Understanding Diphtheria: Causes, Symptoms, Treatment
Diphtheria is a severe bacterial infection caused by Corynebacterium diphtheriae, primarily affecting the throat and skin. It forms a characteristic pseudomembrane that can impede breathing. The bacterium produces a potent toxin damaging vital organs like the heart and nerves. Prompt treatment with antitoxin and antibiotics is crucial to prevent severe complications and potential fatality.
Key Takeaways
Diphtheria is a serious bacterial infection caused by Corynebacterium diphtheriae.
A potent toxin causes organ damage and severe disease complications.
Symptoms include sore throat, fever, and a distinctive pseudomembrane.
Diagnosis relies on clinical signs and laboratory confirmation.
Treatment involves antitoxin and antibiotics; vaccination prevents infection.
What is the causative agent of Diphtheria?
Diphtheria is caused by Corynebacterium diphtheriae, a Gram-positive, facultative anaerobic bacterium. This rod-shaped organism displays unique V, K, or L morphologies, often forming a "Chinese letter" pattern. It is non-motile, non-capsulated, and non-sporing. Identification includes metachromatic granules, staining green and bluish-black with Albert stain. Its potent exotoxin defines the disease's severity.
- Gram-positive, facultative anaerobic bacillus
- V, K, or L shapes; "Chinese letter" pattern
- Metachromatic granules (volutin) present
- Non-motile, non-capsulated, non-sporing
What are the different biotypes of Corynebacterium diphtheriae?
Corynebacterium diphtheriae has distinct biotypes, linked to varying disease severity and colony appearances. Gravis causes the most serious illness, forming large, irregular, gray colonies. Mitis leads to milder disease, producing small, round, convex, black colonies. Intermedius presents with long-barred forms and clubbed ends, causing intermediate severity, and forms small, flat, gray colonies.
- Gravis: Most serious; large, irregular, gray colonies
- Mitis: Mild illness; small, round, convex, black colonies
- Intermedius: Intermediate severity; small, flat, gray colonies
How is Corynebacterium diphtheriae cultivated in the laboratory?
Laboratory cultivation of Corynebacterium diphtheriae is essential for diagnosis, utilizing specific media. Loeffler's serum slope yields creamy white colonies within 6-8 hours. Potassium tellurite medium is particularly effective, producing characteristic black colonies that aid differentiation. Blood agar also supports growth, forming small, grayish, smooth, non-hemolytic colonies. These methods are vital for isolating and identifying the bacterium.
- Loeffler's serum slope: creamy white colonies (6-8 hrs)
- Potassium tellurite medium: black colonies
- Blood agar: small, grayish, smooth, non-hemolytic colonies
What are the key biochemical characteristics of Corynebacterium diphtheriae?
The biochemical profile of Corynebacterium diphtheriae assists in its identification. It ferments glucose and maltose, producing acid. Crucially, it does not ferment lactose, sucrose, or mannitol. Additionally, C. diphtheriae is urease negative, lacking the urease enzyme. These specific reactions are fundamental for accurate laboratory confirmation and distinguishing it from similar bacterial species.
- Ferments glucose and maltose (acid production)
- Does not ferment lactose, sucrose, mannitol
- Urease negative
How is Diphtheria transmitted between individuals?
Diphtheria primarily spreads through respiratory or skin transmission, emphasizing the risk of close contact. Transmission occurs via direct contact with an infected person or through aerosolized secretions, such as droplets from coughing or sneezing. Humans are the sole known reservoir for Corynebacterium diphtheriae. This human-to-human spread highlights the importance of public health measures.
- Respiratory or skin transmission
- Direct contact or aerosolized secretions
- Humans are the only reservoir
What is the role and nature of the Diphtheria Toxin?
The Diphtheria Toxin, a potent exotoxin, causes the disease's severe systemic effects by inhibiting protein synthesis in host cells. This single polypeptide chain has two subunits: A, which prevents protein synthesis, and B, which facilitates cell entry. Toxin production occurs only when the bacterium is infected with a specific bacteriophage, a key factor in its virulence.
