Drug–drug interactions and safety of linezolid, tedizolid, and other oxazolidinones

Pharmacology of emerging drugs for the treatment of multi-drug resistant tuberculosis

Mycobacterium tuberculosis (TB) remains the leading cause of infection-related mortality worldwide. Drug resistance, need for multiple antimycobacterial agents, prolonged treatment courses, and medication-related side effects are complicating factors to TB cure. The introduction of treatment regimens containing the novel agents bedaquiline, pretomanid, and linezolid, with or without moxifloxacin (BPaL-M or BPaL, respectively) have substantially reduced TB-related morbidity and mortality and are associated with favorable rates of treatment completion and cure. This review summarizes key information on the pharmacology and treatment principles for moxifloxacin, bedaquiline, delamanid, pretomanid, linezolid, and tedizolid in the treatment of multi-drug resistant TB, with recommendations provided to address and attenuate common adverse effects during treatment.

Pharmacokinetics and Safety of Linezolid Tablets of 2 Different Manufacturers in Healthy Chinese Subjects in Fasting and Fed States

This study aimed to evaluate the pharmacokinetics (PKs) and safety of a generic drug, linezolid, compared to those of a reference drug in healthy Chinese subjects under both fasting and fed conditions. This was a randomized, open-label, 2-period, 2-sequence crossover study. The subjects received a single dose of the test or reference drug, linezolid (600 mg), in each period. The PK parameters were calculated using a non-compartmental method and compared between the 2 drugs. Bioequivalence was analyzed using geometric mean ratios (GMRs) of the 2 formulations and their corresponding 90% confidence intervals (CIs). The safety of the 2 formulations was assessed under both fasting and fed conditions. Forty-eight subjects completed the study, 24 each in the fasting and feeding groups. The average plasma concentration-time patterns of linezolid were similar for both medications under both conditions. The GMR and 90% CIs of the maximum plasma concentration and the area under the plasma concentration-time curve of linezolid were ranged from 0.80 to 1.25. Both drugs were well tolerated with a similar incidence of adverse drug reactions. In conclusion, the PK and safety profiles of the 2 formulations were comparable. Food intake did not influence the PK profiles of linezolid. These results suggest that the test drug can be used as an alternative to reference drugs.

New Oxazolidinones for Tuberculosis: Are Novel Treatments on the Horizon?

Multidrug-resistant tuberculosis (MDR-TB) is a global health concern. Standard treatment involves the use of linezolid, a repurposed oxazolidinone. It is associated with severe adverse effects, including myelosuppression and mitochondrial toxicity. As such, it is imperative to identify novel alternatives that are better tolerated but equally or more effective. Therefore, this review aims to identify and explore the novel alternative oxazolidinones to potentially replace linezolid in the management of TB. The keywords tuberculosis and oxazolidinones were searched in PubMed to identify eligible compounds. The individual drug compounds were then searched with the term tuberculosis to identify the relevant in vitro, in vivo and clinical studies. The search identified sutezolid, tedizolid, delpazolid, eperezolid, radezolid, contezolid, posizolid and TBI-223, in addition to linezolid. An additional search resulted in 32 preclinical and 21 clinical studies. All novel oxazolidinones except posizolid and eperezolid resulted in positive preclinical outcomes. Sutezolid and delpazolid completed early phase 2 clinical studies with better safety and equal or superior efficacy. Linezolid is expected to continue as the mainstay therapy, with renewed interest in drug monitoring. Sutezolid, tedizolid, delpazolid and TBI-223 displayed promising preliminary results. Further clinical studies would be required to assess the safety profiles and optimize the dosing regimens.

Mtb-Selective 5-Aminomethyl Oxazolidinone Prodrugs: Robust Potency and Potential Liabilities

Linezolid is a drug with proven human antitubercular activity whose use is limited to highly drug-resistant patients because of its toxicity. This toxicity is related to its mechanism of action─linezolid inhibits protein synthesis in both bacteria and eukaryotic mitochondria. A highly selective and potent series of oxazolidinones, bearing a 5-aminomethyl moiety (in place of the typical 5-acetamidomethyl moiety of linezolid), was identified. Linezolid-resistant mutants were cross-resistant to these molecules but not vice versa. Resistance to the 5-aminomethyl molecules mapped to an N-acetyl transferase (Rv0133) and these mutants remained fully linezolid susceptible. Purified Rv0133 was shown to catalyze the transformation of the 5-aminomethyl oxazolidinones to their corresponding N-acetylated metabolites, and this transformation was also observed in live cells of Mycobacterium tuberculosis. Mammalian mitochondria, which lack an appropriate N-acetyltransferase to activate these prodrugs, were not susceptible to inhibition with the 5-aminomethyl analogues. Several compounds that were more potent than linezolid were taken into C3HeB/FeJ mice and were shown to be highly efficacious, and one of these (9) was additionally taken into marmosets and found to be highly active. Penetration of these 5-aminomethyl oxazolidinone prodrugs into caseum was excellent. Unfortunately, these compounds were rapidly converted into the corresponding 5-alcohols by mammalian metabolism which retained antimycobacterial activity but resulted in substantial mitotoxicity.

Comparison of Plasma Concentration of Linezolid's Detection by FICA and LC-MS/MS

Linezolid was the first totally synthetic oxazolidinone antibiotic that was approved for clinical use against Mycobacterium tuberculosis. Our study investigated the correlation and consistency of fluorescence immunochromatography assay (FICA) and high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) in measuring linezolid levels in the plasma. Plasma samples were collected from 80 to 100 tuberculosis patients. The samples were analyzed by FICA and LC-MS/MS, and linezolid levels measured by the two methods were compared by outlier test, correlation coefficient, Bland-Altman scatter plot, Deming regression analysis and bias evaluation. A total of 83 plasma samples were collected, all of which were non-outlier. The correlation coefficient of FICA and LC-MS/MS results was 0.9845. Deming regression analysis showed that the regression equation of FICA and LC-MS/MS was y = 0.2229 + 1.0076x. The medical decision levels of 2 and 7 μg/mL were taken into the regression equation, and the 95% CI of 2- and 7-μg/mL bias were both within the allowed error range. The findings indicated a strong correlation between the results obtained from FICA and LC-MS/MS were consistent showed good correlation, demonstrating their equivalence in measurement.

In Vitro Activities of Oxazolidinone Antibiotics Alone and in Combination with C-TEMPO against Methicillin-Resistant Staphylococcus aureus Biofilms

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a global health concern. The propensity of MRSA to form biofilms is a significant contributor to its pathogenicity. Strategies to treat biofilms often involve small molecules that disperse the biofilm into planktonic cells. Linezolid and, by extension, theoxazolidinones have been developed to treat infections caused by Gram-positive bacteria such as MRSA. However, the clinical development of these antibiotics has mainly assessed the susceptibility of planktonic cells to the drug. Previous studies evaluating the anti-biofilm activity of theoxazolidinones have mainly focused on the biofilm inhibition of Enterococcus faecalis and methicillin-sensitive Staphylococcus aureus, with only a few studies investigating the activity of oxazolidinones for eradicating established biofilms for these species. Very little is known about the ability of oxazolidinones to eradicate MRSA biofilms. In this work, five oxazolidinones were assessed against MRSA biofilms using a minimum biofilm eradication concentration (MBEC) assay. All oxazolidinones had inherent antibiofilm activity. However, only ranbezolid could completely eradicate MRSA biofilms at clinically relevant concentrations. The susceptibility of the MRSA biofilms to ranbezolid was synergistically enhanced by coadministration with the nitroxide biofilm dispersal agent C-TEMPO. We presume that ranbezolid acts as a dual warhead drug, which combines the mechanism of action of the oxazolidinones with a nitric oxide donor or cytotoxic drug.

