Aminoglycosides: nephrotoxicity

New Negamycin-Based Potent Readthrough Derivative Effective against TGA-Type Nonsense Mutations

We report a novel negamycin derivative TCP-1109 (13x) which serves as a potent readthrough drug candidate against nonsense-associated diseases. We previously demonstrated that TCP-112 (7), a nor-compound of native 3-epi-deoxynegmaycin, showed a higher readthrough activity than (+)-negamycin. In the present study, we performed a structure-activity relationship (SAR) study of compound 7 focused on its 3-amino group in an effort to develop a more potent readthrough compound. Introduction of a variety of natural or unnatural amino acids to the 3-amino group gave us the more potent derivative 13x which has about four times higher readthrough activity than 7 in a cell-based assay using a premature termination codon of TGA derived from Duchenne muscular dystrophy. The activity was dose-dependent and relatively selective for TGA. However, the activities for TAG and TAA were also higher than those of (+)-negamycin and 7. Moreover, compound 13x showed significant cell-based readthrough activity for several nonsense mutations derived from other nonsense-associated diseases. It is suggested that 13x has the potential to be a readthrough drug useful for the treatment of many kinds of nonsense-associated diseases.

Risk of Nephrotoxicity in Patients With Drug-Resistant Tuberculosis Treated With Kanamycin/Capreomycin With or Without Concomitant Use of Tenofovir-Containing Antiretroviral Therapy

BACKGROUND

The intersection of HIV and drug-resistant (DR) tuberculosis (TB) presents the challenge of managing convergent drug toxicities.

METHODS

We conducted a retrospective study of adult patients with DR-TB treated with a kanamycin/capreomycin-based (KM) regimen, with or without concomitant antiretroviral therapy (ART). We estimated the incidence of nephrotoxicity (defined as an increase in serum creatinine greater than 26.5 µmol, or an increase in serum creatinine to 1.5 times the baseline value, or a decline in glomerular filtration rate to less than 60 mL/min/1.73 m), and evaluated the association between reported drug use and nephrotoxicity using Kaplan-Meier plots.

RESULTS

A total of 215 patients with DR-TB were treated with a kanamycin/capreomycin-based regimen, with or without concomitant ART. The incidence rate of nephrotoxicity was 3.6 [95% confidence interval (CI): 1.4 to 7.3], 6.9 (95% CI: 5.2 to 9.0), and 12 (95% CI: 3.3 to 30.9) cases per 100 person-months of follow-up in the KM only group (n = 42), the KM + TDF (tenofovir disoproxil fumarate) group (n = 163), and the KM + Other ART group (n = 10), respectively. Using the KM only group as a reference, the hazard ratio was 2.06 (95% CI: 0.92 to 4.63) in the KM + TDF group, and 4.09 (95% CI: 1.17 to 14.25) in the KM + Other ART group. Advancing age was an independent predictor of nephrotoxicity (adjusted hazard ratio 1.29, 95% CI: 1.14 to 1.46).

CONCLUSIONS

Our findings provide evidence of a significant risk of nephrotoxicity during treatment with a kanamycin/capreomycin-based DR-TB regimen, with or without concurrent treatment with ART. This study lends further support to calls for the substitution of TDF during the intensive phase of DR-TB treatment and for close monitoring of renal function during DR-TB treatment, especially in settings where the use of kanamycin/capreomycin is unavoidable.

Gentamicin Affects the Bioenergetics of Isolated Mitochondria and Collapses the Mitochondrial Membrane Potential in Cochlear Sensory Hair Cells

Aminoglycoside antibiotics are widely prescribed to treat a variety of serious bacterial infections. They are extremely useful clinical tools, but have adverse side effects such as oto- and nephrotoxicity. Once inside a cell they are thought to cause mitochondrial dysfunction, subsequently leading to apoptotic cell death due to an increase in reactive oxygen species (ROS) production. Here we present evidence of a direct effect of gentamicin (the most commonly prescribed aminoglycoside) on the respiratory activities of isolated rat liver and kidney mitochondria. We show that gentamicin stimulates state 4 and inhibits state 3u respiratory rates, thereby reducing the respiratory control ratio (RCR) whilst simultaneously causing a collapse of the mitochondrial membrane potential (MtMP). We propose that gentamicin behaves as an uncoupler of the electron transport chain (ETC) - a hypothesis supported by our evidence that it reduces the production of mitochondrial ROS (MtROS). We also show that gentamicin collapses the MtMP in the sensory hair cells (HCs) of organotypic mouse cochlear cultures.

Hypoionic Shock Facilitates Aminoglycoside Killing of Both Nutrient Shift- and Starvation-Induced Bacterial Persister Cells by Rapidly Enhancing Aminoglycoside Uptake

Bacterial persister cells are phenotypic variants that exhibit transient antibiotic tolerance and play a leading role in chronic infections and the development of antibiotic resistance. Determining the mechanism that underlies persister formation and developing anti-persister strategies, therefore, are clinically important goals. Here, we report that many gram-negative and gram-positive bacteria become highly tolerant to typical bactericidal antibiotics when the carbon source for their antibiotic-sensitive exponential growth phase is shifted to fumarate, suggesting a role for fumarate in persister induction. Nutrient shift-induced Escherichia coli but not Staphylococcus aureus persister cells can be killed by aminoglycosides upon hypoionic shock (i.e., the absence of ions), which is achieved by suspending the persisters in aminoglycoside-containing pure water for only 1 or 2 min. Such potentiation can be abolished by inhibitors of the electron transport chain (e.g., NaN₃) or proton motive force (e.g., CCCP). Additionally, we show that hypoionic shock facilitates the eradication of starvation-induced E. coli but not S. aureus persisters by aminoglycosides, and that such potentiation can be significantly suppressed by NaN₃ or CCCP. Mechanistically, hypoionic shock dramatically enhances aminoglycoside uptake by both nutrient shift- and starvation-induced E. coli persisters, whereas CCCP can diminish this uptake. Results of our study illustrate the general role of fumarate in bacterial persistence and may open new avenues for persister eradication and aminoglycoside use.

The Supramolecular Self-Assembly of Aminoglycoside Antibiotics and their Applications

Aminoglycosides, a class of antibiotics that includes gentamicin, kanamycin, neomycin, streptomycin, tobramycin and apramycin, are derived from various streptomyces species. Despite the significant increase in the antibacterial resistant pathogens, aminoglycosides remain an important class of antimicrobial drugs due to their unique chemical structure which offers a broad spectrum of activity. The modification of antibiotics and their subsequent use in supramolecular chemistry is rarely reported. Given the importance of aminoglycosides, here we give a brief overview on the modification of 4,5- and 4,6-disubstituted deoxystreptamine classes of aminoglycosides through supramolecular chemistry and their potential for real world applications. We also make the case that the work in this area is gaining momentum, and there are significant opportunities to meet the challenges of modern antibiotics through the modification of aminoglycosides by harnessing the advantages of supramolecular chemistry.

Protection of Hair Cells from Ototoxic Drug-Induced Hearing Loss

Hair cells are specialized sensory epithelia cells that receive mechanical sound waves and convert them into neural signals for hearing, and these cells can be killed or damaged by ototoxic drugs, including many aminoglycoside antibiotics, platinum-based anticancer agents, and loop diuretics, leading to drug-induced hearing loss. Studies of therapeutic approaches to drug-induced hearing loss have been hampered by the limited understanding of the biological mechanisms that protect and regenerate hair cells. This review briefly discusses some of the most common ototoxic drugs and describes recent research concerning the mechanisms of ototoxic drug-induced hearing loss. It also highlights current developments in potential therapies and explores current clinical treatments for patients with hearing impairments.

