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PubMed1986

Prediction of the keeping quality of pasteurized milk by the detection of cytochrome c oxidase.

The keeping quality (KQ) of pasteurized milk samples stored at 5 degrees C and 10 degrees C was satisfactorily predicted after 18 h pre-incubation with 0.05% benzalkonium chloride at 20 degrees C, by estimating the numbers of Gram-negative psychrotrophic bacteria using the simple, cheap and rapid (5 min) assay of cytochrome c oxidase. Correlation coefficients for the relationship between cytochrome c oxidase activity at 20 degrees C and KQ at 5 degrees C or 10 degrees C of -0.89 and -0.84 respectively were obtained. The method correctly predicted the KQ of more than 89% of the samples of pasteurized milk. The assay was not satisfactory for use on samples after pre-incubation at 30 degrees C.

Animals↗
PubMed1986

Estimation of gram-negative bacteria in milk: a comparison of inhibitor systems for preventing gram-positive bacterial growth.

A number of inhibitor systems which have been reported to allow selection of Gram-negative bacteria were tested against Gram-positive and Gram-negative isolates of dairy origin. No one system worked perfectly. A mixture of crystal violet-penicillin-nisin or monensin had least inhibitory effect on Gram-negative isolates whereas Selectocult (a commercially available mixture of Benzalkon A 50% and crystal violet) and sodium deoxycholate were the most effective inhibitors of Gram-positive bacteria. Cetrimide-fucidin-cephaloridine solutions, which have been reported as allowing selective growth of pseudomonads, were not so specific when applied to milk systems.

Animals↗
PubMed1992

Evaluation of the repeatability and reproducibility of European suspension test methods for antimicrobial activity of disinfectants and antiseptics.

A collaborative study to determine the precision of the 1987 Method of test for the antimicrobial activity of disinfectants in food hygiene is described. The repeatability and reproducibility of the test was found to vary according to the nature of the test organism, the type of disinfectant product and the skill of the operator. Results indicate that significant differences in microbicidal effect (ME values) occur within test laboratories between test periods as well as between laboratories, and that much of this variability derives from apparently random variations in the resistance of test strains from day to day and test period to test period. Indications are that although the test is sufficiently reliable to be used as a standard method, adequate test replication must be specified to distinguish borderline pass from borderline fail disinfectant concentrations. The implications of the results in relation to current work on the development of unified European test methods for disinfectants is discussed.

Analysis of Variance↗
PubMed1998

Factors influencing a suspension test method for antimicrobial activity of disinfectants.

Factors influencing the numbers of Escherichia coli DSM 682 and Staphylococcus aureus ATCC 6538 surviving exposure to disinfectants were evaluated by factorial design. Aerobic conditions during pre-cultivation rendered E. coli more resistant to the lethal activity of benzalkonium chloride (BC) and a disinfectant containing grape fruit extract (GSE), whereas Staph. aureus became more sensitive. The degree of shaking and the pre-growth medium (tryptone soy broth or Mueller-Hinton broth) did not influence the result of the bactericidal test. The number of E. coli surviving BC treatment was significantly lower if the neutralizing broth contained thiosulphate, plate pouring was used instead of plate spreading, or the plates were incubated at 37 instead of 30 degrees C. The negative effect of plate pouring was also found with Staph. aureus. The use of filtration without prior neutralization of the disinfectant decreased the numbers of chlorine-treated, but not BC-treated, E. coli. The results showed that rigorous standardization is necessary to obtain good reproducibility of bactericidal suspension tests.

Benzalkonium Compounds↗
PubMed2004

Comparative analysis of antibiotic and antimicrobial biocide susceptibility data in clinical isolates of methicillin-sensitive Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa between 1989 and 2000.

