Reduction In Colony-forming Units Research Articles

Antibiofilm Activity of Diclofenac and Antibiotic Solutions in Endodontic Therapy

IntroductionThe aim of this study was to compare the antibiofilm effects of a triple antibiotic solution (TAS); a double antibiotic solution (DAS); and 5%, 2.5%, and 1.25% diclofenac solutions (DCSs) against Enteroccocus faecalis biofilm. MethodsEighty-four sterile radicular dentin blocks were used as biofilm substrate for 3 weeks. The study groups were as follows: (1) 1 mg/mL TAS (minocycline, metronidazole, and ciprofloxacin), (2) 1 mg/mL DAS (metronidazole and ciprofloxacin), (3) 5% DCS, (4) 2.5% DCS, (5) 1.25% DCS, and (6) 0.9% saline solution. The antimicrobial activity was evaluated by bacterial count determinations and confocal laser scanning microscopy. The contact time for the antimicrobial tests was 5 minutes. Bacterial counts were expressed as the reduction percentage of colony-forming units; for the confocal laser scanning microscopic evaluation, the log10 total biovolume and percentage of green population (live cells) were calculated. ResultsThe colony-forming unit reduction percentage ranged between 62.98 and 98.62, respectively, for TAS and 5% DCS. The DCS showed a concentration-dependent effect.For the confocal laser scanning microscopy, the log10 total biovolume in all groups was very similar and showed a scarce (1.39–1.02) but significant reduction with respect to the control; 5% and 2.5% DCSs gave the lowest viable cell percentage. The TAS and DAS groups showed intermediate values without significant differences between them. ConclusionsDCSs at 5% and 2.5% have greater antimicrobial effects than TAS and DAS and may be considered a valid alternative for controlling the infection of teeth with apical periodontitis.

Susceptibility of Staphylococcus epidermidis to Argon Cold Plasma Jet by Oxygen Admixture

Cold atmospheric pressure sterilization is one of the nominated and efficient techniques to prevent the spread of diseases. Reactive species such as O and OH and other radicals play a major role in the mechanism of plasma sterilization. Therefore, in this work, oxygen was mixed with different parentage from (0.2 to 1.2%) to argon to enhance the generation of the reactive species and increase the argon atmospheric pressure plasma sterilization efficacy. The emission spectra from the jet increase the radicle line intensities by increasing the percentage admixture of O2 with the argon gas to reach a maximum power at 0.8; then, it gradually decreases with a higher O2 percentage. The OH band intensity decreases with increasing the admixture of O2. The jet with different O2 percentages was tested against Gram-positive S. epidermidis, which is the causal agent of nosocomial infections. The maximum reduction in colony-forming units (CFU) was observed at 0.2% O2. No bacterial growth was observed at the later concentration applied for 8 min and the same case was detected at 0.4% O2 applied to 16 min.

Effect of Photothermal Therapy with Indocyanine Green in Multispecies Biofilm

The purpose of this study is to investigate the antibacterial effects of indocyanine green (ICG) and near-infrared diode lasers on multispecies biofilms. Multispecies biofilms of <i>Streptococcus mutans</i>, <i>Lactobacillus casei</i> and <i>Candida albicans</i> were treated with different irradiation time using photosensitizer ICG and 808 nm near-infrared diode laser. Colony forming unit (CFU) was measured, and qualitative evaluation of biofilm was performed with confocal laser scanning microscopy (CLSM). Temperature measurement was conducted to evaluate photothermal effect. In the groups using ICG and diode laser, reduction in CFU was statistically significant, but the difference in antibacterial effect on <i>L. casei</i> and <i>C. albicans</i> with irradiation time was not significant, and similar results were confirmed with CLSM. Groups with ICG and diode laser showed higher temperature elevation than groups without ICG, and results of measured temperature were similar to the range of hyperthermia. In conclusion, ICG and near-infrared diode laser showed antibacterial effects on multispecies biofilms, but studies on protocol are necessary for clinical application.

Evaluation of Smear Layer Removal and Antimicrobial Efficacy of HybenX Against Enterococcus Faecalis Biofilm.