Enforced lysosomal biogenesis rescues erythromycin- and clindamycin-induced mitochondria-mediated cell death in human cells

Antibiotics are the front-line treatment against many bacterial infectious diseases in human. The excessive and long-term use of antibiotics in human cause several side effects. It is important to understand the underlying molecular mechanisms of action of antibiotics in the host cell to avoid the side effects due to the prevalent uses. In the current study, we investigated the crosstalk between mitochondria and lysosomes in the presence of widely used antibiotics: erythromycin (ERM) and clindamycin (CLDM), which target the 50S subunit of bacterial ribosomes. We report here that both ERM and CLDM induced caspase activation and cell death in several different human cell lines. The activity of the mitochondrial respiratory chain was compromised in the presence of ERM and CLDM leading to bioenergetic crisis and generation of reactive oxygen species. Antibiotics treatment impaired autophagy flux and lysosome numbers, resulting in decreased removal of damaged mitochondria through mitophagy, hence accumulation of defective mitochondria. We further show that over-expression of transcription factor EB (TFEB) increased the lysosome number, restored mitochondrial function and rescued ERM- and CLDM-induced cell death. These studies indicate that antibiotics alter mitochondria and lysosome interactions leading to apoptotsis and may develop a novel approach for targeting inter-organelle crosstalk to limit deleterious antibiotic-induced side effects.

A Simulated Application of the Hartford Hospital Aminoglycoside Dosing Nomogram for Plazomicin Dosing Interval Selection in Patients With Serious Infections Caused by Carbapenem-Resistant Enterobacterales

PURPOSE

In the Phase III Study of Plazomicin Compared With Colistin in Patients With Infection Due to Carbapenem-Resistant Enterobacteriaceae (CARE), plazomicin was studied for the treatment of critically ill patients with infections caused by carbapenem-resistant Enterobacterales. Initial plazomicin dosing was guided by creatinine clearance (CrCl) and subsequent doses adjusted by therapeutic drug monitoring to achieve AUC_0-24 exposures within a target range (210-315 mg∙h/L). We applied the Hartford nomogram to evaluate whether this clinical tool could reduce plazomicin troughs levels and increase the proportion of patients within the target AUC range.

METHODS

Thirty-seven patients enrolled in cohorts 1 or 2 of CARE were eligible for analyses. Observed 10-hour concentrations after the initial dose were plotted on the Hartford nomogram to determine an eligible dosing interval group (q24h, q36h or q48h). On the basis of baseline CrCl, a 15- or 10-mg/kg dose was simulated with the nomogram-recommended dosing interval. The proportion of patients in each dosing interval group with a trough ≥3 mg/L (trough threshold associated with serum creatinine increases ≥0.5 mg/dL in product label) was quantified. Simulated interval-normalized AUC_0-24 was compared with the target AUC range.

FINDINGS

Among the 28 patients with a CrCl ≥60 mL/min, the nomogram recommended every-24-hour dosing in 61% and an extended-interval (q36h or q48h) in 39% of patients. For patients with a CrCl ≥30-59 mL/min (n = 9), the nomogram recommended every-24-hour dosing and an extended-interval in 22% and 78% of patients, respectively. Among both renal function cohorts, exposure simulation with the nomogram significantly reduced the proportion of patients with trough concentrations ≥3 mg/L (CrCl ≥60 mL/min cohort: 91% vs 9%, P < 0.001; CrCl ≥30-59 mL/min cohort, 100% vs 0%, P < 0.001). Relative to the observed mean (SD) AUC_0-24 of 309 mg∙h/mL (96 mg∙h/mL), simulation of extended intervals resulted in a mean interval-normalized AUC_0-24 of 210 mg∙h/mL (40 mg∙h/mL) in all patients eligible for an extended interval, resulting in a similar proportion (49% vs 54%) of patients within the target AUC_0-24 range after the first dose.

IMPLICATIONS

Application of the Hartford nomogram successfully reduced the likelihood of elevated plazomicin trough concentrations while improving AUC exposures in these patients with carbapenem-resistant Enterobacterales infections.

The "Old" and the "New" Antibiotics for MDR Gram-Negative Pathogens: For Whom, When, and How

The recent expansion of multidrug resistant and pan-drug-resistant pathogens poses significant challenges in the treatment of healthcare associated infections. An important advancement, is a handful of recently launched new antibiotics targeting some of the current most problematic Gram-negative pathogens, namely carbapenem-producing Enterobacteriaceae (CRE) and carbapenem-resistant P. aeruginosa (CRPA). Less options are available against carbapenem-resistant Acinetobacter baumannii (CRAB) and strains producing metallo-beta lactamases (MBL). Ceftazidime-avibactam signaled a turning point in the treatment of KPC and partly OXA- type carbapenemases, whereas meropenem-vaborbactam was added as a potent combination against KPC-producers. Ceftolozane-tazobactam could be seen as an ideal beta-lactam backbone for the treatment of CRPA. Plazomicin, an aminoglycoside with better pharmacokinetics and less toxicity compared to other class members, will cover important proportions of multi-drug resistant pathogens. Eravacycline holds promise in the treatment of infections by CRAB, with a broad spectrum of activity similar to tigecycline, and improved pharmacokinetics. Novel drugs and combinations are not to be considered "panacea" for the ongoing crisis in the therapy of XDR Gram-negative bacteria and colistin will continue to be considered as a fundamental companion drug for the treatment of carbapenem-resistant Enterobacteriaceae (particularly in areas where MBL predominate), for the treatment of CRPA (in many cases being the only in vitro active drug) as well as CRAB. Aminoglycosides are still important companion antibiotics. Finally, fosfomycin as part of combination treatment for CRE infections and P. aeruginosa, deserves a greater attention. Optimal conditions for monotherapy and the "when and how" of combination treatments integrating the novel agents will be discussed.

Utilizing the Patient Care Process to Minimize the Risk of Vancomycin-Associated Nephrotoxicity

Vancomycin-associated acute kidney injury (AKI) is a popular topic in the medical literature with few clear answers. While many studies evaluate the risk of AKI associated with vancomycin, few data are high quality and/or long in duration of follow-up. This review takes the clinician through an approach to evaluate a patient for risk of AKI. This evaluation should include patient assessment, antibiotic prescription, duration, and monitoring. Patient assessment involves evaluating severity of illness, baseline renal function, hypotension/vasopressor use, and concomitant nephrotoxins. Evaluation of antibiotic prescription includes evaluating the need for methicillin-resistant Staphylococcus aureus (MRSA) coverage and/or vancomycin use. Duration of therapy has been shown to increase the risk of AKI. Efforts to de-escalate vancomycin from the antimicrobial regimen, including MRSA nasal swabs and rapid diagnostics, should be used to lessen the likelihood of AKI. Adequate monitoring includes therapeutic drug monitoring, ongoing fluid status evaluations, and a continual reassessment of AKI risk. The issues with serum creatinine make the timely evaluation of renal function and diagnosis of the cause of AKI problematic. Most notably, concomitant piperacillin-tazobactam can increase serum creatinine via tubular secretion, resulting in higher rates of AKI being reported. The few studies evaluating the long-term prognosis of AKI in patients receiving vancomycin have found that few patients require renal replacement therapy and that the long-term risk of death is unaffected for patients surviving after the initial 28-day period.

