Development of a UHPLC-MS/MS method for the quantification of Pristinamycin ⅠA and ⅡA in beagle dog plasma and its pharmacokinetic application

The aim of this study was to develop and fully validate a sensitive and rapid ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for simultaneous quantification of pristinamycin ⅠA (PⅠA) and pristinamycin ⅡA (PⅡA) in plasma of beagle dogs after oral administration of pristinamycin tablets. PⅠA, PⅡA and quinupristin (internal standard, IS) were separated on an Agilent Eclipse Plus C18 column (2.1 mm × 100 mm, 3.5 μm particle size) by using gradient elution consisting of methanol and water (0.1 % formic acid) at a flow rate of 0.4 mL/min in 4.0 min. Multiple reaction monitoring (MRM) mode was performed to quantify data under monitoring precursor-product ion transitions of m/z 867.6→134.1, 548.4→287.1 and 1022.7→133.9 for PⅠA, PⅡA and IS at positive ion mode, respectively. The method was developed at linearity ranging from 1.0 to 1000 ng/mL for all analytes.The accuracy of PⅠA and PⅡA was observed to range between -10.6 % and 7.1 %, while the precision was found to be within 8.9 %. No significant matrix effect was observed. PⅠA and PⅡA demonstrated stability during sample storage, preparation and analytic procedures. Furthermore, this method was successfully applied in the investigation of the pharmacokinetic profile of PⅠA and PⅡA in beagle dogs after oral administration of pristinamycin tablets (75 mg for PⅠA and 175 mg for PⅡA). The biological half-life (t1/2) was determined to be 1.75 ± 0.07 h and 1.44 ± 0.31 h for PⅠA and PⅡA, respectively. The areas under curves (AUC0-t) of PⅠA and PⅡA were 80.7 ± 24.6 and 230 ± 94.8 μg/L·h, respectively.

Sanyensin with an Unprecedented Architecture: An Effective Strategy from Discovery to Stereochemical Identification of Flexible Natural Products

Under the guidance of genome mining combined with bioassay-coupled metabolomic analyses, an unprecedented macrodiolide sanyensin (1), with two flexible macrolides fused by the rigid oxabicyclo[3.3.1]nonane core, was isolated from the deep-sea-derived Streptomyces sp. OUCT16-30. The stereochemistry of 1 was established by NOEs (nuclear Overhauser effects), J-based configuration analysis, Marfey's analysis, and together with a newly introduced stereochemical study workflow, which greatly shortens the time to obtain correct conformations of flexible structures based on the NMR constraints, thus leading to reliable quantum chemical calculations to establish the absolute configurations. This workflow is expected to have broad applicability for elucidating the stereochemistry of flexible natural products. The macrodiolide framework of 1 is proposed to be formed through a biocatalytic cyclodimerization, followed by a series of nonenzymatic reactions. This work leads to new insights into the unexplored biosynthetic potential of deep-sea microbes and also provides a practical streamline for efficient mining of novel natural products, from discovery to stereochemical finalization.

Treatment of Mycoplasma genitalium infection in pregnancy: A systematic review of international guidelines

BACKGROUND

Mycoplasma genitalium is an emerging pathogen, which has been linked to cervicitis, urethritis and pelvic inflammatory disease (PID). With the advent of multiplex polymerase chain reaction (PCR) panels for sexually transmitted infections, it is increasingly being identified in pregnant women.

OBJECTIVES

The aim was to review international guidelines, which had explicit recommendations for treatment of M. genitalium infection in pregnancy and breastfeeding.

SEARCH STRATEGY

PubMed, EMBASE and Cochrane databases were reviewed with no age, species, language or date restrictions.

SELECTION CRITERIA

Studies were included if they had an explicit recommendation for treatment of M. genitalium in pregnancy. Studies were excluded if there was no recommendation in pregnancy, if they referred to other international guideline recommendations or were historical versions of guidelines.

DATA COLLECTION AND ANALYSIS

References were manually reviewed and 50 papers were selected for review. Only four guidelines were included in the final analysis and they were from Europe, UK, Australia and Aotearoa New Zealand.

