New strains of bacteria and exacerbations of chronic obstructive pulmonary disease.
BACKGROUND
The role of bacterial pathogens in acute exacerbations of chronic obstructive pulmonary disease is controversial. In older studies, the rates of isolation of bacterial pathogens from sputum were the same during acute exacerbations and during stable disease. However, these studies did not differentiate among strains within a bacterial species and therefore could not detect changes in strains over time. We hypothesized that the acquisition of a new strain of a pathogenic bacterial species is associated with exacerbation of chronic obstructive pulmonary disease.


METHODS
We conducted a prospective study in which clinical information and sputum samples for culture were collected monthly and during exacerbations from 81 outpatients with chronic obstructive pulmonary disease. Molecular typing of sputum isolates of nonencapsulated Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, and Pseudomonas aeruginosa was performed.


RESULTS
Over a period of 56 months, the 81 patients made a total of 1975 clinic visits, 374 of which were made during exacerbations (mean, 2.1 per patient per year). On the basis of molecular typing, an exacerbation was diagnosed at 33.0 percent of the clinic visits that involved isolation of a new strain of a bacterial pathogen, as compared with 15.4 percent of visits at which no new strain was isolated (P<0.001; relative risk of an exacerbation, 2.15; 95 percent confidence interval, 1.83 to 2.53). Isolation of a new strain of H. influenzae, M. catarrhalis, or S. pneumoniae was associated with a significantly increased risk of an exacerbation.


CONCLUSIONS
The association between an exacerbation and the isolation of a new strain of a bacterial pathogen supports the causative role of bacteria in exacerbations of chronic obstructive pulmonary disease.
Division of Pulmonary and Critical Care Medicine, Department of Medicine, State University of New York, Buffalo, NY, USA. ssethi@buffalo.edu
Sanjay
S
Sethi
Nancy
N
Evans
Brydon J B
BJ
Grant
Timothy F
TF
Murphy
D000368:Aged; D000369:Aged, 80 and over; D001419:Bacteria / Q000145:classification* / Q000302:isolation & purification; D015373:Bacterial Typing Techniques; D004417:Dyspnea / Q000209:etiology / Q000382:microbiology; D005260:Female; D006193:Haemophilus influenzae / Q000145:classification / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D001936:Moraxella catarrhalis / Q000145:classification / Q000302:isolation & purification; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000382:microbiology*; D013183:Sputum / Q000382:microbiology; D013211:Staphylococcus aureus / Q000145:classification / Q000302:isolation & purification; D013296:Streptococcus pneumoniae / Q000145:classification / Q000302:isolation & purification