The influence of maggot debridement therapy on the bacterial flora of hard-to-heal wounds.

Objective: Maggot debridement therapy (MDT) is increasingly being used in clinical practice as an alternative treatment for hard-to-heal (chronic) wounds. Among the many benefits of using MDT is its antimicrobial effect. Maggots secrete substances that are known to have antibacterial properties against both Gram-negative and Gram-positive bacteria. Clinically, this results in the effective eradication of pathogenic species and consequently, a faster healing process. The aim of this study was to evaluate the effect MDT has on the bacterial flora of hard-to-heal ulcers.

Method: Patients with venous, mixed arteriovenous, decubitus, diabetic and neuropathic wounds were treated with larvae of Lucilia sericata enclosed in bags. Dressings were applied to the wounds for 72 hours. Before and after the therapy, a swab was taken from the wound, and bacterial diversity and bacterial growth scores were assessed. While 16 patients were treated only once, the treatment had to be repeated in four cases until the wounds were fully debrided.

Results: Bacteria of the species Pseudomonas aeruginosa, Proteus mirabilis, Staphylococcus aureus and Enterococcus faecalis were the most common strains observed. Of the 20 patients treated, the total number of bacterial strains decreased in eight wounds, but increased in five wounds, while no difference was observed in nine wounds. The average number of bacterial strains in wounds decreased after MDT. A lower incidence of alarm pathogens was also reported. In cases where multiple applications of larvae were administered, greater decreases in bacterial growth scores were observed than in cases with a single application of dressing (37.5% vs 18.1%, respectively). In 18 cases, after disinfection of the wound by larvae, it was reinfected by strains not detected before. Wounds healed completely after MDT in two patients.

Conclusion: In this study, MDT changed the bacterial diversity of hard-to-heal wounds. The larvae reduced overall bacterial growth scores and acted on both Gram-positive and Gram-negative bacteria as well as on alarm pathogens. Cleaned wounds appeared to become vulnerable to infection by opportunistic bacteria. The bacterial burden decreased as the number of applications of biological dressings increased.