Immobilization of bacteriophage in wound-dressing nanostructure.

Opportunistic bacteria that cause life-threatening infections are still a central problem associated with a healthcare setting. Bacteriophage capsid immobilization on nanostructured polymers maximizes its tail exposure and looks promising in applications toward skin-infections as alternative to antibiotics standardly used. The main goal of this work was to investigate the covalent immobilization of vB_Pae_Kakheti25 bacteriophage capsid on polycaprolactone (PCL) nanofibers (non-woven textile), as a potential effective antimicrobial, laundry resistant and non-toxic dressing for biomedical use. Surface analyses showed that the immobilization of vB_Pae_Kakheti25 bacteriophage capsid on PCL nanofibres oriented bacteriophage tails to interact with bacteria. Furthermore, antimicrobial assays showed a very effective 6 log bacterial reduction, which was equivalent to 99.9999%, after immediate and 2 hours of contact, even following 25 washing cycles (due to covalent bond). The activity of PCL-vB_Pae_Kakheti25 against P. aeruginosa was immediate and its reduction was complete.

Surface adhesins and exopolymers of selected foodborne pathogens.

The ability of bacteria to bind different compounds and to adhere to biotic and abiotic surfaces provides them with a range of advantages, such as colonization of various tissues, internalization, avoidance of an immune response, and survival and persistence in the environment. A variety of bacterial surface structures are involved in this process and these promote bacterial adhesion in a more or less specific manner. In this review, we will focus on those surface adhesins and exopolymers in selected foodborne pathogens that are involved mainly in primary adhesion. Their role in biofilm development will also be considered when appropriate. Both the clinical impact and the implications for food safety of such adhesion will be discussed.

Staphylococcus epidermidis biofilms control by N-acetylcysteine and rifampicin.

Medical device-associated infections caused by Staphylococcus epidermidis usually involve biofilm formation and its eradication is particularly challenging. Although rifampicin has been proving to be one of the most effective antibiotics against S. epidermidis biofilms, its use as a single agent can lead to the acquisition of resistance. Therefore, we assessed the combined effect of rifampicin with N-acetylcysteine (NAC) known by its mucolytic effect, in the control of S. epidermidis biofilms. Biofilms of 2 S. epidermidis strains (9142 and 1457) were treated with 1x minimum inhibitory concentration (4 mg/mL) and 10x minimum inhibitory concentration (40 mg/mL) of NAC and 10 mg/L (peak serum) of rifampicin alone and in combination. NAC at 40 mg/L alone or in combination with rifampicin (10 mg/L) significantly reduced (4 log10) the number of biofilm cells. Considering their different modes of action, the association of NAC with rifampicin constitutes a promising therapeutic strategy in the treatment of infections associated to S. epidermidis biofilms.

Combined effect of linezolid and N-acetylcysteine against Staphylococcus epidermidis biofilms.

INTRODUCTION: Staphylococcus epidermidis is an organism commonly associated with infections caused by biofilms. Biofilms are less sensible to antibiotics and therefore are more difficult to eradicate. Linezolid and N-acetylcysteine (NAC), have demonstrated to be active against gram-positive microorganisms. Therefore and since linezolid and NAC have different modes of action, the main objective of this work was to investigate the single and synergistic effect of linezolid and NAC against S. epidermidis biofilms. METHODS: This work reports the in vitro effect of linezolid and NAC against S. epidermidis biofilms, treated with MIC (4mgml(-1)) and 10×MIC of NAC, and MIC (1µgml(-1)) and peak serum concentration (PS=18µgml(-1)) of linezolid alone and in combination. After exposure of S. epidermidis biofilms to linezolid and/or NAC for 24h, several biofilm parameters were evaluated, namely the number of cultivable cells [colony forming unit (CFU) enumeration], total biofilm biomass and cellular activity. RESULTS: When tested alone, NAC at 10×MIC was the most effective agent against S. epidermidis biofilms. However, the combination linezolid (MIC)+NAC (10×MIC) showed a synergistic effect and was the most biocidal treatment tested, promoting a 5log reduction in the number of biofilm viable cells. CONCLUSION: This combination seems to be a potential candidate to combat infections caused by S. epidermidis biofilms, namely as a catheter lock solution therapy.

Evaluation of the Antimicrobial Activity of Chitosan Nanoparticles against Listeria monocytogenes.

