Antibiotic resistance gene is rapidly transferred to competent microbial pathogens and making them resistant to existing antibiotics. Therefore, medical science requires a large number of different antibiotics to treat the patient. In addition to mutation, the horizontal gene transfer (HGT) process plays a significant role in undermining antibiotic effectiveness through the acquisition of antibiotic resistance genes against existing antibiotics. Antibiotics and their metabolites are persistent in environmental compartments and responsible for the selection of antibiotic-resistant microorganisms in nature.
Environmental fate of antibiotics
A large number of antibiotics have been detected in environmental compartments and degraded slowly. Abiotic degradation of antibiotics is insignificant and negligible. However, biodegradation plays a major role in mineralization and reduces the persistence of antibiotics in the environment. The rate and extent of biodegradation of antibiotics depend on the structure of antibiotics and the types of microorganisms. In addition, temperature, oxygen availability, pH, and nutrient availability play an important role to regulate the extent of degradation.
The widespread use of antibiotics and their continuous release into the environmental compartments can development of antibiotic resistance through HGT or mutation. Therefore, it is crucial to implement responsible antibiotic use practices, and proper disposal methods to minimize the environmental impact of antibiotics.
Acquisition of antibiotic resistance genes
Horizontal gene transfer (HGT) is the transfer of genetic material between different competent organisms that are not direct offspring. It plays an important role in the spread of antibiotic-resistance genes among bacteria even across species or genera. HGT can reduce antibiotic effectiveness through the acquisition of antibiotic-resistance genes. These resistance genes encode enzymes that break down antibiotics and modify efflux pumps or antibiotic targets. When bacteria acquire these genes, they become resistant to the specific antibiotics targeted by those genes. In addition, HGT facilitates aggregation of resistance plasmid through conjugation, or transduction and transformation. As a result, bacteria that were previously sensitive to antibiotics become resistant.
HGT can also lead to the co-selection of resistance genes. This occurs when genes for antibiotic resistance are located on the same plasmid as other genes that confer a selective advantage. For example genes for heavy metal resistance or virulence factors. The use of antibiotics may inadvertently select for these co-located resistance genes, further reducing antibiotic effectiveness.
Overall, HGT plays an important role in the spread of antibiotic resistance by enabling the transfer of resistance genes between bacteria. This process reduces antibiotic effectiveness by conferring resistance to bacteria that were previously susceptible, reducing the effectiveness of antibiotics in treating infections and contributing to the emergence of multidrug-resistant bacterial strains.
Environmental factors affecting antibiotic effectiveness
Environmental factors affect HGT through the induction of stress response by exposure to environmental stresses, such as antibiotics, heavy metals, UV radiation, or temperature fluctuations. These stress responses can increase the rates of HGT. For example, antibiotics induce the expression of stress-related genes in bacteria, which may include genes involved in DNA absorption and recombination, thereby promoting HGT.
The formation of biofilms provides a suitable environment for cell aggregation, increasing the likelihood of contact and subsequent HGT. It can be noted that biofilm formation is highly regulated by environmental factors.
Environmental conditions can modulate gene expression, modify DNA stability and affect the physiology and metabolism of bacteria, which, in turn, affect HGT. For example, nutrient deprivation or starvation can trigger changes in gene expression in HGT. Bacteria under nutrient-poor conditions can increase the expression of genes related to DNA uptake and recombination, potentially promoting HGT.
In addition, environmental factors can shape the composition and dynamics of microbial communities, which, in turn, can affect HGT. The presence of specific bacterial species or the composition of microbial communities may affect HGT to potential recipients. Interactions between different bacterial species within a community can facilitate or inhibit the transfer of genetic material.
Conclusion
The undermining of antibiotic effectiveness has a direct correlation with increasing HGT which is regulated by environmental factors. The effect of environmental factors on antibiotics may vary depending on the specific mechanisms involved and the characteristics of the bacterial species or strains. Understanding the interplay between environmental factors and HGT may provide insight into the spread of antibiotic resistance genes in natural environments.
