Staphylococci

Question 1

S. Aureus is
Gram …
Often found on the …. and in the …. ……… ….
Transmitted via ….. or …. ……

Answer 1

Positive
Skin upper respiratory tract
Aerosol direct contact

Is also spherical, non motile, an opportunistic pathogen and aerobic or facultative anaerobe

Question 2

What % of the population us colonised with s aureus

Answer 2

30%

Question 3

What do MRSA and MSSA stand for

Answer 3

Methicillin resistant staphylococcus aureus

Methiscillin sensitive staphylococcus aureus

Question 4

What is the general mode of action of beta lactam antibiotics

Answer 4

Beta lactam interaction with penicillin binding proteins (PBP) blocks cross linking of NAM and NAG which compromises cell wall rigidity. The cell is weakened and more prone to external stress

Question 5

How is MRSA resistant to antibiotics

Answer 5

MRSA utilises PBP2a (and not PBP2) which has low affinity for beta lactams as it has a close off active site. Transpeptidation occurs as normal kn the presence of the beta lactam due to the expression of an altered target

Question 6

What do nam and nag stand for

Answer 6

N-acetyl muramic acid

N-acetyl glucosamine

Question 7

Can MRSA and MSSA be distinguished based on appearance

Answer 7

No, their only distinguishing feature is their sntibiotic susceptibility profiles

Question 8

Which antibiotic classes is mrsa resistant to

Answer 8

Methicillin, penicillin, cephalosporins (except newest class), carbapenems

Question 9

What are the main differences between hospital acquired (HAMRSA) and community acquired MRSA

Answer 9

The age of the at risk groups
Ha - mean age 68yrs (prior hospitalisation, surgery, indwelling device)
Ca - mean age 23yrs (children, homeless, inmates, athletes, military)

Infection sites
Uti and respiratory infections - ha
Skin and soft tissue infections - ca

Question 10

Which is more resistant : hospital or community acquired resistance

Answer 10

Hospital - its multi drug resistant

Question 11

Name a common skin infection caused by S. Aureus

Answer 11

Impetigo

Question 12

How does impetigo get into the body and how does it present

Answer 12

Through minor trauma or carriage in nasal cavity

Presents as bullous (ball like) or non bullous (70% cases)

Question 13

Which season are impetigo cases higher

Answer 13

Summer - due to children being outdoors with extremities exposed to the elements (more likely to cut themselves) also due to insect bites (even in uk)

Question 14

What are the treatment options for impetigo

Answer 14

Mild, localised - fusidic acid cream (5days, t.d.s) (mupirocin if MRSA)
Bullous or widespread: oral fluxloxacillin (7days, q.d.s) or oral clarythromycin (7days b.d.s)

If recurrent consider nasal swabs for carriage and decolonisation

Question 15

What is the pharmavists role when considering impetigo

Answer 15

Endorsing public health - hand washing, short fingernails, school/nursery isolation, management of broken skin conditions

(The crusty bulous can spread disease)

Question 16

What is a common bacterial eye infection caused by s. Aureus (in children, elderly, diabetics and immunocompromised)

Answer 16

Conjunctivitis (note, there can be other causes such as streptococci, chlamydia, gonorrhoea, viruses or allergic conjunctivitis)

Question 17

How is bacterial conjunctivitis spread

Answer 17

Hand to eye contact or via formite-to-eye contact

Question 18

What are the symptoms of bacterial conjunctivitis?

Answer 18

Grittiness in the eye, itching, discharge, pink eye

Complications can cause scarring or secondary infection

Question 19

What are the treatment options for bacterial conjunctivitis

Answer 19

Often self limiting within 5-7 days - just keep eyes clean
Chloramphenicol (0.5%) eyedrops- 1 drop hourly for 2d then 4 drops daily for 5 days
Chloramphenicol (1%) ointment (if child doesn’t want drops) - 4 times daily for 2 days then 2 times daily for 5 days
Fusidic acid (1%) eyedrops - second line. 2 times daily for 7 days

Topicql preparations prevent systemic toxicity

Question 20

What is the pharmacists role surrounding conjunctivitis

Answer 20

OTC sales of chloramphenicol drops (POM-P switch)
Under a PGD - chloramphenicol/fusidic acid is available on the MAS as part of the pharmacy first scheme

Other health advice
Regular hand washing, good eye care, no contact lense use, replace towels, pillows and makeup applicators

Question 21

What is an indwelling device

Answer 21

A human made item which is grafted into or onto a human host eg a catheter, artificial knees etc

Question 22

What is the added issue surrounding bacterial infections of indwelling devices

Answer 22

Biofilms - it is proposed that 65% of HCAI (healtjcare associated infections) involve biofilms

Question 23

Why are biofilm associated infections particularly dangerous

Answer 23

They require a low inoculum
Respond poorly to antibiotics and antimicrobials
And are often recurrent

It is much easier for biofilms to form on prosthetic surfaces - the immune response differs to human tissue which has a blood flow

Question 24

What is the common cause of prosthetic joint infections

Answer 24

S. Aureus being introduced to the body via contamination during surgery (infection will usually occur within a year)

Question 25

Which areas are particularly susceptible to MRSA infection from indwelling devices

Answer 25

Vascular or urinary catheters
Tracheostomy tubes
Feeding tubes
CNS shunts 
Orthopaedic implants

These all have areas both inside and outside the body giving bacteria a route to bypass the skin’s defences

Question 26

General signs and symptoms of indwelling devices infection

Answer 26

Greatly variable due to the many different types of devices which can become infected
Warmth at the infection site, redness and exudate
If left untreated there is potential for systemic infection (fever, malaise, elevated hr). These can be symptoms of septicemia

Question 27

What is the treatment for indwelling device infectioms

Answer 27

For something like a catheter - remove the device and replace with a new one
Sometimes surgical removal of infected tissue is required
When removal of the device isn’t instantly possible, IV antibiotic - flucloxacillin, clarithromycin, vancomycin, rifampicin, clindamycin, linezolid. All on a 7-10 day course

NB, biofilms are exceptionally difficult to treat

Question 28

What is the pharmacists role surrounding indwelling device infections

Answer 28

Infection control training for patients, carers, care home staff
Counselling for patients on prevention therapy/pre screening
Wards - patient identification and isolation: gloves, aprons when with MRSA colonised patients