Tobramycin Systemic Absorption in Lung Transplant Recipients Treated With Inhaled Tobramycin: A Cohort Study.

Inhaled tobramycin treatment has been associated with nephrotoxicity in some case reports, but limited data are available about serum levels and its possible systemic absorption in lung transplant recipients (LTR). We conducted a single-center, observational and retrospective study of all adult (>18 years old) LTR treated with inhaled tobramycin for at least 3 days between June 2019 and February 2022. Trough serum levels were collected and >2 µg/mL was considered a high drug level. The primary outcome assessed the presence of detectable trough levels, while the secondary outcome focused on the occurrence of acute kidney injury (AKI) in individuals with detectable trough levels. Thirty-four patients, with a median age of 60 years, were enrolled. The primary indications for treatment were donor bronchial aspirate bacterial isolation (18 patients) and tracheobronchitis (15 patients). In total, 28 patients (82%) exhibited detectable serum levels, with 9 (26%) presenting high levels (>2 µg/mL). Furthermore, 9 patients (26%) developed acute kidney injury during the treatment course. Median trough tobramycin levels were significantly elevated in invasively mechanically ventilated patients compared to non-ventilated individuals (2.5 µg/mL vs. 0.48 µg/mL) (p < 0.001). Inhaled tobramycin administration in LTRs, particularly in those requiring invasive mechanical ventilation, may result in substantial systemic absorption.

Zein nanoparticles containing ceftazidime and tobramycin: antibacterial activity against Gram-negative bacteria.

Aims: This work describes the encapsulation of ceftazidime and tobramycin in zein nanoparticles (ZNPs) and the characterization of their antibacterial and antibiofilm activities against Gram-negative bacteria. Materials & methods: ZNPs were synthesized by nanoprecipitation. Cytotoxicity was assessed by MTT assay and antibacterial and antibiofilm assays were performed by broth microdilution and violet crystal techniques. Results: ZNPs containing ceftazidime (CAZ-ZNPs) and tobramycin (TOB-ZNPs) showed drug encapsulation and thermal stability. Encapsulation of the drugs reduced their cytotoxicity 9-25-fold. Antibacterial activity, inhibition and eradication of biofilm by CAZ-ZNPs and TOB-ZNPs were observed. There was potentiation when CAZ-ZNPs and TOB-ZNPs were combined. Conclusion: CAZ-ZNPs and TOB-ZNPs present ideal physical characteristics for in vivo studies of antibacterial and antibiofilm activities.

A nanotechnology product was developed to treat diseases caused by bacteria. This prototype showed the ideal characteristics and could be administered by ingestion through the mouth, aspiration through the nose or injection into the veins. The prototype did not harm or kill human cells. It killed the bacteria and prevented the formation of a type of protection against antibiotics that bacteria can produce, called a biofilm. Nanotechnology products are a promising alternative for the treatment of bacterial infections.

Mutations in the efflux pump regulator MexZ shift tissue colonization by Pseudomonas aeruginosa to a state of antibiotic tolerance.

Mutations in mexZ, encoding a negative regulator of the expression of the mexXY efflux pump genes, are frequently acquired by Pseudomonas aeruginosa at early stages of lung infection. Although traditionally related to resistance to the first-line drug tobramycin, mexZ mutations are associated with low-level aminoglycoside resistance when determined in the laboratory, suggesting that their selection during infection may not be necessarily, or only, related to tobramycin therapy. Here, we show that mexZ-mutated bacteria tend to accumulate inside the epithelial barrier of a human airway infection model, thus colonising the epithelium while being protected against diverse antibiotics. This phenotype is mediated by overexpression of lecA, a quorum sensing-controlled gene, encoding a lectin involved in P. aeruginosa tissue invasiveness. We find that lecA overexpression is caused by a disrupted equilibrium between the overproduced MexXY and another efflux pump, MexAB, which extrudes quorum sensing signals. Our results indicate that mexZ mutations affect the expression of quorum sensing-regulated pathways, thus promoting tissue invasiveness and protecting bacteria from the action of antibiotics within patients, something unnoticeable using standard laboratory tests.

Optimization of an in vitro Pseudomonas aeruginosa Biofilm Model to Examine Antibiotic Pharmacodynamics at the Air-Liquid Interface.

