Journal Citation

Daeschlein G, Napp M, Assadian O, von Podewils S, Reese K, Hinz P, Matiasek J, Spitzmueller R, Humphreys P, Jünger M, Kramer A. Viability of Lucilia sericata maggots after exposure to wound antiseptics. Int Wound J 2017; 14:512–515

Published Abstract

After debridement and before dressing a wound with maggots of calliphorid flies, one frequently performed step is the application of antiseptics to the prepared wound bed. However, the concomitant application of antiseptic agents during maggot therapy is regarded controversial as antiseptics may interfere with maggots’ viability. In this experimental in vitro study, the viability of fly maggots was investigated after exposure to various antiseptics frequently used in wound care. Here, we show that Lucilia sericata fly maggots can survive up to an hour’s exposure to wound antiseptics such as octenidine, povidone-iodine or polihexanide. Concomitant short-term application of wound antiseptics together with maggots on wound beds is tolerated by larvae and does not impair their viability.

Context (briefly, why and how the research was carried out)

In clinical practice wounds may be treated with antiseptics prior to application of maggot therapy. The effect of these antiseptics on medicinal maggots has been unclear and this research sought to determine whether fly maggots remain viable during and after exposure to the following commonly used wound and skin antiseptics, hand rubs and disinfectants:

Octenisept®

0⋅1% octenidine dihydrochloride, 2% phenoxyethanole

Lavasept®

0⋅04% polyhexanide

Betaisodona®

10%povidone-iodine

Manorapid synergy®

57⋅6% of ethanol 96%, 10% 1-propanol

Ethanol

70% ethanol

Lysoformin 3000®

7.5% glyoxal, 9.5% glutaral, 9.6% didecyldimethyl-ammoniumchloride

Descogen F®

60% potassium peroxymonosulfate

Disifin med® (powder)

90% tosylchloramine sodium

Wofasteril®

35% peracetic acid

Wofasept®

5% chlorocresol, 2%chlorofen, 5–15%anionic tensides

Control

0.9% Sterile saline

In the experiment, maggots were fully immersed for either 1, 2, 5, 10, 30 or 60 minutes in the antiseptic product made up to recommended concentration. Thereafter, maggots were washed three times and placed for 2 hours on Columbia agar for viability monitoring. Follow-up observations for up to three days were made for initially immobile larvae.

In an additional experiment, larvae treated with 70% ethanol, Betaisodona®, Octenisept®, Lavasept®, Disifin med®, Descogen F® and sterile saline were placed in bacterial suspensions containing Staphylococcus aureus to assess their ability to control infection after exposure to antiseptics.

Findings

The three wound antiseptics impacted somewhat on maggot motility and caused up to 19% reduction in the efficacy of maggots to control S. aureus. However, the other antiseptics used for surface and/or instrument disinfection had far greater detrimental impact on larval morbidity and mortality and the maggot’s ability to control S. aureus. With the exception of ethanol and Lysoformin 3000®, these antiseptics led to variable reduction in motility as soon as 1 or 2 minutes from exposure and major maggot mortality of up to 50% in the case of Wolfasteril® and Wolfasept®. Ethanol neither reduced maggot motility nor ability to reduce S. aureus burden. The 1-propanol containing hand rub caused obvious morbidity and mortality due to the toxicity of propanol compared to ethanol. The two surface sterilizers Descogen F® and Disifin med® not only had an obvious effect on maggot wellbeing but also reduced the maggots’ ability to control infection in the order of 74% for Descogen F® and 61% for Disifin med®.

Discussion (looking at author’s conclusions and your own thoughts)

This paper has been an important first step in answering the question whether treatment of wounds with antiseptics is compatible with maggot therapy. The results presented here suggest that maggots may be sufficiently resilient to withstand temporary exposure. However, further research is necessary that aligns more closely with true wound conditions, clinical practice and calliphorid biology before the green light can be given for the concomitant use of wound antiseptics with maggot therapy. 

