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Background Pseudomonas aeruginosa (PsAr) isolates harboring OprD mutations often present phenotypically as carbapenem nonsusceptible but susceptible to antipseudomonal β-lactams (APBLs). It is unknown whether this unique genotype–phenotype combination affects the clinical outcomes of patients infected with these pathogens. The objective of this study was to compare clinical outcomes of patients treated with APBLs for pneumonia and/or bacteremia caused by PsAr bearing this unique carbapenem nonsusceptible, β-lactam susceptible phenotype (Carba-NS) to those retaining susceptibility to both carbapenems and APBLs (Carba-S). Methods Retrospective multicenter cohort of adult in-patients who received effective APBL for PsAr pneumonia and/or bacteremia from January 2012 to November 2018. Baseline characteristics, treatment information, and clinical outcomes were obtained from the electronic medical record. The primary outcome was 14-day mortality. Secondary outcomes included 30-day mortality, 30-day infection recurrence, and infection-related length of stay (IR-LOS). IR-LOS was defined as the time from index culture to antibiotic discontinuation or hospital discharge, whichever was sooner. Descriptive statistics were analyzed using SPSS. Results 387 patients were evaluated; 60 Carba-S and 21 Carba-NS were included. The primary reason for exclusion was ineffective empiric therapy. Select demographics and clinical outcomes are displayed in Table 1. Compared with the Carba-S group, Carba-NS patients were younger, had better renal function, increased incidence of pneumonia, more severely ill, and higher rate of empiric ceftazidime use. Despite these differences at baseline there were no significant differences in empiric APBL treatment patterns, 14- or 30-day mortality, or recurrence at 30 days between the groups. Carba-NS patients had lower rate of oral step down therapy and a significantly longer LOS and IR-LOS. Conclusion In this cohort of patients who received appropriate and timely APBL therapy, the Carba-NS phenotype was not associated with increased rates of 14-day mortality, 30-day mortality, or 30-day infection recurrence. These data suggest that APBLs may be effective therapeutic options against this phenotype. Further research is warranted to confirm these findings. Disclosures All authors: No reported disclosures.

Safe anaerobic metabolism Naked mole-rats live in large colonies deep underground in hypoxic conditions. Park et al. found that these animals fuel anaerobic glycolysis with fructose by a rewired pathway that avoids tissue damage (see the Perspective by Storz and McClelland). These results provide insight into the adaptations that this strange social rodent has to make for life underground. They also have implications for medical practice, particularly for understanding how to protect tissues from hypoxia. Science , this issue p. 307 ; see also p. 248