Microbiology: Corynebacterium and Listeria

Corynebacterium

• Includes C. diphtheria, the cause of diphtheria, and Diphtheriodes (normal flora).
• Diphtheria is rare in developed countries due to widespread vaccination.
• Transmission through respiratory droplets, direct contact, and contaminated waste.
• Pathogenesis involves a toxin that inhibits protein synthesis.
• The toxin consists of two fragments (A and B).
• Fragment B binds to cell receptors, then fragment A is delivered to inhibit protein synthesis.
• C. diphtheriae is found in the throat and nasopharynx of carriers and patients.
• Diphtheria is a local infection.
• Symptoms can include a thick, grayish exudate (pseudomembrane) in the throat, nasal passage swelling, and potentially heart and nerve damage.

Listeria

• Listeria monocytogenes is the only species that infects humans.
• Listeria is an intracellular parasite.
• Foodborne transmission is common (e.g., ice cream, cheese, ground meats, poultry).
• Infections are common during pregnancy, in newborns, and in immunocompromised individuals.
• Symptoms can include asymptomatic infections but severe cases show meningitis or septicemia.
• Three serotypes exist, one with high mortality rate associated with anpasteurized milk.
• Diagnosis includes Gram-stain, microscopic examination, and culture.
• Listeria has short, rod-shaped cells, are Gram-positive, and can be motile, including tumbling.
• Listeria produces a toxin, Listeriolysin O, to escape phagolysosomes.
• The bacteria multiplies in phagocytes and uses actin to move between cells.
• Treatment options include antibiotics like penicillin, or ampicillin/trimethoprim/sulfamethoxazole.

Propionibacterium

• Propionibacterium acnes is a common skin bacterium.
• It's classified as a Corynebacterium anaerobe diphtheroid.
• It is part of normal skin flora, but can cause acne via an inflammatory response.
• The bacteria produce lipase, which then splits off fatty acids from the skin.
• Symptoms of Propionibacterium are related to its role causing infections, inflammation, and associated with acne.
• Propionibacterium produces propionic acid through carbohydrate fermentation.
• It is Gram-positive, non-spore forming, and anaerobic/microaerophilic.
• Diagnosis generally involves clinical findings and sometimes a skin culture.

Explore the essential characteristics and pathology of Corynebacterium and Listeria. Learn about the diseases caused by these bacteria, their transmission methods, and the impact of vaccination on diphtheria occurrence. This quiz covers key aspects of both microorganisms and their effects on human health.