Molecular β-lactamase characterization of Gram-negative pathogens recovered from patients enrolled in the ceftazidime-avibactam phase 3 trials (RECAPTURE 1 and 2) for complicated urinary tract infections: Efficacies analysed against susceptible and resist

This study characterized the β-lactamase content of baseline pathogens recovered from patients with complicated urinary tract infections (cUTI), including acute pyelonephritis, who were enrolled in two phase 3 clinical trials of ceftazidime-avibactam (RECAPTURE 1 and 2), and correlated the clinical efficacy of ceftazidime-avibactam and the comparator doripenem according to resistance mechanisms. A total of 26.2% (93/355) ceftazidime-avibactam and 26.8% (101/377) doripenem patients had baseline isolates that met the MIC screening criteria. The majority of Enterobacteriaceae (87.5%; 154/176) carried blaCTX-M. This pattern was mainly observed in Escherichia coli (96.8%; 92/95) and Klebsiella pneumoniae (96.0%; 48/50), whereas most Proteus mirabilis (80.0%; 8/10) carried plasmid AmpC genes. Two K. pneumoniae and 1 Klebsiella oxytoca carried blaOXA-48 and 1 K. pneumoniae carried blaNDM-1. Five (13/35; 37.1%) Pseudomonas aeruginosa isolates were screened, and 2 carbapenemase producers (IMP-18 and VIM-2) were detected. Among patients enrolled in the ceftazidime-avibactam arm who were infected by MIC screen-positive Enterobacteriaceae, clinical cure occurred in 85.7-95.5%, regardless of β-lactamase content; the respective rate in the doripenem arm was 82.1-92.5%. A total of 75.0% in the ceftazidime-avibactam arm and 100.0% in the doripenem arm of patients infected by P. aeruginosa with MIC screen-positive criteria were clinically cured. Ceftazidime-avibactam efficacy was comparable to doripenem efficacy for treating cUTI caused by uropathogens producing extended-spectrum and/or AmpC β-lactamases.

Mendes RE ，Castanheira M ，Woosley LN ，Stone GG ，Bradford PA ，Flamm RK ... -  《-》

Activity of Ceftazidime-Avibactam against Extended-Spectrum- and AmpC β-Lactamase-Producing Enterobacteriaceae Collected in the INFORM Global Surveillance Study from 2012 to 2014.

The in vitro activity of ceftazidime-avibactam was evaluated against 34,062 isolates of Enterobacteriaceae from patients with intra-abdominal, urinary tract, skin and soft-tissue, lower respiratory tract, and blood infections collected in the INFORM (International Network For Optimal Resistance Monitoring) global surveillance study (176 medical center laboratories in 39 countries) in 2012 to 2014. Overall, 99.5% of Enterobacteriaceae isolates were susceptible to ceftazidime-avibactam using FDA approved breakpoints (susceptible MIC of ≤8 μg/ml; resistant MIC of ≥16 μg/ml). For individual species of the Enterobacteriaceae, the ceftazidime-avibactam MIC inhibiting ≥90% of isolates (MIC90) ranged from 0.06 μg/ml for Proteus species to 1 μg/ml for Enterobacter spp. and Klebsiella pneumoniae Carbapenem-susceptible isolates of Escherichia coli, K. pneumoniae, Klebsiella oxytoca, and Proteus mirabilis with a confirmed extended-spectrum β-lactamase (ESBL) phenotype, or a ceftazidime MIC of ≥16 μg/ml if the ESBL phenotype was not confirmed by clavulanic acid inhibition, were characterized further to identify the presence of specific ESBL- and plasmid-mediated AmpC β-lactamase genes using a microarray-based assay and additional PCR assays. Ceftazidime-avibactam demonstrated potent activity against molecularly confirmed ESBL-producing (n = 5,354; MIC90, 0.5 μg/ml; 99.9% susceptible), plasmid-mediated AmpC-producing (n = 246; MIC90, 0.5 μg/ml; 100% susceptible), and ESBL- and AmpC-producing (n = 152; MIC90, 1 μg/ml; 100% susceptible) isolates of E. coli, K. pneumoniae, K. oxytoca, and P. mirabilis We conclude that ceftazidime-avibactam demonstrates potent in vitro activity against globally collected clinical isolates of Enterobacteriaceae, including isolates producing ESBLs and AmpC β-lactamases.