Chitosan is obtained from the deacetylation of chitin, and it is known to possess antimicrobial activity. It has attracted attention as it may be used for treating infections caused by different types of microorganisms due to its broad spectrum. Its application in the form of micro- or nanoparticles (CM/CN) has expanded its usage, as in this form, it retains its activity, and remain stable in aqueous solutions. However, inconsistencies in the results reported by different authors have been identified. In this communication, the antimicrobial activity of CN produced from different starting materials was tested against Listeria monocytogenes. It was observed that, even though all the starting materials were reported to have a molecular weight (MW) below 200 kDa and degree of deacetylation (DD) > 75%, the size of the CNs were significantly different (263 nm vs. 607 nm). Furthermore, these differences in sizes exerted a direct effect on the antimicrobial properties of the particles, as when testing the ones with the smallest size, i.e., 263 nm, a lower Minimum Inhibitory Concentration (MIC) was achieved, i.e., 0.04 mg/mL. Even though the largest particles, i.e., 607 nm, in individual experiments were able to achieve an MIC of 0.03 mg/mL, the results with CN presented great variation among replicates and up to 0.2 mg/mL were needed in other replicates. The starting material has a critical impact on the properties of the CN, and it must be carefully characterized and selected for the intended application, and MW and DD solely do not fully account for these properties.

Evaluation of antimicrobial activity of certain combinations of antibiotics against in vitro Staphylococcus epidermidis biofilms.

BACKGROUND & OBJECTIVES: Staphylococcus epidermidis is the most common pathogen associated with infections of surgical implants and other prosthetic devices owing to its adhesion and biofilm-forming ability on biomaterials surfaces. The objective of this study was to compare susceptibilities of biofilm-grown cells to single antibiotic and in combination with others to identify those that were effective against S. epidermidis biofilms. METHODS: Biofilms were grown in the MBEC™ assay system. The use of this methodology allowed a rapid testing of an array of antibiotics alone (eight) and in combination (25 double combinations). The antibacterial effect of all treatments tested was determined by colony forming units (cfu) enumeration method. RESULTS: The MBEC™ assay system produced multiple and reproducible biofilms of S. epidermidis. Although none of the antibiotics tested have demonstrated an antimicrobial effect (log reduction >3) against all S. epidermidis isolates biofilms, but combinations containing rifampicin showed in general a broader spectrum namely rifampicin-gentamicin and rifampicin-clindamycin. Levofloxacin in combination with rifampicin showed a killing effect against three isolates but failed to attain a bactericidal action against the other two. INTERPRETATION & CONCLUSIONS: Our findings showed that rifampicin should be a part of any antibiotic therapy directed against S. epidermidis biofilms. However, the efficient antibiotics combination might be dependent on S. epidermidis isolate being tested.

Farnesol in combination with N-acetylcysteine against Staphylococcus epidermidis planktonic and biofilm cells.

Staphylococcus epidermidis is the most frequent cause of nosocomial sepsis and catheter-related infections, in which biofilm formation is considered to be the main virulence mechanism. In biofilm environment, microbes exhibit enhanced resistance to antimicrobial agents. This fact boosted the search of possible alternatives to antibiotics. Farnesol and N-acetylcysteine (NAC) are non-antibiotic drugs that have demonstrated antibacterial properties. In this study, the effect of farnesol and NAC isolated or in combination (farnesol+NAC) was evaluated. NAC at 10 × MIC caused a total cell death in planktonic cells. On the other hand, S. epidermidis biofilms exhibited 4 log reduction in viable cell number after a 24h treatment with NAC at the former concentration. Our results demonstrated that there was a higher CFU log reduction of S. epidermidis planktonic cells when farnesol was combined with NAC at 1 × MIC relatively to each agent alone. However, these results were not relevant because NAC alone at 10 × MIC was always the condition which gave the best results, having a very high killing effect on planktonic cells and a significant bactericidal effect on biofilm cells. This study demonstrated that no synergy was observed between farnesol and NAC. However, the pronounced antibacterial effect of NAC against S. epidermidis, on both lifestyles, indicates the use of NAC as a potential therapeutic agent in alternative to antibiotics.

Chitosan Nano/Microformulations for Antimicrobial Protection of Leather with a Potential Impact in Tanning Industry.

