[Effectiveness of the "14 plus 7 day quarantine" and "nucleic acid plus total antibody testing" strategy for screening imported patients with COVID-19 in Xiamen]

Objective: To analysis effectiveness of the "14 plus 7 day quarantine" and "nucleic acid plus total antibody testing" strategy (combined screening strategy) for screenin the imported patients with COVID-19 in Xiamen. Methods: The study populations were overseas travelers arriving in Xiamen from March 17 to December 31, 2020, and overseas travelers who had quarantine outside Xiamen for less than 21 days from July 18 to December 31, 2020. Data were collected and analyzed on the timing of detection, pathways, and test results of the imported patients with COVID-19 after implementing combined screening strategy. Results: A total of 304 imported patients with COVID-19 were found from 174 628 overseas travelers and 943 overseas travelers from other cities. A total of 163 cases (53.6%) were diagnosed by multitime, multisite intensive nucleic acid testing after positive finding in total antibody testing. Among them, 27 (8.9%) were first positive for nucleic acid in 14 plus 7 day quarantine and 136 were first positive for nucleic acid in 14-day quarantine. Only 8 of these individuals were tested positive for nucleic acid after positive total antibody testing. The other 128 individuals were tested positive for nucleic acid after being negative for average 2.3 times (maximum of 6 times). Aditional 155 cases might be detected by using the combined "14 plus 7 day quarantine" and " nucleic acid plus total antibody testing" strategy compared with "14-day quarantine and nucleic acid testing" strategy, accounting for 51.0% of the total inbound infections. So the combined screening strategy doubled the detection rate for imported patients with COVID-19. No second-generation case caused by overseas travelers had been reported in Xiamen as of February 26, 2021. Conclusions: Xiamen's combined screening strategy can effectively screen the imported patients with COVID-19 who were first positive for nucleic acid after 14 day quarantine. Compared with "14 day quarantine and nucleic acid testing", the combined screening strategy improved detection rate and further reduced the risk of the secondary transmission caused by the imported patients with COVID-19.

[Influencing factors for non/low-response to hepatitis-B vaccine in infants of HBsAg positive mothers]

Objective: To investigate the influencing factors for non/low-response to hepatitis B vaccine in infants of HBsAg-positive mothers. Methods: A total of 286 HBsAg-positive pregnant women and their infants were recruited from the Third People's Hospital of Taiyuan during July 2011 to January 2013. The infants were immunized with hepatitis B vaccine according to the 0-1-6 month vaccination schedule and followed up for 12 months. The serum HBV DNA level of mothers, neonates and infants were detected by electro chemilum inescence immunoassay kits and fluorescene quantiative polymerase chain rection. Results: Among 286 infants, the rate of non/low-response to hepatitis B vaccine was 18.53% (53/286). Non-conditional logistic regression analysis indicated that the mother's HBV DNA level ≥1×10(7) copies/ml (OR=2.592, 95%CI: 1.121-5.996) and natural birth (OR=1.932, 95%CI: 1.021-3.654) were the risk factors for non/low-response to hepatitis B vaccine, the risks were 2.592 times and 1.932 times higher compared with the infants whose mothers were HBV DNA negative and the infants whose mothers had cesarean delivery. There was no multiplicative or additive interaction between high HBV DNA load and natural birth (OR=1.055, 95%CI: 0.209-5.321), (RERI=1.617, 95%CI: -4.038-7.272; AP=0.364, 95%CI: -0.527-1.225; SI=1.195, 95%CI: 0.270-13.135). After stratified analysis of mother's HBV DNA level, delivery mode of mothers was not associated with non/low-response of their infants. Conclusion: The mother's load of HBV DNA≥1×10(7) copies/ml might be the factor for non/low-response to hepatitis B vaccine in infants of HBsAg positive mothers.

[Relationship between the HBsAg-positive infection status of mothers and the non/low-response to hepatitis B vaccine of their infants]

