Omadacycline for Community-Acquired Bacterial Pneumonia

Efficacies of omadacycline + amikacin + imipenem and an all-oral regimen omadacycline + clofazimine + linezolid in a mouse model of M. abscessus lung disease

Treatment outcomes for Mycobacteroides abscessus (Mab, also known as Mycobacterium abscessus) disease are still unsatisfactory, mainly due to issues with drug toxicity, tolerability, and efficacy. Treating Mab disease is challenging due to its high baseline antibiotic resistance, initial requirement for intravenous therapy, and poor medication tolerance. Omadacycline, a new tetracycline, is active against Mab. Since any new antibiotic effective against Mab is expected to be used in combination with other antibiotics, we evaluated the efficacy of two triple-drug combinations comprising omadacycline, omadacycline + amikacin + imipenem, and omadacycline + clofazimine + linezolid against two contemporary Mab clinical isolates in a mouse model of Mab lung disease. Antibiotic administration was initiated 1-week post-infection and was given daily, with Mab burden in the lungs at treatment completion serving as the endpoint. Omadacycline alone moderately reduced Mab levels and maintained better health in mice compared to untreated ones, which typically suffered from the infection. The omadacycline + clofazimine + linezolid combination showed immediate bactericidal activity and enhanced efficacy over 6 weeks, particularly against the more resistant strain (M9507). However, the clofazimine + linezolid combination lacked early bactericidal activity. When combined with amikacin and imipenem, omadacycline did not improve the regimen's effectiveness over 4 weeks of treatment. Our study showed that omadacycline + clofazimine + linezolid exhibited significant bactericidal activity over an extended treatment duration. However, adding omadacycline to amikacin and imipenem did not improve regimen effectiveness against the evaluated clinical isolates within 4 weeks. Further research in Mab disease patients is needed to determine the most effective omadacycline-containing regimen.IMPORTANCEMycobacteroides abscessus is a common environmental bacterium that causes infections in people with compromised lung function, including those with bronchiectasis, cystic fibrosis, chronic obstructive pulmonary disease, and weakened immune systems, especially among older individuals. Treating M. abscessus disease is challenging due to the limited effectiveness and toxicity of current antibiotics, which often require prolonged use. Omadacycline, a new antibiotic, shows promise against M. abscessus. Using a mouse model that mimics M. abscessus disease in humans, we studied the effectiveness of including omadacycline with recommended antibiotics. Adding omadacycline to clofazimine and linezolid significantly improved treatment outcomes, rapidly clearing the bacteria from the lungs and maintaining effectiveness throughout. This oral combination is convenient for patients. However, adding omadacycline to amikacin and imipenem did not improve treatment effectiveness within 4 weeks. Further study with M. abscessus patients is necessary to optimize omadacycline-based treatment strategies for this disease.

Current and novel therapies for management of Acinetobacter baumannii-associated pneumonia

Acinetobacter baumannii is a common pathogen associated with hospital-acquired pneumonia showing increased resistance to carbapenem and colistin antibiotics nowadays. Infections with A. baumannii cause high patient fatalities due to their capability to evade current antimicrobial therapies, emphasizing the urgency of developing viable therapeutics to treat A. baumannii-associated pneumonia. In this review, we explore current and novel therapeutic options for overcoming therapeutic failure when dealing with A. baumannii-associated pneumonia. Among them, antibiotic combination therapy administering several drugs simultaneously or alternately, is one promising approach for optimizing therapeutic success. However, it has been associated with inconsistent and inconclusive therapeutic outcomes across different studies. Therefore, it is critical to undertake additional clinical trials to ascertain the clinical effectiveness of different antibiotic combinations. We also discuss the prospective roles of novel antimicrobial therapies including antimicrobial peptides, bacteriophage-based therapy, repurposed drugs, naturally-occurring compounds, nanoparticle-based therapy, anti-virulence strategies, immunotherapy, photodynamic and sonodynamic therapy, for utilizing them as additional alternative therapy while tackling A. baumannii-associated pneumonia. Importantly, these innovative therapies further require pharmacokinetic and pharmacodynamic evaluation for safety, stability, immunogenicity, toxicity, and tolerability before they can be clinically approved as an alternative rescue therapy for A. baumannii-associated pulmonary infections.

A near-infrared broad-spectrum antimicrobial nanoplatform powered by bacterial metabolic activity for enhanced antimicrobial photodynamic-immune therapy

The emergence of antimicrobial-resistant bacterial infections poses a significant threat to public health, necessitating the development of innovative and effective alternatives to antibiotics. Photodynamic therapy (PDT) and immunotherapy show promise in combating bacteria. However, PDT's effectiveness is hindered by its low specificity to bacteria, while immunotherapy struggles to eliminate bacteria in immunosuppressive environments. In this work, we introduce an innovative near-infrared antimicrobial nanoplatform (ZFC) driven by bacterial metabolism. ZFC, comprising d-cysteine-functionalized pentafluorophenyl bacteriochlorin (FBC-Cy) coordinated with Zn2+, is designed for antimicrobial photodynamic-immune therapy (aPIT) against systemic bacterial infections. By specifically targeting bacteria via d-amino acid incorporation into bacterial surface peptidoglycans during metabolism, ZFC achieves precise bacterial clearance in wound and pulmonary infections, exhibiting an antimicrobial efficacy of up to 90 % with minimal damage to normal cells under 750 nm light. Additionally, ZFC enhances the activation of antigen-presenting cells by 3.2-fold compared to control groups. Furthermore, aPIT induced by ZFC triggers systemic immune responses and establishes immune memory, resulting in a 1.84-fold increase in antibody expression against bacterial infections throughout the body of mice. In conclusion, aPIT prompted by ZFC presents a approach to treating bacterial infections, offering a broad-spectrum solution for systemic bacterial infections. STATEMENT OF SIGNIFICANCE: The new concept demonstrated focuses on an innovative near-infrared antimicrobial nanoplatform (ZFC) for antimicrobial photodynamic-immune therapy (aPIT), highlighting its reliance on bacterial metabolism and its non-damaging effect on normal tissues. ZFC efficiently targets deep-tissue bacterial infections by harnessing bacterial metabolism, thereby enhancing therapeutic efficacy while sparing normal tissues from harm. This approach not only clears bacterial infections effectively but also induces potent adaptive immune responses, leading to the eradication of distant bacterial infections. By emphasizing ZFC's unique mechanism driven by bacterial metabolism and its tissue-sparing properties, this work underscores the potential for groundbreaking advancements in antimicrobial therapy. Such advancements hold promise for minimizing collateral damage to healthy tissues, thereby improving treatment outcomes and mitigating the threat of antimicrobial resistance. This integrated approach represents a significant progress forward in the development of next-generation antimicrobial therapies with enhanced precision and efficacy.

Pharmacotherapies for multidrug-resistant gram-positive infections: current options and beyond

INTRODUCTION

Infections due to multidrug-resistant organisms (MDRO) are a serious concern for public health with high morbidity and mortality. Though many antibiotics have been introduced to manage these infections, there are remaining concerns regarding the optimal management of Gram-positive MDROs.

AREAS COVERED

A literature search on the PubMed/Medline database was conducted. We applied no language and time limits for the search strategy. In this narrative review, we discuss the current options for managing Gram-positive MDROs as well as non-traditional antibacterial agents in development.

EXPERT OPINION

Despite their introduction more than 70 years ago, glycopeptides are still the cornerstone in treating Gram-positive infections: all registrative studies of new antibiotics have glycopeptides as control; these studies are designed as not inferior studies, therefore it is almost impossible to give recommendations other than the use of glycopeptides in the treatment of Gram-positive infections. The best evidence on treatments different from glycopeptides comes from post-hoc analysis and meta-analysis. Non-traditional antibacterial agents are being studied to aid in short and effective antibiotic therapies. The use of non-traditional antibacterial agents is not restricted to replacing traditional antibacterial agents with alternative therapies; instead, they should be used in combination with antibiotic therapies.

Staphylococcus aureus Pneumonia in Can Tho, Vietnam: Clinical Characteristics, Antimicrobial Resistance Profile and Risk Factors of Mortality

INTRODUCTION

Staphylococcus aureus (S. aureus) is an important pathogen in both community-acquired and hospital-acquired pneumonia. S. aureus pneumonia has a high mortality rate and serious complications. Resistance to multiple antibiotics is a major challenge in the treatment of S. aureus pneumonia. Understanding the antibiotic resistance profile of S. aureus and the risk factors for mortality can help optimize antibiotic regimens and improve patient outcomes in S. aureus pneumonia.

METHODS

A prospective cohort study of 118 patients diagnosed with S. aureus pneumonia between May 2021 and June 2023 was conducted, with a 30-day follow-up period. Demographic information, comorbidities, Charlson Comorbidity Index, clinical characteristics, outcomes, and complications were collected for each enrolled case. The data were processed and analyzed using R version 3.6.2.

