Tryptic Soy Broth Research Articles

Optimization of Streptococcus agalactiae Biofilm Culture in a Continuous Flow System for Photoinactivation Studies.

Streptococcus agalactiae is a relevant cause of neonatal mortality. It can be transferred to infants via the vaginal tract and cause meningitis, pneumonia, arthritis, or sepsis, among other diseases. The cause of therapy ineffectiveness and infection recurrence is the growth of bacteria as biofilms. To date, several research teams have attempted to find a suitable medium for the cultivation of S. agalactiae biofilms. Among others, simulated vaginal fluid has been used; however, biofilm production in this medium has been found to be lower than that in tryptic soy broth. We have previously shown that S. agalactiae can be successfully eradicated by photoinactivation in planktonic culture, but there have been no studies on biofilms. The aim of this study was to optimize S. agalactiae biofilm culture conditions to be used in photoinactivation studies. We compared biofilm production by four strains representing the most common serotypes in four different broth media with crystal violet staining. Then, we evaluated stationary biofilm culture in microtiter plates and biofilm growth in a CDC Biofilm Reactor® (BioSurface Technologies, Bozeman, MT, USA) under continuous flow conditions. Subsequently, we applied Rose Bengal-mediated photoinactivation to both biofilm models. We have shown that photoinactivation is efficient in biofilm eradication and is not cyto/phototoxic to human keratinocytes. We found conditions allowing for stable and repetitive S. agalactiae biofilm growth in continuous flow conditions, which can be successfully utilized in photoinactivation assays and potentially in all other antibacterial studies.

Antimicrobial and Antibiofilm Effect of ε-Polylysine against Salmonella Enteritidis, Listeria monocytogenes, and Escherichia coli in Tryptic Soy Broth and Chicken Juice.

ε-Polylysine (ε-PL) is a safe food additive that is used in the food industry globally. This study evaluated the antimicrobial and antibiofilm activity of antibacterial peptides (ε-PL) against food poisoning pathogens detected in chicken (Salmonella Enteritidis, Listeria monocytogenes, and Escherichia coli). The results showed that minimum inhibitory concentrations (MICs) ranged between 0.031–1.0 mg/mL, although most bacterial groups (75%) showed MICs of 1.0 mg/mL. The reduction in the cell viability of pathogens due to ε-PL depended on the time and concentration, and 1/2 × MIC of ε-PL killed 99.99% of pathogens after 10 h of incubation. To confirm biofilm inhibition and degradation effects, crystal violet assay and confocal laser scanning microscopy (CLSM) were used. The biofilm formation rates of four bacterial groups (Salmonella, Listeria, E. coli, and multi-species bacteria) were 10.36%, 9.10%, 17.44%, and 21.37% at 1/2 × MIC of ε-PL, respectively. Additionally, when observed under a CLSM, ε-PL was found to induce biofilm destruction and bacterial cytotoxicity. These results demonstrated that ε-PL has the potential to be used as an antibiotic and antibiofilm material for chicken meat processing.

Production of carotenoid sarcinaxanthin by Kocuria palustris isolated from Northeastern Brazil Caatinga soil and their antioxidant and photoprotective activities

