Community-acquired pneumonia due to gram-negative bacteria and pseudomonas aeruginosa: incidence, risk, and prognosis.
BACKGROUND
Initial empirical antimicrobial treatment of patients with community-acquired pneumonia (CAP) is based on expected microbial patterns. We determined the incidence of, prognosis of, and risk factors for CAP due to gram-negative bacteria (GNB), including Pseudomonas aeruginosa.


METHODS
Consecutive patients with CAP hospitalized in our 1000-bed tertiary care university teaching hospital were studied prospectively. Independent risk factors for CAP due to GNB and for death were identified by means of stepwise logistic regression analysis.


RESULTS
From January 1, 1997, until December 31, 1998, 559 hospitalized patients with CAP were included. Sixty patients (11%) had CAP due to GNB, including P aeruginosa in 39 (65%). Probable aspiration (odds ratio [OR], 2.3; 95% confidence interval [CI], 1.02-5.2; P =.04), previous hospital admission (OR, 3.5; 95% CI, 1.7-7.1; P<.001), previous antimicrobial treatment (OR, 1.9; 95% CI, 1.01-3.7; P =.049), and the presence of pulmonary comorbidity (OR, 2.8; 95% CI, 1.5-5.5; P =.02) were independent predictors of GNB. In a subgroup analysis of P aeruginosa pneumonia, pulmonary comorbidity (OR, 5.8; 95% CI, 2.2-15.3; P<.001) and previous hospital admission (OR, 3.8; 95% CI, 1.8-8.3; P =.02) were predictive. Infection with GNB was independently associated with death (relative risk, 3.4; 95% CI, 1.6-7.4; P =.002).


CONCLUSIONS
In our setting, in every tenth patient with CAP, an etiology due to GNB has to be considered. Patients with probable aspiration, previous hospitalization or antimicrobial treatment, and pulmonary comorbidity are especially prone to GNB. These pathogens are also an independent risk factor for death in patients with CAP.
Hospital Clinic i Provincial, Servei de Pneumologia i Allèrgia Respiratòria, Villarroel, 170, E-08036 Barcelona, Spain. atorres@medicina.ub.es
Francisco
F
Arancibia
Torsten T
TT
Bauer
Santiago
S
Ewig
Josep
J
Mensa
Julia
J
Gonzalez
Michael S
MS
Niederman
Antoni
A
Torres
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002677:Chile / Q000453:epidemiology; D017714:Community-Acquired Infections / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D015897:Comorbidity; D016001:Confidence Intervals; D005260:Female; D016905:Gram-Negative Bacterial Infections / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010359:Patient Readmission; D018410:Pneumonia, Bacterial / Q000175:diagnosis / Q000188:drug therapy / Q000382:microbiology; D011446:Prospective Studies; D011552:Pseudomonas Infections / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification*; D012307:Risk Factors; D013997:Time Factors
D000900:Anti-Bacterial Agents