The contribution of reactive oxygen species (ROS) to antimicrobial lethality was examined by treating Escherichia coli with dimethyl sulfoxide (DMSO), an antioxidant solvent frequently used in antimicrobial studies. DMSO inhibited killing by ampicillin, kanamycin, and two quinolones and had little effect on MICs. DMSO-mediated protection correlated with decreased ROS accumulation and provided evidence for ROS-mediated programmed cell death. These data support the contribution of ROS to antimicrobial lethality and suggest caution when using DMSO-dissolved antimicrobials for short-time killing assays. O ne approach to help stem the emergence of new antimicrobial resistance is to kill bacterial pathogens rapidly, thereby quickly reducing bacterial burden and restricting effects of stressinduced mutagenesis (1, 2). Reactive oxygen species (ROS) have been proposed to be key factors in antimicrobial lethality (3-5), and substantial evidence supports this proposition (3-19). However, their role in lethality has been challenged (20, 21). If ROS are indeed integral to antimicrobial-mediated killing, compounds that act as antioxidants and radical scavengers should reduce antimicrobial lethality. We chose to examine this hypothesis using the radical scavenger dimethyl sulfoxide (DMSO) (22, 23), because it is also a popular solvent that is widely used in the pharmaceutical industry and in antimicrobial research due to its (i) low toxicity, (ii) ability to dissolve both organic and inorganic compounds, (iii) ability to remain in a liquid state over a broad temperature range (e.g., from 19°C to 189°C), (iv) ability to enhance cell membrane permeability, and (v) miscibility in water and a wide range of organic solvents. We report here that DMSO interferes with rapid killing of Escherichia coli and Acinetobacter baumannii by members of three antimicrobial classes.E. coli K-12 strains BW25113 and ATCC 25922 and A. baumannii strain ATCC 17978 were grown in Luria-Bertani (LB) broth or on LB agar at 37°C. LB medium, ampicillin, and kanamycin were obtained from Sangon Biotech Co., Ltd. (Shanghai, China). Oxolinic acid, ciprofloxacin, and DMSO were acquired from Sigma-Aldrich Co. (St. Louis, MO). Meropenem (Sumitomo Dainippon Pharma Co. Ltd.) was obtained from Zhongshan Hospital Pharmacy. The fluorescent probe carboxy-H 2 DCFDA [5(6)-carboxy-2=,7=-dichlorodihydrofluorescein diacetate] was purchased from Invitrogen (Grand Island, NY). All chemical stock solutions were dissolved in sterile water (except carboxy-H 2 DCFDA, which was dissolved in DMSO) and stored at Ϫ80°C until use. MICs were assayed by broth dilution according to CLSI protocols (24); exponentially growing cultures were diluted to 10 5 CFU/ml for MIC determinations. To measure rapid bacterial killing, exponentially growing cultures at about 5 ϫ 10 8 CFU/ml were treated with antimicrobials, after which they were serially diluted and plated on drug-free agar. Viable colony counts were determined after an overnight incubation at 37°C; percentage survival rates were calculat...

ObjectivesTo investigate the associations between the overall burden of comorbidity, inflammatory indicators in plasma and Ct values among the elderly with COVID-19.MethodsWe conducted a retrospective observational study. The results of each nucleic acid test of during hospitalization were obtained. Linear regression models assessed the associations between the overall burden of comorbidity, inflammatory indicators in plasma and Ct values among the elderly. A causal mediation analysis was performed to assess the mediation effects of inflammatory indicators on the association between the overall burden of comorbidity and Ct values.ResultsA total of 767 COVID-19 patients aged ≥ 60 years were included between April 2022 and May 2022. Patients with a high burden of comorbidity had significantly lower Ct values of the ORF gene than subjects with a low burden of comorbidity (median, 24.81 VS 26.58, P < 0.05). Linear regression models showed that a high burden of comorbidity was significantly associated with higher inflammatory responses, including white blood cell count, neutrophil count and C-reactive protein. Also, white blood cell count, neutrophil count, C-reactive protein and the overall burden of comorbidity assessed by age-adjusted Charlson comorbidity index were independent risk factors for the Ct values. A mediation analysis detected the mediation effect of white blood cells on the association between the burden of comorbidity and Ct values, with the indirect effect estimates of 0.381 (95% CI: 0.166, 0.632, P < 0.001). Similarly, the indirect effect of C-reactive protein was -0.307 (95% CI: -0.645, -0.064, P = 0.034). White blood cells and C-reactive protein significantly mediated the relationship between the burden of comorbidity and Ct values by 29.56% and 18.13% of the total effect size, respectively.ConclusionsInflammation mediated the association between the overall burden of comorbidity and Ct values among elderly with COVID-19, which suggests that combined immunomodulatory therapies could reduce the Ct values for such patients with a high burden of comorbidity.

Background: Clostridium difficile (CD) is a major cause of healthcare-associated infections and antibiotic-associated diarrhea in hospitalized patients worldwide. Carriers of toxigenic CD (tCD) have a higher risk of developing CD infections and can transmit CD to the environment and susceptible patients. However, little is known regarding the carriers and transmission of tCD in China.Methods: A multi-center cross-sectional study of tCD colonization (tCDC) was conducted from October 24 to 31, 2014, at 33 hospitals in Shanghai, China. Rectal swabs or stool samples were collected and tested, and the clinical and demographic status, epidemiological data, and blood parameters of 531 participants were recorded. The status of tCDC was defined by a positive result on the nucleic acid amplification test for the tcdA (toxin A), tcdB (toxin B), and cdtAB (toxin CDT) genes after positive bacterial culture. Results:The overall prevalence of CD colonization (CDC) was 19.02%, tCDC accounted for 92.08%, and A+B+CDT-was the dominant genotype (87.13%). The CD infection (CDI) prevalence was 1.51%. Potential tCDC-associated factors were admission to secondary grade hospitals, a body mass index <18.5, hospitalization during the previous 30 days, underlying diseases (including hypertension, diabetes mellitus, coronary heart disease, and respiratory failure), diarrhea during the previous 7 days, and exposure to fluoroquinolones or lansoprazole.Conclusions: This study reveals the prevalence of CDC and tCDC in Shanghai, elucidates several associated factors, contributes to the awareness of the current epidemiology in parts of eastern China and provides new insights for further study and infection control practices.