This study aimed to produce carotenoids of two bacterial strains obtained and isolated from Caatinga soil in Northeastern Brazil and to evaluate their antioxidant and photoprotective activities. The morphological identification of bacteria was performed by Gram staining and molecularly confirmed through the 16S rRNA gene. The production of carotenoids was performed on two 2 3 factorial designs to analyze the influence of independent variables (temperature range, luminosity, agitation, spiral presence, and bacterial isolate type) for maximum carotenoid yield. The selected condition has been transferred to a bioreactor (10L). The identification of carotenoids was performed by liquid chromatography (HPLC) and mass spectrometry (LC-MS). Antioxidant activity was determined by inhibiting the β-carotene/linoleic acid system and the effectiveness as sunscreen was measured through its sun protection factor (SPF). The results revealed that the isolates FT-7.22 and FT-5.12 were identified as Kocuria palustris; producers of a rare C50 carotenoid sarcinaxanthin. This is the first report on the production of carotenoids by this species from the Caatinga Domain. The pigment that was obtained from the Tryptic Soy Broth (TSB) medium in the best conditions of the factorial designs (increased agitation, aeration, and light exposure) exhibited a significant increase in the carotenoid production. The isolated FT-7.22 reached a higher sarcinaxanthin concentration (112,480 μg/L), and it exhibited promising antioxidant (76.53 ± 0.09%) and photoprotective activities (SPF = 9.36 ± 0.52). This study demonstrated the ability of K. palustris to produce carotenoid sarcinaxanthin with antioxidant and photoprotective activities so that it can be applied in cosmetic formulations. How to cite: Mendes-Silva TCD, Vidal EE, de Souza RFR, et al. Production of carotenoid sarcinaxanthin by Kocuria palustris isolated from Northeastern Brazil Caatinga soil and their antioxidant and photoprotective activities. Electron J Biotechnol 2021;53. https://doi.org/10.1016/j.ejbt.2021.05.004

MP57-20 EVALUATION OF GRAM POSITIVE AND GRAM NEGATIVE BACTERIA IN A NOVEL IN VITRO BIOFILM MODEL OF PENILE PROSTHESIS

You have accessJournal of UrologySexual Function/Dysfunction: Surgical Therapy (MP57)1 Sep 2021MP57-20 EVALUATION OF GRAM POSITIVE AND GRAM NEGATIVE BACTERIA IN A NOVEL IN VITRO BIOFILM MODEL OF PENILE PROSTHESIS Manish Narasimman, Gregory Plano, Jesse Ory, Sara Schesser Bartra, and Ranjith Ramasamy Manish NarasimmanManish Narasimman More articles by this author , Gregory PlanoGregory Plano More articles by this author , Jesse OryJesse Ory More articles by this author , Sara Schesser BartraSara Schesser Bartra More articles by this author , and Ranjith RamasamyRanjith Ramasamy More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002087.20AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Infection is the most feared complication of inflatable penile prosthesis (IPP), often necessitating complete removal. Late infection after IPP insertion is thought to be due to the slow formation of a biofilm. Understanding and preventing biofilm formation would be a breakthrough in preventing IPP infections. We aimed to develop an in vitro model to compare formation and growth of biofilms on penile implants by bacteria commonly associated with infection. METHODS: Sterile IPPs (Coloplast® Titan) were cut into rings and incubated with S. epidermidis, S. aureus, P. aeruginosa, or K. pneumoniae cultures in tryptic soy broth (TSB) for a 4 h attachment period, and then in only TSB for 120 h. We utilized a published and validated method to measure biofilm mass. Rings were then dipped in deionized water to wash off additional bacteria and either fixed with ethanol (EtOH) or not treated further (no fix). Fixing was employed to preserve biofilm on the rings that otherwise may have been lost during crystal violet staining. Biofilm formation was measured with a spectrophotometer (OD570) after crystal violet staining. RESULTS: All bacteria formed substantial biofilm on implant rings as measured by OD570. As expected, the gram-negative bacteria, P. aeruginosa and K. pneumoniae produced significantly more biofilm than the gram-positive S. epidermidis and S. aureus. Interestingly, P. aeruginosa formed the most biofilm by at least a factor of 6 in both testing conditions. The ethanol fixing condition produced more consistent results for the crystal violet assay. CONCLUSIONS: Our novel in vitro model of biofilm formation of penile implants can be used in future studies to evaluate the effect of different antibiotic dips and anti-infective capacity of precoated implants against different bacteria. Our findings suggest gram-negative bacteria form faster and a greater quantity of biofilm on penile implants as compared to gram-positives. P. aeruginosa displayed the strongest predilection to form biofilm on implants compared to all other bacteria studied, and could be investigated as a specific target to reduce delayed post-operative IPP infections. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e987-e987 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Manish Narasimman More articles by this author Gregory Plano More articles by this author Jesse Ory More articles by this author Sara Schesser Bartra More articles by this author Ranjith Ramasamy More articles by this author Expand All Advertisement Loading ...

