We evaluated the efficacy of NXL104 a novel β-lactamase inhibitor in combination with ceftazidime (CAZ) in two murine infection models (septicemia Carfilzomib and thigh infection). of cyclophosphamide at days ?4 and ?1 preinfection. Infection was established by the intramuscular injection of KPC-producing into the right thigh. Mice were treated 1.5 h postinfection with either CAZ alone or CAZ-NXL104 at constant ratios of 4:1. When thighs were removed at 24 h postinfection a >2-log CFU reduction was observed for mice treated with CAZ-NXL104 at doses of ≥128:32 mg/kg. In contrast CAZ doses of ≥1 24 mg/kg were unable to reduce the numbers of CFU. Despite resistance to CAZ and possessing a complex β-lactamase background NXL104 Carfilzomib combined with CAZ proved to be very effective in murine models of infection due to contemporary highly resistant KPC-producing isolates. The spread of class A KPC carbapenemases among the family (particularly spp. and is Carfilzomib drawing significant attention due to the important clinical implications that Rabbit Polyclonal to SLC27A5. this resistance determinant bears for infected patients (11 21 25 KPC-producing isolates are endemic in certain hospitals and are responsible for increasing numbers of outbreaks in many health care facilities located in the United States Puerto Rico Israel Greece and Germany (10 17 27 Sporadic detection in Central and South America the Far East and other European countries has also been reported (1 9 17 18 20 23 KPC-producing isolates demonstrate resistance or reduced susceptibility to most commercially available β-lactams and β-lactam/β-lactamase inhibitor combinations as well as many other alternative classes of antimicrobials (e.g. fluoroquinolones and aminoglycosides) (5 17 Thus colistin tigecycline and fosfomycin are becoming the “last-line” therapeutic options for infections due to KPC-producing isolates. Unfortunately the clinical use (e.g. dosage and time of treatment) of these antimicrobials is not yet fully defined and their level of resistance prices for KPC-producing strains may also be quickly raising (7 11 15 23 28 Fairly few novel substances are in advancement that promise to become energetic against Gram-negative multidrug-resistant Carfilzomib (MDR) pathogens such as for example those creating KPC enzymes (3 6 NXL104 (Novexel SA Romainville France and AstraZeneca Pharmaceuticals Boston Carfilzomib MA) is certainly a fresh β-lactamases inhibitor that’s active against course A (e.g. TEM SHV and CTX-M types) Carfilzomib and course C β-lactamases and happens to be in clinical studies (http://clinicaltrials.gov) (2 14 22 Recently Endimiani et al. confirmed its activity in conjunction with regular β-lactams against a big assortment of KPC-producing isolates gathered in the Eastern USA (4). Specifically the MICs from the mix of NXL104 at a continuing focus of 4 μg/ml with piperacillin extended-spectrum cephalosporins (e.g. ceftazidime and cefotaxime) and aztreonam had been in the prone range for everyone examined strains (general MIC90 beliefs of ≤2 μg/ml) (4). In today’s work we examined the antibacterial efficiency of ceftazidime (CAZ) in conjunction with NXL104 within a mouse septicemia model and a mouse thigh infections model using two well-characterized KPC-producing strains. Our data present the fact that addition of NXL104 leads to a significant recovery of ceftazidime efficiency and the capability to eradicate attacks because of KPC-producing isolates. Strategies and Components Clinical isolates. experiments were executed through the use of two KPC-producing isolates (i.e. VA-361 and VA-406) characterized previously (4 5 Both strains had been gathered in the Eastern United States and are clonally related by pulsed-field gel electrophoresis (PFGE) and repetitive extragenic palindromic PCR (rep-PCR) analyses (5). The molecular and phenotypic profiles of the two KPC-producing isolates are shown in Table ?Table1.1. isolate ATCC 13883 was also used as a control. This ATCC strain has an MIC value of CAZ of 2 μg/ml. TABLE 1. Characteristics of the two KPC-producing isolates used for the experimentsstrain resulting in the death of untreated controls within 24 to 48 h. In particular a fresh predetermined bacterial inoculum of approximately 3.3 × 105 to 3.6 × 105 CFU in 5% hog gastric mucin produced overnight was used for both KPC-producing isolates. Thirty minutes postinfection a single subcutaneous dose of ceftazidime (Sigma-Aldrich St. Louis MO) with and without NXL104 (see below for dosages) was initiated and the survival ratio was monitored for 5 days twice a day. For VA-361 5 mice/dose level for each of the following treatment regimens were tested: CAZ alone (doses of 512 1 24 and 2 48 mg/kg.