MAIN RESULTS

All studies recommended azithromycin as first-line treatment, and advised against moxifloxacin use. The dosing schedule of azithromycin, varied between guidelines, as did the utility/safety of pristinamycin for macrolide resistant infections. Safety data was generally reassuring for azithromycin but inconsistent for pristinamycin.

CONCLUSIONS

Azithromycin is the first-line treatment for macrolide susceptible or unknown resistance infections, but there is a lack of consistency regarding dosing of azithromycin or the utility/safety of pristinamycin for macrolide resistant infections in pregnancy/lactation.

Unearthing naturally-occurring cyclic antibacterial peptides and their structural optimization strategies

Natural products with antibacterial activity are highly desired globally to combat against multidrug-resistant (MDR) bacteria. Antibacterial peptide (ABP), especially cyclic ABP (CABP), is one of the abundant classes. Most of them were isolated from microbes, demonstrating excellent bactericidal effects. With the improved proteolytic stability, CABPs are normally considered to have better druggability than linear peptides. However, most clinically-used CABP-based antibiotics, such as colistin, also face the challenges of drug resistance soon after they reached the market, urgently requiring the development of next-generation succedaneums. We present here a detail review on the novel naturally-occurring CABPs discovered in the past decade and some of them are under clinical trials, exhibiting anticipated application potential. According to their chemical structures, they were broadly classified into five groups, including (i) lactam/lactone-based CABPs, (ii) cyclic lipopeptides, (iii) glycopeptides, (iv) cyclic sulfur-rich peptides and (v) multiple-modified CABPs. Their chemical structures, antibacterial spectrums and proposed mechanisms are discussed. Moreover, engineered analogs of these novel CABPs are also summarized to preliminarily analyze their structure-activity relationship. This review aims to provide a global perspective on research and development of novel CABPs to highlight the effectiveness of derivatives design in identifying promising antibacterial agents. Further research efforts in this area are believed to play important roles in fighting against the multidrug-resistance crisis.

Natural Products That Contain Higher Homologated Amino Acids

This review focuses on discussing natural products (NPs) that contain higher homologated amino acids (homoAAs) in the structure as well as the proposed and characterized biosynthesis of these non-proteinogenic amino acids. Homologation of amino acids includes the insertion of a methylene group into its side chain. It is not a very common modification found in NP biosynthesis as approximately 450 homoAA-containing NPs have been isolated from four bacterial phyla (Cyanobacteria, Actinomycetota, Myxococcota, and Pseudomonadota), two fungal phyla (Ascomycota and Basidiomycota), and one animal phylum (Porifera), except for a few examples. Amino acids that are found to be homologated and incorporated in the NP structures include the following ten amino acids: alanine, arginine, cysteine, isoleucine, glutamic acid, leucine, phenylalanine, proline, serine, and tyrosine, where isoleucine, leucine, phenylalanine, and tyrosine share the comparable enzymatic pathway. Other amino acids have their individual homologation pathway (arginine, proline, and glutamic acid for bacteria), likely utilize the primary metabolic pathway (alanine and glutamic acid for fungi), or have not been reported (cysteine and serine). Despite its possible high potential in the drug discovery field, the biosynthesis of homologated amino acids has a large room to explore for future combinatorial biosynthesis and metabolic engineering purpose.

Streptogramins for the treatment of infections caused by Gram-positive pathogens

INTRODUCTION

Streptogramins (pristinamycin and quinupristin-dalfopristin) can be interesting options for the treatment of infections due to Gram-positive cocci, especially multidrug-resistant isolates.

AREAS COVERED

This review provides an updated overview of structural and activity characteristics, mechanisms of action and resistance, pharmacokinetic/pharmacodynamic, and clinical use of streptogramins.

