Infection X - Pathogens + Diseases (Part 2)

Question 1

What type of organism is clostridium difficile?
Why do C.difficle infections arise?
What are its virulence factors?
Why is it so difficult to get rid of?

Answer 1

• Gram positive bacilli (anaerobic)
• Suppression of normal intestinal flora by antibiotics (cephalosporins + fluoroquinolones) allows C.difficile to become dominant and colonise large intestine
• Toxin A (enterotoxin) causes excessive fluid secretion, + stimulates inflammatory response. Toxin B (cytotoxin) disrupts protein synthesis and damages cell structure
• Spore-forming bacillus with spores resistant to heat, acid, antibiotics and survive for months.

Question 2

What are the clinical symptoms of a C.difficle infection?
How is it treated?
What kind of patient profile indicated C.diff infection?

Answer 2

• Diarrhoea, vomiting, abdominal pain, fever, severe infection can cause bowel perforation.
• Cannot kill with alcohol, use soap. Metronidazole for mild, vancomycin for severe.
• Diarrhoea with antibiotic use within past 3 months, or diarrhoea after 48 hours of hospitalisation

Question 3

What type of organism is norovirus?
What does infection cause?
How is it transmitted?
How is it treated?

Answer 3

• Single stranded RNA, non-enveloped virus
• Winter vomiting bug - typical symptoms
• Faecal-oral route
• No specific treatments - supportive only (anti-pyretic, IV fluid)

Question 4

Whats is the causative agent of Covid-19?
What type of organism is it?
How is the virus transmitted?
What are the barriers to its entry?

Answer 4

• Sars-CoV-2 - ssRNA (+) enveloped virus
• Via respiratory route (small droplets, large droplets or larger ones on surfaces onto mucous membranes)

1) Respiratory epithelial cells covered in mucus 2) Ciliated respiratory epithelium 3) IgA, natural killers and macrophages in lung.

Question 5

How does Sars-Cov-2 cause infection?

What are the symptoms?

Answer 5

• Binds to ACE2 receptors, entry via receptor-mediated endocytosis.
• RdRp converts positive sense into negative sense ssRNA
• Acts as messenger RNA for manufacture of viral proteins and assembly into nucleocapsid.
• Loss of taste/smell
• Extreme fatigue
• Dry cough
• Fever/headaches

Question 6

What kind of organism is staphyloccocus epidermis?
What kind of infections does it cause?
Is it coagulase positive or negative?

Answer 6

• A gram positive cocci (grape-like)
• Prosthetic device (e.g.: heart valve) and surgical wound infections
• Coagulase negative (S.aureus is coagulase positive)

Question 7

What is endocarditis?
What are the causative organisms?
How do individuals with prosthetic heart valves develop endocarditis?

Answer 7

• Inflammation of the endocardium
• Staphylococcus epidermis, Streptococcus mutans etc.
• Bacterial adherence to device during surgery, biofilm growth and persistent inflammation.

Question 8

What are the clinical features of endocarditis?
How is it diagnosed?
How is it treated?

Answer 8

• Fever, heart murmur, other cardiac complications, e.g.: embolism.
• Blood cultures + Tissue cultures
• Antibacterials, remove prosthetic valve

Question 9

What is febrile neutropenia/neutropenic sepsis?

What is the treatment?

Answer 9

• High temperature (over 38.3*C) + neutrophil count <500/mL

- Sepsis 6 bundle - empiric broad spec AB’s (IV Tazocin)

Question 10

What type of organism is the EBV?
What disease does the EBV cause?
How is it transmitted?

Answer 10

• Single stranded RNA, non-enveloped virus
• Glandular fever (infectious mononucleosis)
• Gets into mouth by saliva, infects B+T cells in tonsils, causing spread to other lymphoid tissue, immune system responds.

Question 11

What are the symptoms of glandular fever?

How is it treated?

Answer 11

• Fever, pharyngitis, lymphadenopathy, splenomegaly, fatigue, atypical lymphocytosis
• Non - no antivirals.