Preliminary study of graveyard soil as a potential source of AMR - analysis of exhumation soil samples from the New Cemetery in Chełmża, Poland

Abstract

Antimicrobial-resistant microorganisms have been detected in all environments studied so far, wastewater treatment plants, hospitals, agriculture, aquaculture and cemetery soil. However, the latter environment remains poorly explored. In this study, soil samples from the exhumation were collected from the New Cemetery in Chełmża. Samples from 4 research sites and two different depths (1) from the surface (max 10 cm deep) and (2) from under the coffin (1.5-2 m deep) were taken and analyzed for the presence of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs). For this purpose, the number of bacteria colonies resistant to the tested antibiotics: amoxicilline, cefuroxime, doxycycline and oxytetracycline was determined. Colonies grown on a medium with the addition of antibiotic at inhibitory concentration were considered resistant. The soil samples were also examined for the presence of β-lactam (blaSHV, blaOXA, blaCTX-M) and tetracycline (tetA, tetB, tetC, tetD, tetE , tetM) resistance genes. Differences in the number of resistant colonies between samples regarding sampling depth were observed. The highest number of isolates was recorded against cefuroxime and amoxicilline. Moreover, at least one resistance gene was detected in each of the samples and each of the selected genes was detected at least once. The results showed that cemeteries are a source of ARB and ARGs. Due to the possibility of further spread to the environment, i.e. to groundwater and surface waters, they pose a serious threat to human safety. Our results suggest the need for further, more detailed studies to determine the importance of cemeteries in spreading antibiotic resistance.