Epidemiology 

The epidemiology of Enterococcus durans is influenced by several factors, such as the source and mode of transmission, the host susceptibility and immunity, the virulence and resistance of the bacterium, and the environmental and social conditions. Some of the main aspects of the epidemiology of Enterococcus durans are: 

• Source and mode of transmission: Enterococcus durans may spread from animals to people by direct touch or consumption of contaminated food or water. It can also be transmitted from person to person through fecal-oral route or contact with infected body fluids or wounds. The bacterium can colonize various sites in the human body, such as the gastrointestinal tract, the urinary tract, the skin, and the blood. 
• Host susceptibility and immunity: Enterococcus durans can infect both healthy and immunocompromised individuals, but the latter are more prone to develop severe and invasive infections. The risk factors for Enterococcus durans infection include advanced age, underlying diseases (such as diabetes, cancer, renal failure, liver cirrhosis), surgery, trauma, indwelling devices (such as catheters prosthetic valves), antibiotic use, and hospitalization. 
• Virulence and resistance: Enterococcus durans can produce various virulence factors that let it stick to the cells of its host, invade tissues, evade host defenses, and cause tissue damage. Some of these factors include surface proteins (such as Esp), biofilm formation, hemolysin, gelatinase, aggregation substance, and cytolysin. Enterococcus durans can also acquire resistance to multiple antibiotics through various mechanisms, such as mutation, plasmid transfer, or transposon insertion. Some of the antibiotics that Enterococcus durans can be resistant to include penicillin, ampicillin, vancomycin, teicoplanin, gentamicin, streptomycin, erythromycin, tetracycline, chloramphenicol, and quinolones. 
• Environmental and social conditions: Enterococcus durans can survive in various environmental conditions due to its high adaptability. It can tolerate high temperatures, pH, salinity, and disinfectants. It can also persist in soil, water, sewage, fruits, and plants. The spread of Enterococcus durans can be influenced by social factors such as hygiene practices, sanitation facilities, food safety measures, health care systems, antibiotic policies, and infection control programs. 

Classification and Structure 

• Kingdom: Bacteria 
• Phylum: Firmicutes 
• Class:      Bacilli 
• Order:   Lactobacillales 
• Family: Enterococcaceae 
• Genus:  Enterococcus 
• Species: E. durans 

  The structure of Enterococcus durans can be summarized in five points as follows: 

• It is a Gram-positive bacterium, meaning Its cell wall is heavily coated in peptidoglycan that retains the purple color of the Gram stain. 
• It is spherical or ovoid-shaped and usually grows in pairs, short chains, or clusters. 
• Its size ranges from 0.5 to 1.5 micrometers in diameter, and its colonies on agar plates are small, round, and white to cream-colored. 
• It is facultatively anaerobic, meaning it can grow both in the presence and absence of oxygen. 
• It has teichoic acids in its cell wall, which give it a net negative charge and help it adhere to surfaces. It also has various antigenic molecules on its cell wall, such as group-specific carbohydrate antigens, enterococcal surface protein, and aggregation substances. 

Antigenic Types 

Different strains of Enterococcus durans have distinct characteristics and properties. Some of the factors that can be used to differentiate the strains are the cell wall components, the surface proteins, the serovar group, and the probiotic potential. Some examples of Enterococcus durans strains are: 

• ATCC 19432: This is the type of strain of Enterococcus durans, which means it is the reference strain for the species. It was isolated from human feces and has been deposited in various culture collections. 
• KLDS6.0933: This is a potential probiotic strain with high cholesterol removal ability, which was isolated from traditional naturally fermented cream in Inner Mongolia, China. It has a complete genome sequence available and has been studied for its health benefits. 
• HS03: This strain was separated from soft chhurpi, a fermented milk product that the indigenous people of the Himalayan region of Sikkim customarily make. It has a negative bile salt hydrolase (BSH) activity and shows good hypocholesterolemic activity in vitro and in vivo. 
• YY1: This is another strain isolated from soft chhurpi, which has a positive BSH activity and shows good hypocholesterolemic activity in vitro and vivo2. 
• 6kb (B8249), B3371, B2095, CK1025, CK1026, and B3166: These are six strains assigned to the species E. durans that were isolated from different sources, such as cheese, milk, and human feces. They have been used to study the genetic diversity and phylogeny of enterococci. 
• 5 (B8251) and CK1013: These are two strains assigned to E. faecium that were also isolated from cheese and human feces. They have been used to compare with E. durans strains for their genetic diversity and phylogeny. 

