Methods: This was a single-center, retrospective, case-cohort study consisting of adult patients who had clinical infection with a SPICE organism isolated from blood or urine cultures. Patients were excluded if they did not receive at least 48 hours of antimicrobial therapy, had a polymicrobial infection, or received additional antibiotics due to a concomitant infection. Patients were divided into carbapenem or non-carbapenem regimen groups. The primary endpoint was clinical response defined as resolution of signs and symptoms of infection at the end of therapy.
Results: A total of 145 patients were enrolled in this study. There were 20 patients who received meropenem while 125 received a non-carbapenem regimen. The percentage of patients that were bacteremic was 46.2%. The most common organisms isolated were Enterobacter in 38.6% of patients followed by Pseudomonas in 33.8%. Clinical response overall was achieved in 80% of patients on meropenem versus 90.3% of patients on non-carbapenem regimens (p=0.24). Microbiologic cure was 90% for patients on meropenem versus 91.2% for patients on non-carbapenem regimens (p=1). The results were similar after logistic regression controlling for SAPSII score and source of infection. The most common non-carbapenem antibiotic utilized for bacteremia was piperacillin/tazobactam (77.6%) and for UTI was ceftriaxone (41.0%). Piperacillin/tazobactam had an 88.5% rate of clinical response for bacteremia (p=0.41 versus carbapenem). Ceftriaxone had an 84.4% rate of clinical response for UTI (p=1 versus carbapenem).
Conclusion: In this “real-world” study, clinical response of patients treated for a SPICE organism did not differ significantly between carbapenem and non-carbapenem regimens. Current CLSI breakpoints set for SPICE organisms may still reliable and may not require additional testing for AmpC β-lactamases.