Determination of the relative abundance of antibiotic resistant bacteria in sediments of the King George Island, Antarctica

MSc. Gastón Azziz, Instituto de Investigaciones Biológicas Clemente Estable (IIBCE)

Antibiotic resistance of pathogenic bacteria is a serious and emerging public health problem worldwide. Antibiotics are natural or synthetic compounds whose therapeutic use prevents or cures infections of bacterial origin. Its loss of efficiency due to the emergence of resistant bacteria puts this therapeutic option in check, which may mean that in the near future we are unable to treat infections that are currently curable with these drugs.

Bacteria have various mechanisms to cope with changes in the environment. Their rate of mutation and the number of generations of bacteria that can reproduce in a short time determines that resistant variants can arise with relative ease (compared to animals and plants, for example). In addition, bacteria can share genes between them, which is known as horizontal gene transfer. This phenomenon, unique to the prokaryotic world (archaea and bacteria), can occur even among bacteria of different species, which means that genes of a bacteria innocuous for humans can end up being part of the genome of pathogenic bacteria.

In spite of all this, the rate at which antibiotic resistant variants arise following the inclusion of a drug as a therapeutic agent is too high to be explained only by the mechanisms of mutation and horizontal gene transfer. Recently, the presence of antibiotic resistance determining genes (GDRA) in non-clinical settings has been studied. The results have shown that there is a reservoir of genes with potential to be transmitted to pathogenic bacteria. Some of these genes confer resistance to antibiotics found in nature, but surprisingly others confer resistance to synthetic antibiotics without a natural counterpart.

The objective of this project is to determine the abundance of resistant bacteria to four classes of antibiotics in sediments of King George Island. Taking advantage of the human presence in some areas of the island, as well as the dynamics of its birds, we sampled three zones with dissimilar characteristics in terms of human influence: (i) area near the septic chamber of the base; (Ii) zone without human presence but with presence of avifauna (Ardley Island), this zone allows us to evaluate the dispersing potential of the human influence of the birds; (Iii) zone without human presence or of bird fauna (Halftree Point) we consider this zone as the one of less human impact and without potential of dissemination of this impact by the birds.

As a result of previous studies, we have obtained a collection of antibiotic resistant bacteria which is preserved in the Institute of Biological Investigations Clemente Estable. These bacteria, isolated from sediments of King George Island, will allow us to search in their genomes the presence of different GDRAs. To determine the presence of these genes in bacteria isolated from a site with low human impact, such as King George Island, allows to gather information about the natural reservoirs of these genes and their link with the emergence of resistant variants in clinical settings. These aspects of the ecology of DGRAs have been poorly explored and may be of vital importance in assessing the propensity of pathogenic bacteria to acquire resistance to different antibiotics.