Antimicrobial synergism against different lineages of methicillin-resistant Staphylococcus aureus carrying SCCmec IV.

AIM: To evaluate the synergistic activity of antimicrobial drugs against lineages of methicillin-resistant Staphylococcus aureus (MRSA) carrying SCCmec IV. The biofilm production and related genes were also detected. METHODS AND RESULTS: Forty two MRSA isolates were tested for biofilm production and related genes. Biofilm/biomass susceptibility to gentamicin (G), linezolid (L), rifampicin (R) and vancomycin (V) was determined for six isolates from three lineages prevalent in Rio de Janeiro hospitals in concentrations ranging from 0·25 to 64 µg ml(-1). Biomass was evaluated by microtitre plate test and number of viable cells (CFU cm(-2)) and inspected by epifluorescence microscopy. All isolates presented the icaA and sasG genes, but only 38% were biofilm producers. There were 50 and 45% biomass reductions when concentrations ≥4 µg ml(-1) of R or L and ≥16 µg ml(-1) of G or V, respectively, were used. Synergism tests produced a 55% biomass reduction with R(2µgml-1) + G(16µgml-1), R(2µgml-1) + L(2µgml-1), R(2µgml-1) + V(4µgml-1), and L(2µgml-1) + V(4µgml-1). Number of viable cells was reduced from 2 to 3 logs with R(2µgml-1) + L(2µgml-1) and R(2µgml-1) + V(4µgml-1). CONCLUSIONS: Synergisms involving R plus L and R plus V caused important reductions in biofilm/biomass and the number of viable cells. Drug combinations should be considered in the chemotherapies of MRSA-SCCmec IV infections. SIGNIFICANCE AND IMPACT OF THE STUDY: Biofilms in MRSA infections restrict the clinical choice of antimicrobials. Thus, knowledge of the best options for monotherapy and drug synergisms could improve clinical results.

Cinnamomum zeylanicum extract on the radiolabelling of blood constituents and the morphometry of red blood cells: in vitro assay.

Effects of Cinnamomum zeylanicum (cinnamon) on the labelling of blood constituents with technetium-99m(99mTc) and on the morphology of red blood cells were studied. Blood samples from Wistar rats were incubated with cinnamon extract for 1 hour or with 0.9% NaCl, as control. Labelling of blood constituents with 99mTc was performed. Plasma (P) and blood cells (BC), soluble (SF-P and SF-BC) and insoluble (IF-P and IF-BC) fractions were separated. The radioactivity in each fraction was counted and the percentage of radioactivity incorporated (%ATI) was calculated. Blood smears were prepared, fixed, stained and the qualitative and quantitative morphological analysis of the red blood cells was evaluated. The data showed that the cinnamon extract decreased significantly (p<0.05) the %ATI on BC, IF-P and IF-BC. No modifications were verified on shape of red blood cells. Cinnamon extracts could alter the labelling of blood constituents with 99mTc, and although our results were obtained with animals, precaution is suggested in interpretations of nuclear medicine examinations involving the labelling of blood constituents in patients who are using cinnamon.

The role of hydrodynamic stress on the phenotypic characteristics of single and binary biofilms of Pseudomonas fluorescens.

This study investigates the phenotype of turbulent (Re = 5,200) and laminar (Re = 2,000) flow-generated Pseudomonas fluorescens biofilms. Three P. fluorescens strains, the type strain ATCC 13525 and two strains isolated from an industrial processing plant, D3-348 and D3-350, were used throughout this study. The isolated strains were used to form single and binary biofilms. The biofilm physiology (metabolic activity, cellular density, mass, extracellular polymeric substances, structural characteristics and outer membrane proteins [OMP] expression) was compared. The results indicate that, for every situation, turbulent flow-generated biofilms were more active (p < 0.05), had more mass per cm(2) (p < 0.05), a higher cellular density (p < 0.05), distinct morphology, similar matrix proteins (p > 0.1) and identical (isolated strains -single and binary biofilms) and higher (type strain) matrix polysaccharides contents (p < 0.05) than laminar flow-generated biofilms. Flow-generated biofilms formed by the type strain revealed a considerably higher cellular density and amount of matrix polysaccharides than single and binary biofilms formed by the isolated strains (p < 0.05). Similar OMP expression was detected for the several single strains and for the binary situation, not dependent on the hydrodynamic conditions. Binary biofilms revealed an equal coexistence of the isolated strains with apparent neutral interactions. In summary, the biofilms formed by the type strain represent, apparently, the worst situation in a context of control. The results obtained clearly illustrate the importance of considering strain variation and hydrodynamics in biofilm development, and complement previous studies which have focused on physical aspects of structural and density differences.

