Antibacterial resistance Flashcards
The genetic mechanisms by which bacteria develop resistance
Mutation: Mutations can occur spontaneously in bacterial genes, including those that encode for the target of the antibiotic. A mutation may alter the target so that the antibiotic can no longer bind to it, or it may change the structure of the bacterial cell wall, making it less permeable to the antibiotic.
Horizontal gene transfer: Bacteria can acquire resistance genes from other bacteria through horizontal gene transfer. This can occur through several mechanisms, including:
Transformation: Bacteria can take up DNA from their environment, which may include resistance genes.
Conjugation: Bacteria can transfer resistance genes directly to another bacterium through a pilus or bridge-like structure.
Transduction: Bacteria can acquire resistance genes from a virus that has infected another bacterium.
Antibiotic modification: Some bacteria can modify or inactivate antibiotics before they can have an effect. For example, some bacteria produce enzymes that break down beta-lactam antibiotics like penicillin.
Explain horizontal gene transfer
Transformation: In transformation, a cell takes up free DNA from its environment and incorporates it into its own genome.
Transduction: In transduction, genes are transferred between cells by a bacteriophage, a virus that infects bacteria.
Conjugation: In conjugation, genetic material is transferred between cells through direct physical contact. This is commonly seen in bacteria, where a donor cell transfers DNA to a recipient cell through a tube-like structure called a pilus.
The cellular mechanisms for antibacterial resistance
Mutation: Bacteria can acquire mutations that enable them to resist the effects of antibiotics. These mutations can occur spontaneously, and if they provide a selective advantage in the presence of antibiotics, they can be passed on to future generations.
Antibiotic degradation: Some bacteria produce enzymes that can break down antibiotics, rendering them ineffective. For example, beta-lactamase enzymes can break down penicillin and related antibiotics.
Efflux pumps: Bacteria can use efflux pumps to pump antibiotics out of their cells before the antibiotics can have an effect. This is a common mechanism of resistance in gram-negative bacteria.
Target modification: Antibiotics target specific bacterial structures or metabolic pathways, and bacteria can develop mutations that alter these targets, making them less susceptible to the effects of antibiotics. For example, some bacteria can modify their ribosomes to prevent antibiotics from binding to them.
Biofilm formation: Bacteria can form biofilms, which are communities of cells encased in a protective matrix. Biofilms can provide a physical barrier that antibiotics have difficulty penetrating, as well as providing an environment that is less conducive to the effects of antibiotics.
The potential clinical impact of antimicrobial resistance for individual patients
Reduced effectiveness of treatment: Antimicrobial resistance can result in the failure of antibiotic treatment for bacterial infections. This means that the infection may persist or worsen, leading to more severe illness, prolonged hospitalization, and increased risk of complications and death.
Increased morbidity and mortality: Patients with antimicrobial-resistant infections are more likely to experience severe illness, longer hospital stays, and higher mortality rates compared to patients with infections caused by antibiotic-susceptible bacteria.
Increased healthcare costs: Patients with antimicrobial-resistant infections may require longer hospital stays, more intensive care, and more expensive treatments, which can increase healthcare costs for both the patient and the healthcare system as a whole.
Limitations on treatment options: As antimicrobial resistance continues to increase, fewer effective treatment options are available for patients with bacterial infections. This can lead to the use of older, less effective antibiotics, which can increase the risk of adverse effects and further contribute to the development of antibiotic resistance.
Spread of resistant infections: Patients with antimicrobial-resistant infections can spread these infections to others, including healthcare workers and other patients in healthcare settings. This can increase the overall burden of antimicrobial resistance and make it more difficult to control and prevent the spread of resistant infections.
