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.

Posttraumatic infection and osteomyelitis is a difficult to treat complication. Despite surgical interventions, there is great risk for recurrence of the infection and development of an invalidating osteomyelitis. For this reason, a retrospective, case control cohort study on patients with posttraumatic osteomyelitis was performed to evaluate the clinical outcome of a new therapy, i.e. VAC Instillation with Lavasept®, an instillation technique applied after the initial surgical debridement.

In the time period from 2/1999 to 2/2003, thirty three patients with posttraumatic osteomyelitis were included and were treated with the VAC technique and the white polyvinyl alcohol (PVA) foam in combination with lavasept® instillation. The PVA foam was instilled 3 times per day with a disinfectant fluid agent lavasept 0.2 % (polyhexanidum solution). The average time of treatment was 21 days (6–60). The average time that infected wounds became sterile or skin bacteria could be cultured (88.1 %) was 12 days (range 4 – 38; SD 8.9). The follow-up time was up to 72 months. For comparison a historical control group of 94 patients (male 58, mean age 47 (r 9–85) matched for site and severity of osteomyelitis, was identified in hospital records for a period of 20 years (1982–2002). These patients were treated with debridement, lavage and gentamycin beads.

Both groups were statistical comparable to sex, age, comorbidity and site of the osteomyelitis. In the V.A.C.® Instill® group the rate of recurrence of infection was 3/30 (10%), whereas 55/93 (58.5%) of the controls had a recurrence (p< 0.0001). Moreover, in those treated with VAC Instillation, the duration of hospital stay was shorter and the number of admissions and surgical procedures were smaller as compared with the controls (all p< 0.0001).

We conclude that in posttraumatic osteomyelitis VAC Instillation treatment may improve clinical outcome and reduce the need for repeated surgical interventions and hospital admissions in comparison to the present standard approach.

Maggot therapy as an ancient method is succesfully used for treatment of acute and chronic wound infections in traumatology and orthopaedics. In this study, for the first time, the influence of sterile maggot excretions of Lucilia sericata on Pseudomonas aeruginosa (PAO1) biofilm formation on three common used orthopaedic materials was investigated.

Sterile maggot excretions were collected according to a standardized method and the protein concentration was measured. The influence of the excretions on PAO1-biofilm formation was tested on comb-like devices, especially designed for these experiments, made from polyethylene, titanium and stainless steel. These combs were made to fit into a flat-bottom 96-wells microtiter plate. In the wells a suspension of PAO1-bacteria, nutrient medium and maggot excretions were pipetted. In the control wells, no excretions were added. Combs were placed in the wells and incubated for 24 hours at 37°C. The formed biofilms were stained in crystal violet and eluted with ethanol. The Optical Density (OD 595 nm) was read to quantify biofilm formation. The experiments were conducted with excretions from young maggots (Instar-1 maggots) and full grown maggots (Instar-3 maggots). All experiments were done in quadruplicate.

The following can be concluded: PAO1-biofilm formation is the strongest on polyethylene and the weakest on stainless steel. Sterile maggot excretions are effective at preventing initial biofilm formation (p≤0.013) as well as preventing additional accumulation after its initiation (p≤0.038). The excretions even cause a significant breakdown of an existing biofilm (p≤0.028). Excretions from full grown maggots are more effective than those from young maggots.

This study shows for the first time that sterile maggot excretions of Lucilia sericata inhibit biofilm formation, prevent its further grow and break down existing biofilms. While biofilm formation on orthopaedic materials is a severe complication, this experimental study could indicate a new treatment for biofilm formation on infected biomaterials.