Influence of biofilm composition on the resistance to detachment.

Bacillus cereus and Pseudomonas fluorescens were used to develop monoculture biofilms in a bioreactor rotating system using a stainless steel cylinder for biofilm formation. The biofilms were allowed to grow for 7 days, exposed continuously to a Reynolds number of agitation (ReA) of 2,400. Afterwards, the biofilms were characterised in terms of respiratory activity, amount of biomass, cellular density, cellular size and total and extracellular proteins and polysaccharides. The biofilm mechanical stability was assessed by sequential submission of the biofilms to increasing ReA, respectively, 4,000, 8,100, 12,100 and 16,100. The results showed that P. fluorescens biofilms were five times more active, had a higher amount of biomass, cellular density, a reduced cellular size and a four-fold higher amount of extracellular proteins and polysaccharides than B. cereus biofilms. The application of shear stress forces higher than the one under which the biofilm was formed (ReA = 2,400) caused biomass removal. The high percentage of removal occurred with the implementation of a ReA of 8,100 for both B. cereus and P. fluorescens biofilms. The total series of ReA did not give rise to total biofilm removal, as only about 76% of P. fluorescens biofilm mass and 53% of B. cereus biofilm mass were detached from the cylinders. This latter result evidences that B. cereus had a higher mechanical stability than P. fluorescens biofilms. The overall results demonstrate that P. fluorescens and B. cereus formed physiologically distinct biofilms, B. cereus biofilms mainly being constituted by cells and P. fluorescens biofilms largely constituted by extracellular proteins and polysaccharides. B. cereus biofilms had a substantially higher mechanical stability than P. fluorescens biofilms.

Probiotic supplementation affects IGF-1 and leptin levels in Nile tilapia hepatopancreatic tissue / Suplementação com probiótico afeta os níveis de IGF-1 e leptina no tecido hepatopancreático de tilápias-do-nilo

This work aimed to assess the effect of the probiotic strain, Lactobacillus plantarum, on the levels of leptin, IGF-1 and their receptors on the hepatopancreatic tissues of Nile tilapia (Oreochromis niloticus) and then correlate fish growth performance and gut microbiological parameters. Fish juveniles (±23g) were reared in a recirculation system with constant aeration and temperature (25°C). They were distributed into six polyethylene tanks (45L) and fed twice a day at 5% of the tank biomass with the respective diets: control (commercial diet without probiotic) and supplemented with L. plantarum inoculum (1 x 108 CFU mL-1), both in triplicate. After 30 days of feeding, L. plantarum-fed fishes showed greater weekly growth rate, final weight, and feed conversion rate, in addition to higher count of lactic-acid bacteria and lower count of pathogenic bacteria in the intestinal tract, when compared to the control group. The immunostaining intensity for IGF-1 and leptin hormones was lower after L. plantarum supplementation than in the control group, with no change in the level for receptors. This reduction could implicate important changes in fish metabolism and homeostasis.(AU)

