Lactobacillus jensenii mitral valve endocarditis: Case report, literature review and new perspectives

Infective Endocarditis by Lactobacillus Species-A Narrative Review

Bacteria of the genus Lactobacillus are microaerophilic or aerotolerant anaerobic Gram-positive non-spore-forming rods. They are considered essential members of the human gut microbiome; however, recent studies have revealed that these microorganisms are less predominant in the gut microbiome than initially thought. Lactobacillus spp. is mainly known for its use as a probiotic in foods and supplements to prevent and treat specific issues such as infectious diseases, irritable bowel syndrome, and diabetes mellitus. However, Lactobacillus spp. may occasionally cause infections such as bacteremia or infective endocarditis (IE). The present study aimed to review all cases of IE by Lactobacillus spp. and describe the epidemiology, microbiology, clinical characteristics, treatment, and outcomes of this infection by collecting relevant data from studies existing in Pubmed and Scopus until 28 September 2023. A total of 77 studies containing data for 82 patients were included. The median age was 56 years, and 69.6% were male. A prosthetic valve was present in 16% of patients, and 17.3% had previously been on probiotics. The aortic valve was the most commonly involved intracardiac site, followed by the mitral valve. Fever, embolic phenomena, sepsis, and heart failure were the most common clinical presentations. Aminoglycosides and penicillin were the most commonly used antimicrobials for definitive treatment. Surgery was performed in 53.7% of patients. Overall mortality was 17.1%. IE in prosthetic valves and presentation with shock were independently associated with overall mortality.

Gut-Joint Axis: Impact of Bifidobacterial Cell Wall Lipoproteins on Arthritis Development

Gut microbiota affect progression of rheumatoid arthritis (RA). The present study aims at investigating the protective potential of Bifidobacterium longum cell wall lipoproteins (Lpps) shown to modulate the intestinal microbiome and prevent osteoarthritis. Arthritis was induced by collagen (CIA) or anti-collagen antibodies (CAIA) injection. Intake of 0.5 mg of Lpps/L, but not 0.25 and 1 mg of Lpps/L, significantly alleviated RA symptoms in CIA DBA/1OOaHsd mice. The arthritis index (AI) was also reduced in CAIA mice. In the CIA-protected group, colon Ligilactobacillus murinus, caecal Lactobacillus johnsonii and spleen weight correlated with AI, whereas the reverse was observed with splenic CD11c+ dendritic cells (cDCs). The unprotected CIA Lpps group harbored higher cecal and colon E. coli and lower caecal L. murinus. Lpps administration to CAIA mice after arthritis induction led to lower colon E. plexicaudatum counts. Splenocytes from CIA-protected mice triggered by LPS secreted higher Il-10 than control ones. However, a higher IL-10 response was not elicited in gnotobiotic RA mice splenocytes with lower cDCs' recruitment. Labeled bacteria with the Lpps signal were detected in CIA mice bone marrow (BM) cDCs 5 and 16 h post-gavage but not in Peyer's patches and the spleen. In vitro uptake of Lpps by primary BM and thymus cells was observed within 24 h. An FACS analysis detected the Lpps signal in the plasmacytoid cell compartment but not in cDCs. In conclusion, Lpps dosing is critical for preventing arthritis progression and appropriately modulating the microbiome. Our results also highlight the possible triggering of the immune system by Lpps.

Metagenomic sequencing of human cardiac tissue reveals Microbial RNA which correlates with Toll-like receptor-associated inflammation in patients with heart disease

Cardiovascular disease (CVD) is strongly associated with chronic low-grade inflammation, involving activated Toll-like receptors and their downstream cellular machinery. Moreover, CVD and other related inflammatory conditions are associated with infiltration of bacteria and viruses originating from distant body sites. Thus, in this study we aimed to map the presence of microbes in the myocardium of patients with heart disease that we previously found to display upregulated Toll-like receptor signaling. We performed metagenomics analysis of atrial cardiac tissue from patients undergoing coronary artery bypass grafting (CABG) or aortic valve replacement (AVR) and compared with atrial cardiac tissue from organ donors. A total of 119 species of bacteria and seven species of virus were detected in the cardiac tissue. RNA expression of five bacterial species were increased in the patient group of which L. kefiranofaciens correlated positively with cardiac Toll-like receptor-associated inflammation. Interaction network analysis revealed four main gene set clusters involving cell growth and proliferation, Notch signaling, G protein signaling and cell communication in association with L. kefiranofaciens RNA expression. Taken together, intracardial expression of L. kefiranofaciens RNA correlates with pro-inflammatory markers in the diseased cardiac atrium and may have an effect on specific signaling processes important for cell growth, proliferation and cell communication.

Lactobacilli Infection Case Reports in the Last Three Years and Safety Implications

Lactobacilli constitute the dominant microbiota in many fermented foods and comprise widely used probiotics. However, these bacteria cause rare infections mostly in diabetic and immunocompromised subjects in presence of risk factors such as prosthetic hearth valves and dental procedures or caries. The scope of this survey was re-assessing the pathogenic potential of lactobacilli based on the infection case reports published in the last three years. In 2019, 2020, and 2021, total of 17, 15, and 16 cases, respectively, including endocarditis, bacteremia, and other infections, were reported. These annual numbers are higher than those observed previously. Lacticaseibacillus rhamnosus (13 cases), comprising strain GG (ATCC 53103) with established applications in healthcare, L. paracasei (7 cases), Lactobacillus acidophilus (5 cases), L. jensenii (5 cases), Lactiplantibacillus plantarum (3 cases), L. paraplantarum, L. delbrueckii subsp. delbrueckii, L. gasseri, L. paragasseri, Limosilactobacillus fermentum, and L. reuteri (1 case each) were involved. Virulence characterization of two strains that caused infections, a derivative of L. rhamnosus GG and L. paracasei LP10266, indicated that increased biofilm-forming capacity favors pathogenicity and it is determined by variable genetic traits. This survey highlights that the strains of lactobacilli that cause infections are little characterized genetically. Instead, to avoid that these bacteria become a hazard, genetic stability should be periodically re-evaluated by whole genome sequencing (WGS) to ensure that only non-pathogenic variants are administered to vulnerable individuals.