To evaluate the antibacterial efficacy of HybenX, an endodontic irrigant against Enterococcus faecalis biofilm and determine its efficacy in removal of smear layer. Forty root canals were inoculated with E. faecalis for three weeks, divided into 4 groups and irrigated with: Group1: 5 ml 2.5% sodium hypochlorite; Group2: 5 ml 2% chlorhexidine gluconate; Group3: 5 ml HybenX; Group4: 5 ml distilled water (control). Dentin shavings were collected and plated on agar plates, followed by colony forming unit (CFU) determination. For smear layer removal examination, 30 single rooted teeth were instrumented and divided into 3 groups and treated with: GroupI: 5 ml of 17% EDTA; GroupII:5 ml of HybenX; and GroupIII: 5 ml of distilled water. Samples were then subjected to SEM examination. All irrigants showed a significant reduction in CFUs compared to the control group (P⟨ .001), but none compared to each other. Regarding smear layer removal in the apical third, EDTA removed smear layer more effectively than HybenX (P = .014). HybenX demonstrated good antimicrobial efficacy against E. faecalis biofilm and removed the smear layer effectively in coronal and middle third of the root canal system. HybenX can be considered as a promising irrigating agent in root canal treatment of infected teeth.

Antibiofilm and Protein-Repellent Polymethylmethacrylate Denture Base Acrylic Resin for Treatment of Denture Stomatitis.

Candida albicans (C. albicans) biofilm is a common etiological factor in denture stomatitis. The purpose of this study was to investigate the effects of incorporating 2-methacryloyloxyethyl phosphorylcholine (MPC) as a protein repellent into a new high-impact denture acrylic (HIPA) resin on the surface roughness, solution pH, and C. albicans biofilm adhesion to the denture base. The new acrylic denture resin base was formulated by mixing MPC into HIPA resin at mass fractions of 1.5%, 3%, and 4.5%. Surface roughness was measured using a Mitutoyo surface roughness tester. C. albicans biofilm growth and viability were assessed via colony forming unit counts. The pH of the biofilm growth medium was measured using a digital pH meter. Adding MPC to the HIPA resin at percentages of 1.5% and 3% increased the roughness values significantly (p < 0.05), while adding 4.5% MPC resulted in no difference in roughness values to that of the control group (p > 0.05). All experimental groups demonstrated neutral pH values (pH ≅ 7) and were not significantly different from each other (p > 0.05). Incorporating 2-methacryloyloxyethyl phosphorylcholine at 4.5% resulted in a significant (≅1 log) colony-forming unit reduction compared with the control group with 0% MPC (p < 0.05). A fungal-retarding denture acrylic resin was developed through the incorporation of MPC for its protein-repelling properties. This newly developed denture acrylic material has the potential to prevent oral microbial infections, such as denture stomatitis.

Identification of Quinone Degradation as a Triggering Event for Intense Pulsed Light-Elicited Metabolic Changes in Escherichia coli by Metabolomic Fingerprinting.

Intense pulsed light (IPL) is becoming a new technical platform for disinfecting food against pathogenic bacteria. Metabolic changes are deemed to occur in bacteria as either the causes or the consequences of IPL-elicited bactericidal and bacteriostatic effects. However, little is known about the influences of IPL on bacterial metabolome. In this study, the IPL treatment was applied to E. coli K-12 for 0–20 s, leading to time- and dose-dependent reductions in colony-forming units (CFU) and morphological changes. Both membrane lipids and cytoplasmic metabolites of the control and IPL-treated E. coli were examined by the liquid chromatography-mass spectrometry (LC-MS)-based metabolomic fingerprinting. The results from multivariate modeling and marker identification indicate that the metabolites in electron transport chain (ETC), redox response, glycolysis, amino acid, and nucleotide metabolism were selectively affected by the IPL treatments. The time courses and scales of these metabolic changes, together with the biochemical connections among them, revealed a cascade of events that might be initiated by the degradation of quinone electron carriers and then followed by oxidative stress, disruption of intermediary metabolism, nucleotide degradation, and morphological changes. Therefore, the degradations of membrane quinones, especially the rapid depletion of menaquinone-8 (MK-8), can be considered as a triggering event in the IPL-elicited metabolic changes in E. coli.

