoxyisophosphamide (4-hydroperoxy-IP) have been determined by X-ray crystallography. All compounds, synthesized by Dr. A. Takamizawa by ozonolysis of appropriate open-chain precursors, demonstrate in vivo and in vitro cytotoxicity. The structure results show that for 4-hydroperoxy-CP and both isomers of 4-hydroperoxy-IP the 4-hydroperoxy group is situated axial to the ring. In 4-hydroperoxy-CP and the isomer of 4-hydroperoxy-IP which is the major product of the ozonolysis, the phosphoryl oxygen is equatorial to the ring and trans to the C4-oxygen. A scheme is presented to account for the interconversion of the two 4-hydroperoxy-IP configurations. Since a stereoisomer with a hydroperoxy or hydroxy group equatorial has not been isolated from the ozonolysis synthesis or from the Fenton oxidation of cyclophosphamide (CP), the configuration with C4-oxygen axial which is found in 4-hydroperoxy-CP and both isomers of 4-hydroperoxy-I is probably more stable and may be the configuration of 4-hydroxy compounds formed by the in vivo oxidation of CP, isophosphamide, and trophosphamide (TP). The molecular structure of TP has also been elucidated. Comparison of the conformations of the three chloroethyl alkylating groups of this molecule with those of the two chloroethyl groups of other CP derivatives indicates that these groups are highly flexible and do not assume one favored conformation.

Chemical Phenomena↗
PubMed1975

The effect of antibiotic therapy on the faecal excretion of Salmonella typhimurium by experimentally infected chickens.

Chickens in groups of 40 were infected orally with a nalidixic acid-resistant mutant of Salmonella typhimurium and then fed continuously on diets containing ampicillin, chloramphenicol, furazolidone, neomycin, oxytetracycline, polymixin, spectinomycin, streptomycin or a mixture of trimethoprim and sulphadiazine. The amount of S. typhimurium excreted in their faeces was estimated at intervals by culture on brilliant green agar containing sodium nalidixate, both direct and after enrichment in selenite broth; the amount of Escherichia coli excreted was estimated by culture on MacConkey agar. The feeding of diets containing 500 mg./kg. of ampicillin, furazolidone, neomycin, polymixin, spectinomycin or streptomycin or 100 mg./kg. of trimethoprim and 500 mg./kg. of sulphadiazine for 46 days reduced to a varying degree the amount of S. typhimurium and E. coli excreted, the greatest reduction in S. typhimurium being brought about by the last treatment. The effect was less obvious when the concentration of the antibiotics in the food was decreased fivefold. An important reason for the very limited effect of some of the antibiotics was the emergence of antibiotic-resistant populations of S. typhimurium and E. coli. High concentrations of antibiotic-resistant organisms also arose in the faeces of the chickens fed diets containing tetracyclines and chloramphenicol, treatments which had no apparent effect on the amount of S. typhimurium and E. coli excreted. Much of the antibiotic resistance encountered was determined by R factors, a particular R factor usually being found in the E. coli populations of individual chickens before it was found in their S. typhimurium populations. No S. typhimurium or E. coli were isolated that possessed R factors determining resistance to polymixin, furazolidone or trimethoprim. No S. typhimurium or E. coli were isolated that were polymixin-resistant and no S. typhimurium that were furazolidone-resistant. The few trimethoprim-resistant S. typhimurium isolated were thymine-dependent. The feeding of diets containing the higher concentrations of trimethoprim/sulphadiazine, neomycin, furazolidone or ampicillin for 9 days reduced the amount of S. typhimurium excreted. After the withdrawal of these diets, the amount of S. typhimurium excreted increased to the numbers found in chickens given ordinary diets throughout; the chickens that had been given trimethoprim/sulphadiazine or furazolidone did not remain faecal excreters of S. typhimurium longer than the chickens that had been given ordinary diets. Similar results were obtained with trimethoprim/sulphadiazine when the start of the 9-day treatment period was delayed for an extra 9 days or when it was extended to 18 days.