Pharmacokinetic and Pharmacodynamic Considerations of Novel Antibiotic Agents for Pediatric Infections: A Narrative Review

Background: Currently, the escalation of microbial resistance poses a significant global challenge. Children are more susceptible to develop infections and therefore are prescribed antibiotics more frequently. The overuse and misuse of antibiotics in pediatric patients can play a considerable role in developing microbial resistance. Accordingly, many policies, including research into new antibiotic agents have been recommended to combat microbial resistance. Recent developments in novel antibiotics have shown promising results against multi-drug resistant (MDR) and extensive drug resistance (XDR) pathogens. However, as pediatric patients are typically excluded from the clinical trials of new medications, labeling and information about approved antibiotics should be improved. This study aimed to evaluate antibiotics having been introduced to the market in the last decade focusing on pediatric population. Methods: This study reviewed the published literatures on novel FDA-approved antibiotics released between 2010 and 2022. Results: Finally, seven newly approved antibiotics including ceftaroline fosamil, ceftazidime-avibactam, ceftolozane-tazobactam, ceftobiprole, imipenem-cilastatin-relebactam, meropenem-vaborbactam, and tedizolid were considered in the present review-article. All relevant data extracted from literatures, were discussed in different subtitles of "Pharmacology", "Mechanism of action", "Indication", "Dosage regimen and pharmacokinetic and pharmacodynamic properties", "Dosage adjustment in renal/liver failure", "Resistance pattern", and "Adverse drug events". Conclusion: This study reviewed available data on seven new antibiotic agents and their pharmacodynamic and pharmacokinetic properties, with a particular focus on their use in pediatric patients. The information presented in this review will be useful for healthcare professionals in selecting appropriate antibiotics for pediatric patients and for researchers in achieving the ideal therapeutic regimens.

In silico structural and mechanical insights into bedaquiline resistance associated with high-grade non-synonymous mutations in atpE, mmpR5, and pepQ

Clinical resistance against bedaquiline (BDQ) remains intractable to anti-tuberculosis therapies since its introduction to the market over a decade ago. Herein, we investigated the structural and mechanical aspects of BDQ resistance in AtpE, MmpR5, and PepQ. The known target-specific resistant single non-synonymous mutations were refined to high-grade candidates. Thus, 7 (AtpE), 5 (MmpR5), and 1 (PepQ) single nucleotide polymorphisms (SNPs) and one insertion frameshift mutation in MmpR5 were recreated at the molecular level, and these phenotypic models were then directed to stringent dynamics to define time-scaled changes. The AtpE variants destabilized the structure; mainly, L59V, E61D, and I66M were detrimental to the complex fitness, while L74V and L114P boosted the BDQ binding to MmpR5. The first three and last two alterations gave rise to loss- and gain-of-function to AtpE and MmpR5, respectively. Hence, these five mutants are functionally relevant and therapeutically targetable hotspots of BDQ resistance. There were no noticeable changes in PepQ data analysis. The present study revealed that MmpR5 mutations confer BDQ resistance, whereas AtpE and PepQ SNPs display low susceptibility. These results were tallied with the published findings, which testified to the pursued method's reliability and accuracy. We hope these data and inferences could be helpful for the futuristic design of novel TB drugs.Communicated by Ramaswamy H. Sarma.

Staph wars: the antibiotic pipeline strikes back

Antibiotic chemotherapy is widely regarded as one of the most significant medical advancements in history. However, the continued misuse of antibiotics has contributed to the rapid rise of antimicrobial resistance (AMR) globally. Staphylococcus aureus, a major human pathogen, has become synonymous with multidrug resistance and is a leading antimicrobial-resistant pathogen causing significant morbidity and mortality worldwide. This review focuses on (1) the targets of current anti-staphylococcal antibiotics and the specific mechanisms that confirm resistance; (2) an in-depth analysis of recently licensed antibiotics approved for the treatment of S. aureus infections; and (3) an examination of the pre-clinical pipeline of anti-staphylococcal compounds. In addition, we examine the molecular mechanism of action of novel antimicrobials and derivatives of existing classes of antibiotics, collate data on the emergence of resistance to new compounds and provide an overview of key data from clinical trials evaluating anti-staphylococcal compounds. We present several successful cases in the development of alternative forms of existing antibiotics that have activity against multidrug-resistant S. aureus. Pre-clinical antimicrobials show promise, but more focus and funding are required to develop novel classes of compounds that can curtail the spread of and sustainably control antimicrobial-resistant S. aureus infections.

SPILF update on bacterial arthritis in adults and children

In 2020 the French Society of Rhumatology (SFR) published an update of the 1990 recommendations for management of bacterial arthritis in adults. While we (French ID Society, SPILF) totally endorse this update, we wished to provide further information about specific antibiotic treatments. The present update focuses on antibiotics with good distribution in bone and joint. It is important to monitor their dosage, which should be maximized according to PK/PD parameters. Dosages proposed in this update are high, with the optimized mode of administration for intravenous betalactams (continuous or intermittent infusion). We give tools for the best dosage adaptation to conditions such as obesity or renal insufficiency. In case of enterobacter infection, with an antibiogram result "susceptible for high dosage", we recommend the requesting of specialized advice from an ID physician. More often than not, it is possible to prescribe antibiotics via the oral route as soon as blood cultures are sterile and clinical have symptoms shown improvement. Duration of antibiotic treatment is 6 weeks for Staphylococcus aureus, and 4 weeks for the other bacteria (except for Neisseria: 7 days).

Properties of Poly (Lactic-co-Glycolic Acid) and Progress of Poly (Lactic-co-Glycolic Acid)-Based Biodegradable Materials in Biomedical Research

In recent years, biodegradable polymers have gained the attention of many researchers for their promising applications, especially in drug delivery, due to their good biocompatibility and designable degradation time. Poly (lactic-co-glycolic acid) (PLGA) is a biodegradable functional polymer made from the polymerization of lactic acid (LA) and glycolic acid (GA) and is widely used in pharmaceuticals and medical engineering materials because of its biocompatibility, non-toxicity, and good plasticity. The aim of this review is to illustrate the progress of research on PLGA in biomedical applications, as well as its shortcomings, to provide some assistance for its future research development.

Biomimetic cell membrane-coated poly(lactic-co-glycolic acid) nanoparticles for biomedical applications

Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) are commonly used for drug delivery because of their favored biocompatibility and suitability for sustained and controlled drug release. To prolong NP circulation time, enable target-specific drug delivery and overcome physiological barriers, NPs camouflaged in cell membranes have been developed and evaluated to improve drug delivery. Here, we discuss recent advances in cell membrane-coated PLGA NPs, their preparation methods, and their application to cancer therapy, management of inflammation, treatment of cardiovascular disease and control of infection. We address the current challenges and highlight future research directions needed for effective use of cell membrane-camouflaged NPs.

A Retrospective Study to Compare the Incidence of Hyponatremia after Administration between Linezolid and Tedizolid

Linezolid (LZD) and Tedizolid (TZD) are oxazolidinone antibiotic for meticillin-resistant Staphylococcus aureus (MRSA). Severe hyponatremia after LZD administration have been reported. Severe hyponatremia cause seizures, unconsciousness, and even death. Therefore, we conducted a study to assess the change of serum sodium level after LZD and TZD therapy. We enrolled 67 patients treated with LZD and 28 treated with TZD. We monitored the serum sodium level from the administration to 14 days after administration of oxazolidinone drug. Hyponatremia was defined a sodiuln level ≤134 mmol/L after the initiation of oxazolidinone drug. The frequency of hyponatremia in the LZD group was significantly higher than that in the TZD group (39.7% vs. 11.1%, p < 0.05). The rate of patients administered by injection was significantly higher than in the LZD group than in the TZD group (52.9% vs. 14.8%, p < 0.01). Multiple logistic regression analyses identified the albumin level before the oxazolidinone drug therapy as the independent variables associated with the development of hyponatremia. We revealed that TZD is safer than LZD in terms of hyponatremia. Therefore, cases that LZD is administered by injection should be used more carefully with hyponatremia in patients with low albumin level.

