Bacterial Infection

Question 1

What is a bacteria?

Answer 1

Prokaryotic organism without a membrane bound nucleus

Question 2

What is the difference between gram +ve and -ve bacteria?

Answer 2

=> Gram +ve bacteria:
- Bacteria with an exposed peptidoglycan layer, stain purple

=> Gram -ve bacteria:

• With an extra layer of cells protecting the peptidoglycan layer
• Counter stain pink/red

Question 3

What are the different shapes a bacteria can take?

Answer 3

=> Cocci - round
=> Bacilli - rod shaped
=> Spirochaete - spiral

Question 4

What is the difference between aerobe and anaerobes

Answer 4

Aerboes require oxygen to grow and survive where as anaerobes can survive without oxygen

Question 5

What are some examples of Gram +ve bacteria?

Answer 5

=> Staphylococci
- Some strains are commensal, to determine if strains are virulent look for enzyme coagulase
Coagulase -ve, less virulent = Staph Epidermis
Coagulase +ve, more virulent = Staph Aureus

=> Streptococci

• Divided into alpha and B haemolytic types
• Main alpha haemolytic strep = Strep Pneumoniae
• B haemolytic subtypes = group A, B and D

=> Enterococci
- Cause endocarditis

=> Listeria

• Listeria Monocytogenes
• Lives in soil and some foods
• May be asymptomatic and cause a mild flue like disease
• In immunocompromised, gastroenteritis, life threatening septicemia

=> Clostridia

• Clostridium Perfingrens = foul smelling gas gangrene
• Clostridium Botulinum = Found in canned food and honey. May cause flaccid paralysis
• Clostridium Difficile = produces exotoxin and develops through broad spectrum antibiotic use
• Clostridium Tetani = causes spinal paralysis

=> Diptheria

• Caused by Corynebacterium Diptheriae
• Caused tonsillar pseudomembrane with fever, painful dysphagia, cervical lymphadenopathy

=> Actinomycosis

• Actinomyces Israelii
• Causes subacute granulamatous infection

=> Nocardia

=> Anthrax

Question 6

What are some examples of Gram -ve bacteria?

Answer 6

=> Niesseria

• Niesseria Meningitidis
• Neisseria Gonorrhoea

=> Moraxella Catarrhalis
- Can cause pneumonia, acute exacerbation of COPD

=> Enterobacteriaceace

• E.Coli
• Klebsiella
• Proteus

=> Pseusomonas Aeruginosa
- Can infect wounds and cause non-sociamal infections

=> Haemophilus Influenza

=> Whooping Cough

Question 7

What are some examples of B haemolytic subtypes Streptococci?

Answer 7

=> Group A - Strep Pyogenes

• Colonises throat, skin and anogenital tract
• Can cause tonsilitis, pharyngitis, scarlet fever, impetigo pneumonia

=> Group B - Strep Agalactiae
- Neonatal and peuperal infectoin, skin and soft tissue

Question 8

What is Typhoid?

Answer 8

• Typhoid and Paratyphoid are caused by gram -ve rods Salmonella Typhi and Salmonella Paratyphi
• Transmitted via faecal oral route

=> Clinical features:

• Systemic upset
• Bradycardia
• Abdominal pain, distension
• Constipation
• Rose spots on trunk