AIMS: To analyse population minimum inhibitory concentrations (MICs) data from clinical strains of Staphylococcus aureus and Pseudomonas aeruginosa for changes over a 10-year period and to look for correlations between the antimicrobials tested. METHODS AND RESULTS: Data from the MIC study of 256 clinical isolates of Staph. aureus [169 methicillin-sensitive Staph. aureus (MSSA), 87 methicillin-resistant Staph. aureus (MRSA)] and 111 clinical isolates of Ps. aeruginosa against eight antimicrobial biocides and several clinically relevant antibiotics was analysed using anova, Spearman-Rho correlation and principal component analysis. Comparisons suggest that alterations in the mean susceptibility of Staph. aureus to antimicrobial biocides have occurred between 1989 and 2000, but that these changes were mirrored in MSSA and MRSA suggests that methicillin resistance has little to do with these changes. Between 1989 and 2000 a sub-population of MRSA has acquired a higher resistance to biocides, but this has not altered the antibiotic susceptibility of that group. In both Staph. aureus and Ps. aeruginosa several correlations (both positive and negative) between antibiotics and antimicrobial biocides were found. CONCLUSIONS: From the analyses of these clinical isolates it is very difficult to support a hypothesis that increased biocide resistance is a cause of increased antibiotic resistance either in Staph. aureus or in Ps. aeruginosa. SIGNIFICANCE AND IMPACT OF THE STUDY: The observation of negative correlations between antibiotics and biocides may be a useful reason for the continued use of biocides promoting hygiene in the hospital environment.

Anti-Bacterial Agents↗
PubMed2005

Antimicrobial activity of chlorhexidine diacetate and benzalkonium chloride against Pseudomonas aeruginosa and its response to biocide residues.

AIMS: The aims of this study were to evaluate the antimicrobial activity of chlorhexidine diacetate (CHX) and benzalkonium chloride (BZK) for strains of Pseudomonas aeruginosa exhibiting increased minimum inhibitory concentrations (MIC) for CHX, and to determine whether residues of chlorhexidine digluconate (CHG) and Hibiscrub (Hib, a formulation containing CHG) affect the susceptibility of P. aeruginosa to these biocides and a number of antibiotics. METHODS AND RESULTS: The bactericidal activity of CHX and BZK was evaluated for strains of P. aeruginosa exhibiting increased MIC for CHX with established suspension and surface disinfection tests. None of the strains of P. aeruginosa exhibiting raised MIC for CHX was less sensitive than the parent strain to CHX or BZK in either method. A test was designed to investigate the effects of dried CHG and Hib residues on P. aeruginosa cells. Exposure of P. aeruginosa to dried residues of CHG or Hib did not result in the organism becoming less sensitive to either biocide or a number of antibiotics. CONCLUSIONS: Pseudomonas aeruginosa strains with raised MIC to CHX were no less sensitive than the parent strain to CHX and BZK in bactericidal investigations. Exposure to dried residues of CHG and Hib did not render P. aeruginosa less sensitive to either of these agents or a number of antibiotics. SIGNIFICANCE AND IMPACT OF THE STUDY: An increase in the MIC for a biocide in a micro-organism does not necessarily result in a failure of the biocide to effectively kill the organism. The residue that remains after the use of an antimicrobial agent can be at a far lower concentration than that initially applied and this study highlights the necessity for further investigations into the effect of residues, at low concentration, on bacterial populations and their role, if any, in the continued problem of antibiotic resistance.

Anti-Bacterial Agents↗
PubMed1985

High performance liquid chromatography of benzalkonium chlorides--variation in commercial preparations.

High performance liquid chromatography (HPLC) has been used to identify and determine the various alkyl benzyldimethylammonium chloride homologues (C10 to C16) present in commercial benzalkonium chloride preparations. The assay is especially suited for routine quality control work since it has proved to be quick and easily reproducible. It has been found that there can be a large degree of variation in the quality of differing benzalkonium chloride sources.

Benzalkonium Compounds↗
PubMed1995

Compatibility of a commercially available low-density polyethylene eye-drop container with antimicrobial preservatives and potassium ascorbate.