Nephrotoxicity and ototoxic symptoms of injectable second-line anti-tubercular drugs among patients treated for MDR-TB in Ethiopia: a retrospective cohort study

Background

Nephrotoxicity and ototoxicity are clinically significant dose-related adverse effects associated with second-line anti-tubercular injectables drugs (aminoglycosides and capreomycin) used during intensive phase of treatment of multi-drug resistant tuberculosis (MDR-TB) patients. Data are scarce on injectable-induced nephrotoxicity and ototoxicity in Ethiopian MDR-TB patients. The aim of this study was to assess the prevalence, management of nephrotoxicity and ototoxic symptoms and treatment outcomes of patients treated for MDR-TB with injectable-based regimens.

Method

This was retrospective cohort study based on review of medical records of about 900 patients on MDR-TB treatment from January 2010 to December 2015 at two large TB referral hospitals in Addis Ababa, Ethiopia. Nephrotoxicity in study participants was screened using baseline and monthly measurement of serum creatinine and clinical diagnosis and patient reports.

Results

Overall, 473 (54.2%) of participants were male. Children accounted for 47 (5.5%) of cases and the mean age of participants was 32 ± 12.6 years with range of 2–75 years. The majority (n = 788, 84.6%) of participants had past history of TB. The most commonly used injectable anti-TB drug was capreomycin (n = 789, 84.7%), while kanamycin and amikacin were also used. There was a statistically significant increment (p<0.05) in the mean serum creatinine values from baseline throughout intensive phase of treatment with a 10–18% prevalence of nephrotoxicity. Based on clinical criteria, nephrotoxicity was detected in 62 (6.7%) and ototoxic symptoms were detected in 42 (4.8%) participants. Nephrotoxicity and ototoxic symptoms were clinically managed by modification of treatment regimens including dose and frequency of drug administration.

Conclusion

Nephrotoxicity and ototoxic symptoms were significant problems among patients on follow-up for MDR-TB treatment. Based on laboratory criteria (serum creatinine), nephrotoxicity remained significant adverse events throughout intensive phase of treatment, indicating close monitoring of patients for successful outcome is mandatory until countries adopt the recent injectable-free WHO guideline and under specific conditions.

Hemogram and iron indices in renal anemia and the amelioration with Carica papaya leaf extract applied on albino rat model

The present study was designed to look at the hematological disorders in gentamicin nephrotoxicity model, as kidney is considered as one of the hemopoietic organs. In a previous study, novel and classical kidney injury biomarkers were utilized to evaluate the nephroprotective potential of Carica papaya leaf extract (CPLE) in the same model in albino rats. Gentamicin (100 mg/kg, subcutaneously, for 21 consecutive days) resulted in significant decreases in red blood cell (RBC) count, hemoglobin concentration (HGB), and packed cell volume (PCV) value, with minimal alterations in erythrocytic indices. Leucogram showed leukocytosis, granulocytosis, and thrombocytopenia. Erythropoietin (EPO) levels were also drastically decreased by the end of the experimental course. Serum iron, unsaturated iron-binding capacity (UIBC), total iron binding capacity (TIBC), transferrin saturation %, and serum transferrin concentration values were significantly decreased in contrast to ferritin, which was increased. When concurrently administered with gentamicin, CPLE (150 and 300 mg/kg, orally via gastric tube, for 21 days) significantly protected against the drastic effects of the former on the blood profile with improving potentials on erythrogram, leukogram, thrombocytes, EPO, iron and its indices, in a dose-dependent manner. These data may suggest CPLE as an appreciated blood homeostatic and nephroprotective agent from a natural source that could be a good remedy in conditions associated with blood disorders.

Alarmone Ap4A is elevated by aminoglycoside antibiotics and enhances their bactericidal activity

This paper demonstrates that aminoglycoside antibiotics induce the production of the Ap4A in bacteria. Increased intracellular Ap4A, in turn, promotes bacterial cell killing by this class of antibiotics, which correlated well with elevated damage to the bacterial membrane upon aminoglycoside treatment. These findings reveal a striking connection between aminoglycoside killing and the Ap4A production particularly under conditions of oxidative stress. Importantly, the results of this study suggest that targeting Ap4A degradation or inducing its hypersynthesis during therapy with aminoglycosides might help solve the well-known toxicity issue associated with this class of antibiotics by reducing the level of drug needed for effective treatment.

Second messenger molecules play important roles in the responses to various stimuli that can determine a cell's fate under stress conditions. Here, we report that lethal concentrations of aminoglycoside antibiotics result in the production of a dinucleotide alarmone metabolite–diadenosine tetraphosphate (Ap4A), which promotes bacterial cell killing by this class of antibiotics. We show that the treatment of Escherichia coli with lethal concentrations of kanamycin (Kan) dramatically increases the production of Ap4A. This elevation of Ap4A is dependent on the production of a hydroxyl radical and involves the induction of the Ap4A synthetase lysyl-tRNA synthetase (LysU). Ectopic alteration of intracellular Ap4A concentration via the elimination of the Ap4A phosphatase diadenosine tetraphosphatase (ApaH) and the overexpression of LysU causes over a 5,000-fold increase in bacterial killing by aminoglycosides. This increased susceptibility to aminoglycosides correlates with bacterial membrane disruption. Our findings provide a role for the alarmone Ap4A and suggest that blocking Ap4A degradation or increasing its synthesis might constitute an approach to enhance aminoglycoside killing potency by broadening their therapeutic index and thereby allowing lower nontoxic dosages of these antibiotics to be used in the treatment of multidrug-resistant infections.

Optimizing Gentamicin Dosing in Pediatrics Using Monte Carlo Simulations

Gentamicin is known to have concentration-dependent bactericidal activity, and its nephrotoxic effect is well described. We developed a population pharmacokinetic/pharmacodynamic model to optimize gentamicin dosing in pediatrics. Data were retrospectively collected for pediatric patients 1 month to 12 years of age, admitted to general pediatric wards or intensive care units and received gentamicin for suspected or proven Gram-negative infections at King Saud University Medical City, Riyadh, Saudi Arabia. A total of 306 gentamicin peak and trough concentrations sets from 107 patients were analyzed with mean (±standard deviation) patient age and weight of 4.5 ± 3.5 years and 16.7 ± 10.8 kg, respectively. Gentamicin pharmacokinetics were adequately described with a one compartment system (R = 0.82, bias = 1.75% and precision = 88% for population predictions and R = 0.94, bias = 5% and precision = 29% for individual predictions). The gentamicin pharmacokinetic parameters were as follows: volume of distribution = 8.9 L, total body clearance = 2.8 L/h for a 20-kg patient. Monte Carlo simulations showed that doses of 5-6 mg/kg/dose once daily are adequate only to treat infections with Gram-negative organisms having minimal inhibitory concentration less than 1 µg/mL. While, at minimal inhibitory concentration of 1 µg/mL, higher doses (7-8 mg/kg/dose once daily) are needed to maximize the efficacy of gentamicin. However, at minimal inhibitory concentration of 2 µg/mL, even a 10 mg/kg dose showed poor target attainment (52%). The finding of this study highlights the need to reevaluate the current breakpoints of gentamicin and also to assess the safety of higher doses of gentamicin in pediatrics.

