Gram-positive bacilli Flashcards
Where do you find Listeria?
Listeria monocytogenes which lives in soil.
Found in pâté, raw vegetables/salad, unpasteurized milk/cheese
What is the presentation of Listeria?
- Most asymptomatic, or mild flu-like illness
- In immunosuppressed (including elderly): gastroenteritis, local infection (abscess, osteomyelitis, septic arthritis, endocarditis, pneumonia), meningoencephalitis, life-threatening septicaemia
- Listeria in pregnancy may cause mild disease in mother but can cause transplacental infection
How do you diagnose Listeria?
- Culture (blood, placenta, amniotic fluid, csf)
- PCR
How do you treat Listeria?
Ampicillin plus gentamicin (synergistic action) for systemic disease
Co-trimoxazole (CNS disease), macrolides, tetracycline, rifampicin, vancomycin, carbopenem.
NOTE: Resistant to cephalosporins which often 1st-line empirical for meningitis so additional antimicrobial cover if listeria is a possibility.
What are the different types of clostridria?
- Clostridium difficile
- Clostridium perfingens
- C. botulinum
- C. tetani
What does C.diff cause?
- Pseudomembranous colitis, typically seen after the use of broad-spectrum antibiotics
- Produces both an exotoxin and a cytotoxin
What does C.perfingens cause?
- Gastroenteritis
- Gas gangrene
due to alpha-exotoxin production which causes gas gangrene(myonecrosis) and haemolysis
Presentation: sudden, severe pain due to myonecrosis, oedematous skin with haemorrhagic blebs and bullae, tissue crepitus, systemic shock.
Most post-surgery (GI, biliary), or following soft-tissue trauma/open fracture. If spontaneous, look for malignancy
Treatment: early recognition, surgical debridement, protein synthesis inhibitors, eg clindamycin inhibit toxins > penicillins
What does C.botulinum cause?
Seen in canned foods and honey
Prevents acetylcholine (ACh) release leading to flaccid paralysis
What does C.tetani cause?
Produces an exotoxin (tetanospasmin) that prevents the release of glycine from Renshaw cells in the spinal cord causing a spastic paralysis
What does diptheria cause?
Caused by Corynebacterium diphtheriae that releases an exotoxin by a β-prophage that inhibits protein synthesis by catalysing ADP-ribosylation of elongation factor EF-2
What are the presenting features of diptheria?
- Recent visitors to Eastern Europe/Russia/Asia
- sore throat with a ‘diphtheric membrane’ on tonsils caused by necrotic mucosal cells
- fever, painful dysphagia
- bulky cervical lymphadenopathy
- neuritis e.g. cranial nerves
- heart block
How do you diagnose diptheria?
culture, toxin detection, PCR
What is the treatment of diptheria?
- Treatment: antitoxin within 48h. Benzyl-penicillin/erythromycin. Airway support
- Preventable with vaccine
What does actinomycosis cause?
Due to Actinomyces israelii, a mucous membrane commensal.
Presentation: Subacute granulomatous/suppurative infection adjacent to mucous membrane.
Diagnosis: Culture. ‘Sulphur’ granules in pus/tissue are pathognomonic.
Treatment: Abx covering actinomycetes and concomitant microbes
What does nocardia cause?
Rare cause of disease.
Presentation: tropical skin abscess, lung/brain abscess, disseminated infection if immunosuppressed.
Treatment: usually co-trimoxazole