Loss of erm(B)-Mediated rRNA Dimethylation and Restoration of Erythromycin Susceptibility in Erythromycin-Resistant Enterococci Following Induced Linezolid Resistance

Linezolid has been reported to restore erythromycin susceptibility in erythromycin-resistant Staphylococcus aureus. This phenomenon has not been reported in enterococci and the mechanisms involved therein are still unknown. The purpose of this study was to investigate the mechanisms involved and the effect of combining linezolid with erythromycin on erythromycin-resistant enterococci. Checkerboard techniques were used to determine drug interactions, and 12 of 14 isolates showed a synergistic effect between erythromycin and linezolid (fractional inhibitory concentration <0.5). We observed that the erm(B) gene, which encodes a dimethyltransferase responsible for erythromycin resistance, was expressed from transposon Tn1545 in the tested erythromycin-resistant enterococci. After exposure to linezolid, erm(B)-mediated rRNA dimethylation at A2071 could not be detected, and the erm(B) gene was lost following acquisition of erythromycin susceptibility. Thus, in conclusion, linezolid combined with erythromycin exerts a synergistic effect against erythromycin-resistant enterococci. Linezolid treatment suppressed erm(B)-mediated rRNA dimethylation at A2071, which could lead to loss of the erm(B) gene.

Linezolid pharmacokinetics: a systematic review for the best clinical practice

OBJECTIVES

To summarize the pharmacokinetics of linezolid to optimize the dosing regimen in special populations.

METHODS

A literature search was performed in three largest medical databases, including Embase, Scopus, and PubMed. The main applied keywords were linezolid and pharmacokinetics. Of 3663 retrieved publications in the English language, 35 original research articles, clinical studies, and case reports about linezolid pharmacokinetics in different populations such as pregnant women, pediatrics, elderly subjects, obese people, individuals with organ dysfunction, and critically ill patients were included. RESULTS AND CONCLUSION: Dose adjustment is not currently recommended for linezolid in patients with mild to moderate renal or hepatic impairment, older adults, and pregnant women. Although dose adjustment is not recommended in patients with severe renal or hepatic impairment, it should be considered that these patients are more vulnerable to linezolid adverse effects and drug interactions. In pediatrics, reducing the linezolid dosing interval to 8 h is suggested. Despite the lack of sufficient information in obese individuals, dosing based on body weight or use of higher dose seems to be justifiable to prevent sub-therapeutic concentrations. Although dose adjustment of linezolid is not recommended in critically ill patients, administration of linezolid as continuous intravenous infusion is suggested in this population. Blood level monitoring should be considered in populations that are vulnerable to linezolid underexposure (such as critically ill patients with augmented renal clearance, pediatrics, overweight, and obese patients) or overexposure (such as elderly, patients with hepatic and renal impairment). To assess the efficacy and safety of linezolid, the area under the concentration-time curve over 24 h to minimum inhibitory concentration (AUC0-24 h/MIC) equal to 80-120, percentage of time above the MIC ≥ 85%, and serum trough concentration between 2 and 7 mg/L are suggested.

Association of Linezolid With Risk of Serotonin Syndrome in Patients Receiving Antidepressants

IMPORTANCE

Linezolid has the potential to interact with some antidepressants, leading to serotonin syndrome. However, few empirical data support warnings for patients taking antidepressants to avoid linezolid.

OBJECTIVES

To examine the incidence of serotonin syndrome in patients receiving oral linezolid and how concomitant antidepressant treatment changes this risk.

DESIGN, SETTING, AND PARTICIPANTS

This population-based, retrospective cohort study used linked administrative databases at ICES to collect data from outpatients 66 years or older in Ontario, Canada, who were prescribed oral linezolid for any duration from October 1, 2014, to January 1, 2021, with follow-up to 30 days (January 31, 2021).

EXPOSURES

The use of antidepressants while receiving linezolid therapy vs no antidepressant use while receiving linezolid therapy.

MAIN OUTCOMES AND MEASURES

The primary outcome was clinically significant serotonin syndrome based on a physician diagnosis, Sternbach criteria, or the Hunter Serotonin Toxicity Criteria within 30 days of starting oral linezolid treatment. Secondary outcomes were altered mental status, hospitalization, or death within 30 days of starting linezolid treatment.

RESULTS

The study included 1134 patients (age ranges, 66-69 years for 225 patients [19.8%], 70-79 years for 473 patients [41.7%], and ≥80 years for 436 patients [38.4%]; 595 [52.5%] male) who were prescribed linezolid. Of 1134 patients, 215 (19.0%) were also taking antidepressants. Serotonin syndrome occurred in fewer than 6 patients (<0.5%). The number of serotonin syndrome cases were fewer in the antidepressant group. In a propensity score-matched cohort, the adjusted risk difference for serotonin syndrome between the antidepressant group and the no antidepressant group was -1.2% (95% CI, -2.9% to 0.5%). There were similar rates of altered mental status, hospitalization, and death between the propensity score-matched groups.

CONCLUSIONS AND RELEVANCE

In this cohort study of older patients who were prescribed linezolid, serotonin syndrome occurred rarely. Concurrent antidepressants did not significantly increase the risk of serotonin syndrome. These findings suggested that linezolid is likely safe for patients receiving antidepressants. Nevertheless, prescribers should remain vigilant for this potential drug interaction.

MRSA and Skin Infections in Psoriatic Patients: Therapeutic Options and New Perspectives

Psoriatic patients present various infectious risk factors, but there are few studies in the literature evaluating the actual impact of psoriasis in severe staphylococcal skin infections. Our narrative review of the literature suggests that psoriatic patients are at increased risk of both colonization and severe infection, during hospitalization, by S. aureus. The latter also appears to play a role in the pathogenesis of psoriasis through the production of exotoxins. Hospitalized psoriatic patients are also at increased risk of MRSA skin infections. For this reason, new molecules are needed that could both overcome bacterial resistance and inhibit exotoxin production. In our opinion, in the near future, topical quorum sensing inhibitors in combination with current anti-MRSA therapies will be able to overcome the increasing resistance and block exotoxin production. Supplementation with Vitamin E (VE) or derivatives could also enhance the effect of anti-MRSA antibiotics, considering that psoriatic patients with metabolic comorbidities show a low intake of VE and low serum levels, making VE supplementation an interesting new perspective.

Role of Daptomycin in Cutaneous Wound Healing: A Narrative Review

Daptomycin is active against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and the on-label indications for its use include complicated skin and skin structure infections (cSSSI). We performed a narrative review of the literature with the aim to evaluate the role of daptomycin in the skin wound healing process, proposing our point of view on the possible association with other molecules that could improve the skin healing process. Daptomycin may improve wound healing in MRSA-infected burns, surgical wounds, and diabetic feet, but further studies in humans with histological examination are needed. In the future, the combination of daptomycin with other molecules with synergistic action, such as vitamin E and derivates, IB-367, RNA III-inhibiting peptide (RIP), and palladium nanoflowers, may help to improve wound healing and overcome forms of antibiotic resistance.

