Effects of antibiotics ceftriaxone and levofloxacin on the growth of Calliphora vomitoria L. (Diptera: Calliphoridae) and effects on the determination of the post-mortem interval

Abstract

The determination of the post-mortem interval (PMI) is one of the main tasks of forensic entomology, where growth and stages of development of arthropods are used for PMI determination. It is well acknowledged that maggot development is significantly influenced by temperature. Attention has also been paid to the microbial populations of the cadaver, because toxic substances contained in the substrate can influence the microorganisms and affect arthropods growth and development. However, little is known about the influence of antibiotics taken during lifetime of a person on insect development after that persons death. The aim of this study was to test the hypothesis that the antibiotics ceftriaxone and levofloxacin cause inhibition of growth and delay of pupation of the blow fly Calliphora vomitoria, which would then lead to an incorrect determination of the post-mortem interval in forensic cases. It was found that maggot development was delayed by levofloxacin mixed in minced pork, where a mixture of both antibiotics increased this effect. The maggot growth in the samples with ceftriaxone was not delayed. Pupation was delayed in treatments with a mixture of both antibiotics. The mortality was reduced by separate or combined application of ceftriaxone and levofloxacin, which we attribute to a bactericidal effect of the antibiotics on maggot pathogens. Depending on the concentration of the antibiotics, an underestimation of the post-mortem interval between 24 and 48 h could be suspected. We conclude that antibiotics need to be considered if instar stages are to be used to determine the PMI and that some antibiotics may improve the breeding conditions of maggots.