Microecology of aerobic denitrification system construction driven by cyclic stress of sulfamethoxazole.

The construction of aerobic denitrification (AD) systems in an antibiotic-stressed environment is a serious challenge. This study investigated strategy of cyclic stress with concentration gradient (5-30 mg/L) of sulfamethoxazole (SMX) in a sequencing batch reactor (SBR), to achieve operation of AD. Total nitrogen removal efficiency of system increased from about 10 % to 95 %. Original response of abundant-rare genera to antibiotics was changed by SMX stress, particularly conditionally rare or abundant taxa (CRAT). AD process depends on synergistic effect of heterotrophic nitrifying aerobic denitrification bacteria (Paracoccus, Thauera, Hypomicrobium, etc). AmoABC, napA, and nirK were functionally co-expressed with multiple antibiotic resistance genes (ARGs) (acrR, ereAB, and mdtO), facilitating AD process. ARGs and TCA cycling synergistically enhance the antioxidant and electron transport capacities of AD process. Antibiotic efflux pump mechanism played an important role in operation of AD. The study provides strong support for regulating activated sludge to achieve in situ AD function.

Microbial community and antibiotic resistance genes of biofilm on pipes and their interactions in domestic hot water system.

This study aimed to explore the dynamics of microbial communities and antibiotic resistance genes (ARGs) during biofilm formation on polypropylene random (PPR), polyvinyl chloride and stainless steel pipes in domestic hot water system (DHWS), as well as their interactions. Full-scale classification was used to divide abundant and rare genera with 0.1% and 1% as the thresholds. The biofilm community structure presented a temporal pattern, which was mainly determined by conditionally rare or abundant taxa (CRAT) and conditionally rare taxa (CRT). The dynamics of microbial community during biofilm formation were observed, and the effect of pipe material on conditionally abundant taxa (CAT) and CRAT was greater than CRT and rare taxa (RT). CRAT showed the most complex internal associations and were identified as the core taxa. Notably, CRT and RT with low relative abundance, also played an important role in the network. For potential pathogens, 17 genera were identified in this study, and their total relative abundance was the highest (3.6-28.9%) in PPR samples. Enterococcus of CRAT was the dominant potential pathogen in young biofilms. There were 36 more co-exclusion patterns (140) observed between potential pathogens and nonpathogenic bacteria than co-occurrence (104). A total of 38 ARGs were predicted, and 109 negative and 165 positive correlations were detected between them. Some potential pathogens (Escherichia/Shigella and Burkholderia) and nonpathogenic bacteria (Meiothermus and Sphingopyxis) were identified as the possible hosts of ARGs. This study is helpful for a comprehensive understanding of the biofilm microbial community and ARGs, and provides a reference for the management and biosafety guarantee of newly-built DHWS.

[Effect of the liposome albendazole and Huai-Er fungus extract on hepatic infection of Echinococcus granulosus in mice].

OBJECTIVE: To explore the effect of Huai-Er fungus extract (HEF) and liposome albendazole (L-ABZ) on the hepatic infection of Echinococcus granulosus (Eg) in mice, and understand the influence of improved host immunity on postoperative recurrence. METHODS: Female Kunming mice were immune by intraperitoneal injection Eg cyst fluid from sheep, IgG positive mice were divided into drug treatment groups (A, B and C) and control group (D). Mice in group A were administered by gavage with single L-ABZ (75 mg/kg), group B with single HEF (15,000 mg/kg), and group C with combination therapy (L-ABZ 75 mg/kg plus HEF 15,000 mg/kg), once every two days for one week. The protoscoleces were treated with balanced solution for 20 minute and inoculated in the liver by open abdomen of the anesthetized mice. Imitating to an "open sub-adventitial total exocystectomy", protoscoleces outside the cyst led to a reinfection. 72 hours later, groups A, B and C were re-treated for a month. Mice in group D were given with distilled water (0.3 ml per mouse). Group E was set as blank control (n=8). Another 120 IgG positive mice were divided as groups F, G, H and I, and treated in parallel with the groups A, B, C and D respectively; these mice were inoculated with protoscoleces which were treated in advance with 75% alcohol, 20% hypertonic saline, L-ABZ and PBS for 20 min respectively. In 3 months after infection, all the mice were sacrificed to evaluate the efficacy, which covered infection rate, pathological change, spleen index, level of IgG and IgE, CD4+ and CD8+ cells. RESULTS: The recurrence rate in group C (5.7%) was lower than that of groups A (17.1%) and B (24.2%), with hydatid cysts in white colour and nodular, showing degeneration of the germinal and laminated layers. Groups A, B and C showed lower spleen index (A: 3.84+/-0.86, B: 3.95+/-1.01, and C: 3.27+/-0.52), and lower IgE level (A: 0.06+/-0.08, B: 0.07+/-0.08 and C: 0.03+/-0.03) than group D (5.46+/-0.52 and 0.20+/-0.02, respectively) (P<0.05), especially in group C; and also lowerCD8+ in groups A (16.61+/-3.89), B (18.18+/-3.90) and C (15.38+/-2.63) than group D (32.90+/-4.71) (P<0.05), but higher CD4+/CD8+ in groups A (3.21+/-0.70), B (3.05+/-0.66) and C (3.53+/-0.57) than group D (1.57+/-0.26) (P<0.05), especially in group C. The infection rate of mice in group F, Gand H was 0, 0 and 23.1% respectively, and that of group I, 31.2% (P<0.01). CONCLUSION: The combination of HEF and L-ABZ considerably improves the immunity of the hosts and HEF may have a synergetic action to L-ABZ in reducing the recurrence of "sub-adventitial total exocystectomy". 75% alcohol and 20% hypertonic saline show better effect of inactivating protoscoleces than L-ABZ in surgical operation.