Affinity of ceftaroline and other beta-lactams for penicillin-binding proteins from Staphylococcus aureus and Streptococcus pneumoniae

Dynamic migration and risk of cephalosporin antibiotic resistance genes: Move from pharmaceutical plants through wastewater treatment plants to coastal tidal flats sediments

The migration and dissemination of antibiotics and their corresponding antibiotic resistance genes (ARGs) from pharmaceutical plants through wastewater treatment to the environment introduce exogenous ARGs, increasing the risk of antibiotic resistance. Cephalosporin antibiotics (Ceps) are among the most widely used antibiotics with the largest market scale today, and the issue of resistance is becoming increasingly severe. In this study, a cephalosporin pharmaceutical plant was selected and metagenomic analysis was employed to investigate the dissemination patterns of cephalosporin antibiotics (Ceps) and their ARGs (CepARGs) from the pharmaceutical plant through the wastewater treatment plant to tidal flats sediments. The findings revealed a significant reduction in the total concentration of Ceps by 90.32 % from the pharmaceutical plant's Pioneer Bio Reactor (PBR) to the effluent of the wastewater treatment plant, and a notable surge of 172.13 % in the relative abundance of CepARGs. It was observed that CepARGs originating from the PBR could migrate along the dissemination chain, contributing to 60 % of the CepARGs composition in tidal flats sediments. Microorganisms play a crucial role in the migration of CepARGs, with efflux-mediated CepARGs, as an intrinsic resistance mechanism, exhibiting a higher prospensity for migration due to their presence in multiple hosts. While Class I risk CepARGs are present at the pharmaceutical and wastewater plant stages, Class I ina-CepARGs are completely removed during wastewater treatment and do not migrate to the environment. This study reveals the dynamic migration characteristics and potential risk changes regarding Ceps and CepARGs in real dissemination chains, providing new theoretical evidence for the mitigation, control, and risk prevention of CepARGs.

Antimicrobial peptides as promising antibiotic adjuvants to combat drug-resistant pathogens

The widespread antimicrobial resistance (AMR) calls for the development of new antimicrobial strategies. Antibiotic adjuvant rescues antibiotic activity and increases the life span of the antibiotics, representing a more productive, timely, and cost-effective strategy in fighting drug-resistant pathogens. Antimicrobial peptides (AMPs) from synthetic and natural sources are considered new-generation antibacterial agents. Besides their direct antimicrobial activity, growing evidence shows that some AMPs effectively enhance the activity of conventional antibiotics. The combinations of AMPs and antibiotics display an improved therapeutic effect on antibiotic-resistant bacterial infections and minimize the emergence of resistance. In this review, we discuss the value of AMPs in the age of resistance, including modes of action, limiting evolutionary resistance, and their designing strategies. We summarise the recent advances in combining AMPs and antibiotics against antibiotic-resistant pathogens, as well as their synergistic mechanisms. Lastly, we highlight the challenges and opportunities associated with the use of AMPs as potential antibiotic adjuvants. This will shed new light on the deployment of synergistic combinations to address the AMR crisis.

Cephalosporin resistance, tolerance, and approaches to improve their activities

Cephalosporins comprise a β-lactam antibiotic class whose first members were discovered in 1945 from the fungus Cephalosporium acremonium. Their clinical use for Gram-negative bacterial infections is widespread due to their ability to traverse outer membranes through porins to gain access to the periplasm and disrupt peptidoglycan synthesis. More recent members of the cephalosporin class are administered as last resort treatments for complicated urinary tract infections, MRSA, and other multi-drug resistant pathogens, such as Neisseria gonorrhoeae. Unfortunately, there has been a global increase in cephalosporin-resistant strains, heteroresistance to this drug class has been a topic of increasing concern, and tolerance and persistence are recognized as potential causes of cephalosporin treatment failure. In this review, we summarize the cephalosporin antibiotic class from discovery to their mechanisms of action, and discuss the causes of cephalosporin treatment failure, which include resistance, tolerance, and phenomena when those qualities are exhibited by only small subpopulations of bacterial cultures (heteroresistance and persistence). Further, we discuss how recent efforts with cephalosporin conjugates and combination treatments aim to reinvigorate this antibiotic class.

Safety and Efficacy of Ceftriaxone in the Treatment of Methicillin-Susceptible Staphylococcus aureus Bloodstream Infections: A Noninferiority Retrospective Cohort Study

BACKGROUND

Antistaphylococcal penicillins and cefazolin are the treatments of choice for methicillin-susceptible Staphylococcus aureus (MSSA) infections, requiring multiple doses daily. At Parkland, eligible uninsured patients with MSSA bloodstream infections (BSI) receive self-administered outpatient parenteral antimicrobial therapy (S-OPAT). Ceftriaxone was used in a cohort of S-OPAT patients for ease of once-daily dosing.

OBJECTIVE

A retrospective study was conducted to evaluate clinical outcomes for patients discharged with ceftriaxone versus cefazolin to treat MSSA BSI.

METHODS

A retrospective cohort noninferiority study design was used to assess treatment efficacy of ceftriaxone versus cefazolin among Parkland S-OPAT patients treated from April 2012 to March 2020. Demographic, clinical, and treatment-related adverse events data were collected. Clinical outcomes included treatment failure as defined by repeat positive blood culture or retreatment within 6 months, all-cause 30-day readmission rates, and central line-associated bloodstream infection (CLABSI) rates.

RESULTS

Of 368 S-OPAT patients with MSSA BSI, 286 (77.7%) received cefazolin, and 82 (22.3%) received ceftriaxone. Demographics and comorbidities were similar for both groups. There were no treatment failures in the ceftriaxone group compared with 4 (1%) in the cefazolin group (P = 0.58). No difference in 30-day readmission rate between groups was found. The CLABSI rates were lower in ceftriaxone group (2%) compared with cefazolin (11%; P = 0.02). Limitations include retrospective cohort design.

CONCLUSIONS

Ceftriaxone was found to be noninferior to cefazolin in this study. Our findings suggest that ceftriaxone is a safe and effective treatment of MSSA BSI secondary to osteoarticular or skin and soft tissue infections when used in the S-OPAT setting.

POSTER ABSTRACT

OFID on 2018 Nov; 5(Suppl 1): S316: doi: 10.1093/ofid/ofy210.894.