Pseudomonas aeruginosa is an important cause of lower respiratory tract infections, such as ventilator-associated bacterial pneumonia (VABP). Using inhaled antibiotics to treat VABP can achieve high drug concentrations at the infection site while minimizing systemic toxicities. Despite the theoretical advantages, clinical trials have failed to show a benefit for inhaled antibiotic therapy in treating VABP. A potential reason for this discordance is the presence of biofilm-embedded bacteria in lower respiratory tract infections. Drug selection and dosing are often based on data from bacteria grown planktonically. In the present study, an in vitro air-liquid interface pharmacokinetic/pharmacodynamic biofilm model was optimized to evaluate the activity of simulated epithelial lining fluid exposures of inhaled and intravenous doses of polymyxin B and tobramycin against two P. aeruginosa strains. Antibiotic activity was also determined against the P. aeruginosa strains grown planktonically. Our study revealed that inhaled antibiotic exposures were more active than their intravenous counterparts across biofilm and planktonic populations. Inhaled exposures of polymyxin B and tobramycin exhibited comparable activity against planktonic P. aeruginosa. Although inhaled polymyxin B exposures were initially more active against P. aeruginosa biofilms (through 6 h), tobramycin was more active by the end of the experiment (48 h). Together, these data slightly favor the use of inhaled tobramycin for VABP caused by biofilm-forming P. aeruginosa that are not resistant to either antibiotic. The optimized in vitro air-liquid interface pharmacokinetic/pharmacodynamic biofilm model may be beneficial for the development of novel anti-biofilm agents or to optimize antibiotic dosing for infections such as VABP.

Enhancing bactericidal activities of ciprofloxacin by targeting the trans-translation system that is involved in stress responses in Klebsiella pneumoniae.

Although the trans-translation system is a promising target for antcibiotic development, its antibacterial mechanism in Klebsiella pneumoniae (KP) is unclear. Considering that tmRNA was the core component of trans-translation, this study firstly investigated phenotypic changes caused by various environmental stresses in KP lacking trans-translation activities (tmRNA-deleted), and then aimed to evaluate antibacterial activities of the trans-translation-targeting antibiotic combination (tobramycin/ciprofloxacin) in clinical KP isolates based on inhibition activities of aminoglycosides against trans-translation. We found that the tmRNA-deleted strain P4325/ΔssrA was significantly more susceptible than the wild-type KP strain P4325 under environments with hypertonicity (0.5 and 1 M NaCl), hydrogen peroxide (40 mM), and UV irradiation. No significant differences in biofilm formation and survivals under human serum were observed between P4325/ΔssrA and P4325. tmRNA deletion caused twofold lower MIC values for aminoglycosides. As for the membrane permeability, tmRNA deletion increased ethidium bromide (EtBr) uptake of KP in the presence or absence of verapamil and carbonyl cyanide-m-chlorophenylhydrazone (CCCP), decreased EtBr uptake in presence of reserpine in P4325/ΔssrA, and reduced EtBr efflux in P4325/ΔssrA in the presence of CCCP. The time-kill curve and in vitro experiments revealed significant bactericidal activities of the tmRNA-targeting aminoglycoside-based antibiotic combination (tobramycin/ciprofloxacin). Thus, the corresponding tmRNA-targeting antibiotic combinations (aminoglycoside-based) might be effective and promising treatment options against multi-drug resistant KP.

Murepavadin promotes the killing efficacies of aminoglycoside antibiotics against Pseudomonas aeruginosa by enhancing membrane potential.

Murepavadin is a peptidomimetic that specifically targets the lipopolysaccharide transport protein LptD of Pseudomonas aeruginosa. Here, we found that murepavadin enhances the bactericidal efficacies of tobramycin and amikacin. We further demonstrated that murepavadin enhances bacterial respiration activity and subsequent membrane potential, which promotes intracellular uptake of aminoglycoside antibiotics. In addition, the murepavadin-amikacin combination displayed a synergistic bactericidal effect in a murine pneumonia model.

Bacteria can compensate the fitness costs of amplified resistance genes via a bypass mechanism.

