Minimizing the toxicity of aminoglycosides in cystic fibrosis

Personalized tobramycin dosing in children with cystic fibrosis: a comparative clinical evaluation of log-linear and Bayesian methods

BACKGROUND

Children with cystic fibrosis (CF) pulmonary exacerbations receive IV tobramycin therapy, with dosing guided by either log-linear regression (LLR) or Bayesian forecasting (BF).

OBJECTIVES

To compare clinical and performance outcomes for LLR and BF.

PATIENTS AND METHODS

A quasi-experimental intervention study was conducted at a tertiary children's hospital. Electronic medical records were extracted (from January 2015 to September 2021) to establish a database consisting of pre-intervention (LLR) and post-intervention (BF) patient admissions and relevant outcomes. All consecutive patients treated with IV tobramycin for CF pulmonary exacerbations guided by either LLR or BF were eligible.

RESULTS

A total of 376 hospital admissions (LLR = 248, BF = 128) for CF pulmonary exacerbations were included. Patient demographics were similar between cohorts. There were no significant differences found in overall hospital length of stay, rates of re-admission within 1 month of discharge or change in forced expiratory volume in the first second (Δ FEV1) at the end of tobramycin treatment. Patients treated with LLR on average had twice the number of therapeutic drug monitoring (TDM) blood samples collected during a single hospital admission. The timeframe for blood sampling was more flexible with BF, with TDM samples collected up to 16 h post-tobramycin dose compared with 10 h for LLR. The tobramycin AUC0-24 target of ≥100 mg/L·h was more frequently attained using BF (72%; 92/128) compared with LLR (50%; 124/248) (P < 0.001). Incidence of acute kidney injury was rare in both groups.

CONCLUSIONS

LLR and BF result in comparable clinical outcomes. However, BF can significantly reduce the number of blood collections required during each admission, improve dosing accuracy, and provide more reliable target concentration attainment in CF children.

Liquid Crystal Nanoparticles Enhance Tobramycin Efficacy in a Murine Model of Pseudomonas aeruginosa Biofilm Wound Infection

Chronic Pseudomonas aeruginosa wound infections are highly prevalent and often untreatable due to biofilm formation, resulting in high antimicrobial tolerance. Standard antibiotic therapy for P. aeruginosa infections involves tobramycin, yet it is highly ineffective as monotherapy as tobramycin cannot penetrate the biofilm to elicit its antimicrobial effect. Lipid liquid crystal nanoparticles (LCNPs) have previously been shown to increase the antimicrobial efficacy and penetration of tobramycin against P. aeruginosa biofilms in vitro and ex vivo. Here, for the first time, we have developed a chronic P. aeruginosa biofilm infection in full-thickness wounds in mice to examine the potential of LCNPs to improve the effect of tobramycin, preclinically. After three doses, administered once a day, tobramycin-LCNPs significantly reduced the P. aeruginosa bacterial load in murine wounds 1000-fold more than unformulated tobramycin, which in turn showed no significant difference to the saline control treatment. Consistent with the improved P. aeruginosa eradication, the tobramycin-LCNPs promoted wound healing. In comparison to previous in vitro and ex vivo data, we show a strong in vitro-in vivo correlation between P. aeruginosa biofilm infection models. The enhanced activity of tobramycin-LCNPs in vivo in the preclinical murine model demonstrates the strong potential of LCNPs as a next-generation formulation approach to improve the efficacy of tobramycin against P. aeruginosa biofilm wound infections.

