Tobramycin Research Articles

Connecting Gut Microbial Diversity with Plasma Metabolome and Fecal Bile Acid Changes Induced by the Antibiotics Tobramycin and Colistin Sulfate.

The diversity of microbial species in the gut has a strong influence on health and development of the host. Further, there are indications that the variation in expression of gut bacterial metabolic enzymes is less diverse than the taxonomic profile, underlying the importance of microbiome functionality, particularly from a toxicological perspective. To address these relationships, the gut bacterial composition of Wistar rats was altered by a 28 day oral treatment with the antibiotics tobramycin or colistin sulfate. On the basis of 16S marker gene sequencing data, tobramycin was found to cause a strong reduction in the diversity and relative abundance of the microbiome, whereas colistin sulfate had only a marginal impact. Associated plasma and fecal metabolomes were characterized by targeted mass spectrometry-based profiling. The fecal metabolome of tobramycin-treated animals had a high number of significant alterations in metabolite levels compared to controls, particularly in amino acids, lipids, bile acids (BAs), carbohydrates, and energy metabolites. The accumulation of primary BAs and significant reduction of secondary BAs in the feces indicated that the microbial alterations induced by tobramycin inhibit bacterial deconjugation reactions. The plasma metabolome showed less, but still many alterations in the same metabolite groups, including reductions in indole derivatives and hippuric acid, and furthermore, despite marginal effects of colistin sulfate treatment, there were nonetheless systemic alterations also in BAs. Aside from these treatment-based differences, we also uncovered interindividual differences particularly centering on the loss of Verrucomicrobiaceae in the microbiome, but with no apparent associated metabolite alterations. Finally, by comparing the data set from this study with metabolome alterations in the MetaMapTox database, key metabolite alterations were identified as plasma biomarkers indicative of altered gut microbiomes resulting from a wide activity spectrum of antibiotics.

Target-induced Strand Displacement-based Electrochemical Aptasensor for the Determination of Tobramycin in Milk by Differential Pulse Voltammetry (DPV)

A target-induced strand displacement (TISD) electrochemical aptasensor is reported for the sensitive determination of tobramycin (TOB). A novel substrate was synthesized by loading cerium-based metal organic framework (Ce-MOF) that was modified by Pd nanoparticles (PdNPs), onto polyethyleneimine (PEI)-modified molybdenum disulfide (MoS2). The substrate (denoted by PEI-MoS2/Ce-MOF@PdNPs) was used to modify the Au electrode (AuE) to expand the electrode surface area for subsequent cDNA loading. Gold-platinum core–shell particles (Au@Pt) loaded with aptamers (Apt) were introduced as signal tags and mimetic peroxidase to hybridize with cDNA and form a double-stranded structure. When the target was present, strand displacement dominated by TISD occurred and the signal tag was released from the electrode surface, turning the signal off. Using the optimal conditions, the linear range of the sensor was from 5 × 10−11 to 1 × 10−6 mol/L and the detection limit was 1.05 × 10−12 mol/L with good stability, reproducibility, and specificity. The aptasensor provided good performance for the determination of tobramycin in milk.

Self-powered photoelectrochemical aptasensor based on hollow tubular g-C3N4/Bi/BiVO4 for tobramycin detection

A highly sensitive photoelectrochemical aptasensor based on phosphorus-doped hollow tubular g-C3N4/Bi/BiVO4 (PT-C3N4/Bi/BiVO4) for tobramycin (TOB) detecting was developed. This aptasensor is a self-powered sensing system which could generate the electrical output under visible light irradiation with no external voltage supply. Based on the surface plasmon resonance (SPR) effect and unique hollow tubular structure of PT-C3N4/Bi/BiVO4, the PEC aptasensor exhibited an enhanced photocurrent and favorably specific response to TOB. Under the optimized conditions, the sensitive aptasensor presented a wider linearity to TOB in the range of 0.01–50 ng mL−1 with a low detection limit of 4.27 pg mL−1. This sensor also displayed a satisfying photoelectrochemical performance with optimistic selectivity and stability. In addition, the proposed aptasensor was successfully applied to the detection of TOB in river water and milk samples.

Prevalence study of Pseudomonas aeruginosa in Teaching Tikrit Hospital from different sources.