Lung penetration and pneumococcal target binding of antibiotics in lower respiratory tract infection

OBJECTIVES

To achieve the therapeutic effects, antibiotics must penetrate rapidly into infection sites and bind to targets. This study reviewed updated knowledge on the ability of antibiotics to penetrate into the lung, their physicochemical properties influencing the pulmonary penetration and their ability to bind to targets on pneumococci.

METHODS

A search strategy was developed using PubMED, Web of Science, and ChEMBL. Data on serum protein binding, drug concentration, target binding ability, drug transporters, lung penetration, physicochemical properties of antibiotics in low respiratory tract infection (LRTI) were collected.

RESULTS

It was seen that infection site-to-serum concentration ratios of most antibiotics are >1 at different time points except for ceftriaxone, clindamycin and vancomycin. Most agents have proper physicochemical properties that facilitate antibiotic penetration. In antimicrobial-resistant Streptococcus pneumoniae, the binding affinity of antibiotics to targets mostly decreases compared to that in susceptible strains. The data on binding affinity of linezolid, clindamycin and vancomycin were insufficient. The higher drug concentration at the infection sites compared to that in the blood can be associated with inflammation conditions. Little evidence showed the effect of drug transporters on the clinical efficacy of antibiotics against LRTI.

CONCLUSIONS

Data on antibiotic penetration into the lung in LRTI patients and binding affinity of antibiotics for pneumococcal targets are still limited. Further studies are required to clarify the associations of the lung penetration and target binding ability of antibitotics with therapeutic efficacy to help propose the right antibiotics for LRTI.

Identification of 5-(Aryl/Heteroaryl)amino-4-quinolones as Potent Membrane-Disrupting Agents to Combat Antibiotic-Resistant Gram-Positive Bacteria

Nosocomial infections caused by resistant Gram-positive organisms are on the rise, presumably due to a combination of factors including prolonged hospital exposure, increased use of invasive procedures, and pervasive antibiotic therapy. Although antibiotic stewardship and infection control measures are helpful, newer agents against multidrug-resistant (MDR) Gram-positive bacteria are urgently needed. Here, we describe our efforts that led to the identification of 5-amino-4-quinolone 111 with exceptionally potent Gram-positive activity with minimum inhibitory concentrations (MICs) ≤0.06 μg/mL against numerous clinical isolates. Preliminary mechanism of action and resistance studies demonstrate that the 5-amino-4-quinolones are bacteriostatic, do not select for resistance, and selectively disrupt bacterial membranes. While the precise molecular mechanism has not been elucidated, the lead compound is nontoxic displaying a therapeutic index greater than 500, is devoid of hemolytic activity, and has attractive physicochemical properties (clog P = 3.8, molecular weight (MW) = 441) that warrant further investigation of this promising antibacterial scaffold for the treatment of Gram-positive infections.

Thermal and Microwave-Assisted Synthesis of New Highly Functionalized Bis-β-lactams from Available Compounds via Bisketene as an Intermediate

The synthesis of highly functionalized bis-β-lactams containing aromatic rings was achieved by thermal and microwave-assisted methods starting from easily available 2-(4-hydroxyphenyl)acetic acid and 2,2'-(propane-2,2-diyl)diphenol precursors. The approach to these valuable heterocyclic scaffolds involved formal [2π + 2π] cycloadditions between Schiff bases and novel bisketenes, which were generated in situ, followed by an electrocyclic reaction of zwitterionic intermediates. Reactions carried out under microwave irradiation were clean and gave high yields with significantly reduced reaction times. Interestingly, in the thermal method, the reaction proceeded in a stereospecific manner, and only the trans-cis or cis-cis isomers were formed. However, under the microwave conditions, the reaction proceeded stereoselectively, and other possible isomers such trans-trans and cis-trans isomers were formed in addition to the product formed under thermal conditions. More interestingly, when the two compounds that did not produce any products under thermal conditions were reacted under microwave conditions, one formed the trans-cis isomer and the other formed the cis-trans and trans-trans isomers as two products .

Antimicrobial Activity of Ceftaroline and Comparator Agents Against Ceftriaxone-Nonsusceptible Streptococcus pneumoniae from the United States (2008-2020)

We evaluated the activity of ceftaroline against clinical isolates of ceftriaxone-nonsusceptible Streptococcus pneumoniae from United States medical centers. Streptococcus pneumoniae isolates (n = 21,750) were consecutively collected from 201 medical centers in 2008-2020 and tested for susceptibility by broth microdilution method. Among these isolates, 1,419 (6.5%) were ceftriaxone-nonsusceptible (ceftriaxone minimum inhibitory concentration [MIC], ≥2 mg/L). Other resistant subgroups analyzed included multidrug-resistant (MDR; nonsusceptibility to ≥3 classes of agents; n = 4,454) and extensively drug-resistant (XDR; nonsusceptibility to ≥5 classes; n = 1,708) isolates. Ceftriaxone susceptibility increased from 89.0% (2008-2011) to 98.1% (2018-2020). Ceftaroline was active against 99.9% of ceftriaxone-nonsusceptible isolates (MIC_50/90, 0.25/0.25 mg/L) and retained potent activity against MDR (n = 4,454; MIC_50/90, 0.12/0.25 mg/L; >99.9% susceptible) and XDR (n = 1,708; MIC_50/90, 0.25/0.25 mg/L; 100.0% susceptible) isolates. Only one isolate had a ceftaroline MIC ≥0.5 mg/L. In summary, ceftaroline demonstrated potent and consistent activity over time (2008-2020) against a large collection of S. pneumoniae from U.S. medical centers, including ceftriaxone-nonsusceptible, MDR, and XDR isolates.