Pathogenesis 

The pathogenesis of Enterococcus durans involves several factors, such as the source and mode of transmission, the host susceptibility and immunity, the virulence and resistance of the bacterium, and the host response and damage. Some of the main aspects of the pathogenesis of Enterococcus durans are: 

• Source and transmission: Can spread through contact, contaminated food/water, or person-to-person via fecal-oral route. It can colonize the gut, urinary tract, skin, and blood. 
• Host susceptibility: Affects both healthy and immunocompromised individuals, with risk factors including advanced age, underlying diseases, surgery, trauma, indwelling devices, and antibiotic use. 
• Immunity: The host immune system plays a crucial role in controlling the infection but can also cause tissue damage through inflammation and cytokine release. 
• Virulence and resistance: Enterococcus durans can produce virulence factors and acquire antibiotic resistance, making it more challenging to treat. 
• Host response and damage: The interaction between the bacterium and the host’s immune system can result in tissue damage, which varies based on the site and duration of infection. Understanding this pathogenesis is essential for managing infections in both humans and animals. 

Host Defenses 

The host defenses of Enterococcus durans are the mechanisms that the human or animal body uses to protect itself from the infection caused by this bacterium. Some of the host defenses are: 

• The outermost layers of skin & mucous membranes that prevent the entry of E. durans into the body. 
• The cell-based innate immune system and molecules that recognize and eliminate E. durans without prior exposure. These include macrophages, neutrophils, natural killer cells, complement systems, and cytokines. 
• The adaptable immune system, made up of cells and molecules that develop a specific and long-lasting response to E. durans after exposure. These include B cells, T cells, antibodies, and memory cells. 
• The microbiota, which are the normal bacteria that colonize the gastrointestinal tract and other mucosal surfaces. They can compete with E. durans for nutrients and attachment sites, produce antimicrobial substances, modulate the immune system, and prevent the overgrowth of E. durans. 

Clinical manifestations 

The clinical manifestations of Enterococcus durans infection rely on the infection’s location and intensity, but some common signs and symptoms are: 

• Urinary tract infection: A solid and ongoing need to urinate, a burning sensation when urinating, often passing only little volumes of urine, or urine that is hazy, red, pink, or cola in color, and lower abdominal pain. 
• Wound infection: Redness, swelling, pain, warmth, pus, or drainage at the wound site. 
• Endocarditis: Fever, chills, night sweats, fatigue, shortness of breath, chest pain, heart murmur, weight loss, blood in urine. 
• Bacteremia: Chills and fever, vomiting and nausea, appetite loss, breathing difficulties, rapid heart rate, lightheadedness, rashes on the skin. 

Diagnosis 

Diagnosing Enterococcus durans involves several steps: 

• Culture the bacterium from clinical specimens like blood, urine, or wound swabs. 
• Perform Gram staining to observe its characteristic appearance (Gram-positive cocci in pairs or short chains). 
• Conduct biochemical tests, including catalase, oxidase, mannitol/sorbitol fermentation, and vancomycin susceptibility tests to identify E. durans. 
• Use molecular methods like PCR and PFGE to detect genetic markers and study phylogenetic relationships. 
• Perform antimicrobial susceptibility testing to determine its resistance to antibiotics using methods like disk diffusion and broth dilution. 

Control 

The prevention of Enterococcus durans infections involves: 

• Consistently practicing proper hygiene, like frequent hand washing  
• Cleaning wounds properly. 
• Avoid contact with contaminated objects or surfaces. 

It is also advisable to avoid consuming unpasteurized dairy products or undercooked meat that may harbor the bacterium. Moreover, it is crucial to use antibiotics judiciously and only when prescribed by a doctor. 

In healthcare settings, strict adherence to infection control Protocols is necessary to stop the spread of Enterococcus durans infections. It includes using personal protective equipment, sterilizing medical equipment, isolating infected patients, and monitoring antibiotic resistance patterns. 

References 

• Enterococcus durans: Introduction, Classification, Morphology (medicallabnotes.com) 
• Frontiers | Evaluating the Safety of Potential Probiotic Enterococcus durans KLDS6.0930 Using Whole Genome Sequencing and Oral Toxicity Study (frontiersin.org)