Prevalence and Recovery of Microorganisms from Containers used for the Collection of Forensic Biological Samples

Abstract

Background: Microbes play a significant role in the degradation of biological evidence collected for forensic analysis. The present study is aimed to isolate and identify the microbes present inside the empty container used for the biological evidence collection. Methods: Bacterial isolation from the selected containers was done by cotton swab over the inner surface of the containers. Streaking was done on the surface of the three different culture plates as a Blood agar plate, Nutrient plate and MacConkey plate. The plates were placed in an incubator shaker at 37ºC for 48 hours. The colonies grown on the surface of the media were counted on and used for further study. Various biochemical assays were performed to characterize isolated bacteria. Results: Staining results suggested that the presence of Gram-positive stain (Staphylococcus, Bacillus, Corynebacterium, Clostridium) and Gram negative stain (E. coli, Enterobacteriaceae, Pseudomonas, Salmonella, Shigella, Stenotrophomonas, Bdellovibrio, Acetic acid bacteria). The Catalase and Coagulase test suggested the presence of Staphylococcus aureus, S. epidermis and S. sapropyticus. Moreover, the indole test suggested the presence of Citrobacter koseri, Kebsiella oxytoca, Proteus vulgaris etc. Some of the bacteria were urea metabolizing, including Proteus spp, Helicobacter pylori, Cryptococcus spp, Corynebacterium spp. Conclusion: This study recommends that there should be proper maintenance of the chain of custody from the collection to analysis so that evidence properly prevents degradation or contamination in the biological evidence. Extra care is needed for the collection and packing of biological evidence from the crime scene. Moreover, the collection containers, if left wide open, lead to contamination and degradation of biological evidence.