[Epidemiological characteristics of Yersinia enterocolitica in patients with diarrhea from 2013 to 2019 in Pudong New Area, Shanghai].

Objective: To investigate the epidemiological characteristics of Yersinia enterocolitica in patients with diarrhea in Pudong New Area, Shanghai. Methods: Active surveillance of diarrhea was conducted in 14 sentinel hospitals (three tertiary-level hospitals, nine secondary-level hospitals, and two primary-level hospitals) from January 2013 to December 2019 in Pudong New Area of Shanghai, China base on their location, catchment area, and patient volume. Cold enrichment method was used to isolate Y. enterocolitica and further detection of bioserotype, virulence genes and antimicrobial susceptibility of the isolates were conducted. The difference of rates was determined using chi-square test or Fisher's exact test. Results: A total of 12 941 diarrhea cases were included, and 0.7% (88/12 941) cases were confirmed with Yersinia enterocolitica infection. 67.0% (59/88) cases were single infection, 33.0% (29/88) cases were mixed infections. Detection rates of Y. enterocolitica increased annually (0.3%-1.2%) and were highest in children<5 years of age (1.1%, 37/3 218) and in spring (1.1%, 32/2 998) (χ2 were 18.64 and 9.76, respectively, P<0.05). 58.0% (51/88) cases had watery diarrhea, 15.9% (14/88) had fever and 14.8% (13/88) had vomiting. The predominant bioserotypes were 3/O:3 (53.4%, 47/88), followed by 1A/O:8 (15.9%, 14/88) and 1A/O:5(6.8%, 6/88), respectively. Bioserotype 3/O:3 counted for the highest proportions (89.2%, 33/37) in children <5 years of age. All the strains of bioserotype 3/O:3 harbored ail, ystA, yadA and virF genes, which encoded pathogenic Y. enterocolitica. 11/14 strain of 1A/O:8 and 4/6 strains of 1A/O:5 harbored ystB gene. Most strains were resistant to ampicillin (80.7%,71/88) and amoxicillin/clavulanic acid (71.6%,63/88), and 63.8% (56/88) strains were multidrug resistance (MDR). The difference of antimicrobial resistance rates between 3/O:3 and non 3/O:3 was statistically significant in ampicillin, cefoxitin, nalidixic acid, tetracycline and ampicillin/sulbactam (χ2 was 14.68, 43.80, 41.86, 30.54 and 5.07, respectively, P<0.05). Conclusion: The detection rate of Yersinia enterocolitica was higher in children than in adults in Pudong New Area, Shanghai. The predominant bioserotype was pathogenic 3/O:3 with multidrug resistance.

[Epidemiological and etiological surveillance on infectious diarrhea in Pudong New Area, Shanghai, 2013-2017].

Objective: To understand the epidemiological characteristics of infectious diarrhea pathogens in Pudong New Areas of Shanghai from 2013 to 2017 to provide evidence for control and prevention of the disease. Methods: From Jan 2013 to Dec 2017, active surveillance program on diarrhea was conducted in 14 sentinel hospitals (three tertiary-level and nine secondary-level, and two primary-level hospitals) in Pudong New Areas of Shanghai, based on location, catchment areas and number of patients. All recruited outpatients were interviewed in hospitals, using a standard questionnaire. Stool specimens were collected and tested for five viral and eight bacterial pathogens. Results: A total of 9 301 cases with infectious diarrhea were included, and the overall positive rate was 55.7% (5 179). Positive rates of single virus, single bacteria and mixed infections were 26.7% (2 481), 17.0% (1 579) and 12.0% (1 119), respectively. For single infection, the most commonly detected viruses appeared as norovirus (15.4%, 1 428/9 301) and rotavirus (7.2%, 667/9 301). The most commonly detected bacteria were diarrheagenic Escherichia coli (6.7%, 619/9 301) and non-typhoid Salmonella (3.3%, 305/9 301). The most common mixed infections were caused by virus-bacteria (4.9%, 459/9 301). Norovirus (17.0%, 838/4 938) showed the highest positive rates, followed by Escherichia coli (7.2%, 354/4 938), both seen in the age group of 20-59 years old group. Rotavirus (9.4%, 178/1 896) and non-typhoid Salmonella (4.9%, 93/1 896) were the most common pathogens found in the age group of 0-4 years old. The prevalence of norovirus peaked both in spring and autumn. The other peaks were seen as: Rotavirus in winter, diarrheagenic Escherichia coli in summer and non-typhoid Salmonella in summer. Conclusions: Our data showed that the positive rates of infectious diarrhea pathogens were high in Pudong New Areas of Shanghai from 2013 to 2017. The dominant pathogens would include norovirus, rotavirus and diarrheagenic Escherichia coli but with differenct distributions in age groups. Obvious seasonal patterns were also observed.

[Antimicrobial resistance and molecular epidemiology of foodborne Yersinia enterocolitica in Pudong New District, Shanghai].