Antibacterial calcium phosphate cement with human periodontal ligament stem cell‐microbeads to enhance bone regeneration and combat infection

Infectious bone defects remain a significant challenge in orthopedics and dentistry. Calcium phosphate cement (CPC) have attracted significant interest in use as local drug delivery system, which with great potential to control release of antibiotics for the treatment of infectious bone defects. Within the current study, a novel antibacterial scaffold of chitosan-reinforced calcium phosphate cement delivering doxycycline hyclate (CPCC + DOX) was developed. Furthermore, the capacity of CPCC + DOX scaffolds for bone regeneration was enhanced by the human periodontal ligament stem cells (hPDLSCs) encapsulated in alginate beads. CPCC + DOX scaffolds were fabricated to contain different concentrations of DOX. Flexural strength of CPCC + DOX ranged from 5.56 ± 0.70 to 6.2 ± 0.72 MPa, which exceeded the reported strength of cancellous bone. Scaffolds exhibited continual DOX release, reaching 80% at 21 days. Scaffold with 5 mg/ml DOX (CPCC + DOX5mg) had a strong antibacterial effect, with a 4-log colony forming unit reduction against S. aureus and P. gingivalis. The proliferation and osteogenic differentiation of hPDLSCs encapsulated in alginate hydrogel microbeads were investigated in culture with CPCC + DOX scaffolds. CPCC + DOX5mg had no negative effect on proliferation of hPDLSCs. Alkaline phosphatase activity, mineral synthesis, and osteogenic gene expressions for CPCC + DOX5mg group were much higher than control group. DOX did not compromise the osteogenic induction. In summary, the novel CPCC + DOX scaffold exhibited excellent mechanical properties and strong antibacterial activity, while supporting the proliferation and osteogenic differentiation of hPDLSCs. The CPCC + DOX + hPDLSCs construct is promising to enhance bone regeneration and combat bone infections in dental, craniofacial, and orthopedic applications.

Disinfection capabilities of a 222 nm wavelength ultraviolet lighting device: a pilot study.

To demonstrate the efficacy of the SafeZone UVC (Ushio Inc., Japan) 222 nm ultraviolet C (UVC) light to reduce bacterial burden in pressure ulcers (PUs) in human patients. This research is the first human clinical trial using 222 nm UVC in eradicating bacteria in human wounds. Patients with Stage 2 or 3 (as defined by the revised National Pressure Ulcer Advisory Panel Pressure Injury Staging System) sacral or gluteal pressure ulcers (PUs) were subjected to four sessions of 222 nm UVC light therapy over two weeks. Pre- and post-UVC therapy, wound cultures were taken and quantitative analysis of bacterial colony forming units (CFU) were performed. A total of 68 UV light sessions across 16 different patients were conducted. Of these sessions, 59 (87.0%) sessions showed a reduction in CFU counts, with 20 (29.4%) showing complete eradication of bacteria. Bacteria identified included meticillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella Pneumoniae. The overall median reduction in CFU of the 68 sessions was 78.9%. No adverse events were reported in any of the UV sessions. In this study, 222 nm UVC light was safe and effective in reducing bacterial CFU counts in sacral and gluteal PUs across numerous different species of bacteria.

Effectiveness of topical adjuvants in reducing biofilm formation on orthopedic implants: an invitro analysis.

The treatment of periprosthetic joint infection is complicated by the presence of residual biofilm, which resists eradication owing to bacterial adherence to orthopedic implants. The purpose of this study was to compare Bactisure (Zimmer Biomet, Warsaw, IN, USA), povidone-iodine (Betadine), and chlorhexidine gluconate solution (Irrisept; Irrimax, Gainesville, FL, USA) in reducing biofilm formation of Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes inoculated on cobalt-chrome, titanium, and stainless steel disks, representing metals commonly used for shoulder arthroplasty. The hypothesis was that there would be no significant difference in biofilm reduction among the 3 topical adjuvants. Strains of S aureus (ATCC 35556), S epidermidis (ATCC 35984), and C acnes (LMG 16711) were grown on cobalt-chrome, titanium, and stainless steel disks. For each strain, the disks were divided into 4 groups: (1) control, (2) povidone-iodine (Betadine), (3) chlorhexidine gluconate (Irrisept), and (4) Bactisure. Bacteria were grown on 5% sheep blood agar plates. Biofilm eradication was quantified using adenosine triphosphate bioluminescence and compared with controls 48 and 72 hours after implementation of the topical adjuvant. At 72 hours after implementation of the topical adjuvant, a statistically significant reduction in colony-forming units was observed for all topical adjuvants across all tested metals, as compared with their respective control. With respect to the topical adjuvants themselves, Bactisure more consistently demonstrated the most significant reduction in colony-forming units across all bacteria when the tested medium was adjusted for, with the exception of S aureus, which showed similar results to Betadine at 72 hours. By use of commonly encountered topical adjuvants on S aureus-, S epidermidis-, and C acnes-inoculated disks of various implant metals, a significant reduction in biofilm production was observed. Bactisure, a recent Food and Drug Administration-approved topical adjuvant, demonstrated the overall greatest efficacy of the agents studied.