Tanned leather can be attacked by microorganisms. To ensure resistance to bacteria on leather surfaces, protection solutions need to be developed, addressing both environmental issues and economic viability. In this work, chitosan nano/microparticles (CNP) and chitosan/silver nano/microstructures (CSNP), containing silver nanoparticles around 17 nm size, were incorporated into leather, obtained from the industrial process. Low loads of chitosan-based nano/microformulations, 0.1% mass ratio, resulted in total bacteria reduction (100%) after 2 h towards Gram-positive Staphylococcus aureus, both with CNP and CSNP coatings. Otherwise, comparable tests with the Gram-negative bacteria, Klebsiella pneumoniae, Escherichia coli, showed no significant improvement under the coating acidic conditions. The antimicrobial activity was evaluated by standard test methods: (1) inhibition halo and (2) dynamic contact conditions. The developed protection of leather either with CNP or CSNP is much higher than the one obtained with a simple chitosan solution.

Deep impact of the inactivation of the SecA2-only protein export pathway on the proteosurfaceome of Listeria monocytogenes.

Listeria monocytogenes presents a dimorphism associated to the SecA2 activity with cells having a normal rod shape or a dysmorphic elongated filamentous form. Besides variation of the cell and colony morphotype, this cell differentiation has profound ecophysiological and physiopathological implications with collateral effects on virulence and pathogenicity, biotope colonisation, bacterial adhesion and biofilm formation. This suggests the SecA2-only protein export could influence the listerial cell surface, which was investigated first by characterising its properties in L. monocytogenes wt and ΔsecA2. The degree of hydrophilicity and Lewis acid-base properties appeared significantly affected upon SecA2 inactivation. As modification of electrostatic properties would owe to modification in the composition of cell-surface proteins, the proteosurfaceome was further investigated by shotgun label-free proteomic analysis with a comparative relative quantitative approach. Following secretomic analysis, the protein secretion routes of the identified proteins were mapped considering the cognate transport and post-translocational maturation systems, as well as protein categories and subcellular localisation. Differential protein abundance profiles coupled to network analysis revealed the SecA2 dependence of 48 proteins, including some related to cell envelope biogenesis, translation and protein export, which could account for modifications of adhesion and surface properties of L. monocytogenes upon SecA2 inactivation. This investigation unravelled the profound influence of SecA2 activity on the cell surface properties and proteosurfaceome of L. monocytogenes, which provides advanced insights about its ecophysiopathology. SIGNIFICANCE: L. monocytogenes is a foodborne zoonotic pathogen and etiological agent of human listeriosis. This species presents a cellular dimorphism associated to the SecA2 activity that has profound physiopathological and ecophysiological implications with collateral effects on bacterial virulence and colonisation. To explore the influence of the SecA2-only protein export on the listerial cell, the surface properties of L. monocytogenes expressing or depleted of SecA2 was characterised by microelectrophoresis, microbial affinity to solvents and contact angles analyses. As modifications of hydrophilicity and Lewis acid-base electrostatic properties would owe to modification in the composition of cell-surface proteins, the proteinaceous subset of the surfaceome, i.e. the proteosurfaceome, was investigated further by shotgun label-free proteomic analysis. This subproteome appeared quite impacted upon SecA2 inactivation with the identification of proteins accounting for modifications in the cell surface properties. The profound influence of SecA2 activity on the cell surface of L. monocytogenes was unravelled, which provides advanced insights about its ecophysiopathology.

Effect of farnesol on structure and composition of Staphylococcus epidermidis biofilm matrix.

Staphylococcus epidermidis is the most frequent cause of nosocomial sepsis and catheter-related infections in which biofilm formation is considered to be one of the main virulence mechanisms. Moreover, their increased resistance to conventional antibiotic therapy enhances the need to develop new therapeutical agents. Farnesol, a natural sesquiterpenoid present in many essential oils, has been described as impairing bacterial growth. The aim of this study was to evaluate the effect of farnesol on the structure and composition of biofilm matrix of S. epidermidis. Biofilms formed in the presence of farnesol (300 µM) contained less biomass, and displayed notable changes in the composition of the biofilm matrix. Changes in the spacial structure were also verified by confocal scanning laser microscopy (CSLM). The results obtained by the quantification of extracellular polymers and by wheat germ agglutinin (WGA) fluorescent detection of glycoproteins containing ß(1→4)-N-acetyl-D: -glucosamine support the hypothesis that farnesol causes disruption of the cytoplasmic membrane and consequently release of cellular content.

In vitro activity of daptomycin, linezolid and rifampicin on Staphylococcus epidermidis biofilms.

