Aminoglycoside Concentrations Research Articles

High-pH mobile phase in reversed-phase liquid chromatography-tandem mass spectrometry to improve the separation efficiency of aminoglycoside isomers.

In chromatography, the use of extreme conditions can often lead to unique separation selectivity. In this study, a highly basic mobile phase (pH > 11), which is not typically employed for reversed-phase liquid chromatography (RPLC), was utilized in RPLC-tandem mass spectrometry (MS/MS) to achieve effective separation between electrically neutral bases of aminoglycosides (AGs). A mixture of AGs was simultaneously analyzed using 500mmol L-1 ammonia aqueous solution (pH 11.8) as the mobile phase. A total of 11 AGs, including 2 stereoisomers of neomycin (B and C) and 5 structurally similar components of gentamicin (C1, C1a, C2, C2a, and C2b), were completely separated for the first time. The high separation performance for AGs was mainly due to two factors: First, slight differences in hydrophobicity among the AGs were significantly enhanced at a high pH by the complete acid dissociation of amines. Second, the high pH of the mobile phase minimized any electrostatic interactions between the AGs and residual silanol groups in the stationary phase, resulting in extremely sharp peaks for the AGs. The sensitivity of spectinomycin decreased by more than 20% when using the highly basic mobile phase (pH 11.8) due to its degradation, therefore, a mixture of 10 AGs was analyzed with 250mmol L-1 ammonia aqueous solution (pH 11.5) with less degradation as the optimum condition. The developed analytical method could be used to determine the concentrations of trace AGs in milk with high accuracy and precision. Thus, RPLC-MS/MS using a high-pH mobile phase has great potential for the efficient separation of basic compounds containing amino sugars such as AGs.

RavA-ViaA antibiotic response is linked to Cpx and Zra2 envelope stress systems in Vibrio cholerae.

The RavA-ViaA complex was previously found to sensitize Escherichia coli to aminoglycosides (AGs) in anaerobic conditions, but the mechanism is unknown. AGs are antibiotics known for their high efficiency against Gram-negative bacteria. In order to elucidate how the expression of the ravA-viaA genes increases bacterial susceptibility to aminoglycosides, we aimed at identifying partner functions necessary for increased tolerance in the absence of RavA-ViaA, in Vibrio cholerae. We show that membrane stress response systems Cpx and Zra2 are required in the absence of RavA-ViaA, for the tolerance to AGs and for outer membrane integrity. In the absence of these systems, the ∆ravvia strain's membrane becomes permeable to external agents such as the antibiotic vancomycin.

Comparison of Gold Nanoparticles Prepared Using Monobasic Sodium Citrate or Sodium Borohydride for Neomycin Determination in Saliva after Solid-Phase Extraction (SPE) on a Molecularly Imprinted Polymer (MIP)

Two distinct spherical gold nanoparticles (AuNPs) were compared for the spectrophotometric determination of neomycin in saliva. The AuNPs were produced using AuCl3 and monobasic sodium citrate (in water bath at 100 °C) under magnetic stirring (AuNPs-citrate) and using HAuCl4 and NaBH4, at room-temperature under mechanical agitation in a commercial reactor (AuNPs-H). Both AuNPs were spherical with diameters of 7.7 nm (AuNPs-H) and 26.1 nm (AuNPs-citrate) and the maximum wavelength of the localized surface plasmon resonance (LSPR) bands were at 511 nm (AuNPs-H) and 529 nm (AuNPs-citrate). Equivalent spectral extinctions were found despite the fact the large difference in concentrations of AuNPs in dispersions: 4.2 × 10−9 mol L−1 for the AuNPs-H and 8.7 × 10−11 mol L−1 for the AuNPs-citrate. Both AuNPs interacted with aminoglycosides (AMG), affecting intensity of the LSPR band as the concentration of AMG increased. The response of the AuNPs-H was more sensitive toward AMG covering the following ranges: 0.6–600 µg L−1 (gentamicin), 7.3–550 µg L−1 (neomycin) and 14–520 µg L−1 (kanamycin). AuNPs-H optical response was more robust in function of the pH with AuNPs-citrate response only observed in acid solution, favoring electrostatic interaction with AMG. Catalytic activity of AuNPs-H, in reducing the 4-phenolate ion, presented a higher rate constant (4.3 × 10−3 s−1) and was used as analytical probe to determine neomycin in saliva after solid phase extraction with a commercially available AMG imprinted polymer enabling quantification to 0.36 μg of the analyte.

Effect of Phenylalanine–Arginine Beta-Naphthylamide on the Values of Minimum Inhibitory Concentration of Quinolones and Aminoglycosides in Clinical Isolates of Acinetobacter baumannii

(1) Background: Acinetobacter baumannii has become the most important pathogen responsible for nosocomial infections in health systems. It expresses several resistance mechanisms, including the production of β-lactamases, changes in the cell membrane, and the expression of efflux pumps. (2) Methods: A. baumannii was detected by PCR amplification of the blaOXA-51-like gene. Antimicrobial susceptibility to fluoroquinolones and aminoglycosides was assessed using the broth microdilution technique according to 2018 CLSI guidelines. Efflux pump system activity was assessed by the addition of a phenylalanine–arginine beta-naphthylamide (PAβN) inhibitor. (3) Results: A total of nineteen A. baumannii clinical isolates were included in the study. In an overall analysis, in the presence of PAβN, amikacin susceptibility rates changed from 84.2% to 100%; regarding tobramycin, they changed from 68.4% to 84.2%; for nalidixic acid, they changed from 73.7% to 79.0%; as per ciprofloxacin, they changed from 68.4% to 73.7%; and, for levofloxacin, they stayed as 79.0% in both groups. (4) Conclusions: The addition of PAβN demonstrated a decrease in the rates of resistance to antimicrobials from the family of quinolones and aminoglycosides. Efflux pumps play an important role in the emergence of multidrug-resistant A. baumannii strains, and their inhibition may be useful as adjunctive therapy against this pathogen.

Evaluation of Dosing Regimens of Vancomycin and Aminoglycosides in Pediatric Patients on Continuous Renal Replacement Therapy.

To determine the optimal empiric dosing regimen to achieve therapeutic serum concentrations of vancomycin and aminoglycosides in pediatric patients who are receiving continuous renal replacement therapy (CRRT). This retrospective study investigated pediatric patients (<18 years old) who received at least one dose of an aminoglycoside and/or vancomycin while on CRRT and who had at least one serum concentration assessed during the study period. Rates of culture clearance and discontinuation of renal replacement therapy, pharmacokinetic variables (i.e., volume of distribution [Vd], half-life [t½], rate of elimination [ke]), and correlations between patient's age and weight in regard to the empiric dosing regimen were evaluated. Forty-three patients were included in this study. The median dose required to reach therapeutic serum concentrations for vancomycin was 17.6 mg/kg (12.8-20.4 mg/kg) every 12 hours (6-30 hours) in continuous venovenous hemodialysis (CVVHD) patients and 16.3 mg/kg (13.9-21.4 mg/kg) every 12 hours (6-24 hours) in continuous venovenous hemodiafiltration (CVVHDF) patients. The median dose for aminoglycosides was unable to be determined. In CVVHD patients, the median vancomycin ke was 0.04 hr-1, t½ was 18 hours, and Vd was 1.6 L/kg. In CVVHDF patients, the median vancomycin ke was 0.05 hr-1, t½ was 14 hours, and Vd was 0.6 L/kg. No correlation was found between age and weight with regard to effective dosing regimen. To achieve therapeutic trough concentrations in pediatric patients on CRRT, vancomycin should be dosed at approximately 17.5 mg/kg administered every 12 hours.

Intravesical aminoglycoside instillations as prophylaxis for recurrent urinary tract infection: patient satisfaction, long-term safety and efficacy.

Recurrent urinary tract infections (UTIs) are common, especially in women. When oral antimicrobial prophylaxis is ineffective or not possible due to allergies or antimicrobial resistance, intravesical aminoglycoside instillations (IAIs) are a non-systemic alternative. To assess treatment satisfaction, long-term safety and efficacy of IAIs for recurrent UTI. We conducted a cohort study using data collected between January 2013 and June 2022 at the Leiden University Medical Center. Adult patients with recurrent UTI who received prophylactic IAI were eligible for inclusion. Treatment satisfaction was assessed through a survey. Data on serum aminoglycoside concentrations, cystoscopy results and number of recurrences were obtained through chart review. Number of recurrences and UTI characteristics were compared between patients on and off IAI using Poisson and logistic mixed effects models. Forty-four patients were included (median follow-up time 976 days) and 323 UTIs occurred during follow-up. Overall treatment satisfaction was high (median 79.2/100). All but one patient had undetectable serum aminoglycoside levels and no malignancies were found on follow-up cystoscopy. IAI increased the time to first recurrence (102 days versus 36 days, P = 0.02), reduced the number of recurrences (rate ratio 0.75, 95% CI 0.56-0.99, P = 0.04) and the necessity for systemic antibiotics (OR 0.33, 95% CI 0.13-0.86, P = 0.02). In patients with recurrent UTI, IAI was associated with high treatment satisfaction, and was found to be a safe and effective alternative to oral antimicrobial prophylaxis.

Virulence gene detection and antimicrobial resistance analysis of Enterococcus faecium in captive giant pandas (Ailuropoda melanoleuca) in China

BackgroundThe emergence of multidrug resistance among enterococci makes effective treatment of enterococcal infections more challenging. Giant pandas (Ailuropoda melanoleuca) are vulnerable to oral trauma and lesions as they feast on bamboo. Enterococci may contaminate such oral lesions and cause infection necessitating treatment with antibiotics. However, few studies have focused on the virulence and drug resistance of oral-derived enterococci, including Enterococcus faecium, in giant pandas. In this study, we analyzed the prevalence of 8 virulence genes and 14 drug resistance genes in E. faecium isolates isolated from saliva samples of giant pandas held in captivity in China and examined the antimicrobial drug susceptibility patterns of the E. faecium isolates.ResultsTwenty-eight isolates of E. faecium were successfully isolated from the saliva samples. Four virulence genes were detected, with the acm gene showing the highest prevalence (89%). The cylA, cpd, esp, and hyl genes were not detected. The isolated E. faecium isolates possessed strong resistance to a variety of drugs; however, they were sensitive to high concentrations of aminoglycosides. The resistance rates to vancomycin, linezolid, and nitrofurantoin were higher than those previously revealed by similar studies in China and other countries.ConclusionsThe findings of the present study indicate the drugs of choice for treatment of oral E. faecium infection in the giant panda.

Silver nanoparticles enhance the efficacy of aminoglycosides against antibiotic-resistant bacteria.

As the threat of antimicrobial-resistant bacteria compromises the safety and efficacy of modern healthcare practices, the search for effective treatments is more urgent than ever. For centuries, silver (Ag) has been known to have antibacterial properties and, over the past two decades, Ag-based nanoparticles have gained traction as potential antimicrobials. The antibacterial efficacy of Ag varies with structure, size, and concentration. In the present study, we examined Ag nanoparticles (AgNPs) for their antimicrobial activity and safety. We compared different commercially-available AgNPs against gram-negative Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and gram-positive Staphylococcus aureus methicillin-resistant and susceptible strains. The most effective formula of AgNPs tested had single-digit (μg/mL) minimum inhibitory concentrations against gram-negative multidrug-resistant clinical bacterial isolates with novel and emerging mechanisms of resistance. The mode of killing was assessed in E. coli and was found to be bactericidal, which is consistent with previous studies using other AgNP formulations. We evaluated cytotoxicity by measuring physiological readouts using the Caenorhabditis elegans model and found that motility was affected, but not the lifespan. Furthermore, we found that at their antibacterial concentrations, AgNPs were non-cytotoxic to any of the mammalian cell lines tested, including macrophages, stem cells, and epithelial cells. More interestingly, our experiments revealed synergy with clinically relevant antibiotics. We found that a non-toxic and non-effective concentration of AgNPs reduced the minimum inhibitory concentrations of aminoglycoside by approximately 22-fold. Because both aminoglycosides and Ag are known to target the bacterial ribosome, we tested whether Ag could also target eukaryotic ribosomes. We measured the rate of mistranslation at bactericidal concentration and found no effect, indicating that AgNPs are not proteotoxic to the host at the tested concentrations. Collectively, our results suggest that AgNPs could have a promising clinical application as a potential stand-alone therapy or antibiotic adjuvants.

Genomic and transcriptomic profiling of phoenix colonies

Pseudomonas aeruginosa is a Gram-negative bacterium responsible for numerous human infections. Previously, novel antibiotic tolerant variants known as phoenix colonies as well as variants similar to viable but non-culturable (VBNC) colonies were identified in response to high concentrations of aminoglycosides. In this study, the mechanisms behind phoenix colony and VBNC-like colony emergence were further explored using both whole genome sequencing and RNA sequencing. Phoenix colonies were found to have a single nucleotide polymorphism (SNP) in the PA4673 gene, which is predicted to encode a GTP-binding protein. No SNPs were identified within VBNC-like colonies compared to the founder population. RNA sequencing did not detect change in expression of PA4673 but revealed multiple differentially expressed genes that may play a role in phoenix colony emergence. One of these differentially expressed genes, PA3626, encodes for a tRNA pseudouridine synthase which when knocked out led to a complete lack of phoenix colonies. Although not immediately clear whether the identified genes in this study may have interactions which have not yet been recognized, they may contribute to the understanding of how phoenix colonies are able to emerge and survive in the presence of antibiotic exposure.

Arctic Psychrotolerant Pseudomonas sp. B14-6 Exhibits Temperature-Dependent Susceptibility to Aminoglycosides.

Bacteria can evade antibiotics by acquiring resistance genes, as well as switching to a non-growing dormant state without accompanying genetic modification. Bacteria in this quiescent state are called persisters, and this non-inheritable ability to withstand multiple antibiotics is referred to as antibiotic tolerance. Although all bacteria are considered to be able to form antibiotic-tolerant persisters, the antibiotic tolerance of extremophilic bacteria is poorly understood. Previously, we identified the psychrotolerant bacterium Pseudomonas sp. B14-6 from the glacier foreland of Midtre Lovénbreen in High Arctic Svalbard. Herein, we investigated the resistance and tolerance of Pseudomonas sp. B14-6 against aminoglycosides at various temperatures. This bacterium was resistant to streptomycin and susceptible to apramycin, gentamicin, kanamycin, and tobramycin. The two putative aminoglycoside phosphotransferase genes aph1 and aph2 were the most likely contributors to streptomycin resistance. Notably, unlike the mesophilic Pseudomonas aeruginosa PA14, this cold-adapted bacterium demonstrated reduced susceptibility to all tested aminoglycosides in a temperature-dependent manner. Pseudomonas sp. B14-6 at a lower temperature formed the persister cells that shows tolerance to the 100-fold minimum inhibitory concentration (MIC) of gentamicin, as well as the partially tolerant cells that withstand 25-fold MIC gentamicin. The temperature-dependent gentamicin tolerance appears to result from reduced metabolic activity. Lastly, the partially tolerant Pseudomonas sp. B14-6 cells could slowly proliferate under the bactericidal concentrations of aminoglycosides. Our results demonstrate that Pseudomonas sp. B14-6 has a characteristic ability to form cells with a range of tolerance, which appears to be inversely proportional to its growth rate.

Role of Efflux in Antibiotic Resistance of Achromobacter xylosoxidans and Achromobacter insuavis Isolates From Patients With Cystic Fibrosis.

Achromobacter genus (including Achromobacter xylosoxidans, the most prevalent Achromobacter species in patients with cystic fibrosis) is poorly susceptible to most conventional antibiotics. Contribution of efflux by AxyABM, AxyXY-OprZ, and AxyEF-OprN and of target mutations were studied in clinical isolates of A. xylosoxidans and Achromobacter insuavis. Forty-one isolates longitudinally collected from 21 patients with CF were studied by whole-genome sequencing (WGS)-typing, determination of minimum inhibitory concentrations (MICs) of β-lactams, aminoglycosides, colistin, azithromycin, ciprofloxacin, chloramphenicol, and doxycycline, and expression (quantitative RT-PCR) and function (measure of the uptake of a fluorescent substrate) of efflux pumps. WGS-based typing resulted in 10 clusters comprising 2 or 3 isolates and 20 singletons. The efflux activity was high in strains with elevated MICs for amikacin or azithromycin. This work sheds a new light on the impact of efflux and target mutations in resistance of Achromobacter to several drugs.

Aminoglycoside treatment alters hearing-related genes and depicts behavioral defects in Drosophila.

The hearing organ of Drosophila is present within the second segment of antennae. The hearing organ of Drosophila (Johnston's organ [JO]) shares much structural, developmental, and functional similarity with the vertebrate hearing organ (Organ of Corti). JO is evolving as a potential model system to examine the hearing-associated defects in vertebrates. In the vertebrates, aminoglycosides like gentamicin, kanamycin, and neomycin have been known to cause defects in the hearing organ. However, a complete mechanism of toxicity is not known. Taking the evolutionary conservation into account the current study aims to test various concentrations of aminoglycoside on the model organism, Drosophila melanogaster. The current study uses the oral route to check the toxicity of various aminoglycosides at different concentrations (50, 100, 150, 200, and 250 μg ml- 1 ). In Drosophila, many foreign particles enter the body through the gut via food. The aminoglycoside treated third instar larvae show defective crawling and sound avoidance behavior. The adult flies release lower amounts of acetylcholine esterase and higher amounts of reactive oxygen species than control untreated animals, accompanied by defective climbing and aggressive behavior. All these behavioral defects are further confirmed by the altered expression level of hearing genes such as nompC, inactive, nanchung, pyrexia. All the behavioral and genetic defects are reported as a readout of aminoglycoside toxicity.

N-Butanol Potentiates Subinhibitory Aminoglycosides against Bacterial Persisters and Multidrug-Resistant MRSA by Rapidly Enhancing Antibiotic Uptake.

Potentiation of traditional antibiotics is of significance for combating antibiotic-resistant bacteria that have become a severe threat to human and animal health. Here, we report that 1 min co-treatment with n-butanol greatly and specifically enhances the bactericidal action of aminoglycosides by 5 orders of magnitude against stationary-phase Staphylococcus aureus cells, with n-propanol and isobutanol showing less potency. This combined treatment also rapidly kills various S. aureus persisters, methicillin-resistant S. aureus (MRSA) cells, and numerous Gram-positive and -negative pathogens including some clinically isolated multidrug-resistant pathogens (e.g., S. aureus, Staphylococcus epidermidis, and Enterococcus faecalis) in vitro, as well as S. aureus in mice. Mechanistically, the potentiation results from the actions of aminoglycosides on their conventional target ribosome rather than the antiseptic effect of n-butanol and is achieved by rapidly enhancing the bacterial uptake of aminoglycosides, while salts and inhibitors of proton motive force (e.g., CCCP) can diminish this uptake. Importantly, such n-butanol-enhanced antibiotic uptake even enables subinhibitory concentrations of aminoglycosides to rapidly kill both MRSA and conventional S. aureus cells. Given n-butanol is a non-metabolite in the pathogens we tested, our work may open avenues to develop a metabolite-independent strategy for aminoglycoside potentiation to rapidly eliminate antibiotic-resistant/tolerant pathogens, as well as for reducing the toxicity associated with aminoglycoside use.

Role of Aminoglycoside-Modifying Enzymes (AMEs) in Resistance to Aminoglycosides among Clinical Isolates of Pseudomonas aeruginosa in the North of Iran.

In recent years, the prevalence of resistance to aminoglycosides among clinical isolates of Pseudomonas aeruginosa is increasing. The aim of this study was to investigate the role of aminoglycoside-modifying enzymes (AMEs) in resistance to aminoglycosides in clinical isolates of P. aeruginosa. The clinical isolates were collected from different hospitals. Disk agar diffusion test was used to determine the antimicrobial resistance pattern of the clinical isolates, and the minimum inhibitory concentration of aminoglycosides was detected by microbroth dilution method. The PCR was performed for discovery of aminoglycoside-modifying enzyme-encoding genes. Among 100 screened isolates, 43 (43%) isolates were resistant to at least one tested aminoglycosides. However, 13 (13%) isolates were resistant to all tested aminoglycosides and 37 isolates were detected as multidrug resistant (MDR). The resistance rates of P. aeruginosa isolates against tested antibiotics were as follows: ciprofloxacin (41%), piperacillin-tazobactam (12%), cefepime (32%), piperacillin (26%), and imipenem (31%). However, according to the MIC method, 13%, 32%, 33%, and 37% of the isolates were resistant to amikacin, gentamicin, tobramycin, and netilmicin, respectively. The PCR results showed that AAC(6′)-Ib was the most commonly (26/43, 60.4%) identified AME-encoding gene followed by AAC(6′)-IIa (41.86%), APH(3′)-IIb (34.8%), ANT(3″)-Ia (18.6), ANT(2″)-Ia (13.95%), and APH(3″)-Ib (2.32%). However, APH(3′)-Ib was not found in any of the studied isolates. The high prevalence of AME-encoding genes among aminoglycoside-resistant P. aeruginosa isolates in this area indicated the important role of AMEs in resistance to these antibiotics similar to most studies worldwide. Due to the transmission possibility of these genes between the Gram-negative bacteria, we need to control the prescription of aminoglycosides in hospitals.

Aminoglycoside dosing and monitoring for Pseudomonas aeruginosa during acute pulmonary exacerbations in cystic fibrosis.

Aminoglycosides are commonly used for the treatment of Pseudomonas aeruginosa (PsA) in the setting of acute pulmonary exacerbations (PEx) in pediatric patients with cystic fibrosis (CF). There are controversies and practice differences between institutions related to aminoglycoside dosing and monitoring strategies. The purpose of this review article is to summarize the currently available literature and identify gaps in the literature related to pharmacokinetic parameter goals, aminoglycoside dosing strategies, and methods for monitoring serum aminoglycoside concentrations for treatment of PsA in CF PEx, and throughout will discuss anticipated changes with the increasing availability of highly effective CF transmembrane conductance regulator modulators. This review focuses on tobramycin, as it is the most commonly used aminoglycoside in CF PEx, and will briefly discuss special circumstances surrounding use of amikacin and gentamicin.

La concentration sérique de gentamicine est-elle modifiée par une autotransfusion sanguine par cell-saver après une arthroplastie totale du genou avec de l’acide tranexamique ? Un essai contrôlé randomisé

BackgroundSelf-transfusion has been proven as an effective management of blood loss after total knee arthroplasty (TKA). Considering that the high local concentration of antibiotic from bone cement is delivered intravenously through the self-transfusion process, systematic toxicity has never been evaluated. In addition, the effectiveness of self-transfusion with the routine concomitant use of other modern blood-salvage strategies, like tranexamic acid, should also be assessed. Therefore we performed a randomized study to assess: (1) the safety of self-transfusion in TKA by comparing the gentamicin concentrations resulting from the use or not of autologous blood transfusion; (2) the efficacy of self-transfusion in TKA, with the concomitant administration of tranexamic acid. HypothesisSelf-transfusion in TKA elevates the serum gentamicin concentration and the potential risk of nephrotoxicity. MethodsThe serum concentration of aminoglycosides was measured in two groups of 20 patients each, after TKA, according to the use of self-transfusion. Hemoglobin, renal function and calculated blood loss were compared at several points in time between groups. ResultsThe only time where there was a statistically significant difference in serum gentamicin, was at 48h postoperatively between groups [0.3 ug/ml±0.21, range: 0.15 to 0.72 vs. 0.14ug/ml±0.1, range: 0 to 0.35 (p=0.02)]. There were no significant differences in total blood loss [1341ml±501, range: 830 to 2230 vs. 1263ml±459 range: 840 to 2480 (p=0.67)] and need of allogeneic blood transfusion [3 units vs. 2 units] between groups. ConclusionThe use of autologous blood transfusion was found to be safe, in terms of nephrotoxicity of aminoglycosides after TKA, but it seemed to be ineffective as a blood salvage strategy, when used concomitantly with the administration of tranexamic acid. Level of EvidenceII; low powered randomized study. ClinicalTrials.gov registration numberNCT04505748.

Acute Kidney Injury When Treating Periprosthetic Joint Infections After Total Knee Arthroplasties with Antibiotic-Loaded Spacers: Incidence, Risks, and Outcomes.

Two-stage exchange arthroplasty with a high-dose antibiotic-loaded bone cement (ALBC) spacer and intravenous or oral antibiotics is the most common method of managing a periprosthetic joint infection (PJI) after a total knee arthroplasty (TKA). However, little is known about the contemporary incidence, the risk factors, and the outcomes of acute kidney injuries (AKIs) in this cohort. We identified 424 patients who had been treated with 455 ALBC spacers after resection of a PJI following a primary TKA from 2000 to 2017. The mean age at resection was 67 years, the mean body mass index (BMI) was 33 kg/m2, 47% of the patients were women, and 15% had preexisting chronic kidney disease (CKD). The spacers (87% nonarticulating) contained a mean of 8 g of vancomycin and 9 g of an aminoglycoside per construct (in situ for a mean of 11 weeks). Eighty-six spacers also had amphotericin B (mean, 412 mg). All of the patients were concomitantly treated with systemic antibiotics for a mean of 6 weeks. An AKI was defined as a creatinine level of ≥1.5 times the baseline or an increase of ≥0.3 mg/dL within any 48-hour period. The mean follow-up was 6 years (range, 2 to 17 years). Fifty-four AKIs occurred in 52 (14%) of the 359 patients without preexisting CKD versus 32 AKIs in 29 (45%) of the 65 patients with CKD (odds ratio [OR], 5; p = 0.0001); none required acute dialysis. Overall, when the vancomycin concentration or aminoglycoside concentration was >3.6 g/batch of cement, the risk of AKI increased (OR, 1.9 and 1.8, respectively; p = 0.02 for both). Hypertension (β = 0.17; p = 0.002), perioperative hypovolemia (β = 0.28; p = 0.0001), and acute atrial fibrillation (β = 0.13; p = 0.009) were independent predictors for AKI in patients without preexisting CKD. At the last follow-up, 8 patients who had sustained an AKI had progressed to CKD, 4 of whom received dialysis. In our study, the largest series to date that we are aware of regarding this issue, AKI occurred in 14% of patients with normal renal function at baseline, and 2% developed CKD after undergoing a 2-stage exchange arthroplasty for a PJI after TKA. However, the risk of AKI was fivefold greater in those with preexisting CKD. The causes of acute renal blood flow impairment were independent predictors for AKI. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Effect of small molecule eRF3 degraders on premature termination codon readthrough.