In the current study,it was isolated 117 samples from different sources ,the isolates were identification using bacteriological and biochemical tests,(bacteria swabs uptaked from wound, otitis media ,stool and urine and), ,out of 117 samples. only 18 specimens was positive for P.aeruginosa (14%) in the otitis media,(14%) in the stool,(3%) in the wound and (0%) in the urine.all bacterial isolates identified through the using of bacterial and biochemical test ,.P.aeruginosa isolates showed highy resistance to most used antibiotics especially Ceftriaxon (CRO), Erythromycin (E), Cefixime (CFM)100% followed by Cefepime (FEP), Carbenicillin (PY)44%, Tobramycin (TOB)22% and Piperacillin (PRL)16.66% but Norfloxacin (NOR) show the attractive activities against all P.aeruginosa isolates ,the resistance was 0%.
 Conclusion: P.aeruginosa isolated in low prevalence in the Teaching Tikrit Hospital only in 15,38% ,all bacterial isolates was multi drug resistance (MDR) ,and resist to most used antibiotics expect Norfloxacin (NOR).

Role of Selective Digestive Decontamination in the Prevention of Ventilator-Associated Pneumonia in COVID-19 Patients: A Pre-Post Observational Study

The aim of our study was to evaluate whether the introduction of SDD in a structured protocol for VAP prevention was effective in reducing the occurrence of ventilator-associated pneumonia (VAP) in COVID-19 patients without changes in the microbiological pattern of antibiotic resistance. This observational pre-post study included adult patients requiring invasive mechanical ventilation (IMV) for severe respiratory failure related to SARS-CoV-2 admitted in three COVID-19 intensive care units (ICUs) in an Italian hospital from 22 February 2020 to 8 March 2022. Selective digestive decontamination (SDD) was introduced from the end of April 2021 in the structured protocol for VAP prevention. The SDD consisted of a tobramycin sulfate, colistin sulfate, and amphotericin B suspension applied in the patient's oropharynx and the stomach via a nasogastric tube. Three-hundred-and-forty-eight patients were included in the study. In the 86 patients (32.9%) who received SDD, the occurrence of VAP decreased by 7.7% (p = 0.192) compared to the patients who did not receive SDD. The onset time of VAP, the occurrence of multidrug-resistant microorganisms AP, the length of invasive mechanical ventilation, and hospital mortality were similar in the patients who received and who did not receive SDD. The multivariate analysis adjusted for confounders showed that the use of SDD reduces the occurrence of VAP (HR 0.536, CI 0.338-0.851; p = 0.017). Our pre-post observational study indicates that the use of SDD in a structured protocol for VAP prevention seems to reduce the occurrence of VAP without changes in the incidence of multidrug-resistant bacteria in COVID-19 patients.

Tailoring enzymatic loading capacity on CdS nanorods@ZnIn2S4 nanosheets 1D/2D heterojunctions: Toward ultrasensitive photoelectrochemical bioassay of tobramycin

Despite advances in the development of photoelectrochemical (PEC) sensor, modulating the PEC response of assembled heterostructure interface is still a great challenge. Here, an ultrasensitive PEC aptasensor for tobramycin (TOB) assay was conducted based on one-dimensional/two-dimensional CdS nanorods@ZnIn2S4 nanosheets (1D/2D CdS NRs@ZnIn2S4 NSs) heterojunctions by tailoring enzymatic loading capacity. Firstly, alkaline phosphatase modified TOB aptamer (ALP-Apt) was linked via specific base complementary pairing, and insoluble precipitations were then produced through the ALP-triggered catalytic reaction with the aid of Ag+, which prevented the charge transfer and resulted in the decrement of photocurrent. In the presence of TOB, partial ALP-Apt detached from the electrode surface due to the strong affinity between TOB and its aptamer, leading to a reduction in the amount of ALP and insoluble precipitate, in turn the PEC response partially recovered. The photocurrents exhibited a wider linear range towards the TOB concentration of 1.0–5.0 × 104 pg mL−1, with a low detection limit of 0.96 pg mL−1. The constructed PEC aptasensor gained satisfactory results for TOB assay in milk samples as well, which also offered significant promise for other pollutants in environmental analysis.

