Staph. Aureus Bacteraemias

Question 1

how are staphylococci described?

Answer 1

Staphylococci are Gram-positive cocci that form grape-like clusters on Gram stain.

Question 2

in what individuals is the rate of colonisation higher?

Answer 2

The rate of colonisation is higher among patients with insulin-dependent diabetes, HIV infection, patients undergoing haemodialysis, and individuals with skin damage.

Question 3

what is the most frequent site of colonisation?

Answer 3

Anterior nares are the most frequent site of colonisation.

Skin (especially when damaged), vagina, axilla, perineum, and oropharynx may also be colonised.

These colonisation sites serve as a reservoir for future infections.

Question 4

Persons colonised with S. aureus are at greater risk of subsequent infection than _______?

Answer 4

uncolonised individuals

Question 5

how are S.aureus blood stream infections classified traditionally?

Answer 5

healthcare associated

community acquired

Question 6

what is the spectrum of possible infection?

Answer 6

Skin & Soft Tissue Infections- S. aureus is the most commonly identified agent.

Localised pyogenic staphylococcal infections- furuncles and carbuncles.

Deep-seated abscesses, necrotising fasciitis, pyomyositis

Osteomyelitis, Septic arthritis, Discitis

Infective endocarditis

Pneumonia, Empyema

In the hospital setting- wound infection and vascular line- or catheter-related infection

Question 7

Approximately one-third of patients with S.aureus
bacteraemia develop______?

Answer 7

local complications or distant
septic metastases.

Question 8

what are frequent sites of distant metastasis?

Answer 8

Bones and joints (especially when prosthetic materials are present)

Epidural space and intervertebral discs

Native and prosthetic cardiac valves, Cardiac devices

Visceral abscesses in spleen, kidneys and lungs

Question 9

what investigations are done for staph.aureus?

Answer 9

Microscopy and culture of specimens.
multiple blood cultures before commencing antibiotic therapy.

Repeat blood cultures are recommended 48–72 hours after commencing antimicrobial therapy.

Biopsy samples may be of value for bone infections

Imaging- X-ray, CT, MRI, Radionuclide imaging
Transthoracic echocardiography, TOE

Question 10

what is the basis of treatment for invasive staphylococcal
infections?

Answer 10

Antibiotic therapy
Source identification and clearance
and appropriate surgical intervention

Delay in the administration of appropriate antibiotic
therapy and persistent bacteraemia after 72–96 hours of
appropriate therapy, has been associated with an
increased risk of complications and higher mortality

Question 11

when is flucloxacillin used?

Answer 11

minimum duration of treatment for uncomplicated S. aureus bacteraemia is 14 days.

Question 12

when is vancomycin used?

Answer 12

far from an ideal drug due to poor tissue penetration, slow bactericidal activity, inconvenient administration and side effects.

Question 13

when is teicoplanin used?

Answer 13

has an advantage in terms of its single daily dosing and could also be used three times weekly after appropriate loading

Question 14

when is linezolid used?

Answer 14

bacteriostatic, synthetic oxazolidinone, good penetration into bone and excellent oral bioavailability.

Question 15

when is daptomycin?

Answer 15

cyclic lipopeptide with rapid bactericidal activity against S. aureus. Well tolerated. Has the advantage of once daily dosing.

Question 16

what is the guidance on management of proven or suspected staph a?

Answer 16

Question 17

47 year old lady with a background history of Injecting drug use presents to hospital with 5 day history of fever, cough and shortness of breath. She also complained of a painful swollen right groin.

She was alert and orientated on examination. O2 saturations were 90% on air, She was pyrexial at 38.5C. BP was 110/60, Pulse rate was 110 bpm, Respiratory rate was 32.

She did not have any known allergies.
No history of travel.

Bloods showed- WCC 31.9, Urea 8
Dopplar US showed a DVT ? Infected Right leg

What organism is likely to be responsible for the CXR findings?
What antibiotics would you commence her on?

Answer 17

staph aureus
iv Flucloxacillin

Question 18

Blood cultures were positive for S. aureus.

Despite 2 weeks on therapy, She complains of ongoing cough, fever and right sided chest discomfort and right groin pain and discharge.

Bloods showed WCC of 18 and CRP of 210.

You would perform which of the following investigations

Answer 18

ECHO
CXR
Repeat blood cultures
Ultrasound groin
All of above

CXR - empyema