A Review of Population Pharmacokinetic Analyses of Linezolid

In recent years, many studies on population pharmacokinetics of linezolid have been conducted. This comprehensive review aimed to summarize population pharmacokinetic models of linezolid, by focusing on dosage optimization to maximize the probability of attaining a certain pharmacokinetic-pharmacodynamic parameter in special populations. We searched the PubMed and EMBASE databases for population pharmacokinetic analyses of linezolid using a parametric non-linear mixed-effect approach, including both observational and prospective trials. Of the 32 studies, 26 were performed in adults, four in children, and one in both adults and children. High between-subject variability was determined in the majority of the models, which was in line with the variability of linezolid concentrations previously detected in observational studies. Some studies found that patients with renal impairment, hepatic failure, advanced age, or low body weight had higher exposure and adverse reactions rates. In contrast, lower concentrations and therapeutic failure were associated with obese patients, young patients, and patients who had undergone renal replacement techniques. In critically ill patients, the inter-individual and intra-individual variability was even greater, suggesting that this population is at an even higher risk of underexposure and overexposure. Therapeutic drug monitoring may be warranted in a large proportion of patients given that the Monte Carlo simulations demonstrated that the one-size-fits-all labeled dosing of 600 mg every 12 h could lead to toxicity or therapeutic failure for high values of the minimum inhibitory concentration of the target pathogen. Further research on covariates, including renal function, hepatic function, and drug–drug interactions related to P-glycoprotein could help to explain variability and improve linezolid dosing regimens.

Clinical standards for the dosing and management of TB drugs

BACKGROUND: Optimal drug dosing is important to ensure adequate response to treatment, prevent development of drug resistance and reduce drug toxicity. The aim of these clinical standards is to provide guidance on 'best practice´ for dosing and management of TB drugs.METHODS: A panel of 57 global experts in the fields of microbiology, pharmacology and TB care were identified; 51 participated in a Delphi process. A 5-point Likert scale was used to score draft standards. The final document represents the broad consensus and was approved by all participants.RESULTS: Six clinical standards were defined: Standard 1, defining the most appropriate initial dose for TB treatment; Standard 2, identifying patients who may be at risk of sub-optimal drug exposure; Standard 3, identifying patients at risk of developing drug-related toxicity and how best to manage this risk; Standard 4, identifying patients who can benefit from therapeutic drug monitoring (TDM); Standard 5, highlighting education and counselling that should be provided to people initiating TB treatment; and Standard 6, providing essential education for healthcare professionals. In addition, consensus research priorities were identified.CONCLUSION: This is the first consensus-based Clinical Standards for the dosing and management of TB drugs to guide clinicians and programme managers in planning and implementation of locally appropriate measures for optimal person-centred treatment to improve patient care.

Strategies to Improve the Potency of Oxazolidinones towards Bacterial Biofilms

Biofilms are part of the natural lifecycle of bacteria and are known to cause chronic infections that are difficult to treat. Most antibiotics are developed and tested against bacteria in the planktonic state and are ineffective against bacterial biofilms. The oxazolidinones, including the last resort drug linezolid, are one of the main classes of synthetic antibiotics progressed to clinical use in the last 50 years. They have a unique mechanism of action and only develop low levels of resistance in the clinical setting. With the aim of providing insight into strategies to design more potent antibiotic compounds with activity against bacterial biofilms, we review the biofilm activity of clinically approved oxazolidinones and report on structural modifications to oxazolidinones and their delivery systems which lead to enhanced anti-biofilm activity.

Mycobacterium fortuitum peritoneal dialysis-related peritonitis in a child: A case report and review of the literature

BACKGROUND

Non-tuberculous mycobacteria (NTM) are an uncommon but serious cause of peritoneal dialysis (PD)-related infections. NTM peritonitis typically necessitates PD catheter removal, PD withdrawal, and aggressive, prolonged antimicrobial treatment. Few reported cases of NTM peritonitis in the pediatric population exist.

METHODS

We describe a case of a 9-year-old boy on PD after kidney allograft failure who developed Mycobacterium fortuitum peritonitis, and we summarize the available literature on M. fortuitum peritonitis in pediatric patients receiving PD.

RESULTS AND CONCLUSION

Therapeutic options were limited by adverse medication effects and risk of drug-drug interactions in a patient with complex mental health comorbidities. Clofazimine presented an acceptable oral treatment option for long-term therapy in combination with ciprofloxacin and was well tolerated by this patient. Prompt PD catheter removal followed by 6 months of dual antimicrobial therapy resulted in a full recovery and successful re-transplantation with no infection relapse.

Long-term use of tedizolid for pulmonary nocardiosis

Nocardiosis usually occurs in immunocompromised patients and causes infections in various organs, including the lungs, skin, and organs of the central nervous system. Herein, we report the case of a patient with minimal change nephrotic syndrome who had been on immunosuppressive drugs and developed pulmonary nocardiosis due to Nocardia nova complex and Pneumocystis pneumonia. For pulmonary nocardiosis, trimethoprim-sulfamethoxazole, linezolid, and clarithromycin were initiated sequentially, but were subsequently discontinued due to side effects; the treatment was completed with tedizolid. Tedizolid was used safely for 200 out of 286 days of antibiotic treatment, and clinical improvement was observed. Tedizolid is a bacteriostatic oxazolidine antibiotic that inhibits bacterial protein synthesis, the same mechanism as its predecessor, linezolid. Tedizolid is thought to cause less frequent myelosuppression than linezolid, at least for short-term use. In the future, tedizolid may be a promising alternative to linezolid in cases of nocardiosis that usually require long-term treatment.

Early Bactericidal Activity of Delpazolid (LCB01-0371) in Patients with Pulmonary Tuberculosis

Delpazolid, an oxazolidinone, has been studied in non-clinical studies of efficacy and toxicity and Phase 1 clinical studies. Delpazolid has in vitro activity against Gram-positive bacteria, including Mycobacterium tuberculosis. This study evaluated the bactericidal activity, safety, and pharmacokinetics of delpazolid in patients with pulmonary tuberculosis (TB). Seventy-nine subjects, aged 19 to 75 years with newly diagnosed smear-positive TB with no prior treatment for the current episode and no confirmed resistance to rifampin or isoniazid, were randomized to receive delpazolid 800 mg once a day (QD), 400 mg twice a day (BID), 800 mg BID or 1,200 mg QD or an active control of isoniazid, rifampin, pyrazinamide, and ethambutol (HRZE) or linezolid 600 mg BID. The primary endpoint was the average daily reduction in log transformed bacterial load, assessed on 7H11 solid-media culture, from days 0 to 14. The average daily decline in log-CFU was 0.044 ± 0.016, 0.053 ± 0.017, 0.043 ± 0.016, and 0.019 ± 0.017, for the delpazolid 800 mg QD, 400 mg BID, 800 mg BID, and the 1,200 mg QD groups, respectively. The average daily decline in log-CFU was 0.192 ± 0.028 for the HRZE group and 0.154 ± 0.023 for the linezolid 600 mg BID group. Three serious adverse events (SAE) were reported, one each in the delpazolid 400 mg BID group (death due to worsening of TB at day 2), the HRZE group (hospitalization due to pleural effusion) and the linezolid group (hyperkalemia); none of the SAEs were assessed as related to study drugs. This study has been registered at ClinicalTrials.gov with registration number NCT02836483.

Cost of off-label antibiotic therapy for bone and joint infections: a 6-year prospective monocentric observational cohort study in a referral centre for management of complex osteo-articular infections

Introduction: Costs related to bone and joint infection (BJI) management are increasing worldwide, particularly due to the growing use of off-label antibiotics that are expensive treatments (ETs), in conjunction with increasing incidence of multi-drug-resistant pathogens. The aim of this study was to evaluate the whole costs related to these treatments during the patient route, including those attributed to the rehabilitation centre (RC) stay in one regional referral centre in France. The total annual cost of ETs for managing complex BJIs in France was then estimated.

Material and methods: A prospective monocentric observational study was conducted from 2014 to 2019 in a referral centre for BJI management (CRIOAc – Centre de Référence des Infections OstéoArticulaires complexes). Costs related to expensive treatments (“old” ETs, i.e. ceftaroline, ertapenem, daptomycin, colistin, tigecycline, and linezolid and “new” ETs, defined as those used since 2017, including ceftobiprole, ceftazidime-avibactam, ceftolozane-tazobactam, tedizolid, and dalbavancin) were prospectively recorded. In all cases, the use of these ETs was validated during multidisciplinary meetings.