Use of 2-hydroxy-4-(methylthio)-butanoic acid to inhibit Salmonella and Listeria in raw meat for feline diets and palatability in domestic cats.

While the raw pet food market continues to grow, the risk of bacterial contamination in these types of diets is a major concern, with Salmonella enterica and Listeria monocytogenes being the most frequently associated pathogens in raw pet food product recalls. dl-Methionine is included in some commercial feline kibble and canned diets to improve protein quality; however, an alternative to this is a liquid methionine supplement, 2-hydroxy-4-(methylthio)-butanoic acid (HMTBa), which is also an organic acid. 2-Hydroxy-4-(methylthio)-butanoic acid has previously demonstrated similar efficacy to formic acid against pathogens in a liquid environment and may be a good candidate to inhibit S. enterica and L. monocytogenes in raw ground meat. First, the minimum inhibitory concentration and minimum bactericidal concentration of HMTBa against these pathogens under laboratory growth conditions were determined by measuring growth of pathogens over 36 h when exposed to 10 concentrations of HMTBa (0.10% to 1.00%) mixed with tryptic soy broth. 2-Hydroxy-4-(methylthio)-butanoic acid included at ≥0.50% was bactericidal to S. enterica and L. monocytogenes (P < 0.05). Next, five levels of HMTBa (0.50% to 1.25%) were included in raw ground meat mixtures inoculated with cocktails of S. enterica or L. monocytogenes, and contamination levels were determined at four timepoints: immediately, and after refrigerated storage (4 °C) at 24, 48, and 72 h after removal from freezer (24 h at -20 °C). 2-Hydroxy-4-(methylthio)-butanoic acid included as 1.25% of the meat mixture reduced S. enterica and L. monocytogenes compared with the control (P < 0.05); however, it did not result in total kill of either of these pathogens. Following this, feeding behaviors of seven domestic cats were assessed when offered a raw chicken diet treated with or without 1.25% HMTBa for 5 d each, after which a 2-d 2-choice preference test was conducted. Cats demonstrated a preference for raw diets without HMTBa, but still readily consumed diets with 1.25% HMTBa, suggesting that such a diet was still palatable to them.

Identification of Bacteria Associated with Post-Operative Wounds of Patients with the Use of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Approach.

The bacterial infection of post-operative wounds is a common health problem. Therefore, it is important to investigate fast and accurate methods of identifying bacteria in clinical samples. The aim of the study was to analyse the use of the MALDI-TOF MS technique to identify microorganism wounds that are difficult to heal. The most common bacteria are Escherichia coli, Staphylococcus spp., and Enterococcus spp. We also demonstrate the effect of culture conditions, such as the used growth medium (solid: Brain Heart Infusion Agar, Mueller Hilton Agar, Glucose Bromocresol Purple Agar, and Vancomycin Resistance Enterococci Agar Base and liquid: Tryptic Soy Broth and BACTEC Lytic/10 Anaerobic/F), the incubation time (4, 6, and 24h), and the method of the preparation of bacterial protein extracts (the standard method based on the Bruker guideline, the Sepsityper method) to identify factors and the quality of the obtained mass spectra. By comparing the protein profiles of bacteria from patients not treated with antibiotics to those treated with antibiotics based on the presence/absence of specific signals and using the UniProt platform, it was possible to predict the probable mechanism of the action of the antibiotic used and the mechanism of drug resistance.

Biofilm Effectivity of Ethanol Extracts (Casuarina equisetifolia) Leaves of the Bacteria Enterococcus faecalis