EXPERT OPINION

The streptogramin antibiotics act by inhibition of the bacterial protein synthesis. They are composed of two chemically distinct compounds, namely type A and type B streptogramins, which exert a rapid bactericidal activity against a wide range of Gram-positive bacteria (including methicillin-resistant staphylococci and vancomycin-resistant enterococci). Several mechanisms of resistance have been identified in staphylococci and enterococci but the prevalence of streptogramin resistance among clinical isolates remains very low. Even if only a few randomized clinical trials have been conducted, the efficacy of pristinamycin has been largely demonstrated with an extensive use for 50 years in France and some African countries. Despite its effectiveness in the treatment of severe Gram-positive bacterial infections demonstrated in several studies and the low rate of reported resistance, the clinical use of quinupristin-dalfopristin has remained limited, mainly due to its poor tolerance. Altogether, streptogramins (especially pristinamycin) can be considered as potential alternatives for the treatment of Gram-positive infections.

Tackling Antibiotic Resistance with Compounds of Natural Origin: A Comprehensive Review

Drug-resistant bacteria pose a serious threat to human health worldwide. Current antibiotics are losing efficacy and new antimicrobial agents are urgently needed. Living organisms are an invaluable source of antimicrobial compounds. The antimicrobial activity of the most representative natural products of animal, bacterial, fungal and plant origin are reviewed in this paper. Their activity against drug-resistant bacteria, their mechanisms of action, the possible development of resistance against them, their role in current medicine and their future perspectives are discussed. Electronic databases such as PubMed, Scopus and ScienceDirect were used to search scientific contributions until September 2020, using relevant keywords. Natural compounds of heterogeneous origins have been shown to possess antimicrobial capabilities, including against antibiotic-resistant bacteria. The most commonly found mechanisms of antimicrobial action are related to protein biosynthesis and alteration of cell walls and membranes. Various natural compounds, especially phytochemicals, have shown synergistic capacity with antibiotics. There is little literature on the development of specific resistance mechanisms against natural antimicrobial compounds. New technologies such as -omics, network pharmacology and informatics have the potential to identify and characterize new natural antimicrobial compounds in the future. This knowledge may be useful for the development of future therapeutic strategies.

How to manage treatment failure in prosthetic joint infection

BACKGROUND

Management for prosthetic joint infections remains a challenging area for both infectious diseases and orthopaedic surgery, particularly in the setting of treatment failure. This is compounded by a lack of level 1 evidence to guide approaches. The optimal management of prosthetic joint infections requires a multi-disciplinary approach combined with shared decision making with the patient.

AIMS

This article describes the approach to prosthetic joint infections in the setting of treatment failure.

SOURCES

Narrative review based on literature review from PubMed. There was no time limit on the studies included. In addition, the reference list for included studies were reviewed for literature saturation with manual searching of clinical guidelines. Management approaches described incorporate evidence- and eminence-based recommendations from expert guidelines and clinical studies, where applicable.

CONTENT

The surgical and antimicrobial approaches for prosthetic joint infections are described for first-line treatment of prosthetic joint infections and approaches in the event of treatment failure. Management approaches are based on an understanding of the role the biofilm plays in the pathogenesis of prosthetic joint infections. The management of these infections aims to fulfil two key goals: to eradicate the biofilm-associated microorganisms and, to maintain a functional joint and quality of life. In treatment failure, these goals are not always feasible, and the role of the multi-disciplinary team and shared-decision making are prominent.

IMPLICATIONS

Prosthetic joint surgery is a high-volume surgery, and the demand for this surgery is continually increasing. With this, the number of infections requiring expert care will also increase. Eminence-based management approaches have been established to guide treatment failure until knowledge gaps in optimal management are addressed by well-designed, clinical trials.

Recommendations for Systemic Antimicrobial Therapy in Fracture-Related Infection: A Consensus From an International Expert Group

Fracture-related infection (FRI) is a major complication in musculoskeletal trauma and one of the leading causes of morbidity. Standardization of general treatment strategies for FRI has been poor. One of the reasons is the heterogeneity in this patient population, including various anatomical locations, multiple fracture patterns, different degrees of soft-tissue injury, and different patient conditions. This variability makes treatment complex and hard to standardize. As these infections are biofilm-related, surgery remains the cornerstone of treatment, and this entails multiple key aspects (eg, fracture fixation, tissue sampling, debridement, and soft-tissue management). Another important aspect, which is sometimes less familiar to the orthopaedic trauma surgeon, is systemic antimicrobial therapy. The aim of this article is to summarize the available evidence and provide recommendations for systemic antimicrobial therapy with respect to FRI, based on the most recent literature combined with expert opinion. LEVEL OF EVIDENCE:: Therapeutic Level V. See Instructions for Authors for a complete description of levels of evidence.

