Science & Technology, UK (Commonwealth Union) – Over the years, the misuse and overuse of antimicrobial drugs in human and animal health, as well as in agriculture, have fueled the emergence of resistant strains. Antibiotics, antivirals, antifungals, and antiparasitic drugs are becoming less effective, leaving individuals vulnerable to infections that were once easily treatable. The indiscriminate use of antibiotics, in particular, has accelerated the development of resistant bacteria, creating a global crisis with far-reaching implications. Resistant microbes can travel globally through international travel and trade, making it challenging to contain the spread of resistance. Poor sanitation and hygiene practices can lead to the spread of infections, increasing the need for antimicrobial treatments and, subsequently, the risk of resistance.
A recent study published in The Lancet Microbe reveals a significant expansion of antibiotic resistance gene transfer between diverse bacteria, surpassing previous estimations. Researchers from the Ineos Oxford Institute for Antimicrobial Research (IOI) at Oxford University and Fujian Agriculture and Forestry University in China introduced a novel technique, termed culture-independent conjugation. This method, developed over a five-year span, revolutionizes the assessment of plasmid transmission among bacteria sourced from hospital wastewater.
Plasmids, small circular DNA fragments facilitating gene exchange between adjacent bacteria, play a pivotal role in antimicrobial resistance (AMR). Particularly, plasmids harboring antibiotic resistance genes contribute significantly to AMR, including resistance against carbapenem, a critical “last-resort” antibiotic associated with 50,000 to 100,000 annual global deaths.
Traditionally, conjugation analysis focused on pure bacterial cultures of a single species, limiting the understanding of AMR dissemination within human, animal, and environmental bacterial communities. The innovative culture-independent conjugation technique overcomes this limitation, allowing the evaluation of conjugation in mixed-species bacterial communities, simulating real-world conditions. Unprecedentedly, it models the spread of multidrug-resistant plasmids using non-culture methods, applicable to various aquatic or semi-aquatic samples. Plasmids are labeled with a gene encoding a fluorescent protein, facilitating their tracking and separation through a fluorescence-based sorting method.
The researchers scrutinized a prevalent plasmid, IncX3 (pX3_NDM-5), carrying carbapenem resistance genes (NDM-5), using culture-independent conjugation. Their investigation of wastewater from a Fuzhou, China hospital unveiled the plasmid’s broader host range, transmitting across diverse bacteria, even those challenging to culture. This suggests the potential role of such bacteria as plasmid reservoirs contributing to AMR proliferation.
The study’s implications challenge prior assumptions, debunking the belief that highly antibiotic-resistant Gram-negative bacteria cannot readily exchange resistance genes with Gram-positive bacteria. Furthermore, the research explored the impact of environmental stressors on plasmid transfer, revealing that chlorine, a common hospital disinfectant present in wastewater, can modify plasmid conjugation. This underscores the need to reconsider the use of disinfectants like chlorine in light of escalating AMR concerns. The study underscores the urgency of comprehensive AMR surveillance spanning environments, individuals, and animals.
The co-author Professor Timothy Walsh, who is Director of Biology at the IOI says “We know that overuse and misuse of antibiotics in humans contributes to antimicrobial resistance. This study proves that AMR is being spread in the environment around us, not just hospitals and clinics. People, animals, and ecosystems are interconnected around the world, therefore there is an urgent need to use more creative approaches to understand the dynamics of rising bacterial resistance to our last–resort antibiotics.”
Professor Qiu Yang, of the Fujian Agriculture and Forestry University, Fuzhou, China added “This research can be applied to other plasmids carrying resistance genes – it is very likely plasmids thought to have a narrow host range can in fact be spread between lots of different bacteria. Research exploring the host range of multidrug resistant plasmids is urgently needed to prevent the growing burden of drug-resistance globally.”
The research paper titled “Interphylum Dissemination of NDM-5-Positive Plasmids in Hospital Wastewater from Fuzhou, China: a single-centre, culture-independent, plasmid transmission study ” has been officially published in The Lancet Microbe.
