Thirty-seven carbapenem-resistant Enterobacteriaceae (CRE)-infected patients were treated with ceftazidime-avibactam. Clinical success and survival rates at 30 days were 59% (22/37) and 76% (28/37), respectively. In 23% (5/22) of clinical successes, CRE infections recurred within 90 days. Microbiologic failure rate was 27% (10/37). Ceftazidime-avibactam resistance was detected in 30% (3/10) of microbiologic failures.Keywords. ceftazidime-avibactam resistance; carbapenemresistant Enterobacteriaceae; Klebsiella pneumoniae carbapenemase.Ceftazidime-avibactam is a novel β-lactam/β-lactamase inhibitor combination that was recently approved by the US Food and Drug Administration for the treatment of complicated intraabdominal and complicated urinary tract infections [1]. The agent demonstrates in vitro activity against carbapenem-resistant Enterobacteriaceae (CRE) that produce Klebsiella pneumoniae carbapenemase (KPC), but not metallo-β-lactamases such as New Delhi MBL (NDM), Verona integron-encoded MBL (VIM), or imipenemase (IMP) [2]. Ceftazidime-avibactam may offer a significant advance over previously developed antimicrobials with in vitro activity against CRE, such as colistin, gentamicin, and tigecycline, which are limited by concerns over efficacy and/or toxicity. Our objective in this study was to describe our initial clinical experience with ceftazidimeavibactam against CRE infections. METHODSWe conducted a retrospective study of patients with CRE infection who were treated with ceftazidime-avibactam at the University of Pittsburgh Medical Center between April 2015 and February 2016. CRE was defined by current Centers for Disease Control and Prevention criteria as resistance to any carbapenem [3]. A standard dosage of 2.5 g intravenously (IV) every 8 hours was used, with adjustments for renal impairment made according to manufacturer recommendations [1]. Types of CRE infection were classified according to National Healthcare Safety Network criteria [4]. Clinical success was defined as survival and absence of recurrence at 30 days following the onset of infection, resolution of signs and symptoms of infection, and sterilization of site-specific cultures within 7 days of treatment initiation. Microbiologic failure was defined as isolation of CRE following ≥7 days of ceftazidime-avibactam treatment. Recurrences within 90 days of onset were defined by microbiologic failure and concomitant signs of infection. Minimum inhibitory concentrations (MICs) were determined using reference Clinical and Laboratory Standards Institute broth microdilution methods; avibactam was tested at a fixed concentration of 4 µg/mL [2]. Isolates were tested for the presence of β-lactamases as described previously [5,6]. Comparisons between groups were made using Fisher exact test (categorical variables) and Mann-Whitney U (continuous variables). Significance was defined as P ≤ .05 (2-tailed). RESULTSThirty-seven consecutive patients treated for 3 days or longer with ceftazidime-avibactam were evaluated. Median age was 64 years (range, 26-...

Background. Data on the use of ceftolozane-tazobactam and emergence of ceftolozane-tazobactam resistance during multidrug resistant (MDR)-Pseudomonas aeruginosa infections are limited.Methods. We performed a retrospective study of 21 patients treated with ceftolozane-tazobactam for MDR-P. aeruginosa infections. Whole genome sequencing and quantitative real-time polymerase chain reaction were performed on longitudinal isolates.Results. Median age was 58 years; 9 patients (43%) were transplant recipients. Median simplified acute physiology score-II (SAPS-II) was 26. Eighteen (86%) patients were treated for respiratory tract infections; others were treated for bloodstream, complicated intraabdominal infections, or complicated urinary tract infections. Ceftolozane-tazobactam was discontinued in 1 patient (rash). Thirty-day all-cause and attributable mortality rates were 10% (2/21) and 5% (1/21), respectively; corresponding 90-day mortality rates were 48% (10/21) and 19% (4/21). The ceftolozane-tazobactam failure rate was 29% (6/21). SAPS-II score was the sole predictor of failure. Ceftolozane-tazobactam resistance emerged in 3 (14%) patients. Resistance was associated with de novo mutations, rather than acquisition of resistant nosocomial isolates. ampC overexpression and mutations were identified as potential resistance determinants.Conclusions. In this small study, ceftolozane-tazobactam was successful in treating 71% of patients with MDR-P. aeruginosa infections, most of whom had pneumonia. The emergence of ceftolozane-tazobactam resistance in 3 patients is worrisome and may be mediated in part by AmpC-related mechanisms. More research on treatment responses and resistance during various types of MDR-P. aeruginosa infections is needed to define ceftolozane-tazobactam's place in the armamentarium.