Aminoglycoside Revival: Review of a Historically Important Class of Antimicrobials Undergoing Rejuvenation

Aminoglycosides are cidal inhibitors of bacterial protein synthesis that have been utilized for the treatment of serious bacterial infections for almost 80 years. There have been approximately 15 members of this class approved worldwide for the treatment of a variety of infections, many serious and life threatening. While aminoglycoside use declined due to the introduction of other antibiotic classes such as cephalosporins, fluoroquinolones, and carbapenems, there has been a resurgence of interest in the class as multidrug-resistant pathogens have spread globally. Furthermore, aminoglycosides are recommended as part of combination therapy for empiric treatment of certain difficult-to-treat infections. The development of semisynthetic aminoglycosides designed to overcome common aminoglycoside resistance mechanisms, and the shift to once-daily dosing, has spurred renewed interest in the class. Plazomicin is the first new aminoglycoside to be approved by the FDA in nearly 40 years, marking the successful start of a new campaign to rejuvenate the class.

Combinational effect of curcumin and metformin against gentamicin-induced nephrotoxicity: Involvement of antioxidative, anti-inflammatory and antiapoptotic pathway

Gentamicin (GM) is an antibiotic related to aminoglycoside group that is used in treating Gram-negative bacterial infections. However, treatment with gentamicin is considered to be limited as it induces an oxidative stress-mediated apoptosis in kidney which causes a nephrotoxicity. Metformin is a well-known biguanide that is used for treating diabetes mellitus, especially type 2. Supplement with plant metabolites or natural antioxidants produce a protective activity against many types of diseases in vivo. Curcumin is a main medicinal constituent of Curcuma longa, has reported for number of biological effects, such as antioxidant, anti-inflammatory, and antitumor. The study aims at evaluating the metformin and curcumin alone or in combination on nephrotoxicity induced by GM. The outcome of the study shows that both metformin and curcumin, when used unaided, were effectively decreasing GM-induced nephrotoxicity. The two drugs combination was showed synergistic effect in ameliorating a GM-induced kidney injury, as supported by expressively improved renal dysfunction. Metformin and curcumin showed strong protection against oxidative stress in GM treated animals through decreasing the activities and expression of various antioxidative enzymes. Moreover, combination of two drugs showed an anti-inflammatory response through reducing a level of pro-inflammatory cytokines including tumor necrosis factor-alpha, interleukin 1-beta, and interleukin 6 in GM intoxicated group of animals. Furthermore, GM agitated apoptosis was affectedly diminished by the combinational treatment of metformin and curcumin via down-regulating activity of cleaved Caspase-3 and pro-apoptotic factor Bax, whereas increasing anti-apoptotic factor Bcl-2 signaling pathways. The above results suggested that combinational treatment of metformin and curcumin might be have a synergizing effect and substantial potential against nephrotoxicity induced by GM. PRACTICAL APPLICATIONS: Curcumin and metformin combination exhibited substantial synergistic effect against GM-induced nephrotoxicity through reducing oxidative stress, inflammation, as well as apoptosis in kidney cells. Therefore, the method of combination of curcumin and metformin might be functional to treat or inhibit GM prompted nephrotoxicity in future.

Global Analysis of Genes Essential for Francisella tularensis Schu S4 Growth In Vitro and for Fitness during Competitive Infection of Fischer 344 Rats

The highly virulent intracellular pathogen Francisella tularensis is a Gram-negative bacterium that has a wide host range, including humans, and is the causative agent of tularemia. To identify new therapeutic drug targets and vaccine candidates and investigate the genetic basis of Francisella virulence in the Fischer 344 rat, we have constructed an F. tularensis Schu S4 transposon library. This library consists of more than 300,000 unique transposon mutants and represents a transposon insertion for every 6 bp of the genome. A transposon-directed insertion site sequencing (TraDIS) approach was used to identify 453 genes essential for growth in vitro Many of these essential genes were mapped to key metabolic pathways, including glycolysis/gluconeogenesis, peptidoglycan synthesis, fatty acid biosynthesis, and the tricarboxylic acid (TCA) cycle. Additionally, 163 genes were identified as required for fitness during colonization of the Fischer 344 rat spleen. This in vivo selection screen was validated through the generation of marked deletion mutants that were individually assessed within a competitive index study against the wild-type F. tularensis Schu S4 strain.IMPORTANCE The intracellular bacterial pathogen Francisella tularensis causes a disease in humans characterized by the rapid onset of nonspecific symptoms such as swollen lymph glands, fever, and headaches. F. tularensis is one of the most infectious bacteria known and following pulmonary exposure can have a mortality rate exceeding 50% if left untreated. The low infectious dose of this organism and concerns surrounding its potential as a biological weapon have heightened the need for effective and safe therapies. To expand the repertoire of targets for therapeutic development, we initiated a genome-wide analysis. This study has identified genes that are important for F. tularensis under in vitro and in vivo conditions, providing candidates that can be evaluated for vaccine or antibacterial development.

Once-Daily Plazomicin for Complicated Urinary Tract Infections

BACKGROUND

The increasing multidrug resistance among gram-negative uropathogens necessitates new treatments for serious infections. Plazomicin is an aminoglycoside with bactericidal activity against multidrug-resistant (including carbapenem-resistant) Enterobacteriaceae.

METHODS

We randomly assigned 609 patients with complicated urinary tract infections (UTIs), including acute pyelonephritis, in a 1:1 ratio to receive intravenous plazomicin (15 mg per kilogram of body weight once daily) or meropenem (1 g every 8 hours), with optional oral step-down therapy after at least 4 days of intravenous therapy, for a total of 7 to 10 days of therapy. The primary objective was to show the noninferiority of plazomicin to meropenem in the treatment of complicated UTIs, including acute pyelonephritis, with a noninferiority margin of 15 percentage points. The primary end points were composite cure (clinical cure and microbiologic eradication) at day 5 and at the test-of-cure visit (15 to 19 days after initiation of therapy) in the microbiologic modified intention-to-treat population.

RESULTS

Plazomicin was noninferior to meropenem with respect to the primary efficacy end points. At day 5, composite cure was observed in 88.0% of the patients (168 of 191 patients) in the plazomicin group and in 91.4% (180 of 197 patients) in the meropenem group (difference, -3.4 percentage points; 95% confidence interval [CI], -10.0 to 3.1). At the test-of-cure visit, composite cure was observed in 81.7% (156 of 191 patients) and 70.1% (138 of 197 patients), respectively (difference, 11.6 percentage points; 95% CI, 2.7 to 20.3). At the test-of-cure visit, a higher percentage of patients in the plazomicin group than in the meropenem group were found to have microbiologic eradication, including eradication of Enterobacteriaceae that were not susceptible to aminoglycosides (78.8% vs. 68.6%) and Enterobacteriaceae that produce extended-spectrum β-lactamases (82.4% vs. 75.0%). At late follow-up (24 to 32 days after initiation of therapy), fewer patients in the plazomicin group than in the meropenem group had microbiologic recurrence (3.7% vs. 8.1%) or clinical relapse (1.6% vs. 7.1%). Increases in serum creatinine levels of 0.5 mg or more per deciliter (≥40 μmol per liter) above baseline occurred in 7.0% of patients in the plazomicin group and in 4.0% in the meropenem group.