Objective: To investigate the antimicrobial resistance and molecular epidemiology of foodborne Yersinia (Y.) enterocolitica in Pudong New District of Shanghai. Methods: Four kinds of raw food samples were collected in retail circulation sites in Pudong from 2012 to 2016. Cold enrichment method was used to isolate Y. enterocolitica and further detection of biotype, serotype, virulent genes, antimicrobial susceptibility of the isolates and pulsed field gel electrophoresis (PFGE) were conducted. Results: A total of 3 900 raw food samples were collected during this period, including poultry product (n=590), livestock product (n=1 074), aquatic product (n=1 488), vegetable (n=748), in which 111 (2.8%) were contaminated by Y. enterocolitica. The detection rates of Y. enterocolitica in poultry product samples (5.3%, 31/590) and livestock product samples (4.5%, 48/1 074) were higher than those in aquatic product samples (1.6%, 24/1 488) and vegetable samples (1.1%, 8/748). The predominant biotype was 1A (95.5%) and predominant serotype was O∶8 (42.3%). All the strains lacked ail, ystA, yadA and virF genes, which encoded pathogenic Y. enterocolitica. Seventy six (68.5%) strains harbored ystB gene, in which 35 (31.5%) belonged to 1A/O∶8/ystB pattern. Most strains were resistant to ampicillin (74.8%) and amoxicillin/clavulanic acid (70.3%), and non-sensitive rate to Cefoxitin was over 50.0%. No third generation cephalosporin or fluoroquinolone resistant strains were detected, but 38.7% (43/111) strains were multidrug resistant (MDR). Serotype O∶8 and O∶5 strains had 44 and 18 PFGE patterns, respectively. Conclusions: The main foodborne exposure sources of Y. enterocolitica in raw food were poultry and livestock products in Pudong New District. 1A/O∶8/ystB was the predominant pattern with potential pathogenicity despite lacks of typical pathogenic virulent genes. The antimicrobial resistant rates of Y. enterocolitica were at a low level, but MDR strains still existed. Molecular types of the isolates showed highly genetic diversity.

Effect of ammonia on methane production pathways and reaction rates in acetate-fed biogas processes.

In order to understand the correlation between ammonia and methanogenesis metabolism, methane production pathways and their specific rates were studied at total ammonium nitrogen (TAN) concentrations of 0.14-9 g/L in three methanogenic sludges fed with acetate, at both mesophilic and thermophilic conditions. Results showed that high levels of TAN had significant inhibition on methanogenesis; this could, however, be recovered via syntrophic acetate oxidation (SAO) coupled with Hydrogenotrophic Methanogenesis (HM) performed by acetate oxidizing syntrophs or through Acetoclastic Methanogenesis (AM) catalyzed by Methanosarcinaceae, after a long lag phase >50 d. Free ammonia (NH3) was the active component for this inhibition, of which 200 mg/L is suggested as the threshold for the pathway shift from AM to SAO-HM. Methane production rate via SAO-HM at TAN of 7-9 g/L was about 5-9-fold lower than that of AM at TAN of 0.14 g/L, which was also lower than the rate of AM pathway recovered at TAN of 7 g/L in the incubations with a French mesophilic inoculum. Thermophilic condition favored the establishment of the SAO-catalyzing microbial community, as indicated by the higher reaction rate and shorter lag phase. The operational strategy is thus suggested to be adjusted when NH3 exceeds 200 mg/L.

Impact of recycled effluent on the hydrolysis during anaerobic digestion of vegetable and flower waste.

Two trials were established to investigate the effect of recycled effluent on hydrolysis during anaerobic co-digestion of vegetable and flower waste. Trial I evaluated the effect by regulating the flow rate of recycled effluent, while Trial II regulated the ratio of hydrolytic effluent to methanogenic effluent, which were recycled to hydrolysis reactor. Results showed that the recirculation of methanogenic effluent could enhance the buffer capability and operation stability of hydrolysis reactor. Higher recycled flow rate was favourable for microbial anabolism and further promoted hydrolysis. After 9 days of hydrolysis, the cumulative SCOD in the hydrolytic effluent reached 334, 407, 413, 581 mg/g at recycled flow rates of 0.1, 0.5, 1.0, 2.0 m3/(m3 x d), respectively. It was feasible to recycling a mixture of hydrolytic and methanogenic effluent to the hydrolysis reactor. This research showed that partially introducing hydrolytic effluent into the recycled liquid could enhance hydrolysis, while excessive recirculation of hydrolytic effluent will inhibit the hydrolysis. The flow ratio 1:3 of hydrolytic to methanogenic effluent was found to provide the highest hydrolysis efficiency and degradation rate of lignocelluloses-type biomass, among four ratios of 0:1, 1:3, 1:1 and 3:1. Under this regime, after 9 days of hydrolysis, the cumulative TOC and TN in the hydrolytic effluent reached 162 mg/g and 15 mg/g, the removal efficiency of TS, VS, C and cellulose in the solid phase were 60.66%, 62.88%, 58.35% and 49.12%, respectively. The flow ratio affected fermentation pathways, i.e. lower ratio favoured propionic acid fermentation and the generation of lactic acid while higher ratio promoted butyric acid fermentation.

[Genetic diversity of Rh haplotypes among Chinese populations].

In the statistic study of Rh blood group system, whole Chinese data were re-calculated for haplotype frequency and linkage ratio, according to Counting Method. All Chinese majority populations and minority populations were divided into different groups, and variety genetic calculations on their gene diversity and gene differentiation were also calculated. The results shown obvious genetic differences between and among Southern and Northern Chinese populations. UPGMA phylogenetic dendrograms was plotted and the tree demonstrated that the genetic relationship among 68 Chinese populations are well corresponded with their geographical and linguistic distribution.