tell what people are searching for on Google and then blog about it. Something that has cropped up a few times is whether there are any specific operating theatre precautions for PVL positive Staphylococcus aureus. That’s Panton-Valentine Leukocidin not St. Valentine...this is not a dating blog!
possibility of transmitting an infectious microorganism to the patient either from the surgeon, another patient or even the operating theatre environment itself.
A number of factors play a role in influencing these
precautions, usually in the following order of precedence:
1. Operative procedure factors
2. Patient factors
3. Microorganism factors
Operative Procedure Factors
Certain operations require specific precautions to prevent
infection, either because the risk of infection occurring is high, or the risk to patient health in terms of morbidity or mortality is high if infection does occur, however unlikely that might be.
Risk of infection depends on the type of surgical procedure:
• Dirty e.g. where the bowel has perforated and faeces has leaked out into the peritoneum. Risk = 40% (reduces to 7% with prophylactic antibiotics)
• Contaminated e.g. where leakage does occur but it is contained quickly and effectively with suction and washing. Risk = 13% (reduces to 6% with prophylactic antibiotics)
• Clean-contaminated e.g. where an operation is taking place on the bowel which has been prepared with enemas and where there is no active infection beforehand. Risk = 6% (reduces to 3% with prophylactic antibiotics)
• Clean e.g. where the surgeon does not enter unclean areas such as abscesses or the bowel. Risk = 2% (unchanged by prophylactic antibiotics therefore prophylactic antibiotics not usually indicated)
Surgical procedures where prosthetic material is put into the
body require special care. If this prosthetic material becomes infected it is either very hard to remove (e.g. a prosthetic joint) or the infection has a high mortality (e.g. infected heart valve). These types of surgical procedure are often undertaken in specially designed laminar flow or ultra-clean operating theatres which have special ventilation that moves even small numbers of bacteria rapidly away from the operative field. These theatres reduce the risk of infection to less than 0.5%.
Various patient factors adversely affect the ability of body
tissue to heal including smoking, obesity, poor nutrition, diabetes mellitus, advancing age and alcoholism. These factors also impair white blood cell activity in the event of bacterial contamination of the surgical site and lead to higher infection rates.
Patients with these risk factors are encouraged to control these risks before an operation takes place e.g. losing weight, stopping smoking for months prior to the operation and controlling diabetes mellitus.
Certain bacteria are exceptionally good at causing infections.
Staphylococcus aureus is the most common cause of surgical or traumatic wound infections but other Gram-positive cocci such as the Beta-haemolytic Streptococci can also be responsible. Intra-abdominal infections, such as abscesses, following bowel surgery are usually caused by mixtures of bacteria from the normal bowel flora, not Staphylococcus aureus.
PVL positive Staphylococcus aureus produces a higher
rate of skin infections and this may be the reason why surgeons seek specific precautions. The PVL toxin (see previous blog), breaks down white blood cells (leucocytes) making it especially good at causing post-operative wound and other skin and soft tissue infections.
The best way of preventing wound infections with PVL positive Staphylococcus aureus is to not let it get in in the first place! As PVL positive Staphylococcus aureus is part of some patient’s normal flora it is important to 1) prevent
the bacteria entering and infecting their operative site and 2) to ensure the bacteria is not transmitted to other patients. Since PVL positive Staphylococcus aureus is usually transmitted between patients on the hands of healthcare staff or on contaminated equipment (fomites) good hand hygiene, use of clean operating theatre equipment and good surgical technique are the main factors for preventing endogenous and cross-infection. There is little evidence that using pre-operative treatments such as Mupirocin or Chlorhexidine are effective in reducing the risk of PVL positive Staphylococcus aureus infection from the patient’s own flora. Note: there is evidence that it is effective with
It is also important to ensure appropriate antibiotic
prophylaxis is used when necessary. The choice depends on the operation and the likely microorganism that will cause an infection, for example: a dental procedure and mouth flora versus prosthetic joint replacement and skin flora, the list is endless. Added to this, the sensitivity pattern of PVL positive Staphylococcus aureus varies, it can be either Methicillin sensitive or resistant. Prophylactic antibiotics should therefore be chosen on the basis of sensitivity,
not the presence of the PVL toxin itself. Despite my normal rant on the inappropriate use of antibiotics, surgery is often an entirely appropriate time to use antibiotic prophylaxis.
Having said all of this, it is still prudent to put patients who
are known to be colonised with particularly aggressive bacteria, such as PVL positive Staphylococcus aureus, last on an operating list. This then means that if for some reason there is a breakdown in other theatre precautions and the
environment becomes colonised with bacteria, there will always be a deep clean of the theatre before the next theatre list begins.
So are there specific theatre precautions for patients colonised with PVL positive Staphylococcus aureus? Essentially, NO there are not. All normal theatre precautions apply and are appropriate. Specific microorganism factors, such as PVL, are just one of a number of factors which affect the possibility of a post-operative infection and all of these should be controlled as much as possible to prevent infections.