We’ve previously addressed this topic here.   It’s certainly the case that chronic skin ulcers (leg or elsewhere) drive an enormous amount of antibiotic prescribing, perhaps because these ulcers are so hard to heal and a degree of therapeutic impatience occurs. The annual survey of chronic wounds last year in our health district indicated that 28% of inpatients with wounds had received antibiotic treatment in the preceding 2 weeks, unnecessary exposure that leads to increased individual and community risk from antibiotic resistance, C. difficile infection and other unintended consequences, including mortality.

Criteria for systemic antibiotics include:

• presence of cellulitis (don’t overcall it – more than just redness) – minimise duration of treatment (7-10 days maximum) and target Gram positives – beta-haemolytic Streptococci and Staphylococcus aureus.
• presence of underlying osteomyelitis (treatment may well require scalpelmycin – consult your surgeon- and also consult infectious diseases as prolonged treatment usually required)

Wound swabs are almost never appropriate as a positive result is not indicative of clinical infection per se and even in the presence of clinical infection, a positive result is often not indicative of the offending pathogen(s).

In patients with diabetic foot ulcers and underlying osteomyelitis, best practice is to culture a bone biopsy collected via intact skin – surface wound cultures are a poor substitute.  This schema for diagnosis of diabetic foot osteomyelitis may serve as a useful guide (from reference 2, International Working Group on the Diabetes Foot guidelines) .

Our laboratory comment attached to reports from chronic ulcer swabs advises:

References

1. Diabetes Metab Res Rev. 2016 Jan;32 Suppl 1:254-60. doi: 10.1002/dmrr.2736. Pitfalls in diagnosing diabetic foot infections. Peters EJ
2. Open Forum Infect Dis. 2014 Aug 7;1(2). Diagnosing diabetic foot osteomyelitis: narrative review and a suggested 2-step score-based diagnostic pathway for clinicians. Markanday A.