Comparing the Outcomes of Ceftaroline plus Vancomycin or Daptomycin Combination Therapy versus Vancomycin or Daptomycin Monotherapy in Adults with Methicillin-Resistant Staphylococcus aureus Bacteremia—A Meta-Analysis

Introduction: Combination therapy with daptomycin plus ceftaroline to treat methicillin-resistant Staphylococcus aureus bacteremia has been reported to reduce methicillin-resistant Staphylococcus aureus bacteremia-related mortality. The purpose of the current meta-analysis was to compare the clinical outcome of methicillin-resistant Staphylococcus aureus bacteremia in patients treated with daptomycin or vancomycin plus ceftaroline combination therapy versus daptomycin or vancomycin monotherapy. Methods: Studies were included if they directly compared the efficacy of daptomycin or vancomycin plus ceftaroline combination therapy with that of daptomycin or vancomycin monotherapy in the treatment of methicillin-resistant Staphylococcus aureus bacteremia in adult patients. Results: One randomized controlled trial and five retrospective studies were included in the meta-analysis. The combination therapy group had an in-hospital mortality, duration of bacteremia, and adverse event rate similar to those patients who had monotherapy. There was less bacteremia recurrence in the combination group. Initial combination therapy with ceftaroline for the treatment of methicillin-resistant Staphylococcus aureus bacteremia showed a trend of reducing the risk of in-hospital mortality in the current meta-analysis. Conclusions: Randomized controlled trials are needed to further study the role of initial combination therapy with daptomycin or vancomycin plus ceftaroline in the treatment of methicillin-resistant Staphylococcus aureus bacteremia.

Overcoming the rising incidence and evolving mechanisms of antibiotic resistance by novel drug delivery approaches - An overview

Antimicrobial resistance is a normal evolutionary process for microorganisms. Antibiotics exerted accelerated selective pressure that hasten bacterial resistance through mutation, and acquisition external genes. These genes often carry multiple antibiotic resistant determinants allowing the recipient microbe an instant "super-bug" status. The extent of Antimicrobial Resistance (AMR) has reached a level of global crisis, existing antimicrobials are no long effective in treating infections caused by AMR pathogens. The great majority of clinically available antimicrobial agents are administered through oral and intra-venous routes. Overcoming antibacterial resistance by novel drug delivery approach offered new hopes, particularly in the treatment of AMR pathogens in sites less assessible through systemic circulation such as the lung and skin. In the current review, we will revisit the mechanism and incidence of important AMR pathogens. Finally, we will discuss novel drug delivery approaches including novel local antibiotic delivery systems, hybrid antibiotics, and nanoparticle-based antibiotic delivery systems.

Ceftaroline Dosage Optimized for Pediatric Patients With Renal Impairment Using Physiologically Based Pharmacokinetic Modeling

Ceftaroline fosamil is a fifth-generation cephalosporin approved as a treatment for adults and children with community-acquired bacterial pneumonia and acute bacterial skin and skin structure infections. However, its pharmacokinetics have not been fully evaluated in children with renal impairment. This study aimed to propose proper ceftaroline dosages optimized for the renally impaired pediatric population using physiologically based pharmacokinetic (PBPK) modeling. A PBPK model of ceftaroline was established and verified to simulate its disposition in the healthy population and renally impaired adults and to predict the exposure in renally impaired pediatric patients. Consistency was confirmed between simulated and observed data after intravenous administration of various ceftaroline regimens; fold errors were within the 2-fold error range. Among 6-year-old children, healthy subjects had 1.5-fold, 2-fold, and 2.6-fold lower areas under the plasma concentration-time curve (AUCs) than the moderate, severe, and end-stage renally impaired patient groups, respectively; among 1-year-old children, healthy subjects had 1.5-fold, 2.1-fold, and 2.5-fold lower AUCs than the respective renally impaired patient groups; among 1-month-old children, healthy subjects had 1.5-fold, 1.8-fold, and 2.2-fold lower AUCs than the respective renally impaired patient groups. The proposed dosage should be adjusted to 8, 6, and 5 mg/kg every 8 hours for patients aged ≥2 years to <18 years (≤33 kg) with moderate, severe, and end-stage renal impairment, respectively; 5, 4, and 3 mg/kg every 8 hours for patients aged 2 months to <2 years with moderate, severe, and end-stage renal impairment, respectively; 4, 3.5, and 2.5 mg/kg every 8 hours for patients 0 to <2 months of age with moderate, severe, and end-stage renal impairment, respectively. Furthermore, pharmacodynamic investigations demonstrated that adequate antimicrobial effects were attained at the proposed doses in 3 age groups. Hence, our PBPK model can be an effective tool to support ceftaroline dosage proposals for renally impaired pediatric patients.

Clinical Features and Outcomes of Streptococcus pneumoniae Meningitis in Children: A Retrospective Analysis of 26 Cases in China

BACKGROUND

Streptococcus pneumoniae is an important cause of pediatric meningitis.

OBJECTIVE

The aim of this study was to analyze the clinical features and outcomes of children with pneumococcal meningitis at our hospital in China, so as to provide basis for improving the clinical treatment effect.

METHODS

This retrospective analysis included patients aged <16 years treated for pneumococcal meningitis at the Department of Neurology, Children's Hospital of Shanxi (January 2014-February 2016). Clinical data were extracted from the medical records. Patients were followed up for 6 months after discharge.

RESULTS

The analysis included 26 children aged 2 months to 13 years, with 17 (65.4%) aged <3 years. Presenting symptoms included fever (100%), lethargy (100%), impaired consciousness (88.5%), neck stiffness (69.2%), seizures (53.8%), and headache (50.0%). All patients had positive cerebrospinal fluid (CSF) cultures. The final treatment was vancomycin combined with a third-generation cephalosporin or other antibiotics in 25 patients. Eleven patients (42.3%) were recovered, 3 (11.5%) had neurological sequelae, and 12 (46.2%) died. Impaired consciousness (p = 0.035), cerebral hernia (p = 0.037), respiratory failure (p = 0.004), heart failure (p = 0.044), septic shock (p = 0.037), low CSF white blood cell count (p = 0.036), high CSF protein levels (p = 0.028), low white blood cell count (p = 0.036), and low blood neutrophil ratio (p = 0.016) are associated with a poor prognosis to pneumococcal meningitis.

CONCLUSION

Pneumococcal meningitis is associated with a poor prognosis in many children. Poor prognosis might be related to early ineffective antibiotic therapy, a combination of systemic failure, neurological problems, and changed inflammatory response. It is important to rapid initiation of appropriate antibiotic therapy if meningitis is suspected.

In vitro activity of ceftaroline and comparators against bacterial isolates collected globally from patients with skin infections

OBJECTIVES

This study reports the antimicrobial activities of ceftaroline and comparators against bacterial isolates from patients with skin and skin-structure infections (2015-2018).

