ANTIBIOTICS ARE considered one of the most important advances in medicine. Yet bacterial resistance to antibiotics has become a serious problem due to their extensive and often indiscriminate use in hospitals, veterinary clinics and agriculture.
Studies have documented antibiotic resistance mechanisms in micro-organisms isolated from natural habitats, where human influence is minimal or non-existent. These environments include deep underground layers and the ocean floor, as well as ancient environments such as isolated caves.
Many of the resistance mechanisms described in these untouched environments are similar or even identical to those observed in present-day pathogenic bacteria. This suggests that the conservation and transmission of resistance mechanisms throughout evolution provides a selective advantage.
The resistance genes found in permafrost samples from 30,000 years ago bear a strong resemblance to those found today. These strains were as resistant as more modern ones that have been observed to resist β-lactam antibiotics, tetracyclines and vancomycin.
Staphylococcus strains resistant to aminoglycosides and β-lactams have also been isolated from 3.5 million-year old permafrost samples. Research has revealed that competition for resources and adaptation to different habitats were key factors in the evolution of antibiotic resistance.
In pre-drug environments, natural antibiotics not only played an ecological role in inhibiting the growth of competitors, but also supported the survival of producer species. In addition, very small amounts of antibiotics influenced the interactions and balance of microbial communities.
But the presence of these mechanisms in isolated, pre-antibiotic-era environments raise questions about how resistance has originated and spread throughout microbial evolution. It is suggested that antibiotic resistance genes may have been transmitted first from environmental microorganisms to human commensal organisms, and then to pathogens. This process of transfer from the environment to the human environment is random. The more prevalent a resistance mechanism is in the environment, the more likely it is to be transferred.
Reservoirs of resistance in the environment can accelerate bacterial evolution towards multiple drug resistance under antibiotic pressure. It is therefore necessary to consider the diversity of these resistance genes within microbial populations when developing or implementing new strategies to combat antibiotic resistance.
Researching ancestral resistance not only provides information on the evolutionary history of resistance genes, it can also help us predict how they will evolve in the future. By Manny Palomar, PhD (EV Mail AUGUST 11-17, 2025 Issue)