Shiga Toxin-Producing Escherichia coli in the Long-Term Survival Phase Exhibit Higher Chlorine Tolerance and Less Sublethal Injury Following Chlorine Treatment of Romaine Lettuce.

The extent of chlorine inactivation and sublethal injury of stationary-phase (STAT) and long-term survival-phase (LTS) cells of Shiga toxin-producing Escherichia coli (STEC) in vitro and in a lettuce postharvest wash model was investigated. Four STEC strains were cultured in tryptic soy broth supplemented with 0.6% (w/v) yeast extract (TSBYE; 35°C) for 24 h and 21 d to obtain STAT and LTS cells, respectively. Minimum bactericidal concentration (MBC) and dose-response assays were performed to determine chlorine's antibacterial efficacy against STAT and LTS cells. Chlorine solutions (pH 6.5) and romaine lettuce were each inoculated with STAT and LTS cells to obtain initial populations of ∼7.8 log colony-forming units (CFU)/mL. Survivors in chlorine solutions were determined after 30 s. Inoculated lettuce samples were held at 22°C ± 1°C for 2 h or 20 h and then exposed to chlorine (10-40 ppm) for 60 s. Survivors were enumerated on nonselective and selective agar media following incubation (35°C, 48 h). The MBC for STAT and LTS cells was 0.04 and 0.08 ppm, respectively. Following exposure (30 s) to chlorine at 2.5, 5.0, and 10 ppm, STAT cells were reduced to <1.0 log CFU/mL, whereas LTS survivors were at 5.10 (2.5 ppm), 3.71 (5.0 ppm), and 2.55 (10 ppm) log CFU/mL. At 20 and 40 ppm chlorine, greater log CFU reductions of STAT cells (1.64 and 1.85) were observed compared with LTS cells (0.94 and 0.83) after 2 h of cell contact with lettuce (p < 0.05), but not after 20 h. Sublethal injury in STEC after chlorine (40 ppm) treatment was lower in LTS compared with STAT survivors (p < 0.05). Compared with STAT cells, LTS cells of STEC seem to have higher chlorine tolerance as planktonic cells and as attached cells depending on cell contact time on lettuce. In addition, a higher percentage of LTS cells, compared with STAT cells, survive in a noninjured state after chlorine (40 ppm) treatment of lettuce.

Antimicrobial Effect of 1,25 Dihydroxy Vitamin D on Vibrio cholerae and its Association with Serum 25-Hydroxy Vitamin D Level in Rural Elderly Women: An Experimental Study

Introduction: Aging is associated with a variety of functional, demographic and immunologic changes, responsible for increasing the incidence and severity of infectious diseases in the elderly. Aim: To examine the association of serum 25-hydroxy vitamin D status with antimicrobial activity of cultured macrophages isolated within an exclusively elderly population cohort and also to examine the effect of in-vitro 1,25 hydroxy vitamin D supplementation in it. Materials and Methods: This experimental study was conducted among 113 elderly women aged between 60 to 70 years of age, during the period of April 2014 to August 2018, at Amdanga block, North 24th Parganas, West Bengal, India. Their vitamin D status was assessed by the estimation of serum 25-hydroxy vitamin D and classified into three groups, sufficient group (60 subjects), insufficient group (27 subjects) and deficient group (26 subjects). Later their Peripheral Blood Mononuclear Cells (PBMC) were isolated and cultured from fresh blood of each and every study subject. Supplementation of 1,25 dihydroxy vitamin D {1,25(OH)2D} was given selectively at a dose of 10×10-8 M for 72 hours in the culture media and were exposed to Vibrio cholerae and inducible nitric oxide synthase (iNOS), Superoxide Dismutase (SOD) activity and Bactericidal activity were screened. Statistical Package for the Social Sciences (SPSS) software, version 20.0 was used to perform statistical analysis. Results: The sufficient group iNOS activity had significantly higher than the other two groups. Whereas in-vitro 1, 25(OH)2D supplementation increases iNOS activity significantly among all three groups. As per the Colony Forming Unit (CFU) reduction rate against Vibrio cholerae infection the sufficient serum 25(OH)D consisting group had significantly (p-value=0.03) high CFU reduction rate than the other two groups. Although in-vitro 1, 25(OH)2D supplementation had no significant impact on CFU reduction rate among all three groups. Conclusion: Bacteria killing capacity of macrophages varies significantly with serum 25-hydroxy vitamin D level of the target population. Sufficient group macrophages always had better profile than other two groups. In-vitro 1, 25(OH)2D supplementation increases iNOS and SOD activity significantly.