RESULTS

S. aureus pneumonia has a 30-day mortality rate of approximately 50%, with complication rates of 22% for acute respiratory distress syndrome (ARDS), 26.3% for septic shock, and 14.4% for acute kidney injury (AKI). Among patients with methicillin-resistant S. aureus (MRSA) pneumonia treated with vancomycin (n = 40), those with a vancomycin minimum inhibitory concentration (MIC) ≤ 1 had significantly higher cumulative survival at day 30 compared to those with MIC ≥ 2 (log-rank test p = 0.04). The prevalence of MRSA among S. aureus isolates was 84.7%. Hemoptysis, methicillin resistance, acidosis (pH < 7.35), and meeting the Infectious Diseases Society of America/American Thoracic Society (IDSA/ATS) criteria for severe pneumonia were significantly associated with mortality in a multivariate Cox regression model based on the adaptive least absolute shrinkage and selection operator (LASSO).

CONCLUSIONS

S. aureus pneumonia is a severe clinical condition with high mortality and complication rates. MRSA has a high prevalence in Can Tho City, Vietnam. Hemoptysis, methicillin resistance, acidosis (pH < 7.35), and meeting the IDSA/ATS criteria for severe pneumonia are risk factors for mortality in S. aureus pneumonia.

Efficacy of omadacycline in the treatment of Legionella pneumonia: a case report

Legionella, one of the main pathogens that causes community-acquired pneumonia, can lead to Legionella pneumonia, a condition characterized predominantly by severe pneumonia. This disease, caused by the bacterium Legionella pneumophila, can quickly progress to critical pneumonia and is often associated with damage to multiple organs. As a result, it requires close attention in terms of clinical diagnosis and treatment. Omadacycline, a new type of tetracycline derivative belonging to the aminomethylcycline class of antibiotics, is a semi-synthetic compound derived from minocycline. Its key structural feature, the aminomethyl modification, allows omadacycline to overcome bacterial resistance and broadens its range of effectiveness against bacteria. Clinical studies have demonstrated that omadacycline is not metabolized in the body, and patients with hepatic and renal dysfunction do not need to adjust their dosage. This paper reports a case of successful treatment of Legionella pneumonia with omadacycline in a patient who initially did not respond to empirical treatment with moxifloxacin. The patient also experienced electrolyte disturbance, as well as dysfunction in the liver and kidneys, delirium, and other related psychiatric symptoms.

A Review of Omadacycline for Potential Utility in the Military Health System for the Treatment of Wound Infections

INTRODUCTION

Combat-related wound infections complicate the recovery of wounded military personnel, contributing to overall morbidity and mortality. Wound infections in combat settings present unique challenges because of the size and depth of the wounds, the need to administer emergency care in the field, and the need for subsequent treatment in military facilities. Given the increase in multidrug-resistant pathogens, a novel, broad-spectrum antibiotic is desired across this continuum of care when the standard of care fails. Omadacycline was FDA-approved in 2018 for treatment of adults with acute bacterial skin and skin structure infections (ABSSSI), as well as community-acquired bacterial pneumonia (CABP). It is a broad-spectrum antibiotic with activity against gram-positive, gram-negative, and atypical bacterial pathogens, including multidrug-resistant species. Omadacycline can overcome commonly reported tetracycline resistance mechanisms, ribosomal protection proteins, and efflux pumps, and is available in once-daily intravenous or oral formulations. In this review, we discuss the potential role of omadacycline, which is included in the Department of Defense Formulary, in the context of combat wound infections.

MATERIALS AND METHODS

A literature review was undertaken for manuscripts published before July 21, 2023. This included a series of publications found via PubMed and a bibliography made publicly available on the Paratek Pharmaceuticals, Inc. website. Publications presenting primary data published in English on omadacycline in relation to ESKAPEE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli, and Enterobacter species) pathogens and Clostridioides difficile, including in vitro, in vivo, and clinical data were included.

RESULTS

Of 260 identified records, 66 were included for evidence review. Omadacycline has in vitro activity against almost all the ESKAPEE pathogens, apart from P. aeruginosa. Importantly, it has activity against the four most prevalent bacterial pathogens that cause wound infections in the military healthcare system: S. aureus, including methicillin-resistant S. aureus, A. baumannii, K. pneumoniae, and E. coli. In vivo studies in rats have shown that omadacycline is rapidly distributed in most tissues, with the highest tissue-to-blood concentration ratios in bone mineral. The clinical efficacy of omadacycline has been assessed in three separate Phase 3 studies in patients with ABSSSI (OASIS-1 and OASIS-2) and with CABP (OPTIC). Overall, omadacycline has an established safety profile in the treatment of both ABSSSI and CABP.

CONCLUSIONS

Omadacycline has broad-spectrum activity, the option to be orally administered and an established safety profile, making it a potentially attractive replacement for moxifloxacin in the military individual first aid kit, especially when accounting for the increasing resistance to fluoroquinolones. Further studies and clinical evaluation are warranted to support broader use of omadacycline to treat combat wound infections in the military healthcare system.

Development, validation, and clinical application of a UPLC-MS/MS method for omadacycline determination in human serum

BACKGROUND

Omadacycline is the first aminomethyl-tetracycline variety to successfully enter clinical applications. To support regular therapeutic drug monitoring (TDM) in clinical practice, an ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method was developed that would allow omadacycline quantification in human serum.

METHODS

Proteins were precipitated from serum samples using methanol. Tigecycline was used as the internal standard. Mobile phase A was formic acid in water (0.1% v/v) and mobile phase B was methanol. UPLC-MS/MS was performed for analyte separation using a gradient elution program at a flow rate of 0.3 mL/min and a total run time of 5 min. The chromatography column was a ZORBAX PRHD SB-Aq (3 × 50 mm, 1.8 μm, Agilent, USA). The multiple reaction monitoring transitions at m/z = 557.4/470.3 and 586.5/513.3 were selected for omadacycline and tigecycline in the positive mode, respectively.

RESULTS

The validated curve ranges were 0.5-25.0 μg/mL. This method exhibited acceptable selectivity, matrix effects, and recovery. The inter- and intra-run accuracies ranged from 93.5% to 114.8%, and the inter- and intra-run precisions were between 1.29% and 5.55%.

CONCLUSIONS

The LC-MS/MS method provided a simple, specific, and rapid quantification of omadacycline in the serum of patients with pulmonary infection.

Evaluation of omadacycline regimens for community-acquired bacterial pneumonia patients infected with Staphylococcus Aureus by pharmacokinetic/pharmacodynamic analysis

Omadacycline is an FDA-approved agent for community-acquired bacterial pneumonia (CABP). The purpose of this study is to evaluate the effectiveness of omadacycline for treating CABP patients infected with Staphylococcus aureus, including Methicillin-Resistant Staphylococcus aureus (MRSA) and Methicillin-Susceptible Staphylococcus aureus (MSSA), using pharmacokinetic/pharmacodynamic (PK/PD) analysis. Monte Carlo simulations (MCSs) were performed by utilizing omadacycline pharmacokinetic (PK) parameters, minimum inhibitory concentration (MIC) data, and in vivo PK/PD targets to calculate the probability of target attainment (PTA) and cumulative fraction of response (CFR) values for different dose regimens against MRSA and MSSA in CABP patients. A dosage regimen with a PTA or CFR expectation value greater than 90% was considered optimal. For all recommended dose regimens, PTA values for MRSA MIC ≤1 and MSSA MIC ≤4 on days 1, 4, and 7 were greater than 90%. Based on the MIC distribution of Staphylococcus aureus, all dose regimens had CFR values greater than 90% for both MRSA and MSSA. CFR values for different bacterial strains were still greater than 90% within the range of PK/PD target values less than 40, although they gradually decreased with increasing PK/PD target values. PK/PD modeling demonstrated that all recommended dose regimens of omadacycline are highly effective against CABP patients infected with MRSA and MSSA. The study provides theoretical support for the efficacy of omadacycline in different dose regimens.

Clarithromycin for early anti-inflammatory responses in community-acquired pneumonia in Greece (ACCESS): a randomised, double-blind, placebo-controlled trial

BACKGROUND

Addition of macrolide antibiotics to β-lactam antibiotics for the treatment of patients in hospital with community-acquired pneumonia is based on results from observational studies and meta-analyses rather than randomised clinical trials. We investigated if addition of the macrolide clarithromycin to treatment with a β-lactam antibiotic in this population could improve early clinical response-the new regulatory endpoint for community-acquired pneumonia-and explored the possible contribution of modulation of the inflammatory host response to that outcome.

