Community-acquired Pneumonia in North American Emergency Departments: Drug Resistance and Treatment Success with Clarithromycin

Background: Limited information on antibiotic resistance of Streptococcus pneumoniae (SP) exists for patients discharged from emergency departments with community-acquired pneumonia.
Objectives: Using a standardized collection process, this study examined sputum microbiology in outpatient community-acquired pneumonia.
Methods: This was a multicenter, prospective cohort study conducted in North American emergency departments between December 2001 and May 2003. Thirty-one emergency departments enrolled patients older than 18 years with a Pneumonia Severity Index of I to III. All patients received oral clarithromycin and were followed up for four weeks. SP resistance to macrolides and penicillin was determined by a central laboratory.
Results: Among the 317 cultured sputum samples, 116 (37%; 95% confidence interval [CI] = 32% to 42%) grew an identifiable organism; 74 (23% of cultured cases; 95% CI = 19% to 28%) grew non-SP organisms and 42 grew SP organisms (SP positive; 13% of cultured cases; 95% CI = 10% to 17%). A total of 13 resistant organisms (4% of cultured cases; 95% CI = 2% to 6%) were identified. Resistance to macrolides occurred in nine patients (3% of cultured cases [95% CI = 1% to 5%]; 24% of SP-positive cases [95% CI = 11% to 37%]); and resistance to penicillin occurred in nine patients (3% of all sputum-positive cases [95% CI = 1% to 5%]; 21% of SP-positive cases [95% CI = 9% to 34%]). The four-week cure rates were similar in both groups.
Conclusions: Among outpatients with community-acquired pneumonia, half produced adequate sputum samples and most were culture negative. SP resistance was similar to rates from large national databases, and results were of little (if any) consequence. In low-risk Pneumonia Severity Index cases, sputum cultures should not be collected routinely.