Colony-forming Unit Values Research Articles

Bacterial contamination on the inner surface of the masks used by clinicians in a dental clinic

Wearing masks has become an essential safety measure during the coronavirus 2019 (COVID-19) pandemic. Especially clinicians in dental clinics should focus on infection control. However, there is currently no data regarding the frequency of replacement of the masks used in hospitals. Hence, it is necessary for dental clinic staff, who deal with many patients in an aerosol-producing environment, to have precise mask-wearing guidelines. The aim of this study was to evaluate the contamination on the inner surface of the masks used by clinicians in dental clinics and provide basic data to describe hospital infection control guidelines in greater detail. For Study I,12 participants were recruited. The experiment was conducted indoors. After wearing the mask, the temperature and the humidity inside the mask were measured at the set time points (immediately after wearing the mask, and 10 min, 30 min, 1 h, 2 h, and 4 h after wearing the mask). During the experiment, talking was not allowed. For Study II, 23 clinicians from dental clinics were recruited. After wearing the mask, the temperature, the humidity and the number of colony-forming units (CFU) inside the mask were measured at the set time points. Finally, 15 samples were selected for the study based on a survey. Bacterial identification was conducted using the 16S rDNA sequencing. The temperature and the humidity inside the mask increased significantly relative to room temperature and room humidity, respectively. Bacteria were found in all the masks worn for more than 10 min and the CFU values increased with the mask-wearing time. Bacteria belonging to the genera Staphylococcus, Bacillus and Roseomonas were detected in the used mask. A mask should not be worn for more than 2 h; however, the frequency of mask replacement can vary, depending on the number of patients encountered and the working environment.

Assessment of Milk Quality and Food Safety Challenges in the Complex Nairobi Dairy Value Chain.

Food networks present varying food safety concerns because of the complexity of interactions, production, and handling practices. We investigated total bacteria counts (TBCs) and total coliform counts (TCCs) in various nodes of a Nairobi dairy value chain and identified practices that influence food safety. A value chain analysis framework facilitated qualitative data collection through 23 key informant interviews and 20 focus group discussions. Content thematic analysis identified food safety challenges. Cow milk products (N = 290) were collected from farms (N = 63), collection centers (N = 5), shops/kiosks (N = 37), milk bars (N = 17), roadside vendors (N = 14), restaurants (N = 3), milk vending machines (N = 2), mobile traders (N = 2) and a supermarket (N = 1). Mean values of colony-forming units for TBC and TCC were referenced to East African Standards (EAS). Logistic regression analysis assessed differences in milk acceptability based on EAS. The raw milk from farms and collection centers was relatively within acceptable EAS limits in terms of TBC (3.5 × 105 and 1.4 × 106 respectively) but TCC in the milk from farms was 3 times higher than EAS limits (1.5 × 105). Compared to farms, the odds ratio of milk acceptability based on TBC was lower on milk bars (0.02), restaurants (0.02), roadside vendors (0.03), shops/kiosks (0.07), and supermarkets (0.17). For TCC, the odds that milk samples from collection centers, milk bars, restaurants, roadside vendors, and shops/kiosks were acceptable was less than the odds of samples collected from farms (0.18, 0.03, 0.06, 0.02, and 0.12, respectively). Comparison of raw milk across the nodes showed that the odds of milk samples from restaurants, roadside vendors, and shops/kiosks being acceptable were less than the odds of samples collected the farm for TBC (0.03, 0.04, and 0.04, respectively). For TCC, the odds of raw milk from collection centers, restaurants, roadside vendors, milk bars, and shops/kiosks being acceptable were lower than the odds of acceptability for the farm samples (0.18, 0.12, 0.02, 0.04, and 0.05, respectively). Practices with possible influence on milk bacterial quality included muddy cowsheds, unconventional animal feed sources, re-use of spoilt raw milk, milk adulteration, acceptance of low-quality milk for processing, and lack of cold chain. Therefore, milk contamination occurs at various points, and the designing of interventions should focus on every node.