The compatibility of the 7 ml size of Steri-Dropper, a commercially available low-density polyethylene sterile eye-drop container, was studied for use with solutions containing the antimicrobial preservatives benzalkonium chloride and phenylmercuric acetate. For benzalkonium chloride, there was no difference between the Steri-Dropper and the glass eye-drop bottles throughout the study period of 84 days. However, there was less phenylmercuric acetate present in the Steri-Dropper compared to the glass containers by the end of the study. The suitability of the Steri-Dropper bottle was also studied for use with potassium ascorbate eye drops; these degraded more in Steri-Dropper compared to glass containers and a yellow discoloration of the product was also seen in these containers. The Steri-Dropper bottle is therefore potentially compatible with dispensed formulations containing benzalkonium chloride and, for short periods only, with phenylmercuric acetate. The container would only be suitable for use with oxygen-sensitive drugs for short periods. Further validation of the suitability of the Steri-Dropper bottle would be required for use with any specific formulation.

Ascorbic Acid↗
PubMed2005

In vitro dentine permeability evaluation of HEMA-based (desensitizing) products using split-chamber model following in vivo application in the dog.

The aim of this study was to evaluate in vitro dentine permeability evaluation of 2-Hydroxyethyl methacrylate (HEMA)-based desensitizing products using split-chamber model following in vivo application in the dogs for three experimental time periods of 1 week, 1 month and 3 months. Buccal enamel of upper and lower canines of nine young dogs was removed and flat dentinal surface was obtained using a water-cooled diamond bur. The dentinal surface divided into four quarters, three experimental and a control. Health-Dent and Gluma Desensitizing agent and Single bond were applied to respective quarters of one tooth, according to manufacturers' instructions. The last quarters were left as control without any applications. For the each experimental period, 10 dentine samples from each group including control were used to measure the hydraulic conductance values. The dentine discs were placed pulp-side down in a split-chamber device in which the plastic spacers containing the rubber 0 rings have a surface area of 1 mm(2) and permeability was measured by fluid filtration. The data were expressed as hydraulic conductance (Lp). Differences in dentine permeability obtained for the desensitizing agents against the control were tested for statistical significance using Kruskal-Wallis one-way ANOVA and Bonferroni-adjusted Mann-Whitney U-tests. Differences in permeability in three time periods for each desensitizing agent were analysed using Friedman's anova and Wilcoxon signed rank tests. All desensitizing applications caused decreased Lp values compared with the control Lp value at the end of 1 week. In the 1-month samples, between the Lp values of Single bond and control, no statistical difference was found (P > 0.05). At the end of the 3-month period, the Gluma Desensitizing agent had the lowest the Lp value (P < 0.05). The result of this study is that the topical application of desensitizing agents led to decrease in dentine permeability in the dog model. The Gluma Desensitizing agent provide the more lasting tubule-occluding effect than the other material tested in this model.

Animals↗
PubMed1997

The effects of topical nasal steroids on rat respiratory mucosa in vivo, with special reference to benzalkonium chloride.

Fifty rats were treated with topical nasal steroids with and without the preservative benzalkonium chloride in their right nostril twice daily for 21 days, while the left nostrils were exposed to 0.9% NaCl. By cutting the noses serially in frontal sections, the structure of the mucosal lining of all parts of the nose could be investigated. Areas with squamous cell metaplasia were observed in all nostrils exposed to topical steroids containing benzalkonium chloride. Such alterations were not observed in any nasal cavities exposed to the topical nasal steroid without the preservative or to 0.9% NaCl. In conclusion, benzalkonium chloride appears to be potentially toxic to the mucosa in vivo.

Administration, Topical↗
PubMed1997

Rhinitis medicamentosa: aspects of pathophysiology and treatment.

