Bacterial colonization of chronic leg ulcers: current results compared with data 5 years ago in a specialized dermatology department

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Abstract
In nearly every chronic wound different bacteria species can be detected. Nevertheless, the presence of such microorganisms is not necessarily obligatory associated with a delayed wound healing. But from this initially unproblematic colonization an infection up to a sepsis can arise in some patients. The aim of our clinical investigation was to analyse the spectrum of microbial colonization of patients with a chronic leg ulcer in our specialized dermatological outpatient wound clinic, and to compare them with the results of comparable data already collected 5 years ago. In our retrospective investigation the results of bacteriological swabs were documented in 100 patients with a total of 107 chronic leg ulcers. All patients visited the specialized wound outpatient clinic, Department of Dermatology, University of Essen in Germany. A total of 60 patients were female, 40 were male. The mean age was 65 years. Altogether a total of 191 bacterial isolates and 25 different bacterial species could be identified. The most often detected species were Staphylococcus aureus (n = 60), Pseudomonas aeruginosa (n = 36) as well as Proteus mirabilis (n = 17). In 10 patients (10%) we identified a colonization with methicillin resistant S. aureus (MRSA). Merely in 6 patients the taken swabs were sterile. Five years ago a comparable investigation was already carried out in our wound outpatient clinic. At that time we could detect in particular more frequent MRSA (21.5% vs. 10%) and rarely P. aeruginosa (24.1% vs. 33.6%). The results of our investigation demonstrate the current spectrum of the bacterial colonization in patients with chronic leg ulcers in a university dermatological wound centre in comparison to the last 5 years. In our institution we were able to demonstrate a shift of the detected bacterial species from gram-positive in direction to gram-negative germs. Beside the already known problems with MRSA, in future therapeutic strategies in patients with chronic leg ulcers the increasing amount of gram-negative bacteria and especially of P. aeruginosa should considered.