Owing to their massive use, Staphylococcus epidermidis has recently developed significant resistance to several antibiotics, and became one of the leading causes of hospital-acquired infections. Current antibiotics are typically ineffective in the eradication of bacteria in biofilm-associated persistent infections. Accordingly, the paucity of effective treatment against cells in this mode of growth is a key factor that potentiates the need for new agents active in the prevention or eradication of biofilms. Daptomycin and linezolid belong to the novel antibiotic therapies that are active against gram-positive cocci. On the other hand, rifampicin has been shown to be one of the most potent, prevalent antibiotics against S. epidermidis biofilms. Therefore, the main aim of this study was to study the susceptibility of S. epidermidis biofilm cells to the two newer antimicrobial agents previously mentioned, and compare the results obtained with the antimicrobial effect of rifampicin, widely used in the prevention/treatment of indwelling medical device infections. To this end the in vitro activities of daptomycin, linezolid, and rifampicin on S. epidermidis biofilms were accessed, using these antibiotics at MIC and peak serum concentrations. The results demonstrated that at MIC concentration, rifampicin was the most effective antibiotic tested. At peak serum concentration, both strains demonstrated similar susceptibility to rifampicin and daptomycin, with colony-forming units (CFUs) reductions of approximately 3-4 log(10), with a slightly lower response to linezolid, which was also more strain dependent. However, considering all the parameters studied, daptomycin was considered the most effective antibiotic tested, demonstrating an excellent in vitro activity against S. epidermidis biofilm cells. In conclusion, this antibiotic can be strongly considered as an acceptable therapeutic option for S. epidermidis biofilm-associated infections and can represent a potential alternative to rifampicin in serious infections where rifampicin resistance becomes prevalent.

Denitrification of a landfill leachate with high nitrate concentration in an anoxic rotating biological contactor.

The denitrification performance of a lab-scale anoxic rotating biological contactor (RBC) using landfill leachate with high nitrate concentration was evaluated. Under a carbon to nitrogen ratio (C/N) of 2, the reactor achieved N-NO(3)(-) removal efficiencies above 95% for concentrations up to 100 mg N-NO(3)(-) l(-1). The highest observed denitrification rate was 55 mg N-NO(3)(-) l(-1) h(-1) (15 g N-NO(3)(-) m(-2) d(-1)) at a nitrate concentration of 560 mg N-NO(3)(-) l(-1). Although the reactor has revealed a very good performance in terms of denitrification, effluent chemical oxygen demand (COD) concentrations were still high for direct discharge. The results obtained in a subsequent experiment at constant nitrate concentration (220 mg N-NO(3)(-) l(-1)) and lower C/N ratios (1.2 and 1.5) evidenced that the organic matter present in the leachate was non-biodegradable. A phosphorus concentration of 10 mg P-PO(4)(3-) l(-1) promoted autotrophic denitrification, revealing the importance of phosphorus concentration on biological denitrification processes.

Evaluation of Fenton and ozone-based advanced oxidation processes as mature landfill leachate pre-treatments.

Fenton treatment (Fe(2+)/H(2)O(2)) and different ozone-based Advanced Oxidation Processes (AOPs) (O(3), O(3)/OH(-) and O(3)/H(2)O(2)) were evaluated as pre-treatment of a mature landfill leachate, in order to improve the biodegradability of its recalcitrant organic matter for subsequent biological treatment. With a two-fold diluted leachate, at optimised experimental conditions (initial pH 3, H(2)O(2) to Fe(2+) molar ratio of 3, Fe(2+) dosage of 4 mmol L(-1), and reaction time of 40 min) Fenton treatment removed about 46% of chemical oxygen demand (COD) and increased the five-day biochemical oxygen demand (BOD(5)) to COD ratio (BOD(5)/COD) from 0.01 to 0.15. The highest removal efficiency and biodegradability was achieved by ozone at higher pH values, solely or combined with H(2)O(2). These results confirm the enhanced production of hydroxyl radical under such conditions. After the application for 60 min of ozone at 5.6 g O(3)h(-1), initial pH 7, and 400 mg L(-1) of hydrogen peroxide, COD removal efficiency was 72% and BOD(5)/COD increased from 0.01 to 0.24. An estimation of the operating costs of the AOPs processes investigated revealed that Fe(2+)/H(2)O(2) was the most economical system (8.2 € m(-3)g(-1) of COD removed) to treat the landfill leachate. This economic study, however, should be treated with caution since it does not consider the initial investment, prices at plant scale, maintenance and labour costs.

