Aeromonas veronii virulence and adhesion attenuation mediated by the gene aodp

Aeromonas veronii tolC modulates its virulence and the immune response of freshwater pearl mussels, Hyriopsis cumingii

Aeromonas veronii is an opportunistic pathogen that causes diseases in aquatic animals, but its key virulence factors remain unclear. We screened the gene tolC with significantly different expression levels in the two isolates, A. veronii GL2 (higher virulence) and A. veronii FO1 (lower virulence). Therefore, we constructed mutant strain ΔtolC and analyzed its immunological properties. ΔtolC exhibited the reduced ability of biofilms formation, inhibited envelope stress response mediated by several antibiotics except cefuroxime, implying the ability to evade host immunity might be restrained. Challenge tests showed that the LD50 of ΔtolC was 10.89-fold than that of GL2. Enzymatic activities of ΔtolC group were significantly lower and peak time was delayed to 12 h, as demonstrated by qRT-PCR results. Histopathological examination displayed that the degree of tissue damage in ΔtolC group was alleviated. The results show that tolC is an important virulence factor of A. veronii, which provides references for live-attenuated vaccine.

Antimicrobial resistance in aeromonads and new therapies targeting quorum sensing

Aeromonas species (spp.) are well-known fish pathogens, several of which have been recognized as emerging human pathogens. The organism is capable of causing a wide spectrum of diseases in humans, ranging from gastroenteritis, wound infections, and septicemia to devastating necrotizing fasciitis. The systemic form of infection is often fatal, particularly in patients with underlying chronic diseases. Indeed, recent trends demonstrate rising numbers of hospital-acquired Aeromonas infections, especially in immuno-compromised individuals. Additionally, Aeromonas-associated antibiotic resistance is an increasing challenge in combating both fish and human infections. The acquisition of antibiotic resistance is related to Aeromonas' innate transformative properties including its ability to share plasmids and integron-related gene cassettes between species and with the environment. As a result, alternatives to antibiotic treatments are desperately needed. In that vein, many treatments have been proposed and studied extensively in the fish-farming industry, including treatments that target Aeromonas quorum sensing. In this review, we discuss current strategies targeting quorum sensing inhibition and propose that such studies empower the development of novel chemotherapeutic approaches to combat drug-resistant Aeromonas spp. infections in humans. KEY POINTS: • Aeromonas notoriously acquires and maintains antimicrobial resistance, making treatment options limited. • Quorum sensing is an essential virulence mechanism in Aeromonas infections. • Inhibiting quorum sensing can be an effective strategy in combating Aeromonas infections in animals and humans.

A Study on Differential Biomarkers in the Milk of Holstein Cows with Different Somatic Cells Count Levels

Dairy cow mastitis is one of the common diseases of dairy cows, which will not only endanger the health of dairy cows but also affect the quality of milk. Dairy cow mastitis is an inflammatory reaction caused by pathogenic microorganisms and physical and chemical factors in dairy cow mammary glands. The number of SCC in the milk of dairy cows with different degrees of mastitis will increase in varying degrees. The rapid diagnosis of dairy cow mastitis is of great significance for dairy cow health and farm economy. Based on the results of many studies on the relationship between mastitis and somatic cell count in dairy cows, microflora, and metabolites in the milk of Holstein cows with low somatic cell level (SCC less than 200,000), medium somatic cell level (SCC up to 200,000 but less than 500,000) and high somatic cell level (SCC up to 5000,00) were analyzed by microbiome and metabolic group techniques. The results showed that there were significant differences in milk microbiota and metabolites among the three groups (p < 0.05), and there was a significant correlation between microbiota and metabolites. Meanwhile, in this experiment, 75 differential metabolites were identified in the H group and L group, 40 differential metabolites were identified in the M group and L group, and six differential microorganisms with LDA scores more than four were found in the H group and L group. These differential metabolites and differential microorganisms may become new biomarkers for the diagnosis, prevention, and treatment of cow mastitis in the future.

Bacterial diversity of middle ear cholesteatoma by 16S rRNA gene sequencing in China

In this study, the bacterial diversity of acquired middle ear cholesteatoma (MEC) was evaluated to reveal its pathogenesis and provides a guide for the use of antibiotics. Twenty-nine cases of acquired MEC and eight cases of healthy middle ears undergoing cochlear implantation (CI) were evaluated. Full-length 16S rRNA gene sequencing was performed to profile the bacterial communities in lesions and healthy tissues of the middle ear. ACE (P = 0.043) and Chao1 (P = 0.039) indices showed significant differences in alpha diversity (P < 0.05). Analysis of PERMANOVA/Anosim using the Bray-Curtis distance matrix results suggested that the between-group differences were greater than the within-group differences (R = 0.238, P < 0.05, R² = 0.066, P < 0.05). Bacterial community analysis revealed that Alphaproteobacteria at the class level and Caulobacterales and Sphingomonadales at the order level were significantly different (P < 0.05). In the LefSe (Linear discriminant analysis effect size) analysis, Porphyromonas bennonis was elevated, and Bryum argenteum and unclassified Cyanobacteriales were reduced at the species level in MEC (P < 0.05). Fifteen metabolic pathways were found to be significantly different between the two groups by analysing the abundance of metabolic pathways in level 2 of the Kyoto Encyclopaedia of Genes and Genomes (KEGG). Seven and eight metabolic pathways were significantly elevated in the MEC and control groups, respectively (P < 0.05). The role of bacteria in the pathogenesis of acquired MEC was further refined through analysis of metabolic pathways. These findings indicate that the acquired MEC and healthy middle ear contain more diverse microbial communities than previously thought.

Detection of changes in biological characteristics of Aeromonas veronii TH0426 after deletion of lsrB gene by homologous recombination

Aeromonas veronii is a widespread pathogenic microorganism that can infect humans, animals, and a variety of aquatilia, at the same time, can cause diseases, mainly sepsis and ulcer syndrome. In this research, we first deleted the gene of lsrB's nucleotide sequences by homologous recombination. The results showed that the median lethal dose (LD₅₀) of the mutant strain (ΔlsrB) for zebrafish was 1.28-times higher than that of the TH0426 strain. The toxicity of TH0426 to epithelioma papulosum cyprini (EPC) cells was 1.15-times and 1.64-times higher than that of ΔlsrB, 1 and 2 h after infection. The production ability of the biofilm of ΔlsrB decreased by 1.38-times, and the adhesion ability of ΔlsrB to EPC cells greatly decreased by 1.96-times than the TH0426. The result of motility detection pointed out that the swimming ability of ΔlsrB was down by 1.67-times. The results indicated that almost all of them lost their flagella after deleting the lsrB gene. In general, the virulence of TH0426 was reduced after deleting the lsrB gene. The final results point out that the lsrB gene of TH0426 is related to motility, biofilm formation, adhesion, and virulence.