Results: Of the 3219 patients treated, 1682 (52.3 %) received at least one ET, and 21.5 % of patients who received ET were managed in RCs. The overall cost of ETs remained high but stable (EUR 1 033 610 in 2014; EUR 1 129 862 in 2019), despite the increase of patients treated by ETs (from 182 in 2014 to 512 in 2019) and in the cumulative days of treatment (9739 to 16 191 d).

Daptomycin was the most prescribed molecule (46.2 % of patients in 2014 and 56.8 % in 2019, with 53.8 % overall), but its cost has decreased since this molecule was genericized in 2018; the same trend was observed for linezolid. Thus, costs for old ETs decreased overall, from EUR 1 033 610 in 2014 to EUR 604 997 in 2019, but global costs remained stable due to new ET utilization accounting for 46.5 % of overall costs in 2019. Tedizolid, used as suppressive antimicrobial therapy, represented 77.5 % of total new ET costs. In our centre, dalbavancin was never used.

The cost paid by RCs for ETs and the duration of ET remained stable overall between 2016 and 2019.

Conclusions: A high consumption of off-label ET is required to treat patients with BJIs in a CRIOAc, and the consequence is a high cost of antimicrobial therapy for these patients, estimated to be almost EUR 10 million in France annually. Costs associated with ET utilization remained stable over the years. On the one hand, the introduction of the generic drugs of daptomycin and linezolid has significantly decreased the share of old ETs, but, on the other hand, the need for new ETs to treat infections associated with more resistant pathogens has not led to decrease in the overall costs. A drastic price reduction of generic drugs is essential to limit the costs associated with more complex BJIs.

In vitro and in vivo activity of oxazolidinone candidate OTB-658 against Mycobacterium tuberculosis

In this work, we assess anti-tuberculosis activity of OTB-658 in vitro and in vivo. In vitro, OTB-658 showed bacteriostatic effectiveness with a lower minimum inhibitory concentration than linezolid against Mycobacterium tuberculosis. The minimal bactericidal concentrations and time-kill curves for OTB-658 indicated similar inhibition activity to that of linezolid. OTB-658 entered macrophages to inhibit of M. tuberculosis growth. OTB-658 had a low mutant frequency (10^-8), which would prevent drug-resistant mutations from emerging in combination regimens. In vivo, OTB-658 reduced colony-forming unit counts in the lungs and slightly inhibited bacterial growth in the spleen in the early stage and steady state in acute and chronic murine TB models. These results support the preclinical evaluation of OTB-658 and further clinical trials in China.

Safety of Tedizolid as Suppressive Antimicrobial Therapy for Patients With Complex Implant-Associated Bone and Joint Infection due to Multidrug-Resistant Gram-Positive Pathogens: Results From the TediSAT Cohort Study

A prospective cohort study was conducted to evaluate long-term safety of tedizolid as suppressive antimicrobial treatment in patients with implant-associated bone and joint infection caused by multidrug-resistant gram-positive pathogens. Seventeen patients received tedizolid with a median duration of treatment of 6 months. No patients developed a serious adverse event.

Identification of the Multiresistance Gene poxtA in Oxazolidinone-Susceptible Staphylococcus haemolyticus and Staphylococcus saprophyticus of Pig and Feed Origins

Previous studies on the prevalence and transmission mechanism of oxazolidinone resistance gene poxtA in CoNS are lacking, which this study addresses. By screening 763 CoNS isolates from different sources of several livestock farms in Guangdong, China, 2018–2020, we identified that the poxtA was present in seven CoNS isolates of pig and feed origins. Species identification and multilocus sequence typing (MLST) confirmed that seven poxtA-positive CoNS isolates were composed of five ST64-Staphylococcus haemolyticus and two Staphylococcus saprophyticus isolates. All poxtA-positive Staphylococcus haemolyticus isolates shared similar pulsed-field gel electrophoresis (PFGE) patterns. Transformation assays demonstrated all poxtA-positive isolates were able to transfer poxtA gene to Staphylococcus aureus RN4220. S1-PFGE and whole-genome sequencing (WGS) revealed the presence of poxtA-carrying plasmids in size around 54.7 kb. The plasmid pY80 was 55,758 bp in size and harbored the heavy metal resistance gene czcD and antimicrobial resistance genes, poxtA, aadD, fexB and tet(L). The regions (IS1216E-poxtA-IS1216E) in plasmid pY80 were identified in Staphylococcus spp. and Enterococcus spp. with different genetic and source backgrounds. In conclusion, this was the first report about the poxtA gene in Staphylococcus haemolyticus and Staphylococcus saprophyticus, and IS1216 may play an important role in the dissemination of poxtA among different Gram-positive bacteria.

Therapeutic Drug Monitoring Can Improve Linezolid Dosing Regimens in Current Clinical Practice: A Review of Linezolid Pharmacokinetics and Pharmacodynamics

Linezolid is an antibiotic used to treat infections caused by drug-resistant gram-positive organisms, including vancomycin-resistant Enterococcus faecium, multi-drug resistant Streptococcus pneumoniae, and methicillin-resistant Staphylococcus aureus. The adverse effects of linezolid can include thrombocytopenia and neuropathy, which are more prevalent with higher exposures and longer treatment durations. Although linezolid is traditionally administered at a standard 600 mg dose every 12 hours, the resulting exposure can vary greatly between patients and can lead to treatment failure or toxicity. The efficacy and toxicity of linezolid are determined by the exposure achieved in the patient; numerous clinical and population pharmacokinetics (popPK) studies have identified threshold measurements for both parameters. Several special populations with an increased need for linezolid dose adjustments have also been identified. Therapeutic Drug Monitoring (TDM) is a clinical strategy that assesses the response of an individual patient and helps adjust the dosing regimen to maximize efficacy while minimizing toxicity. Adaptive feedback control and model-informed precision dosing are additional strategies that use Bayesian algorithms and PK models to predict patient-specific drug exposure. TDM is a very useful tool for patient populations with sparse clinical data or known alterations in pharmacokinetics, including children, patients with renal insufficiency or those receiving renal replacement therapy, and patients taking co-medications known to interact with linezolid. As part of the clinical workflow, clinicians can use TDM with the thresholds summarized from the current literature to improve linezolid dosing for patients and maximize the probability of treatment success.

Initially Reduced Linezolid Dosing Regimen to Prevent Thrombocytopenia in Hemodialysis Patients

This retrospective cohort study investigated the effects of an initially reduced linezolid dosing regimen in hemodialysis patients through therapeutic drug monitoring (TDM). Patients were divided into two groups depending on their initial dose of linezolid (standard dose of 600 mg every 12 h or initially reduced dose of 300 mg every 12 h/600 mg every 24 h). The cumulative incidence rates of thrombocytopenia and severe thrombocytopenia were compared between both groups using the Kaplan-Meier method and log-rank test. Eleven episodes of 8 chronic hemodialysis patients were included; 5 were in the initially reduced-dose group. Thrombocytopenia developed in 81.8% of patients. The cumulative incidence rates of thrombocytopenia and severe thrombocytopenia in the initially reduced-dose group were significantly lower than in the standard-dose group (p < 0.05). At the standard dose, the median linezolid trough concentration (C_min) just before hemodialysis was 49.5 mg/L, and C_min at the reduced doses of 300 mg every 12 h and 600 mg every 24 h were 20.6 mg/L and 6.0 mg/L, respectively. All five episodes underwent TDM in the standard-dose group required dose reduction to 600 mg per day. Our findings indicate that initial dose reduction should be implemented to reduce the risk of linezolid-induced thrombocytopenia among hemodialysis patients.

