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PubMed2002

Adaptive resistance to benzalkonium chloride, amikacin and tobramycin: the effect on susceptibility to other antimicrobials.

AIMS: To produce strains of antimicrobial-resistant Pseudomonas aeruginosa via adaptation to benzalkonium chloride, amikacin and tobramycin and to then examine the incidence, or otherwise, of cross-resistance between antibiotics and between antibiotics and benzalkonium chloride. METHODS AND RESULTS: Adaptation was obtained by progressive subculturing in subinhibitory concentrations of the antimicrobials. Pseudomonas aeruginosa NCIMB 10421 adapted to grow in high concentrations of benzalkonium chloride (BC) had lower MIC to antibiotics than the wild type, whereas Ps. aeruginosa adapted to grow in antibiotics had greater MIC to benzalkonium by a small degree. CONCLUSIONS: Adaptive resistance to BC of Ps. aeruginosa generally produced cultures with a decrease in resistance to several antibiotics. Adaptive resistance to the aminoglycosides Ak and Tm produced a low-level increase in tolerance to BC. The adaptive mechanisms of resistance appear to be different for the different types of antimicrobials used. SIGNIFICANCE AND IMPACT OF THE STUDY: The relationships between biocide and antibiotic resistance are complex. It appears, from this study, that an organism resistant to a common biocide can become sensitive to antibiotics, but the converse was not true. Could this observation be used in a strategy to alleviate antibiotic resistance?

Adaptation, Physiological↗
PubMed2003

Clonal variation in maximum specific growth rate and susceptibility towards antimicrobials.

AIMS: To examine associations between growth rate within bacterial populations and survival patterns following treatment with antimicrobial agents. METHODS AND RESULTS: Time survival data were generated for the inactivation of Escherichia coli populations, grown as batch and continuous cultures, exposed to ciprofloxacin, benzalkonium chloride and tetracycline. Time-survivor plots were biphasic. Surviving cells were collected and immediately re-exposed to agent or were regrown and then re-exposed. Survivors were resistant to immediate challenge with any of the treatment agents. This resistance was lost on regrowth suggesting that survival reflects an expressed phenotype within a subset of the culture (persisters) rather than individual resistant clones or nonspecific quenching of the test agent. The fraction of persisters increased with decreasing growth rate when cultures were prepared in continuous culture. CONCLUSIONS: Clonal growth rates within populations were determined by culture of individual cells within microtitre plate wells. The fraction of clones, in batch cultures, growing maximally at rates below the apparent threshold for susceptibility to the test agents was sufficient to explain the results of continuous culture experiments. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of persisters in populations of bacteria relate to small subset of cells that are growing only slowly or are metabolically quiescent.

Anti-Infective Agents↗
PubMed2004

Cross-resistance to antibiotics of Escherichia coli adapted to benzalkonium chloride or exposed to stress-inducers.

AIMS: To study the effects of adaptation and stress on the resistance to benzalkonium chloride (BC) and cross-resistance to antibiotics in Escherichia coli. METHODS AND RESULTS: Precultivation of E. coli ATCC 11775 and E. coli DSM 682 in the presence of subinhibitory concentrations of BC or stress inducers (salicylate, chenodeoxycholate and methyl viologen) resulted in higher minimum inhibitory concentration (MIC) of BC and chloramphenicol (CHL). Adaptation to growth in sixfold of the initial MIC of BC resulted in stable BC resistance and enhanced tolerance to several antibiotics and ethidium bromide (EtBr). The MIC of CHL increased more than 10-fold for both strains. Enhanced efflux of EtBr in adapted E. coli ATCC 11775 indicated that the observed resistance was due to efflux. Changes in outer membrane protein profiles were detected in the BC-adapted cells. There were no indications of lower membrane permeability to BC. CONCLUSIONS: Induction of stress response or gradual adaptation to BC or CHL results in acquired cross-tolerance between BC and antibiotics in E. coli. Enhanced efflux was one of the observed differences in adapted cells. SIGNIFICANCE AND IMPACT OF THE STUDY: Provided not taking due precautions, extensive use of disinfectants could lead to emergence of antibiotic-resistant isolates.

