Question

Beth begins her internship at a hospital in Los Angeles. She examines a 5 year old child who has been suffering from cold symptoms the past 10 days. Four days ago, the child was seen by a physician and found to have a fever, enlarged cervical lymph nodes, and an exudate on his pharynx. X-rays of his chest were clear. A throat culture was taken and the child was treated with ampicillin. Today the child is lethargic and experiencing respiratory distress. Beth examines the larynx and sees a yellowish, thick membrane. A club-shaped Gram-positive rods are isolated. No spores are visible via endospore staining.

What is the most likely organism infecting this child? Explain your reasoning.

What is the name for the thick, yellowish exudate seen in the child’s throat?

Should Beth attempt to remove the exudate? Why or why not?

What media should be used to culture these organisms in the lab?

How will colonies of this organism appear on this media (morphology)?

How does the toxin produced by this organism work? i.e. what effect does it have on host cells?

What treatment(s) should be administered to the patient? What precautionary actions should be taken to protect others from infection?

Answer 1

What is the most likely organism infecting this child? Explain your reasoning.

Corynebacterium diptheriae, a gram-positive rod infecting the child. It spreads from one person to another person and leads to symptoms of fever, swollen glands, sore throat, exudates.

What is the name for the thick, yellowish exudate seen in the child’s throat?

Medical experts called the thick, yellowish exudate as 'Pseudomembrane'. It consists of dead tissue that covers the larynx.

Should Beth attempt to remove the exudate? Why or why not?

No. the exudate should not be removed. Removal of membrane leads to scraping of capillaries and results in bleeding.

What media should be used to culture these organisms in the lab?

Blood agar, Loffler medium, and selective tellurite medium are used for screening of Cornybacterium diptheriae. Tellurite inhibits the growth of normal flora so it is easy to differentiate the species.

How will colonies of this organism appear on this media (morphology)?

C. diphtheriae clustered together and appeared as black colonies on the media.

How does the toxin produced by this organism work? i.e. what effect does it have on host cells?

Corynebacterium diphtheria produces an exotoxin covered by bacteriophage. It inhibits the synthesis of protein and thereby kills the cells. The dead cells build up as a thick exudate that covers the larynx and throat and leads to difficulty breathing.

What treatment(s) should be administered to the patient? What precautionary actions should be taken to protect others from infection?

Initially, antitoxin should be administered to neutralize the toxins present in the circulating blood. Antibiotics such as penicillin or erythromycin can be administered for this patient. Strict isolation technique to be followed to prevent the spread of infections to others. The booster dose of vaccination can be administered to prevent the recurrence of disease in the future.