Trends in Antibiotic Use and Nosocomial Pathogens in Hospitalized Veterans With Pneumonia at 128 Medical Centers, 2006-2010

Abstract

Background: In 2005, pneumonia practice guidelines recommended broad-spectrum antibiotics for patients with risk factors for nosocomial pathogens. The impact of these recommendations on the ability of providers to match treatment with nosocomial pathogens is unknown.

Methods: Among hospitalizations with a principal diagnosis of pneumonia at 128 Department of Veterans Affairs medical centers from 2006 through 2010, we measured annual trends in antibiotic selection; initial blood or respiratory cultures positive for methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Acinetobacter species; and alignment between antibiotic coverage and culture results for MRSA and P. aeruginosa, calculating sensitivity, specificity, and diagnostic odds ratio using a 2 × 2 contingency table.

Results: In 95 511 hospitalizations for pneumonia, initial use of vancomycin increased from 16% in 2006 to 31% in 2010, and piperacillin-tazobactam increased from 16% to 27%, and there was a decrease in both ceftriaxone (from 39% to 33%) and azithromycin (change from 39% to 36%) (P < .001 for all). The proportion of hospitalizations with cultures positive for MRSA decreased (from 2.5% to 2.0%; P < .001); no change was seen for P. aeruginosa (1.9% to 2.0%; P = .14) or Acinetobacter spp. (0.2% to 0.2%; P = .17). For both MRSA and P. aeruginosa, sensitivity increased (from 46% to 65% and 54% to 63%, respectively; P < .001) and specificity decreased (from 85% to 69% and 76% to 68%; P < .001), with no significant changes in diagnostic odds ratio (decreases from 4.6 to 4.1 [P = .57] and 3.7 to 3.2 [P = .95], respectively).

Conclusions: Between 2006 and 2010, we found a substantial increase in the use of broad-spectrum antibiotics for pneumonia despite no increase in nosocomial pathogens. The ability of providers to accurately match antibiotic coverage to nosocomial pathogens remains low.

Keywords: HCAP; antibiotic use; drug-resistant pneumonia; nosocomial pathogens; pneumonia.

Figure 1.

Proportion of hospitalized veterans with principal infectious diagnoses, 2006–2010 (total number hospitalized, 2.4 million).

Figure 2.

Five-year trends in initial antibiotic use for hospitalized patients with pneumonia, 2006–2010. Error bars represent 95% confidence intervals.

Figure 3.

Trends in antimicrobial coverage for hospitalized patients with pneumonia in 2006–2010. Error bands represent 95% confidence intervals, For coverage, any atypical coverage includes respiratory fluoroquinolones, macrolide, and tetracycline; standard or guideline-concordant coverage includes nonpseudomonal β-lactam plus a macrolide and respiratory fluoroquinolone; nonpseudomonal β-lactam coverage includes ampicillin, amoxicillin, ampicillin-sulbactam, amoxicillin-clavulanate, cefuroxime, cefotaxime, ceftriaxone, ceftizoxime, cefixime, cefpodoxime, ceftibuten, cefdinir, and ertapenem; single Pseudomonas coverage includes piperacillin-tazobactam, ticarcillin-clavulanate, ceftazidime, cefepime, meropenem, doripenem, imipenem, aztreonam, and aminoglycoside; methicillin-resistant Staphylococcus aureus (MRSA) coverage includes vancomycin and linezolid; and double Pseudomonas coverage includes any 2 of the above or 1 of the above plus ciprofloxacin or levofloxacin.

Figure 4.

Proportion of hospitalized patients with pneumonia with cultures positive for Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA), or Acinetobacter spp. within 2 days of hospitalization.

Figure 5.

Trends in match between coverage and culture for methicillin-resistant Staphylococcus aureus (MRSA) (A) and Pseudomonas aeruginosa (B). Error bands represent 95% confidence intervals. Sensitivity was defined as the proportion of patients with MRSA- or Pseudomonas-positive cultures who received anti-MRSA or antipseudomonal therapy; specificity, the proportion without positive cultures who did not receive such therapy. The diagnostic odds ratio is a composite measure of performance reflecting both sensitivity and specificity (see “Statistical Analysis” section and Table 1).