Karlowsky JA ，Biedenbach DJ ，Kazmierczak KM ，Stone GG ，Sahm DF ... -  《-》

β-Lactamase Characterization of Gram-Negative Pathogens Recovered from Patients Enrolled in the Phase 2 Trials for Ceftazidime-Avibactam: Clinical Efficacies Analyzed against Subsets of Molecularly Characterized Isolates.

The correlation of the clinical efficacies of ceftazidime-avibactam and comparators (carbapenems) was evaluated against baseline Gram-negative isolates having characterized β-lactam resistance mechanisms from complicated urinary tract infection (cUTI) and complicated intra-abdominal infection (cIAI) phase 2 trials. Enterobacteriaceae displaying ceftriaxone and/or ceftazidime MICs of ≥ 2 μg/ml (69 isolates) and nonfermentative Gram-negative bacilli (NF-GNB [three isolates]) with ceftazidime MICs of ≥ 16 μg/ml were characterized for their narrow- and extended-spectrum β-lactamase (ESBL) content. Enterobacteriaceae (one isolate) and NF-GNB (three isolates) with imipenem/meropenem MICs of ≥ 2 and ≥ 16 μg/ml, respectively, were tested for carbapenemases. All cUTI E. coli had the lineage background investigated (ST131-like versus non-ST131-like). The primary efficacy endpoint was microbiological response (eradication) at test of cure (TOC) for cUTI and clinical response (inferred microbiological eradication) at TOC for cIAI. A total of 34.1% of baseline cUTI (36.4%) and cIAI (33.1%) pathogens met the MIC-based screening criteria (screen positive). All screen-positive cUTI pathogens were CTX-M-producing E. coli, except for one E. cloacae isolate with AmpC overexpression. The majority (66.7%) of screen-positive cIAI isolates produced CTX-M-type coupled with a diverse array of other β-lactamases. Similar favorable responses were observed with ceftazidime-avibactam (93.3%) and carbapenems (90.9%), when a non-ESBL Enterobacteriaceae isolate was recovered at the baseline visit. When an ESBL Enterobacteriaceae isolate was present, the favorable responses were 85.7% and 80.0% with ceftazidime-avibactam and carbapenems, respectively. Higher favorable responses were observed with ceftazidime-avibactam (75.0%) than with carbapenems (66.7%) when an ST131-like E. coli isolate was recovered at baseline, as when a non-ST131-like isolate was present (93.8% versus 86.7%, respectively). The efficacy of ceftazidime-avibactam was similar to that of carbapenems for treatment of cUTI and cIAI caused by ESBL organisms.

Mendes RE ，Castanheira M ，Gasink L ，Stone GG ，Nichols WW ，Flamm RK ，Jones RN ... -  《-》

In vitro activity of ceftazidime/avibactam against urinary isolates from patients in a Phase 3 clinical trial programme for the treatment of complicated urinary tract infections.