CONCLUSIONS

Once-daily plazomicin was noninferior to meropenem for the treatment of complicated UTIs and acute pyelonephritis caused by Enterobacteriaceae, including multidrug-resistant strains. (Funded by Achaogen and the Biomedical Advanced Research and Development Authority; EPIC ClinicalTrials.gov number, NCT02486627.).

Methicillin-Resistant Staphylococcus aureus Prosthetic Valve Endocarditis: Pathophysiology, Epidemiology, Clinical Presentation, Diagnosis, and Management

Staphylococcus aureus prosthetic valve endocarditis (PVE) remains among the most morbid bacterial infections, with mortality estimates ranging from 40% to 80%. The proportion of PVE cases due to methicillin-resistant Staphylococcus aureus (MRSA) has grown in recent decades, to account for more than 15% of cases of S. aureus PVE and 6% of all cases of PVE. Because no large studies or clinical trials for PVE have been published, most guidelines on the diagnosis and management of MRSA PVE rely upon expert opinion and data from animal models or related conditions (e.g., coagulase-negative Staphylococcus infection). We performed a review of the literature on MRSA PVE to summarize data on pathogenic mechanisms and updates in epidemiology and therapeutic management and to inform diagnostic strategies and priority areas where additional clinical and laboratory data will be particularly useful to guide therapy. Major updates discussed in this review include novel diagnostics, indications for surgical management, the utility of aminoglycosides in medical therapy, and a review of newer antistaphylococcal agents used for the management of MRSA PVE.

The renoprotective effect of concomitant fosfomycin in the treatment of pulmonary exacerbations in cystic fibrosis

Background

Fosfomycin, effective in Cystic Fibrosis (CF), competes with aminoglycosides at renal binding sites and may therefore afford a renoprotective effect when used in combination therapy. We explored this by using markers of acute renal tubular damage [N-acetyl-β-d-glucose-aminidase (NAG), alanine amino-peptidase (AAP) and β₂-microglobulin].

Methods

Using a prospective randomized crossover trial design, at an acute pulmonary exacerbation, 18 adult CF patients received either 14 days of intravenous (IV) tobramycin or IV tobramycin and IV fosfomycin, both in combination with a second IV antibiotic (colomycin).

Results

Urinary NAG (P = 0.003) and AAP (P = 0.03) following treatment with concomitant fosfomycin were lower than those after treatment with tobramycin and colomycin alone. Fosfomycin attenuated the total 24-h urinary protein leak (P = 0.0001). The 14-day improvements in all surrogate markers of exacerbation resolution (FEV₁% predicted, FVC, white cell count and C-reactive protein) were similar for both treatment regimens.

Conclusion

The addition of fosfomycin reduces acute renal injury caused by IV aminoglycoside therapy in CF pulmonary exacerbations.

Different influences on mitochondrial function, oxidative stress and cytotoxicity of antibiotics on primary human neuron and cell lines

Although antibiotics are generally well tolerated, their toxic effects on the central nervous system have been gained attention. In this study, we systematically investigated the neuron toxicity of antibiotics from six different classes. We show that clinically relevant concentrations of metronidazole, tigecycline, azithromycin and clindamycin but not ampicillin or sulfamethoxazole induce apoptosis of human primary neuron cells and lines. Notably, tigecycline, azithromycin and clindamycin cause neuron cell oxidative damage whereas metronidazole has no effect on reactive oxygen species (ROS) production, suggesting that metronidazole induces neuron death via ROS-independent mechanism. Tigecycline, azithromycin and clindamycin induce mitochondrial dysfunctions via targeting different mitochondrial respiratory complexes, leading to mitochondrial membrane potential disruption and energy crisis. The deleterious effects of antibiotics are reversed by pretreatment of neuron cells with antioxidant. Our work highlights the different influences of antibiotics on mitochondrial dysfunction, oxidative damage and cytotoxicity in neuron cells. We also provide a strategy to prevent the neurotoxicity.

Sex Difference in Gentamicin-induced Nephrotoxicity: Influence of L-arginine in Rat Model

Background:

L-arginine is an important precursor for the formation of nitric oxide (NO). According to previous studies, NO function is related to gender. Likewise, chronic renal diseases have lower prevalence in female. Gentamicin (GM) is an aminoglycoside antibiotic. According to some studies, males are more sensitive to GM renal nephrotoxicity. This study attempts to find protective effects of L-arginine on GM nephrotoxicity in male and female rats.

Methods:

Male and female rats were divided into eight groups: Rats were randomly assigned to 8 groups each including both male and female rats. The first and second groups received vehicle (saline), the third and fourth groups received gentamicin (80 mg/kg), the fifth and sixth groups received L-arginine (150 mg/kg), and finally, seventh and eighth groups received gentamicin+ L- arginine. Next, 9 days after administering drugs, blood samples were collected from the heart. After making sacrifices, the level of blood urea, creatinine (Cr), nitrite, and malondialdehyde (MDA) was measured in serums. Likewise, nitrite and MDA were measured in the homogenized kidney tissue.

Results:

GM significantly increased serum level of urea and Cr in male and female rats (P < 0.05). However, co-administration of GM + L-arginine significantly did not decrease urea and Cr level in male rats, whereas, in female rats, they significantly reduced (P < 0.05). In response to GM, renal MDA level increased in male and female rats (P < 0.05), and in the presence of GM + L-arginine, the level of MDA significantly decreased in both genders (P < 0.05).

Conclusions:

L-arginine demonstrated some protective effects in female rats but did not protect against GM nephrotoxicity in male rats for unknown reasons, probably related to the effects of sex hormones which needs further studies to be confirmed.

Encoding of Promiscuity in an Aminoglycoside Acetyltransferase

Aminoglycoside antibiotics are a large family of antibiotics that can be divided into two distinct classes on the basis of the substitution pattern of the central deoxystreptamine ring. Although aminoglycosides are chemically, structurally, and topologically diverse, some aminoglycoside-modifying enzymes (AGMEs) are able to inactivate as many as 15 aminoglycosides from the two main classes, the kanamycin- and neomycin-based antibiotics. Here, we present the crystal structure of a promiscuous AGME, aminoglycoside- N3-acetyltransferase-IIIb (AAC-IIIb), in the apo form, in binary drug (sisomicin, neomycin, and paromomycin) and coenzyme A (CoASH) complexes, and in the ternary neomycin-CoASH complex. These data provide a structural framework for interpretation of the thermodynamics of enzyme-ligand interactions and the role of solvent in the recognition of ligands. In combination with the recent structure of an AGME that does not have broad substrate specificity, these structures allow for the direct determination of how antibiotic promiscuity is encoded in some AGMEs.

