Efficacy of oregano and rosemary essential oils to affect morphology and membrane functions of noncultivable sessile cells of Salmonella Enteritidis 86 in biofilms formed on stainless steel.

AIMS: This study evaluated the efficacy of essential oil from Origanum vulgare L. (oregano; OVEO) and Rosmarinus officinalis L. (rosemary; ROEO) to inactivate sessile cells of Salmonella enterica serovar Enteritidis 86 (SE86) in young and mature biofilms formed on stainless steel. METHODS AND RESULTS: Ultrastructural alterations and damage in different physiological functions caused by OVEO and ROEO in noncultivable sessile cells of SE86 were investigated using scanning electron microscopy and flow cytometry. OVEO (2·5 µl ml-1 ) and ROEO (40 µl ml-1 ) were effective to eradicate young and mature biofilms formed by SE86 sessile cells on stainless steel surfaces; however, the efficacy varied with exposure time. OVEO and ROEO caused alterations in morphology of SE86 sessile cells, inducing the occurrence of bubbles or spots on cell surface. OVEO and ROEO compromised membrane polarization, permeability and efflux activity in noncultivable SE86 sessile cells. These findings show that OVEO and ROEO act by a multitarget mechanism on SE86 membrane functions. CONCLUSIONS: ROEO and OVEO showed efficacy to eradicate SE86 sessile cells in preformed biofilms on stainless steel, displaying a time-dependent effect and multitarget action mode on bacterial cell membrane. SIGNIFICANCE AND IMPACT OF THE STUDY: The study provides for the first time the effects of OVEO and ROEO on morphology and physiological functions of noncultivable sessile cells of S. Enteritidis biofilms preformed on stainless steel surfaces.

Identification and molecular characterization of a Bacillus subtilis IS13 strain involved in the biodegradation of 4,5,6-trichloroguaiacol.

4,5,6-Trichloroguaiacol (4,5,6-TCG) is a recalcitrant organochlorine compound produced during pulp bleaching and a potential environmental hazard in paper mill effluents. We report here the identification by biochemical tests and molecular biological analysis, using 16S ribotyping, of a 4,5,6-TCG-degrading bacterium, identified as a strain of Bacillus subtilis that is most closely related according to the phylogenetic analysis to B. subtilis strain Lactipan (alignment score 99%). Biodegradation of 4,5,6-TCG by this organism in a mineral salts medium was shown to occur only when the inoculum was composed of cells in the stationary phase of growth and to be accelerated by an additional carbon source, such as glucose, sucrose, glycerol or molasses. An additional nitrogen source (as ammonium sulfate) did not affect the rate of 4,5,6-TGC removal. No plasmids were detected in the bacterial cells. This is the first strain of B. subtilis which degrades chlorophenols and shows that 4,5,6-TCG is not degraded by cometabolism and that the gene encoding this characteristic is probably located on the chromosome. The lack of requirement for additional nitrogen source, the ability to enhance biodegradation by adding cheap carbon sources such as molasses, and the fact the trait is likely to be stable since it is encoded on the cell chromosome, are all characteristics that make the organism an attractive possibility for treatment of wastes and environments polluted with organochlorine compounds.

Identification of heat stable protease of Klebsiella oxytoca isolated from raw milk.

AIMS: The aim of this study was to identify and characterize heat stable proteinases of psychrotrophic proteolytic bacteria isolated from raw milk. METHODS AND RESULTS: A strain of Klebsiella oxytoca producing a high proteolytic activity when cultured on milk was isolated. Maximum proteolytic activity was observed at the stationary phase during growth on milk or casein-peptone broth. The bacterium demonstrated the capability to grow at 7 degrees C, classified as psychrotrophic. The crude enzyme showed optimum activity at 37 degrees C, and pH 5.0 and 7.0. The proteinase was very resistant to heat, maintaining 74% of initial activity after incubation at 142 degrees C. CONCLUSIONS: A heat stable protease of a psychrotrophic strain of K. oxytoca was identified and partially characterized. SIGNIFICANCE AND IMPACT OF THE STUDY: Thermal stable proteases may constitute a serious problem to ultra-high temperature (UHT) processed milk, leading to undesirable physical and sensory alterations.