METHODS

The ACCESS trial was a phase 3 prospective, double-blind, randomised controlled trial, in which adults in hospital with community-acquired pneumonia who had systemic inflammatory response syndrome, Sequential Organ Failure Assessment (SOFA) score of 2 or more, and procalcitonin 0·25 ng/mL or more were enrolled in 18 internal medicine departments of public Greek hospitals. Patients were randomly assigned (1:1) by computer-generated block randomisation to standard of care medication (including intravenous administration of a third-generation cephalosporin or intravenous administration of β-lactam plus β-lactamase inhibitor combination) plus either oral placebo or oral clarithromycin 500 mg twice daily for 7 days. Investigators, staff, and patients were masked to group allocation. The primary composite endpoint required that patients fulfilled both of the following conditions after 72 hours (ie, day 4 of treatment): (1) decrease in respiratory symptom severity score of 50% or more as an indicator of early clinical response and (2) decrease in SOFA score of at least 30% or favourable procalcitonin kinetics (defined as ≥80% decrease from baseline or procalcitonin <0·25 ng/mL), or both, as an indicator of early inflammatory response. Participants who were randomly assigned and received allocated treatment were included in the primary analysis population. This trial is complete and is registered with the EU Clinical Trials Register (2020-004452-15) and ClinicalTrials.gov (NCT04724044).

FINDINGS

Patients were enrolled between Jan 25, 2021, and April 11, 2023, and 278 individuals were randomly allocated to receive standard of care in combination with either clarithromycin (n=139) or placebo (n=139). 134 patients in the clarithromycin group (five withdrew consent) and 133 patients in the placebo group (six withdrew consent) were included in the analysis of the primary endpoint. The primary endpoint was met in 91 (68%) patients in the clarithromycin group and 51 (38%) patients in the placebo group (difference 29·6% [95% CI 17·7-40·3]; odds ratio [OR] 3·40 [95% CI 2·06-5·63]; p<0·0001). Serious treatment-emergent adverse events (TEAEs) occurred in 58 (43%) patients in the clarithromycin group and 70 (53%) patients in the placebo group (difference 9·4% [95% CI -2·6 to 20·9]; OR 0·67 [95% CI 0·42 to 1·11]; p=0·14). None of the serious TEAEs was judged to be related to treatment assignment.

INTERPRETATION

Addition of clarithromycin to standard of care enhances early clinical response and attenuates the inflammatory burden of community-acquired pneumonia. The mechanism of benefit is associated with changes in the immune response. These findings suggest the importance of adding clarithromycin to β-lactams for treatment of patients in hospital with community-acquired pneumonia to achieve early clinical response and early decrease of the inflammatory burden.

FUNDING

Hellenic Institute for the Study of Sepsis and Abbott Products Operations.

Evaluation of omadacycline dosing regimens in Chinese using population pharmacokinetic-pharmacodynamic analysis

PURPOSE

Omadacycline (PTK-0796) is a first-in-class aminomethylcycline for adult patients with community-acquired bacterial pneumonia (CABP) and acute bacterial skin and skin structure infections (ABSSSI) caused by susceptible pathogens. We investigated the pharmacokinetic (PK) and pharmacodynamic (PD) profile of omadacycline, considering the impact of covariates, particularly ethnicity, on PK and determined the PK/PD cutoff values for dosing regimens.

METHODS

Utilizing nonlinear mixed-effects modeling, we pooled data from 11 clinical trials for PopPK analysis. The first-order conditional estimation with interaction (FOCEI) method in NONMEM facilitated model parameter estimation. Employing a stepwise model selection strategy, with forward addition (P < 0.01) and backward deletion (P < 0.001), we assessed the potential impacts of covariates on omadacycline PK, including baseline age, body weight, sex, race, body mass index, body surface area, baseline albumin, creatine clearance, and formulation. After validating the model through various methods, the final PopPK model underwent Monte Carlo simulations to generate the PK profile for the Chinese population. This enabled AUC calculation and assessment of the probability of target attainment (PTA) and the cumulative fraction of response (CFR) for various dosing regimens and bacterial strains.

RESULTS

Omadacycline's PK can be adequately characterized by a three-compartment model. Body weight, sex, race, and drug formulation statistically influenced its PK. Asians and non-Asians exhibit similar exposure after intravenous infusion, but oral dosing results in much higher exposures than in non-Asians. Monte Carlo simulation indicates that IV-only or IV/PO sequential therapy regimens provide adequate attainment for all major pathogens causing ABSSSI and CABP. PK/PD cutoffs were generally above the MIC90 value of recent clinical isolates from China.

CONCLUSIONS

In conclusion, the approved regimen for China achieved adequate target attainment for all pathogens typically associated with these infections. The higher oral exposure observed in Asians may enhance efficacy without affecting safety or tolerability.

Fluoroquinolone-associated adverse events of interest among hospitalized veterans affairs patients with community-acquired pneumonia who were treated with a fluoroquinolone: A focus on tendonitis, Clostridioides difficile infection, and aortic aneurysm

STUDY OBJECTIVE

The objectives of this study were to (i) quantify the incidence of three concerning fluoroquinolone adverse events of interest (FQAEI, i.e., adverse tendon event (TE), clostridioides difficile infection (CDI), and aortic aneurysm/dissection (AAD)), (ii) identify the patient-level factors that predict these events, and (iii) develop clinical risk scores to estimate the predicted probabilities of each FQAEI based on patient-level covariates available on clinical presentation.

DESIGN

Retrospective cohort study.

SETTING

Upstate New York Veterans' Healthcare Administration from 2011 to 2016.

PATIENTS

Hospitalized patients with community-acquired pneumonia receiving care in the Upstate New York Veterans' Healthcare Administration from 2011 to 2016.

INTERVENTION

N/A.

MEASUREMENTS

The outcomes of interest for this study were the occurrence of TE, CDI, and AAD. We also evaluated a composite of these three outcomes, FQAEI.

MAIN RESULTS

The study population consisted of 1071 patients. The overall incidence of FQAEI, TE, AAD, and CDI was 6.5%, 1.8%, 4.5%, and 0.3%, respectively. For each outcome evaluated, the probability of the event of interest was predicted by the presence of certain comorbidities, previous healthcare exposure, choice of specific FQ antibiotic, or therapy duration. Concomitant steroids, pneumonia in preceding 180 days, and creatinine clearance <30 mL/min predicted FQAEI.

CONCLUSIONS

Individual frequencies of three important FQAEIs were quantified, and risk scores were developed to estimate the probabilities of experiencing these events to help clinicians individualize treatment decisions for patients and reduce the potential risks of select FQAEIs.

Long-term evaluation of clinical success and safety of omadacycline in nontuberculous mycobacteria infections: a retrospective, multicenter cohort of real-world health outcomes

Infections due to nontuberculous mycobacteria (NTM) continue to increase in prevalence, leading to problematic clinical outcomes. Omadacycline (OMC) is an aminomethylcycline antibiotic with FDA orphan drug and fast-track designations for pulmonary NTM infections, including Mycobacteroides abscessus (MAB). This multicenter retrospective study across 16 U.S. medical institutions from January 2020 to March 2023 examined the long-term clinical success, safety, and tolerability of OMC for NTM infections. The cohort included patients aged ≥18 yr, who were clinically evaluable, and` had been treated with OMC for ≥3 mo without a previous diagnosis of cystic fibrosis. The primary outcome was 3 mo clinical success, with secondary outcomes including clinical improvement and mortality at 6- and 12 mo, persistence or reemergence of infection, adverse effects, and reasons for OMC utilization. Seventy-five patients were included in this analysis. Most patients were female (48/75, 64.0%) or Caucasian (58/75, 77.3%), with a median (IQR) age of 59 yr (49-67). Most had NTM pulmonary disease (33/75, 44.0%), skin and soft tissue disease (19/75, 25.3%), or osteomyelitis (10/75, 13.3%), and Mycobacterium abscessus (60/75, 80%) was the most commonly isolated NTM pathogen. The median (IQR) treatment duration was 6 mo (4 - 14), and the most commonly co-administered antibiotic was azithromycin (33/70, 47.1%). Three-month clinical success was observed in 80.0% (60/75) of patients, and AEs attributable to OMC occurred in 32.0% (24/75) of patients, leading to drug discontinuation in 9.3% (7/75).

