Pathogen/Pathophys
What is the primary virulence factor of Corynebacterium diphtheriae?
Diphtheria toxin, which inhibits protein synthesis by ADP-ribosylating EF-2
What is the gold standard test for confirming diphtheria infection?
Bonus (100): What is the purpose of using Loeffler's medium in the laboratory diagnosis of Corynebacterium diphtheriae?
Culture on tellurite agar (characteristic black colonies!) followed by Elek immunodiffusion test (precipitation lines confirm toxin production).
Loeffler's medium is used to selectively enhance the growth of Corynebacterium diphtheriae while inhibiting other bacteria. It promotes the production of metachromatic granules (polyphosphate inclusions) within the bacteria, which can be visualized with methylene blue staining to help differentiate C. diphtheriae from non-pathogenic Corynebacterium species.
What does a pseudomembrane look like, and how does it behave when scraped?
Bonus (100): Describe the gram stain for C. Diphtheriae.
Grayish-white membrane that bleeds when scraped.
Corynebacterium diphtheriae is gram-positive, pleomorphic, club-shaped rods that appear in a palisade (side by side) arrangement.
What is the role of the diphtheria toxoid vaccine in preventing disease?
Bonus (300): Discuss the indications, contraindications, formulations, immune response, and efficacy of the vaccine.
It induces immunity by generating neutralizing antibodies against the diphtheria toxin.
Why might endotracheal intubation be required in diphtheria patients?
Bonus (200): Define Adventitious sounds and Inspiratory stridor
To manage airway obstruction from pseudomembrane or laryngeal swelling.
Adventitious sounds: Abnormal sounds heard during breathing, like wheezing or crackles, which may indicate airway obstruction or respiratory complications.
Inspiratory stridor: A high-pitched sound heard during inhalation, caused by partial airway blockage, often due to the pseudomembrane.
How does the pseudomembrane in diphtheria form?
Bonus (100 points): Why does the pseudomembrane bleed upon manipulation?
Toxin-induced necrosis of epithelial and immune cells leads to fibrin, dead cells, and bacteria forming the pseudomembrane.
It bleeds because it is firmly adherent to the underlying inflamed tissue
What physical feature can help differentiate diphtheria from bacterial tracheitis or epiglottitis?
Presence of an adherent pseudomembrane that bleeds when scraped.
What does an elevated troponin T, Ck-MB, and NT-pro BNP level indicate in diphtheria patients?
Myocardial damage due to diphtheria toxin-induced myocarditis
Where is diphtheria still endemic?
(List one area besides Haiti, you can be general)
Areas such as Asia, the Middle East, South Pacific, Haiti, and Eastern Europe.
What is the recommended vaccination schedule for diphtheria for children and adults?
Bonus Question(100): What is the difference between consent and assent in medical decision-making for children?
What is the significance of toxigenic strains in diphtheria pathogenesis compared to non-toxic strains?
Bonus (100): What is used to treat each?
Only toxigenic strains harboring the tox gene produce diphtheria toxin, leading to systemic complications. Antitoxin is reserved exclusively for toxin-producing strains that cause systemic toxicity.
Non-toxic strains cause typically cause localized infections such as pharyngitis, cutaneous lesions, or in rare cases, bacteremia or endocarditis. Antibiotics (penicillin or erythromycin) are used to treat the infection and eliminate the carrier state.
How does PCR help in the diagnosis of diphtheria?
Detects the tox gene in Corynebacterium diphtheriae isolates to confirm toxigenicity.
What findings on urinalysis can be linked to diphtheria-related complications?
Bonus (200): What is the significance of "bull neck" in diphtheria?
Proteinuria and evidence of acute tubular necrosis (e.g., hematuria or elevated creatinine) may indicate renal involvement due to systemic absorption of diphtheria toxin.
Bull Neck indicates severe infection with extensive anterior neck swelling due to lymphadenopathy and soft tissue edema from toxin release.