O presente trabalho teve como objetivo avaliar o efeito da cepa probiótica Lactobacillus plantarum sobre os níveis de leptina, IGF-1 e seus receptores no tecido hepatopancreático de tilápia-do-nilo (Oreochromis niloticus) e correlacionar com o desempenho zootécnico e os parâmetros microbiológicos intestinais dos peixes. Juvenis de tilápia-do-nilo (±23g) foram distribuídos em seis tanques de polietileno (45L) conectados a um sistema de recirculação, com aeração e temperatura constantes (25°C). Os peixes foram alimentados duas vezes ao dia, a 5% da biomassa do tanque, com as respectivas dietas: controle (dieta comercial sem probiótico) e suplementada com L. plantarum (1 x 108 UFC mL-1), ambas em triplicata. Após 30 dias de cultivo, os peixes alimentados com L. plantarum apresentaram maiores ganho de peso semanal, peso final e conversão alimentar, bem como maior contagem de bactérias ácido-láticas e menor contagem de bactérias patogênicas no trato intestinal das tilápias alimentadas com dieta probiótica, em comparação ao grupo controle. A intensidade da imunomarcação para os hormônios IGF-1 e leptina foi menor com a suplementação de L. plantarum do que no grupo controle, sem alterar os níveis de seus receptores. Essa redução pode implicar mudanças importantes no metabolismo e na homeostase dos peixes.(AU)

Hematological profile of Astyanax bimaculatus under different offer of Lactobacillus sp / Perfil hematológico de Astyanax bimaculatus sob diferentes ofertas do Lactobacillus sp

The objective of this study was to evaluate the hematological and immunological parameters of yellowtail lambaris (Astyanax bimaculatus), fed with different frequencies of the probiotic (Lactobacillus spp.). Fishes were distributed into 20 experimental units and divided in five treatments: control (0%), 25%, 50%, 75% and 100% of probiotic supply. A higher presence of total leukocytes (47.70 103cell µl-1), lymphocytes (36.11 103cell µl-1) and monocytes (11.58 103cell µl-1) was verified in fish fed 100% of probiotic, showing a directly proportional ratio among the frequencies of the probiotic supply on the availability of circulating cells in the circulatory system (R² 094-0.97). Hematocrit (27.30-34.63%), hemoglobin (7.00-10.90g dl-1), mean corpuscular volume (4.21-5.45 10-5.pg), mean corpuscular hemoglobin (3.45-5.40 10-6.pg), mean corpuscular hemoglobin concentration, (2.99-4.35g dl-1), total protein (44.32-50.26mg ml-1) and total plasma immunoglobulin (27.96-34.08mg ml-1) did not diverge among treatments. The frequency of the probiotic supply interferes with the hematological profile, although lactic acid bacteria were present in the same concentrations in the intestinal tract, regardless of the probiotic supply, there was an increase in circulating leukocytes, especially lymphocytes and monocytes, in lambari fed probiotic with more frequency.(AU)

O objetivo do presente trabalho foi avaliar os parâmetros hematológicos e imunológicos do lambari-do-rabo-amarelo (Astyanax bimaculatus) alimentado com diferentes frequências de probiótico (Lactobacillus spp.). Os peixes foram distribuídos em 20 unidades experimentais e divididos em cinco tratamentos: controle (0%), 25%, 50%, 75% e 100% de frequência na suplementação probiótica. Alta presença de leucócitos totais (47,70 10³ células µ-1), linfócitos (36,11 10³ células µ-1) e monócitos (11,58 10³ células µ-1) em peixes alimentados com 100% de probiótico apresenta uma taxa diretamente proporcional entre as frequências da suplementação probiótica na disponibilidade das células no sistema circulatório (R² 094-0,97). Hematócrito (27,30-34,63%), hemoglobina (7,00-10,90g dL-¹), volume corpuscular médio (4,21-5,45 10-5.pg), hemoglobina corpuscular média (3,45-5,40 10-6.pg), concentração de hemoglobina corpuscular média (2,99-4,35g dl-1), proteína total (44,32-50,26mg ml-1) e imunoglobulina plasmática total (27,96-34,08mg ml-1) não divergiram entre os tratamentos. A frequência da suplementação probiótica interferiu no perfil hematológico. Embora as bactérias ácido láticas estejam presentes na mesma concentração no trato intestinal, independentemente da oferta de probiótico, houve um aumento na circulação de leucócitos, especialmente linfócitos e monócitos, nos lambaris alimentados com maior frequência.(AU)

Sex disparities determined by biometric and hematological measurements in Astyanax bimaculatus / [Disparidades sexuais determinadas por medições biométricas e hematológicas em Astyanax bimaculatus]

