Microparticle-tagged image-based cell counting (ImmunoSpin) for CD4 + T cells.

Affordable point-of-care (POC) CD4 + T lymphocyte counting techniques have been developed as alternatives to flow cytometry-based instruments caring for patients with human immunodeficiency virus (HIV)-1. However, POC CD4 enumeration technologies can be inaccurate. Here, we developed a microparticle-based visual detector of CD4 + T lymphocytes (ImmunoSpin) using microparticles conjugated with anti-CD4 antibodies, independent of microfluidic or fluorescence detection systems. Visual enumeration of CD4 + T cells under conventional light microscope was accurate compared to flow cytometry. Microparticle-tagged CD4 + T cells were well-recognized under a light microscope. ImmunoSpin showed very good precision (coefficients of variation of ImmunoSpin were ≤ 10%) and high correlation with clinical-grade flow cytometry for the enumeration of CD4 + T cells (y = 0.4232 + 0.9485 × for the %CD4 + T cell count, R2 = 0.99). At thresholds of 200 and 350 cells/µL, there was no misclassification of the ImmunoSpin system compared to the reference flow cytometry. ImmunoSpin showed clear differential classification of CD4 + T lymphocytes from granulocytes and monocytes. Because non-fluorescence microparticle-tags and cytospin slides are used in ImmunoSpin, they can be applied to an automatic digital image analyzer. Slide preparation allows long-term storage, no analysis time limitations, and image transfer in remote areas.

Exposure assessment for pesticide residues in agricultural products consumed in the Republic of Korea during 2016-2020.

Pesticide residues in food comprise compounds such as insecticides, fungicides, herbicides, miticides, and plant activators. The insecticides diazinon (O, O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate) and malathion (O, O-dimethyl dithiophosphate of diethyl-mercaptosuccinate) are classified as probably carcinogenic (Group 2A) and the fungicides chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile) and hexachlorobenzene (pentachlophenyl chloride) as possibly carcinogenic to humans (Group 2B) by the International Agency for Research on Cancer under the World Health Organization. In this study, gas chromatographic and gas chromatography-tandem mass spectrometric analyses were used to determine the concentrations of pesticide residues in agricultural products and assess the effects of chronic human exposure to pesticide residues through the consumption of agricultural products during 2018-2020. Food consumption data were obtained from the Korea National Health and Nutrition Examination Survey of 2016-2018. The chronic exposures determined using mean consumption data for the whole population and mean concentrations of the pesticide residues were 5.15E-11 to 2.08E-05 [lower bound (LB)] and 2.41E-07 to 4.69E-05 mg/kg bw/day [upper bound (UB)], corresponding to 0.00012-2.16% of the hazard index (HA). Exposures to pesticide residues, calculated using the 95th percentile of the consumption data, were 0-8.76E-05 (LB) and 9.26E-07 to 1.56E-04 mg/kg bw/day (UB), corresponding to 0.00045-9.41% of the HA. Based on the result of current exposure assessment, it could be considered that the pesticide residues in agricultural products are properly controlled by the regulatory authorities.

Nanoparticle-Based Visual Detection of Amplified DNA for Diagnosis of Hepatitis C Virus.

Rapid, simple, and inexpensive diagnostic point-of-care tests (POCTs) are essential for controlling infectious diseases in resource-limited settings. In this study, we developed a new detection system based on nanoparticle-DNA aggregation (STat aggregation of tagged DNA, STAT-DNA) to yield a visual change that can be easily detected by the naked eye. This simplified optical detection system was applied to detect hepatitis C virus (HCV). Reverse transcription-polymerase chain reaction (RT-PCR) was performed using primers labeled with biotin and digoxigenin. Streptavidin-coated magnetic particles (1 µm) and anti-digoxigenin antibody-coated polystyrene particles (250-350 nm) were added to form aggregates. The limit of detection (LoD) and analytical specificity were analyzed. The STAT-DNA results were compared with those of the standard real-time PCR assay using serum samples from 54 patients with hepatitis C. We achieved visualization of amplified DNA with the naked eye by adding nanoparticles to the PCR mixture without employing centrifugal force, probe addition, incubation, or dilution. The LoD of STAT-DNA was at least 101 IU/mL. STAT-DNA did not show cross-reactivity with eight viral pathogens. The detection using STAT-DNA was consistent with that using standard real-time PCR.