METHODS

A central laboratory performed antimicrobial susceptibility testing according to CLSI broth microdilution methodology. EUCAST breakpoints were used.

RESULTS

Isolates were collected in Europe (14 408 isolates; 53.9%), Asia/South Pacific (SP) (5317; 19.9%), Latin America (4268; 16.0%) and Africa/Middle East (ME) (2753; 10.3%). In all regions, all 7950 methicillin-susceptible Staphylococcus aureus (MSSA) isolates were susceptible to ceftaroline and vancomycin; susceptibility to daptomycin, linezolid, teicoplanin and tigecycline was ≥99.6%. Susceptibility of all 9174 methicillin-resistant S. aureus (MRSA) isolates to daptomycin, linezolid, teicoplanin, tigecycline and vancomycin was ≥97.7%, with 90.8-96.5% susceptible to ceftaroline. The ceftaroline MIC90 was 0.008 mg/L against Streptococcus pyogenes, 0.015-0.03 mg/L against Streptococcus agalactiae and 0.008-0.015 mg/L against Streptococcus dysgalactiae. All β-haemolytic streptococci were susceptible to vancomycin. Susceptibility of extended-spectrum β-lactamase (ESBL)-negative Escherichia coli to ceftaroline ranged from 67.0% in Asia/SP to 91.0% in Africa/ME; susceptibility to amikacin, meropenem and tigecycline was ≥96.7% in all regions. Susceptibility of ESBL-negative Klebsiella pneumoniae to ceftaroline ranged from 78.4% in Europe to 83.2% in Africa/ME, and among ESBL-negative Klebsiella oxytoca was 76.3% in Asia/SP and 89.0-93.5% in other regions. Among ESBL-negative K. pneumoniae and ESBL-negative K. oxytoca, susceptibility was highest to amikacin (93.7-96.4% and 95.7-100%, respectively) and meropenem (89.7-97.4% and 98.3-100%, respectively).

CONCLUSION

Ceftaroline was active against the Gram-positive isolates collected. Susceptibility of ESBL-negative Gram-negative isolates showed regional variations.

In vitro susceptibility of ceftaroline against clinically important Gram-positive cocci, Haemophilus species and Klebsiella pneumoniae in Taiwan: Results from the Antimicrobial Testing Leadership and Surveillance (ATLAS) in 2012-2018

BACKGROUND/PURPOSE

Ceftaroline, with a unique activity against methicillin-resistant Staphylococcus aureus (MRSA), was not launched in Taiwan before 2019. The in vitro susceptibility data of ceftaroline against important Taiwanese pathogens are lacking.

METHODS

The in vitro susceptibility of ceftaroline against important pathogens collected from 2012 through 2018 were extracted from the Antimicrobial Testing Leadership and Surveillance program. Broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) to ceftaroline against all isolates.

RESULTS

During the study period, the in vitro data regarding isolates of S. aureus (n = 2049), Staphylococcus epidermidis (n = 185), Streptococcus pneumoniae (n = 334), Streptococcus pyogenes (n = 170), Haemophilus influenzae (n = 75), Haemophilus parainfluenzae (n = 10) and Klebsiella pneumoniae (n = 680) regardless of hospital sites of collection were analyzed. Among the S. aureus isolates studied, 19.4% showed MICs of 1 mg/L to ceftaroline, and 4.4% showed in vitro susceptible-dose dependent to ceftaroline (all MICs, 2 mg/L). Most of other Gram-positive cocci, all H. influenzae and H. parainfluenzae isolates were susceptible to ceftaroline. By contrast, about one-third (35.9%) of K. pneumoniae isolates, irrespective of infection sources, exhibited non-susceptibility to ceftaroline (MIC range, 0.015-256 mg/L; MIC50 and MIC90 values, 0.12 and 256 mg/L, respectively).

CONCLUSIONS

From the pharmacodynamic perspectives, the ceftaroline dosage of 600 mg as a 2-h intravenous infusion every 8 h is effective against all S. aureus and other Gram-positive isolates regardless of acquisition sites in Taiwan. Before ceftaroline is prescribed in treatment of the patient with Gram-negative infection, a cautious evaluation about patient's healthcare-associated factor is warranted.

Bacterial Targets of Antibiotics in Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most prevalent bacterial pathogens and continues to be a leading cause of morbidity and mortality worldwide. MRSA is a commensal bacterium in humans and is transmitted in both community and healthcare settings. Successful treatment remains a challenge, and a search for new targets of antibiotics is required to ensure that MRSA infections can be effectively treated in the future. Most antibiotics in clinical use selectively target one or more biochemical processes essential for S. aureus viability, e.g., cell wall synthesis, protein synthesis (translation), DNA replication, RNA synthesis (transcription), or metabolic processes, such as folic acid synthesis. In this review, we briefly describe the mechanism of action of antibiotics from different classes and discuss insights into the well-established primary targets in S. aureus. Further, several components of bacterial cellular processes, such as teichoic acid, aminoacyl-tRNA synthetases, the lipid II cycle, auxiliary factors of β-lactam resistance, two-component systems, and the accessory gene regulator quorum sensing system, are discussed as promising targets for novel antibiotics. A greater molecular understanding of the bacterial targets of antibiotics has the potential to reveal novel therapeutic strategies or identify agents against antibiotic-resistant pathogens.

β-Lactams against the Fortress of the Gram-Positive Staphylococcus aureus Bacterium

The biological diversity of the unicellular bacteria-whether assessed by shape, food, metabolism, or ecological niche-surely rivals (if not exceeds) that of the multicellular eukaryotes. The relationship between bacteria whose ecological niche is the eukaryote, and the eukaryote, is often symbiosis or stasis. Some bacteria, however, seek advantage in this relationship. One of the most successful-to the disadvantage of the eukaryote-is the small (less than 1 μm diameter) and nearly spherical Staphylococcus aureus bacterium. For decades, successful clinical control of its infection has been accomplished using β-lactam antibiotics such as the penicillins and the cephalosporins. Over these same decades S. aureus has perfected resistance mechanisms against these antibiotics, which are then countered by new generations of β-lactam structure. This review addresses the current breadth of biochemical and microbiological efforts to preserve the future of the β-lactam antibiotics through a better understanding of how S. aureus protects the enzyme targets of the β-lactams, the penicillin-binding proteins. The penicillin-binding proteins are essential enzyme catalysts for the biosynthesis of the cell wall, and understanding how this cell wall is integrated into the protective cell envelope of the bacterium may identify new antibacterials and new adjuvants that preserve the efficacy of the β-lactams.