Tobramycin Liquid Crystal Nanoparticles Eradicate Cystic Fibrosis-Related Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa biofilms cause persistent and chronic infections, most known clinically in cystic fibrosis (CF). Tobramycin (TOB) is a standard anti-pseudomonal antibiotic; however, in biofilm infections, its efficacy severely decreases due to limited permeability across the biofilm matrix. Herewith, a biomimetic, nanostructured, lipid liquid crystal nanoparticle-(LCNP)-formulation is discovered to significantly enhance the efficacy of TOB and eradicate P. aeruginosa biofilm infections. Using an advanced, biologically-relevant co-culture model of human CF bronchial epithelial cells infected with P. aeruginosa biofilms at an air-liquid interface, nebulized TOB-LCNPs completely eradicated 1 × 10⁹ CFU mL^-1 of P. aeruginosa after two doses, a 100-fold improvement over the unformulated antibiotic. The enhanced activity of TOB is not observed with a liposomal formulation of TOB or with ciprofloxacin, an antibiotic that readily penetrates biofilms. It is demonstrated that the unique nanostructure of the LCNPs drives the enhanced penetration of TOB across the biofilm barrier, but not through the healthy lung epithelium barrier, significantly increasing the available antibiotic concentration at the site of infection. The LCNPs are an innovative strategy to improve the performance of TOB as a directed pulmonary therapy, enabling the administration of lower doses, reducing the toxicity, and amplifying the anti-biofilm activity of the anti-pseudomonal antibiotic.

Chlortetracycline-Functionalized Silver Nanoparticles as a Colorimetric Probe for Aminoglycosides: Ultrasensitive Determination of Kanamycin and Streptomycin

Aminoglycosides (AMGs) have been extensively used to treat infectious diseases caused by Gram-negative bacteria in livestock and humans. A selective and sensitive colorimetric probe for the determination of streptomycin and kanamycin was proposed based on chlortetracycline-coated silver nanoparticles (AgNPs-CTC) as the sensing element. Almost all of the tested aminoglycoside antibiotics can rapidly induce the aggregation of AgNPs, along with a color change from yellow to orange/red. The selective detection of aminoglycoside antibiotics, including tobramycin, streptomycin, amikacin, gentamicin, neomycin, and kanamycin, with other types of antibiotics, can be achieved by ultraviolet (UV) spectroscopy. This developed colorimetric assay has ability to detect various AMGs using in-depth surface plasmon resonance (SPR) studies. With this determination of streptomycin and kanamycin was achieved at the picomolar level (pM) by using a UV-visible spectrophotometer. Under aqueous conditions, the linear range of the colorimetric sensor for streptomycin and kanamycin was 1000-1,1000 and 120-480 pM, respectively. The corresponding limit of detection was 2000 pM and 120 pM, respectively. Thus, the validated dual colorimetric and ratiometric method can find various analytical applications for the ultrasensitive and rapid detection of AMG antibiotics in water samples.

High-frequency audiometry reveals high prevalence of aminoglycoside ototoxicity in children with cystic fibrosis

BACKGROUND

Intravenous aminoglycoside (IV AG) antibiotics, widely used in patients with cystic fibrosis (CF), are known to have ototoxic complications. Despite this, audiological monitoring is not commonly performed and if performed, uses only standard pure-tone audiometry (PTA). The aim of this study was to investigate ototoxicity in CF children, to determine the most appropriate audiological tests and to identify possible risk factors.

METHODS

Auditory assessment was performed in CF children using standard pure tone audiometry (PTA), extended high-frequency (EHF) audiometry and distortion-product otoacoustic emissions (DPOAE).

RESULTS

70 CF children, mean (SD) age 10.7 (3.5) years, were recruited. Of the 63 children who received IV AG, 15 (24%) children had ototoxicity detected by EHF audiometry and DPOAE. Standard PTA only detected ototoxicity in 13 children. Eleven of these children had received at least 10 courses of IV AG courses. A 25 to 85 dBHL hearing loss (mean±SD: 57.5±25.7 dBHL) across all EHF frequencies and a significant drop in DPOAE amplitudes at frequencies 4 to 8 kHz were detected. However, standard PTA detected a significant hearing loss (>20 dBHL) only at 8 kHz in 5 of these 15 children and none in 2 subjects who had significantly elevated EHF thresholds. The number of courses of IV AG received, age and lower lung function were shown to be risk factors for ototoxicity.

CONCLUSIONS

CF children who had received at least 10 courses of IV AG had a higher risk of ototoxicity. EHF audiometry identified 2 more children with ototoxicity than standard PTA and depending on facilities available, should be the test of choice for detecting ototoxicity in children with CF receiving IV AG.