In vitro Activity of a New Fourth-Generation Cephalosporin, Cefoselis, Against Clinically Important Bacterial Pathogens in China

In Vitro Activities of Aztreonam-Avibactam, Eravacycline, Cefoselis, and Other Comparators against Clinical Enterobacterales Isolates: a Multicenter Study in China, 2019

Aztreonam-avibactam, eravacycline, and cefoselis are three novel antimicrobial agents for the treatment of serious infections caused by Gram-negative bacteria. We evaluated the in vitro activities of the above-mentioned three antimicrobial agents against clinical Enterobacterales isolates. A total of 1,202 Enterobacterales isolates, including 10 genera or species, were collected from 26 hospitals that cover seven regions of China. The susceptibilities of the 30 antimicrobial agents were interpreted based on the combination of U.S. Food and Drug Administration and Clinical and Laboratory Standards Institute guidelines. The results indicated that all Enterobacterales isolates showed high susceptibility to aztreonam-avibactam (98.25%), eravacycline (85.69%), and cefoselis (62.73%). The first two antimicrobial agents also demonstrated potent activities against multidrug-resistant and carbapenem-resistant Enterobacterales independent of antimicrobial resistance mechanisms. The rates of susceptibility to aztreonam-avibactam, eravacycline, and cefoselis were lowest in Morganella spp. (84.42%), Proteus spp. (33.65%), and Escherichia coli (40.14%), respectively. In general, the lower rates of susceptibility to eravacycline and cefoselis were in the older inpatient group. The strains isolated from urinary tract exhibited the lowest rate of susceptibility (78.97%) to eravacycline, and the lowest rate of susceptibility (45.83%) to cefoselis was observed in nervous system specimens. The strains isolated from intensive care unit (ICU) wards showed significantly reduced susceptibility to cefoselis compared with those isolated from non-ICU wards. The MIC values of aztreonam-avibactam and ceftazidime-avibactam have poor consistency (weighted kappa = 0.243), as did eravacycline and tigecycline (weighted kappa = 0.478). Cefoselis and cefepime showed highly similar activities against Enterobacterales (weighted kappa = 0.801). Our results support the clinical development of aztreonam-avibactam, eravacycline, and cefoselis to treat infections caused by Enterobacterales. IMPORTANCE Infections caused by multidrug-resistant (MDR) Enterobacterales, especially carbapenem-resistant Enterobacterales (CRE), have been a challenging clinical problem due to the limited therapeutic options. Therefore, the need to develop novel antimicrobial agents and evaluate their activities against Enterobacterales in vitro is urgent. Our results show that the novel antimicrobial agents aztreonam-avibactam and eravacycline retain activities against MDR and CRE isolates, including carbapenemase producers and non-carbapenemase producers. Further analysis combined with clinical information on the strains tested revealed that no significant differences were observed in susceptibility rates of strains with different demographic parameters to aztreonam-avibactam. Age, specimen source, and department were associated with the susceptibility of strains to eravacycline and cefoselis (P ≤ 0.01). Compared with ceftazidime-avibactam, aztreonam-avibactam has its advantages and limitations against Enterobacterales. The potent activity of eravacycline against Enterobacterales was higher than that of tigecycline. Cefoselis and cefepime showed a highly consistent activity against Enterobacterales.

Establishment of epidemiological cut-off values for cefoselis, a new fourth-generation cephalosporin, against Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Proteus mirabilis and Pseudomonas aeruginosa

OBJECTIVES

To establish the epidemiological cut-off values (ECOFFs) for cefoselis against Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Proteus mirabilis and Pseudomonas aeruginosa.

METHODS

We collected 2288 non-repetitive clinical isolates from five laboratories throughout four cities in China. The cefoselis MICs and inhibition zone diameters for all isolates were established using the broth microdilution method and the disc diffusion method following EUCAST guidelines. MIC ECOFFs were determined by visual estimation and ECOFFinder software. Zone diameter ECOFFs were set if a high correlation of MICs and inhibition zone diameters was found by Pearson correlation. Zone diameter ECOFFs were finally determined by the visual estimate method.

RESULTS

MICs of cefoselis were distributed from 0.008 to >256 mg/L for the four Enterobacterales species and from 0.25 to >256 mg/L for P. aeruginosa. MIC ECOFFs were 0.125 mg/L for E. coli, K. pneumoniae and P. mirabilis, 0.25 mg/L for E. cloacae and 32 mg/L for P. aeruginosa. A high correlation of MICs and zone diameters was observed for all Enterobacterales (|r| > 0.8, P < 0.001) and a relatively high correlation was found for P. aeruginosa (|r| = 0.71, P < 0.001). The zone diameter ECOFF was 24 mm for E. cloacae, E. coli and K. pneumoniae, 26 mm for P. mirabilis and 21 mm for P. aeruginosa.

CONCLUSIONS

We determined MIC and zone diameter ECOFFs for cefoselis against four Enterobacterales species and P. aeruginosa. The establishment of ECOFFs for cefoselis provides clinicians with helpful guidance to differentiate WT and non-WT pathogens.