2014. Characterization of Piperacillin-tazobactam-Non-Susceptible, but Ceftriaxone-Susceptible, Escherichia coli and Klebsiella pneumoniae Bloodstream Infections
Session: Poster Abstract Session: Antimicrobial Resistant Infections: Treatment
Saturday, October 29, 2016
Room: Poster Hall
Background: Piperacillin-tazobactam-non-susceptible (PTZ-NS) Enterobacteriaceae are typically resistant to third-generation cephalosporins. We recently encountered bloodstream infections due to Escherichia coli (Ec) and Klebsiella pneumoniae (Kp) that were PTZ-NS, but ceftriaxone-susceptible (CTX-S), and sought to better understand the epidemiology of infections.

Methods: We reviewed all Ec and Kpbacteremias from 2011-2015 at our medical center and determined the proportion of bacteremias due to a PTZ-NS, CTX-S phenotype. We also assessed antimicrobial susceptibilities and characterized patients with these infections.

Results: There were 1857 episodes of Ec (n=1227) and Kp (n=630) bacteremia, of which 78 (4.2%) were PTZ-NS, CTX-S (Ec: 50 [4.1%]; Kp: 28 [4.4%]). There was a non-significant increase in prevalence during the study period (p=0.06). Thirty-three isolates (42%) were PTZ-intermediate and 45 (58%) were PTZ-resistant. No isolates were ampicillin/sulbactam-S, 11% were amoxicillin-clavulanate-S, all were meropenem-S, and 97% were aztreonam-S. The majority (53%) of patients with PTZ-NS, CTX-S Ec or Kp bacteremia were hospital inpatients at infection onset, 42% had a hematologic malignancy, 38% had recently received chemotherapy, and 73% had recently received antibacterial agents, including 44% who had received a β-lactam/β-lactamase inhibitor (BL/BLI). The most common bacteremia sources were presumed gastrointestinal translocation (41%), urinary (23%) and biliary (22%). Hypotension was present at bacteremia onset in 62% of patients and 31% required transfer to an intensive care unit. Mortality at 14 and 30 days was 19% and 25%, respectively. Thirty-day mortality was 20% (8/41) in patients treated empirically with BL/BLIs and 28% (5/28) in those who received empiric carbapenem therapy. The mortality rate was 17% (5/30) and 33% (9/27) for targeted therapy with cephalosporins and carbapenems respectively (p=0.14).

Conclusion: Ec and Kp that are PTZ-NS, CTX-S, are emerging as causes of bacteremia with substantial morbidity and mortality, particularly in patients with hematologic malignancies. More research is needed to assess risk factors, optimal therapies, and resistance mechanisms for these infections.

Thomas Baker, MD, Division of Infectious Diseases, Weill Cornell Medicine-New York Presbyterian Hospital, New York, NY, David P. Calfee, MD, MS, FIDSA, FSHEA, Weill Cornell Medicine, New York, NY, Lars Westblade, PhD, Emory University School of Medicine, Atlanta, GA, Stephen Jenkins, PhD, New York-Presbyterian Weill Cornell Medical Center, New York, NY, Barry N. Kreiswirth, PhD, Public Health Research Institute Tuberculosis Center, Rutgers University, Newark, NJ and Michael Satlin, MD, New York-Presbyterian, New York, NY


T. Baker, None

D. P. Calfee, None

L. Westblade, None

S. Jenkins, None

B. N. Kreiswirth, None

M. Satlin, Allergan: Grant Investigator , Grant recipient

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