Ceftriaxone is indicated for the treatment of the following major infections when caused by susceptible organisms: Lower respiratory tract infections: caused by Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Haemophilus parainfluenzae, Klebsiella pneumoniae, E. coli, Enterobacter aerogenes, Proteus mirabilis, Serratia marcescens.