This study aimed to compare the body indexes and hematological characteristics between Astyanax bimaculatus males and females. Four hundred fish were randomly distributed into four polyethylene tanks (100 fish/unit) in a recirculation system and fed four times a day (3% of biomass). After 90 days, ten fish (five ♀ and five ♂) were removed to perform blood tests and to measure weight, height, total length, height/length ratio, condition factor and index determination: vicerosomatic (VSI), hepatosomatic (HSI), and gonadosomatic (GSI). The results showed a higher average weight (g) in females (12.32±0.71) compared to males (6.98±0.75), the same happened to height (cm) = (3.01±0.07) and (2.40±0.05), total length (cm) = (3.01±0.07) and (2.40±0.05), VSI (%) = (11.43±0.81) and (3.55±1.05), HSI (%) = (0.72±0.08) and (0.30±0.04), respectively. Mean corpuscular hemoglobin (pg) was higher in females (3.72±1.20) than in males (2.99±1.51). Regarding the number of thrombocytes (103.µL-1), there was an increase in males (25.71±3.91) compared to females (17.40±6.40).(AU)

O objetivo deste trabalho foi comparar os índices corporais e as características hematológicas entre machos e fêmeas de Astyanax bimaculatus. Quatrocentos peixes foram distribuídos aleatoriamente em quatro caixas de polietileno (100 peixes/unidade), em sistema de recirculação, e alimentados quatro vezes ao dia (3% da biomassa). Após 90 dias, 10 peixes (cinco ♀ e cinco ♂) foram retirados para realização das análises sanguíneas e para mensuração do peso, da altura, do comprimento total, da relação altura/comprimento, do fator de condição e da determinação dos índices: viscerossomático (IVS), hepatossomático (IHS) e gonadossomático (IGS). Os resultados mostraram um maior peso médio (g) nas fêmeas (12,32±0,71) em relação aos machos (6,98±0,75); o mesmo aconteceu para altura (cm) = (3,01± 0,07) e (2,40± 0,05), comprimento total (cm) = (3,01±0,07) e (2,40±0,05), IVS (%) = (11,43±0,81) e (3,55±1,05), IHS (%) = (0,72±0,08) e (0,30±0,04), respectivamente. Hemoglobina corpuscular média (pg) foi maior nas fêmeas (3,72±1,20) que nos machos (2,99±1,51). Em relação ao número de trombócitos (103/µL), houve um aumento nos machos (25,71± 3,91) em relação às fêmeas (17,40±6,40).(AU)

Supplementation of Curcuma longa hydrolate improves immunomodulatory response in Nile tilapia reared in a recirculation aquaculture system / [Suplementação de extrato aquoso de Curcuma longa aprimorando a resposta imunomoduladora em tilápias cultivadas em sistema de recirculação em aquicultura]

The objective of this study was to evaluate the effects of dietary supplementation with different doses of Curcuma longa hydrolate on the hematological, immunological and zootechnical parameters of Nile tilapia cultivated in a recirculation system (RAS). Nile tilapia (Oreochromis niloticus) were used, distributed in 16 polyethylene boxes, divided into four treatments: 0.0%; 2.5%; 7.5% and 10.0% of Curcuma longa hydrolate, in quadruplicate. After 45 days of treatment, four fish per experimental unit were anesthetized to remove blood aliquot for hematological and immunological analyzes and dissect the liver to evaluate the hepatosomatic index and final biometry. In the haematological analysis, the fish fed with 2.5% had a higher number of leukocytes, monocytes and lymphocytes than control, while the doses of 7.5% and 10.0% did not differ. Antimicrobial activity showed a significant decrease as the dose of C. longa hydrolate increased. The other hematological, immunological, hepatosomatic index and zootechnical data did not differ between treatments. Thus, supplementation of the hydrolate of Curcuma longa at a dosage of 2.5%, improved and maintained blood-immune homeostasis parameters in these animals, being suggested for further studies.(AU)