Background. The sensitivity of blood cultures for diagnosing invasive candidiasis (IC) is poor. Methods. We performed a validated Candida real-time polymerase chain reaction (PCR) and the Fungitell 1,3-b-D-glucan (BDG) assay on blood samples collected from prospectively identified patients with IC (n 5 55) and hospitalized controls (n 5 73). Patients with IC had candidemia (n 5 17), deep-seated candidiasis (n 5 33), or both (n 5 5). Controls had mucosal candidiasis (n 5 5), Candida colonization (n 5 48), or no known Candida colonization (n 5 20). Results. PCR using plasma or sera was more sensitive than whole blood for diagnosing IC (P 5 .008). Plasma or sera PCR was more sensitive than BDG in diagnosing IC (80% vs 56%; P 5 .03), with comparable specificity (70% vs 73%; P 5 .31). The tests were similar in diagnosing candidemia (59% vs 68%; P 5 .77), but PCR was more sensitive for deep-seated candidiasis (89% vs 53%; P 5 .004). PCR and BDG were more sensitive than blood cultures among patients with deep-seated candidiasis (88% and 62% vs 17%; P 5 .0005 and .003, respectively). PCR and culture identified the same Candida species in 82% of patients. The sensitivity of blood cultures combined with PCR or BDG among patients with IC was 98% and 79%, respectively. Conclusions. Candida PCR and, to a lesser extent, BDG testing significantly enhanced the ability of blood cultures to diagnose IC.

Caspofungin exerts candidacidal activity by inhibiting cell wall (1,3)-␤-D-glucan synthesis. We investigated the physiologic mechanisms of caspofungin-induced Candida albicans cell death. Apoptosis (programmed cell death) and necrosis were studied after C. albicans SC5314 cells were exposed to caspofungin at 0.06, 0.125, and 0.5 g/ml (0.5؋, 1؋, and 4؋ the MIC, respectively) for 3 h. Caspofungin at 0.125 and 0.5 g/ml reduced cellular viability by >50%, as measured by colony counts and methylene blue exclusion. Apoptosis and necrosis were demonstrated by annexin V and propidium iodide staining for phosphatidylserine externalization and loss of membrane integrity, respectively. At all concentrations of caspofungin, 20 to 25% and 5 to 7% of C. albicans cells exhibited early apoptosis and late apoptosis/necrosis, respectively (P value was not significant [NS]). Necrosis, on the other hand, was significantly greater at 0.125 (43%) and 0.5 (48%) g/ml than at 0.06 g/ml (26%) (P values of 0.003 and 0.003, respectively). The induction of apoptosis at concentrations less than or equal to the MIC was corroborated by dihydrorhodamine 123 (DHR-123) and dihydroethidium (DHE) staining (reactive oxygen species production), JC-1 staining (mitochondrial membrane potential dissipation), and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) and 4=,6-diamidino-2-phenylindole dihydrochloride (DAPI) staining (DNA damage and nuclear fragmentation). Moreover, electron microscopy of cells exposed to 0.125 g/ml of caspofungin showed hallmark apoptotic features like chromatin margination and condensation and nuclear blebs. Apoptosis was associated with metacaspase 1 activation, as demonstrated by D2R staining. Caspofungin exerts activity against C. albicans by directly killing cells (resulting in necrosis) and causing others to undergo programmed cell death (apoptosis). Apoptosis is initiated at subinhibitory concentrations, suggesting that strategies to target this process may augment the benefits of antifungal agents.C aspofungin and other agents in the echinocandin class of antifungals have assumed an increasingly important role in the therapy of invasive candidiasis (1). These agents are nontoxic and exert potent fungicidal activity against Candida albicans and other Candida spp. Their antifungal activity is achieved through inhibition of (1,3)-␤-D-glucan synthase (2), an enzyme that synthesizes a major constituent of the fungal cell wall. Although the mechanism of activity for the echinocandins is known, the physiological mechanisms by which they cause cell death are not defined. At least two types of mammalian cell death, necrosis and apoptosis, have been described (3). Necrosis is death resulting from direct cellular injury, which is best defined by cell and organelle swelling and lysis (4). Apoptosis, on the other hand, is programmed cell death, the principal morphological feature of which is shrinkage of the cell and its nucleus (3, 4).Over the last decade, there have been a number of reports on apoptosis in yeas...