A kind of method and a kind of composition are used to treat bacterium infection caused by lung Gram-negative bacteria and are suitable for handling the Escherichia coli for causing infection, Friedlanders bacillus, Klebsiella oxytoca, pseudomonas aeruginosa, haemophilus influenzae, proteus mirabilis, Enterobacter species, serratia marcescens and those by Burkholderia cepacia, Stenotrophomonas category monad, Alcaligenes xylose, multi-resistant Pseudomonas aeruginosa, use concentrate formulation aztreonam, or its pharmaceutically acceptable salt, wherein aztreonam of the preparation without arginine or arginine salt, conveying is used as aerosol or dry powder formulations.