Survival of Escherichia coli K-12 in various types of drinking water

For public health, drinking water should be free of bacterial contamination. Consumption of bottled water, especially in low-income countries has increased to avoid contamination. However, bottling, transportation, and handling procedures increase the risk of microbiological contamination, which is especially harmful to immunocompromised individuals. The objective of this research is to identify the fate of bacteria if drinking water becomes contaminated and inform consumers on which water type enables the least bacteria to survive. This research tested bottled mineral water, bottled spring water, and tap water inoculated with the Escherichia coli K-12 strain bacteria from times 0–72 hours. We hypothesized that bottled mineral water would provide the most sufficient conditions for the E. coli to survive. We found that if water becomes contaminated, the conditions offered by the three water types at room temperature allow the E. coli to survive up to three days. At 72 hours, the bottled spring water had the highest average colony forming units (CFUs), with tap and mineral water CFU values statistically lower than spring water but not significantly different from each other. The findings of this research highlight the need of implementing accessible quality drinking water for the underserved population and for the regulation of water sources.

A Novel 3D Titanium Surface Produced by Selective Laser Sintering to Counteract Streptococcus oralis Biofilm Formation

The topography of implant surfaces influences the interaction relationship between material and bacteria. The aim of this work was to characterize a novel 3D titanium surface, produced using Selective Laser Sintering (SLS), and to compare the bacterial interaction with machined and double acid etching (DAE) discs. The surface was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Energy Dispersive X-ray Spectrometry (EDX). The wettability was measured using the sessile method. The microbiological investigation consisted in the cultivation of a bacterial pioneer, Streptococcus oralis, on titanium surfaces, previously covered by human saliva in order to form the acquired pellicle. Then, colony forming units (CFUs), biofilm biomass quantification, analyses of viable and dead cells, and SEM observation were determined after 24 h of S. oralis biofilm formation on the different discs. A significantly higher nano-roughness with respect to the other two groups characterized the novel 3D surface, but the wettability was similar to that of machined samples. The microbiological assays demonstrated that the 3D discs reported significantly lower values of CFUs and biofilm biomass with respect to machined surfaces; however, no significant differences were found with the DAE surfaces. The live/dead staining confirmed the lower percentage of living cells on DAE and 3D surfaces compared with the machined. This novel 3D surface produced by SLS presented a high antiadhesive and antibiofilm activity.

Treatment effects and periodontal status of chronic periodontitis after routine Er:YAG laser-assisted therapy.