Antibiotic heteroresistance is a phenotype in which a susceptible bacterial population includes a small subpopulation of cells that are more resistant than the main population. Such resistance can arise by tandem amplification of DNA regions containing resistance genes that in single copy are not sufficient to confer resistance. However, tandem amplifications often carry fitness costs, manifested as reduced growth rates. Here, we investigated if and how these fitness costs can be genetically ameliorated. We evolved four clinical isolates of three bacterial species that show heteroresistance to tobramycin, gentamicin and tetracyclines at increasing antibiotic concentrations above the minimal inhibitory concentration (MIC) of the main susceptible population. This led to a rapid enrichment of resistant cells with up to an 80-fold increase in the resistance gene copy number, an increased MIC, and severely reduced growth rates. When further evolved in the presence of antibiotic, these strains acquired compensatory resistance mutations and showed a reduction in copy number while maintaining high-level resistance. A deterministic model indicated that the loss of amplified units was driven mainly by their fitness costs and that the compensatory mutations did not affect the loss rate of the gene amplifications. Our findings suggest that heteroresistance mediated by copy number changes can facilitate and precede the evolution towards stable resistance.

Therapeutic effect of intense pulsed light on different types of chalazion in children.

This study aims to investigate the effectiveness of Intense Pulsed Light (IPL) therapy for chalazion treatment while also exploring potential variations in sensitivity among different types of chalazion. A total of 149 patients were selected to receive tobramycin combined with IPL treatment and tobramycin combined with hot compress. The treatment groups were divided into cystic type and granulomatous type according to different clinical manifestations. The course of treatment was 3 weeks. The improvement was based on the ultrasound measurement of the masses reduction of more than 50% or disappearance. In the IPL group, 17 (22.67%) cases were cured, 39 (52.00%) were effective, and 19 (25.33%) were ineffective. This includes: cystic type was cured in 3 (15.79%), effective in 5 (26.32%) cases, ineffective in 11 (57.89%) cases; granulomatous type was cured in 14 (25.00%) cases, effective in 34 (60.71%) cases, ineffective in 8 (14.29%) cases. In the hot compress group, 5 (6.76%) cases were cured, 16 (21.62%) cases were effective and 53 (71.62%) cases were ineffective. The cystic type was cured in 2 (8.00%) cases, effective in 3 (12.00%) cases and ineffective in 20 (80.00%) cases; the granulomatous type was cured in 3 (6.12%) cases, effective in 13 (26.53%) cases and ineffective in 33 (67.35%) cases. The cure rate and efficacy rate of IPL treatment is higher than that of hot compress treatment, the treatment effect of IPL treatment on granulomatous chalazion is better than that on cystic type.

Combination treatment to improve mucociliary transport of Pseudomonas aeruginosa biofilms.

People with muco-obstructive pulmonary diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) often have acute or chronic respiratory infections that are difficult to treat due in part to the accumulation of hyperconcentrated mucus within the airway. Mucus accumulation and obstruction promote chronic inflammation and infection and reduce therapeutic efficacy. Bacterial aggregates in the form of biofilms exhibit increased resistance to mechanical stressors from the immune response (e.g., phagocytosis) and chemical treatments including antibiotics. Herein, combination treatments designed to disrupt the mechanical properties of biofilms and potentiate antibiotic efficacy are investigated against mucus-grown Pseudomonas aeruginosa biofilms and optimized to 1) alter biofilm viscoelastic properties, 2) increase mucociliary transport rates, and 3) reduce bacterial viability. A disulfide bond reducing agent (tris(2-carboxyethyl)phosphine, TCEP), a surfactant (NP40), a biopolymer (hyaluronic acid, HA), a DNA degradation enzyme (DNase), and an antibiotic (tobramycin) are tested in various combinations to maximize biofilm disruption. The viscoelastic properties of biofilms are quantified with particle tracking microrheology and transport rates are quantified in a mucociliary transport device comprised of fully differentiated primary human bronchial epithelial cells. The combination of the NP40 with hyaluronic acid and tobramycin was the most effective at increasing mucociliary transport rates, decreasing the viscoelastic properties of mucus, and reducing bacterial viability. Multimechanistic targeting of biofilm infections may ultimately result in improved clinical outcomes, and the results of this study may be translated into future in vivo infection models.

Tobramycin and Vancomycin in an In Vitro Model of Anterior Cruciate Ligament Allograft Decontamination.