Correlation of MRSA polymerase chain reaction (PCR) wound swab testing and wound cultures in skin and soft tissue infections

Methicillin-resistant Staphylococcus aureus is a considerable pathogen in the setting of skin and soft tissue infections (SSTIs). MRSA PCR swab testing is widely used in the setting of respiratory tract infections, however little data exists relating to the use of MRSA PCR swab testing in SSTIs. Three thousand, nine hundred and ninety-five patients were included in this retrospective study that aimed to validate the clinical correlation of MRSA PCR wound swab testing in SSTIs through sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) analysis. From this review, MRSA PCR wound swabs were found to have a sensitivity of 97.6% (97.5-98.5), a specificity of 94.9% (94.3-95.7), a PPV of 92.3% (91.4-93.2), and a NPV of 98.4% (98.0-98.8). The study results demonstrate that the MRSA SSTI PCR assays have a high NPV and the potential to be a vital tool in de-escalating antimicrobial therapy associated with SSTIs.

Proposal of initial and maintenance dosing regimens with linezolid for renal impairment patients

Background

Linezolid is administered as a fixed dose to all patients despite evidence of overexposure and thrombocytopenia in renal impairment. The aims of this study were to evaluate the risk of thrombocytopenia and the utility of therapeutic drug monitoring (TDM), and to propose alternate dosing regimens in patients with renal impairment.

Methods

We retrospectively reviewed patients ≥13 years old for whom serum linezolid trough concentration (C_min) was measured during linezolid treatment. Patients with episodes of infection were divided into groups by presence of renal impairment (RI group) or absence of renal impairment (non-RI group), and by use of C_min-based TDM (TDM group) or not (non-TDM group) during linezolid treatment.

Results

In the 108 patients examined by multivariable analyses, renal impairment was independently associated with increased risk of thrombocytopenia (OR 3.17, 95%CI 1.10–9.12) and higher C_min. Analysis of the utility of TDM in the RI group showed that clinical failure rate was significantly lower in the TDM subgroup than in the non-TDM subgroup. Furthermore, in the RI group, dosage adjustments were needed in 90.5% of the TDM subgroup. All episodes administered a reduced dose of 300 mg every 12 h in the RI group showed C_min ≥ 2.0 mg/L. Additional analysis of 53 episodes in which C_min was measured within 48 h after starting administration showed that the initial standard dose for 2 days was sufficient to rapidly reach an effective therapeutic concentration in the RI group.

Conclusions

Empirical dose reduction to 300 mg every 12 h after administration of the initial fixed dose for 2 days and C_min-based TDM may improve safety outcomes while maintaining appropriate efficacy among patients with renal impairment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40360-021-00479-w.

Ribosome-targeting antibacterial agents: Advances, challenges, and opportunities

Ribosomes, which synthesize proteins, are critical organelles for the survival and growth of bacteria. About 60% of approved antibiotics discovered so far combat pathogenic bacteria by targeting ribosomes. However, several issues, such as drug resistance and toxicity, have impeded the clinical use of ribosome-targeting antibiotics. Moreover, the complexity of the bacteria ribosome structure has retarded the discovery of new ribosome-targeting agents that are considered as the key to the drug-resistance and toxicity. To deal with these challenges, efforts such as medicinal chemistry optimization, combination treatment, and new drug delivery system have been developed. But not enough, the development of structural biology and new screening methods bring powerful tools, such as cryo-electron microscopy technology, advanced computer-aided drug design, and cell-free in vitro transcription/translation systems, for the discovery of novel ribosome-targeting antibiotics. Thus, in this paper, we overview the research on different aspects of bacterial ribosomes, especially focus on discussing the challenges in the discovery of ribosome-targeting antibacterial drugs and advances made to address issues such as drug-resistance and selectivity, which, we believe, provide perspectives for the discovery of novel antibiotics.

Red Blood Cell Membrane-Camouflaged Tedizolid Phosphate-Loaded PLGA Nanoparticles for Bacterial-Infection Therapy

Multiple drug resistance (MDR) in bacterial infections is developed with the abuse of antibiotics, posing a severe threat to global health. Tedizolid phosphate (TR-701) is an efficient prodrug of tedizolid (TR-700) against gram-positive bacteria, including methicillin-sensitive staphylococcus aureus (MSSA) and methicillin-resistant staphylococcus aureus (MRSA). Herein, a novel drug delivery system: Red blood cell membrane (RBCM) coated TR-701-loaded polylactic acid-glycolic acid copolymer (PLGA) nanoparticles (RBCM-PLGA-TR-701NPs, RPTR-701Ns) was proposed. The RPTR-701Ns possessed a double-layer core-shell structure with 192.50 ± 5.85 nm in size, an average encapsulation efficiency of 36.63% and a 48 h-sustained release in vitro. Superior bio-compatibility was confirmed with red blood cells (RBCs) and HEK 293 cells. Due to the RBCM coating, RPTR-701Ns on one hand significantly reduced phagocytosis by RAW 264.7 cells as compared to PTR-701Ns, showing an immune escape effect. On the other hand, RPTR-701Ns had an advanced exotoxins neutralization ability, which helped reduce the damage of MRSA exotoxins to RBCs by 17.13%. Furthermore, excellent in vivo bacteria elimination and promoted wound healing were observed of RPTR-701Ns with a MRSA-infected mice model without causing toxicity. In summary, the novel delivery system provides a synergistic antibacterial treatment of both sustained release and bacterial toxins absorption, facilitating the incorporation of TR-701 into modern nanotechnology.

Long-Term Use of Tedizolid in Osteoarticular Infections: Benefits among Oxazolidinone Drugs

Background: To evaluate the efficacy and safety of long-term use of tedizolid in osteoarticular infections. Methods: Multicentric retrospective study (January 2017–March 2019) of osteoarticular infection cases treated with tedizolid. Failure: clinical worsening despite antibiotic treatment or the need of suppressive treatment. Results: Cases (n = 51; 59% women, mean age of 65 years) included osteoarthritis (n = 27, 53%), prosthetic joint infection (n = 17, 33.3%), and diabetic foot infections (n = 9, 18%); where, 59% were orthopedic device-related. Most frequent isolates were Staphylococcus spp. (65%, n = 47; S. aureus, 48%). Reasons for choosing tedizolid were potential drug-drug interaction (63%) and cytopenia (55%); median treatment duration was 29 days (interquartile range -IQR- 15–44), 24% received rifampicin (600 mg once daily) concomitantly, and adverse events were scarce (n = 3). Hemoglobin and platelet count stayed stable throughout treatment (from 108.6 g/L to 116.3 g/L, p = 0.079; and 240 × 10⁹/L to 239 × 10⁹/L, p = 0.942, respectively), also in the subgroup of cases with cytopenia. Among device-related infections, 33% were managed with implant retention. Median follow-up was 630 days and overall cure rate 83%; among failures (n = 8), 63% were device-related infections. Conclusions: Long-term use of tedizolid was effective, showing a better safety profile with less myelotoxicity and lower drug-drug interaction than linezolid. Confirmation of these advantages could make tedizolid the oxazolidinone of choice for most of osteoarticular infections.

Safety and Tolerability of More than Six Days of Tedizolid Treatment

Tedizolid has demonstrated its efficacy and safety in clinical trials; however, data concerning its tolerability in long-term treatments are scarce. The aim of the study was to assess the indications and to describe the long-term safety profile of tedizolid. A multicentric retrospective study of patients who received tedizolid for more than 6 days was conducted. Adverse events (AEs) were identified from patients' medical records and laboratory data. The World Health Organization causality categories were used to discern AEs that were probably associated with tedizolid. Eighty-one patients, treated with tedizolid 200 mg once daily for a median (interquartile range [IQR]) duration of 28 (14 to 59) days, were included; 36 (44.4%) had previously received linezolid. The most common reasons for selecting tedizolid were to avoid linezolid potential toxicities or interactions (53.1%) or due to previous linezolid-related toxicities (27.2%). The most common indications were off-label, including prosthetic joint infections, osteomyelitis, and respiratory infections (77.8%). Overall, 9/81 patients (11.1%) experienced a probably associated AE. Two patients (2.5%) developed gastrointestinal disorders, 1 (1.2%) developed anemia, and 6 developed thrombocytopenia (7.4%) after a median (IQR) duration of treatment of 26.5 (17 to 58.5) days. Four (5%) patients discontinued tedizolid due to AEs. Among 23 patients with chronic renal failure (CRF), the rate of myelotoxicity was 17.4%, and only 8.7% had to stop tedizolid; 20 out of 22 with previous linezolid-associated toxicity had no AE. Long-term tedizolid treatments had good tolerance with rates of gastrointestinal AE and hematological toxicity lower than those reported with linezolid, particularly in patients with CRF and in those with a history of linezolid-associated toxicity.

