17 Questions
What is the main method used for lab diagnosis identification of C. ulcerans and C. diphtheriae?
ELEK's test
Which sugar is positive in Hiss's Serum sugars test for identification?
Glucose
What is the mainstay of treatment for Diphtheria?
Antidiphtheritic serum
Which antibiotic is NOT sensitive for treating carriers of Diphtheria?
Vancomycin
What is the purpose of using Guinea pig inoculation in the ELEK test for Diphtheria diagnosis?
Test organism
What is a general characteristic of Corynebacterium?
Rod-shaped
Which species of Corynebacterium causes sore throat and ulcers?
C. hemolyticum
What are the biotypes of C. diphtheriae that cause Diphtheria?
Gravis, mitis, intermedius
Which species of Corynebacterium is known for systemic infections in immunosuppressed individuals?
C. jeikium
What kind of infection does C. ulcerans typically cause?
Skin infections and wound contamination
What is a distinguishing feature of respiratory diphtheria compared to cutaneous diphtheria?
Can be fatal if untreated
What is the major clinical sign of laryngeal diphtheria that can lead to death?
Presence of a white pseudomembrane over the throat
Which stain is used in the lab diagnosis to stain volutin in Corynebacterium diphtheriae?
Albert's stain (KLB stain)
What selective media is used to differentiate Corynebacterium diphtheriae from other upper respiratory tract flora?
Tindsdale medium
What is the characteristic morphology observed under microscopy for Corynebacterium diphtheriae?
Pleomorphic gram-positive bacilli with Chinese letter arrangement
Which of the following is a major diagnostic criterion for diphtheria infection before the availability of anti-toxin and vaccination?
White pseudomembrane formation in the throat
What differentiates C.diphtheriae from commensal corynebacteria on Hoyle's Tellurite blood agar?
Production of H2S from cystine
Study Notes
General Characteristics of Corynebacterium
- Gram-positive, catalase positive, non-spore-forming, non-motile, rod-shaped bacteria
- Straight or slightly curved shape
- Metachromatic granules are usually present, representing stored phosphate regions
Species of Corynebacterium
- Many species, with most being commensals (diptheroids)
- Human pathogens:
- C. diphtheriae (3 biotypes: gravis, mitis, and intermedius)
- C. hemolyticum (sore throat, ulcers)
- C. jeikium (systemic infections in immunosuppressed, heart valve infections/endocarditis)
- C. ulcerans (pharyngitis, similar to diphtheria)
Diphtheria
- Caused by C. diphtheriae
- Respiratory diphtheria: more serious, fatal if untreated, begins in the upper respiratory tract
- Cutaneous diphtheria: skin infection, wound contaminated with C. diphtheriae, rarely systemic
- Respiratory diphtheria symptoms:
- Throat acute inflammation
- White membrane over the throat
- Can spread down and cause death from asphyxia (Laryngeal diphtheria)
Laboratory Diagnosis
- Specimen: nasopharyngeal swab, wound swab
- Microscopy:
- Gram stain: pleomorphic gram-positive bacilli, gram variable, coryneform (Chinese letter arrangement)
- Special stain: Albert's stain (KLB stain), Malachite Green, and Toludine blue
- Culture:
- Selective media: Hoyle's Tellurite blood agar, Tindale medium
- Characteristic black colonies on blood tellurite agar (C. diphtheriae)
- Gray colonies on Tellurite agar (commensal corynebacteria)
Identification and Virulence Testing
- Biochemical tests:
- Hiss's Serum sugars: glucose and maltose positive, sucrose negative
- Urease positive: C. ulcerans
- Gelatin liquefied: C. ulcerans and C. diphtheriae
- Virulence testing:
- ELEK's test (Ag-Ab test)
- Guinea pig inoculation
Treatment of Diphtheria
- Mainstay of treatment: Antidiphtheritic serum (antitoxin)
- Antibiotics used for:
- Treatment of carriers
- Synergistic with antitoxin for patients
- Sensitive to Erythromycin, Penicillin, and Clindamycin
Test your knowledge on the general characteristics of Corynebacterium, a Gram-positive, catalase positive, non-spore-forming, and non-motile bacteria. Learn about its Metachromatic granules, species diversity, and its association with diseases like Diphtheria.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