BACKGROUND: Approximately 100,000 anterior cruciate ligament (ACL) reconstructions (ACLRs) occur annually in the United States, and postoperative surgical-site infection is a relatively rare but devastating complication, often leading to graft failure or septic arthritis of the knee, necessitating repeat surgery. Wrapping allografts in vancomycin-soaked gauze has been adopted as a common sterilization technique in the operating room to reduce surgical-site infection; however, identifying effective alternatives to vancomycin has not been extensively pursued. HYPOTHESIS: Tobramycin would be as effective as vancomycin in reducing the concentrations of Staphylococcus epidermidis bacteria on tendon allografts. STUDY DESIGN: Controlled laboratory study. METHODS: S. epidermidis strain ATCC 12228 was inoculated onto the human cadaveric gracilis tendon. The tendons were wrapped in sterile gauze saturated with tobramycin or vancomycin at various experimental concentrations. Bacteria remaining on the tendon were dislodged, serially diluted, and plated for colony counting. Statistical analysis was performed utilizing 2-way analysis of variance testing. Results were considered statistically significant when P < .05. RESULTS: Vancomycin (P = .0001) and tobramycin (P < .0001) reduced bacterial concentration. Tobramycin was found to produce a statistically significant reduction in bacterial concentration at concentrations as low as 0.1 mg/mL (P < .0001 and P = .01 at 10 and 20 minutes), while vancomycin produced a statistically significant reduction at a concentration as low as 2.5 mg/mL (P < .0001 at both 10 and 20 minutes). CONCLUSION: This study demonstrates that tobramycin is as effective as vancomycin in bacterial concentration reduction but can achieve this reduction level at lower doses. Further studies clarifying the biomechanical and cytotoxic effects of tobramycin on tendon tissue are indicated to solidify its use as a clinical alternative to vancomycin in ACLR. CLINICAL RELEVANCE: These results will begin establishing tobramycin as an alternative to vancomycin in ACL graft decontamination. Because of relatively frequent shortages of vancomycin, establishing tobramycin as an alternative agent is a useful option for the orthopaedic surgeon.

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.

Simultaneous determination of amphotericin B, tobramycin and vancomycin in rabbit ocular biofluids and tissues by LC-MS/MS: An antimicrobial therapy for keratitis and its PK-PD application.

A rationale poly-microbial keratitis (PMK) therapy requires quick identification of pathogen (bacteria and fungi) and their efficient treatment. However, majority of healthcare providers are still having trouble finding an effective medicine to treat PMK due to constraints such as antimicrobial resistance, dose and dosing schedule. Thus, a broad spectrum anti-fungal and antibacterial having less resistance in community involving combination therapy such as amphotericin B (AmB), tobramycin (TBR) and vancomycin (VCM) is required. Hence, to characterize the pharmacokinetic (PK) and PK-pharmacodynamic (PD) indices, a rapid and sensitive simultaneous LC-MS/MS bioanalytical method was developed and validated for the quantification of AmB, TBR and VCM in rabbit ocular biofluids and tissues. Chromatographic resolution was achieved on a Zorbax C18 column with a mobile phase composed of acetonitrile and 0.4 % formic acid in deionized water using a gradient mode of elution. The calibration curves showed good linearity over the concentration range of 1.95-500 ng/mL for AmB and TBR, 3.9-800 ng/mL for VCM, respectively. The lower limit of quantification (LLOQ) was found to be 1.95 ng/mL for AmB and TBR, and 4.5 ng/mL for VCM. Analyte extraction was performed by simple protein precipitation method with minimal sample volume of 10 µL. Finally, the developed method was validated for selectivity, linearity (r2 > 0.99), precision, accuracy, matrix effects, and stability. The ocular pharmacokinetic profile of commercial AmB, TBR, and VCM formulations was further assessed using the validated method and the PK-PD indices along with dosing frequency was predicted by PK-PD modelling using Phoenix WinNonlin Software.

The Effect of Vancomycin and Tobramycin Local Antibiotic Powder on Surgical Site Infections After Open Treatment of Fracture: A Retrospective Propensity-Matched Analysis.