- Exotoxin; inhibits protein synthesis
- Single polypeptide chain (A and B subunits)
- Produced only when infected with a bacteriophage
- Clinical Classifications:
- Malignant (Hypertoxic): Severe toxemia, adenitis, lymph gland swelling; leads to death, circulatory failure, paralytic sequelae.
- Septic: Ulceration with pseudomembrane formation and cellulitis.
- Hemorrhagic: Local and general bleeding from pseudomembrane edge, conjunctival, epistaxis, purpura.
What are the common clinical manifestations of Diphtheria?
Diphtheria presents with varied clinical signs, mainly affecting the upper respiratory tract. Initial symptoms include sore throat and low fever. A defining feature is the thick, gray pseudomembrane on tonsils, pharynx, or nose, potentially causing airway obstruction. Beyond local effects, the toxin can induce systemic complications like myocarditis (arrhythmia) and polyneuropathy (palatine paralysis).
- Sore throat, low fever, pseudomembrane
- Myocarditis, arrhythmia
- Polyneuropathy, palatine paralysis
- Complications: asphyxia, circulatory failure, kidney failure, septic sequelae
How is Diphtheria diagnosed?
Diagnosing Diphtheria combines clinical assessment with laboratory confirmation for timely treatment. Clinical suspicion arises from upper respiratory illness, sore throat, low-grade fever, and the characteristic pseudomembrane. Laboratory diagnosis involves throat swabs for Gram and Albert's stains, followed by culture on Loeffler's and Potassium Tellurite media. Biochemical tests and virulence testing confirm toxin-producing C. diphtheriae.
- Laboratory Criteria: C. diphtheriae isolation
- Clinical Criteria: Upper respiratory illness, sore throat, low-grade fever, pseudomembrane
- Laboratory Diagnosis: Throat swab, Gram/Albert's stain, Culture, Biochemical tests, Virulence test
How is Diphtheria treated?
Diphtheria treatment requires immediate, aggressive intervention to neutralize the toxin and eliminate bacteria. Diphtheria antitoxin is crucial, administered based on clinical diagnosis to counteract circulating toxin. Concurrently, antibiotics like Erythromycin or Procaine penicillin G eradicate Corynebacterium diphtheriae, preventing further toxin production and reducing transmission. In severe airway obstruction cases, intubation or tracheotomy may be necessary.
- Diphtheria antitoxin (clinical diagnosis)
- Antibiotics: Erythromycin, Procaine penicillin G, Rifampin, Clindamycin
- Intubation or tracheotomy (if needed)
How can Diphtheria be prevented?
Diphtheria prevention primarily relies on widespread vaccination, targeting the diphtheria toxin. The DTP (DPT) vaccine provides immunity against diphtheria toxoid, tetanus toxoid, and pertussis. For adults, the Td toxoid is recommended for booster immunizations. Immunization schedules include primary vaccination for infants and children, followed by adult boosters. These efforts are vital for controlling diphtheria spread.
- DTP (DPT) vaccine (diphtheria toxoid, tetanus toxoid, pertussis)
- Td toxoid (for adults)
- Immunization Schedule: Primary (infants/children), Booster (adults)
Frequently Asked Questions
What causes Diphtheria?
Diphtheria is caused by the bacterium Corynebacterium diphtheriae. This Gram-positive bacillus produces a potent exotoxin responsible for the disease's severe symptoms and complications.
How does Diphtheria spread?
Diphtheria primarily spreads through respiratory or skin transmission. It occurs via direct contact with an infected person or through aerosolized secretions. Humans are the only known reservoir.
What are the main symptoms of Diphtheria?
Key symptoms include sore throat, low-grade fever, and a thick, gray pseudomembrane in the throat or nose. Complications can involve heart damage, nerve issues, and airway obstruction.
How is Diphtheria treated?
Treatment involves immediate Diphtheria antitoxin to neutralize the toxin, plus antibiotics like Erythromycin to eliminate the bacteria. Intubation may be necessary for severe airway obstruction.
Can Diphtheria be prevented?
Yes, Diphtheria is preventable through vaccination. The DTP (DPT) vaccine is given to children, and the Td toxoid is used for adult boosters, targeting the diphtheria toxin for immunity.
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