Current role of oxazolidinones and lipoglycopeptides in skin and soft tissue infections

PURPOSE OF REVIEW

An increase of skin and soft tissue infections involving Staphylococcus aureus has been reported in community and hospital settings. Methicillin resistance in S. aureus is associated with treatment failure and increased mortality. Recently, new antimicrobials with enhanced activity against methicillin-resistant Staph. aureus have been approved for the treatment of skin and soft tissue infections. Among these, novel oxazolidinones and lipoglycopeptides represent options with favorable pharmacokinetic characteristics and safety profiles.

RECENT FINDINGS

Newly approved compounds include tedizolid, characterized by the availability of both oral and intravenous formulation and once daily administration and dalbavancin, a long-acting antimicrobial allowing for weekly administration. These new molecules present advantages, such as enhanced activity against multidrug-resistant Gram-positive bacteria and favorable safety profiles.

SUMMARY

We have reviewed the pharmacokinetic characteristics and the implications for use in skin and soft tissue infections of tedizolid and dalbavancin. Advantages associated with the use of these compounds include the possibility for early patient discharge, reduced hospital length of stay, and outpatient treatment, with potential impact on morbidity, mortality, and overall health-care costs.

Calculated initial parenteral treatment of bacterial infections: Safety and tolerabilty

This is the fourth chapter of the guideline "Calculated initial parenteral treatment of bacterial infections in adults - update 2018" in the 2nd updated version. The German guideline by the Paul-Ehrlich-Gesellschaft für Chemotherapie e.V. (PEG) has been translated to address an international audience. Safety and tolerability of antimicrobial agents will be discussed in this chapter. Toxic, allergic and biological effects can be differentiated on the basis of their pathogenesis. The question of differences in the tolerability of specific antibiotics is of particular importance. However, due to limitations of the available data, it cannot be answered for most agents with the desired accuracy. For an assessment of rare side effects, results from the postmarketing surveillance have to be used.

In vitro evaluation of the antibacterial activities of radezolid and linezolid for Streptococcus agalactiae

PURPOSE

This study aims to evaluate the antimicrobial activities of linezolid and radezolid against Streptococcus agalactiae in vitro and compared for genetic resistance factors.

METHOD

Nonduplicate S. agalactiae clinical isolates (n = 136) were collected and the minimal inhibitory concentrations of antimicrobials were determined by agar dilution methodology. The linezolid-resistant mechanism in the clinical linezolid-non-susceptible S. agalactiae isolates and that induced by linezolid pressure in vitro were analyzed by PCR and sequence alignment. Antimicrobial activities and resistance mechanism distinctions between linezolid and radezolid were further investigated in the clinical linezolid-non-susceptible S. agalactiae isolates and that induced by linezolid pressure in vitro.

RESULTS

Our data indicated that 17 (13%) of the 136 clinical S. agalactiae isolates were not susceptible to linezolid. For individual S. agalactiae isolates, including linezolid-nonsusceptible isolates with 23S rRNA V domain mutations, radezolid MIC₉₀ values were generally one-half to one-quarter of the linezolid MIC₉₀ values. Radezolid MICs remained low relative to linezolid MICs among linezolid-resistant S. agalactiae isolates, but exhibited the synchronous increases with the increasing copy numbers of 23S rRNA V domain mutations. Overall, 13 optrA-carrying clinical S. agalactiae isolates were found in this study and their MICs all remained sensitive to both linezolid and radezolid. Clinical S. agalactiae isolates with high radezolid MICs showed clonality clustering to sequence type (ST)10.

CONCLUSION

Radezolid exhibits stronger potency against S. agalactiae than linezolid and there is a concerning presence of linezolid-nonsusceptible S. agalactiae in clinical samples.

Linezolid pharmacokinetics in MDR-TB: a systematic review, meta-analysis and Monte Carlo simulation

Objectives

The oxazolidinone linezolid is an effective component of drug-resistant TB treatment, but its use is limited by toxicity and the optimum dose is uncertain. Current strategies are not informed by clinical pharmacokinetic (PK)/pharmacodynamic (PD) data; we aimed to address this gap.

Methods

We defined linezolid PK/PD targets for efficacy (fAUC_0–24:MIC >119 mg/L/h) and safety (fC_min <1.38 mg/L). We extracted individual-level linezolid PK data from existing studies on TB patients and performed meta-analysis, producing summary estimates of fAUC_0–24 and fC_min for published doses. Combining these with a published MIC distribution, we performed Monte Carlo simulations of target attainment.

Results

The efficacy target was attained in all simulated individuals at 300 mg q12h and 600 mg q12h, but only 20.7% missed the safety target at 300 mg q12h versus 98.5% at 600 mg q12h. Although suggesting 300 mg q12h should be used preferentially, these data were reliant on a single centre. Efficacy and safety targets were missed by 41.0% and 24.2%, respectively, at 300 mg q24h and by 44.6% and 27.5%, respectively, at 600 mg q24h. However, the confounding effect of between-study heterogeneity on target attainment for q24h regimens was considerable.

Conclusions

Linezolid dosing at 300 mg q12h may retain the efficacy of the 600 mg q12h licensed dosing with improved safety. Data to evaluate commonly used 300 mg q24h and 600 mg q24h doses are limited. Comprehensive, prospectively obtained PK/PD data for linezolid doses in drug-resistant TB treatment are required.

Novel Antibiotics for Multidrug-Resistant Gram-Positive Microorganisms

Increasing multidrug-resistance to Gram-positive pathogens, particularly to staphylococci, enterococci and streptococci, is a major problem, resulting in significant morbidity, mortality and healthcare costs. In recent years, only a small number of novel antibiotics effective against Gram-positive bacteria has been approved. This review will discuss the current evidence for novel branded antibiotics that are highly effective in the treatment of multidrug-resistant infections by Gram-positive pathogens, namely ceftobiprole, ceftaroline, telavancin, oritavancin, dalbavancin, tedizolid, besifloxacin, delafloxacin, ozenoxacin, and omadacycline. The mechanism of action, pharmacokinetics, microbiological spectrum, efficacy and safety profile will be concisely presented. As for any emerging antibiotic agent, resistance is likely to develop against these highly effective antibiotics. Only through appropriate dosing, utilization and careful resistance development monitoring will these novel antibiotics continue to treat Gram-positive pathogens in the future.

An overview of new antitubercular drugs, drug candidates, and their targets

The causative agent of tuberculosis (TB), Mycobacterium tuberculosis and more recently totally drug-resistant strains of M. tuberculosis, display unique mechanisms to survive in the host. A four-drug treatment regimen was introduced 40 years ago but the emergence of multidrug-resistance and more recently TDR necessitates the identification of new targets and drugs for the cure of M. tuberculosis infection. The current efforts in the drug development process are insufficient to completely eradicate the TB epidemic. For almost five decades the TB drug development process remained stagnant. The last 10 years have made sudden progress giving some new and highly promising drugs including bedaquiline, delamanid, and pretomanid. Many of the candidates are repurposed compounds, which were developed to treat other infections but later, exhibited anti-TB properties also. Each class of drug has a specific target and a definite mode of action. These targets are either involved in cell wall biosynthesis, protein synthesis, DNA/RNA synthesis, or metabolism. This review discusses recent progress in the discovery of newly developed and Food and Drug Administration approved drugs as well as repurposed drugs, their targets, mode of action, drug-target interactions, and their structure-activity relationship.