OBJECTIVES: The aim of this study was to compare the effect of vancomycin/tobramycin local antibiotic powder (LAP) on surgical site infections (SSIs) after open treatment of fractures. DESIGN: This was a retrospective comparative study with propensity matching. SETTING: The study was set in an urban level 1 trauma center. PATIENTS SELECTION CRITERIA: Patients undergoing open procedures for fracture performed by a single surgeon before and after cessation of routine LAP use were included. OUTCOME MEASURES AND COMPARISONS: Deep and superficial SSIs were the measured outcomes. RESULTS: There were 652 open procedures for fracture performed by a single surgeon: LAP was used in 36.7% (114/310) of procedures before stopping its use, after which 342 procedures were performed without LAP. Comparison of all procedures performed with and without routine LAP use demonstrated no difference in infection rates, although there was a trend for the group without LAP to have fewer superficial SSIs (proportional difference [PD] -2.0%, 95% confidence interval [CI] -4.1% to 0.1%; P = 0.05) and more deep SSIs (PD 3.9%, 95% CI, -0.2% to 7.9%; P = 0.06). Prematch analysis demonstrated that LAP use was associated with external fixation (PD 8.5%, 95% CI, 1.6%-16.2%; P = 0.005), longer operative times (median difference 56.0 minutes, 95% CI, 39.0-74.0; P < 0.0001), greater estimated blood loss (median difference 70.0, 95% CI, 50.0-100.0; P < 0.0001), and no difference in superficial (PD 2.4%; 95% CI, -0.8% to 6.8%; P = 0.07) or deep SSIs (PD -1.6%, 95% CI, -6.2% to 4.1%; P = 0.54). After propensity matching (108 vs. 108) to control for the above differences, the LAP group, compared with the no LAP group, had no difference in superficial SSIs and was less likely to have deep SSIs (PD -8.3%, 95% CI, -16.2% to -0.2%; P = 0.04). CONCLUSIONS: The use of vancomycin and tobramycin LAP lowered the rate of deep SSIs after open treatment of fractures on propensity-matched analysis. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Necessity of Tobramycin trough Levels in Once Daily Iv-Treatment in Patients with Cystic Fibrosis.

BACKGROUND: Once daily intravenous (iv) treatment with tobramycin for Pseudomonas aeruginosa infection in patients with cystic fibrosis (pwCF) is frequently monitored by measuring tobramycin trough levels (TLs). Although the necessity of these TLs is recently questioned in pwCF without renal impairment, no study has evaluated this so far. The aim of this observational study was to evaluate the frequency of increased tobramycin TLs in pwCF treated with a once daily tobramycin dosing protocol. METHODS: Patient records of all consecutive once daily iv tobramycin courses in 35 pwCF between 07/2009 and 07/2019 were analyzed for tobramycin level, renal function, co-medication and comorbidity. RESULTS: Eight elevated TLs (2.9% of 278 courses) were recorded in four patients, two with normal renal function. One of these resolved without adjustment of tobramycin dosages suggesting a test timing or laboratory error. In the other patient the elevated tobramycin level decreased after tobramycin dosage adjustment. Six of the elevated levels occurred in two patients with chronic renal failure. In 15 other patients with reduced glomerular filtration rate (GFR) (36 courses) but normal range creatinine no case of elevated tobramycin trough levels was detected. Neither cumulative tobramycin dosages nor concomitant diabetes or nutritional status were risk factors for elevated TLs. CONCLUSION: Our data show that elevated tobramycin TLs are rare but cannot be excluded, so determination of tobramycin TLs is still recommended for safety.

The role of hypermutation and collateral sensitivity in antimicrobial resistance diversity of Pseudomonas aeruginosa populations in cystic fibrosis lung infection.

Pseudomonas aeruginosa is an opportunistic pathogen which causes chronic, drug-resistant lung infections in cystic fibrosis (CF) patients. In this study, we explore the role of genomic diversification and evolutionary trade-offs in antimicrobial resistance (AMR) diversity within P. aeruginosa populations sourced from CF lung infections. We analyzed 300 clinical isolates from four CF patients (75 per patient) and found that genomic diversity is not a consistent indicator of phenotypic AMR diversity. Remarkably, some genetically less diverse populations showed AMR diversity comparable to those with significantly more genetic variation. We also observed that hypermutator strains frequently exhibited increased sensitivity to antimicrobials, contradicting expectations from their treatment histories. Investigating potential evolutionary trade-offs, we found no substantial evidence of collateral sensitivity among aminoglycoside, beta-lactam, or fluoroquinolone antibiotics, nor did we observe trade-offs between AMR and growth in conditions mimicking CF sputum. Our findings suggest that (i) genomic diversity is not a prerequisite for phenotypic AMR diversity, (ii) hypermutator populations may develop increased antimicrobial sensitivity under selection pressure, (iii) collateral sensitivity is not a prominent feature in CF strains, and (iv) resistance to a single antibiotic does not necessarily lead to significant fitness costs. These insights challenge prevailing assumptions about AMR evolution in chronic infections, emphasizing the complexity of bacterial adaptation during infection.IMPORTANCEUpon infection in the cystic fibrosis (CF) lung, Pseudomonas aeruginosa rapidly acquires genetic mutations, especially in genes involved in antimicrobial resistance (AMR), often resulting in diverse, treatment-resistant populations. However, the role of bacterial population diversity within the context of chronic infection is still poorly understood. In this study, we found that hypermutator strains of P. aeruginosa in the CF lung undergoing treatment with tobramycin evolved increased sensitivity to tobramycin relative to non-hypermutators within the same population. This finding suggests that antimicrobial treatment may only exert weak selection pressure on P. aeruginosa populations in the CF lung. We further found no evidence for collateral sensitivity in these clinical populations, suggesting that collateral sensitivity may not be a robust, naturally occurring phenomenon for this microbe.

