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Biomedical subjects

P Chadwick

Publications and source records attributed to P Chadwick.

At least 55 records · Page 3Linked to original sources
PubMed1973

Transferable antibiotic resistance in E. coli and Klebsiella pneumoniae.

Twenty-three of 43 E. coli and 25 of 39 Klebsiella isolates, resistant to two or more antibiotics, transferred one or more resistance genes to a recipient E. coli K(12) culture. Resistances transferred most frequently by both species were those to kanamycin and neomycin. E. coli cultures transferred resistance to tetracycline, chloramphenicol, ampicillin and carbenicillin, whereas Klebsiella isolates transferred resistance to the first two of these antibiotics. Extrapolation of these results to a larger series of isolations of E. coli and Klebsiella from hospital patients suggested that 21 and 18% respectively of cultures of these two organisms carried potentially transferable resistance.

Ampicillin↗
PubMed1973

Resistance of Pseudomonas aeruginosa to gentamicin.

The resistance to gentamicin 4 mug./ml. of 250 Pseudomonas aeruginosa isolates was measured by a proportion method. Twenty-eight (11.2%) of the cultures fell into the most resistant group, in whose populations between 10 and 100% of the organisms were resistant. A relatively high percentage of urinary isolates and a comparatively low percentage of isolates from respiratory sources occurred in this group. Three of the 28 were resistant to carbenicillin 150 mug./ml. and 6 of 18 tested were as resistant to gentamicin 8 mug./ml. as they were to 4 mug./ml. The distribution of Ps. aeruginosa isolates between the different grades of resistance did not change significantly during the 10 months in which the survey was performed.

Bacteriuria↗
PubMed1973

Recurrent urethritis in women.

The bacterial flora of the vestibule, urethra and vagina of a group of patients with recurrent urethritis, and of control subjects without symptoms, was investigated. Organisms regarded as pathogenic, such as enterobacteria and Streptococcus faecalis, were recovered significantly more frequently from patients than from controls, whereas the reverse was found for non-pathogenic organisms. The bacterial flora was similar in the three areas, suggesting that a specimen taken from one region only would give adequate bacteriological information. The vestibule is suggested as a suitable site. The incidence of vestibular pathogens was higher in postmenopausal patients. Perineal length and vestibular pH were very similar in patient and control groups. There was some evidence that in most subjects the bacterial flora of the areas investigated remains fairly constant over a period of several weeks. Although bacterial species commonly responsible for urinary tract infection may often cause recurrent urethritis, the absence of these pathogens from some patients suggests that the etiology of this condition is not yet fully understood.

Adult↗
PubMed1969

Effect of carbenicillin on Pseudomonas aeruginosa.

The activity of carbenicillin against 200 strains of Pseudomonas aeruginosa was measured by a quantitative agar dilution method. Minimal inhibitory concentrations (M.I.C.'s) for five graded inocula were measured in terms of complete inhibition (CI) and reduced growth (RG). The M.I.C. decreased progressively as inocula were reduced, median values for the 200 strains ranging from 100 to 37.5 mug. per ml. by the CI criterion, and from 75 to 25 mug. per ml. by the RG definition. Ratios of M.I.C. obtained for large and small inocula were usually small. Identical M.I.C.'s by both CI and RG criteria were most often obtained when the inoculum for the RG criterion was 1 or 2 logs higher than that for complete inhibition.Population analysis of 15 strains of Ps. aeruginosa showed that one specific drug concentration usually caused a sharp drop in proportion of viable cells, ranging from 3 to 5 logs. None of the populations were completely non-viable even at 150 mug. per ml. There was evidence that the viability of different-sized populations was reduced disproportionately by carbenicillin.Carbenicillin 300 mug. per ml. exerted appreciable bactericidal effect against nine of 15 strains of Ps. aeruginosa after a 24-hour contact period; after only six hours the bactericidal effect was very small.Quantitative sensitivity measurements for carbenicillin should include M.I.C. values for both CI and RG criteria, using a range of inocula for testing. Such M.I.C. values may well be useful in monitoring carbenicillin therapy of tissue infections.

In Vitro Techniques↗
PubMed1966

Field trial of a microcolony method for testing the antibiotic sensitivity of bacteria.

The sensitivity of bacteria to antibiotics may be measured by a rapid method in which the criterion of sensitivity is inhibition of microcolony formation on agar which contains antibiotic. As this method allows a report on the antibiotic sensitivity of a pathogenic bacterium four hours after the test is set up, a trial of the method was carried out in a diagnostic laboratory. Two thousand five hundred and four strains of fast-growing bacteria were tested against 10 antibiotics. The overall correlation rate between the four-hour microscopic readings and the subsequent overnight readings on the same cultures was 98.1%. Seven per cent of the microscopical readings attempted gave indeterminate results, and reports on these tests were withheld until the following day.The time spent in making microscopical readings was considered fully justified by the fact that results of a high proportion of antibiotic sensitivity tests were available one day earlier than is usual with established methods.

Anti-Bacterial Agents↗