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Mitochondrial antiviral-signaling protein (MAVS), also called IPS-1/VISA/Cardif, is an important molecule involved in host defense and triggers a signal for producing type I IFN. Currently the function of MAVS in ducks (duMAVS) remains largely unclear while significant progress has been made in mammals. In this study, the full-length duMAVS cDNA was cloned from duck embryo fibroblasts (DEFs) for the first time. Tissue specificity analysis showed duMAVS was universally expressed in all detected tissues. DEFs transfected with duMAVS were able to induce interferon-β (IFN-β) expression through activating interferon regulatory factor 1 (IRF1) and nuclear factor kappa B (NF-κB). Both the CARD-like domain and transmembrane domain were required for duMAVS signaling via deletion mutant analysis. In addition, poly(I:C)- or Sendai virus (SeV)-induced IFN-β expression in DEFs were significantly decreased by knock-down of duMAVS with siRNA. Altogether, these results indicate that MAVS is a critical immunoregulator in duck innate immune system. [ABSTRACT FROM AUTHOR]

Tumor necrosis factor receptor-associated factor 6 (TRAF6) plays a pivotal role in activating various signaling cascades as an intracellular signal transducer. Although significant progress has been made clarifying TRAF6 function in mammals, the role of TRAF6 in ducks (duTRAF6) remains poorly understood. In the present study, we cloned the full-length duTRAF6 cDNA from duck embryo fibroblasts (DEFs) for the first time. Real-time quantitative reverse transcription-polymerase chain reaction assays showed that duTRAF6 was widely expressed in different tissues. Overexpression of duTRAF6 activated nuclear factor kappa B (NF-κB) and induced interferon-β expression. Furthermore, a deletion mutant analysis revealed that the duTRAF6 region between aa 115 and 375 was essential for activating NF-κB. In addition, duTRAF6 knockdown by RNA interference significantly reduced poly(I:C)- and Sendai virus-induced NF-κB activation in DEFs. Taken together, our results demonstrate that duTRAF6 plays a crucial immunoregulatory role in the duck innate immune response. [ABSTRACT FROM AUTHOR]

Aim of this study was to investigate the prevalence and genetic environment of the oxazolidinone resistance gene optrA in Streptococcus suis (S. suis) isolates from diseased pigs in China. A total of 178 S. suis isolates were screened for the optrA gene by PCR. The phenotypes and genotypes of optrA -positive isolates were investigated by antimicrobial susceptibility testing, core genome Multilocus Sequence Typing (cgMLST), capsular serotypes determination and whole-genome sequencing (WGS). Fifty-one (28.7%) S. suis isolates were positive for optrA. Phylogenetic analysis indicated that the spread of the optrA among S. suis isolates was primarily due to horizontal transfer. Analysis of S. suis serotypes from diseased pigs revealed substantial diversity. The genetic environment of optrA was complex and diverse and could be divided into 12 different types. Interestingly, we identified a novel integrative and conjugative element ICE Ssu 988S, carrying optrA and erm (T) genes. This is to the best of our knowledge the first report of the optrA and erm (T) co-located on an ICE in S. suis. Our results showed a high prevalence of optrA gene in S. suis isolates in China. Further research is needed to evaluate the importance of ICEs, as they horizontally propagate important clinical resistance genes. [ABSTRACT FROM AUTHOR]

Glässer's disease in pigs caused by Haemophilus parasuis is characterized by a severe membrane inflammation. In our previous study, we have identified activation of the transcription factor NF-κB after H. parasuis infection of porcine epithelial cells. In this study, we found that H. parasuis infection also contributed to the activation of p38/JNK MAPK pathway predominantly linked to inflammation, but not the ERK MAPK pathway associated with growth, differentiation and development. Inhibition of NF-κB, p38 and JNK but not ERK activity significantly reduced IL-8 and CCL4 expression by H. parasuis . We also found TLR1, TLR2, TLR4 and TLR6 were required for NF-κB, p38 and JNK MAPK activation. Furthermore, MyD88 and TRIF signaling cascades were essential for H. parasuis -induced NF-κB activation. These results provided new insights into the molecular pathways underlying the inflammatory response induced by H. parasuis . [ABSTRACT FROM AUTHOR]

It has been recognized that colistin resistance is a growing problem that seriously impairs the clinical efficacy of colistin against bacterial infections. One strategy that has been proven to have therapeutic effect is to overcome the widespread emergence of antibiotic-resistant pathogens by combining existing antibiotics with promising non-antibiotic agents. In this work, antibiotic susceptibility testing, checkerboard assays and time-kill curves were used to investigate the antibacterial activity of the individual drugs and the potential synergistic activity of the combination. The molecular mechanisms of tetrandrine in combination with colistin were analyzed using fluorometric assay and Real-time PCR. To predict possible interactions between tetrandrine and MCR-1, molecular docking assay was taken. Finally, we evaluated the in vivo efficacy of tetrandrine in combination with colistin against MCR-positive Salmonella. Overall, the combination of tetrandrine and colistin showed significant synergistic activity. In-depth mechanistic analysis showed that the combination of tetrandrine with colistin enhances the membrane-damaging ability of colistin, undermines the functions of proton motive force (PMF) and efflux pumps in MCR-positive bacteria. The results of molecular docking and RT-PCR analyses showed that tetrandrine not only affects the expression of mcr -1 but is also an effective MCR-1 inhibitor. Compared with colistin monotherapy, the combination of tetrandrine with colistin significantly reduced the bacterial load in vivo. Our findings demonstrated that tetrandrine serves as a potential colistin adjuvant against MCR-positive Salmonella. • In our study, the combination of tetrandrine and colistin drastically enhanced colistin bactericidal activity compared with monotreatment. • In-depth mechanistic analysis showed that tetrandrine potentiated colistin activity through enhancing the membrane-damaging ability of colistin. • Tetrandrine dramatically undermines the function of PMF and result in decreased intracellular ATP levels. In addition, the activity of efflux pump was significantly inhibited by the addition of tetrandrine in both single or combination treatments. • Tetrandrine not only affects the expression of mcr -1 but also as an effective MCR-1 inhibitor. • The discovery of tetrandrine as a potential adjuvant for colistin therapy in combination therapy for severe infections caused by MCR-1 positive Salmonella. [ABSTRACT FROM AUTHOR]