Lactococcus garvieae: a small bacteria and a big data world

Lactococcus garvieae exerts a critical role in inducing inflammation in dairy mastitis by triggering NLRP3 inflammasome-mediated pyroptosis in MAC-T cells

Lactococcus garvieae (L. garvieae) is a pathogenic bacterium that is Gram-positive and catalase-negative (GPCN), and it is capable of growing in a wide range of environmental conditions. This bacterium is associated with significant mortality and losses in fisheries, and there are concerns regarding its potential as a zoonotic pathogen, given its presence in cattle and dairy products. While we have identified and characterized virulent strains of L. garvieae through phenotyping and molecular typing studies, their impact on mammary tissue remains unknown. This study aims to investigate the pathogenicity of strong and weak virulent strains of L. garvieae using in vivo mouse models. We aim to establish MAC-T cell model to examine potential injury caused by the strong virulent strain LG41 through the TLR2/NLRP3/NF-kB pathway. Furthermore, we assess the involvement of NLRP3 inflammasome-mediated pyroptosis in dairy mastitis by silencing NLRP3. The outcomes of this study will yield crucial theoretical insights into the potential mechanisms involved in mastitis in cows caused by the L. garvieae-induced inflammatory response in MAC-T cells.

Improvement of the Gut Microbiota In Vivo by a Short-Chain Fatty Acids-Producing Strain Lactococcus garvieae CF11

Gut microbiota has strong connections with health. Regulating and enhancing gut microbiota and increasing the population of beneficial microorganisms constitutes a new approach to increasing the efficiency of health status. Although it has been shown that Lactococcus can adjust gut microbiota and be beneficial for the host, little is known about whether strains of Lactococcus petauri can improve the gut microbiota. This study focused on the influence of Lactococcus petauri CF11 on the gut microbiome composition and the levels of short-chain fatty acids (SCFAs) in vivo in healthy Sprague Dawley rats. The present results showed that strain CF11 was able to induce a higher amount of fecal acetic acid and propionic acid and enhance species richness. Moreover, strain CF11 improved the gut microbiota community structure. In the experimental group, the genera Oscillospira, Coprococcus, and Ruminococcus, which are reported to be able to produce SCFAs, are significantly increased when compared with the control group (p < 0.05). Finally, the functions of genes revealed that 180 pathways were upregulated or downregulated in comparison with the control group. Among them, the top-five clearly enriched pathways regarding metabolism included porphyrin and chlorophyll metabolism; C5-Branched dibasic acid metabolism; valine, leucine, and isoleucine biosynthesis; phenylalanine, tyrosine, and tryptophan biosynthesis; and ascorbate and aldarate metabolism. Our data suggest that the SCFAs-producing strain CF11 is a potential probiotic.

Bacteriemia por Lactococcus garvieae: primer caso en Colombia

Lactococcus garvieae es una causa inusual de bacteriemia. No existen guías diagnósticas y terapéuticas actuales disponibles para tratar las infecciones causadas por estos organismos. Con base en un informe de caso, proporcionamos una revisión de la literatura sobre bacteriemia causada por L. garvieae y destacamos los desafíos de diagnóstico y tratamiento de estas infecciones y las implicaciones para el manejo. Comunicamos el primer caso de bacteriemia por Lactococcus garvieae en Colombia.

Studies on the effect of Lactococcus garvieae of dairy origin on both cheese and Nile tilapia (O. niloticus)

The aims of this study were to evaluate the activity of Lactococcus garvieae of dairy origin against pathogenic bacteria during cheese manufacture and its suitability and safety as a probiotic on Nile tilapia (Oreochromis niloticus). For these purposes, Lactococcus garvieae isolated from raw cow milk was tested to control the growth of Staphylococcus aureus in artificially contaminated cheese during storage under refrigeration. Also a feeding experiment was conducted on 120 Oreochromis niloticus using a diet containing Lactococcus garvieae as a probiotic bacteria against pathogenic S. aureus. The findings of this study showed that Lactococcus garvieae of dairy origin produced inhibitory substances against pathogenic microorganisms. The selected strain had a good inhibitory activity against Staphylococcus aureus in artificially contaminated cheese during refrigerated storage. Concerning fish experiment, it showed no evidence of disease in fish that were fed a diet containing Lactococcus garvieae, and showed a higher survival rate than others. Further investigations for purification of the produced inhibitory substance and confirming that is a bacteriocin-like substance are needed. Nonetheless, it is the first report of using L. garvieae of dairy origin as a probiotic for controlling the pathogenic Staphylococcus aureus in Oreochromis niloticus.

Transcriptome analysis of grey mullet (Mugil cephalus) after challenge with Lactococcus garvieae

Grey mullet (Mugil cephalus) is an economically important fish species in Taiwan mariculture industry. Moreover, grey mullet are common hosts of a bacterial infection by Lactococcus garvieae. However, until now the information related to the immune system of grey mullet is unclear. Therefore, to understand the molecular basis underlying the host immune response to L. garvieae infection, Illumina HiSeq™ 2000 was used to analyse the head kidney and spleen transcriptome of infected grey mullet. De novo assembly of paired-end reads yielded 55,203 unigenes. Comparative analysis of the expression profiles between bacterial challenge fish and control fish identified a total of 7192 from head kidney and 7280 in spleen differentially expressed genes (P < 0.05), including 4211 upregulated genes and 2981 downregulated genes in head kidney, while in spleen 3598 genes were upregulated and 3682 downregulated. A significant enrichment analysis of these differentially expressed genes (DEG) in spleen and head kidney revealed major immune-related pathways, including complement and coagulation cascades, Toll-like receptor signalling, and antigen processing and presentation. Moreover, selected DEGs were validated using qPCR. Altogether, the results obtained on immune-related genes may allow for a better understanding of immunity in grey mullet to Lactococcus garvieae, carrying out detailed functional analysis of these genes and developing strategies for efficient immune protection against infections in grey mullet.