With modern vasoconstrictors, such as oxy- and xylometazoline, the risk of developing rhinitis medicamentosa (RM) has been considered to be small or even nonexistent. However, recent studies have shown that overuse of these drugs may result in rebound congestion, nasal hyperreactivity, tolerance, and histologic changes of the nasal mucosa. Using rhinostereometry, it has also been shown that the long-term use of the preservative benzalkonium chloride (BKC) in oxymetazoline nasal spray accentuates the severity of rhinitis medicamentosa in healthy volunteers. A nasal decongestant spray composed of a combination of vasoactive substances and BKC has a long-term adverse effect on the nasal mucosa. BKC alone induces mucosal swelling after 30 days use of the nasal spray in healthy subjects, unlike placebo. According to the author, rhinitis medicamentosa can be defined as a condition of nasal hyperreactivity, mucosal swelling, and tolerance that is induced, or aggravated, by the overuse of topical vasoconstrictors with or without a preservative. An adequate treatment of these patients consists of a combination of vasoconstrictor withdrawal and a topical corticosteroid to alleviate the withdrawal process. The underlying nasal disorder must then be treated. Patients with rhinitis medicamentosa who overuse topical decongestants and are able to stop using such drugs should be careful about taking these drugs again, even for a few days. They must be informed about the rapid onset of rebound congestion upon repeated use in order to avoid the return of the vicious circle of nose-drop abuse.

Benzalkonium Compounds↗
PubMed1988

Antistatic treatment for reducing airborne contamination of insulating materials in intensive care.

In an effort to reduce airborne contamination by Staphylococcus epidermidis harboured on emitted skin scales, items used in patient care were studied as regards bacterial contamination and electrical resistance. An alcoholic benzalkonium chloride sodium was used to coat stopcocks, latex drains, silicon drains and plastic covering. Static electricity did not accumulate when the insulating resistance was less than 10(9) to 10(10) ohms. Study items not treated with the antistatic solution had resistances of greater than 2 x 10(12) ohms, which decreased to 2 x 10(6) to 8 x 10(10) ohms following antistatic treatment. The resistance of the silicon drain before and after antistatic exposure remained unchanged; an increase in its weight after treatment suggests absorption rather than the solution adhering to its surface. Statistically significantly lowered aerobic bacterial colony counts occurred from study items antistatistically treated as compared to those items left untreated. The coating of an entire room and its metal contents failed to decrease bacterial contamination. The results suggest that coating of insulating objects with an antistatic solution will reduce electrical resistance and thereby airborne bacterial contamination.

Air Microbiology↗
PubMed1989

Characterization of crystalline formate dehydrogenase from Candida methanolica.

The crystalline formate dehydrogenase from Candida methanolica, which showed the highest specific activity (7.52 U/mg) so far reported, was characterized in detail. The enzyme is a dimer composed of identical subunits, each containing one SH group related to the catalytic activity. The molecular mass of the enzyme is about 82-86 kDa. The Km values were found to be 3.0 mM for formate and 0.11 mM for NAD+. Even if the enzyme was incubated at pH 6.5-9.5 or at 55 degrees C, the activity remained at 100%. Hg2+, Ni2+, NaCN, NaN3 and p-chloromercuribenzoate strongly inhibited the enzyme activity, while the enzyme showed relatively high resistance to various chelating agents. The amino acid composition and some other physicochemical properties of the enzyme were studied. Immunological studies revealed that formate dehydrogenases of methanol-utilizing yeasts immunologically more or less resemble each other, but differ from those of methanol-utilizing bacteria. Furthermore, yeast formate dehydrogenases can be immunologically classified into three types: (a) the Candida type, (b) the Torulopis/Hansenula/Pichia type and (c) the formaldehyde-resistant yeast type. For simple and large-scale preparation of the enzyme for practical use, treatment of cells of C. methanolica with the commercial cationic detergent, 'Benzalkonium' cation, is useful: the total and specific activities of the enzyme are 1.17-fold and 3.10-fold higher than those of the crude cell-free extract, respectively.