Adaptation, Physiological↗
PubMed2004

The long-term effectiveness of five current desensitizing products on cervical dentine sensitivity.

The aim of this study was to compare the long-term effectiveness of five desensitizing products on 25 male and 27 female patients (total 52) aged 21-67 years (mean 36 +/- 7 years) suffering from cervical dentine sensitivity. All subjects were seen by the same examiner (ID) who was blinded to the applied treatment for 3-month clinical study. Patients were asked to record their overall sensitivity by marking a point on a 10 cm Visual Analogue Scale (VAS). Two hundred and seventy-seven sensitive teeth were treated by one of the five desensitizing products, all of which were placed following manufacturers' instructions by the other investigator (AS). A paired (split mouth) study design was used and selection of quadrants was randomized. At the post-treatment and at 10 days and 3 months periods, sensitivity measurements were recorded by the same investigator (ID). Statistical analysis showed that all of the VAS scores at post-treatment evaluation points were significantly decreased compared with baseline data (P < 0.05). There was a significant reduction in mean sensitivity scores in the Protect Liner F and the Health-Dent Desensitizer groups when compared with Fluoline varnish at the 10-day time point (P < 0.05). At 3 months, the Protect Liner F group continued to show a significantly reduced sensitivity level when compared with Health-Dent Desensitizer, Single Bond, Fluoline and Gluma Desensitizer (P < 0.05). The present study demonstrated that although at the end of 3-month evaluation period all desensitizers showed lower VAS sensitivity values compared with baseline, there were differences in the level of reduction of cervical dentine sensitivity.

Adult↗
PubMed2002

Regulatory network of lipopolysaccharide O-antigen biosynthesis in Yersinia enterocolitica includes cell envelope-dependent signals.

Lipopolysaccharide (LPS) is a glycolipid present in the outer membrane of all Gram-negative bacteria, and it is one of the signature molecules recognized by the receptors of the innate immune system. In addition to its lipid A portion (the endotoxin), its O-chain polysaccharide (the O-antigen) plays a critical role in the bacterium-host interplay and, in a number of bacterial pathogens, it is a virulence factor. We present evidence that, in Yersinia enterocolitica serotype O:8, a complex signalling network regulates O-antigen expression in response to temperature. Northern blotting and reporter fusion analyses indicated that temperature regulates the O-antigen expression at the transcriptional level. Promoter cloning showed that the O-antigen gene cluster contains two transcriptional units under the control of promoters P(wb1) and P(wb2). The activity of both promoters is under temperature regulation and is repressed in bacteria grown at 37 degrees C. We demonstrate that the RosA/RosB efflux pump/potassium antiporter system and Wzz, the O-antigen chain length determinant, are indirectly involved in the regulation mainly affecting the activity of promoter P(wb2). The rosAB transcription, under the control of P(ros), is activated at 37 degrees C, and P(wb2) is repressed through the signals generated by the RosAB system activation, i.e. decreased [K+] and increased [H+]. The wzz transcription is under the control of P(wb2), and we show that, at 37 degrees C, overexpression of Wzz downregulates slightly the P(wb1) and P(wb2) activities and more strongly the P(ros) activity, with the net result that more O-antigen is produced. Finally, we demonstrate that overexpression of Wzz causes membrane stress that activates the CpxAR two-component signal transduction system.

Benzalkonium Compounds↗
PubMed2002

Effects of anti-inflammatory drugs and preservatives on morphologic characteristics and migration of canine corneal epithelial cells in tissue culture.