Background: Enterococcus faecalis is one of the bacteria that can form biofilms that can cause persistent endodontic infections. Biofilm is the unity of microbial cell surface surrounded by a matrix of extracellular polymeric substances (EPS). The ethanol extracts of Casuarina equisetifolia leaves are known to have potentially bioactive compounds as antibacterials such as flavonoids, saponins, tannins, phenols, and alkaloids. Objective: To determine the power antibiofilm ethanol extracts of Casuarina equisetifolia leaves at multiple concentrations of the bacteria Enterococcus faecalis. Methods: This study is an experimental research design post-test only control group design. The sample divided into 5 groups consisted of positive control Enterococcus faecalis in media Trypticase Soy Broth (TSB)+DMSO 1%, and 4 treatment groups of ethanol extracts of Casuarina equisetifolia leaves a concentration of 0,5%, 1%, 1,5%, and 2%. Biofilm is made using Enterococcus faecalis ATCC 29212 bacteria were cultured on TSB media were incubated for 1x24 hours. 0,1 ml of the bacteria Enterococcus faecalis with a concentration of 106 put on a plate micro titter then done using crystal violet staining. Biofilm-checked by measuring optical density (OD) values ​​using the ELISA reader. Data analysis used Kruskal-Wallis followed by Mann-Whitney test. Results: The ethanol extracts Casuarina equisetifolia leaves on the growth of Enterococcus faecalis bacteria indicate the presence of power antibiofilm. The results mean % mortality of bacteria (p&lt;0.05) were significant in all groups that have the power antibiofilm effectiveness as against the growth of bacteria Enterococcus faecalis. Conclusion: The ethanol extracts Casuarina equisetifolia leave have antibiofilm power against bacterial growth Enterococcus faecalis.&#x0D;

Characterization of biofilm formation and reduction of hexavalent chromium by bacteria isolated from tannery sludge

Biofilm formation ability of bacteria makes them potential in the field of tannery effluent treatment. However, the hazardous nature of effluent and environmental conditions may disturb the biofilm formation ability of bacteria which ultimately affects their effluent treatment efficiency. Accordingly, we isolated and characterized biofilm-forming bacteria Bacillus vallismortis (MT027009), Bacillus haynesii (MT027008), and Alcaligenes aquatilis (MT027005) from tannery sludge and examined them for biofilm formation under variable environmental conditions. Biofilm formation in tryptic soy broth (TSB) at different incubation times (24–120 h) revealed that the biofilm formation activity of the strain B. haynesii was not affected by incubation time, whereas the increase in biofilm formation was observed in the case of B. vallismortis (28 %) and A. aquatilis (52 %) after 48 h. The medium pH (pH 5.0–9.0) had a limited effect on biofilm formation except in the case of A. aquatilis at pH 5.0 (94 %) and pH 9.0 (80 %). Furthermore, compared to the controls (only TSB), the strains B. vallismortis, B. haynesii, and A. aquatilis showed enhanced biofilm formation in undiluted tannery effluent (28, 33, and 21 %) and 25 mg L−1 Cr(VI) (23 %, 48 % 32 %). The biofilm structure was influenced by Cr(VI) as revealed by scanning electron microscopy (SEM) analysis. The results of Cr(VI) bioreduction studies suggest that bacterial biofilm (60–99 %) has a greater potential to remove Cr(VI) than planktonic cells (43–94 %). The results of the study provide important data on biofilm formation by indigenous bacteria in effluent environment conditions, making them potential isolates for tannery effluent treatment.

The First Report of Bacteriocin Production by the Bacillus coagulans IS2 and its Antibacterial Effects

Bacillus coagulans is a probiotic bacterium with high beneficial effects on human health. The present research was performed to assess the antimicrobial effects of bacteriocin extracted from B. coagulans IS2 against different food-borne bacteria. B. coagulans IS2 was cultured on tryptic soy broth and incubated for 24 h at 37°C. Then, bacteria were sub-cultured on Man, Rogosa, Sharpe (MRS) broth. Produced bacteriocin was extracted from the MRS culture of B. coagulans IS2 by 70% ammonium sulphate. Escherichia coli, Salmonella enterica, and Listeria monocytogenes were cultured on Mueller Hinton Agar. Then, two separate 6 mm wells were created and filled with 200 µL of extracted bacteriocin. Presence of growth inhibition zones around wells weas considered as antimicrobial effect. The molecular weight of the bacteriocin was assessed by the Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The SDS-PAGE analysis showed presence of low molecular weight protein (