Is coverage of S. aureus necessary in cellulitis/erysipelas? A literature review

BACKGROUND

Empirical treatment of patients with cellulitis/erysipelas usually targets both streptococci and methicillin-sensitive S. aureus (MSSA). However, the recommendation to empirically cover MSSA is weak and based on low-quality evidence.

METHODS AND OBJECTIVE

A systematic review was conducted in PubMed and clinical trial registries to assess the role of S. aureus in cellulitis/erysipelas and the need for empirical MSSA coverage.

RESULTS

Combined microbiological and serological data, and response to penicillin monotherapy suggest that streptococci are responsible for the vast majority of cases of cellulitis/erysipelas. However, most cases are non-culturable and the specificity of microbiological and serological studies is questionable based on recent studies using molecular techniques. According to epidemiological data and three randomized controlled trials, empirical coverage of methicillin-resistant S. aureus (MRSA) is not recommended for most patients, despite the high prevalence of MRSA in many areas. If MRSA is indeed not an important cause of uncomplicated cellulitis/erysipelas, then the same may apply to MSSA. Based on indirect comparison of data from clinical studies, cure rates with penicillin monotherapy (to which most MSSA are resistant) are comparable to the cure rates reported in many studies using wider-spectrum antibiotics.

CONCLUSION

Considering the limitations of microbiological studies in identifying the pathogens responsible for cellulitis/erysipelas, treatment needs to be guided by clinical trials. Trials comparing penicillin or amoxicillin monotherapy to MSSA-covering regimens are needed to definitively answer whether empirical coverage of MSSA is needed and to identify the subset of patients that can be safely treated with penicillin or amoxicillin monotherapy.

Pharmacotherapy of Lower Respiratory Tract Infections in Elderly-Focused on Antibiotics

Lower respiratory tract infections (LRTIs) refer to the inflammation of the trachea, bronchi, bronchioles, and lung tissue. Old people have an increased risk of developing LRTIs compared to young adults. The prevalence of LRTIs in the elderly population is not only related to underlying diseases and aging itself, but also to a variety of clinical issues, such as history of hospitalization, previous antibacterial therapy, mechanical ventilation, antibiotic resistance. These factors mentioned above have led to an increase in the prevalence and mortality of LRTIs in the elderly, and new medical strategies targeting LRTIs in this population are urgently needed. After a systematic review of the current randomized controlled trials and related studies, we recommend novel pharmacotherapies that demonstrate advantages for the management of LRTIs in people over the age of 65. We also briefly reviewed current medications for respiratory communicable diseases in the elderly. Various sources of information were used to ensure all relevant studies were included. We searched Pubmed, MEDLINE (OvidSP), EMBASE (OvidSP), and ClinicalTrials.gov. Strengths and limitations of these drugs were evaluated based on whether they have novelty of mechanism, favorable pharmacokinetic/pharmacodynamic profiles, avoidance of interactions and intolerance, simplicity of dosing, and their ability to cope with challenges which was mainly evaluated by the primary and secondary endpoints. The purpose of this review is to recommend the most promising antibiotics for treatment of LRTIs in the elderly (both in hospital and in the outpatient setting) based on the existing results of clinical studies with the novel antibiotics, and to briefly review current medications for respiratory communicable diseases in the elderly, aiming to a better management of LRTIs in clinical practice.