Advancements in the Management of Severe Community-Acquired Pneumonia: A Comprehensive Narrative Review

Pneumonia, classified as a lower respiratory tract illness, affects different parts of the bronchial system as well as alveoli and can present with varying severities depending on co-morbidities and causative pathogens. It can be broadly classified using the setting in which it was acquired, namely the community or hospital setting, the former being more common and spreading through person-to-person droplet transmission. Community-acquired pneumonia (CAP) is currently the fourth leading cause of death worldwide, and its high mortality makes continual insight into the management of the condition worthwhile. This review explores the literature specifically for severe CAP (sCAP) and delves into the diagnosis, various modalities of treatment, and management of the condition. This condition can be defined as pneumonia requiring mechanical ventilation in the ICU and/or presenting with sepsis and organ failure due to pneumonia. The disease process is characterized by inflammation of the lung parenchyma, initiated by a combination of pathogens and lowered local defenses. Acute diagnosis of the condition is vital in reducing negative patient outcomes, namely through clinical presentation, blood/sputum cultures, imaging modalities such as computed tomography scan, and inflammatory markers, identifying common causative pathogens such as Streptococcus pneumoniae, rhinovirus, Legionella, and viral influenza. Pathogens such as Escherichia coli should also be investigated in patients with chronic obstructive pulmonary disease. The mainstay of treating sCAP includes rapid ICU admission once a diagnosis has been confirmed, initiating sepsis protocol, and treatment with combined empiric antibiotic regimens consisting of beta-lactams and macrolides. Corticosteroid use alongside antibiotics shows promise in reducing inflammation, but its use has to be judged on a case-by-case basis. New drugs such as omadacycline, delafloxacin, and zabofloxacin have shown valid evidence for the treatment of resistant causative organisms. The main guidelines for preventing sCAP include maintaining a healthy lifestyle, and annual pneumococcal and influenza vaccines are recommended for the most vulnerable patient groups, such as those with COPD and immunosuppression.

Case Report: Omadacycline in the treatment of macrolide-unresponsive Mycoplasma pneumoniae pneumonia in an adolescent patient

Omadacycline is a novel tetracycline antibiotic that exhibits good in vitro antibacterial activity against atypical pathogens such as Mycoplasma pneumoniae. It is approved for the treatment of adults with community-acquired bacterial pneumonia. However, the safety and efficacy of omadacycline in pediatric patients under 18 years of age have not yet been established. In the present paper, we report a case of pediatric community-acquired pneumonia in which initial empirical anti-infective therapy had failed. The patient received empirical anti-infective therapy with azithromycin and other antimicrobial agents upon admission but showed a poor clinical response and developed secondary tinnitus and liver dysfunction. After the confirmation of M. pneumoniae infection through metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid, an antibiotic switch to omadacycline was made. Thereafter, the patient's condition improved, and no adverse reactions were observed. These findings demonstrate that mNGS enables the identification of infection-causing pathogens in patients with unresponsive pneumonia. Omadacycline can be considered as an alternative option for anti-infective therapy in pediatric M. pneumoniae pneumonia, especially when the presence of bacterial resistance, adverse drug reactions, or organ failure are taken into consideration.

New Antimicrobials for Gram-Positive Sustained Infections: A Comprehensive Guide for Clinicians

Antibiotic resistance is a public health problem with increasingly alarming data being reported. Gram-positive bacteria are among the protagonists of severe nosocomial and community infections. The objective of this review is to conduct an extensive examination of emerging treatments for Gram-positive infections including ceftobiprole, ceftaroline, dalbavancin, oritavancin, omadacycline, tedizolid, and delafloxacin. From a methodological standpoint, a comprehensive analysis on clinical trials, molecular structure, mechanism of action, microbiological targeting, clinical use, pharmacokinetic/pharmacodynamic features, and potential for therapeutic drug monitoring will be addressed. Each antibiotic paragraph is divided into specialized microbiological, clinical, and pharmacological sections, including detailed and appropriate tables. A better understanding of the latest promising advances in the field of therapeutic options could lead to the development of a better approach in managing antimicrobial therapy for multidrug-resistant Gram-positive pathogens, which increasingly needs to be better stratified and targeted.

The pharmacokinetic evaluation of omadacycline (Oral Only Dosing Regimen) for the treatment of Community-Acquired Bacterial Pneumonia (CABP)

INTRODUCTION

Omadacycline is a new analog of the tetracycline class active against atypical bacteria, as well as against staphylococci, including methicillin-resistant strains, and Streptococcus pneumoniae.

AREAS COVERED

This review has summarized the available clinical evidence on the use of oral omadacycline in the treatment of community-acquired pneumonia (CAP) and described the mechanism of action, pharmacokinetic/pharmacodynamic (PK/PD) parameters in healthy and special populations and the latest research on omadacycline.

EXPERT OPINION

The available clinical evidence on oral omadacycline for the treatment of CAP shows that its properties provide reliable empirical coverage for pathogens such as Haemophilus influenzae, Moraxella catarrhalis, and species of Legionella, Chlamydia, and Mycoplasma. Omadacycline is also active against methicillin-resistant Staphylococcus aureus (MRSA); penicillin-resistant and multidrug-resistant Streptococcus pneumoniae, Streptococcus pyogenes, and Streptococcus agalactiae; and vancomycin-resistant Enterococcus spp. A dose of 450 mg orally once daily is recommended, followed by a maintenance dose of 300 mg orally once daily. Importantly, omadacycline does not require dose adjustment for patients based on BMI, age, gender, or renal or hepatic impairment.

Omadacycline in the treatment of community-acquired bacterial pneumonia in patients with comorbidities: a post-hoc analysis of the phase 3 OPTIC trial

Introduction

The 2019 American Thoracic Society/Infectious Disease Society of America guidelines recommend respiratory fluoroquinolones to treat community-acquired bacterial pneumonia (CABP) in adults with comorbidities. Fluoroquinolones are effective against both typical and atypical pathogens. However, fluoroquinolone treatment has a risk of adverse effects, and the Food and Drug Administration has issued black box safety warnings for their use. Inpatient use of fluoroquinolones has reduced as a result; however, most antibiotic courses are completed as outpatients and discharge prescriptions account for the majority of fluoroquinolone use. As such, a new treatment option is needed to replace fluoroquinolones. Omadacycline is an aminomethylcycline antibiotic with a broad spectrum of activity and is available as a once-daily intravenous or bioequivalent oral formulation.

Methods

This study assessed the safety and clinical efficacy of omadacycline compared with moxifloxacin for the treatment of adult CABP patients with Pneumonia Severity Index (PSI) risk class II/III and ≥1 comorbidity through a post-hoc analysis of the phase 3 OPTIC study (NCT02531438).

Results

In total, 239 omadacycline- and 222 moxifloxacin-treated patients were assessed. The median age was similar between groups (omadacycline: 57 years; moxifloxacin: 58 years), with 26.0% and 26.6%, respectively, ≥65 years of age. Early clinical response was 91.6% for patients with ≥1 comorbidity treated with omadacycline and 91.4% for those treated with moxifloxacin. Post-treatment evaluation results for overall response were 89.1% in the omadacycline group and 87.4% in the moxifloxacin group.

Conclusion

Safety warnings have reduced inpatient use of fluoroquinolones; however, outpatient and discharge prescriptions account for the majority of fluoroquinolone use. Outpatients with comorbidities need an efficacious alternative to fluoroquinolones. Omadacycline maintains the similar efficacy and benefits of fluoroquinolones as a once-daily, monotherapy, bioequivalent oral option with potent in vitro activity against the most common CABP pathogens, including S. pneumoniae and atypical pathogens, but offers a materially different safety profile consistent with its tetracycline heritage. In conclusion, both omadacycline and moxifloxacin exhibited similar efficacy in patients with PSI risk class II/III and comorbidities. Omadacycline fulfills an unmet need as an oral monotherapy treatment option for adult patients with CABP, which will further reduce the use of fluoroquinolones.

Clinical trial registration

https://www.clinicaltrials.gov/study/NCT02531438, identifer: NCT02531438; https://www.clinicaltrialsregister.eu/ctr-search/search?query=2013-004071-13, identifier: EudraCT #2013-004071-13.

Long-term Safety and Tolerability of Omadacycline for the Treatment of Mycobacterium abscessus Infections

Background

Mycobacterium abscessus is a virulent human pathogen. Treatment is complex and often poorly tolerated with suboptimal rates of eradication, highlighting the need for improved therapeutics. This study reports clinical experience with omadacycline for treatment of M abscessus infections at five large nontuberculous mycobacterial (NTM) disease clinics across the United States to better understand long-term safety and tolerability.

Methods

We conducted a multicenter retrospective chart review of adults with M abscessus infections. All patients treated with omadacycline as part of a multidrug therapeutic regimen through December 2021 were included. Clinical data from time of omadacycline initiation and up to 12 months of follow-up were collected. Descriptive statistics were performed.

Results

Analysis included 117 patients. Among patients with M abscessus isolate subspeciation, 58 of 71 (81.7%) were M abscessus spp abscessus. In isolates with reported drug susceptibility testing, 15 of 70 (21.4%) had confirmed susceptibility to macrolides. The most common site of infection was lungs. Median duration omadacycline treatment was 8 months (range, 0.25-33 months; interquartile range, 4-15 months). Omadacycline was discontinued in 60 patients (51.3%); 20 completed planned treatment course, 23 experienced intolerance or adverse event leading to drug cessation, and 17 stopped due to cost, death (unrelated to NTM infection or therapy), or another reason. In those with pulmonary disease, 44 of 95 (46%) had 1 or more negative cultures at time of final microbiological assessment, with 17 of 95 (18%) achieving culture conversion.