A tag-free fluorescent aptasensor for tobramycin detection using a hybridization of three aptamer strands and SYBR Green I dye

In this study, a sensitive fluorescent method is designed to detect tobramycin (TOB) drug applying a hybrid structure of three aptamer strands and SYBR Green I (SGI) fluorescent dye as the bioreceptor segment and signal indicator, respectively. The preferential binding of the aptamers to TOB resulted in the collapse of the hybridized aptamer skeleton to the single strands. So, the intercalation of SGI molecules reduced that quenched the fluorescence response. The aptasensing assay provided the superior target specificity with a detection limit (LOD) of 0.153 pM and a wide linear dynamic range over 0.5 pM–300 μM. The aptasensor could successfully quantify TOB in human serum samples. The tag-free sensor with the remarkable advantages of simplicity, easy-to-use, cost-effectiveness, and high sensitivity is superior to be applicable for clinical samples.

A novel "turn-off" photoelectrochemical aptasensing platform for selective detection of tobramycin based on the Ti3C2-MoS2/BiOI heterojunction.

Tobramycin (TOB), as a widely used antibiotic, poses severe unpredictable risks to ecology and health. In this study, a novel photoelectrochemical (PEC) adapter sensor, based on its "turn-off" PEC mode, was constructed for TOB detection. This visible-light-driven photoelectrochemical (PEC) aptasensor was successfully developed for TOB detection using Ti3C2-MoS2/BiOI and TOB aptamer probes. When TOB was captured by probes anchored on the modified electrode, a decreased photocurrent was also noted due to steric hindrance and this further hindered electron transfer. Under optimal conditions, 0.001 ng mL-1 to 40 ng mL-1 of TOB could be identified, with the detection limit being as low as 0.5 pg mL-1. At the same time, actual samples were also explored. Finally, the proposed sensor exhibited high specificity, satisfactory detectability and great reproducibility, thereby providing a novel approach for the detection of pollutants.

Albumin-coated pH-responsive dimeric prodrug-based nano-assemblies with high biofilm eradication capacity.

Pseudomonas aeruginosa (PA) biofilms cause many persistent chronic infections in humans, especially in cystic fibrosis (CF) patients. The biofilms form a strong barrier which may inhibit antimicrobial agents from penetrating the biofilms and killing PA bacteria that reside deep within the biofilms. Concomitant therapies based on tobramycin (TOB) and azithromycin (AZM) have demonstrated beneficial effects in CF patients with chronic PA infections. However, the co-delivery of TOB and AZM has rarely been reported. In this study, we constructed a self-assembled pH-sensitive nano-assembly (DPNA) based on a dimeric prodrug (AZM-Cit-TOB) by simply inserting citraconic amide bonds between AZM and TOB. Moreover, the cationic surface of DPNA was further modified with anionic albumin (HSA) via electrostatic interactions to form an electrostatic complex (termed HSA@DPNA) for better biocompatibility. Upon arrival at the infected tissues, the citraconic amide bonds would be cleaved at acidic pH, resulting in the release of TOB and AZM for bacteria killing and biofilm eradication. As expected, HSA@DPNA showed comparable antibacterial abilities against the P. aeruginosa strain PAO1 in both planktonic and biofilm modes of growth compared to the TOB/AZM mixture in vitro. Moreover, HSA@DPNA exhibited excellent therapeutic efficacy on mice with PAO1-induced lung infection compared to the TOB/AZM mixture, and no detectable toxicity to mammalian cells/animals was observed during the therapeutic process. In summary, our study provides a promising method for the co-delivery of AZM and TOB in concomitant therapies against PAO1-related infection.

A highly sensitive pre-column derivatization method for fluorescence detection of tobramycin using 2-naphthalenesulfonyl chloride as a derivatizing agent

A new, simple, rapid and highly sensitive high performance liquid chromatographic method was developed for the determination of tobramycin (TOB) in ophthalmic solutions. The developed method was based on derivatizing this non-chromophoric drug with 2-naphthalenesulfonyl chloride (NSCl), at 80 ºC for 40 min, and measuring the fluorescent product. Elution from the column was isocratic, using a mobile phase consisting of acetonitrile –1% phosphoric acid in water, (90:10, v/v), with a flow rate of 2 mL/min, at 40 ºC. Determination was developed using fluorescence detection at an excitation wavelength of 300 nm and an emission wavelength of 380 nm. The chromatographic separation was achieved on Knauer-Eurospher 100–5 C18 silica column (300 mm × 4 mm i.d, 5 μm). Different approaches were used to optimize the conditions of the method and to reach the maximum yield. The linear regression data for the calibration plot showed acceptable correlation coefficient (r2 = 0.9998) at the concentration ranges of 2.5–1000 ng/mL for TOB. The method was successfully validated according to the guidelines of the International Council on Harmonization, and was found suitable for pharmaceutical applications. The method was new, simple and precise for analysis of TOB and applicable for routine analysis in quality control laboratories.

