Acquired resistance

1. Acquired Resistance

Acquired resistance refers to the ability of microorganisms, such as bacteria, viruses, fungi, and parasites, to develop resistance to antimicrobial agents that were previously effective in treating infections caused by these organisms. This phenomenon poses a significant challenge in the treatment of infectious diseases and is a major concern in the field of public health.

Mechanisms of Acquired Resistance

Microorganisms can acquire resistance through several mechanisms:

Genetic Mutation

Spontaneous mutations in the microbial genome can lead to changes in the target site of the antimicrobial agent, reducing its efficacy. These mutations can occur naturally and may confer a survival advantage in the presence of the drug.

Horizontal Gene Transfer

Microorganisms can acquire resistance genes from other organisms through horizontal gene transfer. This can occur via:

• **Transformation**: Uptake of free DNA from the environment.
• **Transduction**: Transfer of DNA by bacteriophages.
• **Conjugation**: Transfer of DNA through direct contact between cells, often mediated by plasmids.

Efflux Pumps

Some microorganisms develop efflux pumps that actively expel antimicrobial agents from the cell, reducing their intracellular concentration and effectiveness.

Enzymatic Degradation

Microorganisms can produce enzymes that inactivate antimicrobial agents. For example, beta-lactamase enzymes can hydrolyze beta-lactam antibiotics, rendering them ineffective.

Clinical Implications

Acquired resistance can lead to treatment failures, prolonged illness, increased healthcare costs, and higher mortality rates. It necessitates the use of alternative, often more expensive or toxic, antimicrobial agents. The spread of resistant strains can lead to outbreaks of difficult-to-treat infections.

Strategies to Combat Acquired Resistance

Efforts to combat acquired resistance include:

• **Antimicrobial Stewardship**: Rational use of antibiotics to minimize the development of resistance.
• **Infection Control Measures**: Preventing the spread of resistant organisms in healthcare settings.
• **Research and Development**: Developing new antimicrobial agents and alternative therapies.
• **Surveillance**: Monitoring resistance patterns to inform treatment guidelines.

Also see

• Antimicrobial resistance
• Horizontal gene transfer
• Public health
• Infection control