Comparative Evaluation of the Antimicrobial Effect of Mangosteen, Triphala, Chitosan, and 2% Chlorhexidine on Mono- and Dual-Species Biofilms of - and Candida albicans: An in Vitro Study.

Objective:The purpose of this in vitro study was to compare the antimicrobial effectiveness of 2% chlorhexidine gel, 0.5% chitosan, ethanol extract of mangosteen pericarp, and Triphala used as intracanal medicaments against Enterococcus faecalis and Candida albicans in mono- and dual-species biofilms.Methods:Bioactive components in the ethanol extract of mangosteen pericarp and Triphala were evaluated by gas chromatography-mass spectrometry (GCMS). Quantitative assessment of the biofilm formations of E. faecalis and C. albicans and as a dual-species in the presence of test medicaments was carried out using a crystal violet (CV) assay in a microtiter plate. Following this, 246 single-rooted premolar teeth were collected, and root specimens were prepared. C. albicans and E. faecalis mono- and dual-species biofilms were grown in the root specimens. At the end of 21 days, the samples were divided into five groups and subjected to different types of medicaments: Control group- distilled water; Chlorhexidine group- 2% chlorhexidine gel; Chitosan group- 0.5% chitosan; Mangosteen group- ethanol extract of mangosteen pericarp; and Triphala group- ethanol extract of Triphala. Colony-forming units (CFUs) were assessed on the first and fifth day after medicament placement.Results:Microbial population reduction was measured by one-way analysis of variance, followed by post-hoc Tukey’s multiple comparison test (P<0.05). Chlorhexidine showed maximum log reduction in CFUs of microorganisms, followed by chitosan, which showed a similar log reduction (P>0.05) for both mono- and dual-species biofilms. However, in the mangosteen and Triphala extract groups, the CFU/mL for dual-species on both days did not have a significant reduction in count (P<0.05) when compared to chlorhexidine and chitosan.Conclusion:Chlorhexidine showed maximum antimicrobial activity, followed by chitosan, on both mono- and dual-species biofilms. Mangosteen and Triphala had good antimicrobial action on the mono-species biofilm.

Comparative evaluation of three different ultrasonic liquid on microorganisms in dental aerosols

Introduction: Transmission of diseases has become very common in modern dentistry. This happens mainly due to aerosol production by handpieces and ultrasonic scalers. Aerosol and splatter are terms typically used in dentistry in relation to the microbiological risk of nosocomial transmission. Hence, in order to prevent this, we can use certain chemical agents in the water supply line to prevent the spread of diseases. The objective of this study is to assess the effect of chlorhexidine (CHX) and povidone-iodine (PVI) on the microorganisms in dental aerosols in comparison with distilled water. Materials and Methods: A total of thirty patients were included in this study. They were randomly assigned into three groups of 10 each. Group 1 (Control group): ultrasonic scaling with distilled water, Group 2 (test group): ultrasonic scaling with 2% povidone-iodine, and Group 3 (test group): ultrasonic scaling with 0.12% CHX. Three blood agar plates were kept at a distance of 0.4 m away on either side of the patient and 2 m behind the patient's mouth during ultrasonic scaling. On the patient, ultrasonic scaling is executed for 20 min with a universal tip. Blood agar plates were used to collect the gravitometric settling of dental aerosols, followed by a colony-counting procedure with the help of a microbiologist. Results: The results demonstrated no significant number of colony-forming unit (CFU) were detected at baseline. It is found that Group 3 (CHX gluconate) showed effective CFU reduction (29.2 ± 1.47 CFU) compared to distilled water (126.5 ± 24.02CFU) and povidone-iodine (70.1 ± 2.13 CFU). More CFU was found on blood agar plates which were kept on the right side in all the groups. The results obtained were statistically significant (P

A novel antimicrobial-containing nanocellulose scaffold for regenerative endodontics.

