Haemophilus influenzae erythromycin activity

Clarithromycin has a spectrum of antibacterial activity similar to that of erythromycin, but is also effective against Haemophilus influenzae. Its activity against intracellular pathogens such as Chlamydia. Legionella and Ureaplasma is higher than that of erythromycin (Figure 31.9). 

Azithromycin, though less active against streptococci and staphylococci than erythromycin, is far more active against respiratory infections due to Haemophilus influenzae and Moraxella catarrhalis. Except for its cost, it is now the preferred therapy for urethritis caused by Chlamydia trachomatis. Its activity against Mycobacterium avium intracellulare complex has not proven to be clinically important, except in AIDS patients with disseminated infections. 

Ketolides and macrolides have very similar antibacterial properties. Telithromycin is active against staphylococci, streptococci, S. pneumoniae, Haemophilus spp., Moraxella catarrhalis. Mycoplasma, Chlamydia, and Legionella. It is slightly more active by weight than erythromycin. MIC breakpoints for telithromycin are <0.25 pg/ml for S. aureus, <1 pg/ml for S. pneumoniae, and pg/ml for H. influenzae. 

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