Aldehyde Oxidoreductases↗
PubMed2004

Severe contact dermatitis as a result of an antiseptic bath oil.

Siblings aged 7 and 5 years developed extensive truncal and flexural inflammation and desquamation unresponsive to standard eczema therapy. After delays in diagnosis, subsequent history revealed prior use of an antiseptic bath oil in a much stronger concentration than recommended. The case illustrates the severe irritant contact dermatitis that can arise following inadequate dilution of antiseptic bath oils, presumably as a result of skin contact with benzalkonium chloride and triclosan. Features that may direct attention to such irritant dermatitis are flexural predominance with superficial desquamation and rapid improvement after avoidance of exposure to the antiseptic solution.

Anti-Infective Agents, Local↗
PubMed2004

Corneal epithelial cellular dysfunction from benzalkonium chloride (BAC) in vitro.

PURPOSE: To investigate the functional and morphological toxicity of benzalkonium chloride (BAC) on corneal epithelial cells in vitro. METHODS: Primary corneal epithelial cells were cultured from rabbit cornea. Corneal epithelial cells containing radioactive 51Cr were exposed for 5 min, 10 min, 30 min and 60 min to concentration of BAC 0.001%, 0.005%, 0.01%, 0.05% and 0.1%. Control cells were treated with phosphate buffer solution alone. 51Cr release from epithelial cells into the supernatant was used as an index of epithelial cell lysis. Cell detachment (index of cell dysfunction) was analysed by measuring 51Cr activity in the supernatant and wash fluid. Morphological cell damage was investigated with transmission electron microscopy. RESULTS: With the higher concentration and the longer duration of BAC exposure, corneal epithelial cell lysis was increased significantly (P < 0.05). Cells showed severe damage at BAC concentration over 0.05% during 5 min of exposure. Cell dysfunction appeared markedly at BAC concentrations of 0.005% for 30 min of exposure, but decreased with longer exposure times. There was an increase in significant cytoplasmic damage with longer BAC exposure times, although not with a minimal dose of 0.001%. Disrupted cytoplasmic membranes of corneal epithelial cells appeared at the higher BAC concentration of 0.1%, and at the longer exposure time of 30 min with BAC concentration of at least 0.001%. CONCLUSIONS: BAC can induce corneal epithelial dysfunction, which can damage the corneal epithelial barrier. This effect occurs when BAC is used frequently or for periods over 30 min, even when the BAC concentration is low (0.001%).

Animals↗
PubMed2004

New vehicle based on a microemulsion for topical ocular administration of dexamethasone.

AIM: Eye drops are the most used dosage form by the ocular route, in spite of their low bioavailability. Due to their properties and numerous advantages, microemulsions are promising systems for topical ocular drug delivery. They can increase water solubility of the drug and enhance drug absorption into the eye. The present study describes the development and characterization of an oil-in-water microemulsion containing dexamethasone and the evaluation of its pharmacokinetics in rabbits after topical ocular application. METHODS: The microemulsion was prepared by the titration technique. Its physico-chemical characteristics and stability were determined. The ocular irritation test and the pharmacokinetics of this system were studied in white rabbits. RESULTS: The developed system showed an acceptable physico-chemical behaviour and presented good stability for 3 months. The ocular irritation test used suggested that the microemulsion did not provide significant alteration to eyelids, conjunctiva, cornea and iris. This formulation showed greater penetration of dexamethasone in the anterior segment of the eye and also release of the drug for a longer time when compared with a conventional preparation. The area under the curve obtained for the microemulsion system was more than twofold higher than that of the conventional preparation (P < 0.05). CONCLUSIONS: The microemulsion-based dexamethasone eye drop is advantageous for ophthalmic use because it is well-tolerated in the eye and seemed to provide a higher degree of bioavailability. The developed system shows greater penetration in the eye, allowing the possibility of decreasing the number of applications of eye drops per day.

Administration, Topical↗