ObjectivesThe aim of this study was to evaluate bacterial nanocellulose (BNC) membranes incorporated with antimicrobial agents regarding cytotoxicity in fibroblasts of the periodontal ligament (PDLF), antimicrobial activity, and inhibition of multispecies biofilm formation.Materials and MethodsThe tested BNC membranes were BNC + 1% clindamycin (BNC/CLI); BNC + 0.12% chlorhexidine (BNC/CHX); BNC + nitric oxide (BNC/NO); and conventional BNC (BNC; control). After PDLF culture, the BNC membranes were positioned in the wells and maintained for 24 hours. Cell viability was then evaluated using the MTS calorimetric test. Antimicrobial activity against Enterococcus faecalis, Actinomyces naeslundii, and Streptococcus sanguinis (S. sanguinis) was evaluated using the agar diffusion test. To assess the antibiofilm activity, BNC membranes were exposed for 24 hours to the mixed culture. After sonicating the BNC membranes to remove the remaining biofilm and plating the suspension on agar, the number of colony-forming units (CFU)/mL was determined. Data were analyzed by 1-way analysis of variance and the Tukey, Kruskal-Wallis, and Dunn tests (α = 5%).ResultsPDLF metabolic activity after contact with BNC/CHX, BNC/CLI, and BNC/NO was 35%, 61% and 97%, respectively, compared to BNC. BNC/NO showed biocompatibility similar to that of BNC (p = 0.78). BNC/CLI showed the largest inhibition halos, and was superior to the other BNC membranes against S. sanguinis (p < 0.05). The experimental BNC membranes inhibited biofilm formation, with about a 3-fold log CFU reduction compared to BNC (p < 0.05).ConclusionsBNC/NO showed excellent biocompatibility and inhibited multispecies biofilm formation, similarly to BNC/CLI and BNC/CHX.

1309. Imipenem/Cilastatin/Relebactam (I/R) Alone and in Combination against Pseudomonas aeruginosa (PSA) in the In Vitro Pharmacodynamic Model

BackgroundI/R, a carbapenem-beta-lactamase inhibitor antibiotic, is active against most imipenem-resistant PSA, including MDR isolates. Combination therapy may enhance activity against MDR pathogens and suppress resistance. This study’s objective was to assess the efficacy of I/R compared with combinations including colistin (CST) or amikacin (AMK) against PSA in an IVPD model.MethodsHuman-simulated concentrations of I/R 500/250 mg every six hours, a total daily dose of CST 360 mg, and AMK 25 mg/kg daily were reproduced alone and in combination against 6 imipenem-non-susceptible PSA with I/R MICs of 1/4 to 8/4 mg/L in an IVPD over 24h. The primary endpoint was the difference in 24h colony forming units (CFU) between each combination regimen and its components alone. The log ratio differences of the area under the CFU curve were also calculated to compare the overall bacterial burden resulting from exposure to I/R alone with those treated by combination regimens. Emergence of resistance was tested at 24h using drug-containing plates at 3xMIC.ResultsI/R, CST, and AMK alone produced 24hCFU changes consistent with isolate MICs. One isolate (already I/R non-susceptible) developed I/R resistance, and 4 and 3 developed CST and AMK resistance, respectively. I/R plus CST suppressed all resistance and resulted in synergistic or additive interactions against three of six isolates with 24h CFU reductions ranging from -2.62 to -4.67 log10CFU/mL. This combination further reduced overall bacterial burden by 79-81% compared with I/R alone against two I/R-non-susceptible strains. I/R plus AMK also prevented resistance emergence but exhibited indifferent interactions against all isolates at 24h with the combined drugs achieving -0.51 to -3.33 log10CFU/mL reductions. Minor overall reductions in bacterial burden were observed relative to I/R alone.ConclusionI/R plus CST resulted in additivity or synergy against three of six PSA and prevented I/R and CST resistance, whereas the addition of AMK only suppressed resistance. The greatest overall reductions in bacterial burden, however, were observed with I/R plus CST against I/R-non-susceptible isolates, supporting targeted use of this combination against this phenotype when alternatives are unavailable.Disclosures David P. Nicolau, PharmD, Cepheid (Other Financial or Material Support, Consultant, speaker bureau member or has received research support.)Merck & Co., Inc. (Consultant, Grant/Research Support, Speaker’s Bureau)Wockhardt (Grant/Research Support) Joseph L. Kuti, PharmD, Allergan (Speaker’s Bureau)bioMérieux (Research Grant or Support, Other Financial or Material Support, Speaker Honorarium)Melinta (Research Grant or Support)Merck & Co., Inc. (Research Grant or Support)Paratek (Speaker’s Bureau)Summit (Other Financial or Material Support, Research funding (clinical trials))

