Abstract
In the literature a lot is written about the antibacterial properties that maggots and their secretions are thought to possess, with inconsistencies among different studies. This study investigates the mechanism of the successful clearance of infections in wounds by maggots through examining living maggots and their excretions.
To test the excretions a turbidometric assay was carried out. The sterile excretions were pipetted in different dilutions into a microtiter plate and had bacteria added. Five bacteria were tested, viz. S. aureus, S. pyogenes, E. faecalis, P. aeruginosa and K. oxytoca. After 20 hours the wells were checked. Clear wells presented bacteriolytic activity, whereas cloudy wells presented bacterial growth.
Putting maggots in tubes together with bacterial suspension tested the effect of living maggots. Control tubes contained bacteria only. Same bacteria as ascribed above were used, except for E. faecalis that was changed for coagulase-negative Streptococ. Young maggots (Instar-1) and full-grown maggots (Instar-3) were used, and as a medium for the suspension, Muller Hinton (MH) was used with and without 5% sheep blood. The tubes were horizontally incubated for 16 hours, and every two hours a sample was taken and put onto an agar plate. After 24 hours, the bacterial colonies were counted.
The turbidometric assay showed cloudy wells for all bacteria and dilutions with the less diluted excrete showing the highest stimulation of bacterial growth.
The test with living maggots showed increased bacterial growth as compared to the controls (p=0.001 using the S. aureus). Young maggots stimulated growth more than full-grown maggots (p=0.002 using the S. aureus). Using a more nutritious medium, viz. MH with 5% sheep blood, no difference in growth of bacteria was observed between the tubes with maggots and the controls (p=0.271 using the S. aureus). The other bacteria gave similar results.
This study shows that other mechanisms must be accounted for the clearance of infections in wounds by maggots than their proposed antibacterial properties.
Correspondence should be addressed to Vasiliki Boukouvala at Department of Orthopaedic Surgery & Traumatology, University Hospital of Larissa, 110 Mezourlo, Larissa, GREECE. Tel: +30 2410 682722, Fax: +30 2410 670107, Email: malizos@med.uth.gr