Conclusions

This study reports data supporting long-term safety and tolerability of omadacycline along with signal of effectiveness in treatment of M abscessus infections.

Multicenter Clinical Performance Evaluation of Omadacycline Susceptibility Testing of Enterobacterales on VITEK 2 Systems

We present the first performance evaluation results for omadacycline on the VITEK 2 and VITEK 2 Compact Systems (bioMérieux, Inc.). The trial was conducted at four external sites and one internal site. All sites were in the United States, geographically dispersed as follows: Indianapolis, IN; Schaumburg, IL; Wilsonville, OR; Cleveland, OH; and Hazelwood, MO. In this multisite study, omadacycline was tested against 858 Enterobacterales on the VITEK 2 antimicrobial susceptibility test (AST) Gram-negative (GN) card, and the results were compared to the Clinical and Laboratory Standards Institute broth microdilution (BMD) reference method. The results were analyzed and are presented as essential agreement (EA), category agreement (CA), minor error (mE) rates, major error (ME) rates, and very major error (VME) rates following the US Food and Drug Administration (FDA) and International Standards Organization (ISO) performance criteria requirements. Omadacycline has susceptibility testing interpretive criteria (breakpoints) established by the FDA only; nevertheless, the analysis was also performed using the ISO acceptance criteria to satisfy the registration needs of countries outside the United States. The analysis following FDA criteria (including only Klebsiella pneumoniae and Enterobacter cloacae) showed the following performance: EA = 97.9% (410/419), CA = 94.3% (395/419), VME = 2% (1/51), with no ME present. The performance following ISO criteria (including all Enterobacterales tested) after error resolutions was EA = 98.1% (842/858) and CA = 96.9% (831/858). No ME or VME were observed. The VITEK 2 test met the ISO and FDA criteria of ≥ 95% reproducibility, and ≥ 95% quality control (QC) results within acceptable ranges for QC organisms. In June 2022, the omadacycline VITEK 2 test received FDA 510(k) clearance (K213931) FDA as a diagnostic device to be used in the treatment of acute bacterial skin and skin-structure infections caused by E. cloacae and K. pneumoniae, and for treatment of community-acquired bacterial pneumonia caused by K. pneumoniae. The new VITEK 2 AST-GN omadacycline test provides an alternative to the BMD reference method testing and increases the range of automated diagnostic tools available for determining omadacycline MICs in Enterobacterales.

Omadacycline for treatment of acute bacterial infections: a meta-analysis of phase II/III trials

OBJECTIVE

This study aims to assess the clinical efficacy and safety of omadacycline for the treatment of acute bacterial infections.

METHODS

A search of PubMed, Embase, Cochrane Library, and Clinical Trials was conducted up to July 1, 2022. We included only randomized controlled trials (RCTs), in which omadacycline and other antibiotics were evaluated for treating acute bacterial infections in adults. The primary outcomes were clinical response and microbiological response, whereas the secondary outcome was the risk of adverse events (AEs).

RESULTS

A total of seven RCTs involving 2841 patients with acute bacterial infection were included. Overall, our study illustrated that the clinical cure ratio of omadacycline was similar to the comparators in the treatment of acute bacterial infections (OR = 1.18, 95%CI = 0.96, 1.46, I² = 29%). Omadacycline had a microbiological eradication rate similar to comparators in the treatment of acute bacterial infections (OR = 1.02, 95%CI = 0.81, 1.29, I² = 42%). No statistical differences were observed between omadacycline and the comparators in terms of infection caused by Staphylococcus aureus (OR = 1.14, 95%CI = 0.80, 1.63, I² = 0%), methicillin-resistant S. aureus (MRSA, OR = 1.28, 95%CI = 0.73, 2.24, I² = 0%), methicillin-susceptible S. aureus (MSSA, OR = 1.12, 95%CI = 0.69, 1.81, I² = 0%), and Enterococcus faecalis (OR = 2.47, 95%CI = 0.36, 16.97, I² = 7%). A significant difference was found between omadacycline and the comparators for the risk of any AEs and treatment related AEs. The risk of discontinuation of the study drug due to an AEs was lower for omadacycline than for the comparators.

CONCLUSION

Omadacycline is as good as comparators in terms of efficacy and tolerance in the treatment of acute bacterial infections in adult patients. Thus, omadacycline is an appropriate option for antibiotic therapy in adult patients with acute bacterial infections.

New Antibiotics for Staphylococcus aureus Infection: An Update from the World Association of Infectious Diseases and Immunological Disorders (WAidid) and the Italian Society of Anti-Infective Therapy (SITA)

Staphylococcus aureus is an extremely virulent pathogen that is capable of quickly evolving and developing antibiotic resistance. To overcome this problem, new antibiotics have been developed. Some of these have been licenced for use in clinical practice, mainly for the treatment of adults with acute skin and soft tissue infections, in addition to both community-acquired pneumonia (CAP) and nosocomial pneumonia (hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia). In this paper, the main characteristics and clinical use of new licenced anti-staphylococcal drugs have been discussed. In vitro studies have demonstrated that some new anti-staphylococcal antibiotics have better antimicrobial activity and, at least in certain cases, more favourable pharmacokinetic properties and higher safety and tolerability than the presently available anti-staphylococcal drugs. This suggests that they may have a potential use in reducing the risk of failure of S. aureus therapy. However, an in-depth analysis of microbiological and clinical studies carried out with these new drugs seems to indicate that further studies need to be conducted before the problem of resistance of S. aureus to the antibiotics available today can be completely solved. Considering the overall available research, the drugs that are active against S. aureus appear to present a great therapeutic opportunity for overcoming resistance to traditional therapy. There are advantages in the pharmacokinetic characteristics of some of these drugs and they have the potential to reduce hospital stays and economic costs associated with their use.

Pharmacokinetic-Pharmacodynamic Target Attainment Analyses Evaluating Omadacycline Dosing Regimens for the Treatment of Patients with Community-Acquired Bacterial Pneumonia Arising from Streptococcus pneumoniae and Haemophilus influenzae

Omadacycline, a novel aminomethylcycline with in vitro activity against Gram-positive and -negative organisms, including Streptococcus pneumoniae and Haemophilus influenzae, is approved in the United States to treat patients with community-acquired bacterial pneumonia (CABP). Using nonclinical pharmacokinetic-pharmacodynamic (PK-PD) targets for efficacy and in vitro surveillance data for omadacycline against S. pneumoniae and H. influenzae, and a population pharmacokinetic model, PK-PD target attainment analyses were undertaken using total-drug epithelial lining fluid (ELF) and free-drug plasma exposures to evaluate omadacycline 100 mg intravenously (i.v.) every 12 h or 200 mg i.v. every 24 h (q24h) on day 1, followed by 100 mg i.v. q24h on day 2 and 300 mg orally q24h on days 3 to 5 for patients with CABP. Percent probabilities of PK-PD target attainment on days 1 and 2 by MIC were assessed using the following four approaches for selecting PK-PD targets: (i) median, (ii) second highest, (iii) highest, and (iv) randomly assigned total-drug ELF and free-drug plasma ratio of the area under the concentration-time curve to the MIC (AUC/MIC ratio) targets associated with a 1-log₁₀ CFU reduction from baseline. Percent probabilities of PK-PD target attainment based on total-drug ELF AUC/MIC ratio targets on days 1 and 2 were ≥91.1% for S. pneumoniae for all approaches but the highest target and ≥99.2% for H. influenzae for all approaches at MIC₉₀s (0.12 and 1 μg/mL for S. pneumoniae and H. influenzae, respectively). Lower percent probabilities of PK-PD target attainment based on free-drug plasma AUC/MIC ratio targets were observed for randomly assigned and the highest free-drug plasma targets for S. pneumoniae and for all targets for H. influenzae. These data provided support for approved omadacycline dosing regimens to treat patients with CABP and decisions for the interpretive criteria for the in vitro susceptibility testing of omadacycline against these pathogens.

Evaluation of the Impact of Comorbidities on Omadacycline Pharmacokinetics

Omadacycline is approved in the United States for the treatment of patients with community-acquired bacterial pneumonia or acute bacterial skin and skin structure infections. Analyses were undertaken to evaluate pharmacokinetic differences among subjects or patients stratified by comorbidities. Differences in clearance by smoking status, history of diabetes mellitus, chronic lung disease, hypertension, heart failure, or coronary artery disease were evaluated using a Welch two-sample t test. Smoking was the only significant comorbidity after correction for sex, with a clinically insignificant difference of 13%. Omadacycline dose adjustments based on these comorbidities do not appear to be warranted.

