Neomycin, an aminoglycoside with spectrum similar to gentamicin, binds to the 30S subunits of the bacterial ribosome, inhibiting protein synthesis and thereby disrupting DNA synthesis. It is active against many Gram-negative aerobes and some strains of staphylococci. Polymyxin B disrupts bacterial cell membrane and has bactericidal action against most Gram-negative bacilli. It is inactive against Gram-positive bacteria, obligate anaerobes and Neisseria spp. When used together, they are active against Staphylococcus aureus, Escherichia coli, Haemophilus influenzae, Klebsiella-Enterobacter species, Neisseria species, and Pseudomonas aeruginosa but have inadequate coverage against Serratia marcescens and streptococci, including Streptococcus pneumoniae. Hydrocortisone, a corticosteroid with mainly glucocorticoid...