ABSTRACT
Objective: To refine the infectious doses of enteric bacterial pathogens in animal assays and vaccine clinical trials by studying the invasion kinetics of five bacterial pathogens with human intestinal cells. Methods: Utilizing in vitro cultured cell invasion assays with gentamicin-killing step, the invasive effects were analyzed in foodborne pathogens including Salmonella, Shigella, Yersinia, Escherichia coli (E. coli) O157 and opportunistic pathogens Cit-robacter in human embryonic intestine 407 cells and ileocecum HCT-8 cells at multi-plicities of infection(MOIs)of 0.04–4 000.00 E.coli HS served as a noninvasive control. Results: The study results showed that the bacterial invasive efficiency and the average number of internalized bacteria per host cell changed with different starting MOIs.Higher starting MOIs did not always produce more bacterial internalization. The bacterial in-vasion effects varied with different bacterial strains and host cell lines.E.coli O157:H7 did invade human ileocecum HCT-8 cells. Conclusions: This study shows that these bacteria possess different invasive patterns at various starting MOIs and also in different cell lines.The results could help to figure out the appropriate infectious doses of the bacteria in animal assays and in vaccine clinical trials.The bacterial invasion kinetics is also valuable in evaluating the safety and efficacy of live attenuated bacterial vaccines.
ABSTRACT
Objective To explore the status of Keshan disease in Shaanxi province to provide a scientific basis for decision-making of prevention and control of Keshan disease. Methods Nineteen infected villages were randomly selected in 19 infected counties in the range of Keshan disease infected area in Shaanxi province in 2008 as the investigation sites. Clinical examination and electrocardiography were performed in the chosen people at every spots, chest X-ray of posteroanterior position film in 2-meter distance was taken in suspicious cardiac patients, and determining the selenium contents was also determined in the collected grain samples of the investigators. Results Of the 10 228 investigated residents in the endemic area, 110 Keshan disease patients were detected, the total detection rate was 1.08% (110/10 228). Among the 110 patients, 92 were potential Keshan disease, which accounted 0.90%(92/10 228); 18 chronic Keshan disease formed a detection rate of 0.18%( 18/10 228); no acute and sub-acute type of Keshan disease had been inspected. Potential Keshan disease patients often showed electrocardiogram abnormality of complete fight bundle branch block [48.57%(51/105)], ST-T change[ 19.05% ( 20/105 ) ], frequent premature ventricular contraction [ 10.48 % ( 11/105 ) ], left ventricular hypertrophy [ 5.71% (6/105) ], block in the anterosuperior division of the left branch[5.71%(6/105)]; Chronic of Keshan patients mostly presented atrial fibrillation [ 24.00% (6/25) ], left ventricular hypertrophy [ 20.00% (5/25) ], complete right bundle branch block [ 20.00% (5/25)]. The increase rate of cardiothoracie ratio was 18.08% (32/177). Food samples of wheat, corn, millet and rice in infected area residents were of selenium content, being (0.096± 0.028), (0.089 ±0.029), (0.087 ± 0.016), (0.047 ± 0.016)mg/kg, respectively. Conclusions Keshan disease in Shaanxi province is steadily declining, potential and chronic Keshan diseases are currently the main clinical types. Selenium content of food in endemic area has reached the level of the non-endemic area.