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.

Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Figures

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).