MED-NERD
The environment plays an important role in developing bacterial resistance and this is known as ‘transmission event’. Evolution events mean change in DNA sequence of pathogens and their transmission across bacterial species. Evolution events lead to emergence of of new genetic sequences and therefore successful resistance in pathogens. Evolutionary events are not limited compared to environmental transmission.
Environmental transmission are common in low- and middle income countries due to handling faecal waste and improper hygiene. Infection can also result from contact with surface waters contaminated with faecal waste and through contaminated surfaces not only in hospitals. Levels of faecal indicator bacteria are used in the European Union as surrogate exposure thresholds.
It was suggested that the overall sanitation and waste infrastructure can be used as an indicator and predictor of national burdens of resistance.
The role of environmental contribution to colonization or infection with specific resistant bacteria has been proven by few studies. It was found through faecal swabs from that Britain surfers that are more likely to ingest seawater, are more prone to carry cephalosporin-resistant E. coli. Another study found that the risk of urinary tract infections with extended-spectrum β-lactamase-producing E. coli or Klebsiella pneumoniae is increased for recreational swimming. More studies are required to ensure the role of environmental transmission in developing and spread of resistance. Raw vegetables are also possible exposure methods.
Studies have shown that fresh produce may carry various resistant bacteria with diverse mobile elements resulting in infection with different pathogens such as enterohaemorrhagic E. coli, Salmonella spp., and Campylobacter jejuni.
Safe use of human and animal faecal matter on farmland is indicated to control resistance evolution.
Antibiotic resistance evolution in the environment:
The mechanism through which antibiotic resistance can emerge include the uptake of foreign DNA and mutations in the pre-existing genome of the organism.
When animals or patients become treated with antibiotics, mutations can occur easily and become fixed in the affected patient. The effect of external environment is less important in emergence of antibiotic resistance through mutations and the genetic reservoir does not affect the process. The external environment can provide various genes that could be acquired by pathogens to develop resistance against antibiotics which is a prominent feature. All available antibiotics were found to be not effective in at least one of the targeted pathogens which may be due to the resistance factors that are already existed in the external environment.
Pollution as a factor in emergence of antibiotic resistance:
Antibiotics produced by environmental microorganisms act on microscale and limit the exposure through dropping around the producing microorganism. However, man-made antibiotics act on a macroscale and associated with selection pressures across microbial communities.
Excretions from humans or domestic animals including urine and faeces can be methods of transferring antibiotics to the environment through improper disposal, direct contamination, plant production, waste streams from production of antibiotics, and handling unused drugs. Most antibiotics are released due to the use and excretion.
Bacterial excretion through faeces causes environmental contamination affecting human through physical contact which allows exchange of genes between environmental bacteria and intestinal bacteria of humans or animals. Bacteria can act as carriers of genetic elements such as integrons, transposons, plasmids, insertion sequences, and integrative conjugative elements. The genetic carriers facilitate gene transference to pathogens.
Adding fluorescence labeled E. coli to soils results in rapid development of resistance from the soil microbiota which was proven by experiments.
See: Zika Virus
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8567979/
Reference:
Larsson DGJ, Flach CF. Antibiotic resistance in the environment. Nat Rev Microbiol. 2022 May;20(5):257-269.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8567979/
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