O objetivo deste estudo foi avaliar os efeitos da suplementação dietética com diferentes doses de hidrolato de Curcuma longa nos parâmetros hematológicos, imunológicos e zootécnicos da tilápia-do-nilo cultivada em sistema de recirculação. Utilizou-se tilápia- do-nilo (Oreochromis niloticus), distribuída em 16 caixas de polietileno, divididas em quatro tratamentos: 0,0%; 2,5%7,5% e 10,0% de hidrolato de Curcuma longa, em quadruplicata. Após 45 dias de tratamento, quatro peixes por unidade experimental foram anestesiados para remover uma alíquota sanguínea para análises hematológicas e imunológicas, e removeu-se o fígado para avaliar o índice hepatossomático e a biometria final. Na análise hematológica, os peixes alimentados com 2,5% apresentaram maior número de leucócitos, monócitos e linfócitos que no controle, enquanto as doses de 7,5% e 10,0% não diferiram. Por outro lado, a atividade antimicrobiana apresentou uma redução significativa à medida que a dose de hidrolato de C. longa aumentou. Os demais dados hematológicos, imunológicos, hepatossomáticos e zootécnicos não diferiram entre os tratamentos. Assim, a suplementação do hidrolato de Curcuma longa, na dose de 2,5%, melhorou os parâmetros hematoimunológicos e manteve a homeostase nesses animais, sendo sugerida para novos estudos.(AU)

Monitoring the effects of biocide treatment of Pseudomonas fluorescens biofilms formed under different flow regimes.

The effectiveness of glutaraldehyde (GTA), a very common biocide for controlling biofilms formed by Pseudomonas fluorescens on stainless steel slides, in laminar and turbulent flow, was investigated. Tests were performed using a concentration of biocide of 200 mg L(-1) and a range of exposure times. The GTA action was assessed by means of activity tests and dry weight of the biofilms. The physical stability of the biofilm without biocide application and after exposure to GTA for different periods of time was also studied and evaluated through the variation of the mass of the deposit after submission to different rotation velocities. The results showed that, in all the situations studied, biofilms were not controlled after the treatment with biocide, since they remained on the metal surface and were still active. The results also demonstrated that the physical stability of the biofilms increased with biocide application.

Comparison of two biocides--carbamate and glutaraldehyde--in the control of fouling in pulp and paper industry.

Formation of fouling deposits is a serious problem facing paper mills. Despite the search for alternative methods, chemical biocides still represent the chief countermeasure to control microbial growth and general fouling buid-up in pulp and paper mills. The purpose of this work was to determine the effect of two biocides (carbamate and glutaraldehyde) on both planktonic cells and fouling layers of a paper machine system. A flow system was used for the study of fouling accumulation in an industrial white water circuit. Both biocides proved to be more effective in reducing the microbial loading of the white water circuit than the deposit accumulated on the stainless steel surfaces. Carbamate, in contrast to glutaraldehyde, had the ability of promoting cell agglomeration since the microbial loading decreased much more when the white water, treated with carbamate, was filtered through a filter-linen. The retention of suspended cells in the cellulose fibres acquires major importance since it is obtained by using an already existing physical process (filtration), which strongly enhances the overall microbial reduction obtained with the addition of the carbamate, without increasing the economic costs. These results also suggest that the use of conventional retention agents in pulp and paper processes can be efficient in controlling unwanted microbial effects.

Action time and feed frequency of Lactobacillus plantarum for Nile tilapia / Tempo de ação e frequência alimentar do Lactobacillus plantarum para tilápia-do-nilo

