Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2017

Antimicrobial susceptibility of Clostridium difficile from diverse environmental sources (#140)

Su Chen Lim 1 , Grace O Androga 1 , Daniel R Knight 1 , Niki F Foster 2 , Thomas V Riley 1 3 4 5
  1. School of Biomedical Science, The University of Western Australia, Perth, WA, Australia
  2. OzFoodNet, Communicable Disease Control Directorate, Department of Health, Perth, WA, Australia
  3. PathWest Laboratory Medicine, Perth, WA, Australia
  4. Edith Cowan University, Perth, WA, Australia
  5. Murdoch University, Perth, WA, Australia

Background: Clostridium difficile is an established cause of healthcare-associated diarrhea in humans. Over the past decade, the incidence of community-acquired C. difficile infection (CA-CDI) has increased. Molecular studies show possible long-distance transmission of C. difficile from production animals to humans in the community. Our recent studies have found a high prevalence of C. difficile in retail foods, compost and lawn; many of the ribotypes isolated are common among food animals and humans. The objective of this study was to determine the antimicrobial resistance profile of these C. difficile isolates. Our hypothesis was that any overlap in antimicrobial phenotype would provide insight into the transmission of CA-CDI.

Methods: A total of 274 C. difficile isolates from food (n= 56), compost (n= 36) and lawn (n= 182), collected in Western Australia from 2015 to 2016, were tested against 10 antimicrobial agents using an agar incorporation method.

Results: Overall 44.2% (121 of 274) of isolates showed resistance to at least one antimicrobial agent. Multidrug resistance was observed in 4.1% (5 of 121) of resistant isolates, with 22.2% (4 of 18) of compost resistant isolates and less than 1.0% (1 of 103) of lawn resistant isolates being multidrug resistant. Compost isolates had a significantly higher prevalence of resistance to clindamycin, erythromycin and tetracycline (P<0.05) compared to lawn and/or food isolates. While resistance to clindamycin (42.3%) in lawn isolates was similar to compost isolates, it was significantly higher than the food isolates.

Conclusions: The high antimicrobial resistance rate among compost isolates is likely due to the widespread use of antimicrobials in the food animal industry. It is common practice in Australia to compost animal manure to use as fertiliser for gardening and landscaping, including turf/lawn farming. This study suggests that food, compost and lawn might be playing an intermediary role in the transmission C. difficile from animals to humans, supporting studies that show long range interspecies transmission.