Question

Describe one mechanism of bacterial resistance to the following antibiotics:

a) penicillin

b) rifampin

Answer 1

Mechanism of bacterial resistance to  penicillin

• Hydrolysis of penicillin antibiotic by the bacteria is the most common mechanism of resistance
• Hydrolysis of penicillin is mediated by the enzyme beta-lactamase.
• Beta-lactamase gene may be present in the chromosome or plasmid
• Beta-lactamase gene can be induced by the exposure of beta-lactam drugs.
• Penicillinase encoded by extended spectrum β-Lactamase” ( plasmid-encoded ESBL) also can hydrolyze penicillins

Mechanism of bacterial resistance to  rifampin

• Rifampin inhibit the DNA depandant RNA polymerase activity in bacterial cells
• The main mechanism of resistance to Rifampin by bacteria is by mutations of the rpoB (RNA polymerase B) gene
• Eg. in E.coli, mutation occur at the amino acid residue 516 (aspartic acid to valine) of the rpoB polypeptide
• In Mycobacterium the mutation occur at residue 531 (Serine to Leucine) of the rpoB polypeptide
• These mutations make the RNA polymerase insensitive to rifampin and bacteria survives