O objetivo desta pesquisa foi avaliar o tempo de ação do Lactobacillus plantarum no trato intestinal, assim como em qual frequência esse probiótico deve ser oferecido para tilápia-do-nilo (Oreochomis niloticus). Quarenta e oito tilápias foram alimentadas com ou sem probiótico, durante 14 dias. Após esse período, os peixes foram esviscerados, e amostras do trato intestinal foram semeadas em ágar TCBS, cetrimide e MRS. Esse procedimento foi repetido dois, quatro e seis dias após o 14º dia. Depois disso, 252 tilápias foram divididas em quatro tratamentos, peixes alimentados com probiótico suplementado em 100%, 50%, 25% e 0% (controle) das alimentações. Após nove semanas, os índices zootécnicos foram avaliados. No dia zero, verificou-se maior concentração de bactérias ácido-lácticas e menor concentração de Vibrios spp. e de Pseudomonas spp. no trato intestinal dos alevinos alimentados com probiótico. Peixes alimentados com 100% e 50% das alimentações suplementadas com probiótico apresentaram melhores índices zootécnicos que os peixes alimentados com 25% de suplementação e sem suplementação. O L. plantarum atuou por quatro dias após a última alimentação, e, para obter os melhores índices, essa cepa deve ser suplementada em 50% das alimentações por dia para tilápia-do-nilo (O. niloticus).(AU)

Sucralose sweetener in vivo effects on blood constituents radiolabeling, red blood cell morphology and radiopharmaceutical biodistribution in rats.

Effects of sucralose sweetener on blood constituents labelled with technetium-99m ((99m)Tc) on red blood cell (RBC) morphology, sodium pertechnetate (Na(99m)TcO(4)) and diethylenetriaminepentaacetic acid labeled with (99m)Tc ((99m)Tc-DTPA) biodistribution in rats were evaluated. Radiolabeling on blood constituents from Wistar rats was undertaken for determining the activity percentage (%ATI) on blood constituents. RBC morphology was also evaluated. Na(99m)TcO(4) and (99m)Tc-DTPA biodistribution was used to determine %ATI/g in organs. There was no alteration on RBC blood constituents and morphology %ATI. Sucralose sweetener was capable of altering %ATI/g of the radiopharmaceuticals in different organs. These findings are associated to the sucralose sweetener in specific organs.

Multiplicação in vitro de segmentos apicais caulinares de segurelha (Satureja hortensis L. ) / In vitro multiplication of apical shoot segments of Summer Savory (Satureja hortensis L. )

O presente estudo teve por objetivo avaliar o efeito de BAP, na presença e ausência de ANA, sobre a multiplicação in vitro de segmentos apicais caulinares de Satureja hortensis. Os explantes foram isolados de plântulas germinadas in vitro e cultivados em meio nutritivo MS. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 2x5, correspondendo às concentrações de ANA (0 e 1 µM) e de BAP (0; 5; 10; 15 e 20 µM), com seis repetições, cada uma composta por três explantes. Para a porcentagem de explantes com brotações houve efeito significativo para o fator BAP, aumentando à medida que cresce a concentração da citocinina. A variável "número de brotos por explante" apresentou interação entre os fatores, havendo a maior formação de brotos na presença de ANA na faixa de 10 - 15 µM de BAP. Na presença da auxina, o maior valor ocorreu com 15 µM de BAP tendendo a diminuir independente da presença de ANA. O enraizamento dos segmentos apicais foi maior na presença de ANA e ausência de BAP, diminuindo com o aumento da citocinina. O número de folhas foi influenciado pela maior concentração de BAP sendo que a 15 µM foi observado o maior número, tendendo à queda com aumento da concentração. A concentração de 15 µM de BAP, independente de ANA, proporcionou os melhores resultados na multiplicação da espécie produzindo aumento de brotações e número de folhas, à exceção do enraizamento que foi influenciado pela auxina.

This study aimed to evaluate the effect of BAP in the presence and absence of NAA, on the in vitro multiplication of shoot apical segments of Satureja hortensis. The explants were isolated from seedlings germinated in vitro and cultured in nutrient medium MS. The experimental design was completely randomized in a 2x5 factorial arrangement, corresponding to the concentrations of NAA (0 and 1 µM) and BAP (0, 5, 10, 15 and 20 µM), with six replicates, each consisting of three explants. For the percentage of explants with shoots, there was no significant effect for the factor BAP, increasing as the concentration of BAP grows. The variable number of shoots per explant showed interaction between factors, with the highest shoot formation in the presence of NAA and BAP in the range of 10 -15 µM. In the presence of auxin, the highest value occurred with 15 µM BAP, tending to decline regardless of the presence of NAA. The rooting of the apical segments was higher in the presence of NAA and absence of BAP, decreasing with increasing cytokinin. Leaf number was influenced by the higher concentration of BAP, and the amount of 15 µMhadthe largest number, tending to decrease with increasing concentration. The concentration of 15 µM BAP, regardless of NAA, provided better results in the multiplication of the species, producing increased number of shoots and leaves, except for rooting, whichwas influenced by auxin.