500. Novel Use of a Targeted Ultraviolet Light Device for the Decontamination of a Single-Use Filtering Facepiece Respirator

BackgroundThe use of disposable or single-use filtering facepiece respirators (FFRs), like N95s, are an important component of personal protective equipment for healthcare personnel in treating patients with a respiratory virus and not approved for reuse. The current pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in the limited availability of respirators. As a result, the decontamination of FFRs is a potential solution for reuse in order to conserve supplies. However, the efficacy of disinfection for a contaminated FFR needs to be evaluated. This experiment examined the effectiveness of a targeted ultraviolet C (UVC) device for the decontamination of a single-use respirator.MethodsTo mimic an aerosolized droplet contaminating a cellulose based respirator, a 6 mm cotton disk was inoculated with a 10 μL aliquot of Bacillus subtilis endospores. The disks were placed directly under the UVC light with 6 inches between the bulb and disk. The samples were then exposed for 90 seconds, 3 minutes, 5 minutes, and 10 minutes, respectively. After specified exposure time, the disks were turned over, and the other side was exposed for the same time interval as the previous side. Disks were placed in a 10 mL nutrient broth and incubated at 30°C for 48 hours. Lastly, the serially diluted specimens were plated onto nutrient agar, incubated for 48 hours, and the log10 colony forming units (CFU) reductions were enumerated by comparing disks after decontamination versus untreated controls.ResultsThe log10 CFU reduction of B. subtilis spores over all time intervals were significant when compared to controls. The mean reduction of spores on the cotton disks were 2.5 log after 90 seconds, 4 log after 3 minutes, and >6 log for both 5 and 10 minutes with no measurable recovery of spores for the last two exposures.ConclusionThe use of targeted UVC was very successful in reducing the B. subtilis spores from a cotton disk within 90 seconds, and the 100% elimination of the spores after 5 minutes. Even though a pandemic virus was not used, the sporicidal efficacy suggests this device could be effective at inactivating SARS-CoV-2. Based upon these findings, a targeted UVC device could be utilized for the decontamination of a single-use respirator needed during times of shortages.Disclosures All Authors: No reported disclosures

A Novel Dicationic Boron Dipyrromethene-based Photosensitizer for Antimicrobial Photodynamic Therapy against Methicillin-Resistant Staphylococcus aureus.

Background We report herein the synthesis of a novel dicationic boron dipyrromethene derivative (compound 3) which is symmetrically substituted with two trimethylammonium styryl groups.Methods The antibacterial photodynamic activity of compound 3 was determined against sixteen methicillin-resistant Staphylococcus aureus (MRSA) strains, including four ATCC type strains (ATCC 43300, ATCC BAA-42, ATCC BAA-43, and ATCC BAA-44), two mutant strains [AAC(6’)-APH(2”) and RN4220/pUL5054], and ten non-duplicate clinical strains of hospital- and community-associated MRSA. Upon light irradiation, the minimum bactericidal concentrations of compound 3 were in the range of 1.56-50 µM against all the sixteen MRSA strains. Interestingly, compound 3 was not only more active than an analogue in which the ammonium groups are not directly connected to the n-conjugated system (compound 4), but also showed significantly higher (p < 0.05) antibacterial potency than the clinically approved photosensitizer methylene blue. The skin irritation of compound 3 during topical application was tested on human 3-D skin constructs and proven to be non-irritant in vivo at concentrations below 1.250 mM. In the murine MRSA infected wound study, the colony forming unit reduction of compound 3 + PDT group showed significantly (p < 0.05) higher value (>2.5 log10) compared to other test groups except for the positive control.Conclusion In conclusion, the present study provides a scientific basis for future development of compound 3 as a potent photosensitizer for photodynamic therapy for MRSA wound infection.