Omadacycline in treating community-based infections: a review and expert perspective

INTRODUCTION

Omadacycline is approved for the treatment of community-acquired bacterial pneumonia (CABP) and acute bacterial skin and soft tissue infection (ABSSSI). The integration of newer agents into clinical use involves understanding the nuances of clinical decision-making. This review will provide an in-depth focus on omadacycline in clinical practice.

AREAS COVERED

Literature review of omadacycline utilizing PubMed was performed to provide a comprehensive evaluation of omadacycline pharmacology, microbiology, registrational Phase 3 clinical trials, and post-marketing clinical studies. In addition, the immunomodulatory and other attributes of tetracycline class of antibiotics, of which omadacycline is a member, are reviewed, introducing the concept of antibiotic selection with attention to the bacterial pathogen and human host relationship.

EXPERT OPINION

Omadacycline builds upon the favorable attributes of tetracycline antibiotics and provides very reliable empiric coverage for both Staphylococcus aureus and Streptococcus spp. Clinicians require a more robust understanding of antibiotics, including omadacycline, in order to optimize patient outcomes, streamline care, and reduce medical costs.

A Comprehensive Overview of the Antibiotics Approved in the Last Two Decades: Retrospects and Prospects

Due to the overuse of antibiotics, bacterial resistance has markedly increased to become a global problem and a major threat to human health. Fortunately, in recent years, various new antibiotics have been developed through both improvements to traditional antibiotics and the discovery of antibiotics with novel mechanisms with the aim of addressing the decrease in the efficacy of traditional antibiotics. This manuscript reviews the antibiotics that have been approved for marketing in the last 20 years with an emphasis on the antibacterial properties, mechanisms, structure-activity relationships (SARs), and clinical safety of these antibiotics. Furthermore, the current deficiencies, opportunities for improvement, and prospects of antibiotics are thoroughly discussed to provide new insights for the design and development of safer and more potent antibiotics.

Omadacycline and Clostridioides difficile: A Systematic Review of Preclinical and Clinical Evidence

OBJECTIVE

The objective of this systematic review is to summarize in vitro, preclinical, and human data related to omadacycline and Clostridioides difficile infection (CDI).

DATA SOURCES

PubMed and Google Scholar were searched for "omadacycline" AND ("Clostridium difficile" OR "C difficile" OR "Clostridioides difficile") for any studies published before February 15, 2022. The US Food and Drug Administration (FDA) Adverse Events Reporting System (AERS) was searched for omadacycline (for reports including "C. difficile" or "CDI" or "gastrointestinal infection"). The publications list publicly available at Paratek Pharmaceuticals, Inc. Web site was reviewed.

STUDY SELECTION AND DATA EXTRACTION

Publications presenting primary data on omadacycline and C. difficile published in English were included.

DATA SYNTHESIS

Preclinical and clinical evidence was extracted from 14 studies. No case reports in indexed literature and no reports on FDA AERS were found. Omadacycline has potent in vitro activity against many C. difficile clinical strains and diverse ribotypes. In phase 3 studies, there were no reports of CDI in patients who received omadacycline for either community-acquired bacterial pneumonia or acute bacterial skin and skin structure infection.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Omadacycline should be considered a low-risk antibiotic regarding its propensity to cause CDI.

CONCLUSIONS

Reducing the burden of CDI on patients and the health care system should be a priority. Patients with appropriate indications who are at heightened risk of CDI may be suitable candidates for omadacycline therapy. In these patients, omadacycline may be preferable to antibiotics with a high CDI risk.

Current and emerging drug treatment strategies to tackle invasive community-associated methicillin-resistant Staphylococcus aureus (MRSA) infection: what are the challenges?

INTRODUCTION

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections represent a leading cause of purulent skin and soft tissue infections in some geographical regions. Traditionally, 'old antibiotics' such as trimethoprim-sulfamethoxazole, tetracyclines, clindamycin, chloramphenicol,vancomycin, and teicoplanin have been used to treat these infections, but these were often associated with low efficacy and excessive side effects and toxicity, especially nephrotoxicity. Along with the development of new compounds, the last decade has seen substantial improvements in the management of CA-MRSA infections.

AREAS COVERED

In this review, the authors discuss the current and emerging drug treatment strategies to tackle invasive CA-MRSA infections. Articles reported in this review were selected from through literature searches using the PubMed database.

EXPERT OPINION

The availability of new drugs showing a potent in vitro activity against CA-MRSA represents a unique opportunity to face the threat of resistance while potentially reducing toxicity. All these compounds represent promising options to enhance our antibiotic armamentarium. However, data regarding the use of these new drugs in real-life studies are limited and their best placement in therapy and in terms of optimization of medical resources and balance of cost-effectiveness requires further investigation.

New advances in management and treatment of multidrug-resistant Klebsiella pneumoniae

INTRODUCTION

The management of multidrug-resistant (MDR) Klebsiella pneumoniae (KP) represents a major challenge in the field of infectious diseases. It is associated with a high rate of nosocomial infections with a mortality rate that reaches approximately 50%, even when using an effective antimicrobial therapy. Therefore, combined actions addressing infection control and antibiotic stewardship are required to delay the emergence of resistance. Since new antimicrobial agents targeting MDR-GNB bacteria have been produced during the last years and are now available for physicians to treat MDR, it is fundamental to choose appropriate antimicrobial therapy for K. pneumoniae infection.

AREAS COVERED

The PubMed database was searched to review the most significant recent literature on the topic, including data from articles coming from endemic areas and from the current European and American Guidelines.

EXPERT OPINION

We explore the most effective strategies for prevention of MDR-KP spread and the currently available treatment options, focusing on comparing old strategies and new compounds. We reviewed data concerning newly developed drugs that could play an important role in the future; we also propose a treatment algorithm that could be useful for physicians in daily clinical practice.

Re-establishing the utility of tetracycline-class antibiotics for current challenges with antibiotic resistance

The progressive increase in antibiotic resistance in recent decades calls for urgent development of new antibiotics and antibiotic stewardship programs to help select appropriate treatments with the goal of minimising further emergence of resistance and to optimise clinical outcomes. Three new tetracycline-class antibiotics, eravacycline, omadacycline, and tigecycline, have been approved within the past 15 years, and represent a new era in the use of tetracyclines. These drugs overcome the two main mechanisms of acquired tetracycline-class resistance and exhibit a broad spectrum of in vitro activity against gram-positive, gram-negative, anaerobic, and atypical pathogens, including many drug-resistant strains. We provide an overview of the three generations of tetracycline-class drugs, focussing on the efficacy, safety, and clinical utility of these three new third-generation tetracycline-class drugs. We also consider various scenarios of unmet clinical needs where patients might benefit from re-engagement with tetracycline-class antibiotics including outpatient treatment options, patients with known β-lactam antibiotic allergy, reducing the risk of Clostridioides difficile infection, and their potential as monotherapy in polymicrobial infections while minimising the risk of any potential drug-drug interaction. KEY MESSAGESThe long-standing safety profile and broad spectrum of activity of tetracycline-class antibiotics made them a popular choice for treatment of various bacterial infections; unfortunately, antimicrobial resistance has limited the utility of the early-generation tetracycline agents.The latest generation of tetracycline-class antibiotics, including eravacycline, tigecycline, and omadacycline, overcomes the most common acquired tetracycline resistance mechanisms.Based on in vitro characteristics and clinical data, these newer tetracycline agents provide an effective antibiotic option in the treatment of approved indications in patients with unmet clinical needs - including patients with severe penicillin allergy, with renal or hepatic insufficiency, recent Clostridioides difficile infection, or polymicrobial infections, and those at risk of drug-drug interactions.

Omadacycline for the Treatment of Severe Chlamydia psittaci Pneumonia Complicated with Multiple Organ Failure: A Case Report

Psittacosis is a rare zoonotic disease caused by Chlamydia psittaci infection, and tetracyclines are the preferred treatment. Omadacycline is a novel tetracycline that has a strong in vitro antibacterial activity against atypical pathogens, including C. psittaci; however, clinical data for its usage are lacking. We report a patient with severe C. psittaci-induced pneumonia presenting with a high fever, muscle aches, severe hepatic and renal insufficiency, and acute respiratory failure requiring tracheal intubation and mechanical ventilation. The condition was diagnosed using metagenomic next-generation sequencing. The patient was discharged after treatment with omadacycline. The findings of this study suggest that metagenomic next-generation sequencing is valuable for the rapid and accurate diagnosis of psittacosis. With its good safety profile and no requirement for dose adjustment in special populations, omadacycline is a new option for the treatment of severe C. psittaci pneumonia. However, additional case reports are needed to support this conclusion.

