Sputum susceptibilities in a nationwide veteran cohort

Background: Respiratory infections are one of the most common causes of morbidity and mortality. This study examined antimicrobial susceptibility of common respiratory isolates from veterans. Methods: Sputum culture data from the Veteran Health Administration were obtained retrospectively between January 2009 and 2019. Cumulative antibiograms were constructed for bacterial isolate susceptibility. Results: Sputum and bronchial cultures from approximately 10,345 veterans were included each year. Haemophilus influenzae has maintained high levels of susceptibility to third generation cephalosporins from 2009 (99.7%) to 2018 (97.2%). Third generation cephalosporin susceptibilities amongst Klebsiella pneumoniae have trended upward from 2009 to 2018 as well (79.1% vs 86.4%). In Pseudomonas aeruginosa isolates, there has been an increase in susceptibility rates to cefepime from 2009 to 2018 (79.6%, to 86.6%), gentamicin (81.5% to 89.1%), and piperacillin/tazobactam (86.5% to 90%). Fluoroquinolone susceptibilities amongst Escherichia coli have remained low but stable between 2009 and 2018. Third generation cephalosporin susceptibilities for S. pneumoniae improved slightly from 92.2% to 95% between 2009 and 2018 while susceptibility to azithromycin trended down slightly from 56.8% in 2009 to 51.7% in 2018 for S. pneumoniae. Discussion: The antibiogram of sputum isolates from the VA Healthcare System were examined to determine changes in patterns of resistance over a decade of use. Conclusions: This large-scale study investigated nationwide sputum culture susceptibility trends. Avoidance of macrolides for empiric treatment of community acquired pneumonia and avoidance of fluoroquinolones for empiric treatment of hospital acquired or ventilator associated pneumonia may be warranted based on susceptibility trends.