BACKGROUNDRoutine preclinical interventions for patients with chronic periodontitis such as supragingival cleaning and subgingival curettage, establishing a balanced occlusal relationship, and irrigation with 3% hydrogen peroxide can relieve the symptoms to some extent. However, there is room for improvement in the overall effect. For example, Er:YAG lasers can quickly increase the temperature of the irradiated tissue, effectively eliminate dental plaque and calculus, reduce periodontal pockets, adjust periodontal microecology, and reduce the gingival sulcus. The content of factors in the liquid, and then achieve the purpose of treatment.AIMThe aim was evaluate the effect of Er:YAG laser-assisted routine therapy on the periodontal status in chronic periodontitis.METHODSBetween October 2018 and January 2020, 106 patients with chronic periodontitis in our hospital were randomly assigned to either the study or control group, with 53 patients in each group. The control group underwent routine therapy, and the study group underwent Er:YAG laser therapy in addition to routine therapy. We evaluated the treatment outcome in both groups. Periodontal status was determined by clinical attachment loss (CAL), gingival index (GI), periodontal probing depth (PD), dental plaque index (PLI), and sulcular bleeding index (SBI), inflammatory factors in the gingival crevicular fluid, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-8], and colony forming units (CFUs).RESULTSTotal effectiveness in the study group (94.34%) was higher than that in the control group (79.25%, P < 0.05). The clinical parameters in the study group (PD, 5.28 ± 1.08 mm; CAL, 4.81 ± 0.79 mm; SBI, 3.37 ± 0.59; GI, 1.38 ± 0.40; PLI, 2.05 ± 0.65) were not significantly different from those in the control group (PD, 5.51 ± 1.14 mm; CAL, 5.09 ± 0.83 mm; SBI, 3.51 ± 0.62; GI, (1.41 ± 0.37; PLI, 1.98 ± 0.70) before treatment (P > 0.05). However, after treatment, the parameters in the study group (PD, 2.97 ± 0.38 mm; CAL, 2.71 ± 0.64 mm; SBI, 2.07 ± 0.32; GI, 0.51 ± 0.11; PLI, 1.29 ± 0.34) were lower than those in the control group (PD, 3.71 ± 0.42 mm; CAL, 3.60 ± 0.71 mm; SBI, 2.80 ± 0.44; GI, 0.78 ± 0.23; PLI, 1.70 ± 0.51) (P < 0.05). Differences in crevicular TNF-α, IL-6, and IL-8 levels in the study (TNF-α, 7.82 ± 3.43 ng/mL; IL-6, 11.67 ± 2.59 ng/mL; IL-8, 12.12 ± 3.19 pg/mL) and control groups (TNF-α, 9.06 ± 3.89 ng/ml, IL-6, 12.13 ± 2.97 ng/mL, IL-8, 10.99 ± 3.30 pg/mL) before therapy (P > 0.05) were not significant. Following treatment, the parameters were significantly lower in the study group (TNF-α, 2.04 ± 0.89 ng/mL; IL-6, 4.60 ± 1.26 ng/mL; IL-8, 3.15 ± 1.08 pg/mL) than in the control group (TNF-α, 3.11 ± 1.07 ng/mL; IL-6, 6.25 ± 1.41 ng/mL; IL-8, 4.64 ± 1.23 pg/mL, P < 0.05). The difference in the CFU of the study group [(367.91 ± 74.32) × 104/mL and control group (371.09 ± 80.25) × 104/mL] before therapy was not significant (P > 0.05). The CFU decreased in both groups following therapy, however, the CFU values were lower in the study group [(36.09 ± 15.26) × 104/mL] than in the control group [(45.89 ± 18.08) ×104/mL] (P < 0.05).CONCLUSIONCombining Er:YAG lasers with routine measures significantly improved the overall periodontal therapy outcomes by improving periodontal status and reducing oral levels of inflammatory factors and CFUs.

Effectiveness of Plasma-Treated Hydrogen Peroxide Mist Disinfection in Various Hospital Environments.

Hospital environments are associated with a high risk of infection. As plasma-treated hydrogen peroxide mist disinfection has a higher disinfection efficacy, we tested the efficacy of plasma-treated hydrogen peroxide mist disinfection on several surfaces in various hospital environments. Disinfection was performed in 23 rooms across different hospital environments, including hospital wards, outpatient departments (OPDs), and emergency rooms. A total of 459 surfaces were swabbed before/after disinfection. Surfaces were also divided into plastic, metal, wood, leather, ceramic, silicone, and glass for further analyses. Only gram-positive bacteria were statistically analyzed because the number of gram-negative bacteria and mold was insufficient. Most colony-forming units (CFUs) of gram-positive bacteria were observed in OPDs and on leather materials before disinfection. The proportion of surfaces that showed a percentage decrease in CFU values of more than 90% after disinfection were as follows: OPDs (85%), hospital wards (99%), and emergency rooms (100%); plastic (97%), metal (83%), wood (84%), leather (81%), and others (87%). Plasma-treated hydrogen peroxide mist disinfection resulted in a significant decrease in the CFU values of gram-positive bacteria in various environments. Plasma-treated hydrogen peroxide mist disinfection is an effective and efficient method of disinfecting various hospital environments.

Endothelial Progenitor Cell Function in Patients With Coronary Chronic Total Occlusion and its Relationship With Collateral Circulation.