A critical review of adverse effects to the kidney: mechanisms, data sources, and in silico tools to assist prediction

INTRODUCTION

The kidney is a major target for toxicity elicited by pharmaceuticals and environmental pollutants. Standard testing which often does not investigate underlying mechanisms has proven not to be an adequate hazard assessment approach. As such, there is an opportunity for the application of computational approaches that utilize multiscale data based on the Adverse Outcome Pathway (AOP) paradigm, coupled with an understanding of the chemistry underpinning the molecular initiating event (MIE) to provide a deep understanding of how structural fragments of molecules relate to specific mechanisms of nephrotoxicity. Aims covered: The aim of this investigation was to review the current scientific landscape related to computational methods, including mechanistic data, AOPs, publicly available knowledge bases and current in silico models, for the assessment of pharmaceuticals and other chemicals with regard to their potential to elicit nephrotoxicity. A list of over 250 nephrotoxicants enriched with, where possible, mechanistic and AOP-derived understanding was compiled. Expert opinion: Whilst little mechanistic evidence has been translated into AOPs, this review identified a number of data sources of in vitro, in vivo, and human data that may assist in the development of in silico models which in turn may shed light on the interrelationships between nephrotoxicity mechanisms.

Novel and classical renal biomarkers as evidence for the nephroprotective effect of Carica papaya leaf extract

The present study is aimed at utilization of novel and classical kidney function biomarkers to evaluate the nephroprotective potential of Carica papaya leaf extract (CPLE) in gentamicin nephrotoxicity model in albino rats. The used classical biomarkers were urea and creatinine; while the new biomarkers were Kidney injury molecule-1 (KIM-1) and Clusterin. Forty-five male albino rats were assigned into five groups and subjected to different treatments for nine consecutive days (vehicles; gentamicin, 100 mg/kg, subcutaneously; ascorbic acid, 200 mg/kg, orally; CPLE, 150 and 300 mg/kg b wt., orally). Three rats/group were killed on days 3, 6, and 9 for blood and tissue samples for renal and oxidation markers. Gentamicin resulted in significant increase in urea and creatinine only by the end of the experimental course; while the novel biomarkers were evident as early as 3 days upon gentamicin injection. When concurrently administered with gentamicin, CPLE significantly protected kidney tissues against gentamicin nephrotoxic effects indicated by decrement of both the novel and the classical standard biomarkers, in a dose-dependent manner. CPLE-mediated protection was attributed to its antioxidant potential indicated by significant inhibition of malondialdehyde (MDA) levels in both serum and kidney homogenates. The results were further supported by histopathological examination that revealed considerable amelioration of the pathological microscopic alterations induced by repeated gentamicin injection. Phytochemical analysis of CPLE indicated presence of tannins and flavonoids. These data may suggest CPLE, based on improvement of both classical and novel renal markers, as a highly potent nephroprotective and antioxidant from natural source that could be a good remedy in conditions associated with renal disorders.

The Prevention and Management of Contrast-induced Acute Kidney Injury: A Mini-review of the Literature

Contrast-induced acute kidney injury, also called contrast-induced nephropathy, is one of the main causes of acute renal failure/acute kidney injury (AKI) in hospitalized patients within 48 to 72 hours of contrast media administration during various radiologic procedures. Several factors can be responsible for contrast-induced acute tubular necrosis (ATN); however, patient and procedure-related factors play the lead role in determining the development of contrast-induced nephropathy. There is no definitive treatment and hydration remains the mainstay preventive strategy. This article will review the incidence, criteria for definitive diagnosis, and an effective approach on how to prevent contrast-induced nephropathy in a clinical setup.

In Vivo Efficacy of Meropenem with a Novel Non-β-Lactam-β-Lactamase Inhibitor, Nacubactam, against Gram-Negative Organisms Exhibiting Various Resistance Mechanisms in a Murine Complicated Urinary Tract Infection Model

Urinary tract infections (UTIs) are a tremendous burden on the health care system due to the vast number of infections resulting in antibiotic therapy and/or hospitalization. Additionally, these infections are frequently caused by multidrug-resistant (MDR) organisms, limiting the availability of effective antimicrobials. Nacubactam is a novel non-β-lactam-β-lactamase inhibitor with in vitro activity against class A and class C β-lactamases. Nacubactam is being developed in combination with meropenem, providing broad-spectrum activity in addition to improved stability against common β-lactamases. Here, we utilized a neutropenic murine complicated UTI (cUTI) model to determine the potential clinical utility of meropenem-nacubactam compared with meropenem or nacubactam alone against 10 Klebsiella pneumoniae, Escherichia coli, and Enterobacter cloacae isolates with diverse genotypic and phenotypic profiles, including NDM, KPC, OXA, CTX-M, SHV, and TEM enzyme-producing isolates. Selected isolates had meropenem-nacubactam MICs between 1 and 8 μg/ml. Meropenem-nacubactam demonstrated the greatest in vivo efficacy against 9 of 10 isolates, achieving a ≥3 log reduction from the 48-h control in all isolates tested, including isolates prepared as high inoculums. Nacubactam alone confirmed antibacterial properties, achieving a >1 log reduction against the majority of isolates. The combination of meropenem-nacubactam further enhanced the activity of either agent alone, notably against meropenem-resistant isolates. Against ceftazidime-avibactam-resistant isolates, meropenem-nacubactam demonstrated increased antibacterial kill upwards of 6 log₁₀ CFU in comparison to the 48-h control. Our data support the potential clinical utility of meropenem-nacubactam for cUTI in humans against MDR Enterobacteriaceae, although further clinical data supporting meropenem-nacubactam efficacy are needed.

Intact Cell Lipidomics Reveal Changes to the Ratio of Cardiolipins to Phosphatidylinositols in Response to Kanamycin in HeLa and Primary Cells

Antimicrobial resistance is a major threat the world is currently facing. Development of new antibiotics and the assessment of their toxicity represent important challenges. Current methods for addressing antibiotic toxicity rely on measuring mitochondrial damage using ATP and/or membrane potential as a readout. In this study, we propose an alternative readout looking at changes in the lipidome on intact and unprocessed cells by matrix-assisted laser desorption ionization mass spectrometry. As a proof of principle, we evaluated the impact of known antibiotics (levofloxacin, ethambutol, and kanamycin) on the lipidome of HeLa cells and mouse bone marrow-derived macrophages. Our methodology revealed that clinically relevant concentrations of kanamycin alter the ratio of cardiolipins to phosphatidylinositols. Unexpectedly, only kanamycin had this effect even though all antibiotics used in this study led to a decrease in the maximal mitochondrial respiratory capacity. Altogether, we report that intact cell-targeted lipidomics can be used as a qualitative method to rapidly assess the toxicity of aminoglycosides in HeLa and primary cells. Moreover, these results demonstrate there is no direct correlation between the ratio of cardiolipins to phosphatidylinositols and the maximal mitochondrial respiratory capacity.

Human Milk Oligosaccharides (HMOs) Sensitize Group B Streptococcus to Clindamycin, Erythromycin, Gentamicin, and Minocycline on a Strain Specific Basis

Human milk oligosaccharides (HMOs) possess antimicrobial and antibiofilm activity against Group B Streptococcus (GBS). HMOs were screened for their ability to potentiate antibiotic activity. We observed that HMOs potentiate the function of aminoglycosides, lincosamides, macrolides, and tetracyclines on a strain specific basis but not β-lactams or glycopeptides that inhibit cell wall synthesis. These findings are notable as GBS has evolved high levels of resistance toward aminoglycosides, macrolides, and tetracyclines. Finally, HMOs potentiate the function of aminoglycosides against both Staphylococcus aureus and Acinetobacter baumannii. On the basis of these observations, we hypothesized that HMOs act by increasing membrane permeability. This hypothesis was evaluated using a bacterial membrane permeability assay which revealed that HMOs increase membrane permeability toward propidium iodide.