Relationship of Growth Conditions to Desiccation Tolerance of Salmonella enterica, Escherichia coli, and Listeria monocytogenes

Growth on solid media as sessile cells is believed to increase the desiccation tolerance of Salmonella enterica. However, the reasons behind increased resistance have not been well explored. In addition, the same effect has not been examined for other foodborne pathogens such as pathogenic Escherichia coli or Listeria monocytogenes. The purpose of this research was twofold: first, to determine the role of oxygenation during growth on the desiccation resistance of S. enterica, E. coli, and L. monocytogenes, and second, to determine the effect of sessile versus planktonic growth on the desiccation resistance of these pathogens. Three different serotypes each of Salmonella, E. coli, and L. monocytogenes were cultured in Trypticase soy broth with 0.6% yeast extract (TSBYE), with (aerobic) shaking or on TSBYE with agar under either aerobic or anaerobic conditions and harvested in the stationary phase. After adding cell suspensions to cellulose filter disks, pathogen survival was determined by enumeration before drying (0 h) and after drying for 24 h. Results showed statistical differences in harvested initial populations before drying. For Salmonella, a correlation was found between high initial population and greater survival on desiccation (P = 0.05). In addition, statistical differences (P ≤ 0.05) between survival based on growth type were identified. However, differences found were not the same for the three pathogens, or between their serotypes. In general, Salmonella and E. coli desiccation resistance followed the pattern of aerobic agar media ≥ liquid media ≥ anaerobic agar media. For L. monocytogenes serotypes, resistance to desiccation was not statistically different based on mode of growth. These results indicate growth on solid media under aerobic conditions is not always necessary for optimal desiccation survival, but may be beneficial when the desiccation resistance of the test serotype is unknown.

The heat resistance of spores from biofilms of Bacillus cereus grown in tryptic soy broth and milk

Bacillus cereus is a concern for the dairy industry due to the biofilm and spore formation during the manufacture of dairy products, causing contamination in the final products. Biofilm spores of all tested isolates showed a significantly higher (P < 0.05) or statistically comparable D90° value than their planktonic spores. The dipicolinic acid (DPA) content was measured and suggested not responsible for the differences in D90° values observed. The intracellular structure of spores was observed under transmission electron microscopy, showing a clearly defined circular coat for biofilm spores while an irregular-shaped coat was observed for planktonic spores. This is the first manuscript considering factors including biofilm formation, DPA content and spore structure in milk. This suggests more severe heat treatments are needed to control B. cereus spores from biofilms in the dairy industry compared with spores from planktonic cultures without the presence of milk.

Removal of Mixed-Species Biofilms Developed on Food Contact Surfaces with a Mixture of Enzymes and Chemical Agents.

Sanicip Bio Control (SBC) is a novel product developed in Mexico for biofilms’ removal. The aims of this study were to evaluate (i) the removal of mixed-species biofilms by enzymatic (protease and α-amylase, 180 MWU/g) and chemical treatments (30 mL/L SBC, and 200 mg/L peracetic acid, PAA) and (ii) their effectiveness against planktonic cells. Mixed-species biofilms were developed on stainless steel (SS) and polypropylene B (PP) in whole milk (WM), tryptic soy broth (TSB) with meat extract (TSB+ME), and TSB with chicken egg yolk (TSB+EY) to simulate the food processing environment. On SS, all biofilms were removed after treatments, except the enzymatic treatment that only reduced 1–2 log10 CFU/cm2, whereas on PP, the reductions ranged between 0.59 and 5.21 log10 CFU/cm2, being the biofilms developed in TSB+EY being resistant to the cleaning and disinfecting process. Higher reductions in microbial load on PP were reached using enzymes, SBC, and PAA. The employed planktonic cells were markedly more sensitive to PAA and SBC than were the sessile cells. In conclusion, biofilm removal from SS can be achieved with SBC, enzymes, or PAA. It is important to note that the biofilm removal was strongly affected by the food contact surfaces (FCSs) and surrounding media.