Discuss the role of herd immunity in diphtheria prevention in endemic vs. non-endemic areas.
Herd immunity reduces transmission, protecting unimmunized individuals, but is less effective in endemic areas with high exposure and low vaccination rates
Why is IV methylprednisolone used in cases of presumed myocarditis caused by diphtheria?
Bonus (300): Drug Chart IV methylprednisolone
To reduce inflammation caused by the diphtheria toxin's damage to myocardial tissue, thereby preventing further cardiac complications such as conduction abnormalities or heart failure.
Why might renal and myocardial cells be more susceptible to diphtheria toxin?
Bonus (200 points): What factors affect the severity of systemic diphtheria toxin effects?
These cells have higher densities of receptors for diphtheria toxin, making them more vulnerable to its effects. :(
The extent of pseudomembrane, bacterial load, patient immunity, and time to antitoxin administration affect its severity.
Why might diphtheria and infectious mononucleosis be confused clinically?
Both can present with fever, sore throat, lymphadenopathy, and pharyngitis; however, EBV involves posterior cervical lymphadenopathy and atypical lymphocytosis.
What is the Elek test, and how does its procedure confirm the diagnosis of toxigenic Corynebacterium diphtheriae?
The Elek test is an immunodiffusion assay used to confirm whether Corynebacterium diphtheriae isolated from a culture produces diphtheria toxin.
In the procedure, a strip of filter paper soaked with diphtheria antitoxin is placed on a culture plate inoculated with the bacteria. If the bacteria produce toxin, antigen-antibody precipitation lines form within 16–48 hours, confirming toxigenicity.
What public health protocols must be implemented for a suspected case of respiratory diphtheria, and why is rapid notification to health authorities critical?
Suspected respiratory diphtheria cases must be immediately reported to local and state health authorities to ensure proper isolation, contact tracing, and initiation of chemoprophylaxis for close contacts.
Notification is critical to prevent outbreaks, especially in unvaccinated or underimmunized populations. Strict droplet precautions should be implemented for the patient until two consecutive negative cultures confirm eradication of the pathogen. Authorities assist in providing the diphtheria antitoxin, monitoring carriers, and coordinating vaccination campaigns in affected communities.
What is the rationale for hypersensitivity testing before administering diphtheria antitoxin?
Bonus (300): Drug Chart Diphtheria Antitoxin
To avoid anaphylaxis in patients with a prior sensitivity to horse serum, as the antitoxin is derived from equine sources.
Discuss the pathophysiologic mechanism of diphtheria toxin in myocarditis development.
Diphtheria toxin inhibits protein synthesis in myocardial cells, leading to necrosis, inflammation, conduction defects, and potential heart failure.
Discuss why identifying toxigenic vs. nontoxigenic strains of Corynebacterium diphtheriae is crucial.
Toxigenic strains cause systemic complications like myocarditis and neuropathy, while nontoxigenic strains may cause localized infections or endocarditis.
How do imaging AND ECG findings in Corynebacterium diphtheriae infection correlate with the pathophysiology of the disease, and what do these findings indicate about disease progression?
Imaging, such as chest X-rays or SPECT, can show complications like airway obstruction, soft tissue swelling, or pseudomembrane extension, correlating with toxin-mediated local damage. ECG findings, such as conduction abnormalities or arrhythmias, reflect myocarditis caused by diphtheria toxin's inhibition of protein synthesis in myocardial cells, leading to cell death and cardiac dysfunction.
These findings highlight systemic toxin effects and the need for close monitoring for life-threatening complications.
Describe the stages of Corynebacterium diphtheriae infection and explain how each stage contributes to its epidemiology.
Discuss the rationale behind chemoprophylaxis with erythromycin for close contacts of diphtheria patients.
To eliminate carriage of Corynebacterium diphtheriae, reducing transmission risk and preventing secondary cases.