To evaluate the relationship between endothelial progenitor cell (EPC) count and function and collateral circulation in coronary chronic total occlusions (CTOs). A total of 20 consecutive patients with successfully treated CTO lesions were included during a period of 12 months. EPC count and function were evaluated by flow cytometry and colony-forming unit (CFU) analysis at baseline (before percutaneous coronary intervention) and at 1-year follow-up. Patients were classified, according to Rentrop classification at the baseline angiography, as group 1 (Rentrop 3; n = 7) and group 2 (Rentrop <3; n = 13). Differences in EPC count and function were compared between groups. The EPC count did not differ between the 2 groups, either at baseline or at follow-up. CFU was significantly lower at follow-up compared with baseline in the overall population (16.6 10^6/mL (IQR, 10.2-29.4 10^6/mL) vs 7.1 10^6/mL (IQR, 5.3-25.0 10^6/mL); P=.046). Group 1 had both higher basal and follow-up CFU values compared with group 2 (35.4 10^6/mL (IQR, 21.5-41.8 10^6/mL) vs 13.3 10^6/mL (IQR, 6.9-17.5 10^6/mL) and 32.1 10^6/mL (IQR, 13.9-40.5 10^6/mL) vs 5.9 10^6/mL (IQR, 4.4-9.8 10^6/mL), respectively; P=.01 for both). By linear regression analysis, Rentrop grade 3 flow was an independent predictor of both basal and follow-up CFU levels (odds ratio, 3.66; 95% confidence interval, 6.41-29.69; P<.01; and odds ratio, 5.24; 95% confidence interval, 9.78-25.85; P<.01, respectively). Patients with Rentrop grade 3 collateral circulation exhibited higher EPC activity at baseline and at 1-year follow-up compared with those who had reduced collateral circulation. The role of this higher EPC activity in determining clinical endpoint should be investigated in a larger study.

In vitro comparison of root surface roughness and bacterial adhesion following treatment with three different instruments.

A novel device, piezoelectric 11 Gracey curet tip, reportedly combines benefits of a piezoelectric device and manual curet. The primary objective of this study was to compare root surface roughness outcomes between traditional manual curets and piezoelectric devices, as compared with this novel device. The secondary aim was to assess the level of adhesion of Streptococcus mutans on the root surface after instrumentation. The groups consisted of the following: 1) Gracey curet; 2) piezoelectric scaler; 3) piezoelectric 11 Gracey curet tip; and 4) untreated control. Root specimens were obtained from extracted human teeth and randomly assigned to each group. Surface roughness measurements (Ra and Rz) were taken with a profilometer before and after instrumentation. After instrumentation, root specimens were inoculated with S. mutans and biofilm was dislodged. Various dilutions of resuspended biofilm were incubated on blood agar plates and colony forming units (CFU) values were measured. The experimental device resulted in significantly lower Ra and Rz compared with other groups (P<0.01), and the Gracey curet was significantly lower than the piezoelectric tip and untreated control (P<0.05). The Gracey curet and experimental device tip had significantly lower CFU values compared with the control (P<0.05). There were no significant CFU value differences between the Gracey curet and both the piezoelectric and experimental device tips. There were no significant CFU differences between piezoelectric tip and both experimental device and control. There was no correlation between Ra and CFU values for Gracey curet, piezoelectric tip, or the control. However, correlation between Ra values and CFU approached significance for the experimental device (correlation=0.66, P=0.05). Piezoelectric 11 Gracey curet tip is effective at resulting in a significantly smoother surface compared with traditional piezoelectric and hand instruments. CFU values with piezoelectric 11 Gracey curet tip were significantly lower than non-instrumented surfaces, but there were no significant differences compared with conventional methods.

Usefulness of a 3D-printing air sampler for capturing live airborne bacteria and exploring the environmental factors that can influence bacterial dynamics

We created a handmade 3D-printed air sampler to effectively collect live airborne bacteria, and determined which environmental factors influenced the bacteria. Bacterial colony forming units (CFUs) in the air samples (n = 37) were monitored by recording the environmental changes occurring over time, then determining the presence/absence of correlations among such changes. The bacterial CFUs changed sharply and were significantly correlated with the DNA concentrations, indicating that the captured bacteria made up most of the airborne bacteria. Spearman's rank correlation analysis revealed significant correlations between the bacterial CFU values and some environmental factors (humidity, wind speed, insolation, and 24-h rainfall). Similarly the significant associations of CFU with humidity and wind speed were also found by multiple regression analysis with box-cox transformation. Among our panel of airborne bacteria (952 strains), 70 strains were identified as soil-derived Bacillus via the production of Escherichia coli- and Staphylococcus aureus-growth inhibiting antibiotics and by 16S rDNA typing. Soil-derived protozoa were also isolated from the air samples. We conclude that the airborne bacteria mainly derived from soil can alter in number according to environmental changes. Our sampler, which was created by easy-to-customize 3D printing, is a useful device for understanding the dynamics of live airborne bacteria.