Volatile Compounds From Bacillus, Serratia, and Pseudomonas Promote Growth and Alter the Transcriptional Landscape of Solanum tuberosum in a Passively Ventilated Growth System

The interaction of an array of volatile organic compounds (VOCs) termed bacterial volatile compounds (BVCs) with plants is now a major area of study under the umbrella of plant-microbe interactions. Many growth systems have been developed to determine the nature of these interactions in vitro. However, each of these systems have their benefits and drawbacks with respect to one another and can greatly influence the end-point interpretation of the BVC effect on plant physiology. To address the need for novel growth systems in BVC-plant interactions, our study investigated the use of a passively ventilated growth system, made possible via Microbox® growth chambers, to determine the effect of BVCs emitted by six bacterial isolates from the genera Bacillus, Serratia, and Pseudomonas. Solid-phase microextraction GC/MS was utilized to determine the BVC profile of each bacterial isolate when cultured in three different growth media each with varying carbon content. 66 BVCs were identified in total, with alcohols and alkanes being the most abundant. When cultured in tryptic soy broth, all six isolates were capable of producing 2,5-dimethylpyrazine, however BVC emission associated with this media were deemed to have negative effects on plant growth. The two remaining media types, namely Methyl Red-Voges Proskeur (MR-VP) and Murashige and Skoog (M + S), were selected for bacterial growth in co-cultivation experiments with Solanum tuberosum L. cv. ‘Golden Wonder.’ The BVC emissions of Bacillus and Serratia isolates cultured on MR-VP induced alterations in the transcriptional landscape of potato across all treatments with 956 significantly differentially expressed genes. This study has yielded interesting results which indicate that BVCs may not always broadly upregulate expression of defense genes and this may be due to choice of plant-bacteria co-cultivation apparatus, bacterial growth media and/or strain, or likely, a complex interaction between these factors. The multifactorial complexities of observed effects of BVCs on target organisms, while intensely studied in recent years, need to be further elucidated before the translation of lab to open-field applications can be fully realized.

Staphylococcal Biofilm on the Surface of Catheters: Electron Microscopy Evaluation of the Inhibition of Biofilm Growth by RNAIII Inhibiting Peptide.

Staphylococcus aureus and coagulase-negative staphylococci (CoNS) have become the main causative agents of medical device-related infections due to their biofilm-forming capability, which protects them from the host’s immune system and from the action of antimicrobials. This study evaluated the ability of RNA III inhibiting peptide (RIP) to inhibit biofilm formation in 10 strains isolated from clinical materials, including one S. aureus strain, two S. epidermidis, two S. haemolyticus, two S. lugdunensis, and one isolate each of the following species: S. warneri, S. hominis, and S. saprophyticus. The isolates were selected from a total of 200 strains evaluated regarding phenotypic biofilm production and the presence and expression of the ica operon. The isolates were cultured in trypticase soy broth with 2% glucose in 96-well polystyrene plates containing catheter segments in the presence and absence of RIP. The catheter segments were observed by scanning electron microscopy. The results showed inhibition of biofilm formation in the presence of RIP in all CoNS isolates; however, RIP did not interfere with biofilm formation by S. aureus. RIP is a promising tool that might be used in the future for the prevention of biofilm-related infections caused by CoNS.

Immobilized Reporter Phage on Electrospun Polymer Fibers for Improved Capture and Detection of Escherichia coli O157:H7

Escherichia coli O157:H7 is a foodborne Shiga-toxin-producing bacterium that leads to millions of cases of illness every year. The development of a portable biosensor that rapidly detects this pathogen can greatly reduce both the time required to identify the source of contamination within the food production chain and the scale of outbreaks. Here we propose a swab for the detection of E. coli O157:H7 made from electrospun poly-3-hydroxybutyrate (PHB) on which the reporter bacteriophage (phage), PP01—engineered to express the bioluminescent protein Nanoluc upon infection of the pathogen—has been immobilized. In the development of the material, the properties of phage-immobilized electrospun porous, nonwoven PHB mats were compared to those of phage-immobilized flat PHB films produced by solvent casting. Dynamics of E. coli infections initiated with the phage-immobilized materials showed the electrospun mats had the highest infectivity, indicative of higher phage surface density (confirmed by microscopy) and activity—two important properties for the sensitivity and response time of biosensors. In sample tests, successful detection of E. coli O157:H7 cells in both milk and Tryptic Soy Broth at concentrations of 105 CFU/mL within 1 h and 101 CFU/mL within 3 h demonstrates the promising potential of the system as a food safety assessment tool.