Multifunctional Cationic Hyperbranched Polyaminoglycosides that Target Multiple Mediators for Severe Abdominal Trauma Management.

Trauma and its associated complications, including dysregulated inflammatory responses, severe infection, and disseminated intravascular coagulation (DIC), continue to pose lethal threats worldwide. Following injury, cell-free nucleic acids (cfNAs), categorized as damage-associated molecular patterns (DAMPs), are released from dying or dead cells, triggering local and systemic inflammatory responses and coagulation abnormalities that worsen disease progression. Harnessing cfNA scavenging strategies with biomaterials has emerged as a promising approach for treating posttrauma systemic inflammation. In this study, the effectiveness of cationic hyperbranched polyaminoglycosides derived from tobramycin (HPT) and disulfide-included HPT (ss-HPT) in scavenging cfNAs to mitigate posttrauma inflammation and hypercoagulation is investigated. Both cationic polymers demonstrate the ability to suppress DAMP-induced toll-like receptor (TLR) activation, inflammatory cytokine secretion, and hypercoagulation by efficiently scavenging cfNAs. Additionally, HPT and ss-HPT exhibit potent antibacterial efficacy attributed to the presence of tobramycin in their chemical composition. Furthermore, HPT and ss-HPT exhibit favorable modulatory effects on inflammation and therapeutic outcomes in a cecal ligation puncture (CLP) mouse abdominal trauma model. Notably, in vivo studies reveal that ss-HPT displayed high accumulation and retention in injured organs of traumatized mice while maintaining a higher biodegradation rate in healthy mice, contrasting with findings for HPT. Thus, functionalized ss-HPT, a bioreducible polyaminoglycoside, holds promise as an effective option to enhance therapeutic outcomes for trauma patients by alleviating posttrauma inflammation and coagulation complications.

Mutations in genes lpxL1, bamA, and pmrB impair the susceptibility of cystic fibrosis strains of Pseudomonas aeruginosa to murepavadin.

Murepavadin is a peptidomimetic exhibiting specific inhibitory activity against Pseudomonas species. In the present study, its in vitro activity was assessed on 230 cystic fibrosis (CF) strains of Pseudomonas aeruginosa isolated from 12 French hospitals, in comparison with 12 other antipseudomonal antibiotics. Although murepavadin is still in preclinical stage of development, 9.1% (n = 21) of strains had a minimum inhibitory concentration (MIC) >4 mg/L, a level at least 128-fold higher than the modal MIC value of the whole collection (≤0.06 mg/L). Whole-genome sequencing of these 21 strains along with more susceptible isogenic counterparts coexisting in the same patients revealed diverse mutations in genes involved in the synthesis (lpxL1 and lpxL2) or transport of lipopolysaccharides (bamA, lptD, and msbA), or encoding histidine kinases of two-component systems (pmrB and cbrA). Allelic replacement experiments with wild-type reference strain PAO1 confirmed that alteration of genes lpxL1, bamA, and/or pmrB can decrease the murepavadin susceptibility from 8- to 32-fold. Furthermore, we found that specific amino acid substitutions in histidine kinase PmrB (G188D, Q105P, and D45E) reduce the susceptibility of P. aeruginosa to murepavadin, colistin, and tobramycin, three antibiotics used or intended to be used (murepavadin) in aerosols to treat colonized CF patients. Whether colistin or tobramycin may select mutants resistant to murepavadin or the opposite needs to be addressed by clinical studies.