Antibiotics for multidrug-resistant gram-positive bacteria

Background: Antimicrobial resistance is a major global threat to public health and is associated with increased morbidity and mortality. A few therapeutic options for the treatment of multidrug resistant (MDR) gram-positive bacteria, such as methicillin resistant Staphylococcus aureus, MDR Streptococcus pneumoniae, vancomycin resistant Enterococci, are available.Current Concepts: As a result of comprehensive efforts, a dozen novel antibiotics have been developed and approved for the treatment of MDR gram-positive bacteria in the United States and Europe over the past 15 years. However, only a few antibiotics have been introduced in the Republic of Korea. The purpose of this review is to evaluate the antibiotics that act against MDR gram-positive bacteria as a primary therapeutic option. Particularly, this review focuses on novel antibiotics, including ceftaroline, ceftobiprole, telavancin, dalbavancin, oritavancin, tedizolid, delafloxacin, omadacycline, and lefamulin.Discussion and Conclusion: Novel antibiotics against MDR gram-positive bacteria have not yet been sufficiently studied in various clinical settings, and therefore, the approved indications are limited. However, these antibiotics are expected to play a major role in the treatment of MDR gram-positive bacteria owing to their advantages, including broad anti-bacterial spectrum, rapid bactericidal effect, minimal drug-drug interaction, a favorable safety profile, availability of both intravenous and oral formulations, convenient dosing scheme, and a single dose (or once a week) regimen owing to long half-life. It is crucial to introduce these novel antibiotics in the Republic of Korea for the treatment of patients suffering from MDR bacterial infections.

Real-World, Multicenter Case Series of Patients Treated with Oral Omadacycline for Resistant Gram-Negative Pathogens

INTRODUCTION

Antibiotic-resistant Gram-negative bacteria have been associated with substantial morbidity and mortality and have limited treatment options available. Omadacycline (OMC) is an aminomethylcycline antibiotic that has been shown to exhibit broad in vitro activity against antibiotic-resistant Gram-negative bacteria. Given the lack of real-world data, the primary objective of our report was to describe early experience with OMC for the treatment of resistant Gram-negative infections.

METHODS

This was a real-world, multicenter, observational cases series/pilot study conducted in the USA. Inclusion criteria included any adult patient aged ≥ 18 years who received OMC for ≥ 72 h either in the inpatient and/or outpatient setting. Clinical success was defined as a composite of 90-day survival from initiation of OMC, lack of alteration in treatment/addition of other antibiotic due to concerns of OMC failure, and lack of microbiologic recurrence within 30 days from the end of therapy.

RESULTS

Oral OMC was used in nine cases primarily for multidrug-resistant (MDR)/extensively drug-resistant (XDR) Gram-negative bacterial infections (55.6% XDR and/or carbapenem-resistant Acinetobacter baumannii [CRAB]). The majority of infections were of bone/joint (55.6%) origin, followed by intra-abdominal (33.3%) origin. Clinical success occurred in 66.7% of cases, with 80.0% success each in infections of bone/joint origin or those caused by CRAB. One patient experienced an adverse effect that was not treatment limiting while on therapy (gastrointestinal).

CONCLUSION

The use of oral OMC in MDR/XDR Gram-negative infections exhibited a relatively high success rate with minimal adverse effects. Real-world studies with larger case numbers are needed to confirm our initial findings.

Multi-drug resistant gram-negative bacterial pneumonia: etiology, risk factors, and drug resistance patterns

Bacterial pneumonia is one of the most serious public health issues owing to its medical and economic costs, which result in increased morbidity and mortality in people of all ages around the world. Furthermore, antimicrobial resistance has risen over time, and the advent of multi-drug resistance in GNB complicates therapy and has a detrimental impact on patient outcomes. The current review aimed to summarize bacterial pneumonia with an emphasis on gram-negative etiology, pathogenesis, risk factors, resistance mechanisms, treatment updates, and vaccine concerns to tackle the problem before it causes a serious consequence. In conclusion, the global prevalence of GNB in CAP was reported 49.7% to 83.1%, whereas in VAP patients ranged between 76.13% to 95.3%. The most commonly reported MDR-GNB causes of pneumonia were A. baumannii, K. pneumoniae, and P. aeruginosa, with A. baumannii isolated particularly in VAP patients and the elderly. In most studies, ampicillin, tetracyclines, amoxicillin-clavulanic acid, cephalosporins, and carbapenems were shown to be highly resistant. Prior MDR-GNB infection, older age, previous use of broad-spectrum antibiotics, high frequency of local antibiotic resistance, prolonged hospital stays, ICU admission, mechanical ventilation, and immunosuppression are associated with the MDR-GNB colonization. S. maltophilia was reported as a severe cause of HAP/VAP in patients with mechanically ventilated and having hematologic malignancy due to its ability of biofilm formation, site adhesion in respiratory devices, and its intrinsic and acquired drug resistance mechanisms. Effective combination therapies targeting PDR strains and drug-resistant genes, antibiofilm agents, gene-based vaccinations, and pathogen-specific lymphocytes should be developed in the future.

Microwave assisted antibacterial action of Garcinia nanoparticles on Gram-negative bacteria

Owing to the existence of the outer membrane barrier, most antibacterial agents cannot penetrate Gram-negative bacteria and are ineffective. Here, we report a general method for narrow-spectrum antibacterial Garcinia nanoparticles that can only be effective to kill Gram-positive bacteria, to effectively eliminate Gram-negative bacteria by creating transient nanopores in bacterial outer membrane to induce drug entry under microwaves assistance. In vitro, under 15 min of microwaves irradiation, the antibacterial efficiency of Garcinia nanoparticles against Escherichia coli can be enhanced from 6.73% to 99.48%. In vivo, MV-assisted GNs can effectively cure mice with bacterial pneumonia. The combination of molecular dynamics simulation and experimental results reveal that the robust anti-E. coli effectiveness of Garcinia nanoparticles is attributed to the synergy of Garcinia nanoparticles and microwaves. This work presents a strategy for effectively treating both Gram-negative and Gram-positive bacteria co-infected pneumonia using herbal medicine nanoparticles with MV assistance as an exogenous antibacterial auxiliary.

Pharmacokinetics, Safety and Pharmacokinetics/Pharmacodynamics Analysis of Omadacycline in Chinese Healthy Subjects

Objective: Omadacycline is a new type of aminomethylcycline antibiotic, having a broad antibacterial spectrum. But the pharmacokinetic characteristics and safety profile of the Chinese population remain unknown. It is also unclear whether the US-approved treatment regimen is applicable for the Chinese population.

Methods: In a randomized, double-blinded, placebo-controlled dose-escalated trial, the pharmacokinetics of omadacycline was evaluated by a non-compartmental and compartmental model. Monte Carlo simulations were performed using the pharmacokinetic data from the Chinese population to evaluate the probability of target attainment (PTA) and the cumulative fraction of response (CFR) of the US FDA-approved dose regimen.

Results: The three-compartment model successfully described the rapid distribution and slow elimination of omadacycline after the intravenous infusion (i.v.). The double-peak concentration-time curve of the oral absorption (p.o.) was explained by the two-compartment model with two absorption compartments. The steady-state AUC of 100 mg omadacycline i.v. and 300 mg omadacycline p. o. were 12.1 and 19.4 mg h/L, respectively. Pharmacokinetics/pharmacodynamics (PK/PD) analysis showed that the omadacycline dosing regimen with a loading dose (200 mg i.v. q24 h, 100 mg i.v. q12 h, 450 mg p. o. q24 h × 2 days or 300 mg p. o. q12 h) and maintenance dose (100 mg i.v. q24 h or 300 mg p. o. q24 h) could cover the main pathogens of the indications acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP): Staphylococcus aureus and Streptococcus pneumoniae. Also, omadacycline had showed a good safety profile in the Chinese population.

Conclusions: With the evidence provided, omadacycline could be a novel treatment option to Chinese patients with ABSSSI and CABP.

Omadacycline Oral Dosing and Pharmacokinetics in Community-Acquired Bacterial Pneumonia and Acute Bacterial Skin and Skin Structure Infection

Omadacycline, a first-in-class aminomethylcycline antibiotic, is approved in the USA as intravenous (IV) and/or oral therapy for treatment of adults with community-acquired bacterial pneumonia (CABP) or acute bacterial skin and skin structure infections (ABSSSI). Phase 1 and 3 studies indicate that omadacycline dose adjustments are not required for any patient group based on age, sex, race, weight, renal impairment, end-stage renal disease, or hepatic impairment. Equivalency of exposure has also been demonstrated for 300 mg oral and 100 mg IV doses. Using an oral loading-dose regimen results in drug exposures exceeding established efficacy targets against the most common CABP and ABSSSI pathogens by Day 2 of treatment, and omadacycline has demonstrated clinical efficacy and is well tolerated. The oral-only dosing regimens provide the potential for treatment of CABP and ABSSSI either within a hospital setting or in the community, which could support earlier hospital discharge and reduced treatment costs.

