Bacterial Infections

Question 1

Antibiotics for perichondritis:

Answer 1

Pseudomonas aeruginosa
–> *Ciprofloxacin

I&D if fluctuant (ENT)

Don’t miss- deformity

Question 2

ESCAPPM organisms, and significance:

Answer 2

Enterobacter
Serratia
Citerobacter
Aeromonas, Acetinobater
Proteus (not mirabelis)
Pseudomonas, providencia
Morganella

Induceable beta-lactamase
ie. Resistant to most cephalosporins, penicillins and even B-lactamase inhibitors like Augmentin

Treat with:
Carbapenam, or
aminoglycoside

Question 3

Acute Rheumatic Fever

Answer 3

Sequelae 3 weeks after a Group A strep pharyngitis
–> 30% subclinical initial infection
School-age children
ATSI, developing

CLINICAL
- Jones Criteria

IX
- Throat swab for GAS -often negative
- Antistreptolysin (ASO) + AntiDNaseB titres
- ECG: ?AV block

MX
- Penicillin
—> Single dose IM Pen G
or
—> 10 days PO Phenoxy (penV)
…….then years of prophylaxis
- ECHO
- High-dose aspirin 100mg/kg/day for joints
- Notifiable

Question 4

Jones Criteria in acute rheumatic fever:

Answer 4

Diagnosis:
- History of recent Strep A infection
plus
- 2 major
or
- 1 major + 2 minor

_______________

MAJOR- ’SPECC’
- polyarthritis, or polyarthralgia
- Carditis (AR/MR murmur or on echo)
- Subcut nodules (rare)
- Erythema marginatum (rare)
- Chorea

MINOR
- Prolonged PR
- Fever
- ESR, CRP, Leuks
- Monoarthralgia

Question 5

Most common manifestation in Rheumatic Heart Disease?

Answer 5

Mitral REGURGITATION (or stenosis)
–> Emboli
–> IE
–> CCF
AV block
Pericarditis
Myocarditis

Question 6

What is the false + rate for blood cultures:

Answer 6

50%!

Also only 10% yield.

Question 7

Ways to minimise spurious blood culture results:

Answer 7

• 2 sets, from 2 sites
• Before antibiotics
• Only from aseptic sites or newly inserted line
• If line sepsis, take from line
• Sterile technique
• Don’t under or overfill bottle (9ml adult)
• Fill BC bottles before other tubes
• Use appropriate specialised bottle (eg. fungal, HACEK)

Question 8

What things suggest a contaminated/ false + blood culture sample:

Answer 8

Polymicrobial
COAG NEG STAPH
BACILLUS
DIPTHEROIDS
–> Skin flora.

Not all bottles positive
Slow to grow

Question 9

Which organisms almost never represent contaminants?

Answer 9

S. aureus
S. pneumoniae
S. pyogenes (GAS)
Pseudomonas

Question 10

What are the main marine pathogens. Where are they acquired, and how are they treated?

Answer 10

AEROMONAS:
- Fresh or brackish
- Unremarkable cellulitis
–> CIPROFLOXACIN 500mg BD

VIBRIO:
(Vulfunicans)
- Salt or brackish
- Nasty + necrotising wounds
(Parahaemolyticus)
- Dysentary from undercooked shellfish
–> DOXYCYCLINE plus CEFTRIAXONE

MYCOBACTERIUM:
- Fish tanks
- “Fishtank granuloma”
- DOXYCYCLINE

Question 11

TB: Natural course

Answer 11

PRIMARY TB usually causes an unremarkable pneumonia anywhere in lung.

It can spread systemically to cause:
- Miliary/ disseminated
- Extrapulmonary (tuberculomas, meningitis, cutaneous, lymphadenitis, pericarditis, spinal (Potts) etc.)

TB pneumonia gets ‘walled off’ into a Gohn focus (granuloma). It is now either cured or dormant (latent).

Latent either stays this way, or reactivates as SECONDARY TB. Typically upper zone cavitating pneumonia
________

Only active, pulmonary TB is infectious (airborne)
Latent + extrapulmonary TB is not.

Question 12

TB: Diagnosis of active TB

Answer 12

Sputum, for:
- Culture (takes 3 weeks!!)
- Gram stain
–> Acid-fast bacillus, Zeihl-Neillson
- PCR

Question 13

TB: Management

Answer 13

Airborne precautions

‘RIPE’
- Rifampicin
- Isoniazid
- Pyrozinamide
- Ethambutol
….+ pyridoxine (neuropathy)

For 6 months.

Contact PEP

Question 14

CXR in TB:

Answer 14

Primary TB:
- Non-specific pneumonia + lymphadenopathy
- May get calcified lymph nodes
- Or, miliary

Gohn Focus:
- 1-2cm
- Subpleural
- Mid zone

Secondary TB:
- Upper/ hilar and cavitating

Question 15

Gas Gangrene

Answer 15

Clostridium (perfringens)
Soil-borne anaerobe

Rapidly progressive MUSCLE necrosis
Gas filled blisters, crepitus
Foul smelling+++

100% fatal without treatment.

• Antis (Ceftriaxone + Gent + Metro)
• HBO
• Debridement/ amputation

Question 16

Necrotising Fasciitis: Common organisms

Answer 16

S.aureus (MSSA, MRSA)
Strep pyogenes (GAS)
Vibrio (vulcanifans)
Clostridium (gas gangrene)

Polymicrobial (diabetes)
Candida (immunosuppression)

Question 17

Necrotising Fasciitis: CT and Examination

Answer 17

Pain out of proportion
Rapidly progressive
Oedema beyond margin of erythema
Firm
Crepitus (gas gangrene)
Toxic

Oedema
Collection
Fat stranding
Gas in fascial planes

Question 18

Necrotising Fasciitis: Treatment

Answer 18

MEROPENAM
+ VANCOMYCIN
+ CLINDAMYCIN

Hyperbaric O2

Question 19

Necrotising skin infections: General

Answer 19

Nec fasc: Subcut
Gas gangrene: Muscle
Fourniere is a polymicrobial nec fasc of perineum

• Meropenam + Vanc + Clinda
• Debride/ amputate
• Hyperbaric O2