Influence of Nutrient Media Compared to Human Synovial Fluid on the Antibiotic Susceptibility and Biofilm Gene Expression of Coagulase-Negative Staphylococci In Vitro

Bacterial antibiotic resistance and biofilm formation are mechanisms usually involved in the pathogeny of implant-related infections. Worldwide, antibiotic susceptibility tests are usually carried out using nutrient-rich media. Clinical routine laboratories and even research centers use for example EUCAST or CLSI for guidelines. In this study, we investigated the effect of different nutrient media on the antibiotic susceptibility and icaADBC gene expression of bacteria in biofilm. As media, Müller-Hinton Bouillon (MHB), Tryptic Soy Broth (TSB) and human synovial fluid (SF) diluted 1:4 in phosphate buffered saline (PBS), each also supplemented with 1% glucose, were used. The influence of different nutrient media on the antibiotic susceptibility of coagulase-negative staphylococci (CoNS) was evaluated by counting of colony-forming units (CFU) and by checking the metabolic activity of the bacteria. We used reverse transcriptase and real-time qPCR to investigate the influence of nutrient media on the biofilm gene expression. We used two-way analysis of variance (ANOVA). p < 0.05 was considered to be statistically significant. Significant differences in growth and antibiotic susceptibility were detected in all strains tested among the different media used. The nutrient media showed influence on the cell viability of all bacteria after antibiotic treatment. IcaADBC gene expression was significantly influenced by glucose and all nutrient media. The results highlight the influence of glucose on the antibiotic susceptibility, growth and gene expression of all strains tested. For all strains, a significant difference in bacterial recovery, viability and gene expression were found when compared to biofilm grown in SF.

Biotransformation and removal of arsenic oxyanions by Alishewanella agri PMS5 in biofilm and planktonic states

Arsenic oxyanions are toxic chemicals that impose a high risk to humans and other living organisms in the environment. The present study investigated indigenous heterotrophic bacteria in the tailings dam effluent (TDE) of a gold mining factory. Thirty-seven arsenic resistant bacteria were cultured on Reasoner's 2A agar supplemented with arsenic salts through filtration. One strain encoded as PMS5 with the highest resistance to 140-mM sodium arsenite and 600-mM sodium arsenate in tryptic soy broth was selected for further investigations. According to phenotypic examinations and 16S rDNA sequence analysis, PMS5 belonged to the genus Alishewanella and was sensitive to most of the examined antibiotics. The biosorption and bioaccumulation abilities of arsenic salts were observed in this isolate based on Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) and biosorption and bioaccumulation data. PMS5 was also found to cause the volatilization and biotransformation of arsenic oxyanions through their oxidation and reduction. Moreover, the contribution of PMS5 to arsenic (3+, 5+) bioprocessing under oligotrophic conditions was confirmed in fixed-bed reactors fed with the TDE of the gold factory (R1) and synthetic water containing As5+ (R2). According to biofilm assays such as biofilm staining, cell count, detachment assay and SEM, the arsenic significantly reduced the biofilm density of the examined reactors compared to that of the control (R3). Arsenate reduction and arsenite oxidation under bioreactor conditions were respectively obtained as 75.5–94.7% and 8%. Furthermore, negligible arsenic volatilization (1.2 ppb) was detected.