Amphiphilic tribasic galactosamines potentiate rifampicin in Gram-negative bacteria at low Mg++/Ca++concentrations.

Many antibiotics specific to Gram-positive bacteria like rifampicin (RIF) are inactive in Gram-negative bacteria because of outer membrane (OM) impermeability. Enhancing the OM permeability of these antibiotics with the help of OM perturbants is a promising strategy to develop new agents against Gram-negative bacteria. Here we report the synthesis and biological properties of amphiphilic tribasic galactosamines as potential RIF potentiators. Our results demonstrate that tribasic galactose-based amphiphiles potentiate RIF in multidrug-resistant Acinetobacter baumannii and Escherichia coli but not Pseudomonas aeruginosa in low salt-containing media. Under these conditions, lead compounds 20, 22 and 35 lowered the minimum inhibitory concentration of RIF by 64- to 256-fold against Gram-negative bacteria. However, the RIF-potentiating effect was reduced when bivalent Mg++ or Ca++ ions were added in the media at physiological concentrations. Overall, our results indicate that amphiphilic tribasic galactosamine-based compounds show reduced RIF-potentiating effects when compared to amphiphilic tobramycin antibiotics at physiological salt concentrations.

Thermostable Lactonases Inhibit Pseudomonas aeruginosa Biofilm: Effect In Vitro and in Drosophila melanogaster Model of Chronic Infection.

Pseudomonas aeruginosa is one of the six antimicrobial-resistant pathogens known as "ESKAPE" that represent a global threat to human health and are considered priority targets for the development of novel antimicrobials and alternative therapeutics. The virulence of P. aeruginosa is regulated by a four-chemicals communication system termed quorum sensing (QS), and one main class of QS signals is termed acylhomoserine lactones (acyl-HSLs), which includes 3-Oxo-dodecanoil homoserine lactone (3-Oxo-C12-HSL), which regulates the expression of genes implicated in virulence and biofilm formation. Lactonases, like Paraoxonase 2 (PON2) from humans and the phosphotriesterase-like lactonases (PLLs) from thermostable microorganisms, are able to hydrolyze acyl-HSLs. In this work, we explored in vitro and in an animal model the effect of some lactonases on the production of Pseudomonas virulence factors. This study presents a model of chronic infection in which bacteria were administered by feeding, and Drosophila adults were treated with enzymes and the antibiotic tobramycin, alone or in combination. In vitro, we observed significant effects of lactonases on biofilm formation as well as effects on bacterial motility and the expression of virulence factors. The treatment in vivo by feeding with the lactonase SacPox allowed us to significantly increase the biocidal effect of tobramycin in chronic infection.

The Inactivation of the Putative Two-Component System Sensor PA14_27940 Increases the Susceptibility to Several Antibiotics and Reduces the Motility of Pseudomonas aeruginosa.

The identification of targets whose inactivation increases the activity of antibiotics helps to fight antibiotic resistance. Previous work showed that a transposon-insertion mutant in the gene PA14_27940 increases Pseudomonas aeruginosa susceptibility to aminoglycosides. Since polar effects may affect the phenotype, in the present work, we generated an in-frame PA14_27940 deletion mutant. A PA14_27940 deletion increased the susceptibility to aminoglycosides, tetracycline, tigecycline, erythromycin and fosfomycin. Excepting fosfomycin, the other antibiotics are inducers of the MexXY efflux pump. MexXY induction is required for P. aeruginosa resistance to these antibiotics, which is post-transcriptionally regulated by the anti-repressor ArmZ. Although mexXY is inducible by tobramycin in ΔPA14_27940, the induction level is lower than in the parental PA14 strain. Additionally, armZ is induced by tobramycin in PA14 and not in ΔPA14_27940, supporting that ΔPA14_27940 presents an ArmZ-mediated defect in mexXY induction. For its part, hypersusceptibility to fosfomycin may be due to a reduced expression of nagZ and agmK, which encode enzymes of the peptidoglycan recycling pathway. ΔPA14_27940 also presents defects in motility, an element with relevance in P. aeruginosa's virulence. Overall, our results support that PA14_27940 is a good target for the search of adjuvants that will increase the activity of antibiotics and reduce the virulence of P. aeruginosa.