Understanding Bacterial Resistance to Antibiotics

Sub: Sci

Sec: Health

Why in News

Antimicrobial resistance has emerged as a major global health concern due to the overuse of antibiotics. In 2021, around 1.2 million deaths worldwide were attributed to antibiotic resistance. In India, hospital surveys indicate that infections caused by drug-resistant bacteria have a mortality rate of 13%.

Antibiotics function:

They are used to kill bacteria or inhibit their growth without harming human cells. Antibiotics target unique bacterial structures or processes essential for survival.

Bacterial Cell Wall:

Unlike human cells, bacterial cells have a peptidoglycan cell wall, providing structural integrity.
Peptidoglycan Structure: Composed of alternating sugar molecules NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid).
The NAM-NAG chains are linked by peptides, forming a strong mesh-like structure.
Antibiotic Action: The first antibiotic, penicillin, targets the crosslinking step in peptidoglycan synthesis.
Weakening of the bacterial cell wall causes bacterial lysis and death.

Mechanisms of Antibiotic Resistance:

Bacteria have evolved multiple strategies to counteract antibiotics:
- Bacteria produce enzymes like penicillinase, which break down penicillin.
- Bacteria alter their cell wall components, reducing antibiotic effectiveness.
- Some bacteria develop pumps that expel antibiotics from the cell before they take effect.
- Bacteria can form protective biofilms, making them more resistant to antibiotics.

Bacterial Cell Division:

Bacterial growth requires constant cell wall synthesis.
Enzymes called endopeptidases break peptide crosslinks, while lytic transglycosylases (LTs) cut sugar chains.
These processes must be precisely coordinated for successful bacterial division.
Disrupting these mechanisms can offer new avenues for antibiotic development.

Recent Research:

Researchers at CCMB Hyderabad, have discovered that bacteria compensate for the loss of crosslink-cutting enzymes by producing excess LT scissors.
These findings help in understanding bacterial survival mechanisms and developing innovative treatments.
Future strategies may focus on:
- Inhibiting bacterial adaptation mechanisms.
- Developing novel antibiotics targeting newly discovered bacterial enzymes.
- Exploring alternative treatments such as bacteriophage therapy and antimicrobial peptides.

Biofilms:

Biofilms are structured communities of microorganisms that adhere to surfaces and are encased within a self-produced matrix of extracellular polymeric substances (EPS), primarily composed of polysaccharides, proteins, and nucleic acids.
Formation Process:
- Microorganisms first adhere to a surface.
- The initial colonizers proliferate, forming microcolonies.
- The biofilm matures into a complex, three-dimensional structure.
- Cells or clusters detach to colonize new areas.

Biofilms exhibit increased resistance to antibiotics and disinfectants, posing challenges in medical treatments.
The EPS matrix shields the microorganisms from environmental threats, including the host’s immune system.
Biofilms can form on various surfaces, both biotic and abiotic, such as medical devices, natural water systems, and human tissues.
Biofilms are implicated in chronic infections due to their resilience against standard antimicrobial therapies.