1686. Antimicrobial Activity of Aztreonam-avibactam, Ceftazidime-Avibactam, and Comparator Agents against Pseudomonas aeruginosa from Cystic Fibrosis Patients

Abstract Background Aztreonam-avibactam (ATM-AVI) is under clinical development for the treatment of serious infections caused by Gram-negative bacteria, including MBL producers. Four other β-lactamase inhibitor combinations (BL/BLI) have been recently approved by the US FDA: ceftazidime-avibactam (CAZ-AVI), ceftolozane-tazobactam (C-T), meropenem-vaborbactam (MEM-VAB), and imipenem-relebactam (IMI-REL). We evaluated the in vitro activity of these 5 BL/BLIs and comparators against P. aeruginosa (PSA) causing cystic fibrosis (CF) pulmonary exacerbation. Methods 383 PSA isolates (1/patient) were recovered from 35 medical centers in the US (n=187) and 12 European countries (EU; n=196) in 2018-2021 and susceptibility tested by CLSI broth microdilution method. Results ATM-AVI inhibited 83.4%/85.2% of isolates from US/EU at ≤8 mg/L. CAZ-AVI (MIC50/90, 2/8 mg/L; 96.3%/95.4% susceptible [S] in US/EU) was the most active agent, followed by IMI-REL (94.7%/92.5%S in US/EU) and C-T (89.8%/91.3%S in US/EU). MEM-VAB (not approved for PSA in the US) and MEM showed similar activity. Tobramycin (TOB)-S rates were 73.3%/85.7% in US/EU (Table 1). Among TOB-non-S (NS) isolates, 84.6% were CAZ-AVI-S and 73.1% were inhibited at ATM-AVI MIC of ≤8 mg/L. CAZ-AVI retained good activity against C-T-NS (61.1%S), IMI-REL-NS (62.1%S), piperacillin-tazobactam (PIP-TAZ)-NS (86.7%S), meropenem (MEM)-NS (86.6%S), and ciprofloxacin (CIP)-NS (92.1%S) isolates (Table 2). Multidrug-resistant (MDR) and extensively drug-resistant (XDR) phenotypes were observed among 40.1%/30.1% and 24.6%/16.8% of isolates from US/EU, respectively. Among MDR isolates, 90.7%/84.7% were CAZ-AVI-S, 65.3%/66.1% were inhibited at ≤8 mg/L of ATM-AVI, and 78.7%/76.3% were TOB-S in US/EU. CAZ-AVI and TOB retained activity against 87.0%/75.8% and 39.1%/63.6% of XDR isolates in US/EU, respectively. Conclusion ATM-AVI and CAZ-AVI exhibited potent activity against PSA isolated from CF patients in US and EU and retained good activity against isolates resistant to other antimicrobials, including MDR and XDR organisms; both compounds showed greater activity than TOB. ATM-AVI and CAZ-AVI may represent a valuable option to treat CF patients with pulmonary exacerbations due to PSA infection. Disclosures Helio S. Sader, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Pfizer: Grant/Research Support Leonard R. Duncan, PhD, AbbVie: Grant/Research Support Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Office for Assistant Secretary of Defense for Health Affairs: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support|Spero Therapeutics: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support.

A label-free liquid crystal-assisted aptasensor for trace level detection of tobramycin in milk and chicken egg samples

Developed herein is an aptasensing array based on liquid crystal (LC) for monitoring of tobramycin (TOB) antibiotic. The direction of LC molecules from vertical to a random status was induced by the conformational changes of the specific aptamer due to its selective interaction with the target. The dark view of the aptasensing platform changed to colorful through observation by a polarized light microscope that clarifies the TOB presence. The aptasensor is especially able to determine TOB in the linear concentration range of 0.005–600 pM with a limit of detection (LOD) as 0.0021 pM. The TOB values can be determined successfully in the milk and chicken egg samples that highlights the potential applicability of the designed aptasensor. The proposed sensing approach is facile, operator-independent, label-free, and ultra-sensitive, making it novel for developing real-time portable sensing devices for future.