Genome-Wide Association Studies for the Detection of Genetic Variants Associated With Daptomycin and Ceftaroline Resistance in Staphylococcus aureus

Background

As next generation sequencing (NGS) technologies have experienced a rapid development over the last decade, the investigation of the bacterial genetic architecture reveals a high potential to dissect causal loci of antibiotic resistance phenotypes. Although genome-wide association studies (GWAS) have been successfully applied for investigating the basis of resistance traits, complex resistance phenotypes have been omitted so far. For S. aureus this especially refers to antibiotics of last resort like daptomycin and ceftaroline. Therefore, we aimed to perform GWAS for the identification of genetic variants associated with DAP and CPT resistance in clinical S. aureus isolates.

Materials/methods

To conduct microbial GWAS, we selected cases and controls according to their clonal background, date of isolation, and geographical origin. Association testing was performed with PLINK and SEER analysis. By using in silico analysis, we also searched for rare genetic variants in candidate loci that have previously been described to be involved in the development of corresponding resistance phenotypes.

Results

GWAS revealed MprF P314L and L826F to be significantly associated with DAP resistance. These mutations were found to be homogenously distributed among clonal lineages suggesting convergent evolution. Additionally, rare and yet undescribed single nucleotide polymorphisms could be identified within mprF and putative candidate genes. Finally, we could show that each DAP resistant isolate exhibited at least one amino acid substitution within the open reading frame of mprF. Due to the presence of strong population stratification, no genetic variants could be associated with CPT resistance. However, the investigation of the staphylococcal cassette chromosome mec (SCCmec) revealed various mecA SNPs to be putatively linked with CPT resistance. Additionally, some CPT resistant isolates revealed no mecA mutations, supporting the hypothesis that further and still unknown resistance determinants are crucial for the development of CPT resistance in S. aureus.

Conclusion

We hereby confirmed the potential of GWAS to identify genetic variants that are associated with antibiotic resistance traits in S. aureus. However, precautions need to be taken to prevent the detection of spurious associations. In addition, the implementation of different approaches is still essential to detect multiple forms of variations and mutations that occur with a low frequency.

The Evolving Reduction of Vancomycin and Daptomycin Susceptibility in MRSA-Salvaging the Gold Standards with Combination Therapy

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with substantial morbidity and mortality. Vancomycin (VAN) has been used as the gold standard treatment for invasive MRSA infections for decades but, unfortunately, the reliance of VAN as the primary treatment option against these infections has led to a reduction in VAN susceptibility in MRSA isolates. Although daptomycin (DAP) is another common treatment option against invasive MRSA infections, it has been shown that the development of VAN resistance can lead to DAP nonsusceptibility. VAN or DAP backbone regimens in combination with other antibiotics has been advocated as an alternative approach to improve patient outcomes in VAN/DAP-susceptible infections, enhance outcomes in infections caused by isolates with reduced VAN/DAP susceptibility, and/or prevent the emergence of VAN/DAP resistance or further resistance. A peer-reviewed literature search was conducted using Medline, Google Scholar and PubMed databases. The primary purpose of this review is to describe the mechanisms and epidemiology of MRSA isolates with a reduction in VAN and/or DAP susceptibility, evaluate in vitro and in vivo literature describing combination therapy (CT) against MRSA isolates with reduced VAN and/or DAP susceptibility and describe studies involving the clinical outcomes of patients treated with CT against invasive MRSA infections.

High-yield production of active recombinant S. simulans lysostaphin expressed in E. coli in a laboratory bioreactor

Staphylococcus aureus (S. aureus), which has developed multidrug resistance, leads to many healthcare-associated infections resulting in significant medical and economic losses. Therefore, the development of new efficient strategies to deal with these bacteria has been gaining importance. Lysostaphin is a peptidoglycan hydrolase that has considerable potential as a bacteriocin. However, there have been few reported optimization and scale-up studies of the lysostaphin bioproduction process. Our preliminary results have revealed that the composition of auto-induction media at 30 °C increases the produced lysostaphin around 10-fold in shake flasks. In this study, achieving higher yields for recombinant lysostaphin in E. coli at a laboratory scale has been the aim, through the use of auto-induction media. Optimized medium composition and fermentation parameters were transferred to a laboratory-scale bioreactor. The tested conditions improved protein yields up to 184 mg/L in a 3 L stirred bioreactor and the productivity was improved 2-fold in comparison to previously published reports. Furthermore, this study also showed that lysostaphin is an effective bacteriocin on both commercially available and isolated S. aureus strains. These results will contribute to future larger-scale production of lysostaphin via the proposed fermentation conditions.

Efficacy and mechanism of actions of natural antimicrobial drugs

Microbial infections have significantly increased over the last decades, and the mortality rates remain unacceptably high. The emergence of new resistance patterns and the spread of new viruses challenge the eradication of infectious diseases. The declining efficacy of antimicrobial drugs has become a global public health problem. Natural products derived from natural sources, such as plants, animals, and microorganisms, have significant efficacy for the treatment of infectious diseases accompanied by less adverse effects, synergy, and ability to overcome drug resistance. As the Chinese female scientist Youyou Tu received the Nobel Prize for the antimalarial drug artemisinin, antimicrobial drugs developed from Traditional Chinese Medicine are expected to receive increasing attention again. This review summarizes the antimicrobial agents derived from natural products approved for nearly 20 years and describes their efficacy and mode of action. The aim of this unit is to review the current status of antimicrobial drugs from natural products in order to increase the value of natural products as a source of novel drug candidates for infectious diseases.