Identification of the Bacterial Biosynthetic Gene Clusters of the Oral Microbiome Illuminates the Unexplored Social Language of Bacteria during Health and Disease

Small molecules are the primary communication media of the microbial world. Recent bioinformatic studies, exploring the biosynthetic gene clusters (BGCs) which produce many small molecules, have highlighted the incredible biochemical potential of the signaling molecules encoded by the human microbiome. Thus far, most research efforts have focused on understanding the social language of the gut microbiome, leaving crucial signaling molecules produced by oral bacteria and their connection to health versus disease in need of investigation. In this study, a total of 4,915 BGCs were identified across 461 genomes representing a broad taxonomic diversity of oral bacteria. Sequence similarity networking provided a putative product class for more than 100 unclassified novel BGCs. The newly identified BGCs were cross-referenced against 254 metagenomes and metatranscriptomes derived from individuals either with good oral health or with dental caries or periodontitis. This analysis revealed 2,473 BGCs, which were differentially represented across the oral microbiomes associated with health versus disease. Coabundance network analysis identified numerous inverse correlations between BGCs and specific oral taxa. These correlations were present in healthy individuals but greatly reduced in individuals with dental caries, which may suggest a defect in colonization resistance. Finally, corroborating mass spectrometry identified several compounds with homology to products of the predicted BGC classes. Together, these findings greatly expand the number of known biosynthetic pathways present in the oral microbiome and provide an atlas for experimental characterization of these abundant, yet poorly understood, molecules and socio-chemical relationships, which impact the development of caries and periodontitis, two of the world's most common chronic diseases.IMPORTANCE The healthy oral microbiome is symbiotic with the human host, importantly providing colonization resistance against potential pathogens. Dental caries and periodontitis are two of the world's most common and costly chronic infectious diseases and are caused by a localized dysbiosis of the oral microbiome. Bacterially produced small molecules, often encoded by BGCs, are the primary communication media of bacterial communities and play a crucial, yet largely unknown, role in the transition from health to dysbiosis. This study provides a comprehensive mapping of the BGC repertoire of the human oral microbiome and identifies major differences in health compared to disease. Furthermore, BGC representation and expression is linked to the abundance of particular oral bacterial taxa in health versus dental caries and periodontitis. Overall, this study provides a significant insight into the chemical communication network of the healthy oral microbiome and how it devolves in the case of two prominent diseases.

Managing community acquired pneumonia in the elderly - the next generation of pharmacotherapy on the horizon

INTRODUCTION

Community acquired pneumonia (CAP) is associated with high rates of morbidity and mortality, especially among the elderly. Antibiotic treatment for CAP in the elderly is particularly challenging for many reasons, including compliance issues, immunosuppression, polypharmacy and antimicrobial resistance. There are few available antibiotics that are able to address these concerns. Areas covered: After a systematic review of the current literature, we describe seven novel antibiotics that are currently in advanced stages of development (phase 3 and beyond) and show promise for the treatment of CAP in those over the age of 65. These antibiotics are: Solithromycin, Pristinamycin, Nemonaxacin, Lefamulin, Omadacycline, Ceftobiprole and Delafloxacin. Using a novel conceptual framework designed by the present authors, known as the 'San Antonio NIPS model', we evaluate their strengths and weaknesses based on their ability to address the unique challenges that face the elderly. Expert opinion: All seven antibiotics have potential value for effective utilization in the elderly, but to varying degrees based on their NIPS model score. The goal of this model is to reorganize a clinician's focus on antibiotic choices in the elderly and bring attention to a seldom discussed topic that may potentially become a health-care crisis in the next decade.

Old antimicrobials and Gram-positive cocci through the example of infective endocarditis and bone and joint infections

The management of some serious infections such as infective endocarditis (IE) and bone and joint infections (BJIs) caused by Gram-positive cocci (GPC) is complex and requires great responsiveness and effective antimicrobials with high bioavailability in heart valves or bone tissues. Treatment of these infections requires the use of a higher dosage that may result in increased toxicity or the use of new promising antimicrobials to control the infection. However, use of these new antimicrobials could still bring about new toxicity and resistance. Another approach may be the 'comeback' of old antimicrobials, which is evaluated in this review in the treatment of IE and BJIs caused by GPC.

