Methicillin Resistant Staphylococcus aureus (MRSA)

Dr John Cheesbrough, Consultant Microbiologist, LTHTR

Methicillin Resistant Staphylococcus aureus (MRSA) and other hospital flora; What can the surgeon do minimise the risk?

Three microbes often acquired in health care facilities: MRSA, Clostridium difficile and various coliforms expressing ESBL s and fluroquinolone resistance - most notably Multi-resistant E. coli (MREC) warrant special attention.
MRSA has acquired the status of the pre-eminent health care associated infection (HCAI) in the UK thanks to its high profile in the popular media and the DoH making the reduction of MRSA bacteraemia rates a key target for all Trusts. As such it has become a surrogate marker for the effectiveness of Infection Control Measures.

Clostridium difficile is arguably a much better indicator of Infection Control effectiveness as it occurs at a much higher frequency, has a major environmental reservoir and will respond much more reliably to enhanced hygiene and tight antibiotic control. It is also associated with a much higher morbidity and mortality than MRSA with over 30% mortality within 3 months. While most deaths are due to underlying disease than direct consequence of C. difficile, it is often a contributory factor and can be a very important cause of end of life morbidity.
MREC has emerged across the UK since 2005. While there is still substantial variation in local sensitivity patterns (especially to gentamicin) all are resistant to cephalosporins and quinolones. These are mainly a cause of UTI and bacteraemia, which is associated with a mortality of around 30%. Chronic asymptomic carriage in the GIT tract is often present and some studies have found carriage rates of over 40% in nursing home residents.
A unifying feature of all three of these problem microbes is that the majority of clinical infections are due to a very limited number of clones, which have co-acquired both antibiotic resistance and key virulence factors. Resistance to flouroquinolones is found in all three and this class of antibiotic is most clearly associated with their acquisition. Prudent antibiotic use is a critical component of any stragety designed to reduce risk and should emphasise the following points:

• When a microbiology result comes back ask yourself: is this germ harming my patient? Avoid treating results as a routine.
• Assess for presence of risk factors for MRSA, C. difficle and MREC.
• Limit prophylaxis to a single dose given with induction of anaesthesia and consider modifying choice of antibiotic if patients is at risk of MRSA or MREC,
• Limit duration of course to five days for “simple” intercurrent infections.
• Avoid agents with a high risk of inducing C. difficile such as 3rd generation cephalosporins and fluroquinolones as far as possible, but remember almost any antibiotic can cause C. difficile and reduction of overall antibiotic use is important.