Generation of Stilbene Antimicrobials against Multiresistant Strains of Staphylococcus aureus through Biotransformation by the Enzymatic Secretome of Botrytis cinerea

The biotransformation of a mixture of resveratrol and pterostilbene was performed by the protein secretome of Botrytis cinerea. Several reaction conditions were tested to overcome solubility issues and to improve enzymatic activity. Using MeOH as cosolvent, a series of unusual methoxylated compounds was generated. The reaction was scaled-up, and the resulting mixture purified by semipreparative HPLC-PDA-ELSD-MS. Using this approach, 15 analogues were isolated in one step. Upon full characterization by NMR and HRMS analyses, eight of the compounds were new. The antibacterial activities of the isolated compounds were evaluated in vitro against the opportunistic pathogens Pseudomonas aeruginosa and Staphylococcus aureus. The selectivity index was calculated based on cytotoxic assays performed against human liver carcinoma cells (HepG2) and the human breast epithelial cell line (MCF10A). Some compounds revealed remarkable antibacterial activity against multidrug-resistant strains of S. aureus with moderate human cell line cytotoxicity.

Dalbavancin exposure in vitro selects for dalbavancin-non-susceptible and vancomycin-intermediate strains of methicillin-resistant Staphylococcus aureus

OBJECTIVES

Dalbavancin is a lipoglycopeptide active against methicillin-resistant Staphylococcus aureus (MRSA). Its long half-life (8.5-16 days) allows for once-weekly or single-dose treatments but could prolong the mutant selection window, promoting resistance and cross-resistance to related antimicrobials such as vancomycin. The objective of this study was to evaluate the capacity of post-distributional pharmacokinetic exposures of dalbavancin to select for resistance and cross-resistance in MRSA.

METHODS

We simulated average, post-distributional exposures of single-dose (1500 mg) dalbavancin (fCmax 9.9 μg/mL, β-elimination t_1/2 204 h) in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model for 28 days (672 h) against five MRSA strains and one methicillin-susceptible strain (MSSA). Samples were collected at least daily, and surviving colonies were enumerated and screened for resistance on drug-free and dalbavancin-supplemented medium respectively. Isolates from resistance screening plates were subjected to whole-genome sequencing (WGS) and susceptibly testing against dalbavancin, vancomycin, daptomycin, and six β-lactams with varying penicillin-binding protein (PBP) affinities.

RESULTS

Dalbavancin was bactericidal against most strains for days 1-4 before regrowth of less susceptible subpopulations occurred. Isolates with eight-fold increases in dalbavancin MIC were detected as early as day 4 but increased 64-128-fold in all models by day 28. Vancomycin and daptomycin MICs increased 4-16-fold, exceeding the susceptibly breakpoints for both antibiotics; β-lactam MICs generally decreased by two-to eight-fold, suggesting a dalbavancin-β-lactam seesaw effect, but increased by eight-fold or more in certain isolates. Resistant isolates carried mutations in a variety of genes, most commonly walKR, apt, stp1, and atl.

CONCLUSIONS

In our in vitro system, post-distributional dalbavancin exposures selected for stable mutants with reduced susceptibility to dalbavancin, vancomycin, and daptomycin, and generally increased susceptibility to β-lactams in all strains of MRSA tested. The clinical significance of these findings remains unclear, but created an opportunity to genotype a unique collection of dalbavancin-resistant strains for the first time. Mutations involved genes previously associated with vancomycin intermediate susceptibility and daptomycin non-susceptibility, most commonly walKR-associated genes.

Clearance of Persistent Staphylococcus aureus Bacteremia in a Preterm Neonate With the Use of Combination Cefazolin and Ertapenem

Late-onset sepsis caused by Staphylococcus aureus is a serious and relatively common complication encountered by preterm neonates in NICUs. Typical treatment regimens for invasive methicillin-sensitive Staphylococcus aureus (MSSA) include semisynthetic beta lactam antibiotics, such as nafcillin. This report describes the first use of a combination of cefazolin and ertapenem to successfully treat persistent MSSA bacteremia in a preterm neonate who failed traditional first-line therapy.

Prolonged Exposure to β-Lactam Antibiotics Reestablishes Susceptibility of Daptomycin-Nonsusceptible Staphylococcus aureus to Daptomycin

Daptomycin-nonsusceptible (DAP-NS) Staphylococcus aureus often exhibits gain-in-function mutations in the mprF gene (involved in positive surface charge maintenance). Standard β-lactams, although relatively inactive against methicillin-resistant S. aureus (MRSA), may prevent the emergence of mprF mutations and DAP-NS. We determined if β-lactams might also impact DAP-NS isolates already possessing an mprF mutation to revert them to DAP-susceptible (DAP-S) phenotypes and, if so, whether this is associated with specific penicillin-binding protein (PBP) targeting. This study included 25 DAP-S/DAP-NS isogenic, clinically derived MRSA bloodstream isolates. MICs were performed for DAP, nafcillin (NAF; PBP-promiscuous), cloxacillin (LOX; PBP-1), ceftriaxone (CRO; PBP-2), and cefoxitin (FOX; PBP-4). Three DAP-NS isolates were selected for a 28-day serial passage in subinhibitory β-lactams. DAP MICs and time-kill assays, host defense peptide (LL-37) susceptibilities, and whole-genome sequencing were performed to associate genetic changes with key phenotypic profiles. Pronounced decreases in baseline MICs were observed for NAF and LOX (but not for CRO or FOX) among DAP-NS versus DAP-S isolates ("seesaw" effect). Prolonged (28-d) β-lactam passage of three DAP-NS isolates significantly reduced DAP MICs. LOX was most impactful (∼16-fold decrease in DAP MIC; 2 to 0.125 mg/liter). In these DAP-NS isolates with preexisting mprF polymorphisms, accumulation of additional mprF mutations occurred with prolonged LOX exposures. This was associated with enhanced LL-37 killing activity and reduced surface charge (both mprF-dependent phenotypes). β-lactams that either promiscuously or specifically target PBP-1 have significant DAP "resensitizing" effects against DAP-NS S. aureus strains. This may relate to the acquisition of multiple mprF single nucleotide polymorphism (SNPs), which, in turn, affect cell envelope function and metabolism.

β-Lactams as promising anticancer agents: Molecular hybrids, structure activity relationships and potential targets

β-Lactam, commonly referred as azetidin-2-one, is a multifunctional building block for synthesizing β-amino ketones, γ-amino alcohols, and other compounds. Besides its well known antibiotic activity, this ring system exhibits a wide range of activities, attracting the attention of researchers. However, the structurally diverse β-lactam analogues as anticancer agents and their different molecular targets are poorly discussed. The purpose of this review is 3-fold: (1) to explore the molecular hybridization approach to design β-lactams hybrids as anticancer agents; (2) the structure activity relationship of the most active anticancer β-lactams and (3) to summarize their antitumor mechanisms.

