Potential use of bacterial community observed during decomposition of pig (Sus scrofa domesticus) and sheep (Ovisaries) carrion in estimating the post-mortem interval during the cold season in KwaZulu-Natal Province of South Africa.

Abstract

This study was aimed at identifying and describing the bacterial communities present during the decomposition stages of both pig and sheep carcasses, with the potential use of these bacterial communities aiding in estimating the post-mortem interval (PMI). One pig (Sus scrofa domesticus) and one sheep (Ovis aries) carcasses were used for this study during the cold season and the study location was Ukulinga Research Farm, University of KwaZulu-Natal, Pietermaritzburg, South Africa. Five stages of decomposition fresh (0-1 d), bloat (2-6 d), active decay (7-12 d), advanced decay (13-51 d) and dry (5258 d) were observed and described for both the pig and sheep carcasses at the same duration from June till August 2019. Temperatures of the carcass and soil (surrounding environment) was recorded. Temperatures of the individual carcasses changed during each stage of decomposition which was influenced by the surrounding environment temperatures. Five bacterial genera (Bacillus, Leclercia, Myroides, Pseudomonas and Providencia) were identified using 16S rRNA gene. During the pig decomposition Myroides and Pseudmonas spp. were absent and Leclercia sp. was absent in the sheep decomposition process. Providencia vermicola was observed during the fresh till the advanced decay of pig decomposition. On a phylum level Proteobacteria was persistent from the fresh till the end of advanced decay stage of the pig carcass, while on the sheep carcass it was persistent till the end of the active stage. Bacillus cereus belonging to the phylum Firmicutes was observed only during the dry stage of the pig decomposition process. During sheep decomposition Providencia sp. were observed during the fresh till the end of active decay stage and Bacillus cereus was observed during the advanced decay and dry stages. Results showed that Proteobacteria was present on both carcasses at the beginning and were absent at the end of decomposition, Firmicutes was present only on the later (advanced decay and dry) stages of decomposition. The presence and absence of different bacterial species during different stages of decomposition on pig and sheep carcasses, indicates their importance in potentially estimating the post mortem interval (PMI), in forensic investigation in KwaZulu- Natal, South Africa. Although this research indicates that bacterial communities can be utilized for PMI estimations, further research is required to better understand the role of bacteria during the decomposition process. This research is especially needed in the different regions of South Africa, as results cannot be extrapolated beyond the countries/regions of study since the bacterial species spectrum vary with geographical regions and conditions.