In vitro evaluation of using ceftazidime/avibactam against carbapenem-resistant Acinetobacter baumannii.

OBJECTIVE: Carbapenem-resistant Acinetobacter baumannii (CRAB) is a global concern as effective treatments are very limited. We previously used a modified susceptibility testing approach to predict growth suppression in carbapenem-resistant Enterobacterales, but there are uncertainties about the generalizability of the model. The objective of this study is to verify if a similar approach can be extended to CRAB. METHOD: A clinical isolate of CRAB resistant to ceftazidime/avibactam (CAZ/AVI, MIC = 32/4 mg/L) was examined. CAZ susceptibility was determined using increasing concentrations of AVI (0-64 mg/L), and MIC reduction was characterized with a sigmoid inhibitory maximum effect (Emax) model. The effectiveness of CAZ/AVI was validated in a hollow fibre infection model (HFIM) over 72 hours, using simulated unbound serum / epithelial lining fluid (ELF) exposures of 2.5 g over 2 hours every 8 hours. Baseline inocula of approximately 5.5 log CFU/mL were examined. RESULTS: An AVI concentration-dependent reduction in CAZ MIC was observed (r2 = 0.99). CAZ MIC was dramatically reduced from 512 mg/L (no AVI) to 32 mg/L (AVI = 4 mg/L), and further to 8 mg/L (AVI = 16 mg/L). Pharmacokinetic simulations were satisfactory in the HFIM (r2 > 0.96). Bacterial suppression was observed >24 hours with the serum exposure, but not that from the ELF. CONCLUSION: Using multiple AVI concentrations within the clinically relevant range, our susceptibility testing approach could have better insights of treatment outcome for infections caused by CRAB. This could potentially lead to effective intervention(s) overlooked by conventional susceptibility testing method. This case highlights the importance of site-specific drug exposures on determining treatment outcome.

The emergence of cefiderocol resistance in Pseudomonas aeruginosa from a heteroresistant isolate during prolonged therapy.

Cefiderocol is a siderophore cephalosporin designed to target multi-drug-resistant Gram-negative bacteria. Previously, the emergence of cefiderocol non-susceptibility has been associated with mutations in the chromosomal cephalosporinase (PDC) along with mutations in the PirA and PiuA/D TonB-dependent receptor pathways. Here, we report a clinical case of cefiderocol-resistant P. aeruginosa that emerged in a patient during treatment. This resistance was associated with mutations not previously reported, suggesting potential novel pathways to cefiderocol resistance.

Optimizing antimicrobial prophylaxis strategies in acute leukemia patients: Assessing the efficacy of fluconazole.

BACKGROUND: Acute myeloid (AML) and promyelocytic (APL) leukemia patients are at high risk for infection and mortality. While guidance for infection prevention is provided by the National Comprehensive Cancer Network (NCCN) and the American Society of Clinical Oncology (ASCO), each institution may vary in antimicrobial prophylaxis prescribing practices. The discrepancy may be explained by medication intolerance, cost, and low incidence of mold infections in leukemia patients. A recent meta-analysis demonstrated mortality benefits with the use of posaconazole, which was adopted by the NCCN. Despite known risks, it is unclear whether universal mold-active coverage is indicated for all AML and APL patients. OBJECTIVE: To assess the incidence of breakthrough infections in AML and APL patients. METHODS: This was a single-center, retrospective chart review of AML and APL patients receiving induction therapy at Baylor St Luke's Medical Center (BSLMC) between January 2019 and October 2021. The primary outcome assessed the incidence of breakthrough infections. Descriptive statistics were used to summarize the data. RESULTS: A total of 55 patients were included and 54 (98%) had prolonged neutropenia with a median duration of 30 days. Five patients (9.3%) experienced breakthrough infections during induction while 21 individuals (38.9%) during the follow-up period. Aspergillus infections occurred in three patients receiving nonmold coverage compared to none on mold-active agents (p = 1.0) with no statistical difference in mortality. CONCLUSION: Despite the majority of patients not receiving mold-active prophylaxis, nonmold-active prophylaxis may be sufficient with consideration of low aspergillosis incidence.

Significant Publications on Infectious Diseases Pharmacotherapy in 2022.

Purpose: To provide summarization of the most significant infectious diseases (ID) pharmacotherapy articles published in peer-reviewed literature in 2022. Summary: Members of the Houston Infectious Diseases Network (HIDN) nominated notable articles providing significant contributions to ID pharmacotherapy in 2022. Article nominations included those pertaining to general ID, as well as those including coronavirus disease 2019 (COVID-19), and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) pharmacotherapy. A total of 71 articles were nominated by HIDN. Members: 68 articles pertaining to general ID pharmacotherapy and 3 articles focusing on HIV/AIDS. To aid selection of the most these most notable articles of 2022, a survey was created and distributed to members of the Society of Infectious Diseases Pharmacists (SIDP). Of the 153 SIDP members who participated in the survey, there were 128 recorded votes for the top 10 general ID pharmacotherapy articles and 30 votes recorded for the top HIV/AIDS article. The most notable publications are summarized. Conclusion: Post pandemic significant advances in antimicrobial stewardship and infectious disease states continues to occur in a world recently focused on the coronavirus disease 2019 (COVID-19) global pandemic. Continuous growth in publication of ID-related articles over the past year lends towards the aims of this review to aid clinicians in remaining current on key practice-changing ID pharmacotherapy publications from 2022.