Streptococcus sanguinis-Introduction, Morphology, Pathogeni

Introduction

Table of Contents

Streptococcus sanguinis is a Gram-positive bacterium belonging to the Streptococcaceae family. It is a commensal bacterium commonly found in the human oral cavity and is part of the normal oral microbiota. While it generally coexists peacefully with its host, S. sanguinis can also play a role in various oral diseases and infections under certain conditions.

Morphology

Streptococcus sanguinis is a Gram-positive bacterium with specific morphological characteristics. Below are key features of the morphology of Streptococcus sanguinis:

Cell Shape: It typically appears as cocci, which are spherical or ovoid-shaped bacterial cells. Cocci are a common shape among streptococci.
Arrangement: The cells are arranged in pairs or short chains. The pairing or chaining arrangement is a result of cell division along a single plane.
Size: The size of individual S. sanguinis cells is relatively small. The cocci are typically in the range of 0.5 to 1.0 micrometers in diameter.
Gram Staining: It is Gram-positive. This means that, after a Gram staining procedure, its cells retain the crystal violet dye, appearing purple or blue under a microscope.
Cell Wall: The cell wall of Streptococcus sanguinis is a critical component of its structure. It contains peptidoglycan, which contributes to the rigidity of the cell wall.
Capsule (Optional): Some strains of S. sanguinis may produce a capsule, which is an outer layer outside the cell wall. The capsule can play a role in adherence to surfaces and evasion of the host immune system.
Motility: It is generally non-motile. Unlike some other bacteria, it lacks flagella and does not exhibit active movement.

Streptococcus sanguinis in wet mount of culture microcopy at a magnification of 1600X — Fig. *Streptococcus sanguinis* in wet mount of culture microcopy at a magnification of 1600X

Colonial Morphology: When grown on agar plates, colonies of Streptococcus sanguinis are circular, smooth, and often exhibit a slightly raised appearance. The color is typically white to grayish.

Pathogenicity

Streptococcus sanguinis is primarily considered a commensal bacterium, meaning that it normally resides harmlessly in the human oral cavity without causing disease. However, under certain conditions, it can become opportunistic and potentially pathogenic, particularly when there is a breach in the host’s defenses or an imbalance in the oral microbiota. Here are key aspects related to the pathogenicity of Streptococcus sanguinis:

Infective Endocarditis: It is a member of the viridans group streptococci and is recognized as one of the bacteria associated with infective endocarditis (IE).
IE is an infection of the endocardium, often affecting heart valves. Individuals with pre-existing heart valve abnormalities or damaged heart valves are more susceptible.
Endovascular Infections: In addition to infective endocarditis, Streptococcus sanguinis has been implicated in other endovascular infections, including bloodstream infections and septicemia.
Biofilm Formation: It is known for its ability to adhere to surfaces and contribute to the formation of dental plaque, a biofilm on tooth surfaces. While this is a normal part of oral microbiota, dental plaque can lead to dental caries and gingivitis if not adequately managed through oral hygiene practices.
Adherence to Host Tissues: The ability of S. sanguinis to adhere to host tissues, including dental surfaces and the endothelium of heart valves, is a key factor in its pathogenic potential.
Virulence Factors: Although not as extensively studied as some other streptococci, Streptococcus sanguinis possesses certain virulence factors that contribute to its ability to colonize and potentially cause infections. These may include adhesins and factors that aid in evasion of the host immune response.
Immunocompromised Individuals: Immunocompromised individuals, such as those undergoing chemotherapy, organ transplantation, or with weakened immune systems, may be more susceptible to infections caused by S. sanguinis.

Streptococcus sanguinis in Gram Staining of Culture Microscopy at a Magnification of 4000X — Fig. *Streptococcus sanguinis* in Gram Staining of Culture Microscopy at a Magnification of 4000X

Joint Infections (Rare): While less common, there have been rare reports of Streptococcus sanguinis causing joint infections, especially in individuals with predisposing factors.