Combining Extracellular miRNA Determination with Microfluidic 3D Cell Cultures for the Assessment of Nephrotoxicity: a Proof of Concept Study

Drug-induced kidney injury is often observed in the clinics and can lead to long-term organ failure. In this work, we evaluated a novel in vitro system that aims at detecting whether compounds can cause renal proximal tubule damage in man. For this, we implemented organotypic cultures of human conditionally immortalized proximal tubule epithelial cells overexpressing the organic anion transporter 1 (ciPTEC-OAT1) in a three-channel OrganoPlate under microfluidic conditions. Cells were exposed to four known nephrotoxicants (cisplatin, tenofovir, cyclosporine A, and tobramycin). The effect on cell viability and NAG release into the medium was determined. A novel panel of four miRNAs (mir-21, mir-29a, mir-34a, and mir-192) was selected as potential biomarkers of proximal tubule damage. After nephrotoxicant treatment, miRNA levels in culture medium were earlier indicators than cell viability (WST-8 assay) and outperformed NAG for proximal tubule damage. In particular, mir-29a, mir-34a, and mir-192 were highly reproducible between experiments and across compounds, whereas mir-21 showed more variability. Moreover, similar data were obtained in two different laboratories, underlining the reproducibility and technical transferability of the results, a key requirement for the implementation of novel biomarkers. In conclusion, the selected miRNAs behaved like sensitive biomarkers of damage to tubular epithelial cells caused by several nephrotoxicity mechanisms. This biomarker panel, in combination with the 3D cultures of ciPTEC-OAT1 in the OrganoPlate, represents a novel tool for in vitro nephrotoxicity detection. These results pave the way for the application of miRNAs in longitudinal, time-course in vitro toxicity studies.

Inhibition of Connexin Hemichannels by New Amphiphilic Aminoglycosides without Antibiotic Activity

Connexins hemichannels (HCs) from adjacent cells form gap junctional channels that mediate cell-to-cell communication. Abnormal opening of "free" undocked HCs can produce cell damage and participate in the mechanism of disorders such as cardiac infarct, stroke, deafness, skin diseases, and cataracts. Therefore, inhibitors of connexin HCs have great pharmacological potential. Antibiotic aminoglycosides (AGs) have been recently identified as connexin HC inhibitors, but their antibiotic effect is an issue for the treatment of disorders where infections do not play a role. Herein, we synthesized and tested several amphiphilic AGs without antibiotic effect for their inhibition against connexin HCs, using a newly developed cell-based bacterial growth complementation assay. Several leads with superior potency than the parent compound, kanamycin A, were identified. Unlike traditional AGs, these amphiphilic AGs are not bactericidal and are not toxic to mammalian cells, making them better than traditional AGs as HC inhibitors for clinical use and other applications.

Optimisation of antimicrobial dosing based on pharmacokinetic and pharmacodynamic principles

While suboptimal dosing of antimicrobials has been attributed to poorer clinical outcomes, clinical cure and mortality advantages have been demonstrated when target pharmacokinetic (PK) and pharmacodynamic (PD) indices for various classes of antimicrobials were achieved to maximise antibiotic activity. Dosing optimisation requires a good knowledge of PK/PD principles. This review serves to provide a foundation in PK/PD principles for the commonly prescribed antibiotics (β-lactams, vancomycin, fluoroquinolones and aminoglycosides), as well as dosing considerations in special populations (critically ill and obese patients). PK principles determine whether an appropriate dose of antimicrobial reaches the intended pathogen(s). It involves the fundamental processes of absorption, distribution, metabolism and elimination, and is affected by the antimicrobial's physicochemical properties. Antimicrobial pharmacodynamics define the relationship between the drug concentration and its observed effect on the pathogen. The major indicator of the effect of the antibiotics is the minimum inhibitory concentration. The quantitative relationship between a PK and microbiological parameter is known as a PK/PD index, which describes the relationship between dose administered and the rate and extent of bacterial killing. Improvements in clinical outcomes have been observed when antimicrobial agents are dosed optimally to achieve their respective PK/PD targets. With the rising rates of antimicrobial resistance and a limited drug development pipeline, PK/PD concepts can foster more rational and individualised dosing regimens, improving outcomes while simultaneously limiting the toxicity of antimicrobials.

Antibiotic drug piperacillin induces neuron cell death through mitochondrial dysfunction and oxidative damage

Although nerve damage/toxicity has been shown to be one of the side effects in patients given prolonged antibiotic treatment, the mechanisms of the action of antibiotics on neuron cells are not clear. In this work, we investigated the toxicity of piperacillin (an antibiotic that can penetrate the blood–brain barrier) on neuron cells and its underlying mechanisms. We show that clinically relevant doses of piperacillin induce apoptosis in SH-SY5Y and human primary neuron cells through activating caspase-3 activity and decreasing Mcl-1 and Bcl-2 levels. In addition, piperacillin causes mitochondrial dysfunction in neuron cells as shown by the reduction of mitochondrial respiration, membrane potential, and ATP production. We further demonstrate that piperacillin increases accumulation of mitochondrial superoxide and reactive oxygen species, suggesting the oxidative stress in neuron cells. Consistently, oxidative damage to DNA, proteins, and membrane lipids are observed in neuron cells exposed to piperacillin. The deleterious effects of piperacillin are abolished in neuron cells by antioxidant N-acetyl-l-cysteine, further confirming that piperacillin causes neuron cell death through inducing mitochondrial dysfunction and oxidative damage. Our work demonstrates the role of piperacillin in inducing oxidative damage in neuron cells and also provides a therapeutic strategy to prevent the side effects of antibiotic treatment.

The effect of PTC124 on choroideremia fibroblasts and iPSC-derived RPE raises considerations for therapy

Inherited retinal dystrophies (IRDs) are caused by mutations in over 200 genes, resulting in a range of therapeutic options. Translational read-through inducing drugs (TRIDs) offer the possibility of treating multiple IRDs regardless of the causative gene. TRIDs promote ribosomal misreading of premature stop codons, which results in the incorporation of a near-cognate amino acid to produce a full-length protein. The IRD choroideremia (CHM) is a pertinent candidate for TRID therapy, as nonsense variants cause 30% of cases. Recently, treatment of the UAA nonsense-carrying CHM zebrafish model with the TRID PTC124 corrected the underlying biochemical defect and improved retinal phenotype. To be clinically relevant, we studied PTC124 efficiency in UAA nonsense-carrying human fibroblasts and induced pluripotent stem cell-derived retinal pigment epithelium, as well as in a UAA-mutated CHM overexpression system. We showed that PTC124 treatment induces a non-significant trend for functional rescue, which could not be improved by nonsense-mediated decay inhibition. Furthermore, it does not produce a detectable CHM-encoded protein even when coupled with a proteasome inhibitor. We suggest that drug efficiency may depend upon on the target amino acid and its evolutionary conservation, and argue that patient cells should be screened in vitro prior to inclusion in a clinical trial.

Anti-Brucella activity of Caryopteris mongolica Bunge root extract against Brucella melitensis infection in mice

Background

The current treatment for human brucellosis requires a combination of antibiotics for long periods of time, and the reported incidence and prevalence of the disease vary widely in nomadic livestock of Mongolia. The objective of the present study was to evaluate the in vivo antibacterial activity of the C. mongolica root extract against B. melitensis.

