Comparative pharmacodynamics and antimutant potentials of doripenem and imipenem with ciprofloxacin-resistant Pseudomonas aeruginosa in an in vitro model

Testing the mutant selection window hypothesis with meropenem: In vitro model study with OXA-48-producing Klebsiella pneumoniae

OXA-48 carbapenemases are frequently expressed by Klebsiella pneumoniae clinical isolates; they decrease the effectiveness of carbapenem therapy, particularly with meropenem. Among these isolates, meropenem-susceptible carbapenemase-producers may show decreased meropenem effectiveness. However, the probability of the emergence of resistance in susceptible carbapenemase-producing isolates and its dependence on specific K. pneumoniae meropenem MICs is not completely known. It is also not completely clear what resistance patterns will be exhibited by these bacteria exposed to meropenem, if they would follow the patterns of non-beta-lactamase-producing bacteria and other than beta-lactams antibiotics. These issues might be clarified if patterns of meropenem resistance related to the mutant selection window (MSW) hypothesis. To test the applicability of the MSW hypothesis to meropenem, OXA-48-carbapenemase-producing K. pneumoniae clinical isolates with MICs in a 64-fold range (from susceptible to resistant) were exposed to meropenem in a hollow-fiber infection model; epithelial lining fluid meropenem pharmacokinetics were simulated following administration of 2 grams every 8 hours in a 3-hour infusion. Strong bell-shaped relationships between the meropenem daily dose infused to the model as related to the specific isolate MIC and both the antimicrobial effect and the emergence of resistance were observed. The applicability of the MSW hypothesis to meropenem and carbapenemase producing K. pneumoniae was confirmed. Low meropenem efficacy indicates very careful prescribing of meropenem to treat K. pneumoniae infections when the causative isolate is confirmed as an OXA-48-carbapenemase producer.

Pseudomonas aeruginosa Susceptibility in Spain: Antimicrobial Activity and Resistance Suppression Evaluation by PK/PD Analysis

Pseudomonas aeruginosa remains one of the major causes of healthcare-associated infection in Europe; in 2019, 12.5% of invasive isolates of P. aeruginosa in Spain presented combined resistance to ≥3 antimicrobial groups. The Spanish nationwide survey on P. aeruginosa antimicrobial resistance mechanisms and molecular epidemiology was published in 2019. Based on the information from this survey, the objective of this work was to analyze the overall antimicrobial activity of the antipseudomonal antibiotics considering pharmacokinetic/pharmacodynamic (PK/PD) analysis. The role of PK/PD to prevent or minimize resistance emergence was also evaluated. A 10,000-subject Monte Carlo simulation was executed to calculate the probability of target attainment (PTA) and the cumulative fraction of response (CFR) considering the minimum inhibitory concentration (MIC) distribution of bacteria isolated in ICU or medical wards, and distinguishing between sample types (respiratory and non-respiratory). Ceftazidime/avibactam followed by ceftolozane/tazobactam and colistin, categorized as the Reserve by the Access, Watch, Reserve (AWaRe) classification of the World Health Organization, were the most active antimicrobials, with differences depending on the admission service, sample type, and dose regimen. Discrepancies between EUCAST-susceptibility breakpoints for P. aeruginosa and those estimated by PK/PD analysis were detected. Only standard doses of ceftazidime/avibactam and ceftolozane/tazobactam provided drug concentrations associated with resistance suppression.

The Efficacy and Safety of Doripenem in the Treatment of Acute Bacterial Infections-A Systemic Review and Meta-Analysis of Randomized Controlled Trials

