Community-acquired infections

Question 1

66 year old type II diabetic on gliclazide: 2-day history of rigors and fever, Increasing heat, swelling and pain in right foot, Loss of function

• O/E: T 40ºC, BP 90/50, Slightly confused
  a) Diagnosis? - likely pathogen? - what more severe DDx is there?
  b) Investigations?
  c) Management?

Answer 1

a) Cellulitis: most likely strep pyogenes, then staph,
- more severe DDx: NECROTISING FASCIITIS

b) Bloods (FBC, U+E, Glucose/HBA1C, CRP), Blood cultures (pre-antibiotics), Swab of pus if present (pre-antibiotics), XR foot – osteomyelitis/foreign body

c) - IV fluids (hypotensive)
- IV ABx (fluclox to cover staph AND benpen for strep),
- Elevation of foot (demarcate borders)

Question 2

Clinical features that may indicate necrotising fasciitis

Answer 2

Pain ++ (out of proportion to cutaneous signs)
Sepsis/shock (out of proportion to visible signs)
Blisters/bullae
Rapid progression of lesion
Oedema
Gas in soft tissues

Question 3

Management of necrotising fasciitis

Answer 3

• ABC
• Urgent surgical opinion for debridement
• Antibiotics (anti-toxin activity)
• ?Intravenous immunoglobulin
• Critical Care assessment

Question 4

Appropriate antibiotics for strep pyogenes

a) Oral first line
b) If penicillin allergic
c) IV (for more severe)
d) In pregnancy

Answer 4

a) Amoxicillin/ampicillin
b) Erythromicin
c) Benzylpenicillin (penicillin G)
d) Erythromycin

Question 5

Appropriate antibiotics for staph aureus

a) Oral first line
b) If penicillin allergic
c) MRSA
d) In pregnancy

Answer 5

a) Flucloxacillin
b) Clindamycin
c) Vancomycin
d) Erythromycin

Question 6

72 year old woman:
Referred to MAU with 5 days of fever and chills, Lethargy and malaise 4 weeks, Weight loss and reduced appetite.
6-months previously: tissue aortic-valve replacement for degenerative disease
- O/E: HR 90, BP 110/60, T 39ºC, ESM 3/6 and EDM 2/6
a) Diagnosis?
b) What other clinical features might confirm this?
c) Investigations?
d) Management?

Answer 6

a) Bacterial endocarditis
b) Splinter haemorrhages, Roth spots, Janeway lesions, Olser’s nodes

c) - Bedside: ECG
- Bloods: cultures (3 separate sites, 3 separate times),
- FBC and full clotting screen, U+Es, ESR, CRP
- Imaging: CXR, echocardiogram (TOE)

d) - IV ABx (choice dependent on severity, whether native valve or prosthetic valve and results of culture)

Question 7

Predisposing factors for infective endocarditis

Answer 7

Susceptible valve:

• Pre-existing valvular lesion (bicuspid aortic, other acquired valve lesions, RHD)
• Prosthetic valve (tissue + metal)

Causes of Bacteraemia

• IVDU
• Dental infection/intervention
• Long-term haemodialysis/central access
• Invasive procedures (esp. urological)

Question 8

Causes of infective endocarditis

a) Gram neg or gram positive mainly?
b) Native valve causes
c) Prosthetic
d) Non-bacterial

Answer 8

a) Usually gram-positive bacteria.

b) Native valve endocarditis:
- Staph aureus (and more rarely MRSA)
- Strep viridans, Strep. pyogenes
- Enterococcus spp. (esp. urological issues/intervention)

c) Prosthetic valve endocarditis:
- Coagulase negative staphylococci (e.g. Staph. epidermidis)

d) - ‘Culture-negative endocarditis’: HACEK, coxiella, chlamydia, legionella
- Other: Fungal endocarditis (esp. IDU)
- Non-infective (malignancy, autoimmune)

Question 9

Microbiology:

a) Catalase positive, coagulase positive = ?
b) Catalase positive, coagulase negative = ?
c) Catalase negative, beta-haemolytic = ?
d) Catalase negative, alpha-haemolytic = ? (2)

Answer 9

a) S. aureus
b) coag-negative staph
c) s. pyogenes (GABS)
d) s. pneumoniae and strep viridans

Question 10

Antibiotic choice:

a) Gram positive cocci (3 classes)
b) Gram negative rods (4 classes)
c) Gram negative diplococci (neisseria)

