Antibiotic resistant bacteria in terrestrial and aquatic environments: A review

Abstract

Antibiotic resistant bacteria have become increasingly widespread in environment and their prevalence is a serious problem for health. The rise and spread of this resistance is primarily due to overuse of antibiotics in clinical therapeutics and as growth promoters for livestock. Overuse undermines the usefulness of antibiotics by giving a selective advantage to microbes that are resistant. The problem has been exacerbated by the emergence of bacteria that are resistant to multiple antibiotics, and by the ability of these resistance determinants to spread horizontally between different bacteria via horizontal gene transfer. Such transfer can, for example, take place in the guts of farm animals, which can become reservoirs of multiple antibiotic resistant bacteria (MARB). Antibiotics and MARB enter the environment via wastewater, especially from hospitals and pharmaceutical plants, and through agricultural runoff, leading to contamination of surface and ground water. This is a serious problem in arid regions such as Oman where wastewater is recycled for irrigation and recharging aquifers. Even treatment with chlorine does not completely remove bacteria from wastewater or prevent their re-growth in downstream distribution systems. MARB can reach humans via contaminated food and drinking water, or directly from the environment. Agricultural runoff and sewage, either treated or untreated, are also the main sources of antibiotic resistant bacteria in coastal sea water. It is necessary to use antibiotics more prudently in medicine, treat wastewater more effectively, eliminate the discharge of untreated waste into the environment, and curtail the profligate use of antibiotics as growth promoters for livestock.