Lab Diagnosis

The laboratory diagnosis of Streptococcus sanguinis involves a combination of microbiological techniques, biochemical tests, and, in some cases, molecular methods for accurate identification. Here is an overview of the typical steps involved in the laboratory diagnosis:

Sample Collection: Clinical specimens are collected from the suspected infection site. For Streptococcus sanguinis, this may include samples from blood cultures, oral swabs, or other relevant sites depending on the suspected infection.
Culturing: The collected samples are inoculated onto appropriate culture media. For Streptococcus species, blood agar is commonly used. The presence of Streptococcus sanguinis may result in the growth of characteristic colonies.
Colonial Morphology: Its colonies on blood agar are typically circular, smooth, and may have a slightly raised appearance. The color is often white to grayish.
Gram Staining: Gram staining is performed to determine the Gram reaction of the bacteria. Streptococcus sanguinis is Gram-positive, appearing as purple cocci under the microscope.
Hemolysis Pattern: It may show all types of hemolysis on blood agar..
Biochemical Tests: Various biochemical tests are conducted to confirm the identity of Streptococcus sanguinis. These may include tests for catalase negativity, optochin susceptibility, and bile solubility.
Molecular Methods (if needed): In some cases, molecular methods such as polymerase chain reaction (PCR) or DNA sequencing may be employed for definitive identification. Specific primers targeting the 16S rRNA gene or other conserved regions can be used for molecular confirmation.
Serological Identification (if needed): In certain situations, serological methods, including agglutination tests, may be employed for further identification and typing.
Antibiotic Susceptibility Testing: Antibiogram testing may be performed to determine the susceptibility or resistance of Streptococcus sanguinis to various antibiotics. This information is crucial for guiding appropriate treatment.

Fig. Antimicrobial susceptibility testsing (AST) result of Streptococcus sanguinis

Treatment

Streptococcus sanguinis is a commensal bacterium commonly found in the oral cavity, and it is generally considered beneficial for oral health. However, in certain situations, it can become opportunistic and contribute to infections, especially in individuals with weakened immune systems or underlying health conditions. The choice of treatment for S. sanguinis infections may vary depending on the severity of the infection, the site of infection, and the overall health of the individual. Here are general considerations for the treatment of Streptococcus sanguinis infections:

Antibiotics: Antibiotics are the primary treatment for bacterial infections, including those caused by Streptococcus sanguinis. The choice of antibiotics is typically guided by the results of antibiotic susceptibility testing, which helps determine the most effective drug.
Commonly used antibiotics for streptococcal infections include penicillin and amoxicillin. In some cases, other beta-lactam antibiotics or alternatives may be prescribed.
Duration of Treatment: The duration of antibiotic treatment will depend on the type and severity of the infection. For example, infective endocarditis caused by Streptococcus sanguinis may require several weeks of antibiotic therapy.
Follow-Up Cultures: Follow-up cultures and testing may be performed to ensure that the infection has been successfully treated. This is particularly important in cases of invasive infections or where there is a risk of recurrence.
Management of Underlying Conditions: Addressing and managing any underlying health conditions or risk factors is crucial for preventing recurrent infections. This may include optimizing oral health, managing chronic diseases, and addressing immune system deficiencies.
Dental Interventions: Streptococcus sanguinis is commonly associated with the oral cavity, and dental interventions may be necessary, especially if the infection is related to dental procedures or oral hygiene. Dental procedures, such as tooth extractions, may be required in certain cases.
Preventive Measures: Prevention is a key aspect of managing S. sanguinis infections. This includes practicing good oral hygiene, regular dental check-ups, and adherence to any prescribed medications or treatments.
Consultation with Specialists: Depending on the severity and complexity of the infection, consultation with specialists such as infectious disease specialists or cardiologists may be warranted, especially in cases of endocarditis or systemic infections.

