Microbiology 8 - Infection CPC

Question 1

How does PCP pneumonia appear on CT chest?

Answer 1

Widespread, bilateral ground glass shadowing with ↓ exercise tolerance and ↓ sats

Question 2

PCP ‘typical picture’

Answer 2

CXR fairly normal, CT ground-glass, SoBOE (SpO2 tends to drop on exertion more)

Question 3

Which stain can be used to detect PCP ?

Answer 3

methenamine silver stain (Grocott-Gomori) -> cysts

Question 4

How should PCP pneumonia be treated?

Answer 4

1. co-trimoxazole 960mg BD
2. Clindamycin and Primiquine (G6PD norm), IV methylprednisolone

Question 5

Which type of bacteria are people with a B cell immunological defect most susceptible to?

Answer 5

Strep
Staph
Haemophilus

Question 6

Which type of bacteria are people with a neutrophil immunological defect most susceptible to?

Answer 6

Staph
Pseudomonas

Question 7

Which type of bacteria are people with a complement defect most susceptible to?

Answer 7

Neisseria

Question 8

Which type of virus are people with a B cell immunological defect most susceptible to?

Answer 8

Enteroviral encephalitis

Question 9

Which type of viruses are people with a T cell immunological defect most susceptible to?

Answer 9

CMV
EBV
Varicella

Question 10

Which type of fungal infections are people with a T cell immunological defect most susceptible to?

Answer 10

PCP
Candidia

Question 11

Which type of fungal infections are people with a neutrophil immunological defect most susceptible to?

Answer 11

Candida
Aspergillus

Question 12

What infection are alcoholics more susceptible to than the general population and why?

Answer 12

Alcohol also immunosuppresses - Actinomyces Lung Abscess

Gram-positive rod that branches

Question 13

What phrase is pathognemonic for actinomyces abscesses?

Answer 13

Basiphilogranules (sulphur granules)

Question 14

Why are antibiotics not useful in osteomyelitis?

Answer 14

cannot sterilise dead bone or cavities with necrotic content and rigid walls

Fibrous capsules can form which makes it impenetrable to ABx and it becomes a chronic source of infection

Question 15

What is the most important part of treating prosthetic joint infection?

Answer 15

Removal of prosthesis and adequate debridement is the MOST IMPORTANT part of treatment

Antibiotics = secondary role

Question 16

What are the risk factors for C diff infection?

Answer 16

Administration of antibiotics (clindamycin, cephalosporin, ciprofloxacin)

65+ years

Duration of hospital stay

Severe underlying diseases

precipitated by cytotoxic drugs, antacids/PPIs, non-surgical GI procedures (e.g. NG tubes)

Question 17

Why do PPIs increase the risk of C diff?

Answer 17

NOTE: PPIs ↑ stomach pH → ↑ GI flora and C. difficile spores can survive the stomach and travel down to the colon

Disease may occur during a course of antibiotics or in the weeks after completing a course of antibiotics

Question 18

What is the treatment for C diff?

Answer 18

Non-severe - metronidazole 400mg PO TDS 10-14 days

intolerant/not responding at 72 hours (and no other indicators of severity) → vancomycin 125mg PO QDS 10-14 days

Severe + colonic dilatation -> vancomycin 125-250mg PO QDS + metronidazole 500mg IV TDS 14 days + liaise with ID and gastroenterologist surgeons

severe + ileus/vomiting -> consider intracolonic vancomycin + liaise with ID and gastroenterologist surgeons

Question 19

What do the toxins attack in C diff?

Answer 19

One damages epithelial cells (cytotoxin) → neutrophil infiltration of tissues

other disrupts tight junctions → loss of fluid within bowels

Question 20

How are the WCC and CRP in C diff?

Answer 20

high WCC + low CRP is common in C. difficile infection