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Screening of benzalkonium chloride resistance in Listeria monocytogenes strains isolated during cold smoked fish production.

AIMS: To determine the susceptibility to disinfectants and cross-resistance to antibiotics in Listeria monocytogenes strains isolated from fish products and the fish-processing environment. METHODS AND RESULTS: Minimal inhibitory concentration assessment, using the agar dilution method, showed 108 of 255 L. monocytogenes isolates with low susceptibility to benzalkonium chloride (BC), commonly used in food industries. Most of them are from raw products of farmed fish during processing, while the remaining resistant isolates were mainly from the environment and finished products irrespective of the fish species. Two BC-resistant isolates were resistant to ethidium bromide (EB). The conservation of resistance after plasmid curing suggested that the resistance genes are not plasmid associated. EB accumulation assays demonstrated that the two BC(R) EB(R) isolates used an efflux pump to expel these substrates whereas a different mechanism was probably used by the majority of the strains with BC(R) EB(S) pattern. No cross-resistance was found with antibiotics. CONCLUSIONS: This study highlights the difference in susceptibilities to BC for L. monocytogenes strains isolated from fish-processing plants and in resistance mechanisms to BC developed by these bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of BC resistant L. monocytogenes strains could contribute to their adaptation and so explained their survival and persistence in the fish-processing environment.

Anti-Bacterial Agents↗

Topical pharyngeal anesthesia does not improve upper gastrointestinal endoscopy in conscious sedated patients.

OBJECTIVE: We undertook this study to determine whether topical pharyngeal anesthesia with conscious sedation is superior to conscious sedation alone, with respect to procedure performance or tolerance in patients undergoing diagnostic upper gastrointestinal endoscopy. METHODS: Ninety-five patients undergoing diagnostic upper endoscopy with conscious sedation were randomized to receive either topical pharyngeal anesthesia with 2% tetracaine/14% benzocaine spray or no pharyngeal anesthesia. Conscious sedation was achieved in all patients using intravenous midazolam and meperidine. Patients were asked to rate their pretest anxiety, comfort during endoscopy, recollection of the procedure, and willingness to undergo subsequent examinations using a 100-mm visual analog scale. Additionally, they were asked to estimate procedure duration and rate their tolerance for topical pharyngeal anesthesia. All examinations were performed by two endoscopists who were blinded to whether or not patients had received pharyngeal anesthesia. Endoscopists were asked to determine whether they believed that patients had received topical pharyngeal anesthesia and to estimate ease of esophageal intubation and procedure performance using a 100-mm visual analog scale. Procedure duration and doses of midazolam and meperidine were measured. RESULTS: The two groups did not differ with respect to age, gender, and previous endoscopic history. There were no significant differences between the two groups with respect to pretest anxiety, procedural comfort, and willingness to undergo subsequent examinations. Patients receiving topical pharyngeal anesthesia rated it as moderately unpleasant. Endoscopists were able to discriminate patients who received pharyngeal anesthesia from those who did not with a sensitivity of 0.73 and a specificity of 0.59. There were no significant differences between the two groups with respect to ease of intubation, procedure performance, procedure duration, and dosing of midazolam or meperidine. CONCLUSIONS: In patients undergoing diagnostic upper endoscopy using intravenous midazolam and meperidine, the use of topical pharyngeal anesthesia does not improve patient tolerance or procedure performance. Elimination of this agent in the performance of diagnostic upper endoscopy will save time and money without adversely affecting patient care or outcomes.

Anesthesia, Local↗

Effects of antiglaucoma drugs on ocular surface.

Topical medications have a very important role in chronic glaucoma treatment. Long-term use of these medications can cause significant changes on ocular surfaces. In this study, the ocular surfaces of 20 control subjects (group I), 20 primary open-angle glaucoma patients (group II) treated (mean 21.20 +/- 1.32 months) with 0.50% timolol maleate, and 20 primary open-angle glaucoma patients (group III) treated (mean 21.70 +/- 1.34 months) with 0.50% timolol maleate + 1% dipivefrin hydrochloride were evaluated. Studied parameters included Schirmer's test, tear break-up time, conjunctiva impression cytology and goblet cell density. These results suggest that long-term applications of topical anti glaucoma medications damage the ocular surface.

Administration, Topical↗

Topical urea as a treatment for non-infectious keratopathy.

The purpose of this study was to evaluate topical urea ophthalmic ointment as an agent to promote epithelial healing. Corneal epitheliopathy and epithelial defects were chemically induced in rabbits. Urea ophthalmic ointment was administered to one eye and control ointment to the fellow eye. The rabbits were examined by a masked observer for eleven days and points were awarded for steps of improvement in their ocular surface disease. The eyes receiving the urea ointment improved an average of 5.73 points while the control eyes improved 4.2 points (p < 0.0001). In conclusion, topical urea dissolved in a bland ointment encourages corneal reepithelialization and limits epithelial damage after toxic injury to corneal epithelium.