Answer 10

a) PENICILLINS (Flucloxacillin, penicillin)
MACROLIDES (clarithro/azithro/erythromycin)
GLYCOPEPTIDES (vancomycin/teicoplanin)
- Also clindamycin (a lincosamide)

b) - CEPHALOSPORINS
- PENICILLINS with ANTI-β LACTAMASE (co-amoxiclav, tazocin),
- AMINOGLYCOSIDES (gentamicin, tobramycin, neomycin)
- CARBAPENEMS (meropenem)

c) Benzylpenicillin, cefotaxime, ciprofloxacin, rifampicin

Question 11

Diagnosing IE:

a) Criteria
b) Major
c) Minor

Answer 11

a) Dukes (modified)
b) 2 separate +ve blood cultures with relevant organisms, Evidence of endomyocardial involvement (Echo or new regurgitant murmur), +ve Coxiella serology
c) T>38ºC, Vascular phenomena (e.g. emboli), Immunological phenomena (Osler’s, GN, Roth’s, RF), +ve microbiology not fulfilling major criteria, Echo findings not fulfilling major criteria

Question 12

Blood cultures growing staphylococcal-like bacteria would usually be tested against which of the following antibiotics:

a) Methicillin (flucloxacillin)
b) Gentamicin
c) Vancomycin/teicoplanin
d) Metronidazole
e) Erythromycin

Answer 12

a) Methicillin (flucloxacillin)
c) Vancomycin/teicoplanin

i. e. to test for:
- Normal staph aureus
- MRSA
- VRSA

Question 13

Blood cultures growing gram-negative rods (coliform-like) would usually be tested against which of the following antibiotics?

a) Gentamicin
b) Amoxicillin
c) Co-amoxiclav
d) Erythromycin
e) Vancomycin

Answer 13

a) Gentamicin
b) Amoxicillin
c) Co-amoxiclav

Question 14

23 year old woman:
Referred to MAU with 12-hours fever, chills and loin pain, 3 days of dysuria and frequency, Similar urinary symptoms over last few months: treated with 3-days of cefalexin by GP, in a stable relationship, on OCP
- O/E: Unwell and agitated, T 39ºC, BP 90/50
Renal angle tenderness on right
- Urine dip: Cloudy urine, Leucocytes ++, Nitrites +++, Blood +
a) Diagnosis
b) Ix?
c) Rx?
d) If patient doesn’t respond - why?
e) Next steps to take

Answer 14

a) Probable UTI + acute pyelonephritis
b) Send urine for MC and S, Bloods (FBC, U and E, CRP), Blood cultures
c) IV fluids, analgesia, IV Antibiotics (cefuroxime, or co-amoxiclav)
d) Extended-spectrum β-lactamase producers (ESBL)

e) - USS kidneys
- await MC and S,
- trial other antibiotics (e.g. ciprofloxacin, gentamicin - beware gentamicin if kidney damage)

Question 15

UTI management.

a) Investigating suspected UTI
b) ABx choice
c) ABx in pregnancy
d) ABx choice if systemically unwell

Answer 15

a) Urine dip (good for excluding infection; no use in catheterised patients) +/- MSU
- Women - pregnancy test (determines ABx choice)

b) Trimethoprim, nitrofurantoin (only for lower UTI - needs to be concentrated in kidney to have therapeutic effect), amoxicillin (3/7 course)

c) Β-lactam (cell-wall) antibiotics generally safe,
Avoid trimethoprim in 1st trimester, avoid nitrofurantoin in 3rd trimester

d) Co-amoxiclav (beware risks - c.diff, ABx resistance)

Question 16

60 year old lady:
Normally fit and well, 2 day history of ear ache, 24 hour history of fever and headache, becoming increasingly confused.
- O/E: GCS 10/15, T 39ºC, HR 120 bpm regular, BP 100/60mmHg, No rash, Neck stiffness, Photophobia
a) DDx?
b) Initial Ix?
c) Rx?
d) Further Ix?
e) Further Rx? (if bacterial)

Answer 16

a) Meningoencephalitis
b) FBC, U+Es, LFTs, Clotting, Blood cultures, Meningococcal and Pneumococcal PCR
c) ABC, IV access and fluid resuscitation, IV ABx (ceph +/- amoxicillin for listeria), IV dexamethasone, +/- IV aciclovir
d) CT head, LP (if no CIs)
e) Chemoprophylaxis close contacts, notify PHE

Question 17

25 year old man:
Presents to GP with fever, cough with thick yellow sputum.
- O/E: unwell, sweating profusely, RR 25, T 39.5
BP 105/60, HR 100
Dullness and patchy areas of bronchial breathing mid-zone of the right lung field
a) DDx?
b) Assessment of severity?
c) Initial Rx?
d) Initial Ix?

Answer 17

a) CAP (if rust-coloured sputum: pneumococcus)
b) CURB 65 (Confusion, Urea > 7, RR > 30, SBP < 90, age> 65)

1 = mild, 2-3 = moderate, 4+ severe

c) Amoxicillin, macrolide or co-amoxiclav
d) Bloods (FBC, CRP, U and Es), blood cultures, sputum culture, CXR