To evaluate the in vitro activity of ceftazidime/avibactam relative to comparator agents against Gram-negative isolates from a Phase 3 clinical trial programme for complicated urinary tract infections (RECAPTURE). The in vitro activity of ceftazidime/avibactam was evaluated against 840 Gram-negative pathogens isolated at baseline from 1033 randomized patients in two pivotal Phase 3 clinical trials for the treatment of complicated urinary tract infections. The trials were conducted in 160 institutions from 25 countries worldwide. Susceptibility testing was performed by broth microdilution at a central laboratory according to CLSI methodologies. Overall, ceftazidime/avibactam showed significant activity against the Enterobacteriaceae and Pseudomonas aeruginosa with MIC 90 values of 0.5 and 8 mg/L, respectively. Against the most common Enterobacteriaceae, MIC 90 values were 0.25 mg/L for Escherichia coli , 1 mg/L for Klebsiella pneumoniae , 0.06 mg/L for Proteus mirabilis and 2 mg/L for Enterobacter cloacae . The ceftazidime/avibactam MIC 90 for 154 ceftazidime-non-susceptible isolates of Enterobacteriaceae was 1 mg/L and the ceftazidime/avibactam MIC 90 for 15 non-susceptible isolates of P. aeruginosa was 64 mg/L. There was a significant reduction in the ceftazidime/avibactam MIC relative to ceftazidime alone for most of the Enterobacteriaceae isolates. The ceftazidime/avibactam in vitro activity against these clinical urinary tract isolates demonstrates the potential utility of the drug in complicated urinary tract infections.

Stone GG ，Bradford PA ，Yates K ，Newell P ... -  《-》

Antimicrobial Activity of Ceftazidime-Avibactam against Gram-Negative Bacteria Isolated from Patients Hospitalized with Pneumonia in U.S. Medical Centers, 2011 to 2015.

Bacterial isolates were collected from patients hospitalized with pneumonia (PHP), including ventilator-associated pneumonia (VAP), from 76 U.S. medical centers in 2011 to 2015. The Gram-negative organisms (n = 11,185, including 1,097 from VAP) were tested for susceptibility to ceftazidime-avibactam and comparators by the broth microdilution method. β-Lactamase-encoding genes were screened using a microarray-based assay on selected isolates. Pseudomonas aeruginosa and Klebsiella spp. were the most common Gram-negative bacteria isolated from PHP and VAP. Ceftazidime-avibactam was very active against P. aeruginosa (n = 3,402; MIC50/MIC90, 2 and 4 μg/ml; 96.6% susceptible), including isolates nonsusceptible to meropenem (86.3% susceptible to ceftazidime-avibactam), piperacillin-tazobactam (85.6% susceptible), or ceftazidime (80.6% susceptible). Ceftazidime-avibactam was also highly active against Enterobacteriaceae (MIC50/MIC90, 0.12 and 0.5 μg/ml; 99.9% susceptible), including carbapenem-resistant Enterobacteriaceae (CRE) (n = 189; MIC50/MIC90, 0.5 and 2 μg/ml; 98.0% susceptible) and multidrug-resistant (MDR) (n = 674; MIC50/MIC90, 0.25 and 1 μg/ml; 98.8% susceptible) and extensively drug-resistant (XDR) (n = 156; MIC50/MIC90, 0.5 and 2 μg/ml; 98.1% susceptible) Enterobacteriaceae isolates, as well as Klebsiella species isolates showing an extended-spectrum β-lactamase (ESBL) screening-positive phenotype (n = 433; MIC50/MIC90, 0.25 and 1 μg/ml; 99.5% susceptible). Among Enterobacter spp. (24.8% ceftazidime nonsusceptible), 99.8% of the isolates, including 99.4% of ceftazidime-nonsusceptible isolates, were susceptible to ceftazidime-avibactam. The most common β-lactamases detected among Klebsiella pneumoniae and E. coli isolates were K. pneumoniae carbapenemase (KPC)-like and CTX-M-15, respectively. Only 8 of 6,209 Enterobacteriaceae isolates (0.1%) were ceftazidime-avibactam nonsusceptible, three NDM-1-producing strains with ceftazidime-avibactam MIC values of >32 μg/ml and five isolates with ceftazidime-avibactam MIC values of 16 μg/ml and negative results for all β-lactamases tested. Susceptibility rates among isolates from VAP were generally similar or slightly higher than those from all PHP.

Sader HS ，Castanheira M ，Flamm RK 《-》