The diabetic foot
BMJ 2003; 326 doi: https://doi.org/10.1136/bmj.326.7396.977 (Published 03 May 2003) Cite this as: BMJ 2003;326:977All rapid responses
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Editor,
Watkins' ABC of the diabetic foot, while providing a succinct
summary, offers advice on antibiotic selection which may not amount to
current best practice in patients who exhibit 'danger signs' suggesting
abscess formation or gas in the tissues [1]. Watkins recommends that this
group should receive amoxicillin, flucloxacillin and metronidazole with
either ceftazidime or gentamicin. There are two important disadvantages
to this regimen in patients with the most severe infections.
Firstly, gentamicin, although effective for clearing a bacteraemia,
is a large polycationic molecule with low volume of distribution;
therefore, high plasma levels for a prolonged period (which is associated
with toxicity) are required to achieve adequate passage across biological
membranes [2]. Furthermore, gentamicin has lacking potency in the low pH
environment of abscesses.
Secondly, finding gas in the soft tissues of an ill diabetic patient
presenting with cellulitis raises the serious possibility of synergistic
gangrene. In such circumstances, clindamycin would be preferable to
flucloxacillin because of its effect on protein, and hence toxin,
production in Clostrium perfringens [3]. However, more important than
antibiotic management is an immediate surgical consultation for emergency
debridement.
Furthermore, the antibiotics Watkins lists as available treatments
for MRSA-infected diabetic foot ulcers are parenteral vancomycin and
teicoplanin. However, linezolid is an alternative which can be
administered orally; this may facilitate earlier hospital discharge. In
fact, its tissue penetration is superior and it has been associated with
better outcomes, in respect of several infection types including skin and
skin structure infections, in randomised-controlled trials [4,5].
Although Watkins acknowledges the possibility of modifying therapy in
the light of culture results, our experience is of disappointing yield
from ulcer swabs, particularly if the patient has previously received
antibiotics. Additionally, culture of contaminating organisms may
precipitate an inappropriate antibiotic change if not accompanied by
specialist advice. Hence, often, one cannot rely upon laboratory data to
correct inadequate empirical therapy.
We acknowledge that Watkins' suggested antibiotics are appropriate
for the majority of patients. Indeed, we approve of restricting the
prescription of potent, broad spectrum, agents with a view to antibiotic
conservation. However, it becomes increasingly important to chose the
best available antibiotic (considering spectrum of antibacterial activity
as well as pharmacokinetics / pharmacodynamics) when treating patients in
whom severity of illness is greater. With this in mind, when managing
those patients who have severe infections, consultation with an infection
specialist may be prudent.
REFERENCES
1. Watkins PJ. The diabetic foot. BMJ 2003;326:977-9
2. Gilbert DN. Aminoglycosides. In: Mandell GL, Bennett JE, Dolin R.
Principles and Practice of Infectious Diseases, Churchill Livingstone,
2000
3. Stevens DL, Maier KA, Mitten JE. Effects of antibiotics on toxin
production and viability of Clostridium perfringens. Antimicrob Agents
Chemother 1987;31:312-16
4. Wilcox M et al. Interscience Conference on Antimicrobial Agents and
Chemotherapy, 2001: Poster 1481
5. Leach TS, Kaja RW, Eckert SM et al. Linezolid versus vancomycin for the
treatment of MRSA infections: results of a randomised phase III trial.
Ninth International Congress of Infectious Diseases, April 2000:224
Competing interests:
None declared
Competing interests: No competing interests
Editor,
In his excellent review “The Diabetic Foot” (1) Dr Peter J Watkins
states that metformin should be stopped 48 hours prior to angiography and
reinstated 48 hours after in order to minimise potential renal risk. This
contradicts the current guidelines published by the Royal College of
Radiologists on the use of iodinated contrast medium (2) which state that
in patients with normal renal function metformin be stopped before or at
the time of the contrast examination and for the subsequent 48 hours. The
British Diabetic Association states that metformin is contraindicated in
those with abnormal renal function and therefore these patients should
have their drug regimen reviewed.
1. Watkins P J. The Diabetic Foot. BMJ 2003;326:977-979
2. Weir J. Guidelines with Regard to Metformin-Induced Lactic Acidosis and
X-ray Contrast Medium Agents. 1999
http://www.rcr.ac.uk/pubtop.asp?PublicationID=70
Competing interests:
None declared
Competing interests: No competing interests
Diabetic foot ………….a ‘western form’ of leprosy foot ?
Just to comment on your article ABC of diabetes - the diabetic foot1.
Those of us who have worked in leprosy clinics abroad cannot but be
impressed by the striking resemblance between diabetic foot and leprosy
foot. World wide about 3 million leprosy patients are physically disabled
as a result of damage to peripheral nerves and the attendant sensorimotor
loss2. This is a consequence of infection with an intracellular obligate
pathogen (Mycobacterium leprae) which is unique among bacteria in its
ability to invade peripheral nervous system3.The pathogenesis and the
principles of management of diabetic and leprosy feet are similar. Perhaps
both can learn from each others’ experience?
I. A. Hassan consultant microbiologist
Manchester Royal Infirmary M13 9WL.
Ihassan@doctors.org.uk.
1. Watkins PJ.ABC of diabetes - the diabetic foot. BMJ 2003;326:977-
9.(3rd May).
2. Leprosy situation by WHO regions end of 2000. www.who.int/lep/12.htm.
3. Pfaltzgraff RE, Bryceson A. Leprosy. 1984 p. 134-5 In Hastings (ed).
Churchill Livingstone, UK.
Competing interests:
None declared
Competing interests: No competing interests