Table 2.

Nosocomial pneumonia (NP; excluding patients with immunosuppression): spectrum of common pathogens. MRSA methicillin-resistant Staphylococcus aureus. (Modified from [14])

Early onset mild to moderate NP; enteric gram-negative bacilli	Onset, any time, mild to moderate NP; enteric gram-negative bacilli	Late-onset severe NP; enteric gram-negative bacilli
Enterobactericeae species	Enterobactericeae species	Enterobactericeae species
Escherichia coli	Escherichia coli	Escherichia coli
Klebsiella species	Klebsiella species	Klebsiella species
Proteus species	Proteus species	Proteus species
Serratia marrescens	Serratia marcescens	Serratia marcescens
Haemophilus influenzae	Haemophilus influenzae	Haemophilus influenzae
Staphylococcus aureus	Staphylococcus aureus	Staphylococcus aureus
Streptococcus pneumoniae	Streptococcus Pneumoniae	Streptococcus Pneumoniae
	Plus	Plus
	Anaerobesa	Pseudomonas aeruginosa
	Staphylococcus aureus b	Acinetobacter species
	Legionella speciesc	Consider MRSA
	Pseudomonas aeruginosa d

^aRecent abdominal surgery, witnessed aspiration

^bComa, head trauma, diabetes mellitus, and renal failure

^cHigh-dose steroids

^dProlonged ICU stay, steroids, antibiotics, and structural lung disease