OBJECTIVE: To determine the effects of commonly used ophthalmic corticosteroids, suprofen, polysulfated glycosaminoglycan and preservatives on morphologic characteristics and migration of canine corneal epithelium grown in cell culture. ANIMALS STUDIED: Corneal epithelial cells harvested from the corneas of euthanized dogs were propagated in cell culture. PROCEDURES: Canine corneal epithelium was grown in tissue culture. The cells were treated with different corticosteroids, polysulfated glycosaminoglycan, suprofen or preservatives at different concentrations after a defect was created in the monolayer. Cellular morphologic characteristics and closure of the defect were compared between test drugs and controls. RESULTS: Morphologically the cells treated with dexamethasone were essentially the same as controls. Prednisolone and hydrocortisone caused rounding and shrinkage of the cells. Both suprofen and polysulfated glycosaminoglycan caused no apparent changes in morphologic characteristics at the lowest concentrations tested, but at higher concentrations there was a concentration-dependent degree of rounding and shrinkage. Benzylkonium chloride and thimerosal caused rounding and shrinkage of all the cells at all concentrations tested. Dexamethasone, hydrocortisone, and suprofen did not inhibit epithelial migration over the defects at the lowest concentrations tested. All other drugs and concentrations inhibited cellular migration. CONCLUSION: Dexamethasone affected the morphologic characteristics and migration of corneal epithelial cells less than hydrocortisone and prednisolone; therefore, dexamethasone may be the drug of choice when a corticosteroid is indicated and an epithelial defect is present. Suprofen and polysulfated glycosaminoglycan caused a concentration-dependent effect on morphologic characteristics and migration. The preservatives caused severe changes and inhibited migration of the canine corneal epithelial cells at all concentrations and may therefore contribute to poor epithelialization of ulcers treated with preservative-containing drugs.

Administration, Topical↗
PubMed2003

Effects of benzalkonium chloride treatment on the intramural innervation of the upper urinary tract.

OBJECTIVE: To establish a model for investigating the pathophysiology of pelvi-ureteric junction (PUJ) obstruction, using benzalkonium chloride (BCI) treatment of the upper urinary tract of rabbits, and thus further elucidate the pathophysiology of PUJ obstruction, the most common urinary tract obstruction in children. MATERIALS AND METHODS: Although various histological abnormalities have been described, PUJ obstruction may be functional. Defective innervation in PUJ has been suggested to be a major factor in the failure to transmit peristaltic waves across the PUJ. Previously established animal models of hydronephrosis deal mostly with surgical obstruction of the PUJ, which does not correlate with human congenital hydronephrosis. BCl has been used to ablate selectively neurones of the gastrointestinal myenteric plexus, which generated spastic segments with impaired peristalsis. Thus 12 rabbits were treated with BCl at the PUJ; the right upper urinary tract was dissected extraperitoneally and treated with a local application of 0.1% or 0.5% BCl (six each) for 15 min. The controls were four sham-operated animals treated with saline. The animals were assessed by intravenous urography (IVU) at 4 and 8 weeks after treatment, after which the animals were killed, the upper urinary tracts removed and whole-mounts prepared. Acetylcholinesterase (AChE) histochemistry, and neurofilament and tyrosine hydroxylase (TH) single-enzyme immunohistochemistry were used to detect the intrinsic innervation. RESULTS: None of the animals had hydronephrosis on the IVU or at death. AChE histochemistry, TH and neurofilament immunohistochemistry showed no or very few nerve fibres within the BCl-treated PUJs in both (0.1% and 0.5%) groups. After saline treatment there was normal development of the neuronal plexus within the submucosal, muscular and adventitial layers of the upper urinary tract. CONCLUSION: These results suggest that treatment with BCl is useful for ablating the intrinsic innervation in the upper urinary tract. Defective intrinsic innervation of the upper urinary tract did not lead to clinically or radiologically evident hydronephrosis. Further physiological studies using this model are needed to further elucidate the neuronal and myogenic influence on the development of PUJ obstruction.

Acetylcholine↗
PubMed2000

In vitro evaluation of open heart surgery tubing coated with heparin and lipid.

The aim of this work was to evaluate in vitro the tromboresistence, hemolysis tendency, platelet adhesion, cytotoxicity, physicochemical properties, and stability of open-heart tubing coated with fractionated heparin-benzalkonium chloride and/or lipid dipalmitoyl L-alpha-phosphatidylcholine (DPPC). The tendency for clot formation and platelet adhesion was greater in noncoated and lipid-coated tubing than in heparin-coated tubing. There were no significant differences between the hemolytic potentials of coated and noncoated tubing. The coatings were stable during the time of the experiment. The coatings did not present cytotoxicity and physicochemical alterations.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2001

Contact allergy to corticosteroids in patients using inhaled or intranasal corticosteroids for allergic rhinitis or asthma.

