Background: Multiple in vitro studies have demonstrated Streptococcus pneumoniae resistance to β-lactams, including ceftriaxone. The clinical impact of resistance has not been fully evaluated in patients with pneumonia caused by drug-resistant strains of S. pneumoniae.
Methods: Adult inpatients 18 or older and younger than 89 years with a diagnosis of pneumonia plus a respiratory culture positive for S. pneumoniae between January 2007 and September 2012 were evaluated. Patients with pneumonia due to ceftriaxone-resistant (minimum inhibitory concentration >1 µg/mL) S. pneumoniae (CRSP) were compared with those with ceftriaxone-susceptible S. pneumoniae (CSSP). Statistical significance was ascertained using 2-tailed χ2 or Fisher exact test.
Results: Thirty patients were evaluated: 10 with CRSP and 20 with CSSP. No patient with CRSP had prior ceftriaxone exposure. Seven CRSP patients (70%) achieved a clinical cure compared with 14 CSSP patients (70%) (P = 1.00). Time to clinical cure for CRSP was 4 (1–5) days compared with 8 (3–12) days for CSSP (P = 0.51). Length of stay and infection-related length of stay were 17 days (9–23) and 9 days (7–13) for patients with CRSP, respectively, compared with 15 (8–20) days and 8 (7–13) days for patients with CSSP (P = 0.46, 0.74). No patient with CRSP died or was readmitted for pneumonia. Of the 10 CRSP isolates, 100% were resistant to azithromycin, 90% to penicillin, and 70% to cefepime.
Conclusions: Although differences in clinical outcomes were not observed, isolates resistant to ceftriaxone were more likely to be multidrug resistant. As the proportion of pneumococcal isolates with elevated minimum inhibitory concentrations to β-lactams continues to rise, treatment options may become more limited.