The challenge of curbing aminoglycoside resistance: can antimicrobial stewardship programs play a critical role?

Mechanisms of Aminoglycoside- and Cisplatin-Induced Ototoxicity

Purpose This review article summarizes our current understanding of the mechanisms underlying acquired hearing loss from hospital-prescribed medications that affects as many as 1 million people each year in Western Europe and North America. Yet, there are currently no federally approved drugs to prevent or treat the debilitating and permanent hearing loss caused by the life-saving platinum-based anticancer drugs or the bactericidal aminoglycoside antibiotics. Hearing loss has long-term impacts on quality-of-life measures, especially in young children and older adults. This review article also highlights some of the current knowledge gaps regarding iatrogenic causes of hearing loss. Conclusion Further research is urgently needed to further refine clinical practice and better ameliorate iatrogenic drug-induced hearing loss.

Observed concentrations of amikacin and gentamycin in the setting of burn patients with gram-negative bacterial infections: Preliminary data from a prospective study

AIM OF THE STUDY

Critically ill populations often have shown subtherapeutic aminoglycosides' concentrations mostly because of unavoidable changes in drug volume distribution and clearance. We present a real life prospective study evaluating plasma concentrations for once-daily dosing for amikacin and gentamycin among a population of severe burn adults.

METHODS

We conducted a real life prospective study on the plasma observed concentrations of amikacin and gentamycin among severe burn patients, using aminoglycoside as combination therapy. Antibiotics were prescribed at the standard doses of 15-20mg/kg/day for amikacin and 3-5mg/kg/day for gentamycin.

RESULTS

Eight patients (4 in amikacin and 4 in gentamycin groups, respectively) were enrolled in the study. All subjects were admitted for severe burns. The most common site of infection was bloodstream (5; 62.5%) and pneumonia (4; 50%). Pseudomonas aeruginosa, followed by Klebsiella pneumoniae and multi-drug resistant Acinetobacter baumannii were the most prevalent agents isolated. Amikacin and gentamycin never achieved the target peak concentration of 60mg/L and 30mg/L: in our study C_max, for amikacin, was 33.1±15.6mg/L (SD), while for gentamycin was 14.3mg/L±9. C_max and total body surface area have shown a strong negative correlation with borderline statistical significance (amikacin: ρ=0.922, P=0.078; gentamycin: ρ=0.937, P=0.063). At the standard dosage, the pharmacokinetic/pharmacodynamic (PK/PD) target of C_max>8×highest MIC was reached for 8 (53.3%) out of 15 isolated pathogens.

CONCLUSIONS

The present study found that, in a population of septic burn patients, standard doses of gentamycin and amikacin most often lead to plasma concentrations under the PK/PD target.

A mechanistic approach to prove the efficacy of combination therapy against New Delhi metallo-β-lactamases producing bacterial strain: a molecular and biochemical approach

BACKGROUND

NDM-1 is a novel broad-spectrum metallo-β-lactamase with the capability to grant resistance to almost all β-lactam antibiotics. Its widespread dissemination made treatment options a major challenge to combat, causing threat to public health worldwide. Due to antibiotic resistance problems, development of effective therapeutics for infections caused by NDM-1 producing strains is urgently required. Since combination therapies are proved to be effective in many cases, this study was initiated to put forward novel effective antibiotics combinations for fighting infections caused by NDM-1 producing strains.

METHODS

Streptomycin and amikacin combination and streptomycin and ciprofloxacin combination were tested by checkerboard assay. NDM-1 protein/enzyme was then expressed and purified to carry out enzyme kinetics study, CD and fluorescence spectroscopic studies.

RESULTS

Streptomycin and amikacin combination and streptomycin and ciprofloxacin combination showed synergistic effect towards NDM-1 producing bacterial strains as shown by FICI results. NDM-1 producing bacterial cells were expressed and purified to obtain protein as the source of enzyme. When NDM-1 enzyme was treated with streptomycin along with amikacin, the efficiency of enzyme was decreased by 49.37% and when the enzyme was treated with streptomycin along with ciprofloxacin, the efficiency of enzyme was decreased by 29.66% as revealed by enzyme kinetic studies. Due to binding of streptomycin and amikacin in combination and streptomycin and ciprofloxacin in combination, conformational changes in the secondary structure of NDM-1 enzyme were observed by CD spectroscopic studies. Antibiotics streptomycin and ciprofloxacin bind with NDM-1 through exothermic processes, whereas amikacin binds through an endothermic process. All three antibiotics bind spontaneously with an association constant of the order of 104 M-1 as revealed by fluorescence spectroscopic studies.

CONCLUSIONS

The therapeutic combination of streptomycin with amikacin and ciprofloxacin plays an important role in inhibiting NDM-1 producing bacterial strains. Therefore, these combinations can be used as effective future therapeutic candidates against NDM-1 producing bacterial cells.

Aminoglycoside- and Cisplatin-Induced Ototoxicity: Mechanisms and Otoprotective Strategies

Ototoxicity refers to damage of inner ear structures (i.e., the cochlea and vestibule) and their function (hearing and balance) following exposure to specific in-hospital medications (i.e., aminoglycoside antibiotics, platinum-based drugs), as well as a variety of environmental or occupational exposures (e.g., metals and solvents). This review provides a narrative derived from relevant papers describing factors contributing to (or increasing the risk of) aminoglycoside and cisplatin-induced ototoxicity. We also review current strategies to protect against ototoxicity induced by these indispensable pharmacotherapeutic treatments for life-threatening infections and solid tumors. We end by highlighting several interventional strategies that are currently in development, as well as the diverse challenges that still need to be overcome to prevent drug-induced hearing loss.

Capturing antibacterial natural products with in silico techniques

The aim of the present study was to index natural products in order to facilitate the discovery of less expensive antibacterial therapeutic drugs. Thus, for modeling purposes, the present study utilized a set of 628 antibacterial drugs, representing the active domain, and 2,892 natural products, representing the inactive domain. In addition, using the iterative stochastic elimination algorithm, 36 unique filters were identified, which were then used to construct a highly discriminative and robust model tailored to index natural products for their antibacterial bioactivity. The area attained under the curve was 0.957, indicating a highly discriminative and robust prediction model. Utilizing the proposed model to virtually screen a mixed set of active and inactive substances enabled the present study to capture 72% of the antibacterial drugs in the top 1% of the sample, yielding an enrichment factor of 72. In total, 10 natural products that scored highly as antibacterial drug candidates with the proposed indexing model were reported. PubMed searches revealed that 2 molecules out of the 10 (caffeine and ricinine) have been tested and identified as showing antibacterial activity. The other 8 phytochemicals await experimental evaluation. Due to the efficiency and rapidity of the proposed prediction model, it could be applied to the virtual screening of large chemical databases to facilitate the drug discovery and development processes for antibacterial drug candidates.