Focusing the Lens on the CAMERA Concepts: Early Combination β-Lactam and Vancomycin Therapy in Methicillin-Resistant Staphylococcus aureus Bacteremia

Methicillin-resistant Staphylococcus aureus (MRSA) has grown to become a major burden on health care systems. The cumulation of limited therapeutic options and worsened patient outcomes with persistent MRSA bacteremia has driven research in optimizing its initial management. The guidelines published by the Infectious Diseases Society of America currently recommend combination therapy for refractory MRSA bacteremia, but the utility of combining antibiotics from the start of therapy is under investigation. The alternative strategy of early use of β-lactam antibiotics in combination with vancomycin upon initial MRSA bacteremia detection has shown promise. While this concept has gained international attention, providers should give this strategy serious consideration prior to implementation. The objective of this review is to examine retrospective and prospective evidence for early combination with vancomycin and β-lactam antibiotics, as well as explore potential consequences of combination therapy.

The Emerging Role of β-Lactams in the Treatment of Methicillin-Resistant Staphylococcus aureus Bloodstream Infections

Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSI) are associated with substantial morbidity and mortality. Monotherapy with first-line antimicrobials such as vancomycin (VAN; glycopeptide) and daptomycin (DAP; lipopeptide) are inadequate in some cases due to reduced antibiotic susceptibilities or therapeutic failure. In recent years, β-lactam antibiotics have emerged as a potential option for combination therapy with VAN and DAP that may meet an unmet therapeutic need for MRSA BSI. Ceftaroline (CPT), the only commercially available β-lactam in the United States with intrinsic in vitro activity against MRSA, has been increasingly studied in the setting of VAN and DAP failures. Novel combinations of first-line agents (VAN and DAP) with β-lactams have been the subject of many recent investigations due to in vitro findings such as the "seesaw effect," where β-lactam susceptibility may be improved in the presence of decreased glycopeptide and lipopeptide susceptibility. The combination of CPT and DAP, in particular, has become the focus of many scientific evaluations, due to intrinsic anti-MRSA activities and potent in vitro synergistic activity against various MRSA strains. This article reviews the available literature describing these innovative therapeutic approaches for MRSA BSI, focusing on preclinical and clinical studies, and evaluates the potential benefits and limitations of each strategy.

Penicillin binding protein 2a: An overview and a medicinal chemistry perspective

Antimicrobial resistance is an imminent threat worldwide. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the "superbug" family, manifesting resistance through the production of a penicillin binding protein, PBP2a, an enzyme that provides its transpeptidase activity to allow cell wall biosynthesis. PBP2a's low affinity to most β-lactams, confers resistance to MRSA against numerous members of this class of antibiotics. An Achilles' heel of MRSA, PBP2a represents a substantial target to design novel antibiotics to tackle MRSA threat via inhibition of the bacterial cell wall biosynthesis. In this review we bring into focus the PBP2a enzyme and examine the various aspects related to its role in conferring resistance to MRSA strains. Moreover, we discuss several antibiotics and antimicrobial agents designed to target PBP2a and their therapeutic potential to meet such a grave threat. In conclusion, we consider future perspectives for targeting MRSA infections.

Raman-activated sorting of antibiotic-resistant bacteria in human gut microbiota

The antibiotic‐resistant bacteria (ARB) and antibiotic‐resistant genes (ARGs) in human gut microbiota have significant impact on human health. While high throughput metagenomic sequencing reveals genotypes of microbial communities, the functionality, phenotype and heterogeneity of human gut microbiota are still elusive. In this study, we applied Raman microscopy and deuterium isotope probing (Raman–DIP) to detect metabolic active ARB (MA‐ARB) in situ at the single‐cell level in human gut microbiota from two healthy adults. We analysed the relative abundances of MA‐ARB under different concentrations of amoxicillin, cephalexin, tetracycline, florfenicol and vancomycin. To establish the link between phenotypes and genotypes of the MA‐ARB, Raman‐activated cell sorting (RACS) was used to sort MA‐ARB from human gut microbiota, and mini‐metagenomic DNA of the sorted bacteria was amplified, sequenced and analysed. The sorted MA‐ARB and their associated ARGs were identified. Our results suggest a strong relation between ARB in human gut microbiota and personal medical history. This study demonstrates that the toolkit of Raman–DIP, RACS and DNA sequencing can be useful to unravel both phenotypes and genotypes of ARB in human gut microbiota at the single‐cell level.

Imipenem-Cilastatin-Relebactam: A Novel β-Lactam-β-Lactamase Inhibitor Combination for the Treatment of Multidrug-Resistant Gram-Negative Infections

Imipenem-cilastatin-relebactam (IMI-REL) is a novel β-lactam-β-lactamase inhibitor combination recently approved for the treatment of complicated urinary tract infections (cUTIs) and complicated intraabdominal infections (cIAIs). Relebactam is a β-lactamase inhibitor with the ability to inhibit a broad spectrum of β-lactamases such as class A and class C β-lactamases, including carbapenemases. The addition of relebactam to imipenem restores imipenem activity against several imipenem-resistant bacteria, including Enterobacteriaceae and Pseudomonas aeruginosa. Clinical data demonstrate that IMI-REL is well tolerated and effective in the treatment of cUTIs and cIAIs due to imipenem-resistant bacteria. In a phase III trial comparing IMI-REL with imipenem plus colistin, favorable clinical response was achieved in 71% and 70% of patients, respectively. Available clinical and pharmacokinetic data support the approved dosage of a 30-minute infusion of imipenem 500 mg-cilastatin 500 mg-relebactam 250 mg every 6 hours, along with dosage adjustments based on renal function. In this review, we describe the chemistry, mechanism of action, spectrum of activity, pharmacokinetics and pharmacodynamics, and clinical efficacy, and safety and tolerability of this new agent. The approval of IMI-REL represents another important step in the ongoing fight against multidrug-resistant gram-negative pathogens.

Adjunctive ceftaroline in combination with daptomycin or vancomycin for complicated methicillin-resistant Staphylococcus aureus bacteremia after monotherapy failure

Background:

Methicillin-resistant Staphylococcus aureus bacteremia (MRSA-B) may fail to improve with standard monotherapy, particularly in patients with multifocal infection, incomplete source control, or persistent bacteremia. Synergy observed in vitro between ceftaroline (CPT) and daptomycin (DAP) or vancomycin (VAN) may translate into clinical benefit. Here, we describe our experience with DAP/CPT and VAN/CPT for complicated MRSA-B after monotherapy failure.