BACKGROUND: Patients using topically applied corticosteroids are at risk of developing allergic contact hypersensitivity. OBJECTIVE: To assess prevalence of allergic contact hypersensitivity reactions to inhaled or intranasal corticosteroids. METHODS: A prospective study of 30 adult patients using inhaled or intranasal corticosteroids for conditions such as allergic rhinitis was performed. We used epicutaneous patch testing to determine the prevalence of allergic contact hypersensitivity to corticosteroids and common additives (propylene glycol and benzalkonium chloride) in inhaled and nasal corticosteroid preparations in this population. RESULTS: Of 30 patients, 4 (13%) had positive patch test results. 3 (10%) were allergic reactions and 1 (3%) was an irritant reaction. Half of the reactions were to a corticosteroid (budesonide) and half were to a common preservative in nasal preparations (benzalkonium chloride). CONCLUSION: This study supports other clinical evidence that contact dermatitis/mucositis from inhaled or intranasal corticosteroid products can occur. The corticosteroids or added agents such as preservatives can be causative and may result in allergic or irritant reactions, which can be relevant to clinical symptoms.

Administration, Inhalation↗
PubMed2001

Benzalkonium chloride as a preservative in nasal solutions: re-examining the data.

Recent studies have suggested that benzalkonium chloride (BKC), an antimicrobial agent used as a preservative in nasal sprays, lacks deleterious effects on the nasal ciliated epithelium. Other data, including recent in vivo findings, suggest that BKC may, in fact, produce adverse clinical effects on human nasal tissue, including the aggravation of rhinitis medicamentosa. Toxic effects have also been reported. In light of the discrepancy between negative results and studies suggesting no safety concerns, we consider the possibility of problems in the design and methodology of some of the studies and in the interpretation of results. Clearly, further research is warranted to clarify the significance of conflicting findings. In the meantime, without conclusive data regarding BKC and the possibility of harmful effects, the use of nasal formulations without BKC might be a reasonable alternative.

Animals↗
PubMed2003

[The protective effect of dexpanthenol in nasal sprays. First results of cytotoxic and ciliary-toxic studies in vitro].

BACKGROUND: In Germany more than 60 million units of nasal decongestants are prescribed or sold over the counter. The cytotoxic and ciliary-toxic potential of alpha-sympathomimetic decongestants is well established. Furthermore, in many of the marketed products preservatives are added, predominantly benzalchonium-chloride, which can lead to a further alteration of cell- and ciliary function. Recently a protective effect of dexpanthenol was found for the human nasal mucosa. The objective of the present studies was to prove the hypothesis that dexpanthenol is able to neutralise the toxic effects of both alpha-sympathomimetic decongestants, in particular those of xylometazoline, and those of benzalconium-chloride. Therefore, systematic cytotoxic and ex vivo in vitro ciliary-toxic studies were performed. METHOD: After exposition to xylometazoline in concentrations of 0.1 % and 0.05 %, the influence of dexpanthenol (5 %) and benzalconium-chloride (0,01 %) was assessed by determination of a) cell growth of FL-cells of human amnion origin, and b) ciliary beat frequency of human nasal mucosa. All tests were performed placebo-controlled. RESULTS: Both hypotheses were confirmed. Dexpanthenol (5 %) reduces statistically significantly the concentration-dependent toxic effects of xylometazoline, and benzalchonium-cloride regarding cell growth and ciliary beat frequency (p < 0.001). The combination of xylometazoline with dexpanthenol, while benzalconium-chloride is eliminated, resulted in a further significant increase of cell growth and ciliary beat frequency (p < 0.001), similar to control. CONCLUSIONS: The additive application of dexpanthenol (5 %) with nasal decongestants and/or with preserved nasal sprays seems to be able to reduce the cell- and ciliary-toxic effects of these substances.

Administration, Intranasal↗
PubMed1990

[Benzalkonium chloride for vaginal contraception--the vaginal sponge].

