Effects of fermentation products of the commensal bacterium Clostridium ramosum on motility, intracellular pH, and flagellar synthesis of enterohemorrhagic Escherichia coli

Clostridium ramosum Bacteremia With Mesenteric Ischemia Secondary to Superior and Inferior Mesenteric Arteries Occlusion

Clostridium ramosum, despite being a common enteric bacterium, is not commonly identified as the cause of pathologic infections in humans. It was first identified by Veillion and Zuber in 1898 from a patient with pulmonary gangrene and appendicitis. After performing an extensive literature search of major databases, only a few cases of pathologic C. ramosum infection were found in the medical literature. In this piece of work, we add to existing research by presenting a case report of an 83-year-old female who presented with abdominal pain, fever, and shortness of breath, requiring ICU admission due to mesenteric ischemia and C. ramosum bacteremia.

The in Vitro Fermentation of Cordyceps militaris Polysaccharides Changed the Simulated Gut Condition and Influenced Gut Bacterial Motility and Translocation

The motility ability of intestinal lipopolysaccharide (LPS)-producing bacteria determines their translocation to the enterohepatic circulation and works as an infectious complication. In this study, the health effects of Cordyceps militaris polysaccharides (CMPs) were re-evaluated based on whether these polysaccharides could affect the motility of gut commensal LPS-producing bacteria and impede their translocation. The results showed that CMP-m fermentation in the gut could change the chemical environment, leading to a decrease in velocity and a shift in the motility pattern. Further study suggested that detachment/fragmentation of flagella, decreased motor forces, and changed chemical conditions might account for this weakened motility. The adhesion and invasion abilities of gut bacteria were also reduced, with lower expression of virulence-related genes. These results indicated that the health regulation effects of CMP-m might be through decreasing the motility of LPS-producing bacteria, hindering their translocation and therefore reducing the LPS level in the enterohepatic circulation.

Clostridium ramosum bacteremia: A case series at a general acute care hospital

Clostridium ramosum infections have been rarely reported, probably due to underestimating in clinical practice. Seven patients with bacteremia from gastrointestinal sources and skin and soft tissue were recognized between 2009 and 2020. Most of them were older and in compromised status, and they had risk factors including cancer, diabetes, liver cirrhosis, gangrene, and pressure ulcers. The source of infections was considered bacterial translocation from the gastrointestine and the skin and soft tissue infections. All patients were treated with antimicrobials, and two received surgical interventions. Four patients died secondary to sepsis due to C. ramosum. The bacteremia of C. ramosum should be appropriately evaluated and treated, especially in compromised hosts.

The Two-Component System DcuS-DcuR Is Involved in Virulence and Stress Tolerance in the Poplar Canker Bacterium Lonsdalea populi

The gram-negative bacterium Lonsdalea populi causes an emerging poplar (Populus × euramericana) canker resulting in severe losses to poplar production in China and Europe. Two-component signal transduction systems play important roles in the regulation of virulence and stress responses in phytopathogenic bacteria. We identified a two-component pair (Lqp2625-Lqp2624) in L. populi, highly homologous to DcuS-DcuR of Escherichia coli. Mutants lacking DcuS or DcuR displayed normal growth while their virulence on poplar twigs was impaired. An inability to produce flagella indicated that DcuS and DcuR are involved in biofilm formation and swimming motility. Moreover, the loss of DcuS or DcuR led to increased sensitivity to oxidative stress and chloramphenicol through downregulation of genes associated with catalases and the multidrug efflux pump, suggesting that the two-component pair contributes to cellular adaptation to oxidative and antibiotic stresses. We identified key domains and putative phosphorylation sites important for virulence and stress responses. Our findings reveal the functions of DcuS-DcuR in virulence and stress responses in L. populi and provide increasing evidence that two-component systems are crucial during the infection process and stress adaptation in bacteria.

Clostridium ramosum rapidly identified by MALDI-TOF MS. A rare gram-variable agent of bacteraemia

Clostridium ramosum is an enteric anaerobic, endospore-forming, gram-positive rod with a low GC content that is rarely associated with disease in humans. We present a case of C. ramosum bacteraemia. To the best of our knowledge, this is the second case of C. ramosum bacteraemia in an elderly patient presenting with fever, abdominal pain and bilious emesis. We highlight the Gram stain variability, the lack of visualization of spores and the atypical morphology of the colonies that showed C. ramosum in a polymicrobial presentation that initially appeared to show monomicrobial bacteraemia. The microorganism was rapidly identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). We present a comprehensive literature review of 32 cases of clinical infections by C. ramosum in which we describe, if available, sex, age, clinical symptoms, predisposing conditions, other organisms present in the blood culture, other samples with C. ramosum , identification methodology, treatment and outcome.

Short Chain Fatty Acids Commonly Produced by Gut Microbiota Influence Salmonella enterica Motility, Biofilm Formation, and Gene Expression

Short chain fatty acids (SCFAs) are commonly produced by healthy gut microbiota and they have a protective role against enteric pathogens. SCFAs also have direct antimicrobial activity against bacterial pathogens by diffusion across the bacterial membrane and reduction of intracellular pH. Due to this antimicrobial activity, SCFAs have promising applications in human health and food safety. In this study, the minimum inhibitory concentrations (MICs) of four SCFAs (acetic acid, butyric acid, propionic acid, and valeric acid) in Salmonella strains isolated from poultry were determined. The effect of subinhibitory concentrations of SCFAs in Salmonella biofilm formation, motility, and gene expression was also evaluated. Butyric acid, propionic acid, and valeric acid showed a MIC of 3750 µg/mL in all strains tested, while the MIC of acetic acid was between 1875 and 3750 µg/mL. Subinhibitory concentrations of SCFAs significantly (p < 0.05) reduced the motility of all Salmonella strains, especially in the presence of acetic acid. Biofilm formation was also significantly (p < 0.05) lower in the presence of SCFAs in some of the Salmonella strains. Salmonella strain. Salmonella Typhimurium T7 showed significant (p < 0.05) upregulation of important virulence genes, such as invA and hilA, especially in the presence of butyric acid. Therefore, SCFAs are promising substances for the inhibition of the growth of foodborne pathogens. However, it is important to avoid the use of subinhibitory concentrations that could increase the virulence of foodborne pathogen Salmonella.

Ion-selective electrode integrated in small-scale bioreactor for continuous intracellular pH determination in Lactobacillus plantarum

The aim of the present study was to develop an ion-selective electrode method for the continuous determination of the intracellular pH in Lactobacillus plantarum using a small-scale bioreactor. This method employed a salicylate-selective electrode basing on the distribution of salicylic acid across the cytoplasmic membrane. This developed electrode responded to salicylate concentrations above 20 μmol/L with a Nernstian sensitivity. The energized and concentrated cells were added into a thermostated small-scale bioreactor that contained the salicylate anions dissolved in a 100 mmol/L potassium phosphate buffer at different pH values. The changes in salicylate concentration that occurred in the medium containing bacterial suspension were measured as a voltage change. The cells of Lactobacillus plantarum showed maintenance of pH homeostasis at the studied pH ranging from 4.0 to 7.0, and they kept a neutral intracellular pH up to 5.8. The simplicity of the measuring preparation and the relatively low cellular concentration, as well as the advantages of the small-scale bioreactor, lead us to believe that the described method can facilitate the study of the physicochemical factors on the intracellular pH of lactic acid bacteria using a single pH probe in one method.