Active natural-based films for food packaging applications: The combined effect of chitosan and nanocellulose.

This work aimed to evaluate the potential of chitosan/cellulose nanocrystals (CNC) films to be used as active pads for meat packages to prolong its shelf-life and preserve its properties over time. Several CNC concentrations (5, 10, 25, and 50 wt%) were tested and the films were produced by solvent casting. The developed samples were characterized by ATR-FTIR, TGA, FESEM, and XRD. The transparency, antimicrobial, barrier and mechanical properties were also assessed. Finally, the films' ability to prolong food shelf-life was studied in real conditions using chicken meat. CNC incorporation improved the thermal stability and the oxygen barrier while the water vapor permeability was maintained. An enhancement of mechanical properties was also observed by the increase in tensile strength and Young's modulus in chitosan/CNC films. These films demonstrated bactericidal effect against Gram-positive and Gram-negative bacteria and fungicidal activity against Candida albicans. Lastly, chitosan-based films decreased the growth of Pseudomonas and Enterobacteriaceae bacteria in meat during the first days of storage compared to commercial membranes, while chitosan/CNC films reduced the total volatile basic nitrogen (TVB-N), indicating their efficiency in retarding meat's spoilage under refrigeration conditions. This work highlights the great potential of natural-based films to act as green alternatives for food preservation.

Effect of farnesol on planktonic and biofilm cells of Staphylococcus epidermidis.

Staphylococcus epidermidis is now amongst the most important pathogenic agents responsible for bloodstream nosocomial infections and for biofilm formation on indwelling medical devices. Its increasing resistance to common antibiotics is a challenge for the development of new antimicrobial agents. Accordingly, the goal of this study was to evaluate the effect of farnesol, a natural sesquiterpenoid, on Staphylococcus epidermidis planktonic and biofilm cells. Farnesol displayed a significant inhibitory effect on planktonic cells. Small concentrations (100 muM) were sufficient to exhibit antibacterial effect on these cells. In biofilm cells the effect of farnesol was not so pronounced and it seems to be strongly dependent on the cells metabolic activity and amount of matrix. Interestingly, the effect of farnesol at 200 muM was similar to the effect of vancomycin at peak serum concentration either in planktonic or biofilm cells. Overall, the results indicate a potential antibacterial effect of farnesol against S. epidermidis, and therefore the possible action of this molecule on the prevention of S. epidermidis related infections.

Effect of batch and fed-batch growth modes on biofilm formation by Listeria monocytogenes at different temperatures.

The influence of Listeria monocytogenes (L. monocytogenes) biofilm formation feeding conditions (batch and fed-batch) at different temperatures on biofilm biomass and activity was determined. Biofilm biomass and cellular metabolic activity were assessed by Crystal Violet (CV) staining and 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT) colorimetric method, respectively. Live/Dead staining was also performed in order to get microscopic visualization of the different biofilms. Results revealed that at refrigeration temperature (4 degrees C) a higher amount of biofilm was produced when batch conditions were applied, while at higher temperatures the fed-batch feeding condition was the most effective on biofilm formation. Moreover, independently of the temperature used, biofilms formed under fed-batch conditions were metabolically more active than those formed in batch mode. In conclusion, this work shows that different growth modes significantly influence L. monocytogenes biofilm formation on abiotic surfaces as well as the metabolic activity of cells within biofilms.

The role of extracellular polymers on Staphylococcus epidermidis biofilm biomass and metabolic activity.

Staphylococcus epidermidis is now well established as a major nosocomial pathogen, associated with indwelling medical devices. Its major virulence factor is related with the ability to adhere to indwelling medical devices and form biofilms. In this study, the biofilm matrix of four S. epidermidis clinical isolates was extracted and the polysaccharides and proteins content was quantified. The results were correlated with the total biofilm biomass (determined by crystal violet assay) and cellular metabolic activity (evaluated with XTT reduction assay). According to the results, the exopolymers studied play an important role not only on structure and biofilm biomass but also on cellular activity. Thus, the strain forming biofilms with the highest level of polysaccharides (S. epidermidis 1457) also formed thicker biofilms but with the lowest metabolic activity. The protein concentration also varied among strains, with the biofilm matrix of S. epidermidis 9142 presenting a higher concentration of proteins comparing to the remaining strains. This fact indicates the different levels of importance that matrix proteins can hold on biofilm composition among strains albeit overall, it is suggested that extracellular protein production it is not a determinative factor for biofilm total biomass.