Population Pharmacokinetics and Dosing Optimization of Linezolid in Pediatric Patients

Linezolid is a synthetic antibiotic very effective in the treatment of infections caused by Gram-positive pathogens. Although the clinical application of linezolid in children has increased progressively, data on linezolid pharmacokinetics in pediatric patients are very limited. The aim of this study was to develop a population pharmacokinetic model for linezolid in children and optimize the dosing strategy in order to improve therapeutic efficacy. We performed a prospective pharmacokinetic study of pediatric patients aged 0 to 12 years. The population pharmacokinetic model was developed using the NONMEM program. Goodness-of-fit plots, nonparametric bootstrap analysis, normalized prediction distribution errors, and a visual predictive check were employed to evaluate the final model. The dosing regimen was optimized based on the final model. The pharmacokinetic data from 112 pediatric patients ages 0.03 to 11.9 years were analyzed. The pharmacokinetics could best be described by a one-compartment model with first-order elimination along with body weight and the estimated glomerular filtration rate as significant covariates. Simulations demonstrated that the currently approved dosage of 10 mg/kg of body weight every 8 h (q8h) would lead to a high risk of underdosing for children in the presence of bacteria with MICs of ≥2 mg/liter. To reach the pharmacokinetic target, an elevated dosage of 15 or 20 mg/kg q8h may be required for them. The population pharmacokinetics of linezolid were characterized in pediatric patients, and simulations provide an evidence-based approach for linezolid dosage individualization.

Potential Drug-Drug Interactions with Antimicrobials in Hospitalized Patients: A Multicenter Point-Prevalence Study

Background

Improper use of antimicrobials can cause adverse drug events and high costs. The purpose of this study was to investigate the frequency and potential drug–drug interactions associated with antimicrobials among hospitalized patients.

Material/Methods

This study was conducted on the same day in 5 different hospitals in Turkey. We included patients aged ≥18 years who received at least 1 antimicrobial drug and at least 1 of any other drug. The Micromedex^® online drug reference system was used to control and describe the interactions. Drug interactions were classified as contraindicated, major, moderate, and minor.

Results

Potential drug–drug interactions with antimicrobials were 26.4% of all interactions. Five (42%) of 12 contraindicated interactions and 61 (38%) of 159 major interactions were with antimicrobials. Quinolones, triazoles, metronidazole, linezolid, and clarithromycin accounted for 173 (25.7%) of 673 prescribed antimicrobials, but were responsible for 141 (92.1%) of 153 interactions. In multivariate analysis, number of prescribed antimicrobials (odds ratio: 2.3001, 95% CI: 1.6237–3.2582), number of prescribed drugs (odds ratio: 1.2008, 95% CI: 1.0943–1.3177), and hospitalization in the university hospital (odds ratio: 1.7798, 95% CI: 1.0035–3.1564) were independent risk factors for developing drug interactions.

Conclusions

Due to risk of drug interactions, physicians should be more cautious when prescribing antimicrobials, particularly when prescribing quinolones, linezolid, azoles, metronidazole, and macrolides.

Novel therapeutic approaches of natural oil from black seeds and its underlying mechanisms against kidney dysfunctions in haloperidol-induced male rats

BACKGROUND

Antipsychotic drugs could be nephrotoxic in schizophrenia patients.

METHODS

The present study investigated the protective effect of oil from black seed on kidney dysfunctions using several biological approaches in adult rats. The animals were divided into six groups (n=10): normal control rats; haloperidol (HAL)-induced rats: induced rats were pre-, co- and post-treated with black seed oil (BSO), respectively, and the last group was treated with the oil only. The treatment was done through oral administration, and the experiment lasted 14 days.

RESULTS

Therapeutic administration of HAL to rats caused reduction in both enzymatic and non-enzymatic proteins mediated by stable OH˙ and DPPH free radicals. K+, Na+ and MDA contents as well as 51 nucleotidase, aldose-reductase activities were increased with corresponding decrease in the activity of lactate dehydrogenase (LDH) in HAL-induced toxicity rats. Contrariwise, differential treatments with BSO prevented and reversed the nephrotoxicity by depleting K+, Na+, MDA contents and aldose-reductase activity, and AMP hydrolysis with increased adenosine triphosphate (ATP) in the PMFs of rat kidney. The cytotoxicity of HAL elicited on both inner renal cortex and outer medulla was equally alleviated by combined active molecules of oil from black seed (OBS). However, pre-, co- and post-treatment demonstrate significant approaches in averting nephrotoxicity of neuroleptic drug (HAL) via several biological mechanisms.

CONCLUSIONS

This study therefore validates the use of black seed oil as therapy particularly for individuals with renal dysfunctions.

Epididymo-orchitis caused by enteric organisms in men > 35 years old: beyond fluoroquinolones

Epididymo-orchitis is a common urological condition in men of all ages, causing a unilateral or bilateral swelling of the epididymis and/or testis. It is frequently caused by sexually transmitted infections, Chlamydia trachomatis and Neisseria gonorrheae, as well as common enteric organisms implicated in urinary tract infections. Men over 35 years old may develop epididymo-orchitis associated with enteric organisms, often associated with functional bladder outlet problems such as benign prostatic hyperplasia or urethral stricture disease. Fluoroquinolones, especially ciprofloxacin, have long been the mainstay of treatment for these infections; however, rising resistance to ciprofloxacin in E. coli isolates in Europe and the USA means that there is an unprecedented necessity for alternative antimicrobials with adequate penetration into genital tissues (epididymis and testes) to allow appropriate and comprehensive treatment of epididymo-orchitis in this group of patients.

Variable Linezolid Exposure in Intensive Care Unit Patients-Possible Role of Drug-Drug Interactions

BACKGROUND

Standard doses of linezolid may not be suitable for all patient groups. Intensive care unit (ICU) patients in particular may be at risk of inadequate concentrations. This study investigated variability of drug exposure and its potential sources in this population.

METHODS

Plasma concentrations of linezolid were determined by high-performance liquid chromatography in a convenience sample of 20 ICU patients treated with intravenous linezolid 600 mg twice daily. Ultrafiltration applying physiological conditions (pH 7.4/37°C) was used to determine the unbound fraction. Individual pharmacokinetic (PK) parameters were estimated by population PK modeling. As measures of exposure to linezolid, area under the concentration-time curve (AUC) and trough concentrations (Cmin) were calculated and compared with published therapeutic ranges (AUC 200-400 mg*h/L, Cmin 2-10 mg/L). Coadministered inhibitors or inducers of cytochrome P450 and/or P-glycoprotein were noted.

RESULTS

Data from 18 patients were included into the PK evaluation. Drug exposure was highly variable (median, range: AUC 185, 48-618 mg*h/L, calculated Cmin 2.92, 0.0062-18.9 mg/L), and only a minority of patients had values within the target ranges (6 and 7, respectively). AUC and Cmin were linearly correlated (R = 0.98), and classification of patients (underexposed/within therapeutic range/overexposed) according to AUC or Cmin was concordant in 15 cases. Coadministration of inhibitors was associated with a trend to higher drug exposure, whereas 3 patients treated with levothyroxine showed exceedingly low drug exposure (AUC ∼60 mg*h/L, Cmin <0.4 mg/L). The median unbound fraction in all 20 patients was 90.9%.

CONCLUSIONS

Drug exposure after standard doses of linezolid is highly variable and difficult to predict in ICU patients, and therapeutic drug monitoring seems advisable. PK drug-drug interactions might partly be responsible and should be further investigated; protein binding appears to be stable and irrelevant.