Bilayer magnetic-plasmonic satellite nanoassemblies for SERS detection of tobramycin with exonuclease amplification

Nanoscale assemblies designed for trace analyte detection typically require a complex fabrication process. Here, we prepare magnetic nanoparticle (Fe3O4)-gold nanoparticle (AuNP)-gold nanostar (AuNS) bilayer magnetic-plasmonic satellite nanoassemblies (BMPSNs) for ultrasensitive detection of tobramycin (TOB). BMPSNs are constructed through seed-mediated growth and complementary DNA hybridization, combining magnetic separation and surface-enhanced Raman scattering (SERS) activities. AuNP is in situ growth on the surface of Fe3O4 to form the monolayer satellite assemblies. Partially complementary double-stranded DNA (DNA1/DNA2) is modified onto the surface of the first layer satellite AuNP. TOB aptamer (Apt) and fully complementary DNA (cDNA) form the duplex DNA. In the presence of TOB, cDNA of TOB Apt is replaced by TOB/TOB Apt, which can hybridize with DNA2 modified on the surface of Fe3O4@AuNP-DNA1/DNA2 and further triggers exonuclease III cyclic amplification to obtain Fe3O4@AuNP-DNA1. Finally, Fe3O4@AuNP-DNA1 can assemble with AuNS@4-MBA-DNA3 through DNA hybridization to form BMPSNs. Thanks to excellent magnetic separation, exonuclease amplification and huge SERS enhancement of multiple hot spots, the limit of detection can achieve as low as 0.44 fg/mL of TOB, which is more sensitive than the previously reported methods. In addition, this method can be applied to TOB detection in actual samples with good recoveries and without interference by other antibiotics. The proposed method can be easily extended to sensitive detection of other targets by replacing the corresponding aptamers, paving a new avenue for food safety and environment monitoring.

Meropenem-loaded Cement Is Effective in Preventing Gram-negative Osteomyelitis in an Animal Model.