Oral pristinamycin for the treatment of resistant Gram-positive infections in patients with cancer: Evaluation of clinical outcomes

Pristinamycin has been used to treat a range of Gram-positive infections, but reported experience in patients with malignancy is limited. This study aimed to evaluate the use of pristinamycin in patients with cancer at an Australian centre. All patients commenced on oral pristinamycin therapy at the Peter MacCallum Cancer Centre between January 2005 and December 2014 were identified using the hospital pharmacy dispensing system. Information on demographics, co-morbidities, cancer diagnosis, infection characteristics, pristinamycin regimen, pristinamycin tolerability and outcomes was collected. The median duration of follow-up was 398 days. In total, 26 patients received pristinamycin, with median age of 61 years and a male predominance (65%). Underlying diagnoses were haematological malignancies (50%) and solid tumours (50%). Pathogens included 13 meticillin-resistant Staphylococcus aureus, 6 vancomycin-resistant Enterococcus faecium, 4 meticillin-resistant Staphylococcus epidermidis, 2 meticillin-susceptible S. aureus and 1 vancomycin-susceptible E. faecium. Infection sites were osteomyelitis (6), skin and soft-tissue (4), intra-abdominal/pelvic abscess (4), bloodstream (3), empyema (3), endocarditis/endovascular (3), prosthesis-related infection (2) and epididymo-orchitis (1). One patient ceased pristinamycin due to nausea. Regarding outcome, 13 patients (50%) were cured of infection, 8 (31%) had suppression and 5 (19%) had relapse. Relapses included 1 endovascular infection, 2 episodes of osteomyelitis, 1 pelvic abscess and 1 skin and soft-tissue infection. Overall, 81% of patients achieved cure or suppression of antibiotic-resistant or complex Gram-positive infections, consistent with published experience in non-cancer populations. A favourable tolerability profile makes oral pristinamycin a viable treatment option, particularly in settings where outpatient management of cancer is the objective.

Pristinamycin in the treatment of MSSA bone and joint infection

OBJECTIVES

The aim of this study was to evaluate pristinamycin in the treatment of MSSA bone and joint infection (BJI).

PATIENTS AND METHODS

A retrospective, single-centre cohort study (2001-11) investigated outcome in adults receiving pristinamycin for MSSA BJI and pristinamycin-related adverse events (AEs).

RESULTS

One hundred and two MSSA BJIs were assessed in 98 patients [chronic infection, 33.3%; and orthopaedic device-related infection (ODI), 67.6%]. Surgery was performed in 77.5% of total cases, and in all but three ODIs, associated with antibiotic therapy of a median total duration of 29.2 weeks. Pristinamycin was prescribed as a part of the initial intensive treatment phase (29.4%) and/or included in final maintenance therapy (83.3%) at a dose of 47.6 (45.5-52.6) mg/kg/day for 9.3 (1.4-20.4) weeks. AEs occurred in 13.3% of patients, consisting of gastrointestinal disorder (76.9%) or allergic reaction (23.1%), leading to treatment interruption in 11 cases. AEs were related to daily dose (OR, 2.733 for each 10 additional mg/kg/day; P = 0.049). After a follow-up of 76.4 (29.6-146.9) weeks, the failure rate was 34.3%, associated with ODI (OR, 4.421; P = 0.006), particularly when the implant was retained (OR, 4.217; P = 0.007). In most patients, the pristinamycin companion drug was a fluoroquinolone (68.7%) or rifampicin (21.7%), without difference regarding outcome.

CONCLUSIONS

Pristinamycin is an effective, well-tolerated alternative therapeutic option in MSSA BJI, on condition that a daily dosage of 50 mg/kg is respected.

A new strategy to fight antimicrobial resistance: the revival of old antibiotics

The increasing prevalence of hospital and community-acquired infections caused by multidrug-resistant (MDR) bacterial pathogens is limiting the options for effective antibiotic therapy. Moreover, this alarming spread of antimicrobial resistance has not been paralleled by the development of novel antimicrobials. Resistance to the scarce new antibiotics is also emerging. In this context, the rational use of older antibiotics could represent an alternative to the treatment of MDR bacterial pathogens. It would help to optimize the armamentarium of antibiotics in the way to preserve new antibiotics and avoid the prescription of molecules known to favor the spread of resistance (i.e., quinolones). Furthermore, in a global economical perspective, this could represent a useful public health orientation knowing that several of these cheapest “forgotten” antibiotics are not available in many countries. We will review here the successful treatment of MDR bacterial infections with the use of old antibiotics and discuss their place in current practice.