Use of maggot therapy for treating a diabetic foot ulcer colonized by multidrug resistant bacteria in Brazil

Maggot therapy is known to be used in chronic wounds to remove necrotic tissue, stimulate granulation tissue formation and kill bacteria12. In diabetic foot ulcers with the problem of bacterial resistance, this therapy has been used as an alternative treatment of these ulcers. We report here a case study in Brazil using maggot therapy for treating chronic ulcers infected with multidrug-resistant bacteria in a diabetic patient.

A 74 year old female patient having diabetes for over 30 years, reported to the Surgical Clinic Department, University Hospital Onofre Lopes (HUOL)- University Federal do Rio Grande do Norte, Brazil, with a foot ulcer in August 2012. The second instar larvae of the Chrysomya megacephala (Diptera: Calliphoridae) were used in this study for maggot therapy and the maintenance and eggs disinfection processes were performed using procedures recommended by Marcondes3. The larvae were obtained from established colonies in the insectory of Laboratory of Insect and Vectors, Department of Microbiology and Parasitology, Biosciences Center, Federal University of Rio Grande do Norte. The larvae were removed from the medium, washed with sterile water and transferred to a sterile container. The technique of maggot therapy consisted of an initial wash with saturated sodium chloride followed by collection of clinical specimens for microbiological analysis and application of the free-range larvae (5 per cm² of tissue compromised) directly at the ulcer. The clinical specimen was sent in Stuart transport medium (Difco Laboratories, USA) to Mycobacteria Laboratory, department of Microbiology and Parasitology, Federal University of Rio Grande do Norte. The processing of clinical specimens was performed using procedures and culture media recommended by Murray et al4. Biochemical tests were performed for bacteria identification at species level. To perform the antimicrobial sensibility test (AST), the Kirby-Bauer's agar disk diffusion method was used5. The bacterial strains that showed the multidrug resistance pattern were subjected to genotypic analysis to confirm the presence of genes encoding TEM, SHV, and CTX-M6. Strains of Escherichia coli (ATCC 25922) and Klebsiella pneumoniae (ATCC 700603) were included as controls.

The study was approved by the ethics committee of the Federal University of Rio Grande do Norte, Brazil. Six biological dressings were done with an interval of every 48 h. Before therapy, an extension of tissue impairment of 8.4 cm² was obtained (Fig. A) and after two weeks of treatment (14 days) a retraction of the ulcer 0.7 cm2 was observed (Fig. B). At the end of treatment (43 days) the ulcer's surface area was occupied by granulation tissue (Fig. C). The maggot therapy was found to be an effective and inexpensive method of debridement, providing a rapid acceleration in the process of wound healing78. Importantly, the effect of using the debridement maggot therapy occurs not only by the physical activity of larvae (by their mandibles) but also by secretions and excretions such as trypsin, collagenase, and chymotrypsin, showing that the lytic activity is able to promote the dissolution of necrotic tissue. This therapy also eliminated multidrug resistant microorganisms (K. pneumoniae, E. coli, Pseudomonas aeruginosa) present in the wound, as reported earler9. The SHV and CTX-M genotypes were observed only in the K. pneumoniae isolates. These results indicated the presence of ESBL (extended-spectrum beta-lactamase) in bacteria. Bexfield et al10 demonstrated the efficacy of these compounds against strains of methicillin-resistant Staphylocccus aureus and other bacteria. Several peptides produced in whole body extract of maggots with high antimicrobial activity as well as compounds present in their haemolymph have been shown to have activity against P. aeruginosa11.

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Fig. 1

Patient's foot ulcer before and after the maggot therapy. (A). Measurement of the extent of necrosis and application of treatment (day 1). Asterisks represent areas of tissue necrosis. (B). Patient's foot ulcer image during treatment with maggot therapy (day 14). The asterisks represent areas of tissue necrosis and the arrows indicate the larvae of Chrysomya megacephala. (C). Patient's foot ulcer image after treatment with maggot therapy (day 43).

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In conclusion, considering the role of maggot therapy in wound healing, particularly in diabetic ulcer and its low cost compared with the other usual treatments, there is a need to evaluate its safety and efficacy on a large number of patients.