Análise de perigos e pontos críticos de controle para garantir a segurança alimentar em restaurante da Universidade Federal do Rio Grande do Sul / Analyse hazard and critical control points to guarantee the alimentar safety in restaurant of Universidade Federal do Rio Grande do Sul

Muitos restaurantes universitários brasileiros produzem significativas quantidades de refeiçöes, mesmo näo havendo condiçöes ideais para tanto. As freqüentes reduçöes de orçamento e a falta de treinamento dos funcionários cooperam ainda mais no detrimento da qualidade dos alimentos ali processados. Objetivou-se analisar perigos e identificar pontos críticos de controle (PCC), os quais podem ser utilizados em um sistema HACCP/APPCC (Hazard Analysis Critical Control Point ou Análise de Perigos e Pontos Críticos de Controle) como fonte de resoluçäo dos problemas diários que afetam a qualidade das refeiçöes produzidas. A investigaçäo de perigos e pontos críticos de controle foi conduzida no restaurante universitário n§3 da Universidade Federal do Rio Grande do Sul através de elaboraçäo de fluxogramas, análises visuais, físicas e microbiológicas durante os meses de temperatura pico (janeiro e junho) no veräo e inverno dos anos de 1997 e 1998, na cidade de Porto Alegre. Os resultados obtidos foram comparados a fim de evidenciar as diferenças de contaminaçäo dentro de condiçöes climáticas diferentes. Treinamentos periódicos, destinaçäo de recursos para a manutençäo e aquisiçäo de equipamentos e utensílios, assim como a implantaçäo completa do sistema HACCP/APPCC reduziriam sensivelmente a possibilidade de toxinfecçöes e a instabilidade imposta pelas condiçöes näo ideais de trabalho desses restaurantes.

Assessing and analysing contamination of a dairy products processing plant by Staphylococcus aureus using antibiotic resistance and PFGE.

A dairy product processing plant was studied for 2.5 years to examine contamination with Staphylococcus aureus and try to correlate the source of contamination. Cultures were submitted to an antibiotic susceptibility test (AST) and characterised by Pulsed-field Gel Electrophoresis (PFGE) analysis. Results showed that 35.2% (19/51) of food handlers were asymptomatic carriers of S. aureus, and that 90.4% (19/21) of raw milk sampled was contaminated. Staphylococcus aureus was isolated from only 10 samples among more than 3200 investigated dairy products. No S. aureus contamination was found on machinery. The AST analysis demonstrated sensitivity of tested S. aureus to oxacillin, cephalothin, vancomycin, gentamicin, and sulfamethoxazole/trimethoprim. AST analysis generated eight different phenotypic profiles, but did not allow us to identify the source of contamination in seven of ten final products. PFGE analysis proved to be a sensitive method as it generated 42 different DNA banding profiles among the 48 S. aureus investigated, demonstrating a lack of predominance of endemic strains in the plant, contrary to suggestions raised by antibiotic resistance typing. Based on PFGE genotyping, S. aureus strains isolated from four contaminated final products were similar to four S. aureus isolated from raw milk. Five final products contained S. aureus different from all other strains collected, and one showed similarity to a strain isolated from a food handler. These results suggest contamination by raw milk as the main source of contamination of the final dairy products.

High biodegradetion levels of 4, 5, 6-trichloroguaiacol by "Bacillus" sp. isolates from pupl mill effluent

An aerobic Gram positive spore-forming bacterium was isolated drom cellulose pulp mill effluent. This microorganism, identified as "Bacillus" sp. and named IS13, was able to rapdly degrade the organic chlorinateed compound 4, 5, 6-trichloroguaiacol (4, 5, 6-TCG) from a culture containing 50 mg/l, wich corresponds to about 3,0E4 times the concentration found in the organic chlorinated compound 4, 5, 6-TCG decreasing, the lack of by-products had shown by such analysis lead to verify the possibility of either adsorption of absorption of 4, 5, 6-TCG by the cells, instead of real biodegradation. There were no traces of 4, 5, 6-TCG. Plasmid isolation was attempted by using different protocols. The best results werw reached by CTAB method, but no plamid DNA was found in "Bacillus"sp. IS13. The results suggest that genes located at the bacterial chromossome might mediate the high decrease of 4, 5, 6-TCG. The importance of this work is that, in being a natural ocurring microorganism, "Bacillus" sp. IS13, can be used as inoculum in plant effluents to best organochlorinated compounds biodegradation.