Exposure assessment and safe intake guidelines for heavy metals in consumed fishery products in the Republic of Korea.

Heavy metals in food are non-intentional pollutants such as lead (Pb), cadmium (Cd), and mercury (Hg). Pb, a neurotoxic substance, is classified as a possible carcinogen for humans (group 2B) by the International Agency for Research on Cancer (IARC) under the World Health Organization (WHO). Cd, a substance that causes kidney damage, is classified as a substance that causes human cancer (group 1). In this study, inductively coupled plasma atomic emission spectrometry (ICP-AES) and a mercury analyzer (MA) were used to identify the concentrations of heavy metals (Pb, Cd, Hg) in fishery products and to assess the effects of chronic human exposure to heavy metals via fisheries consumption. Food consumption data were obtained from the Korea National Health and Nutrition Examination Survey (KNHANES 2010-2015), and the mean exposure concentrations for Pb, Cd, and Hg were 0.0067 µg/kg bw/day, 1.1277 µg/kg bw/month, and 0.0872 µg/kg bw/week, respectively. Exposures to Pb, Cd, and Hg using the 95th percentile of the consumption data were 0.0183 µg/kg bw/day, 4.0230 µg/kg bw/month, and 0.2268 µg/kg bw/week, respectively, corresponding to 3, 16, and 6% of the human exposure safety standard. Safe guidelines for the intake of fishery products are proposed to reduce the exposure to and accumulation of heavy metals in humans.

Genetic and phenotypic characterization of tetracycline-resistant Pasteurella multocida isolated from pigs.

Pasteurella multocida causes single or complex respiratory disease in pigs. Although antimicrobial therapy is the most effective treatment for porcine respiratory disease, P. multocida shows increased antimicrobial resistance in Korea. Therefore, we aimed to investigate the phenotypic and genotypic characterization of tetracycline-resistant P. multocida. Thirty-seven of 454 P. multocida isolates from South Korea between 2010 and 2016 were selected. Four tet genes [tet(B) (78.4%), tet(H) (16.2%), tet(C) (5.4%), and tet(O) (2.7%)] were observed. This is the first report of tet(C) in P. multocida. Various virulence factors were observed in both tetracycline-resistant and -susceptible P. multocida isolates. Genes encoding pmHAS and pfhA were more prevalent in tetracycline-resistant than in tetracycline-susceptible isolates. Some virulence factors exhibited association with serogroups. tadD and sodA were common in serogroup A, while hsf-l was significantly associated with serogroup D (p < 0.01). Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) results showed the genetic diversity of tetracycline-resistant P. multocida. MLST showed six different sequence types (ST), with clonal complex 13 encompassing 56.8% of the strains. PFGE was more efficient in differentiating the isolates, and 29 PFGE patterns of the strains were observed. By combining these methods, identical STs and PFGE patterns were observed in isolates from different farms, suggesting that transmission of antimicrobial-resistant P. multocida strains between farms might occur in a geographically discrete population. In future, epidemiological approaches and development of effective vaccines should focus on the major clonal lineages carrying the important virulence factors and frequently observed resistance genes to prevent the transmission and control the disease.

Antimicrobial resistance of Pasteurella multocida strains isolated from pigs between 2010 and 2016.

Pasteurella multocida is one of the significant causes of respiratory infection outbreaks in the Korean pig industry. Although antimicrobial treatment is an effective strategy for controlling respiratory diseases, limited information is available regarding the antimicrobial susceptibility of the pathogens infecting Korean pigs. Therefore, in this study, we evaluated the antimicrobial resistance of P multocida against widely used antimicrobials in order to enable the selection of appropriate drugs and to evaluate any trends in resistance. A total of 454 isolates of P multocida were collected from all provinces in Korea between 2010 and 2016. Antimicrobial susceptibility of all isolates was determined using a broth microdilution method. The most frequently observed resistance was to sulphadimethoxine (76.0 per cent), followed by oxytetracycline (66.5 per cent), chlortetracycline (36.8 per cent) and florfenicol (18.5 per cent). Although no consistent increase or decrease in resistance was observed for most antimicrobials, resistance to fluoroquinolones tended to increase over the study period. A variety of resistance patterns were observed, most frequently for tetracyclines and sulphonamides. These findings could provide information enabling the selection of optimal antimicrobials for efficient treatment of pneumoniae pasteurellosis in pig farms, which would impede the emergence of antimicrobial resistance.