Using autochthonous Bdellovibrio as a predatory bacterium for reduction of Gram-negative pathogenic bacteria in urban wastewater and reuse it.

Background and Objectives:The microbial contamination of wastewater is associated with health risks. The aim of this study was to use the autochthonous Bdellovibrio potential to prey Gram-negative pathogenic bacteria as a bio-control agent to treat urban wastewater.Materials and Methods:Thirty-six raw sewage samples were collected for isolation of Bdellovibrio. Double layer plaque assay was used for isolation and the isolates were identified by microscopic examination and molecular analysis. To evaluate the predatory potential for decrease number of Gram-negative pathogenic bacteria, plaque perdition assay, reduction in host cells viability by colony-forming unit (CFU) counting, reduction in optical density (OD) in co-cultures and assay of killing efficiency were carried out. Also, the raw wastewater was treated by Bdellovibrio then the reduction in CFU counting and reduction in OD was evaluated.Results:Four strains of Bdellovibrio were isolated and were registered in Gene Bank. Clear plaques were observed after 3–6 days of incubation for all prey cells. The CFU enumerations of all preys were decreased after 48 hrs in co-cultures and raw wastewater. Also, OD was decreased down to 0.2 nm after 48 hrs.Conclusion:These autochthonous Bdellovibrio strains are proposed to use for bio-control of Gram-negative pathogenic bacteria in wastewater and reuse it for irrigation in arid regions.

The Effect of Disinfectants on Quinolone Resistant E. coli (QREC) in Biofilm.

The aim of disinfection is to reduce the number of microorganisms on surfaces which is a challenge due to biofilms. In the present study, six quinolone resistant Escherichia coli (QREC) strains with three different biofilm matrix compositions were included to assess the log10 colony forming units (CFU) reduction effect of three disinfectants at various exposure times on biofilm of different ages and morphotypes. Biofilm was formed on stainless steel coupons for two and five days before transferred to tubes with Virocid 0, 25%, VirkonS 1%, and TP990 1% and left for various exposure times. The biofilms were scraped off and serial dilutions were spread on blood agar plates where colony forming units (CFU) were counted. A mean log10 CFU reduction ≥4 was seen on two-day-old biofilm with VirkonS and Virocid (30 min) but not on five-day old biofilm. TP990 did not display sufficient effect under the conditions tested. The bactericidal effect was inferior to that reported on planktonic bacteria. The findings of this study should be considered when establishing both disinfectant routines and standard susceptibility tests, which further should accommodate E. coli biofilms and not only Pseudomonas as is the case today.

Methicillin-resistant Staphylococcus aureus contamination of hospital-use-only mobile phones and efficacy of 222-nm ultraviolet disinfection

Mobile phones may be contaminated with nosocomial pathogens such as methicillin-resistant Staphylococcus aureus (MRSA). The aim of this study was to investigate the MRSA contamination rate on doctors' hospital-use-only mobile phones and the efficacy of 222-nm ultraviolet light (UV) disinfection. We investigated the MRSA contamination rate of doctors' hospital-use-only mobile phones, as well as the reduction in MRSA counts on plastic plates and aerobic bacteria (AB) on mobile phones before and after exposure to 222-nm UV irradiation. Five (10%) of the 50 mobile phones investigated were contaminated with MRSA. Exposure to 0.1 mJ/cm2 222-nm UVC irradiation for 1.5 and 2.5 min (9 and 15 mJ/cm2) achieved mean log10 MRSA colony-forming units reductions of 2.91 and 3.95, respectively. Exposure to 9 mJ/cm2 222-nm UVC irradiation (0.1 mW/cm2 for 1.5 minutes) significantly reduced AB contamination on mobile phones (P < .001). The use of 222-nm UV disinfection resulted in effective in vitro reduction of MRSA and significantly reduced AB contamination of mobile phone surfaces.