A novel three-dimensionally printed model to assess biofilm removal by ultrasonically activated irrigation.

To apply an innovative three-dimensionally printed tooth model to investigate the efficacy of three ultrasonically activated irrigation (UAI) systems in removing multispecies biofilms from dentine samples. Three-dimensionally printed teeth with a curved root canal were fabricated with a standardized slot in the apical third of the root to achieve precision fit of human root dentine specimens. Multispecies biofilms including Enterococcus faecalis, Streptococcus mitis and Campylobacter rectus were developed in the root canal for 21days. The canals were allocated to be irrigated with 1% sodium hypochlorite (NaOCl) using a syringe and needle or ultrasonically activated NaOCl with a stainless-steel file (Irrisafe), a conventional nickel-titanium (Ni-Ti) file (CK) or a blue heat-treated Ni-Ti file (Endosonic Blue). Infected root canals irrigated with distilled water served as controls. Bacterial reduction was determined by colony-forming unit (CFU) counting (n=20), whilst biofilms were analysed using confocal laser scanning microscopy (n=7) and field emission scanning electron microscopy. For CFU counting, the independent two-sample t-test (Welch's t-test) was examined to compare overall bacterial reduction amongst groups. For CLSM analysis, the data were analysed using one-way analysis of variance (ANOVA), followed by the Scheffé post hoc test. The p-values <.05 were considered to indicate statistical significance. All groups in which NaOCl was ultrasonically activated had significantly lower CFU values than the syringe-and-needle irrigation and control groups (p<.05). Ultrasonic activation with the stainless-steel file and blue heat-treated Ni-Ti file significantly reduced the biofilm volume compared with other groups (p<.05). Overall, UAI with the blue heat-treated file resulted in the highest antibacterial and biofilm removal efficacy. UAI with different inserts had differential antibiofilm effects. The blue heat-treated Ni-Ti ultrasonic insert resulted in the greatest antibacterial and biofilm removal from dentine in this standardized root canal model.

Abundance of Veillonella spp. does not Reflect Salivary Nitrite Production after Nitrate Ingestion

Veillonella spp. have been reported to be the most prevalent nitrate-reducing bacterial species in the oral cavity. The purpose of this study was to examine the relationship between the abundance of Veillonella spp. and nitrite production after nitrate ingestion. Bacterial samples were obtained from the tongue surfaces of 50 university students. The predominant Veillonella spp., V. atypica, V. dispar, and V. rogosae were identified and enumerated using real-time polymerase chain reaction (qPCR). Salivary nitrate and nitrite were measured before and 30, 60, and 90 min after ingestion of 100 ml of beetroot juice. Increased nitrite concentrations were observed in all participants, with a mean increase of 0.61 (0.42-1.10) mM expressed as the median (interquartile range). Veillonella atypica was detected in 40 subjects (80%), V. dispar in 48 (96%), and V. rogosae in 48 (96%), at quantities ranging from 1.3 × 102 to 2.8 × 107 CFU/ml per subject. The strengths of the correlations of the log colony forming unit (CFU) values of V. atypica, V. dispar, V. rogosae, and the log CFU value of the three species together with the increase in nitrite levels were 0.091, 0.114, -0.228, and 0.060, respectively, none of which were significant (p > 0.05). Our results indicate that the abundance of Veillonella spp. is not related to salivary nitrite production after nitrate ingestion.

A New Treatment Experience in Pseudomonas Keratitis: Topical Meropenem and Cefepime.

