Infections due to carbapenem-resistant Enterobacterales are considered urgent public health threats and often treated with a β-lactam/β-lactamase inhibitor combination. However, clinical treatment failure and resistance emergence have been attributed to inadequate dosing. We used a novel framework to provide insights of optimal dosing exposure of ceftazidime/avibactam. Seven clinical isolates of Klebsiella pneumoniae producing different KPC variants were examined. Ceftazidime susceptibility (MIC) was determined by broth dilution using escalating concentrations of avibactam. The observed MICs were characterized as response to avibactam concentrations using an inhibitory sigmoid E_max model. Using the best-fit parameter values, %fT>MIC_i was estimated for various dosing regimens of ceftazidime/avibactam. A hollow-fibre infection model (HFIM) was subsequently used to ascertain the effectiveness of selected regimens over 120 h. The drug exposure threshold associated with bacterial suppression was identified by recursive partitioning. In all scenarios, ceftazidime MIC reductions were well characterized with increasing avibactam concentrations. In HFIM, bacterial regrowth over time correlated with emergence of resistance. Overall, suppression of bacterial regrowth was associated with %fT>MIC_i ≥ 76.1% (100% versus 18.2%; P < 0.001). Using our framework, the optimal drug exposure could be achieved with ceftazidime/avibactam 2.5 g every 12 h in 5 out of 7 isolates. Furthermore, ceftazidime/avibactam 2.5 g every 8 h can suppress an isolate deemed resistant based on conventional susceptibility testing method. An optimal drug exposure to suppress KPC-producing bacteria was identified. The novel framework is informative and may be used to guide optimal dosing of other β-lactam/β-lactamase inhibitor combinations. Further in vivo investigations are warranted.

Background: Vancomycin ranks among the most utilized antimicrobial agents in the treatment of serious β-lactam–resistant gram-positive infections, but its use has been associated with nephrotoxicity. Reduction of acute kidney injury (AKI) has been reported in preclinical models with adjuvant montelukast. The purpose of the study was to ascertain if montelukast was associated with a reduction in the prevalence of vancomycin-associated AKI. Methods: This retrospective cohort study examined adult patients who received intravenous vancomycin between January 2020 and January 2024. The RIFLE criteria (risk, injury, failure, loss, and end-stage kidney disease) were employed in identifying cases of AKI. Additionally, a preclinical vancomycin-associated nephrotoxicity model was established to provide insights into possible renal protective mechanisms. Results: Patients receiving montelukast (n = 110) were compared with controls (n = 330), of which AKI was observed in 3 (2.7%) vs 35 (10.6%), respectively (P = .01). A multivariate logistic regression analysis revealed that weight (odds ratio [OR], 1.02; 95% CI, 1.006–1.03; P = .005) and intensive care unit admission (OR, 6.88; 95% CI, 2.96–18.8; P < .001) were independently associated with AKI, while montelukast (OR, 0.26; 95% CI, .06–.77; P = .03) and male gender were protective (OR, 0.41; 95% CI, .19–.85; P = .02). Our in vitro model also revealed that adjuvant montelukast can reduce injury to proximal tubule cells through activation of the p62/KEAP-1/HO-1 antioxidant pathway. Conclusions: Our study suggests that montelukast during vancomycin therapy may be protective against AKI, which may reduce patient harm and hospitalization costs. Further studies are warranted to validate our findings prospectively.

Antimicrobial resistance has been steadily increasing in prevalence, and combination therapy is commonly used to treat infections due to multidrug resistant bacteria. Under certain circumstances, combination therapy of three or more drugs may be necessary, which makes it necessary to simulate the pharmacokinetic profiles of more than two drugs concurrently in vitro. Recently, a general theoretical framework was developed to simulate three drugs with distinctly different half-lives. The objective of the study was to experimentally validate the theoretical model. Clinically relevant exposures of meropenem, ceftazidime, and ceftriaxone were simulated concurrently in a hollow-fiber infection model, with the corresponding half-lives of 1, 2.5, and 8 h, respectively. Serial samples were obtained over 24 h and drug concentrations were assayed using validated LC-MS/MS methods. A one-compartment model with zero-order input was used to characterize the observed concentration-time profiles. The experimentally observed half-lives corresponding to exponential decline of all three drugs were in good agreement with the respective values anticipated at the experiment design stage. These results were reproducible when the experiment was repeated on a different day. The validated benchtop setup can be used as a more flexible preclinical tool to explore the effectiveness of various drug combinations against multidrug resistant bacteria.

Background: Predicting oral drug absorption in humans is critical during early drug development. Current in vitro systems to predict absorption (e.g., PAMPA and MDCK cells) are lacking for certain classes of drugs. Intestinal organoids are emerging as a promising alternative that offers several potential advantages. In this study, we utilized human intestinal organoid-derived monolayers to predict oral absorption of lenalidomide. Methods: Human jejunal organoids (RepliGut^®) were cultured as monolayers on transwell plates and differentiated into intestinal epithelial cells. Lenalidomide permeability in the organoid system was compared with the permeability in the conventional Madin-Darby Canine Kidney cell (MDCK) monolayer system, as well as P-gp knockout, human P-gp overexpressing, and human BCRP overexpressing MDCK cells across a concentration range of 1 to 500 µM. Male Sprague Dawley rats were administered lenalidomide orally/intravenously, and concentrations in the serum, urine, and feces were measured and modeled in Phoenix WinNonlin. Results: Orally administered lenalidomide was well absorbed by rats at all doses (bioavailability = 68–120%). In the human jejunal organoid model, lenalidomide apparent permeability (Papp) was approximately 0.6 × 10⁻⁶ cm/s independent of the concentration used (1–500 µM). In contrast, lenalidomide Papp was significantly lower in gMDCK cell monolayers, approximately 0.2 × 10⁻⁶ cm/s. Additionally, lenalidomide was identified as a P-gp/BCRP substrate in intestinal organoids and gMDCK P-gp and BCRP overexpressing cells. Conclusions: Lenalidomide Papp was significantly lower in gMDCK monolayers than expected based on its high bioavailability. Our results suggest that organoid systems can better capture transporter and paracellularly mediated effects on drug permeability, which may allow for more accurate predictions of in vivo absorption.

Carbapenem-resistant Enterobacterales is an urgent antibiotic resistance threat [1]. In the U.S., carbapenem resistance in Enterobacterales is primarily due to the production of serine-based carbap...