Prevention

Streptococcus sanguinis is a commensal bacterium commonly found in the oral cavity. While it is generally harmless, certain preventive measures can help manage its presence and reduce the risk of potential infections. Here are some strategies for the prevention of Streptococcus sanguinis-related issues:

Oral Hygiene Practices: Regular Brushing: Brush your teeth at least twice a day using fluoride toothpaste. This helps remove dental plaque, where S. sanguinis may reside.
Flossing: Regular flossing helps clean between teeth and along the gumline, areas where bacterial biofilms can accumulate.
Dental Check-ups: Schedule regular dental check-ups and cleanings. Professional cleanings by a dentist or dental hygienist can help remove plaque and tartar that may harbor bacteria.
Antimicrobial Mouthwashes: Use antimicrobial mouthwashes as recommended by your dentist. These mouthwashes may help reduce bacterial counts in the oral cavity.
Proper Nutrition: Maintain a balanced diet rich in fruits, vegetables, and whole grains. Adequate nutrition supports overall oral health and may contribute to a balanced oral microbiome.
Avoidance of Tobacco: Avoid smoking and using tobacco products, as these can contribute to oral health issues and compromise the immune system.
Limiting Sugar Intake: Reduce the consumption of sugary foods and beverages, as they can contribute to the growth of bacteria and the formation of dental plaque.
Hydration: Stay hydrated by drinking plenty of water. Water helps flush away food particles and bacteria, promoting a healthier oral environment.
Prophylactic Antibiotics (in Certain Cases): In specific medical situations, individuals with a history of infective endocarditis or other high-risk conditions may receive prophylactic antibiotics before certain dental procedures. However, guidelines for antibiotic prophylaxis have evolved, and it is crucial to consult with a healthcare professional to determine the appropriate course of action.

Good Overall Health Practices: Maintaining good overall health practices, including regular exercise, adequate sleep, and stress management, can contribute to a robust immune system that helps keep oral bacteria in check.

Keynotes

Streptococcus sanguinis is a Gram-positive bacterium commonly found in the oral cavity. While it is generally considered a commensal bacterium, it can become opportunistic and contribute to infections, particularly in individuals with compromised immune systems or underlying health conditions. Here are keynotes related to Streptococcus sanguinis:

Normal Oral Flora:
- Streptococcus sanguinis is a part of the normal oral microbiota, residing on tooth surfaces and mucous membranes.
Coccal Shape:
- The bacterium appears as cocci, which are spherical or ovoid-shaped cells.
Pairs or Short Chains:
- Its cells are typically arranged in pairs or short chains, reflecting the pattern of cell division.
Gram-Positive:
- It is Gram-positive, meaning that its cell wall retains the crystal violet stain in the Gram staining procedure.
Beta-Hemolytic Activity:
- On blood agar, Streptococcus sanguinis may exhibit all types of hemolysis on blood agar.
Biofilm Formation:
- It plays a role in the formation of dental plaque, a biofilm on tooth surfaces. It adheres to dental surfaces and contributes to the complex microbial community in the oral cavity.
Opportunistic Pathogen:
- While typically commensal, Streptococcus sanguinis can become pathogenic in certain conditions, such as when there is a breach in the oral mucosa or in individuals with weakened immune systems.
Infective Endocarditis:
- It is one of the bacteria associated with infective endocarditis (IE), particularly in individuals with pre-existing heart valve abnormalities.
Virulence Factors:
- The bacterium possesses virulence factors, including adhesins, that contribute to its ability to adhere to host tissues and potentially cause infections.
Adherence to Host Tissues:
- It can adhere to host tissues, including dental surfaces and the endothelium of heart valves, which is essential for its pathogenic potential
Importance in Research:
- Streptococcus sanguinis is studied for its role in oral microbiology, bacterial interactions, and its contribution to infectious diseases.

Streptococcus sanguinis-Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynotes