Tobramycin Concentrations Research Articles

Bone allograft impregnated with tobramycin and vancomycin delivers antibiotics in high concentrations for prophylaxis against bacteria commonly associated with prosthetic joint infections.

Local delivery of antibiotics as prophylaxis for prosthetic joint infections (PJIs) is frequently used during total hip replacement surgery. Morselized bone allograft impregnated with vancomycin and tobramycin (TobraVanc) could provide effective prophylaxis against bacteria commonly associated with PJIs. In this study, the concentrations of antibiotics released by bone allograft impregnated with TobraVanc were determined by using an in vitro bioassay system entailing measuring inhibition zone diameters caused by antibiotic-impregnated bone chips cast in agar against standard curves. The concentrations were determined in samples of TobraVanc-impregnated bone graft taken before and after the application of the bone graft in the patients undergoing acetabular revision surgery. Antibiotic-impregnated bone grafts, sampled prior to application in the patient, delivered antibiotics in the concentration ranges of 730-9,800 mg/L for tobramycin and 1,300-11,000 mg/L for vancomycin. Samples taken after application in the patient released lower concentrations of tobramycin (490-1,900 mg/L; P < 0.01) and vancomycin (3,000-5,100 mg/L; P < 0.05); however, these concentrations remained well above the tobramycin minimum inhibitory concentrations (MICs) for investigated, highly tobramycin-resistant Staphylococcus epidermidis strains (MICs > 256 mg/L). At the tested concentrations, bone graft material mixed with TobraVanc delivered antibiotics in potent concentrations above the MICs for bacteria causing PJIs. Clinical trials are needed to evaluate the efficacy and risk of TobraVanc-impregnated bone graft as a prophylactic agent for patients undergoing hip replacement surgery.IMPORTANCEAntibiotic prophylaxis is the cornerstone of successful joint replacement surgery, reducing the risk for the dreaded complication of prosthetic joint infection (PJI) to roughly 0.5%-2% in standard total hip replacement (THR). In addition to systemic antibiotics, antibiotics added locally have the potential to reduce the PJI risk even further, because of the high concentrations that can be achieved in the joint with limited risk for systemic toxicity. The results in the current study show that bone chips impregnated with a combination of tobramycin and vancomycin (TobraVanc) release antibiotics in concentrations that are potent against common bacteria causing PJIs. Especially in high-risk patients, our results support the prophylactic use of TobraVanc in hip replacement surgery requiring the use of a bone graft. A clinical study testing the efficacy of TobraVanc-impregnated bone graft in reducing the incidence of PJI in hip replacement surgery is currently ongoing (EudraCT: 2021-001708-14).

Enhanced sensitivity in tobramycin monitoring using a surfactant-aligned liquid crystal aptasensor with a ternary hybrid aptamer

Determining pharmaceutical residues in foodstuffs is of great importance worldwide. The improper use of tobramycin (TOB) with abroad spectrum antibacterial activity results in its accumulation in the food chain and human body. Given its detrimental effects on human health, the careful surveillance of TOB concentrations is essential to ensure food safety. Presented here is a highly sensitive aptasensing array designed to measure the TOB concentration by disrupting the alignment of liquid crystal (LC) molecules induced by surfactants. For the first time, a ternary hybrid of the aptamer strands was incorporated onto the surfactant-designed LC-aqueous interface instead of a single strand of aptamer, causing a significant disruption in the customary orientation of LCs. This changed the brightness quantity from 35.06 to 69.54, due to higher interaction with the positively charged section of the surfactant than that for one aptamer strand. The presence of TOB caused the ternary aptamer hybrid to break apart by creating the complex between the aptamer and TOB, separating the aptamer strands from the LC-aqueous interface. Subsequently, the TOB presence was specified by inducing a color change in the polarized vision of the aptasensor platform, resulting in a shift from colorful to murky. The aptasensor could monitor TOB in the linear concentration range of 1 fM-10 nM, with an impressively low detection limit of 0.217 fM. With the capability to determine TOB in beef, chicken egg, and low-fat milk, the LC-decorated aptasensor is proficient in food quality control. The aptasensor possesses characteristics such as simplicity, high sensitivity, ease of use, and affordability. As a result, it has the potential to be marketed as a portable testing kit that is convenient and cost-effective.

Analysis of Antibiotic Response in Clinical Wound Pseudomonas aeruginosa Isolates: Unveiling Proteome Dynamics of Tobramycin-Tolerant Phenotype

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic human pathogen, causing serious chronic infections. P. aeruginosa can adapt efficiently to antibiotic stressors via different genotypic or phenotypic strategies such as resistance and tolerance. The adaptation regulatory system is not always very well understood. In this study, we use shotgun proteomics to investigate the system-level response to tobramycin in two clinical wound P. aeruginosa isolates and PAO1. We profiled each strain for its antibiotic drug-tolerant phenotype using supra-minimum inhibitory concentrations (supra-MIC) of tobramycin and applied proteomics to investigate the protein expression profiles. The MIC revealed that all isolates were susceptible to tobramycin but at supra-MIC concentrations at stationary growth, a degree of tolerance was observed for the isolates. We identified around 40 % of the total proteins encoded by the P. aeruginosa genome and highlighted shared and unique protein signatures for all isolates. Comparative proteome profiling in the absence of antibiotic treatment showed divergent fingerprints, despite similarities in the growth behavior of the isolates. In the presence of tobramycin, the isolates shared a common response in the downregulation of proteins involved in the two-component system, whereas stress response proteins were present at higher levels. Our findings provide insight into the use of proteomic tools to dissect the system-level response in clinical isolates in the absence and presence of antibiotic stress.

In Vivo Intra-Articular Antibiotic Concentrations at 24 Hours After TKA Fall Below the Minimum Inhibitory Concentration for Most Bacteria: A Randomized Study of Commercially Available Bone Cement.

The use of antibiotic-loaded bone cement (ALBC) to help reduce the risk of infection after primary total knee arthroplasty (TKA) is controversial. There is a paucity of in vivo data on the elution characteristics of ALBC. We aimed to determine whether the antibiotic concentrations of 2 commercially available ALBCs met the minimum inhibitory concentration (MIC) and minimum biofilm eradication concentration (MBEC) for common infecting organisms. Forty-five patients undergoing TKA were randomized to receive 1 of the following: bone cement without antibiotic (the negative control; n = 5), a commercially available formulation containing 1 g of tobramycin (n = 20), or a commercially available formulation containing 0.5 g of gentamicin (n = 20). Intra-articular drains were placed, and fluid was collected at 4 and 24 hours postoperatively. An automated immunoassay measuring antibiotic concentration was performed, and the results were compared against published MIC and MBEC thresholds. The ALBC treatment groups were predominantly of White (65%) or Black (32.5%) race and were 57.5% female and 42.4% male. The mean age (and standard deviation) was 72.6 ± 7.2 years in the gentamicin group and 67.6 ± 7.4 years in the tobramycin group. The mean antibiotic concentration in the tobramycin group was 55.1 ± 37.7 μg/mL at 4 hours and 19.5 ± 13.0 μg/mL at 24 hours, and the mean concentration in the gentamicin group was 38.4 ± 25.4 μg/mL at 4 hours and 17.7 ± 15.4 μg/mL at 24 hours. Time and antibiotic concentration had a negative linear correlation coefficient (r = -0.501). Most of the reference MIC levels were reached at 4 hours. However, at 24 hours, a considerable percentage of patients had concentrations below the MIC for many common pathogens, including Staphylococcus epidermidis (gentamicin: 65% to 100% of patients; tobramycin: 50% to 85%), methicillin-sensitive Staphylococcus aureus (gentamicin: 5% to 90%; tobramycin: 5% to 50%), methicillin-resistant S . aureus (gentamicin: 5% to 65%; tobramycin: 50%), Streptococcus species (gentamicin: 10% to 100%), and Cutibacterium acnes (gentamicin: 10% to 65%; tobramycin: 100%). The aforementioned ranges reflect variation in the MIC among different strains of each organism. Gentamicin concentrations reached MBEC threshold values at 4 hours only for the least virulent strains of S . aureus and Escherichia coli. Tobramycin concentrations did not reach the MBEC threshold for any of the bacteria at either time point. The elution of antibiotics from commercially available ALBC decreased rapidly following TKA, and only at 4 hours postoperatively did the mean antibiotic concentrations exceed the MIC for most of the pathogens. Use of commercially available ALBC may not provide substantial antimicrobial coverage following TKA. Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

Impact of pH modification of the empirically used tobramycin ophthalmic solution on MIC90 concentration in tears and aqueous humor of donkeys (Equus asinus)

BackgroundCommercial tobramycin ophthalmic solution is frequently used empirically to treat ocular disorders in equines, despite being primarily formulated for use in humans. It has been noted that tobramycin MIC90 concentration (minimal inhibitory concentration to 90% of microbial growth) rapidly declined following topical administration. It is hypothesized that adjustment of the pH of the empirically used tobramycin ophthalmic solution -prepared for human use- with the pH of the tears of donkeys, could increase the bioavailability of the drug and subsequently improve its penetration to the aqueous humor. Therefore, this study aimed to evaluate the impact of pH adjustment of the empirically used tobramycin ophthalmic solution on MIC90 concentration in tears and aqueous humor of donkeys (Equus asinus). The study was conducted on six (n = 6) clinically healthy donkeys. In each donkey, one eye was randomly selected to receive 210 µg tobramycin of the commercial tobramycin (CT) and used as a positive control (C group, n = 6). The other eye (treated eye) received 210 µg of the modified tobramycin ophthalmic solution (MT) (T group, n = 6). Tears and aqueous humor samples were collected 5-, 10-, 15-, 30- min, and 1-, 2-, 4-, and 6 h post-instillation.ResultsModifying the pH of the empirically used commercial tobramycin ophthalmic solution in donkeys at a pH of 8.26 enhanced the drug’s bioavailability. The MIC90 of the most hazardous bacteria isolated from equines’ eyes such as Pseudomonas aeruginosa (MIC90 = 128 µg/ml) and Staphylococcus aureus (MIC90 = 256 µg/ml) was covered early (5 min post-instillation) and over a longer period in donkey tears (239–342 min) and aqueous humor (238–330 min) with the modified tobramycin solution.ConclusionsAdjustment of the pH of the commercial tobramycin ophthalmic solution, empirically used by veterinarians to treat donkeys’ ophthalmic infections at a pH of 8.26, isotonic with the donkeys’ tears pH, resulting in higher concentrations of tobramycin in tears and aqueous humor for a longer time.

Evaluation of Target Attainment for Tobramycin in Children and Adults with Cystic Fibrosis.

Introduction: Patients with cystic fibrosis (CF) commonly experience pulmonary exacerbations, and it is recommended by the TOPIC study to treat this with tobramycin at a dose of 10 mg/kg once daily. The aim of this study was to evaluate the target attainment of the current dosing regimen. Methods: A single-center retrospective cohort study of child and adult patients with CF who received tobramycin between 2019 and 2022 was conducted. Descriptive statistics and linear mixed models were used to assess target attainment for tobramycin. Results: In total, 25 patients (53 courses), of which 10 were children (12 courses) and 15 were adults (41 courses), were included. Those 25 patients all received 10 mg/kg/day. The tobramycin peak concentrations were supratherapeutic in 82.9% and therapeutic in 100.0% of adults and children, respectively. The trough concentrations were outside the target range in 0% and 5.1% of children and adults, respectively. We found lower tobramycin concentrations with the same dose in children compared to adults. Conclusions: This study illustrates the need to validate dosing advice in a real-world setting, as supratherapeutic concentrations of tobramycin were prevalent in adults with CF.

Cuminaldehyde and Tobramycin Forestall the Biofilm Threats of Staphylococcus aureus: A Combinatorial Strategy to Evade the Biofilm Challenges.

Staphylococcus aureus, an opportunistic Gram-positive pathogen, is known for causing various infections in humans, primarily by forming biofilms. The biofilm-induced antibiotic resistance has been considered a significant medical threat. Combinatorial therapy has been considered a reliable approach to combat antibiotic resistance by using multiple antimicrobial agents simultaneously, targeting bacteria through different mechanisms of action. To this end, we examined the effects of two molecules, cuminaldehyde (a natural compound) and tobramycin (an antibiotic), individually and in combination, against staphylococcal biofilm. Our experimental observations demonstrated that cuminaldehyde (20μg/mL) in combination with tobramycin (0.05μg/mL) exhibited efficient reduction in biofilm formation compared to their individual treatments (p < 0.01). Additionally, the combination showed an additive interaction (fractional inhibitory concentration value 0.66) against S. aureus. Further analysis revealed that the effective combination accelerated the buildup of reactive oxygen species (ROS) and increased the membrane permeability of the bacteria. Our findings also specified that the cuminaldehyde in combination with tobramycin efficiently reduced biofilm-associated pathogenicity factors of S. aureus, including fibrinogen clumping ability, hemolysis property, and staphyloxanthin production. The selected concentrations of tobramycin and cuminaldehyde demonstrated promising activity against the biofilm development of S. aureus on catheter models without exerting antimicrobial effects. In conclusion, the combination of tobramycin and cuminaldehyde presented a successful strategy for combating staphylococcal biofilm-related healthcare threats. This combinatorial approach holds the potential for controlling biofilm-associated infections caused by S. aureus.

A comparison of aminoglycoside antibiotic serum concentrations collected by peripheral veins and peripherally inserted central catheters in adults with cystic fibrosis.

People with cystic fibrosis (PwCF) are frequently hospitalized for treatment of pulmonary exacerbation. The Cystic Fibrosis Foundation Pulmonary Guidelines support the use of intravenous aminoglycosides with therapeutic drug monitoring for the treatment of pulmonary exacerbation due to Pseudomonas aeruginosa. Serum intravenous tobramycin concentrations are commonly collected by peripheral venipuncture (PV). Discomfort associated with collection of samples by PV prompts collection via PICC, but the accuracy of intravenous tobramycin serum levels collected by PICC has not been documented in adult PwCF. The primary study objective was to evaluate the difference between intravenous tobramycin serum levels collected by PV and PICC in adult PwCF. The authors conducted a prospective case-control study of adult PwCF admitted to University of Utah Health for a pulmonary exacerbation receiving tobramycin by a single lumen PICC. The authors compared tobramycin peak and random serum levels collected by PV and PICC using a detailed flush and waste protocol. The authors analyzed a total of 19 patients with peripheral and PICC samples. The mean tobramycin peak collected by PV (27.2 mcg/mL) was similar to the mean peak collected by PICC (26.9 mcg/mL) (paired samples Wilcoxon signed-rank test, p = .94). The correlation coefficient was 0.88 (95% CI = 0.85-0.91, p < .001). Tobramycin serum samples collected by PICC appear to be similar in value to PV collections. Collecting aminoglycoside levels by PICC rather than PV may reduce patient discomfort and improve quality of life. Additional multicenter studies are needed to confirm these results.

Membrane fluidity homeostasis is required for tobramycin-enhanced biofilm in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen, which causes chronic infections, especially in cystic fibrosis (CF) patients where it colonizes the lungs via the build-up of biofilms. Tobramycin, an aminoglycoside, is often used to treat P. aeruginosa infections in CF patients. Tobramycin at sub-minimal inhibitory concentrations enhances both biofilm biomass and thickness in vitro; however, the mechanism(s) involved are still unknown. Herein, we show that tobramycin increases the expression and activity of SigX, an extracytoplasmic sigma factor known to be involved in the biosynthesis of membrane lipids and membrane fluidity homeostasis. The biofilm enhancement by tobramycin is not observed in a sigX mutant, and the sigX mutant displays increased membrane stiffness. Remarkably, the addition of polysorbate 80 increases membrane fluidity of sigX-mutant cells in biofilm, restoring the tobramycin-enhanced biofilm formation. Our results suggest the involvement of membrane fluidity homeostasis in biofilm development upon tobramycin exposure.IMPORTANCEPrevious studies have shown that sub-lethal concentrations of tobramycin led to an increase biofilm formation in the case of infections with the opportunistic pathogen Pseudomonas aeruginosa. We show that the mechanism involved in this phenotype relies on the cell envelope stress response, triggered by the extracytoplasmic sigma factor SigX. This phenotype was abolished in a sigX-mutant strain. Remarkably, we show that increasing the membrane fluidity of the mutant strain is sufficient to restore the effect of tobramycin. Altogether, our data suggest the involvement of membrane fluidity homeostasis in biofilm development upon tobramycin exposure.

Effects of vancomycin and tobramycin on compressive and tensile strengths of antibiotic bone cement: A biomechanical study

PurposeThis study aims to compare the compressive and tensile strengths of bone cement mixed with various concentrations of vancomycin, tobramycin, and combinations of the two. Methods12 mm × 6 mm antibiotic bone cement samples were created by vacuum mixing 0–4 g of vancomycin, tobramycin, and combinations of the two in 0.5 g increments per one pouch (40 g) of Palacos LV cement. An Instron 3369 Universal Testing System was used to determine the compressive and tensile strengths. ResultsCompressive and tensile strengths of the bone cement without antibiotics were 118 ± 4 MPa and 30.3 ± 12 MPa, respectively. 4 g of vancomycin alone decreased the compressive strength to 108 ± 4 MPa (p-value 0.001) and decreased the tensile strength beginning at 2 g which yielded a strength of 28.1 ± 12 MPa (p-value 0.016). Tobramycin alone decreased the tensile strength beginning at 1.5 g yielding a strength of 27.7 ± 7 MPa (p-value 0.003). Although it decreased compressive strength at 1 g to 117 ± 7 MPa (p-value 0.002), it demonstrated variable effects with increasing concentrations. A combination of vancomycin and tobramycin decreased both the compressive (111 ± 5 MPa, p-value 0.014) and tensile (27.9 ± 8 MPa, p-value 0.007) strengths beginning at 1 g each. ConclusionsVarious combinations of vancomycin and tobramycin affect the compressive and tensile strengths of bone cement. Clinicians should be diligent when mixing these antibiotics in bone cement to prevent possible failure of the constructs.

438 Comparison of tobramycin concentrations via peripheral and central blood draws in children with cystic fibrosis

438 Comparison of tobramycin concentrations via peripheral and central blood draws in children with cystic fibrosis

Response of Nicandra physalodes (Linn.) Gaertn. and Its Rhizospheric Organisms to the Selective Pressures of High-Concentration Oxytetracycline, Ciprofloxacin, and Tobramycin

Antibiotics play an essential role in the treatment of infectious diseases in humans and animals. Despite their benefits, the release of an increasing amount of various antibiotics into the environment poses a potential threat to plants, soils, animals, and microorganisms. Here, an outdoor pot experiment was conducted to preliminarily evaluate high concentrations of three antibiotics (oxytetracycline, ciprofloxacin, and tobramycin) on Nicandra physalodes (Linn.) Gaertn. and its rhizospheric organisms. The results showed that the three antibiotics had different effects on the growth behavior (germination uniformity, average growing height gain per week, and thousand seed weight) and biomass (aboveground biomass and belowground biomass) of Nicandra physalodes (Linn.) Gaertn. After adding high concentrations of the three antibiotics to the soil of each test group, the earthworm extract in group A (oxytetracycline) significantly increased the coagulation parameters prothrombin time (PT) and thrombin time (TT). The PT significantly decreased (p &lt; 0.01), while the TT was not affected in group B (ciprofloxacin). For group C (tobramycin), the TT significantly decreased (p &lt; 0.01) and the PT was not affected compared to the CK group (control group). The application of the three antibiotics caused alterations in the general activity of enzymes, such as soil sucrase (SC), urease (UE), acid phosphatase (ACP), alkaline phosphatase (AKP), and nitrate reductase (NR). Different antibiotic groups influenced the rhizosphere bacterial diversity and community structure of Nicandra physalodes (Linn.) Gaertn. At the phylum level, Ignavibacteriae was only found in group C, and Parcubacteria and Ignavibacteriae were not present in the CK group. At the genus level, Parcubacteria_norank was not present in the CK group, and BSV40_norank was found in group C. Ultimately, the results suggested that high concentrations of oxytetracycline, ciprofloxacin, and tobramycin could affect the growth behavior and biomass of Nicandra physalodes (Linn.) Gaertn. and alter its rhizobacterial community structure, providing the scientific basis for the rational use of antibiotics in animal husbandry and veterinary science.

Construction of aptamer sensor based on Au nanozymes for ultrasensitive SERS detection of tobramycin

Tobramycin aptamer was adsorbed on the surface of gold nanoparticles (Au NPs) by van der Waals forces, hydrogen bonds, and other factors, limiting nanozyme peroxidase activity. Because tobramycin has a higher affinity for the tobramycin aptamer, including tobramycin in Au@Apts nanozymes was able to dislodge the aptamer from the surface of Au NPs and restore the catalytic activity of nanozymes. Raman spectroscopy of the enzyme-catalyzed product TMBox can detect this shift in enzyme activity. The restored value of nanozyme activity increased with tobramycin concentration and had a good linear correlation in the concentration range of 10−10∼10−1 M with a detection limit of 2.04 × 10−11 M. Aptamer biosensors are built using the SERS platform, which has the advantages of high sensitivity, high precision, and a wide detection range. It is prospectively employed in food safety and the detection of antibiotic residues.

Synthesis of fluorescent probe based on molecularly imprinted polymers on nitrogen-doped carbon dots for determination of tobramycin in milk.

Tobramycin (TOB) plays a considerable role in combating milk spoilage and preventing disease in dairy cows. However, overuse of TOB can lead to nephrotoxicity, ototoxicity, neuromuscular blockade, and hypersensitivity reactions. Here, nitrogen-doped carbon dots (N-CDs) were prepared with ethylenediamine and citric acid, then molecularly imprinted layers were obtained by imprinting of surface on the N-CDs to prepare Nitrogen-doped carbon dot-based molecularly imprinted polymers (N-CDs@MIPs). The fluorescence emission spectrum of this probe showed a linear enhancement with the TOB concentration in the 1-12μM. Meanwhile, a detection limit of 99.2nM was obtained. This probe was not affected by the structural analogs of the TOB and can show high sensitivity and selectivity compared to non-imprinted polymers (N-CDs@NIPs). Therefore, it can be successfully used for the trace analysis of TOB in milk with advantages over other reported techniques such as liquid chromatography coupled with tandem mass spectrometry or various aptamer sensors.

Dual fluorescence-colorimetric sensor based on silver nanoparticles for determination of tobramycin in its pharmaceutical preparations

The purpose of this study is to develop a dual fluorescence-colorimetric sensor for determination of the non-chromophoric drug, tobramycin using fluorescein-modified silver nanoparticles. Fluorescein is adsorbed on the surface of silver nanoparticles resulting in quenching of the fluorescence intensity of fluorescein at 513 nm. Upon addition of tobramycin to fluorescein-bound silver nanoparticles, tobramycin can displace fluorescein from the surface of nanoparticles resulting in nanoparticles aggregation and liberation of free fluorescein restoring its fluorescence. The interaction of tobramycin with fluorescein-bound silver nanoparticles is manifested by a decrease in the surface plasmon resonance band of silver nanoparticles at 395 nm, an increase in the fluorescence intensity of fluorescein at 513 nm and color change of the colloidal solution from yellow to light pink. These spectral effects are directly proportional to the concentration of tobramycin with a linearity range of 0.10 – 0.45 μg mL−1 and 0.05 – 0.45 μg mL−1 for the spectrophotometric and spectrofluorimetric methods, respectively. The proposed methods were applied for determination of tobramycin in Tobrin® ophthalmic solution with mean %recovery ± standard deviation of 99.036 ± 1.737 for the spectrophotometric method and 101.192 ± 1.315 for the spectrofluorimetric method. The optical sensor is simple, rapid, and cost-effective and can be used for determination of tobramycin in bulk and in its pharmaceutical preparations.

The Nocardial aph(2″) Gene Confers Tobramycin and Gentamicin Resistance and Is an Effective Positive Selection Marker in Mycobacteria and Nocardia.

The current study aimed to evaluate the feasibility of using the aminoglycoside 2″-O-phosphotransferase aph(2″) gene as a positive selection marker in N. asteroides, M. smegmatis, M. abscessus and M. tuberculosis. The aph(2″) gene, known to confer resistance to tobramycin, was PCR amplified from N. farcinica and cloned into two plasmid vectors, pMSG383 and pDB151, harboring hygromycin and zeocin selection markers, respectively. The recombinant plasmids were transformed into the target microorganisms, and selectability was assessed against varying concentrations of tobramycin and using an E-test against gentamicin. The results indicated that the aph(2″) gene is a useful selection marker in Mycobacteria and Nocardia against tobramycin, with a good selectability at 2.5-10 µg/mL for M. smegmatis mc2-155 and N. asteroides ATCC 19,247, and 60-160 µg/mL for M. abscessus ATCC 19,977 and M. tuberculosis H37Ra. The minimum inhibitory concentration (MIC) of gentamicin for recombinant N. asteroides, M. smegmatis and M. abscessus was >256 µg/mL, whereas respective MIC in wild-type strains was 0.125 µg/mL, 0.38 µg/mL and 8 µg/mL, respectively. These findings demonstrate the potential of aph(2″) as a positive selection marker for genetic manipulation processes in Mycobacteria and Nocardia, thus facilitating their research and improving the efficiency of biotechnology applications. Conclusions: the aph(2″) gene is a useful, new selection marker for genetic manipulation of Nocardia and various Mycobacteria.

Using seconds-resolved pharmacokinetic datasets to assess pharmacokinetic models encompassing time-varying physiology.

Pharmacokinetics have historically been assessed using drug concentration data obtained via blood draws and bench-top analysis. The cumbersome nature of these typically constrains studies to at most a dozen concentration measurements per dosing event. This, in turn, limits our statistical power in the detection of hours-scale, time-varying physiological processes. Given the recent advent of in vivo electrochemical aptamer-based (EAB) sensors, however, we can now obtain hundreds of concentration measurements per administration. Our aim in this paper was to assess the ability of these time-dense datasets to describe time-varying pharmacokinetic models with good statistical significance. We used seconds-resolved measurements of plasma tobramycin concentrations in rats to statistically compare traditional one- and two-compartmental pharmacokinetic models to new models in which the proportional relationship between a drug's plasma concentration and its elimination rate varies in response to changing kidney function. We found that a modified one-compartment model in which the proportionality between the plasma concentration of tobramycin and its elimination rate falls reciprocally with time either meets or is preferred over the standard two-compartment pharmacokinetic model for half of the datasets characterized. When we reduced the impact of the drug's rapid distribution phase on the model, this one-compartment, time-varying model was statistically preferred over the standard one-compartment model for 80% of our datasets. Our results highlight both the impact that simple physiological changes (such as varying kidney function) can have on drug pharmacokinetics and the ability of high-time resolution EAB sensor measurements to identify such impacts.

A fluorescent aptasensor based on ZIF-8 @PdNCs and DNA-AgNCs for tobramycin detection in milk

A novel ratiometric fluorescent aptasensor was constructed utilizing ZIF-8-encapsulated palladium nanoclusters (ZIF-8 @PdNCs) as reference signals that emit blue fluorescence, and DNA-templated silver nanoclusters (DNA-AgNCs) containing aptamer fragments as response signals that emit yellow fluorescence. In the absence of tobramycin (TOB), the aptamers of DNA-AgNCs bind to ZIF-8 @PdNCs via π-π stacking, resulting in the quenching of the fluorescent signals of DNA-AgNCs. The presence of TOB can weaken the π-π stacking interaction between ZIF-8 @PdNCs and single-stranded DNA (ssDNA) aptamers, which can lead to the desorption of DNA-AgNCs from the surface of ZIF-8 @PdNCs. As a result, the fluorescence signals of DNA-AgNCs are restored. The developed fluorescent sensor exhibits a linear range between 50 nM and 500 nM, with a limit of detection determined to be 15.3 nM. Exposure to UV light triggers a visible change in fluorescent color from blue to yellow as the concentration of TOB increases. To build a miniaturized and portable device for detecting TOB concentration, we employed 3D printing technology to create an RGB (Red Green Blue) instrument recognition framework with ultraviolet lamp beads and RGB recognition components. The RGB standard curve and programming in Python can be used to directly read the TOB concentration.

New Recommendations of a Height-Based Dosing Regimen of Tobramycin for Cystic Fibrosis in Adults: A Population Pharmacokinetic Analysis.

Acute pulmonary exacerbations (APEs) in patients with adult cystic fibrosis (CF) are treated with a beta-lactam and an aminoglycoside for activity against Pseudomonas aeruginosa (PA). Emerging drug resistance and changing pharmacokinetic profile in an aging population involve a reevaluation of tobramycin dosing recommendations. The objective of this study was to develop a population pharmacokinetic model and establish optimal dosing recommendations for tobramycin using Monte Carlo simulations. This retrospective clinical study and data collection were performed at the CF center of the McGill University Health Center (MUHC), Canada. Model development and simulations were performed using a nonlinear mixed-effect modeling approach (NONMEM, version 7.4.2). The ratios of maximal concentration (C max ) to the minimal inhibitory concentration (MIC) (C max /MIC ≥8 and ≥10) and area under the curve (AUC) to the MIC (AUC/MIC ≥70 and ≥100) were evaluated. Adult patients with CF (n = 51) treated with tobramycin were included in the study. Plasma concentrations of tobramycin were obtained for 699 samples from the MUHC database. The two-compartmental model best described the pharmacokinetics of tobramycin. The association of patient height with the central volume of distribution significantly improved this model. Height, rather than weight, induced the best reduction in objective function. According to simulations, doses between 3.4 mg/cm and 4.4 mg/cm were necessary to achieve C max /MIC values of ≥8 and ≥10, respectively. However, higher doses were required to achieve the AUC/MIC targets. This study demonstrated that height of the patients seems to be more suitable than their weight for dosing adjustments in adult patients with CF. According to this model, initial doses of tobramycin between 3.4 and 4.4 mg/cm should be recommended for patients with a median height of 164 cm and weight of 55 kg to achieve the target plasma concentrations.

CCCP Facilitates Aminoglycoside to Kill Late Stationary-Phase Escherichia coli by Elevating Hydroxyl Radical.

Improving the efficacy of existing antibiotics is significant for combatting antibiotic resistance that poses a major threat to human health. Carbonyl cyanide m-chlorophenylhydrazine (CCCP), a well-known protonophore for dissipating proton motive force (PMF), has been widely used to block the PMF-dependent uptake of aminoglycoside antibiotics and thus suppress aminoglycoside lethality. Here, we report that CCCP and its functional analog FCCP, but not other types of protonophores, unprecedently potentiate aminoglycosides (e.g., tobramycin and gentamicin) by 3-4 orders of magnitude killing of Escherichia coli, Staphylococcus aureus, Shigella flexneri, and Vibrio alginolyticus cells in stationary phase but not these cells in exponential phase nor other 12 bacterial species we examined. Overall, the effect of CCCP on aminoglycoside lethality undergoes a gradual transition from suppression against E. coli exponential-phase cells to potentiation against late stationary-phase cells, with the cell growth status and culture medium being crucial. Consistently, disturbance of the PMF by changing transmembrane proton gradient (ΔpH) or electric potential (ΔΨ) also potentiates tobramycin. Nevertheless, CCCP neither increases the intracellular concentration of tobramycin nor decreases the MIC of the antibiotic, thus excluding that CCCP acts as an efflux pump inhibitor to potentiate aminoglycosides. Rather, we show that the combined treatment dramatically enhances the cellular level of hydroxyl radical under both aerobic and anaerobic culturing conditions, under which the antioxidant N-acetyl cysteine fully suppresses both hydroxyl radical accumulation and cell death. Together, these findings open a new avenue to develop certain protonophores as aminoglycoside adjuvants against pathogens in stationary phase and also illustrate an essential role of hydroxyl radical in aminoglycoside lethality regardless of aerobic respiration.