Study of the hormetic effect of disinfectants chlorhexidine, povidone iodine and benzalkonium chloride.

The study of the dose-response relationship of disinfectants is of great importance in treating infection, the objective being to use concentrations above the minimal bactericidal concentration (MBC). Below these concentrations, the bacteriostatic or bactericidal effect may be insufficient. Moreover, at low concentrations, a hormetic effect may be observed, producing a stimulation of growth instead of inhibitory action. Hormesis is not well known in the context of antimicrobial substances. This study investigates the possible existence of a hormetic effect in three commonly used antiseptics-chlorhexidine digluconate, povidone iodine and benzalkonium chloride-on strains of reference of Staphylococcus aureus and Pseudomonas aeruginosa. Growth curves were determined for different concentrations of the disinfectants. The variables studied-concentration of disinfectant, instantaneous growth rate and number of generations-were analysed using linear, quadratic and cubic models to adjust for the variables. The three disinfectants tested show a significant hormetic effect with P. aeruginosa and a less significant effect with S. aureus. These findings point to a dose-response effect that is not linear at low concentrations, while hormetic effects observed at some low concentrations result in greater bacterial growth. In infected wounds, materials or surfaces where microorganisms may occupy zones of difficult access for a disinfectant, the hormetic effect may have important consequences.

Specificity of the neutralizers as the cause of errors in evaluating disinfectant efficacy: an assessment of triclosan.

UNLABELLED: One of the most commonly used methods for assessing disinfectants in vitro is the dilution-neutralization test. Although it is known that using an effective neutralizer is essential for obtaining reliable results, in the case of disinfectants like triclosan, whose neutralization is more complicated, an adequate neutralizer is not always used. Here, we compare the efficacy of different neutralizers described previously, and others that have been modified, against several antiseptic formulations of triclosan. The strains of reference used were Pseudomonas aeruginosa, Enterococcus faecium, Staphylococcus aureus and Escherichia coli. The solutions of antiseptic were triclosan 2% aqueous solution, and three alcoholic solutions containing 2, 0·068 and 0·5% triclosan, respectively. In the dilution-neutralization test, six neutralizers with different degrees of complexity were assayed. Our results show that the antiseptic solutions studied are effective against the strains of reference, with the exception of triclosan 2% aqueous solution against Ps. aeruginosa. Most neutralizers proved ineffective, depending on the antiseptic solution and the bacterial species, particularly in the case of Staph. aureus. These findings confirm a need to test every neutralizer specifically for each disinfectant, at the maximum concentration used, and for every specific bacterial strain. SIGNIFICANCE AND IMPACT OF THE STUDY: The choice of an adequate neutralizing agent is essential for obtaining precise results in the evaluation of disinfectants using the dilution-neutralization method. In this study, we show that the neutralization of triclosan and some of its commercial solutions is not a simple task, requiring complex neutralizers. Moreover, the action of the neutralizer is shown to depend on the micro-organism tested. Specificity in view of the disinfectant and the micro-organism calls for performing the neutralizing assay in each particular case of application of the dilution-neutralization method. We also demonstrate that some of the neutralizers described for triclosan in previous studies are not sufficiently effective.

Efficacy of some neutralizers in suspension tests determining the activity of disinfectants.

The ability of six mixtures to neutralize glutaraldehyde, o-phthalaldehyde and peracetic acid was tested using four reference strains: Pseudomonas aeruginosa CIP A22, Escherichia coli CIP 54127, Staphylococcus aureus CIP 53154, and Enterococcus faecium CIP 5855. Glutaraldehyde was the hardest to neutralize, and peracetic acid the easiest. The most effective mixture was Tween 80 with sodium bisulphate, sodium thioglycolate, lecithin and cysteine, and the least effective was Tween 80, lecithin and histidine. The efficacy of the neutralizers may indicate a propensity loss of activity from interfering substances when disinfectants are used in practice.

[Small-cell carcinoma of the larynx]. / Carcinoma de células pequeñas de laringe.

Primary small-cell (also known as oat-cell) neuroendocrine carcinoma of the larynx is an infrequent tumor. We report a case of epiglottic oat-cell carcinoma in a 57-year-old man. Its association with other malignant neoplasms and aggressive behavior in spite of treatment are discussed.

Endotoxin liberation by strains of N. meningitidis isolated from patients and healthy carriers.

The main objective of this study was to assess whether the capacity of Neisseria meningitidis to release endotoxin depends upon the type of strain or upon bacterial mass. Endotoxin release was studied in 32 strains isolated from patients with meningococcal infections and in 49 from asymptomatic carriers, using a quantitative test (limulus test with a chromogenic substrate). The results show that the strains from patients release significantly higher amounts of endotoxin than strains from carriers regardless of serogroup and isolation site. No correlation was found between stage of bacterial growth and the amount of endotoxin liberated. These findings suggest that endotoxin liberation is a characteristic of certain strains of N. meningitidis and is not determined simply by bacterial mass.

[Adhesiveness in Neisseria meningitidis. A virulence factor?]. / Adhesividad en Neisseria meningitidis. Un factor de virulencia?

The role of adhesivity as a factor of virulence in cases of N. meningitidis has not yet been established. Unlike other bacteria in which the presence of adhesivity reflects an enhanced virulence, a high capacity of adherence is associated with a low virulence and invasive capacity in cases of meningococcus. In order to gain more insight into the knowledge of this phenomenon we have studied the adhesivity of 109 strains of N. meningitidis to human pharyngeal epithelial cells. Twenty nine out of the 109 strains were isolated from blood or spinal fluid of patients with meningococcal infection (meningitis or septicemia), whereas the remaining 80 strains were obtained from pharyngeal smears of healthy carriers. The adhesivity was measured as the number of meningococci adhered to 50 epithelial cells according to Craven's scale. Strains of healthy carriers showed a greater adhesivity than that of patients (p less than 0.001). The relevance of the pharyngeal area in the evaluation of the adhesive capacity is in accordance with the hypothesis that meningococcal adhesivity decreases when the microorganism crosses the pharyngeal epithelium. The results would support the concept that the virulence of N. meningitidis is related to its adhesiveness.

Measurement of polycyclic aromatic hydrocarbons and other pollutants.

A single point study of atmospheric pollution has been carried out in Granada (Spain); suspended particulate matter, sulphur oxides, ammoniac, nitrogen dioxide and polycyclic aromatic hydrocarbons were determined. There were variations in relation to the month and the day of the week. The PAHs have been determined through HPLC, with a mobile phase of acetonitrile-water (75-25). The results of measurements of benzo(a)pyrene were between 1.006 and 0.485 micrograms m-3 in two different periods of sampling.

Aplicación epidemiológica de un nuevo esquema de bacteriocinotipia para Proteus mirabilis / Epidemiological application of a new scheme of bacteriocinotyping for Proteus mirabilis

Se realizó un estudio epidemiológico de 81 enfermos infectados por Proteus mirabilis mediante la aplicación de un nuevo esquema de bacteriocinotipia, obteniéndose un 72.83% de tipificación y un total de 31 bacteriocinotipos. Se aplicó el mismo esquema a cepas de Proteus mirabilis aisladas, de los citados enfermos, de heces y/o faringe demostrando que 27,16% de los casos presentan coincidencia del tipo original con el obtenido en los otros especímenes, en un 72.84% no se detecta esta coincidencia