Gram Negative Aerobes Citrobacter diversus Citrobacter freundii Enterobacter aerogenes Enterobacter cloacae* Haemophilus influenzae* Escherichia coli Klebsiella pneumoniae* Klebsiella oxytoca Morganella morganii Proteus mirabilis* Proteus vulgaris Providencia rettgeri Providencia stuartii Salmonella species Serratia marcescens Shigella species