To that end, the paper would have been enriched by more detailed information as to the use of wound antiseptics in clinical practice either by themselves or in conjunction with maggot debridement therapy. The reader would have benefited from learning when topical wound antiseptics are indicated and in what manner they are applied, including quantity and frequency. These practical considerations are important when discussing concomitant use of antiseptics with maggot therapy in clinical practice. Consideration of clinical practice may also have led to the exclusion of hand-rubs and disinfectants from the experimental protocol because they are unlikely to pose a relevant risk to medicinal maggots in clinical practice.

The authors briefly mention that wound antiseptics may be used before the application of medicinal maggots and that the experiments were conducted with third instar maggots which ought to be much more resilient to environmental insults than early-stage maggots. Importantly, given the ability of medicinal maggots to control wound infection, it is probably rare that clinicians would consider applying topical antiseptics during maggot therapy. The compatibility of antibiotics, however, has been shown to be safe and indeed synergistic (Cazander et al., 2010, Peck and Kirkup, 2012). Consequently, in clinical practice, fragile small early second instar larvae that are usually applied to wounds for maggot therapy would be exposed to antiseptics and not third instars. For this reason, future studies should align experiments closer with the use of antiseptics in the treatment cycle and match the corresponding maggot development stage in the experiment.

The wound is unlike a test-tube that maintains content volume and concentration. The wounds treated with maggot therapy often produce lots of exudate which further increases in the presence of medicinal maggots. Given the diluting effect of exudate and maggot excretions/secretions, and liquefaction of necrotic wound tissue, the concentration of any antiseptic would quickly decrease provided the medicinal maggots survive the first few hours in the wound and are well enough to convey therapeutic benefit.  

The paper reports on the initial mortality and morbidity, as expressed in reduced motility, but not the performance of medicinal maggots over the likely maggot therapy treatment time of 2 to 4 days. It is plausible that the antibiotic effect measured is the result of the briefly remaining ability to produce secretions and void excretions but which may rapidly decrease with the health of the maggot. It is not clear how severely the longer-term health of exposed medicinal maggots is affected and whether they are able to survive and provide therapeutic benefits for the full period of debridement (2-4 days depending on dressing modality), especially because it is in all likelihood early second instar maggots that are exposed to antiseptics. In addition to immediate exposure, the chronic low-level presence of these chemicals in the wound and dressing materials also needs to be considered.

Moreover, the reviewer notes the absence of any statistical analysis of results which weakens the relevance of reported results considerably.

In summary, it may be premature of the authors to conclude that “Concomitant short-term application of wound antiseptics together with maggots on wound beds is tolerated by larvae and does not impair their viability”. This research would have been more conclusive and practice-relevant if early second instar maggots had been used and if the experimental protocol had allowed for morbidity, mortality and performance testing of maggots over a period of four days. Moreover, debridement efficacy ought to be a good proxy for overall maggot health and the ability of maggots to produce excretions and secretions that control pathogens in the wound. It may therefore be instructive in future experiments to focus on performance and viability testing of antiseptic-treated maggots using artificial wound models as in  Blake et al. (2007) and  Čičková et al. (2015).

 

-Reviewed by: Anonymous

 

References Cited

BLAKE, F. A. S., ABROMEIT, N., BUBENHEIM, M., LI, L. & SCHMELZLE, R. 2007. The biosurgical wound debridement: experimental investigation of efficiency and practicability. Wound Repair & Regeneration, 15, 756-761.

CAZANDER, G., PAWIROREDJO, J. S., VANDENBROUCKE-GRAULS, C. M. J., SCHREURS, M. W. J. & JUKEMA, G. N. 2010. Synergism between maggot excretions and antibiotics. Wound Repair & Regeneration, 18, 637-642.

ČIČKOVÁ, H., KOZÁNEK, M. & TAKÁČ, P. 2015. Growth and survival of blowfly Lucilia sericata larvae under simulated wound conditions: Implications for maggot debridement therapy. Medical and Veterinary Entomology, 29, 416-424.

PECK, G. W. & KIRKUP, B. C. 2012. Biocompatibility of antimicrobials to maggot debridement therapy: medical maggots Lucilia sericata (Diptera: Calliphoridae) exhibit tolerance to clinical maximum doses of antimicrobials. J Med Entomol, 49, 1137-43.

 

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