Erythromycin and azithromycin are macrolide antibiotics. They bind to the 50S ribosomal subunit of susceptible bacteria, preventing translocation during protein synthesis. This blockage halts bacterial growth and ultimately leads to bacterial death.
Erythromycin’s Spectrum
Erythromycin’s activity covers Gram-positive bacteria like Streptococcus pneumoniae, Staphylococcus aureus (penicillinase-sensitive strains), and Corynebacterium diphtheriae. It also targets some Gram-negative bacteria, including Haemophilus influenzae and Legionella pneumophila, as well as atypical bacteria such as Mycoplasma pneumoniae and Chlamydia trachomatis.
Azithromycin’s Spectrum
Azithromycin shares a similar spectrum to erythromycin, demonstrating good activity against Gram-positive cocci and some Gram-negative organisms. However, azithromycin often exhibits superior intracellular penetration, making it particularly effective against intracellular pathogens like Chlamydia and Mycoplasma species. It also shows activity against Helicobacter pylori.
Remember that bacterial resistance to macrolides is a growing concern. Antibiotic susceptibility testing is vital for optimal treatment choices.