Administration, Topical↗

Extrinsic dental stain caused by chlorhexidine and other denaturing agents.

Experiments were performed in a standardized rabbit model for examination of the potential of chlorhexidine and other denaturing agents to induce dental stain together with ferric ions. The studies supported the view that denaturation may be a major aspect of the mechanism of stain formation and that iron sulphide may be one important cause for extrinsic dental stain. Analytical microprobe analysis showed high amounts of Fe and S in the stain. The stain formation could be inhibited by SnF2, possibly by a red-ox reaction. Established stain could be removed by an oxidizing agent.

Animals↗

Effect of some irritants on human epidermal mitosis.

Studies on how irritant materials might induce epidermal hyperplasia were initiated by investigating their influence on epidermal mitosis. 5% hydrochloric acid, neat dimethyl acetamide and 1% benzalkonium chloride had no effect. 5% benzalkonium chloride, however, produced a 10-fold increase in mitotic activity, while a dose response curve was seen with sodium lauryl sulphate (SLS) peaking at 1%. 1% SLS produced a remarkably uniform response for this type of assay and it is suggested that it might provide a useful model for situations of increased epidermal cell turnover such as psoriasis. It is also noted that there was apparently no direct relationship between gross inflammation and the mitotic response.

Acetamides↗

Relationship between intensities of skin test reactions to glass-fibres and chemical irritants.

A total of 98 workers at a glass-wool factory were patch tested with glass-fibres and six chemical irritants. A rubbing test with the fibres, a Trafuril test and provocation of dermographism were also performed. The subjects with strong patch test reactions to one quality of fibres also reacted strongly to the other types of fibres but did not show an increased sensitivity to other tests. The subjects with intense skin reactions to rubbing with the fibres showed an increased skin reactivity to Trafuril. A tendency towards increased reactivity to the patch tests with fibres was found in persons with fair skin and blue eyes.

Adolescent↗

Does occupational exposure to glass-fibres increase the general skin reactivity to irritants?

A total of 33 workers at a glass-wool factory were tested (patch tests with glass-fibres and chemical irritants, epicutaneous tests with Trafuril and intracutaneous tests with histamine) before starting to work at the factory and then re-tested after at least 4 weeks of exposure to glass-fibres. No statistically significant differences in the intensity of the skin reactions before and after exposure were found. Thus no general increased irritancy of the normal skin was induced by the continuous exposure to glass-fibres.

Adolescent↗

Human cutaneous vulvar reactivity to irritants.

To better understand the cutaneous reactivity of vulvar skin, two chemical irritants were applied topically to 21 subjects. The forearm of each subject served as a comparative control. Test sites remained open and were read at 24 hours. A significantly increased response to the irritants was noted on the vulvar skin.

Administration, Topical↗

Conjunctivitis due to soft lens solutions.

In cases of conjunctivitis associated with the use of soft lenses, delayed hypersensitivity to disinfecting components of the used soft lens liquids has to be considered. In 7/15 patients, positive patch test reactions to merthiolate, chlorhexidine or the soaking solutions were observed. The significance of these findings is discussed.

Benzalkonium Compounds↗

An animal model for altering the irritability threshold of normal skin.

Theory behind conditioned hyperirritability (autoeczematization) predicts the lowering of the irritation threshold in the presence of a pre-existing dermatitis. We have attempted to develop an animal model that parallels the syndrome seen in man. Groups of 10 guinea pigs were shaved and depilated; irritation thresholds to benzalkonium chloride and trichloroacetic acid were determined using 1 cm diameter open patches. Reactions were scored 24 h later on the basis of erythema and induration. Animals having as little as 1.56 cm2 of skin acutely inflamed with a known irritant had lowered irritation thresholds to the same irritant on normal skin at remote sites (p less than 0.01). Mild irritation of a much larger surface area produced the same effect (p less than 0.01). More extensive, severe dermatitis did not lower the irritation threshold further. Acute dermatitis induced by a contact allergen (DNCB) lowered the irritation threshold of normal skin to the same level as that obtained with irritants (p less than 0.01). Induction of chronic cutaneous ulcers 3-4 cm in diameter lowered the irritation threshold of normal skin to the same point defined by the acute studies (p less than 0.01). These results indicate that an acute irritant or contact dermatitis, as well as chronic skin ulceration, may alter the reactivity of unaffected normal skin to exhibit a heightened response to irritation. This model appears to differ from that seen in humans, in that a more extensive or chronic dermatitis did not further heighten the susceptibility to irritation.

Animals↗