Competitive enzyme-linked immunosorbent assay for Treponema pallidum antibodies.

A competitive enzyme-linked Treponema pallidum immunosorbent assay (CETPIA) was compared with the standard serological tests for syphilis. Of 3081 serum samples submitted, 2883 gave negative results in the CETPIA and the routine screening tests. Positive results were obtained in the CETPIA and in one or more of the specific treponemal tests with 115 samples. Discrepancies in the results of the CETPIA and standard serological tests were found with 83 serum samples, most of these were attributed to biological false positive reactions in the Venereal Disease Research Laboratory (VDRL) test. CETPIA may have a role in the serological diagnosis of syphilis.

Five days versus one day of penicillin as prophylaxis in elective neurosurgical operations.

Of 423 patients undergoing elective cranial and spinal operations, infections due to Staphylococcus aureus occurred in 3 of 217 (1.4%) receiving penicillin for 1 day, in none of 206 receiving penicillin for 5 days. There was no significant difference in rates of infection between the two groups receiving penicillin. It is concluded that penicillin for 1 day is as effective as penicillin for 5 days, in the prevention of wound infections due to S. aureus.

Psittacosis in the elderly.

Six elderly patients with serological evidence of psittacosis but atypical syndromes are described. These cases illustrate the difficulties in diagnosing this infection in the old. Four patients were febrile and three had lesions visible on X-ray of the chest. Three died, in one acute toxic viral myocarditis seemed the cause. All were treated with tetracycline, which must be given generously. Psittacosis infection would probably be more commonly diagnosed in the old if serological examinations were carried out in old people immediately on their administration to hospital because of a severe febrile illness. Serological tests appear clearly to be the most certain means of identifying psittacosis in patients with multiple pathology.

Quality control of the isolation rate of pathogens in medical microbiology laboratories.

Two statistical analyses are suggested to compare the success rates in isolating and identifying pathogenic organisms from specimens achieved by different laboratories participating in a quality control scheme. An example is given in which the analyses are applied to 25 laboratories that received 30 simulated specimens.

Staphylococci in swimming pool water.

During a period of five years 1192 water samples from swimming pools were examined for staphylococci and 338 for coliform organisms only. Eighty-nine different pools were sampled.Numbers of staphylococci, estimated by the membrane filtration technique did not bear any significant relation to either bathing load or concentration of free chlorine.Wide variation in the staphylococcal count was observed when different parts of a pool were sampled on the same occasion.The only practicable standard for pool samples in relation to staphylococci would appear to be that these organisms should be absent from 100 ml. water when the pool has been out of use during at least ten hours before sampling if filtration and chlorination are adequate.

Inhibition of some respiration and dehydrogenase enzyme systems in Escherichia coli NCTC 5933 by phenoxyethanol.

Low concentrations (less than 0.2% w/v) of phenoxyethanol stimulated both the rate of respiration and total oxygen uptakes of Escherichia coli NCTC 5933 suspensions with glucose and other substrates, whilst higher concentrations (0.2--0.6% w/v) although still below those showing significant bactericidal activity, produced progressive levels of inhibition. The degree of respiratory inhibition varied with different substrates in the order malate less than succinate less than pyruvate less than or equal to glucose less than lactate, and suggested appreciable inhibition at a point after malate in the tricarboxylic acid cycle. This suggestion was supported by the use of tetrazolium salts as alternative electron acceptors, and by cytochrome difference spectra, which together implicated malate dehydrogenase as the most likely site of action. Isolated dehydrogenase enzymes of the tricarboxylic acid cycle in cell-free preparations were unaffected by high concentrations of phenoxyethanol (0.8% w/v) with the exception of malate dehydrogenase which was inhibited in extracts to extents similar to those of malate oxidation by intact bacteria. Lineweaver-Burke plots for malate dehydrogenase activity in the presence of phenoxyethanol suggested a competitive inhibition of the oxaloacetic acid-limited reaction and a non-competitive inhibition of the NADH-limited reaction. Accordingly, Ki values were found to be low when the rate of reaction was limited by oxaloacetic acid concentration yet relatively high when NADH was rate limiting.

The lethal action of 2-phenoxyethanol and its analogues upon Escherichia coli NCTC 5933.

Bactericidal activity has been assessed for a number of glycolmonophenyl ethers towards Escherichia coli NCTC 5933, and the action of one analogue, 2-phenoxyethanol, has been studied in greater detail. For this compound the onset of bactericidal activity towards Escherichia coli occurred at concentrations which also induced considerable increases in drug uptake, marked leakage of cytoplasmic constituents, the cellular penetration of N-tolyl-alpha-napthylamine-8-sulphonic acid, and morphological changes consistent with gross membrane damage. However, temperature coefficients of rates of cellular leakage of low molecular weight cytoplasmic constituents, and rates of kill, were markedly different and suggested that the two phenomena were not integrally related, but that each was a consequence of some other action of the drug. Drug levels considerably below those possessing lethal activity, however, promoted the ready efflux of potassium ions from cells and caused disorganisation of the outer lipopolysaccharide-rich regions of the cell envelope.

Effect of phenoxyethanol on the permeability of Escherichia coli NCTC 5933 to inorganic ions.

Concentrations of phenoxyethanol which retarded the growth rate of Escherichia coli NCTC 5933 in nutrient broth, stimulated the rates of respiration and total oxygen uptake of cell suspensions with glucose as carbon source, and were able to dissipate artificially induced membrane proton gradients. In cells with repressed oxidative phosphorylating activity, no stimulation of respiration was observed. These actions were characteristic of uncouples of oxidative phosphorylation. Similar concentrations of the drug caused additional increased permeability of the cytoplasmic membrane to K+ but not to Li+, Na+, Ca++, Mg++, NO-3, Cl-, So--4, or PO---4. Drug induced permeability of the membrane to protons and potassium ions were not found to be directly coupled.

Effect of 2-phenoxyethanol upon RNA, DNA and protein biosynthesis in Escherichia coli NCTC 5933.

The effects of concentrations of 2-phenoxyethanol of negligible bactericidal activity upon the rates of biosynthetic assimilation by Escherichia coli, of 14C-thymidine, 14C-uracil, 14C-phenylalanine and 14C-glucose, were assessed. Increasing the drug concentration from 0.05-0.4% w/v progressively increased inhibition of growth rate, measured as changes in optical density. Thymidine, uracil and glucose assimilation were inhibited to an extent similar to growth rate, whilst phenylalanine incorporation was markedly less sensitive at the lower concentrations (leads to 0.2% w/v). In addition to its previously observed roles in inhibiting oxidative phosphorylation and TCA cycle enzymes, it is suggested that 2-phenoxyethanol can exert a more direct inhibitory action upon DNA and RNA biosynthesis and possibly on protein biosynthesis.

Correlations between physico-chemical properties and antimicrobial activity for some glycolmonophenyl ethers.

Aqueous solubilities, octanol: water partition coefficients and Rm were determined for twelve glycolmonophenyl ether analogues. Their correlation with growth inhibitory activity towards eight bacterial, yeast and fungal species was assessed. Correlations were also sought between bactericidal activity and inhibition of respiration of E. coli suspensions with these physico-chemical properties. Variations in antimicrobial activity generally correlated well with aqueous solubility. Partition coefficients were found to correlate poorly with biological response with the exception of those correlations involving Gram-negative micro-organisms. Regression equations relating solubility to biological activity generally varied significantly between micro-organisms and for different biological responses with E. coli. This suggested the possibility of different problems of drug penetration in different microbial species and/or different sites of action for the various biological responses.