This study aims to assess the efficacy and safety of doripenem on treating patients with acute bacterial infections. The Pubmed, Embase, and Cochrane databases were searched up to April 2019. Only randomized clinical trials comparing doripenem and other comparators for the treatment of acute bacterial infection were included. The primary outcome was the clinical success rate and the secondary outcomes were microbiological eradication rate and risk of adverse events. Eight randomized controlled trials (RCTs) were included. Overall, doripenem had a similar clinical success rate with comparators (odds ratio [OR], 1.15; 95% CI, 0.79-1.66, I2 = 58%). Similar clinical success rates were noted between doripenem and comparators for pneumonia (OR, 0.84; 95% CI, 0.46-1.53, I² = 72%) and for intra-abdominal infections (OR, 1.00; 95% CI, 0.57-1.72). For complicated urinary tract infection, doripenem was associated with higher success rate than comparators (OR, 1.89, 95% CI, 1.13-3.17, I² = 0%). The pool analysis comparing doripenem and other carbapenems showed no significant differences between each other (OR, 0.96, 95% CI, 0.59-1.58, I² = 63%). Doripenem also had a similar microbiological eradication rate with comparators (OR, 1.08; 95% CI, 0.86-1.36, I² = 0%). Finally, doripenem had a similar risk of treatment-emergent adverse events as comparators (OR, 0.98; 95% CI, 0.83-1.17, I² = 33%). In conclusion, the clinical efficacy of doripenem is as high as that of the comparator drugs in the treatment of acute bacterial infection; furthermore, this antibiotic is as well tolerated as the comparators.

Comparative activities of selected fluoroquinolones against dynamic populations of Actinobacillus pleuropneumoniae in an in vitro model of time-kill continuous culture experiment

The aim of the current study was to demonstrate and compare the impact of different pharmacokinetics of marbofloxacin, enrofloxacin and difloxacin on their antimicrobial effects, their killing and re-growth kinetics, and the population dynamics of Actinobacillus pleuropneumoniae clinical isolates in an in vitro dynamic model. Selected clinical isolates of A. pleuropneumoniae and three fluoroquinolones at a range of simulated AUC(24)/MIC ratios of multiple doses were investigated. At the same simulated AUC(24)/MIC ratios of the three fluoroquinolones, the killing re-growth profile and I(E) values (intensity of the antimicrobial effect) revealed strain- and fluoroquinolone-specific effects. For example, a 31% lower I(E) of difloxacin was observed in AppK5 (biofilm-former) than in AppK2 (biofilm-non-former) at the same AUC(24)/MIC ratio of 120 h. In addition, losses in A. pleuropneumoniae susceptibility of both strains by the three fluoroquinolones were observed. AUC(24)/MPC ratios of 20.89 and 39.81 for marbofloxacin, 17.32 and 19.49 for enrofloxacin and 31.62 and 60.25 for difloxacin were estimated to be protective against the selection of AppK2 and AppK5 strain mutants, respectively. Integration of these in vitro data with published pharmacokinetics revealed the inadequacy of the conventional clinical doses of the three drugs to attain the above protective values for minimum biofilm eradication concentration (MBEC) and concentration to prevent growth of 90% of the mutant subpopulation (MPC(90)). In conclusion, the results suggest optimising doses could suffice for resistant mutants control, while for biofilm-forming strains combination with biofilm-disrupting agents to reduce the MBEC to achieve AUC/MBEC ratios within the possible dosing regimens is desired.

Concentration-resistance relationships with Pseudomonas aeruginosa exposed to doripenem and ciprofloxacin in an in vitro model

OBJECTIVES

To compare the abilities of doripenem and ciprofloxacin to restrict the enrichment of resistant Pseudomonas aeruginosa, multiple antibiotic dosing regimens were simulated in an in vitro model at comparable ratios of the 24 h AUC (AUC24) to the MIC.

METHODS

Three clinical isolates of ciprofloxacin-resistant P. aeruginosa (MIC of doripenem 1 mg/L, MIC of ciprofloxacin 4 mg/L) were exposed to thrice-daily doripenem or twice-daily ciprofloxacin for 3 days at AUC24/MIC ratios from 50 to 170 h (doripenem) and from 55 to 180 h (ciprofloxacin).

RESULTS

Doripenem- and ciprofloxacin-resistant mutants were enriched at antibiotic concentrations that fell into the mutant selection window for ≥ 45% and ≥ 60% of the dosing interval, respectively. The anti-mutant effects of doripenem and ciprofloxacin expressed by the area under the bacterial mutant concentration-time curve (AUBCM) depended on the AUC24/MIC ratio, and the AUBCM-log AUC24/MIC relationships were antibiotic specific.

CONCLUSION

Based on AUC24/MIC relationships with AUBCM, a greater anti-mutant potential was predicted for doripenem compared with ciprofloxacin.