To compare the efficacy of topical meropenem and cefepime treatments with respect to moxifloxacin as new treatment options in an experimental Pseudomonas keratitis model. Twenty-four rabbits in which keratitis are induced using Pseudomonas aeruginosa were divided into four groups according to treatment options. A solution of 50 mg/mL meropenem was prepared and topically applied to the first group, 50 mg/mL cefepime solution to the second group, topical 0.5% moxifloxacin drop to the third group, and topical isotonic (0.9% saline) solution to the fourth (control) group. The eyes were examined before and after treatment to score the clinical severity. After the subjects were sacrificed, their corneas were excised. To determine the efficacy of treatments, clinical score, bacterial load, and histopathological and immunohistochemical findings were evaluated. When the three treatment groups were compared, there was a significant difference in the colony-forming unit (CFU) value, polymorph-nuclear leukocyte (PMNL) infiltration, and matrix metalloproteinase (MMP)-9 immunoreactivity (P=0.022, P=0.038, and P=0.037, respectively). The CFU values, PMNL infiltration scores and MMP-9 immunoreactivity were significantly lower in the meropenem and moxifloxacin groups compared with the cefepime group (P<0.05 for all). There was no significant difference between the meropenem and moxifloxacin groups in respect of the CFU values, PMNL infiltration, and MMP-9 immunoreactivity (P=0.842, P=0.784, and P=0.699, respectively). The results of our study indicate that topical meropenem is at least as effective as topical moxifloxacin in the treatment of Pseudomonas keratitis. The meropenem and moxifloxacin are safer and suitable in the limited corneal invasion than cefepime. Thus, topical meropenem may be an alternative drug in the treatment of this condition. Clinical studies are needed to be conducted to assess this possibility more accurately.

Analysis of the Antimicrobial, Cytotoxic, and Antioxidant Activities of Cnidium officinale Extracts.

This study analyzed the antimicrobial, cytotoxic, and antioxidant properties of Cnidium officinale (CO) extracts to confirm their antimicrobial activity toward oral microorganisms. The control group contained 0 μg/mL of CO, and the experimental groups contained 50, 100, 150, and 200 μg/mL of CO. To confirm the antibacterial activity of CO extracts against microorganisms in the oral cavity, an inhibition zone test, a colony-forming unit (CFU) analysis, an optical density (OD) evaluation, and a SEM (scanning electron microscopy) analysis were performed. A cytotoxicity test was also conducted to determine cell viability, and the contents of flavonoids and polyphenols were measured to analyze the extract components. In the control group, the growth inhibition zone increased, while the CFU and OD values decreased (p < 0.05). The SEM analysis confirmed that the number of microorganisms for both the microbes decreased. The cell viability was more than 80% in both the control and experimental groups, excluding the 200 μg/mL sample. The flavonoid and polyphenol contents in the experimental groups showed higher values than those of the control group. Therefore, the CO extract showed considerable antimicrobial activity toward both Streptococcus mutans and Candida albicans, suggesting that it may be used as a natural antimicrobial agent for dental applications.

Surgical Smoke and Airborne Microbial Contamination in Operating Theatres: Influence of Ventilation and Surgical Phases.

Air cleanliness is a crucial factor in operating theatres (OTs), where the health of patients and staff must be preserved by controlling air contamination. Particular attention must be paid to ultrafine particles (UFPs) size range, generated for instance by electrosurgical instruments (ESTs). OT contamination is also affected by ventilation systems, medical staff and their gowning system, staff routines, instruments, etc. This comparative study is based on experimental measurements of airborne microbial contamination and UFPs carried out during real ongoing surgeries in two OTs equipped with upward displacement ventilation (UWD) and hybrid ventilation, with unidirectional airflow on the operating table and peripheral mixing (UDAF+Mixing) ventilation systems. Airborne contamination concentration at the exit grilles has been analyzed as function of four different surgical phases normally performed during an operation. Results highlight that airborne contamination is influenced by the activities carried out during the surgical phases. EST usage affects the contamination level more than staff size during operation observed. Colony forming unit (CFU) values in the protected area close to the patient’s wound are influenced more by the type of ventilation system than by surgical phases. CFU values decrease by 18 to 50 times from the UWD system to the hybrid one. The large airflow volumes supply together with high air velocities in OTs equipped with UDAF+Mixing systems guarantee a better and a safer airborne contamination control for patients and medical team in comparison with UWD systems.

