Study objective: To compare the clinical outcomes
of critically ill patients developing early-onset nosocomial pneumonia
(NP; ie, within 96 h of ICU admission) and
late-onset NP (ie, occurring after 96 h of ICU
Design: Prospective cohort study.
Setting: A medical ICU and a surgical ICU from a
university-affiliated urban teaching hospital.
Patients: Between July 1997 and November 1998, 3,668
patients were prospectively evaluated.
Prospective patient surveillance and data collection.
Results: Four hundred twenty patients (11.5%) developed
NP. Early-onset NP was observed in 235 patients (56.0%), whereas 185
patients (44.0%) developed late-onset NP. Among patients with early
onset NP, 114 patients (48.5%) spent at least 24 h in the
hospital prior to ICU admission, compared to 57 patients (30.8%) with
late-onset NP (p = 0.001). One hundred eighty-three patients (77.9%)
with early-onset NP received antibiotics prior to the development of
NP, as compared to 162 patients (87.6%) with late-onset NP
(p = 0.010). The most common pathogens associated with early-onset NP
were Pseudomonas aeruginosa (25.1%),
oxacillin-sensitive Staphylococcus aureus (OSSA;
17.9%), oxacillin-resistant S aureus (ORSA; 17.9%),
and Enterobacter species (10.2%). P aeruginosa
(38.4%), ORSA (21.1%), Stenotrophomonas maltophilia
(11.4%), OSSA (10.8%), and Enterobacter species (10.3%) were the
most common pathogens associated with late-onset NP. The ICU length of
stay was significantly longer for patients with early-onset NP
(10.3 ± 8.3 days; p < 0.001) and late-onset NP (21.0 ± 13.7
days; p < 0.001), as compared to patients without NP (3.5 ± 3.2
days). Hospital mortality was significantly greater for patients with
early-onset NP (37.9%; p = 0.001) and late-onset NP (41.1%;
p = 0.001) compared to patients without NP (13.1%).
Conclusions: Both early-onset and late-onset NP are
associated with increased hospital mortality rates and prolonged
lengths of stay. The pathogens associated with NP were similar for both
groups. This may be due, in part, to the prior hospitalization and use
of antibiotics in many patients developing early-onset NP. These data
suggest that P aeruginosa and ORSA can be important
pathogens associated with early-onset NP in the ICU setting.
Additionally, clinicians should be aware of the common microorganisms
associated with both early-onset NP and late-onset NP in their
hospitals in order to avoid the administration of inadequate