Premature termination codon (PTC) readthrough is considered a potential treatment for genetic diseases caused by nonsense mutations. High concentrations of aminoglycosides induce low levels of PTC readthrough but also elicit severe toxicity. Identifying compounds that enhance PTC readthrough by aminoglycosides or reduce their toxicity is a continuing challenge. In humans, a binary complex of eukaryotic release factors 1 (eRF1) and 3 (eRF3a or eRF3b) mediates translation termination. They also participate in the SURF (SMG1-UPF1-eRF1-eRF3) complex assembly involved in nonsense-mediated mRNA decay (NMD). We show that PTC readthrough by aminoglycoside G418 is considerably enhanced by eRF3a and eRF3b siRNAs and cereblon E3 ligase modulators CC-885 and CC-90009, which induce proteasomal degradation of eRF3a and eRF3b. eRF3 degradation also reduces eRF1 levels and upregulates UPF1 and selectively stabilizes TP53 transcripts bearing a nonsense mutation over WT, indicating NMD suppression. CC-90009 is considerably less toxic than CC-885 and it enhances PTC readthrough in combination with aminoglycosides in mucopolysaccharidosis type I-Hurler, late infantile neuronal ceroid lipofuscinosis, Duchenne muscular dystrophy and junctional epidermolysis bullosa patient-derived cells with nonsense mutations in the IDUA, TPP1, DMD and COL17A1 genes, respectively. Combination of CC-90009 with aminoglycosides such as gentamicin or ELX-02 may have potential for PTC readthrough therapy.

Translation error clusters induced by aminoglycoside antibiotics

Aminoglycoside antibiotics target the ribosome and induce mistranslation, yet which translation errors induce bacterial cell death is unclear. The analysis of cellular proteins by quantitative mass spectrometry shows that bactericidal aminoglycosides induce not only single translation errors, but also clusters of errors in full-length proteins in vivo with as many as four amino acid substitutions in a row. The downstream errors in a cluster are up to 10,000-fold more frequent than the first error and independent of the intracellular aminoglycoside concentration. The prevalence, length, and composition of error clusters depends not only on the misreading propensity of a given aminoglycoside, but also on its ability to inhibit ribosome translocation along the mRNA. Error clusters constitute a distinct class of misreading events in vivo that may provide the predominant source of proteotoxic stress at low aminoglycoside concentration, which is particularly important for the autocatalytic uptake of the drugs.

Role of aminoglycoside-modifying enzymes and 16S rRNA methylase (ArmA) in resistance of Acinetobacter baumannii clinical isolates against aminoglycosides.

INTRODUCTION: This study aimed to determine the role of genes encoding aminoglycoside-modifying enzymes (AMEs) and 16S rRNA methylase (ArmA) in Acinetobacter baumannii clinical isolates. METHODS: We collected 100 clinical isolates of A. baumannii and identified and confirmed them using microbiological tests and assessment of the OXA-51 gene. Antibiotic susceptibility testing was carried out using disk agar diffusion and micro-broth dilution methods. The presence of AME genes and ArmA was detected by PCR and multiplex PCR. RESULTS: The most and least effective antibiotics in this study were netilmicin and ciprofloxacin with 68% and 100% resistance rates, respectively. According to the minimum inhibitory concentration test, 94% of the isolates were resistant to gentamicin, tobramycin, and streptomycin, while the highest susceptibility (20%) was observed against netilmicin. The proportion of strains harboring the aminoglycoside resistance genes was as follows: APH(3′)-VIa (aphA6) (77%), ANT(2”)-Ia (aadB) (73%), ANT(3”)-Ia (aadA1) (33%), AAC(6′)-Ib (aacA4) (33%), ArmA (22%), and AAC(3)-IIa (aacC2) (19%). Among the 22 gene profiles detected in this study, the most prevalent profiles included APH(3′)-VIa + ANT(2”)-Ia (39 isolates, 100% of which were kanamycin-resistant), and AAC(3)-IIa + AAC(6′)-Ib + ANT(3”)-Ia + APH(3′)-VIa + ANT(2”)-Ia (14 isolates, all of which were resistant to gentamicin, kanamycin, and streptomycin). CONCLUSIONS: High minimum inhibitory concentration of aminoglycosides in isolates with the simultaneous presence of AME- and ArmA-encoding genes indicated the importance of these genes in resistance to aminoglycosides. However, control of their spread could be effective in the treatment of infections caused by A. baumannii.