Objective: To explore the relationship between the status of HBsAg-positive infection of mothers and the non/low-response to hepatitis B vaccine of their infants. Methods: A total of 225 pairs of mothers and their infants were recruited in our cohort from June 2011 to July 2013. Infants were given three doses of hepatitis B vaccine at hour 24, first month and month 6(t)h respectively and were followed up for one year after birth. HBV serological markers and HBV DNA in the peripheral blood of both mothers and infants were detected by Electro-chemiluminescence immunoassay and fluorescence quantitative Polymerase Chain Reaction. Results: Six HBV infection models were detected in HBsAg-positive mothers, and "HBsAg (+), HBeAg (+), anti-HBc (+)" (model one) and "HBsAg (+), anti-HBe (+), anti-HBc (+)" (model two) accounted for 92.5%(208/225) of all the models. Rate of non/low-response to hepatitis B vaccine in infants born to mothers in model one was lower than those in model two, the differences are statistically significant (χ(2)=4.80, P=0.029). The rate of non/low-response to hepatitis B vaccine in infants showed a downward trend with the rising of HBeAg level in their mothers (χ(2)=4.86, P=0.028). Results from the unconditional logistic regression analysis showed that the HBeAg of the HBsAg-positive mothers was significantly correlated with the low risk of non/low-response to hepatitis B vaccine in infants (OR=0.598, 95%CI: 0.378-0.947). The positive rate of serum HBV DNA in HBsAg-positive mothers was 54.2%, while the rate of non/low-response to hepatitis B vaccine in infants born to HBV DNA positive mothers was similar to those infants born to HBV DNA negative mothers (χ(2)=0.22, P=0.640). Conclusions: "HBsAg (+), HBeAg (+), anti-HBc (+)" and "HBsAg (+), anti-HBe(+), anti-HBc (+)" were the common models seen in HBsAg-positive mothers, and the rate of non/low-response to hepatitis B vaccine was different between the two models. HBeAg of HBsAg-positive mothers might have positive effects on the immune response to hepatitis B vaccine in infants but the mechanisms remained not clear. HBV DNA of the HBsAg-positive mothers did not seem to be correlated with the immune response to hepatitis B vaccine in infants.

[Effect of telbivudine on infants born to HBsAg-positive mothers with non-/hypo-response to hepatitis B vaccine during their second and third trimesters of pregnancy]

Objective: To explore the effect of telbivudine treatment in a prevention program on infants born to HBsAg-positive mothers with non-/hypo-responsiveness to hepatitis B vaccine. Methods: A retrospective cohort study with a total of 321 HBsAg-positive pregnant women and their infants enrolled, was conducted. The mothers were recruited from the Third People' s Hospital of Taiyuan, from July 2011 to January 2013. According to the situation of telbivudine intake in second and third trimesters of pregnancy, the participants were divided into two groups: with telbivudine-treated or as control. The neonates were followed up till the age of 12 months. Maternal, neonatal and infantile HBV-M together with HBV DNA in serum were measured using the electro-chemiluminescence immuno-assay (ECLIA) kits and fluorescence quantitative polymerase chain reaction (FQ-PCR) assay, respectively. Results: The rate of non-/hypo-response was 17.99%. After adjusting the potential confounding factors, the telbivudine treatment on HBsAg-positive mothers in the second and third trimesters of pregnancy seemed as the protective factor for non-/hypo-response to hepatitis B vaccine in infants (aRR=0.119, 95% CI: 0.014-0.974). Levels of IFN-γ and IL-10 in telbivudine-treated group were higher than those in the controls (aRR=8.684, 95%CI: 1.977-38.140; aRR=5.330, 95% CI: 1.278-22.236). When the serum levels of IFN-γ and IL-10 in neonatal peripheral blood were higher than 228.47 pg/ml and 174.05 pg/ml respectively, the infants were less likely to be non-/hypo-responsive to the hepatitis B vaccine (aRR=0.300, 95%CI: 0.105-0.857) (aRR= 0.104, 95% CI: 0.030-0.354). Conclusion: Telbivudine treatment provided for the HBsAg-positive mothers in second and third trimesters of pregnancy were less likely to develop non-/low-responsive to hepatitis B vaccine in infants since IFN-γ and IL-10 might have played a vital role in this process.

Cloning and characterization of the rpfC gene of Xanthomonas oryzae pv. oryzae: involvement in exopolysaccharide production and virulence to rice

rpfC is one of a cluster of genes which coordinately regulate the synthesis of extracellular enzymes and exopolysaccharide and pathogenicity in Xanthomonas campestris pv. campestris, the black rot pathogen of brassicas. An rpfC homolog which could functionally complement an rpfC mutant of X. campestris pv. campestris was identified in Xanthomonas oryzae pv. oryzae and the gene was characterized. Mutation of this gene in X. oryzae pv. oryzae had no effect on extracellular enzymes, but exopolysaccharide synthesis and virulence to rice were substantially reduced.

[Multivariate analysis on factors associated with preterm delivery]

In order to estimate the occurrence of Preterm Delivery (PD) and factors associated with PD, 1141 perinatal cases at first affiliated hospital were collected by the method of systematic random sampling. The occurrence rate of PD was 6.0%. Multivariate analysis revealed that the history of premature birth, twin pregnancy, polyhydramnios, placenta praevia, premature rupture of fetal membranes and Bart's fetal hydrops were the main risk factors with statistical significance. Path analysis showed that the history of premature birth had indirect positive effect (elevating risk of PD) on PD through premature rupture of the fetal membranes and Bart's fetal hydrops. Similarly, twin pregnancy had indirect positive effect through premature rupture of the fetal membranes and polyhydramnios. It is suggested that proper health care of the pregnant mother attending to the risk factors should be emphasized to prevent the occurrence of PD.