Comparative antibacterial potential of selected aldehyde-based biocides and surfactants against planktonic Pseudomonas fluorescens.

The antimicrobial efficacy of two aldehyde-based biocides (glutaraldehyde, GTA, and ortho-phthalaldehyde, OPA) and two surfactants (cetyltrimethyl ammonium bromide, CTAB, and sodium dodecyl sulphate, SDS) was tested against planktonic Pseudomonas fluorescens. The antimicrobial effects were evaluated by respiratory activity as a measure of the oxygen uptake rate, adenosine triphosphate (ATP) release, outer membrane proteins (OMP) expression and cellular colour changes. The results were compared with the bacterial characteristics without chemical treatment. Tests in the presence of bovine serum albumin (BSA), in order to mimic a disinfection process in the real situation under dirty conditions, were performed according to the European Standard EN-1276. P. fluorescens was completely inactivated with OPA (minimum bactericidal concentration, MBC = 0.5 mM) and CTAB (MBC = 5 mM) and was resistant to GTA and SDS. Only CTAB promoted cellular disruption and consequent ATP release. The antimicrobial action of the chemicals tested was significantly reduced when BSA was introduced into the bacterial cultures, increasing markedly the MBC values. Additionally, the presence of BSA acted as a disruption protective agent when CTAB was applied and stimulated the bacterial respiratory activity when lower concentrations of SDS were tested. The OMP of the bacterial cells was affected by the application of both surfactants. OMP expression remained unaltered after biocide treatment. Bacterial colour change was noticed after treatment with biocides and surfactants. In summary, P. fluorescens was extremely resistant to GTA and SDS, with antimicrobial action being quenched markedly by the reaction with BSA.

Validation of respirometry as a short-term method to assess the efficacy of biocides.

This study shows that a short-term respirometric measurement based on the rate of oxygen uptake needed to oxidize glucose is a reliable and fast method to assess biocide efficacy against P. fluorescens cells. Respiratory activity using oxygen consumption rate, the determination of viable and nonviable cells using Live/Dead BacLight kit and colony formation units (CFU), were compared as indicators of the biocidal efficacy of ortho-phthalaldehyde (OPA). The results showed that determining the effect of OPA against P. fluorescens using the different methods leads to different conclusions. The minimum bactericidal concentration (MBC) was 80 mgl(-1), 100 mgl(-1) and 65 mgl(-1) respectively, using respiratory activity, viability using BacLight counts and culturability. The plate count method was shown to underestimate the biocidal action of OPA, whilst data from respirometry and viability using Live/Dead BacLight kit correlated strongly and were not statistically different when yellow cells were considered nonviable. Respirometry therefore represents an expeditious, non-destructive and accurate method to determine the antimicrobial action of biocides against aerobic heterotrophic bacteria.

A versatile reactor for continuous monitoring of biofilm properties in laboratory and industrial conditions.

AIMS: The understanding of the dynamics of surface microbial colonization with concomitant monitoring of biofilm formation requires the development of biofilm reactors that enable direct and real-time evaluation under different hydrodynamic conditions. METHODS AND RESULTS: This work proposes and discusses a simple flow cell reactor that provides a means to monitoring biofilm growth by periodical removing biofilm-attached slides for off-line, both non-destructive and destructive biofilm analyses. This is managed without the stoppage of the flow, thus reducing the contamination and the disturbance of the biofilm development. With this flow cell, biofilm growth and respiratory activity can be easily followed, either in well-defined laboratory conditions or in an industrial environment. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The reproducible and typical biofilm development curves obtained, validated this flow cell and confirmed its potential for different biofilm-related studies, which can include biocidal treatment.