From March 1986 to December 1987, a vaginal contraceptive, not yet commercially available in Germany, was studied in 56 women. The substance benzalconium chloride (BZC) was contained in vaginal sponges (n = 46), pessaries (n = 4) and cream (n = 6) at a dose rate of 1.18%. BZC is a surfactant of the ammonium series that ruptures the spermatozoal membrane. It is also a powerful bactericide and viricide. The advantages of the vaginal sponge (intercourse is safe immediately after insertion for the next 24 h and for multiple intercourses) made it pleasant for the women. The rate of transitory local side effects (16%) was acceptable. The vaginal contraception did not interfere with the sexual life. In 645 months of use 10 pregnancies occurred of which 9 happened with the sponge (PI 20.3). Its fixation before the cervix and the release of the spermicide is not reliable enough, so that we cannot recommend the sponge as a safe vaginal contraceptive.

Adult↗
PubMed1986

[Effect of cyclosporin A, dexamethasone and various preservatives on epithelial wound healing in the denervated guinea pig cornea].

In order to examine a possible connection between punctate keratopathy following keratoplasty and the various drugs used in postoperative treatment, denervation was performed in white Pirbright guinea pigs by corneal trepanation with a 6 mm trephine to a depth of 0.25 mm. One week later an iodine gas applicator was used to produce erosion in the cornea, which had healed in the meantime. Until the erosions healed, the corneas were photographed four times daily after fluorescein staining; the negatives were enlarged by projection and the erosions measured planimetrically. The linear regression method was used to calculate a compensating straight line and thus the hourly epithelial wound-healing surface (mm2/h) for each eye. This was 0.76 mm2/h in control eyes. Dexamethasone 0.1%, benzalconium chloride 0.01%, and chlorobutanol 0.2% did not significantly inhibit wound healing, while Spersadex (dexamethasone 0.1% + benzalconium chloride 0.01%) and Totocortin (dexamethasone 0.1 + chlorobutanol 0.2%) did. Polyvinyl alcohol (1.4% without preservative) significantly delayed epithelial wound healing. Cyclosporin A 2% (in castor oil) had no influence on epithelial wound healing.

Animals↗
PubMed1989

Thymine dimer formation as a probe of the path of DNA in and between nucleosomes in intact chromatin.

Photo-induced thymine dimer formation was used to probe nucleosome structure in nuclei. The distribution of thymine dimers in the nucleosome and recent studies of the structure of thymine dimer-containing DNA suggest that the rate of thymine dimer formation is affected by the direction and degree of DNA bending. This premise was used to construct a model of the path of DNA in the nucleosome, which has the following features. (i) There are four regions of sharp bending, two which have been seen previously by x-ray crystallography of the core particle. (ii) The DNA in H1-containing nucleosomes deviates from its superhelical path near the midpoint; this is not seen with H1-stripped chromatin. (iii) The internucleosomal (linker) DNA appears to be relatively straight.

Animals↗
PubMed1997

Cidofovir transport in the pigmented rabbit conjunctiva.

PURPOSE: To characterize cidofovir (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine) transport in the pigmented rabbit conjunctiva and to evaluate the formulation influence on its transport. METHODS: The excised pigmented rabbit conjunctiva was mounted in the modified Ussing chamber. Cidofovir transport was initiated by applying 3H-cidofovir to the donor compartment and assayed by measuring the radioactivity accumulated in the receiver fluid over 180 min. RESULTS: Cidofovir flux in the mucosal-to-serosal direction increased proportionally with drug concentration over the 0.01 to 1 mM range. Cidofovir transport (0.01 mM) at 37 degrees C in the mucosal-to-serosal direction was not significantly different from that in the opposite direction or from that at 4 degrees C. Hypotonicity (80 mOsm/kg), 0.5% EDTA, and 0.0125% benzalkonium chloride increased the apparent permeability coefficient of cidofovir 3, 21, and 49 times, respectively. This was accompanied by a corresponding 43%, 86%, and 96% reduction in the transconjunctival electrical resistance over 180 min. The reduction in transepithelial electrical resistance elicited by hypotonicity was reversible. There was a good correlation between apparent permeability coefficient and the transconjunctival conductance, suggesting that cidofovir may undergo paracellular passive diffusion in the conjunctiva. CONCLUSION: Cidofovir transport in the rabbit conjunctiva may be via paracellular passive diffusion. Formulation changes may improve cidofovir absorption from the conjunctival route.

Animals↗