Elevated MICs of Susceptible Anti-Pseudomonal Cephalosporins in Non-Carbapenemase-Producing, Carbapenem-Resistant Pseudomonas aeruginosa: Implications for Dose Optimization

Piperacillin/Tazobactam Dose Optimization in the Setting of Piperacillin/Tazobactam-susceptible, Carbapenem-resistant Pseudomonas aeruginosa: Time to Reconsider Susceptible Dose Dependent

PURPOSE

This study evaluates the in vitro potency of piperacillin/tazobactam among a global collection of carbapenem-resistant Pseudomonas aeruginosa (CR-PA) and assesses the adequacy of the Clinical and Laboratory Standards Institute (CLSI) P aeruginosa breakpoint dose in the setting of CR-PA using Monte Carlo simulation.

METHODS

Isolates were collected during the Enhancing Rational Antimicrobials Against Carbapenem-Resistant P aeruginosa (ERACE-PA) Global Surveillance Program. Piperacillin/tazobactam MICs were determined using broth microdilution per CLSI standards. A 5000-patient Monte Carlo simulation was performed using various piperacillin/tazobactam dosing regimens to determine the probability of target attainment (PTA) for 50% free time above the MIC. The MIC distribution of piperacillin/tazobactam-susceptible CR-PA was used to calculate cumulative fraction of response (CFR). Optimal PTA and CFR were defined as 90% target achievement.

FINDINGS

A total of 28% of tested CR-PA were piperacillin/tazobactam susceptible. Of these, 71% had MICs of 8 to 16/4 mg/L. Doses of 3.375 g q6h as 0.5-hour infusion (current breakpoint dose) had adequate PTA at MIC of 8/4 mg/L (CFR, 81%); however, extended infusion of 3 or 4 hours improved PTA at 16/4 mg/L (CFR, >90%). Doses of 4.5 g q8h as a 4-hour infusion and 4.5 g q6h as a 3-hour infusion both provide >90% PTA at an MIC of 16 mg/L (CFRs, 97 and 100%, respectively), favoring susceptible dose dependent interpretive criteria with these regimens.

IMPLICATIONS

Although susceptible, piperacillin/ tazobactam has reduced potency in CR-PA. If piperacillin/tazobactam is used for susceptible CR-PA, high-doses (4.5 g q6h) and extended infusion (3 hours or continuous infusion) are needed to optimize exposure.

Carbapenem-resistant Pseudomonas aeruginosa: an assessment of frequency of isolation from ICU versus non-ICU, phenotypic and genotypic profiles in a multinational population of hospitalized patients

BACKGROUND

Historically, multi-drug resistant organisms have been associated with the ICU setting. The present study sought to define the frequency of isolation from ICU versus non-ICU, phenotypic and genotypic profiles of carbapenem-resistant Pseudomonas aeruginosa (CR-PA) from a global cohort.

METHODS

Multicenter surveillance study (17 centers from 12 countries) including 672 CR-PA isolates from 2019 to 2021. Phenotypic carbapenemase testing was assessed. Genotypic carbapenemase testing was conducted (CarbaR and CarbaR NxG) to detect β-lactamases. Broth microdilution MICs were established for ceftazidime, cefepime, ceftolozane/tazobactam, and ceftazidime/avibactam.

RESULTS

59% of CR-PA were isolated from patients outside the ICU. The most common source in ICU and non-ICU patients was respiratory (55% and 30%, respectively). In the ICU, 35% of isolates were phenotypically carbapenemase-positive versus 29% for non-ICU. VIM was the most common carbapenemase (54% and 44%, respectively) followed by GES (27% and 28%, respectively). Susceptibility to ceftazidime or cefepime were relatively low in ICU (39% and 41% of isolates, respectively) and non-ICU (47% and 52% of isolates, respectively). Ceftolozane/tazobactam and ceftazidime/avibactam were more active with 56% and 66% of isolates susceptible in the ICU while 65% and 76% in non-ICU, respectively. When carbapenemase-negative, 86% and 88% of ICU isolates were susceptible to ceftolozane/tazobactam and ceftazidime/avibactam. Similarly, in the carbapenemase-negative, non-ICU isolates 88% and 92% of isolates were susceptible, respectively.

CONCLUSION

Although multidrug resistant pathogens are often regarded as a challenge in the ICU population, the majority of CR-PA were isolated from non-ICU patients. Implementing phenotypic/genotypic testing will assist in guiding treatment. Carbapenem-resistance in P. aeruginosa should be regarded as a surrogate for MDR and this phenotype is increasingly prevalent outside the ICU.

Infectious Diseases Society of America 2022 Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. The initial guidance document on infections caused by extended-spectrum β-lactamase producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa) was published on 17 September 2020. Over the past year, there have been a number of important publications furthering our understanding of the management of ESBL-E, CRE, and DTR-P. aeruginosa infections, prompting a rereview of the literature and this updated guidance document.

METHODS

A panel of 6 infectious diseases specialists with expertise in managing antimicrobial-resistant infections reviewed, updated, and expanded previously developed questions and recommendations about the treatment of ESBL-E, CRE, and DTR-P. aeruginosa infections. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment recommendations are provided with accompanying rationales, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Recommendations apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of 24 October 2021. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance/.

Pharmacokinetic/Pharmacodynamic Optimization of Hospital-Acquired and Ventilator-Associated Pneumonia: Challenges and Strategies

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are correlated with high mortality rates worldwide. Thus, the administration of antibiotic therapy with appropriate dosing regimen is critical. An efficient antibiotic is needed to maintain an adequate concentration at the infection site, for a sufficient period of time, to achieve the best therapeutic outcome. It can, however, be challenging for antibiotics to penetrate the pulmonary system due to the complexity of its structure. Crossing the blood alveolar barrier is a difficult process determined by multiple factors that are either drug related or infection related. Thus, the understanding of pharmacokinetics/pharmacodynamics (PK/PD) of antibiotics identifies the optimum dosing regimens to achieve drug penetration into the epithelial lining fluid at adequate therapeutic concentrations. Critically ill patients in the ICU can express augmented renal clearance (ARC), characterized by enhanced renal function, or may have renal dysfunction necessitating supportive care such as continuous renal replacement therapy (CRRT). Both ARC and CRRT can alter drug elimination, thus affecting drug concentrations. PK of critically ill patients is less clear due to the multiple variabilities associated with their condition. Therefore, conventional dosing regimens often lead to therapeutic failure. Another major hurdle faced in optimizing treatment for HAP/VAP is the reduction of the in vitro potency. Therapeutic drug monitoring (TDM), if available, may allow health care providers to personalize treatment to maximize efficacy of the drug exposures while minimizing toxicity. TDM can be of significant importance in populations whom PK are less defined and for resistant infections to achieve the best therapeutic outcome.