Low-dose antibiotic-loaded acrylic cement is routinely used for preventing skeletal infection or reimplantation in patients with periprosthetic joint infections. However, few reports about the selection of antibiotics in acrylic cement for antigram-negative bacteria have been proposed. (1) Does the addition of antibiotics (tobramycin, meropenem, piperacillin, ceftazidime, ciprofloxacin, and aztreonam) to acrylic cement adversely affect compressive strength before and after elution? (2) Which antibiotics have the highest cumulative release within 28 days? (3) Which antibiotics showed antimicrobial activity within 28 days? (4) Does meropenem-loaded cement improve body weight, temperature, and other inflammatory markers compared with control unloaded cement? This is an in vitro study that assessed the mechanical strength, antibiotic elution, and antibacterial properties of antibiotic-loaded cement, combined with an animal study in a rat model that evaluated key endpoints from the animal study. In the in vitro study, we added 2 g of tobramycin (TOB), meropenem (MEM), piperacillin (PIP), ceftazidime (CAZ), ciprofloxacin (CIP), and aztreonam (ATM) to 40 g of acrylic cement. The compressive strength, elution, and in vitro antibacterial properties of the antibiotic-loaded cement were detected. Thirty male rats were randomly divided into two groups: CON (antibiotic-unloaded cement) and MEM (meropenem-loaded cement, which had the most stable antibacterial properties of the six tested antibiotic-loaded cements in vitro within 28 days). The right tibia of all rats underwent arthroplasty and was implanted with the cement, followed by inoculation with Pseudomonas aeruginosa in the knee. General status, serum biomarkers, radiology, microbiological assay, and histopathological tests were assessed over 14 days postoperatively. The compressive strength of all tested antibiotic cement combinations exceeded the 70 MPa threshold (the requirement established in ISO 5833). The cumulative release proportions of the raw antibiotic in cement were 1182.8 ± 37.9 µg (TOB), 355.6 ± 16.2 µg (MEM), 721.2 ± 40.3 µg (PIP), 477.4 ± 37.1 µg (CAZ), 146.5 ± 11.3 µg (CIP), and 372.1 ± 14.5 µg (ATM) within 28 days. Over a 28-day period, meropenem cement demonstrated antimicrobial activities against the four tested gram-negative bacteria ( Escherichia coli , P. aeruginosa , Klebsiella pneumoniae , and Proteus vulgaris ). Ciprofloxacin cement inhibited E. coli growth, ceftazidime and aztreonam cement inhibited K. pneumonia growth, and tobramycin cement inhibited P. aeruginosa . Only meropenem demonstrated antimicrobial activity against all gram-negative bacteria on agar diffusion bioassay. Rats treated with meropenem cement showed improved body weight (control: 280.1 ± 4.2 g, MEM: 288.5 ± 6.6 g, mean difference 8.4 [95% CI 4.3 to 12.6]; p < 0.001), improved knee width (control: 13.5 ± 0.3 mm, MEM: 11.8± 0.4 mm, mean difference 1.7 [95% CI 1.4 to 2.0]; p < 0.001), decreased inflammatory marker (control: 316.7 ± 45.0 mm, MEM: 116.5 ± 21.8 mm, mean difference 200.2 [95% CI 162.3 to 238.2]; p < 0.001), decreased radiographic scores (control: 17.7 ± 2.0 mm, MEM: 10.7± 1.3 mm, mean difference 7.0 [95% CI 5.4 to 8.6]; p < 0.001), improved bone volume/total volume (control: 8.7 ± 3.0 mm, MEM: 28.5 ± 5 .5 mm, mean difference 19.8 [95% CI 13.3 to 26.2]; p < 0.001), decreased Rissing scale scores of the knee gross pathology (control: 3.3 ± 0.5, MEM: 1.1 ± 0.7, mean difference 2.2 [95% CI 1.7 to 2.7]; p < 0.001), decreased Petty scale scores of knee synovium (control: 2.9 ± 0.4 mm, MEM: 0.7 ± 0.7 mm, mean difference 2.1 [95% CI 1.7 to 2.5]; p < 0.001), and decreased bacterial counts of the bone and soft tissues and negative bacterial cultures of cement (p < 0.001, p < 0.001, p < 0.001, p < 0.001, respectively). In this current study, MEM cement had the most stable in vitro antimicrobial activities, effective in vivo activity while having acceptable mechanical and elution characteristics, and it may be an effective prophylaxis against skeletal infection caused by gram-negative bacteria. Meropenem-loaded acrylic cement is a potentially effective prevention measure for skeletal infection caused by gram-negative bacteria; however, more related clinical research is needed to further evaluate the safety and efficacy.

“Turn-off” photoelectrochemical aptasensor based on g-C3N4/WC/WO3 composites for tobramycin detection

Tobramycin (TOB), as a widely used antibiotic, poses severe unpredictable risks to ecology and health. Here, a novel photoelectrochemical (PEC) aptasensor based on a “turn-off” PEC mode was constructed for TOB detection. The working electrode could be modified by g-C3N4/WC/WO3 composites and TOB aptamer probes in turn. The TOB aptamer probes could anchor on the g-C3N4/WC/WO3 through π-π stacking interaction to avoid interference from other modifications. When TOB was captured by the aptamer probes anchored on the modified fluorine-doped tin oxide (FTO) electrode, a decreased photocurrent was obtained owing to steric hindrance and hinder electron transfer. Under optimal conditions, 0.005–5 ng mL−1 of TOB could be detected with a detection limit as low as 2 pg mL−1. Meanwhile, actual samples were investigated as well. The proposed sensor shows high specificity, satisfactory detectability, great reproducibility, and may provide a new thought for detecting other pollutants.

Electrochemical Quantification of Tobramycin Retention in Pseudomonas aeruginosa as Antimicrobial Susceptibility Indicator.

The emergence and spread of bacterial resistance to antibiotics has developed into one of the most challenging threats to public health. Antibiotic susceptibility tests (ASTs) for bacterial infections are now essential, because they provide guidance for physicians in the selection of antibiotics, to which bacteria will respond. Most current AST methods require long periods of time, because of bacterial growth and incubation, leading to a prolonged and overuse of broad-spectrum antibiotics. Thus, there is a growing demand for methods and technologies that enable rapid antibiotic susceptibility assessment. Due to advantages related to cost-effectiveness, rapid response time and high sensitivity, electrochemical detection methods are promising analytical tools that can successfully quantify antibiotic uptake and retention in clinically relevant bacterial strains. This study presents the electroanalytical quantification of tobramycin (TOB) retention in susceptible and resistant bacterial strains of Pseudomonas aeruginosa. The electrochemical behavior of TOB was characterized by voltammetry, identifying redox potentials, the current dependence on pH conditions, and the detection limit at unmodified glassy carbon electrodes. The presented methodology was able to distinguish between susceptible and resistant bacterial strains, and is also capable of identifying varying degrees of resistance against TOB. The presented approach detects the immediate interaction of bacteria with an antibiotic, without the need of complex and cost-intense equipment related to genomic testing methods.

