Listeriosis and Diphtheria

Question 1

Diagnosis of Listeria Monocytogenes

Answer 1

Gram (+), Rod-shaped, Catalase (+), oxidase(-),facultative anaerobic, no spores

Question 2

Infection route of Listeria Monocytogenes

Answer 2

1) Zoonoses, food contamination ( found in soil,
vegetation, water)
2) perinatal or non-perinatal (foodborne)

Question 3

Risk factors of Listeria Monocytogenes

Answer 3

1) HIV
2) age extremes,
3) pregnancy,
4) solid organ & bone marrow transplant,
5) corticosteroids & antiTNF

Question 4

Pathogenesis of Listeria Monocytogenes

Answer 4

Ingestion–> crosses mucosal barrier –>
bloodstream–> dissemination (spreads)
(predilection: placenta & CNS)

*Avoids phagosomes–> multiplies in cytoplasm

Question 5

Clinical Manifestations of Listeria Monocytogenes

Answer 5

1) Bacteraemia in pregnancy (3rd trimester):
- febrile illness (e.g., respiratory tract infection)
- headache,
- arthralgia (stiff joints)
- stillbirth,
- abortion,
- premature labour
(NB: pregnant women isn’t septic)

2) Neonatal listeriosis:
- granulomatosis infatiseptica,
- early onset sepsis,
- late-onset meningitis

3) CNS:
- meningitis,
- brain abscess,
- rhombencephalitis

4) febrile GI disease:
(self-limited), 1-3 days after ingestion–> fever, watery diarrhoea, vomiting

Question 6

Diagnosis of Corynebacterium Diphtheriae

Answer 6

Gram(+), rod shaped , No spores, black-brown colonies
(tinsdale agar)

Question 7

Infection route of Corynebacterium Diphtheriae

Answer 7

Airborne or direct contact of respiratory
secretions or skin lesion exudate

Question 8

Pathogenesis/VF of Corynebacterium Diphtheriae
+
what are the complicatins associated with the VF?

Answer 8

Εxotoxin (β-phage carrying gene for diphtheria toxin)

Affects:
1) myocardial cells (myocarditis),
2) neurons (demyelination) &
3) kidney cells (tubular necrosis)

Question 9

Clinical Manifestaions of Corynebacterium Diphtheriae

Answer 9

1) Respiratory diphtheria:
–> 2-4d incubation,
Anterior Nasal :
–> serosanguineous/ seropurulent discharge
- faucial:
–> low-grade fever, malaise, sore throat, pharyngeal infection

–> toxin tissue necrosis, grey membrane on tonsils, oropharynx, nasopharynx
–>oedema, stridor, breathing difficulty

2) Cutaneous diphtheria:
- chronic non-healing ulcers with grey
membrane (Bull neck?)

3) Systemic infections:
- cardiac failure, arrhythmias, myocarditis,
paralysis of soft palate & posterior pharynx, cranial & peripheral neuropathies, renal failure

Question 10

Treatment for Corynebacterium Diphtheriae

Answer 10

1) Diphtheria antitoxin (equine) + abx
2) Vaccinate close contacts & prophylactic abx
3) Strict patient isolation until 2 throat cultures
are -ve