This practice is often followed in primary care settings as topical treatments are easily administered by the patient or carer. For example, topical Fusidic Acid is used for skin infections and topical Gentamicin for ear infections. HOWEVER, as a general rule topical applications are not good treatments for established infections.
Because it is impossible to know how much antibiotic is being used and for how long it has been in contact with the bacteria. This results in low level antibiotic exposure for sub-therapeutic periods of time; both of these factors are excellent ways of producing resistant bacteria. In fact, in the past, topical methods have been used to study how antibiotic mechanisms of resistance occur. In the case of topical Fusidic Acid used to treat skin infections the speed by which this resistant bacteria is created is very quick, often within a day or two. Pseudomonas in ears takes a little longer but usually resistance starts to appear within a few weeks.
It would therefore seem a little crazy to use a method to treat patients, which is known to develop resistance; 9/10 times the outcome will be a patient with altered normal flora to those that are antibiotic resistant bacteria.
But it does work!
I know there will be those out there who say these topical preparations work and patients get better but I would argue that there are other reasons why your patient may have improved.
- These ointments act as emollients and so they deal very nicely with conditions like eczema for which they are often prescribed
- They are often combined with steroids which damp down any inflammatory component of the infection. It is therefore usually the steroid in the ointment that gets the patient better, despite the presence of an
Patients who are known to be colonised with a certain bacteria may benefit from the use of topical antibiotics. In particular, the use of nasal mupirocin (Bactroban) as part of the suppression regimen of Meticillin Resistant Staphylococcus aureus, this reduces the amount of MRSA in a colonised patient’s nose and therefore reduces the risk of infection at a time when a patient undergoes a procedure. However, this suppression therapy rarely eliminates the MRSA and eventually resistance occurs making the Mupirocin obsolete. These patients eventually get break-through infections with resistant MRSA. Suppression therapy therefore only delays the inevitable infections in the long run.
So how should skin infections be treated? Well firstly, most apparent skin infections are not infections at all but inflammatory conditions and so antimicrobials are not
indicated. Where there is a definite infection e.g. cellulitis then the correct length and full doses of oral or IV antibiotics should be used, these treatment methods are less likely to lead to resistant bacteria evolving.
And on the subject of, should we really be using prophylactic suppression therapy, opinion is divided. Many Consultants and GPs choose to prescribe in this manner while Microbiologists feel this practise is storing up a problem. But that topic is for a whole new blog!