Elizabeth J. Shaw

Polarisation fluoroimmunoassay of gentamicin.

A polarisation fluoroimmunoassay has been developed for the routine determination of gentamicin levels in serum. The method employs fluorescein-labelled gentamicin which is easily, reproducibly and economically prepared and has excellent shelf-life. The assay is fast (minimum incubation time 2 min) and requires 1.25 mul of serum. There is no separation step prior to readout of results. Recovery experiments reveal no serum effects. Intra- and inter-assay coefficients of variation are of the order of 10% or less. Estimations of gentamicin levels in patient serum samples correlate closely with those obtained by bioassay (r = 0.93) and radioimmunoassy (r = 0.97).

Spread of Escherichia coli colonizing newborn babies and their mothers.

Most babies are colonized by the predominant strains of Escherichia coli present in their own mothers faecal flora. Those babies who did not acquire their maternal faecal flora acquired strains of E. coli belonging to a small number of the possible serotypes. Moreover, the same serotypes were found in several babies and other mothers, suggesting spread within the ward. These few strains included some of the O groups which had previously commonly been found as urinary pathogens. These strains may have increased potentialities for colonization of human bowel. Antigenic and biochemical variation was observed among the strains.

Intraperitoneal povidone-iodine in peritonitis

The efficacy of intraperitoneal povidone-iodine was evaluated in mice and rats with induced gram-negative peritonitis. Two hundred twenty Theiller Original mice (20–25 g) were injected intraperitoneally with 0.15 to 0.2 ml of Escherichia coli 014/K85/H4, at 107 organisms/ml. An intraperitoneal injection of 0.2 ml of povidone-iodine solution (containing 0.075% available iodine) significantly reduced mortality (P

A simple, rapid fluorimetric assay of amoxycillin in plasma.

A method for estimation of amoxycillin in plasma is described, based on the formation of a fluorescent derivative which is measured in the presence of 2-methoxyethanol. Drugs commonly administered together with amoxycillin do not appear to interfere with the assay. Data on the sensitivity, accuracy and linearity of the assay are presented together with a comparison with the microbiological assay.

Prophylactic intraperitoneal povidone-iodine in alimentary tract surgery

In controlled experiments intraperitoneal povidone-iodine significantly reduced the mortality of mice (p less than 0.01) and rats (p less than 0.01) with induced peritonitis. Povidone-iodine irrigation of the rat colon before and after anastomosis did not interfere with healing or inhibit peritoneal adhesion formation. However, a newly formulated povidone-iodine solution containing increased PVP significantly reduced adhesion formation in a controlled study in rats.

Pseudomonas thomasii in a hospital distilled-water supply.

Summary The distilled water supply in a pharmacy was found to be contaminated with Pseudomonas aeruginosa and P. thomasii Disinfection of the piping system proved impracticable, and use of the water from this supply was discontinued.

Relationship of an epidemic strain of Escherichia coli O125.H21 to other serotypes of E. coli during an outbreak situation in a neonatal ward

Summary An epidemic of mild gastroenteritis in a neonatal ward of a London hospital is described. The causative organism was Escherichia coli O125.H21. Although efforts to control the spread of the organism were instituted, it spread to affect 16 babies. The faeces of all mothers, their babies and ward staff were examined for E. coli and the isolates serotyped. In contrast to the epidemic strain, the other serotypes did not spread to that extent.

Effect of noxythiolin on experimental peritonitis.

The intraperitoneal instillation of noxythiolin in the treatment of peritonitis is widespread in clinical practice despite contradictory evidence as to its efficacy. In this light the value of noxythiolin was reappraised by studying its effect in guinea-pigs and mice with induced bacterial peritonitis. Treatment with a 1% solution of noxythiolin reduced the mortality rate of mice by 14% (P less than 0.1). The guinea-pig model proved unreliable giving inconsistent mortality rates throughout. Further studies are required to determine the optimum dose and concentration of noxythiolin while the search for more effective intraperitoneal antiseptics should continue.

Fluoroimmunoassay of serum gentamicin

SummaryFluoroimmunoassay methods permit rapid, reliable and technicaly simple estimation of gentamicin at levels of clinical significance in microlitre amounts of serum samples. The reagents required are fluorescein-labelled gentamicin, which is easily and economically prepared and has indefinite shelf life, and anti-gentamicin serum. All methods are based on competitive binding to antiserum between labelled and unlabelled gentamicin, but because of the versatility of the fluorescence technique, various assay modes are possible. When assay of gentamicin is performed to determine apprioriate clinical dosage the preferred method is the “quenching fluoroimmunoassay” in which determinations are made by means of conventional fluorimetry of unseparated immunoassay incubation mixtures. Assay time for this technique is of the order of 10 minutes per sample. When extreme sensitivity (10 ng/ml gentamicin) is necessary, the fluorescein groups of the labelled gentamicin may be conveniently radioiodinated to provide gamma-labelled material suitable for “radiofluoresceinimmuno-assay”. In this instance total assay time is about 4 hours.

Intraperitoneal noxythiolin and povidone-iodine in experimental peritonitis

The efficacy of intraperitoneal noxythiolin and povidone-iodine was compared in mice and rats with induced Gram-negative peritonitis. Noxythiolin 1% solution reduced the mortality of mice from 65 to 41% (P<0·1) but was ineffective in rats. Povidone-iodine (6·0-7·5 mg available iodine/kg body weight) significantly reduced the mortality of both mice (P<0·001) and rats (P<0.01) in treated animals compared to matched controls. The mortality rate of rats treated with povidone-iodine was significantly less than those treated with noxythiolin (P<0·01).