Isolation of phosphate-solubilizing bacteria from subtropical soils with different fertilization histories

Phosphorus is one of the most abundant chemical elements but has a low bioavailability index. Therefore, microrganisms play a fundamental role in providing insoluble phosphorus to plants. The objective of this study was to evaluate the capacity of bacteria to solubilize inorganic phosphates in soils with different fertilization histories. Soil and rhizosphere samples were collected from a Red Distroferric Latosol, including a control without mineral or organic fertilizer (C), treatment with mineral fertilizer (MF) according to the needs of each crop, and treatment with organic fertilizer [300 m3 ha-1 of swine wastewater (SW)]. The medium containing calcium phytate presented more colony-forming units (CFU) for all fertilization histories, and growth in treatments C and MF was 50% higher than treatment with SW. CFU values in soils treated with SW were lower than those in the other treatments, and the diversity of insoluble phosphate-solubilizing bacteria (PSB) was higher in treatment C. These results indicate a negative relationship between phosphorus concentrations and the number of PSB.

Population Kinetics and Mechanistic Aspects of Saccharomyces cerevisiae Growth in Relation to Selenium Sulfide Nanoparticle Synthesis.

Biosynthesis of nanoparticles (NPs) by microorganisms is a cost- and energy-effective approach. However, how the production of NPs affects the population of producing organism remains as an unresolved question. The present study aimed to evaluate the kinetics of Saccharomyces cerevisiae growth in relation to synthesis of selenium sulfide nanoparticles by using a population model. To this end, the population of S. cerevisiae cells was investigated in terms of colony forming units (CFU) in the presence of the substrate in different time points. Fluctuation of sulfite reductase (SiR) activity, expression of MET5 and MET10 genes, and concentrations of sulfite and selenium were evaluated to support the population findings. CFU values in the test groups were lower than those in the control counterparts. The rise and fall of the SiR activity and MET5 and MET10 gene expression conformed to the variations of CFU values. The rate of reduction in the selenium and sulfite concentrations tended to decrease over the time. In conclusion, the cells population was negatively and positively affected by selenium and sulfite concentrations, respectively. The indirect relationship of the selenium ions concentration in the path analysis revealed that the product, selenium sulfide nanoparticles, caused this drop in S. cerevisiae cells population.

High Potential of Bacterial Adhesion on Block Bone Graft Materials

Bone graft infections represent a challenge in daily clinics, resulting in increased patient discomfort and graft removal. The aim of this study was to investigate the initial adhesion of five representative pathogens on three different block bone graft materials (xenogeneic, alloplastic and allogeneic) and to assess if chlorhexidine (CHX) can effectively control the initial bacterial adhesion. Three different block bone grafting materials (Tutobone®, Endobon® and human spongiosa) were incubated with Escherichia coli, Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis and Pseudomonas aeruginosa in the presence or absence of 0.2% CHX solution. Bacterial adhesion was assessed by the direct counting of the colony-forming units (CFUs) and visualized by scanning electron microscopy (SEM). Overall, the selected bacterial species adhered successfully to all tested bone replacement scaffolds, which showed similar bacterial counts. The lg CFU values ranged from 5.29 ± 0.14 to 5.48 ± 0.72 for E. coli, from 4.37 ± 0.62 to 5.02 ± 0.48 for S. aureus, from 4.92 ± 0.34 to 4.95 ± 0.21 for S. mutans, from 4.97 ± 0.40 to 5.22 ± 0.13 for E. faecalis and from 4.23 ± 0.54 to 4.58 ± 0.26 for P. aeruginosa. CHX did not interfere with initial microbial adhesion, and yet it killed all adhered bacterial cells. Thus, CHX can be used to prevent subsequent biofilm infections.

Optimal Condition of Isolation from an Adipose Tissue-Derived Stromal Vascular Fraction for the Development of Automated Systems.

The stromal vascular fraction (SVF) isolated from adipose tissue, which contains stem cells as well as other cell types, has been applied in various research fields. Although different enzymatic concentrations and treatment durations have been applied to isolate the SVF, optimal conditions have not been established. Thus, we aimed to establish the optimal conditions for isolation of the SVF from adipose tissue by automated systems. The SVF was collected from removed adipose tissues of five donors during surgery. The SVF was treated with 0.1% or 0.2% collagenase type I for 20, 40, or 60min. Then, colony forming unit (CFU) assays and flow cytometry were performed to characterize the adipose stem cells (ASCs). A cytokine array was used to investigate the correlation between colony-formation ability and the secretion of isolated ASCs. Treatment with 0.1% collagenase type I for 60min resulted in a higher SVF yield, whereas treatment with 0.1% collagenase for 40min resulted in higher CFU values. In addition, expression of interleukin (IL)-6, IL-8, and monocyte chemoattractant protein-1 in the SVF was higher in the high-CFU group than in the low-CFU group. The optimal conditions for isolation of the SVF from adipose tissue were treatment with 0.1% collagenase type I for 40min. We identified the conditions required for efficient SVF isolation based on high CFU values, and our results will facilitate the development of automated systems.