Antimicrobial activity of olive leaf extract on selected foodborne pathogens and its effect on thermal resistance of Listeria monocytogenes in sous vide ground beef

Antimicrobial activity of a commercial olive leaf extract (OLE) against Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, Escherichia coli Biotype I, Salmonella Enteritidis and Salmonella Typhimurium was tested by disc diffusion assay. The Gram negative bacteria tested in this study were more sensitive to OLE than Gram negatives. The highest antimicrobial activity was on L. monocytogenes which yielded the largest inhibitions zone. Effect of OLE on thermal resistance of L. monocytogenes was tested both in Tryptic Soy Broth supplemented with 0.6% yeast extract (TSBYE) and sous vide packed ground beef. OLE added TSBYE (0, 0.5, 1%) tubes and ground beef (0, 1%) samples were inoculated with L. monocytogenes (7-8 log cfu/ml-g) and heated at 55, 60 and 65°C up to 30, 20 and 7.5 minutes, respectively. Total reductions in TSBYE tubes added with 0.5 and 1% OLE were slightly higher than control tubes (0% OLE) for all temperatures. Counts of L. monocytogenes in sous vide packed ground beef samples added with 1% OLE and then cooked at 55°C (30 min), 60°C (20 min) and 65°C (7.5 min) were 0.31, 1.04 and 0.73 log cfu/g lower than those control samples, respectively. The results indicate that OLE included in formulation may be an additional hurdle to control L. monocytogenes in heat processed ground beef.

IS IT POSSIBLE TO MAKE FEWER EXPERIMENTS: PREDICTION OF BACTERIAL SURVIVAL/DEATH PROBABILITY FOR HIGH-PRESSURE PROCESSING WITH THE BAYESIAN APPROACH?

In the present study, a model based on Bayesian Logistic Regression (BLR) was developed to predict the probability of bacterial survival/death treated with high-hydrostatic pressure under different conditions. Previously published data for Listeria monocytogenes in phosphate-buffered saline and Cronobacter sakazakii in trypticase soy broth and infant formula were used where the process variables were pressure, temperature, medium pH, initial inoculum and processing time. Along with the using possibility of BLR, effects of introduced sampling size by changing data split ratio and case prevalence were assessed. The BLR model predictions were consistent with both experimental data and the frequentist logistic regression models. Although some overfitting problems arise as the sampling size decrease, BLR can produce reliable probability models with a smaller number of experimental data (about 50 experimental samples) than the frequentist approach requires. Moreover, instead of a point estimate, BLR offers a posterior distribution for parameters and predictions. So the present study has indicated that BLR can be a useful tool to describe the survival/death of microorganisms after high-pressure processes with less experimental data requirement than the frequentist approach and also with the ability to handle missing observation and imbalanced dataset. In the light of these outcomes, the design of new experiments according to BLR, save on time and costs for experimental studies and more detailed safety risk assessment may be feasible for the food industry.

Plasma electrolytic oxidation as an effective tool for production of copper incorporated bacteriostatic coatings on Ti-15Mo alloy

This report describes the plasma electrolytic oxidation (PEO) treatment of Ti-15Mo alloy surfaces in baths containing 0.1 M Ca(H2PO2)2 with different insoluble copper-based additives: CuO or Cu3(PO4)2. The aim of this work was to fabricate oxide coatings with bacteriostatic and cytocompatible properties. The surface morphology, roughness, and wettability (based on dynamic water contact angle measurements) of the oxide coatings were evaluated. Additionally, the presence of copper compounds and bioactive calcium and phosphorus in the investigated oxide coatings was confirmed using various spectroscopic and crystallographic techniques. The highest copper concentration (3.5 at.%) was detected in the oxide layer obtained using a PEO suspension bath comprising Cu3(PO4)2 and Ca3(PO4)2. The oxide coating generated from a PEO bath containing CuO had the lowest copper concentration (0.1 at.%). The bacteriostatic properties of the obtained Cu-doped oxide layers were established based on bacterial adhesion tests using Gram-positive Staphylococcus aureus (ATCC 25923) and Gram-negative Escherichia coli (ATCC 25922). On the Cu-incorporated surfaces, the number of surface-adhered bacterial colonies was ~10–100 times lower than on the reference Ti-15Mo surface, and ~105 times lower than on tryptic soy broth medium. The materials’ cytocompatibilities were confirmed through tests with MG-63 osteoblast-like cells.