Bacterial Growth-Induced Tobramycin Smart Release Self-Healing Hydrogel for Pseudomonas aeruginosa-Infected Burn Wound Healing.

Burns are a common health problem worldwide and are highly susceptible to bacterial infections that are difficult to handle with ordinary wound dressings. Therefore, burn wound repair is extremely challenging in clinical practice. Herein, a series of self-healing hydrogels (QCS/OD/TOB/PPY@PDA) with good electrical conductivity and antioxidant activity were prepared on the basis of quaternized chitosan (QCS), oxidized dextran (OD), tobramycin (TOB), and polydopamine-coated polypyrrole nanowires (PPY@PDA NWs). These Schiff base cross-links between the aminoglycoside antibiotic TOB and OD enable TOB to be slowly released and responsive to pH. Interestingly, the acidic substances during the bacteria growth process can induce the on-demand release of TOB, avoiding the abuse of antibiotics. The antibacterial results showed that the QCS/OD/TOB/PPY@PDA9 hydrogel could kill high concentrations of Pseudomonas aeruginosa (PA), Staphylococcus aureus, and Escherichia coli in a short time and showed a bactericidal effect for up to 11 days in an agar plate diffusion experiment, while showing good in vivo antibacterial activity. Excellent and long-lasting antibacterial properties make it suitable for severely infected wounds. Furthermore, the incorporation of PPY@PDA endowed the hydrogel with near-infrared (NIR) irradiation assisted bactericidal activity of drug-resistant bacteria, conductivity, and antioxidant activity. Most importantly, in the PA-infected burn wound model, the QCS/OD/TOB/PPY@PDA9 hydrogel more effectively controlled wound inflammation levels and promoted collagen deposition, vascular generation, and earlier wound closure compared to Tegaderm dressings. Therefore, the TOB smart release hydrogels with on-demand delivery are extremely advantageous for bacterial-infected burn wound healing.

Intramedullary Canal Injection of Vancomycin- and Tobramycin-loaded Calcium Sulfate: A Novel Technique for the Treatment of Chronic Intramedullary Osteomyelitis.

AimIn this study, we present a detailed surgical technique for treating chronic osteomyelitis (COM) of the intramedullary canal with injectable tobramycin and vancomycin-loaded calcium sulfate (CS).BackgroundChronic osteomyelitis of the long bones has been treated using antibiotic-impregnated polymethyl methacrylate (PMMA), which typically requires a second procedure for removal.TechniqueRemoval of the infected intramedullary nail (if any), copious irrigation, canal reaming, and intramedullary canal injection of vancomycin- and tobramycin-loaded calcium sulfate as a single-stage procedure for the treatment of COM of long bones.ConclusionIntramedullary injection of vancomycin- and tobramycin-loaded CS can be used as a single-stage procedure for the treatment of long bone intramedullary COM. Further studies are necessary to compare the long-term outcomes of antibiotic-coated CS vs other antibiotic carriers for infection eradication.Clinical significanceThe authors have endeavored to explain the best surgical technique to eradicate long bones COM with injectable tobramycin and vancomycin-loaded CS.How to cite this articleElhessy AH, Rivera JC, Shu HT, et al. Intramedullary Canal Injection of Vancomycin- and Tobramycin-loaded Calcium Sulfate: A Novel Technique for the Treatment of Chronic Intramedullary Osteomyelitis. Strategies Trauma Limb Reconstr 2022;17(2):123–130.