EFECTO DE LA DEFENSINA RECOMBINANTE (pdf1.2) SOBRE MICROORGANISMOS BENÉFICOS ASOCIADOS A FRIJOL GENÉTICAMENTE MODIFICADO

Genetically modified organisms have as a requirement for their release into the environment at the experimental stage an assessment of the possible risks that could be caused to the environment, to biological diversity, and to plant, animal and aquaculture health, in accordance with the biosafety law of genetically modified organisms in Mexico. Common bean (Phaseolus vulgaris L.) modified with the Arabidopsis thaliana defensin gene (pdf1.2) has the characteristic of conferring broad-spectrum tolerance/resistance to plant pathogenic fungi of beans. The interactions between five common bean homozygous lines cv. Flor de Mayo Anita modified with the defensin gene (FMA-pdf1.2), with the antagonistic Trichoderma harzianum, the symbiotic association with Rhizobium tropici and the Rhizophagus intraradices mycorrhizae association were analyzed. Sterile soil was inoculated with those microorganisms and their density and infection or colonization in bean roots were evaluated. T. harzianum showed a larger number of colony-forming units (CFU) in non-modified plants than in those that expressed defensin; however, CFU values in the modified plants were within the range reported by other authors for this type of symbiotic relationships. On the other hand, even though R. tropici develops at inter and intracellular spaces, where the defensin protein is expressed, the number of nodules exceeded that of unmodified control plants. Finally, the R. intraradices percentage of infection was inconsistent, being low in both FMA-pdf1.2 and unmodified plants; therefore, the effect of defensin was not clear. The above suggests that the presence of defensin does not represent a risk factor against microorganisms that do not invade the intra and intercellular space of the modified plants, or against microorganisms not included in the spectrum of action of pdf1.2.

Underperforming light curing procedures trigger detrimental irradiance-dependent biofilm response on incrementally placed dental composites

ObjectivesInsufficient radiant exposure (J/cm2) may provide an early trigger in a cascade of detrimental responses on incrementally-place composite, especially the bottom layer. This study aimed to assess the influence of poor radiant exposure, the degree of conversion (%DC), water sorption/ solubility and S. mutans biofilm formation on conventional, incrementally placed composites and to establish a relationship between these factors. MethodsTwo light units operating at 600 and 1000 mW/cm2 and four most common operator-dependent curing conditions had the radiant exposure (RE) recorded. All the specimens were subjected to S. mutans biofilm model for 14 days. The %DC, biofilm formation expressed by colony-forming units (CFU), water sorption/ solubility and surface roughness/ SEM were assessed. Data were submitted to two-way ANOVA and Tukey post-hoc test (α = 0.05). Pearson correlation was also determined. ResultsThe influence of RE on S. mutans CFU values and DC are dependent on the curing conditions and irradiance (p < 0.05). A negative relationship was observed between RE and biofilm formation. The operator-dependent curing conditions have shown RE reduction varying from 49.4% to 73.5% in relation to control. The difference in DC between top/bottom of cylinder varied from 13% to 21% for 1000 mW/cm2and from 29% to 53% for LCU600. The roughness, solubility and salivary sorption were greater for low RE. ConclusionPoor, deficient curing procedures provide an early trigger in a negative pathway of events for incrementally-place dental composite including a biological response by increased biofilm formation by S. mutans, a relevant factor for secondary caries development. SignificanceThe susceptibility to variation in the outcomes was RE -dependent. The optimization of the curing procedures ensures the maximum performance in the chain of events involved in the light curing process of resin-based materials and potentially reduce the risk factors of secondary caries development.