Effect of operating parameters on denitrification in an anoxic rotating biological contactor.

The presence of nitrate in water and wastewater is a serious environmental problem. Anoxic rotating biological contactors (RBC) are a promising novel technology for nitrate removal. In this study the effect of two carbon/nitrogen (C/N) molar ratios (1.5 and 3.0) on denitrification, using acetate as a carbon source, were investigated in an anoxic bench-scale RBC, treating synthetic wastewater. The effect of different hydraulic retention times (HRTs) and different nitrogen and carbon influent concentrations on the reactor performance, at constant C/N, were also analysed. The average removal efficiency in terms of nitrogen-nitrate was about 90.4% at C/N = 1.5, lowering to 73.7% at C/ N = 3.0. Considering carbon-acetate removal, overall efficiencies of 82.0% and 63.6% were attained at C/N ratios of 1.5 and 3.0, respectively. The increase in nitrogen-nitrate (from 50 to 100 mg N-NO3- L(-1)) and carbon-acetate influent concentrations and the decrease in HRT, keeping C/N constant, had a slight negative effect in terms of substrate removal. It was found that, for the tested conditions, the use of C/N = 1.5 is advantageous to denitrification. The anoxic RBC was significantly effective at reducing nitrate concentrations within a relatively short HRT. These reactors may be a feasible option for the treatment of nitrate-rich wastewaters.

Evaluation by Flow Cytometry of Escherichia coli Viability in Lettuce after Disinfection.

Foodborne outbreaks due to the consumption of ready-to-eat vegetables have increased worldwide, with Escherichia coli (E. coli) being one of the main sources responsible. Viable but nonculturable bacteria (VBNC) retain virulence even after some disinfection procedures and constitute a huge problem to public health due to their non-detectability through conventional microbiological techniques. Flow cytometry (FCM) is a promising tool in food microbiology as it enables the distinction of the different physiological states of bacteria after disinfection procedures within a short time. In this study, samples of lettuce inoculated with E. coli were subject to disinfection with sodium hypochlorite at free chlorine concentrations of 5, 10, 25, 50, and 100 mg·L-1 or with 35% peracetic acid at concentrations of 5, 10, 25, and 50 mg·L-1. The efficiency of these disinfectants on the viability of E. coli in lettuce was evaluated by flow cytometry with LIVE/DEAD stains. Results from this study suggest that FCM can effectively monitor cell viability. However, peracetic acid is more effective than sodium hypochlorite as, at half the concentration, it is enough to kill 100% of bacteria and always induces a lower percentage of VBNC. Finally, we can conclude that the recommended levels of chemical disinfectants for fresh fruit and vegetables are adequate when applied in lettuce. More importantly, it is possible to ensure that all cells of E. coli are dead and that there are no VBNC cells even with lower concentrations of those chemicals. These results can serve as guidance for lettuce disinfection, improving quality and the safety of consumption.

Adhesion to and viability of Listeria monocytogenes on food contact surfaces.

Listeria monocytogenes is an important pathogen responsible for major outbreaks associated with food products. Adhesion to surfaces leads to significant modifications in cell physiology. The aim of this work was to determine the adhesion ability of 10 isolates of L. monocytogenes to eight materials commonly used in kitchens and to evaluate the viability of the adhered cells. The materials assayed were stainless steel 304, marble, granite, glass, polypropylene from a bowl and from a cutting board, and two kinds of silestone. All L. monocytogenes strains attached to all surfaces, although to different extents. L. monocytogenes adhered most tightly to granite and marble, followed by stainless steel 304, glass, silestones, and finally polypropylene surfaces. Surfaces at the threshold between hydrophobicity and hydrophilicity, with high electron acceptor capability and a regular pattern of roughness, were more prone to attachment. Polypropylene surfaces displayed the highest percentage of viable bacteria (nearly 100%), whereas marble and granite had a lower percentage of cultivable cells, 69.5 and 78.7%, respectively. The lowest percentage of culturable bacteria was found on white silestone (18.5%). These results indicate that there are differences in adhered cell viability on different materials. Cell viability assays are important to better understand the cross-contamination process because only adhered bacteria that remain viable are responsible for postprocess contamination.