Methods

In this study, we used of 6 groups of mice (n = 5). Five groups of BALB/c mice were inoculated intraperitoneally with the M16 strain of B. melintensis, as follows: (i) one group was used for pretreatment monitoring; (ii) the control group was administered 2% Tween 80 and was used as the non-treatment group; and the other three groups were treated with one oral gavage per day for 21 days with (iii) doxycycline (2 mg/day), (iv) doxycycline (1 mg/day) with root extract (20 mg/day), and (v) C. mongolica root extract (20 mg/day). The one group that was kept non-infected was used as a healthy control group.

Results

This study demonstrated that daily treatment with doxycycline alone and in combination with C. mongolica root extract significantly reduced splenic infection at the end of treatment. However, the spleen index of both the doxycycline-treated and the combination-treated groups of mice decreased by approximately 50% compared to that of the healthy control mouse group. Treatment with the C. mongolica root extract resulted in a 1.47log reduction in splenic infection compared to the non-treatment group, and the spleen index of the C. mongolica-treated group of mice was the same as that of the normal mouse group. In all treatment groups, neutrophil phagocytic activity significantly decreased, and all treatment groups demonstrated splenic regeneration.

Conclusions

The present study showed that the C. mongolica root extract may be useful in the treatment of brucellosis patients, in combination with doxycycline or other antibiotics, to reduce the toxicity of high-dosage antibiotics, to prevent the development of antibiotic resistance and to prevent Brucella infection.

Recent Updates on Treatment of Ocular Microbial Infections by Stem Cell Therapy: A Review

Ocular microbial infection has emerged as a major public health crisis during the past two decades. A variety of causative agents can cause ocular microbial infections; which are characterized by persistent and destructive inflammation of the ocular tissue; progressive visual disturbance; and may result in loss of visual function in patients if early and effective treatments are not received. The conventional therapeutic approaches to treat vision impairment and blindness resulting from microbial infections involve antimicrobial therapy to eliminate the offending pathogens or in severe cases; by surgical methods and retinal prosthesis replacing of the infected area. In cases where there is concurrent inflammation, once infection is controlled, anti-inflammatory agents are indicated to reduce ocular damage from inflammation which ensues. Despite advances in medical research; progress in the control of ocular microbial infections remains slow. The varying level of ocular tissue recovery in individuals and the incomplete visual functional restoration indicate the chief limitations of current strategies. The development of a more extensive therapy is needed to help in healing to regain vision in patients. Stem cells are multipotent stromal cells that can give rise to a vast variety of cell types following proper differentiation protocol. Stem cell therapy shows promise in reducing inflammation and repairing tissue damage on the eye caused by microbial infections by its ability to modulate immune response and promote tissue regeneration. This article reviews a selected list of common infectious agents affecting the eye; which include fungi; viruses; parasites and bacteria with the aim of discussing the current antimicrobial treatments and the associated therapeutic challenges. We also provide recent updates of the advances in stem cells studies on sepsis therapy as a suggestion of optimum treatment regime for ocular microbial infections.

Targeting mutant p53 for efficient cancer therapy

The tumour suppressor gene TP53 is the most frequently mutated gene in cancer. Wild-type p53 can suppress tumour development by multiple pathways. However, mutation of TP53 and the resultant inactivation of p53 allow evasion of tumour cell death and rapid tumour progression. The high frequency of TP53 mutation in tumours has prompted efforts to restore normal function of mutant p53 and thereby trigger tumour cell death and tumour elimination. Small molecules that can reactivate missense-mutant p53 protein have been identified by different strategies, and two compounds are being tested in clinical trials. Novel approaches for targeting TP53 nonsense mutations are also underway. This Review discusses recent progress in pharmacological reactivation of mutant p53 and highlights problems and promises with these strategies.

Amikacin: Uses, Resistance, and Prospects for Inhibition

Aminoglycosides are a group of antibiotics used since the 1940s to primarily treat a broad spectrum of bacterial infections. The primary resistance mechanism against these antibiotics is enzymatic modification by aminoglycoside-modifying enzymes that are divided into acetyl-transferases, phosphotransferases, and nucleotidyltransferases. To overcome this problem, new semisynthetic aminoglycosides were developed in the 70s. The most widely used semisynthetic aminoglycoside is amikacin, which is refractory to most aminoglycoside modifying enzymes. Amikacin was synthesized by acylation with the l-(-)-γ-amino-α-hydroxybutyryl side chain at the C-1 amino group of the deoxystreptamine moiety of kanamycin A. The main amikacin resistance mechanism found in the clinics is acetylation by the aminoglycoside 6'-N-acetyltransferase type Ib [AAC(6')-Ib], an enzyme coded for by a gene found in integrons, transposons, plasmids, and chromosomes of Gram-negative bacteria. Numerous efforts are focused on finding strategies to neutralize the action of AAC(6')-Ib and extend the useful life of amikacin. Small molecules as well as complexes ionophore-Zn⁺² or Cu⁺² were found to inhibit the acetylation reaction and induced phenotypic conversion to susceptibility in bacteria harboring the aac(6')-Ib gene. A new semisynthetic aminoglycoside, plazomicin, is in advance stage of development and will contribute to renewed interest in this kind of antibiotics.

Hyperbaric oxygen treatment and nephrotoxicity induced by gentamicin in rats

Background

Nephrotoxicity is a significant adverse side effect of gentamicin. Previous preclinical studies showed that hyperbaric oxygen treatment (HBOT) may have beneficial effects by attenuating renal damage in rats subjected to renal injury. We evaluated the effect of HBOT on acute renal failure caused by gentamicin.

Methods

Thirty-six rats were divided into four groups. Gentamicin (150 mg/kg for 5 consecutive days) was administered in 30 rats, 10 rats received only gentamicin, 10 rats received 100% oxygen therapy on days 1-5 of the experiment, 10 received daily HBOT on days 1-5 of the experiment, and the remaining six served as a control group. On day 6, renal function tests and renal pathological examinations were performed.

Results

Body weight and biochemical parameters were similar in all groups except for higher plasma levels of calcium in the 100% oxygen group (P = 0.03). All the rats in the experimental group showed biochemical parameters compatible with renal failure (high serum levels of urea and creatinine). All the rats in the control group had normal renal function tests. Two rats from the HBOT group died on the fifth day of the experiment. All rats in the control group demonstrated normal renal morphology. All 28 intoxicated rats showed moderate to severe histopathological changes without significant differences between the groups.

Conclusions

Treatment of gentamicin-induced nephrotoxicity with either HBOT or 100% oxygen for 5 days had no beneficial renal effect. Mortality was observed only in the HBOT group.

Renal Physiology and Robotic Urological Surgery

The use of robotic-assisted laparoscopic techniques has transformed the face of urological surgery in the last decade, with demonstrable benefits over both unassisted laparoscopic and traditional open approaches. For example, robotic-assisted partial nephrectomy is associated with lower morbidity, improved convalescence, reduced postoperative pain, shorter length of hospital stay, and a superior cosmetic result when compared to an open procedure. This review discusses the various perioperative influences on the renal physiology of patients undergoing robotic-assisted urological procedures.