A pathogen considered to be a cause of hospital infection is widespread in Vietnam, turning up in farm soil and pig faeces as well as hospital beds and toilet floor surfaces, with 70% of isolates found to be resistant to at least one class of antimicrobials.

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Source: CDC/ Antibiotic Resistance Coordination and Strategy Unit

Medical illustration of Clostridioides difficile bacteria, formerly known as Clostridium difficile

A study by a group of scientists from The University of Western Australia and Vietnam, ‘Environmental contamination with Clostridioides (Clostridium) difficile in Vietnam’ warns that there is significant contamination of the environment in general with Clostridioides difficile spores. The paper has been accepted for publication by the Journal of Applied Microbiology, an Applied Microbiology International publication.

Hospital-only infection

C. difficile infection has been considered a hospital-only problem in high-income countries for most of the last 45 years, corresponding author Professor Thomas Riley explained.

“More recently though, community-associated cases of CDI have been increasing, suggesting sources or reservoirs of C. difficile outside the hospital environment. The spotlight has fallen mainly on food animals - however, the inciting agents are still antimicrobials being used in agriculture,” he said.

“The US CDC now considers C. difficile an urgent antimicrobial resistance threat in the USA. CDI should be thought of as a zoonosis, and a ‘One Health’ approach is required to deal with this problem.

Continental clades

“With the rise of whole genome sequencing, we are learning that there are different phylogenetic clades of C. difficile circulating in the world and that these clades differ in various continents.“

“Very little is known about C. difficile and CDI outside high-income countries, and my group has been particularly interested in Asia, given its proximity to Australia. Thus, over the last several years, we have been investigating C. difficile and CDI in Asian countries where misuse of antimicrobials in both humans and animals is still a major problem.”

Antimicrobial exposure

Vietnam is a developing country where there is limited knowledge of CDI, no specialist anaerobe diagnostic laboratory and poor antimicrobial regulation, and the main risk factor for CDI remains antimicrobial exposure, Professor Riley said.

“Furthermore, C. difficile is a spore-forming bacterium and spores are commonly found in healthcare facilities, animal manure and on vegetables grown in contaminated soil,” he said.

“Due to a lack of C. difficile data in Vietnam, the study was designed to investigate the presence of C. difficile in Vietnamese communities and healthcare facilities. These findings might provide a lesson for other low- and middle-income countries in Asia.”

Variety of samples

Samples were collected from a variety of healthcare facilities, potato surfaces and pigs, while soil samples were collected from both hospital grounds and piggeries. Nearly a quarter (24.5%) of 278 samples, mainly soils, contained C. difficile and ~6% of isolates were toxigenic.

Toxigenic C. difficile strains were more common from hospital samples, such as soil from gardens, hospital beds and toilet floors. Overall, 53 different strains of C. difficile (or ribotypes) were identified.

Toxigenic strain

“Interestingly, the toxigenic strain C. difficile ribotype 001 was detected in pig stool, soils from pig farms, hospital beds and toilet floor surfaces, showing how widespread it was. This strain has been reported frequently as a cause of human CDI in many parts of the world,” Professor Riley said.

“Of the 120 C. difficile isolates, about 70% were resistant to at least one class of antimicrobials, and almost 30% were multidrug-resistant i.e. resistant to more than three classes of antimicrobial. Six isolates (5%) were resistant to four classes of antimicrobials, macrolides, tetracyclines, fluoroquinolones and/or rifamycins.

“What this means is that there is significant contamination of the environment in general with C. difficile spores, not just healthcare facilities.

Infection prevention measures

“Effective infection prevention and control measures in hospitals can work to reduce hospital-acquired CDI. C. difficile spores cannot be eliminated with the usual disinfectants, particularly those that are alcohol based - however, bleach can effectively kill spores. Furthermore, effective hand hygiene with soap is also important to reduce the transmission.”

Pig faeces and soils from piggeries are used as organic compost in soil to grow vegetables in many countries, and various root or tuber vegetables such as potatoes become contaminated, Professor Riley said.

Major problem

“Based on this and some of our earlier Asian studies, the prevalence of CDI in Vietnam and other low- to medium-income countries in Asia is high. A lack of knowledge about C. difficile among Asian physicians and poor antimicrobial regulation may be contributory factors, and antimicrobial resistance is becoming a major problem,” he said.

“In the future, surveillance – the cornerstone of public health - will play an important role in understanding C. difficile circulation in Asia. Whole genome sequencing can be used to investigate pathways of transmission of C. difficile from the environment or animals to humans under a ‘One Health’ umbrella.

Role of government

“In addition, the government has a role to play in paying more attention to effective infection prevention and control in healthcare, regulation of antimicrobial use in health and agriculture, and disseminating knowledge of C. difficile to physicians and relevant members of the community. Importantly, governments should invest more into diagnostic microbiology laboratories.”

The lead author of this study, Dr Peng An Khun, was funded by a Scholarship for International Research Fees awarded by The University of Western Australia.

Dr Deirdre Collins was the recipient of a National Health and Medical Research Council Early Career Fellowship. This project was undertaken during the COVID pandemic.

“We had fantastic help from our Vietnamese co-authors listed on the title page of the manuscript and support from many Vietnamese collaborators listed in the Acknowledgements section,” said Professor Riley, who was the senior author and overall project supervisor.

‘Environmental contamination with Clostridioides (Clostridiumdifficile in Vietnam’ is published in the Journal of Applied Microbiology.