Animal Feed↗
PubMed1975

The effect of feeding diets containing permitted antibiotics on the faecal excretion of Salmonella typhimurium by experimentally infected chickens.

Groups of 45 chickens were fed continuously on diets containing 10 or 100 mg./kg. of different 'growth-promoting' antibiotics and infected orally with a nalidixic acid-resistant mutant of Salmonella typhimurium. The amount of S. typhimurium organisms excreted in their faeces was estimated by culturing them at weekly intervals and in a standard manner on plates of brilliant green agar containing sodium nalidixate, both direct and after enrichment in selenite broth. All of four groups fed diets containing 100 mg./kg. of nitrovin in three different experiments excreted much larger amounts of S. typhimurium than did groups fed antibiotic-free diets. In some, but not all, experiments, larger amounts were also excreted by groups fed diets containing 10 mg./kg. of nitrovin or 10 or 100 mg./kg. of flavomycin or tylosin. Feeding diets containing 10 or 100 mg./kg. of virginiamycin or bacitracin either did not influence or slightly increased the amount of S. typhimiurium excreted. Two groups fed continuously on diets containing 100 or 500 mg./kg. of sulphaquinoxaline for 44 days excreted smaller amounts of the S. typhimurium organisms that did groups fed antibiotic-free diets; no sulphonamide-resistant organisms of the S. typhimurium strain were isolated from the faeces.

Animal Feed↗
PubMed1975

Transmissible substrate-utilizing ability in enterobacteria.

Three of 152 strains of Escherichia coli transmitted their ability to utilize sucrose (Sac+) to other strains by conjugation. The transfer factor of one of them and of a Sac+ Salmonella thompson strain was thermosensitive. The raffinose-utilizing ability of 27 of 163 E. coli strains was also transmissible. Transmissible raffinose-utilizing ability was a feature of porcine enterpathogenic strains possessing the K88 antigen. The determinants controlling raffinose utilization (Raf) and K88 antigen production were commonly transmitted together from these strains; so also was the determinant controlling enterotoxin production, but to a lesser extent. It was not possible to transfer lactose-utilizing ability from 320 strains of E. coli, salicin-utilizing ability from 12 strains of E. coli or dulcitol-utilizing ability from 99 strains of E. coli and 88 strains of salmonellae. Sucrose- and raffinose-utilizing ability were transmitted separately to several Salmonella sp., including Salm. typhi, to Shigella flexneri and Sh. sonnei and to a variety of strains of E. coli. A strain of Salm. typhimurium in which Sac had been established and a strain of E. coli in which Raf had been established survived less well in the alimentary tract of chickens than their Sac minus or Raf minus parent strains.

Animals↗
PubMed1975

Sex pili as immunogens.

Groups of chickens were vaccinated intravenously with live cultures of Escherichia coli K12 possessing transfer factors F, I, A2 or no transfer factor (Tra-minus) and their immunity challenged by injecting them intravenously with an F-plus strain of Salmonella heidelberg or an F-plus or I-plus strain of Salmonella typhimurium. Compared with the Tra-minus strain, vaccination with the F-plus, but not the I-plus or A2-plus, K12 strain significantly reduced the mortality rate caused by the F-plus salmonella strains; vaccination with the I-plus or A2-plus, but not the F-plus, K12 strain significantly reduced the mortality rate caused by the I-plus salmonella strain.

Agglutination Tests↗
PubMed1975

The establishment of K99, a thermolabile, transmissible escherichia coli K antigen, previously called "Kco", possessed by calf and lamb enteropathogenic strains.

The transmissible antigen in enteropathogenic E. coli strains from calf and lamb, previously called Kco, is established as the E. coli K99 antigen. It is probably of protein nature since it is destroyed by heating. It is pointed out that other antigens present, growth medium and unknown factors are of great importance for the demonstration of this antigen.

Animals↗