Electrochemical Detection of Tobramycin Resistance in Pseudomonas Aeruginosa

Pseudomonas aeruginosa are Gram-negative anaerobic bacteria and is listedby the World Health Organization as one of the critical antibiotic-resistant pathogens1. The treatment for P. aeruginosa infection can be challenging, since this pathogen often exhibits an enhanced resistance to antibiotics, including aminoglycosides, such as Tobramycin (TOB). These are called mucoid strains and are mainly found in the lungs of cystic fibrosis patients, where it is a common cause of death for these individuals2. The overall goal of the presented work is the development of an electrochemical method capable of detecting TOB uptake in P. aeruginosa. Drug susceptible and drug resistant strains of P. aeruginosa were exposed to a TOB solution for different time intervals (Figure 1). By removing organisms from the solution after incubation, the remaining TOB in solution can be determined by electrochemistry. Resistant bacteria strains showed significantly lower TOB uptake than susceptible organisms, because cellular drug resistant mechanisms enable them to inhibit TOB absorption. The presented drug uptake studies demonstrate the sensitivity of electrochemistry to detect drug resistance in living bacteria. References Singh, M., Yau, Y. C. W., Wang, S., Waters, V. & Kumar, A. MexXY efflux pump overexpression and aminoglycoside resistance in cystic fibrosis isolates of pseudomonas aeruginosa from chronic infections. Canadian Journal of Microbiology 63, 929–938 (2017).Germoni, L. A. P., Bremer, P. J. & Lamont, I. L. The effect of alginate lyase on the gentamicin resistance of Pseudomonas aeruginosa in mucoid biofilms. Journal of Applied Microbiology 121, 126–135 (2016). Figure 1

Synergistic Activity of Repurposed Peptide Drug Glatiramer Acetate with Tobramycin against Cystic Fibrosis Pseudomonas aeruginosa.

ABSTRACTPseudomonas aeruginosa is the most common pathogen infecting the lungs of people with cystic fibrosis (CF), causing both acute and chronic infections. Intrinsic and acquired antibiotic resistance, coupled with the physical barriers resulting from desiccated CF sputum, allow P. aeruginosa to colonize and persist in spite of antibiotic treatment. As well as the specific difficulties in eradicating P. aeruginosa from CF lungs, P. aeruginosa is also subject to the wider, global issue of antimicrobial resistance. Glatiramer acetate (GA) is a peptide drug, used in the treatment of multiple sclerosis (MS), which has been shown to have moderate antipseudomonal activity. Other antimicrobial peptides (AMPs) have been shown to be antibiotic resistance breakers, potentiating the activities of antibiotics when given in combination, restoring and/or enhancing antibiotic efficacy. Growth, viability, MIC determinations, and synergy analysis showed that GA improved the efficacy of tobramycin (TOB) against reference strains of P. aeruginosa, reducing TOB MICs and synergizing with the aminoglycoside. This was also the case for clinical strains from people with CF. GA significantly reduced the MIC50 of TOB for viable cells from 1.69 mg/L (95% confidence interval [CI], 0.26 to 8.97) to 0.62 mg/L (95% CI, 0.15 to 3.94; P = 0.002) and the MIC90 for viable cells from 7.00 mg/L (95% CI, 1.18 to 26.50) to 2.20 mg/L (95% CI, 0.99 to 15.03; P = 0.001), compared to results with TOB only. Investigation of mechanisms of GA activity showed that GA resulted in significant disruption of outer membranes, depolarization of cytoplasmic membranes, and permeabilization of P. aeruginosa and was the only agent tested (including cationic AMPs) to significantly affect all three mechanisms.IMPORTANCE The antimicrobial resistance crisis urgently requires solutions to the lost efficacy of antibiotics. The repurposing of drugs already in clinical use, with strong safety profiles, as antibiotic adjuvants to restore the efficacy of antibiotics is an important avenue to alleviating the resistance crisis. This research shows that a clinically used drug from outside infection treatment, glatiramer acetate, reduces the concentration of tobramycin required to be effective in treating Pseudomonas aeruginosa, based on analyses of both reference and clinical respiratory isolates from people with cystic fibrosis. The two agents acted synergistically against P. aeruginosa, being more effective combined in vitro than predicted for their combination. As a peptide drug, glatiramer acetate functions similarly to many antimicrobial peptides, interacting with and disrupting the P. aeruginosa cell wall and permeabilizing bacterial cells, thereby allowing tobramycin to work. Our findings demonstrate that glatiramer acetate is a strong candidate for repurposing as an antibiotic resistance breaker of pathogenic P. aeruginosa.