Staphylococci Flashcards
S. Aureus is
Gram …
Often found on the …. and in the …. ……… ….
Transmitted via ….. or …. ……
Positive
Skin upper respiratory tract
Aerosol direct contact
Is also spherical, non motile, an opportunistic pathogen and aerobic or facultative anaerobe
What % of the population us colonised with s aureus
30%
What do MRSA and MSSA stand for
Methicillin resistant staphylococcus aureus
Methiscillin sensitive staphylococcus aureus
What is the general mode of action of beta lactam antibiotics
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
How is MRSA resistant to antibiotics
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
What do nam and nag stand for
N-acetyl muramic acid
N-acetyl glucosamine
Can MRSA and MSSA be distinguished based on appearance
No, their only distinguishing feature is their sntibiotic susceptibility profiles
Which antibiotic classes is mrsa resistant to
Methicillin, penicillin, cephalosporins (except newest class), carbapenems
What are the main differences between hospital acquired (HAMRSA) and community acquired MRSA
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
Which is more resistant : hospital or community acquired resistance
Hospital - its multi drug resistant
Name a common skin infection caused by S. Aureus
Impetigo
How does impetigo get into the body and how does it present
Through minor trauma or carriage in nasal cavity
Presents as bullous (ball like) or non bullous (70% cases)
Which season are impetigo cases higher
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)
What are the treatment options for impetigo
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
What is the pharmavists role when considering impetigo
Endorsing public health - hand washing, short fingernails, school/nursery isolation, management of broken skin conditions
(The crusty bulous can spread disease)
What is a common bacterial eye infection caused by s. Aureus (in children, elderly, diabetics and immunocompromised)
Conjunctivitis (note, there can be other causes such as streptococci, chlamydia, gonorrhoea, viruses or allergic conjunctivitis)
How is bacterial conjunctivitis spread
Hand to eye contact or via formite-to-eye contact
What are the symptoms of bacterial conjunctivitis?
Grittiness in the eye, itching, discharge, pink eye
Complications can cause scarring or secondary infection
What are the treatment options for bacterial conjunctivitis
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
What is the pharmacists role surrounding conjunctivitis
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
What is an indwelling device
A human made item which is grafted into or onto a human host eg a catheter, artificial knees etc
What is the added issue surrounding bacterial infections of indwelling devices
Biofilms - it is proposed that 65% of HCAI (healtjcare associated infections) involve biofilms
Why are biofilm associated infections particularly dangerous
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
What is the common cause of prosthetic joint infections
S. Aureus being introduced to the body via contamination during surgery (infection will usually occur within a year)
Which areas are particularly susceptible to MRSA infection from indwelling devices
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
General signs and symptoms of indwelling devices infection
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
What is the treatment for indwelling device infectioms
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
What is the pharmacists role surrounding indwelling device infections
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