The remaining unsolved problems for rational antibiotic therapy use in pediatric community-acquired pneumonia

INTRODUCTION

Despite availability of several official guidelines, not all the problems related to the most effective and safe use of antibiotics in children with community-acquired pneumonia (CAP) have been solved. Presently, too many children receive unneeded antibiotics or, when antibiotics are mandatory, the choice of the drug is not appropriate.

AREAS COVERED

In this paper, the authors discuss the remaining unsolved problems for rational antibiotic therapy use in pediatric community-acquired pneumonia and provide their expert perspectives.

EXPERT OPINION

Further improvement in pediatric CAP management could be derived from physician education on antibiotic use and a larger use, particularly in office practice, of point of care testing or new technologies (i.e. artificial intelligence) to define etiology of a lower respiratory infection. However, recommendations regarding the duration of antibiotic therapy vary largely because of the absence of reliable data on the optimal CAP treatment according to the bacterial etiology of the disease, its severity, and child characteristics. Available evidence seems to confirm that a short course of antibiotics, approximately 5 days, can be effective and lead to results not substantially different from those obtained with prolonged-course antibiotic therapy, at least in patients with mild to moderate disease.

Prepared omadacycline for injection: Nine-day stability and sterility in an elastomeric pump

Objective:

To investigate compatibility, stability, and microbiologic risk of omadacycline 1 mg/mL when prepared in an elastomeric infusion pump and stored under refrigeration for 9 days based upon requests for information from healthcare providers.

Methods:

Omadacycline was reconstituted to 1 mg/mL with sodium chloride 0.9% w/v or dextrose 5% w/v in SMARTeZ® elastomeric infusion pumps and refrigerated for up to 9 days. Samples were taken daily and tested for appearance, pH, osmolality, chemical composition, and particulate matter. For a microbial challenge study, the pumps were spiked with a challenge microorganism ( Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, or Aspergillus brasiliensis) and samples were plated daily for 9 days to assess microbial survival.

Results:

Appearance, pH, osmolality, percent label claim, and particulate matter results remained essentially unchanged for omadacycline solutions in either diluent over the 9-day study. No > 0.5-log day-to-day increases in the challenge-microorganism populations were measured in diluted omadacycline pumps or positive controls. With omadacycline, no growth was seen for S. aureus or E. coli in either diluent, nor for P. aeruginosa in dextrose 5% w/v. Reduction of C. albicans and A. brasiliensis populations over time was similar between omadacycline solutions and positive controls.

Conclusion:

After reconstitution, omadacycline for injection was stable and remained within specifications for use for up to 9 days when refrigerated.

OUP accepted manuscript

Objectives

The standard of care (SOC) for the treatment of pulmonary Mycobacterium avium complex (MAC) disease (clarithromycin, rifabutin, and ethambutol) achieves sustained sputum conversion rates of only 54%. Thus, new treatments should be prioritized.

Methods

We identified the omadacycline MIC against one laboratory MAC strain and calculated drug half life in solution, which we compared with measured MAC doubling times. Next, we performed an omadacycline hollow fibre system model of intracellular MAC (HFS-MAC) exposure–effect study, as well as the three-drug SOC, using pharmacokinetics achieved in patient lung lesions. Data was analysed using bacterial kill slopes (γ-slopes) and inhibitory sigmoid E_max bacterial burden versus exposure analyses. Monte Carlo experiments (MCE) were used to identify the optimal omadacycline clinical dose.

Results

Omadacycline concentration declined in solution with a half-life of 27.7 h versus a MAC doubling time of 16.3 h, leading to artefactually high MICs. Exposures mediating 80% of maximal effect changed up to 8-fold depending on sampling day with bacterial burden versus exposure analyses, while γ-slope-based analyses gave a single robust estimate. The highest omadacycline monotherapy γ-slope was −0.114 (95% CI: −0.141 to −0.087) (r^2 =0.98) versus −0.114 (95% CI: −0.133 to −0.094) (r²= 0.99) with the SOC. MCEs demonstrated that 450 mg of omadacycline given orally on the first 2 days followed by 300 mg daily would achieve the AUC_0-24 target of 39.67 mg·h/L.

Conclusions

Omadacycline may be a potential treatment option for pulmonary MAC, possibly as a back-bone treatment for a new MAC regimen and warrants future study in treatment of this disease.

Current pharmacotherapy for methicillin-resistant Staphylococcus aureus (MRSA) pneumonia

INTRODUCTION

Currently, several antibiotics are active against methicillin-resistant Staphylococcus aureus (MRSA) and can be used for the treatment of pneumonia. They show great variability in terms of antibiotic class, indication, pharmacodynamic/pharmacokinetic properties, type of available formulations, spectrum of activity against bacteria other than MRSA, and toxicity profile.

AREAS COVERED

In this narrative review, the authors discuss the characteristics of currently available agents for the treatment of MRSA pneumonia.

EXPERT OPINION

The availability of different agents with anti-MRSA activity, and approved for the treatment of pneumonia can allow a personalized approach for any given patient based on the severity of the disease, the setting of occurrence, the patient's baseline risk of toxicity and drug interactions, and the possibility of oral therapy whenever early discharge or outpatient treatment are possible. Although some gray areas still remain, like the lack of high certainty evidence on the efficacy of some old agents and on the precise role of companion agents with toxin inhibitory activity in the case of necrotizing pneumonia, the frequent availability of different treatment choices, each with peculiar characteristics, is already allowing an important step toward a precision medicine approach for the treatment of MRSA pneumonia.

The Development of Third-Generation Tetracycline Antibiotics and New Perspectives

The tetracycline antibiotic class has acquired new valuable members due to the optimisation of the chemical structure. The first modern tetracycline introduced into therapy was tigecycline, followed by omadacycline, eravacycline, and sarecycline (the third generation). Structural and physicochemical key elements which led to the discovery of modern tetracyclines are approached. Thus, several chemical subgroups are distinguished, such as glycylcyclines, aminomethylcyclines, and fluorocyclines, which have excellent development potential. The antibacterial spectrum comprises several resistant bacteria, including those resistant to old tetracyclines. Sarecycline, a narrow-spectrum tetracycline, is notable for being very effective against Cutinebacterium acnes. The mechanism of antibacterial action from the perspective of the new compound is approached. Several severe bacterial infections are treated with tigecycline, omadacycline, and eravacycline (with parenteral or oral formulations). In addition, sarecycline is very useful in treating acne vulgaris. Tetracyclines also have other non-antibiotic properties that require in-depth studies, such as the anti-inflammatory effect effect of sarecycline. The main side effects of modern tetracyclines are described in accordance with published clinical studies. Undoubtedly, this class of antibiotics continues to arouse the interest of researchers. As a result, new derivatives are developed and studied primarily for the antibiotic effect and other biological effects.

Surveillance of omadacycline activity tested against clinical isolates from the USA: report from the SENTRY Antimicrobial Surveillance Program, 2019

OBJECTIVES

Omadacycline was tested against 7000 bacterial isolates collected prospectively from medical centres in the USA during 2019.

METHODS

Antimicrobial susceptibility testing was performed according to Clinical and Laboratory Standards Institute (CLSI) guidelines.

RESULTS

Omadacycline was active against: Staphylococcus aureus (MIC_50/90, 0.12/0.25 mg/L; 98.3% susceptible), including methicillin-resistant S. aureus (MRSA); Enterococcus faecalis (MIC_50/90, 0.06/0.25 mg/L; 100.0% susceptible), including vancomycin-resistant enterococci (VRE); Streptococcus pneumoniae (MIC_50/90, 0.06/0.06 mg/L; 99.8% susceptible); viridans group streptococci, including Streptococcus anginosus group (MIC_50/90, 0.03/0.06 mg/L; 100.0% susceptible); β-haemolytic streptococci, including Streptococcus pyogenes (MIC_50/90, 0.06/0.12 mg/L; 99.2% susceptible); Enterobacterales (MIC_50/90, 1/8 mg/L; 86.9% inhibited at ≤4 mg/L), including Escherichia coli (MIC_50/90, 0.5/2 mg/L; 99.6% inhibited at ≤4 mg/L); Enterobacter cloacae (MIC_50/90, 2/4 mg/L; 98.5% susceptible); Klebsiella pneumoniae (MIC_50/90, 1/4 mg/L; 93.2% susceptible); Acinetobacter baumannii (MIC_50/90, 0.5/4 mg/L; 90.8% inhibited at ≤4 mg/L); Haemophilus influenzae (MIC_50/90, 0.5/1 mg/L; 100.0% susceptible); and Moraxella catarrhalis (MIC_50/90, ≤0.12/0.25 mg/L).

CONCLUSION

The 2019 in vitro activity of omadacycline against key Gram-positive and Gram-negative pathogens has not changed compared with the prior 3 years of surveillance in the SENTRY Antimicrobial Surveillance Program. Omadacycline merits further study in serious infections where resistant pathogens may be encountered.