Background: The inner membrane protein DotU of Aeromonas veronii is an important component of the minimal core conserved membrane proteome required for the formation of an envelope-transmembrane complex. This protein functions in a type VI secretion system (T6SS), and the role of this T6SS during the pathogenic process has not been clearly described. Results: A recombinant A. veronii with a partial disruption of the dotU gene (720 bp of the in-frame sequence) (defined as ∆dotU) was constructed by two conjugate exchanges. We found that the mutant ∆dotU allele can be stably inherited for more than 50 generations. Inactivation of the A. veronii dotU gene resulted in no significant changes in growth or resistance to various environmental changes. However, compared with the wild-type strain colony, the mutant ∆dotU colony had a rough surface morphology. In addition, the biofilm formation ability of the mutant ∆dotU was significantly enhanced by 2.1-fold. Conversely, the deletion of the dotU gene resulted in a significant decrease in pathogenicity and infectivity compared to those of the A. veronii wild-type strain. Conclusions: Our findings indicated that the dotU gene was an essential participant in the pathogenicity and invasiveness of A. veronii TH0426, which provides a novel perspective on the pathogenesis of TH0426 and lays the foundation for discovering potential T6SS effectors.

Limited information about Toxoplasma gondii infection in pet cats and their owners is available in China. In this study, blood samples were randomly collected from 306 pet cats and 397 corresponding pet owners in Jilin province, northeastern China. Sera from the pet cats and the pet owners were tested for anti-T. gondii antibodies using an modified agglutination test (MAT) and an enzyme-linked immunosorbent assay (ELISA), respectively. Moreover, the risk factors for T. gondii infection in pet cats and corresponding pet owners were explored. In total, 62 sera out of 306 examined pet cats (20.3%) and 18.1% (72/397) pet cat owners were seropositive for T. gondii, respectively. The results of statistical analysis showed that both pet cats and their owners from rural area had significantly higher T. gondii seroprevalence than those from urban area (p < 0.001). Moreover, owners of pet cas who have the knowledge of zoonotic protozoan diseases had a significantly lower T. gondii seroprevalence than those without the knowledge of zoonotic protozoan diseases (p < 0.001). The present results revealed that the seroprevalence of T. gondii infection are widespread in pet cats and their owners in Jilin province, northeastern China. Residence area and understanding knowledge of zoonotic protozoan diseases are considered to be raleted to the T. gondii infection. Hence, it is necessary to highlight the dangers and protection methods of zoonotic protozoan diseases caused by pet cats, especially in rural area.

Toxoplasma gondii is a worldwide food-borne protozoa that has harmful influences on animal and human health. Raw milk containing T. gondii has been considered as one of the possible infectious sources for humans. Although China is one of the world’s leading milk consumers, there is still no study to investigate the seroprevalence of T. gondii in raw cow milk in China; especially for cows in rural areas. Thus, we conducted this study to examine the specific anti-T. gondii IgG-antibody in the raw milk and sera of domestic cows in China. In total, 894 cows were randomly selected from rural areas in northeastern China. The positive rate of T. gondii in the milk and serum samples were 6.38% (57/894) and 7.16% (64/894), respectively. Moreover, a history of abortion (OR = 2.03, 95% CI: 1.11–3.72, p = 0.022) was identified as the only risk factor for T. gondii infection in the studied cows. This study investigated the seroprevalence of T. gondii in the raw milk and sera of cows in China; it provided timely and useful data for public health and food safety, especially in rural areas.