Methods:

Single-center, retrospective review of consecutive patients treated with DAP/CPT or VAN/CPT for MRSA-B after monotherapy failure from 1 January 2016 to 30 November 2018.

Results:

We identified 11 instances of combination therapy in 10 patients (DAP/CPT = 6, VAN/CPT = 5) with 1 patient receiving VAN/CPT followed by DAP/CPT. Rates of multifocal infection, incomplete source control, persistent bacteremia, and infective endocarditis were high (100%, 80%, 60%, and 60%, respectively). Combination therapy was initiated most commonly for persistent bacteremia (60%). When patients were persistently bacteremic, median preceding duration was 13 days and median time to clearance was 3 days. Total microbiologic cure rate was 100%. There were zero instances of bacteremia relapse at 30 days (30D) or 60 days (60D). All-cause 30D and 60D mortality rates were 11.1% and 33.3%, respectively.

Conclusions:

Combination therapy demonstrated success in diverse cases of refractory MRSA-B, including instances of persistent bacteremia paired with incomplete source control. Optimal timing and therapeutic cadence for combination therapy remain unclear. Our findings suggest that DAP/CPT and VAN/CPT can be considered for complicated MRSA bacteremia when other treatment options fail or are unavailable. We propose persistent bacteremia with incomplete source control to be a clinical niche particularly worthy of further investigation.

Genotypic analysis of Italian MRSA strains exhibiting low-level ceftaroline and ceftobiprole resistance

The aim of this study was to address the involvement of PBP mutations in the bactericidal activity to novel cephalosporins, alone and in combination with daptomycin, in not-related multidrug-resistant methicillin-resistant Staphylococcus aureus strains isolated during a nationwide Italian survey. MICs determination and time-killing assays were performed and mecA, pbp1, pbp2, pbp3, pbp4, and gdpP genes were sequenced. Ten strains showed low-level resistance to ceftaroline and ceftobiprole. PBP2a sequence analysis identified four different mutations (N146K; N204K; T235I; E239K) uniquely present in the non-penicillin-binding domain (nPBD). Epidemiologically, this resistance was associated with the most widespread MDR Italian clone ST228-SCCmecI-t001/t041, confirming its proclivity to accumulate mutations, and it is also associated to substitutions in the GdpP signaling protein, involved in the maintenance of di-AMP balance, recently associated with resistance to beta-lactams. Despite these mutations, both drugs retained their potent in vitro bactericidal activity and showed a synergistic effect towards difficult-to-treat isolates.

A comparative assessment of clinical, pharmacological and antimicrobial profile of novel anti-methicillin-resistant Staphylococcus aureus agent levonadifloxacin: Therapeutic role in nosocomial and community infections

Staphylococcus aureus is of significant clinical concern in both community- and hospital-onset infections. The key to the success of S. aureus as a pathogen is its ability to swiftly develop antimicrobial resistance. Methicillin-resistant S. aureus (MRSA) is not only resistant to nearly all beta-lactams but also demonstrates resistance to several classes of antibiotics. A high prevalence of MRSA is seen across worldwide. For many decades, vancomycin remained as gold standard antibiotic for the treatment of MRSA infections. In the past decades, linezolid, daptomycin, ceftaroline and telavancin received regulatory approval for the treatment of infections caused by resistant Gram-positive pathogens. Although these drugs may offer some advantages over vancomycin, they also have significant limitations. These includes vancomycin's slow bactericidal activity, poor lung penetration and nephrotxicity;linezolid therapy induced myelosuppression and high cost of daptomycin greatly limits their clinical use. Moreover, daptomycin also gets inactivated by lung naturally occurring surfactants. Thus, currently available therapeutic options are unable to provide safe and efficacious treatment for those patients suffering from hospital-acquired pneumonia, bloodstream infections (BSIs), bone and joint infections and diabetic foot infections (DFI). An unmet need also exists for a safe and efficacious oral option for switch-over convenience and community treatment. Herein, the review is intended to describe the supporting role of anti-staphylococcal antibiotics used in the management of S. aureus infections with a special reference to levonadifloxacin. Levonadifloxacin and its prodrug alalevonadifloxacin are novel benzoquinolizine subclass of quinolone with broad-spectrum of anti-MRSA activity. It has been recently approved for the treatment of complicated skin and soft-tissue infection as well as concurrent bacteraemia and DFI in India.

The ClpX chaperone controls autolytic splitting of Staphylococcus aureus daughter cells, but is bypassed by β-lactam antibiotics or inhibitors of WTA biosynthesis

β-lactam antibiotics interfere with cross-linking of the bacterial cell wall, but the killing mechanism of this important class of antibiotics is not fully understood. Serendipitously we found that sub-lethal doses of β-lactams rescue growth and prevent spontaneous lysis of Staphylococcus aureus mutants lacking the widely conserved chaperone ClpX, and we reasoned that a better understanding of the clpX phenotypes could provide novel insights into the downstream effects of β-lactam binding to the PBP targets. Super-resolution imaging revealed that clpX cells display aberrant septum synthesis, and initiate daughter cell separation prior to septum completion at 30°C, but not at 37°C, demonstrating that ClpX becomes critical for coordinating the S. aureus cell cycle as the temperature decreases. FtsZ localization and dynamics were not affected in the absence of ClpX, suggesting that ClpX affects septum formation and autolytic activation downstream of Z-ring formation. Interestingly, oxacillin antagonized the septum progression defects of clpX cells and prevented lysis of prematurely splitting clpX cells. Strikingly, inhibitors of wall teichoic acid (WTA) biosynthesis that work synergistically with β-lactams to kill MRSA synthesis also rescued growth of the clpX mutant, as did genetic inactivation of the gene encoding the septal autolysin, Sle1. Taken together, our data support a model in which Sle1 causes premature splitting and lysis of clpX daughter cells unless Sle1-dependent lysis is antagonized by β-lactams or by inhibiting an early step in WTA biosynthesis. The finding that β-lactams and inhibitors of WTA biosynthesis specifically prevent lysis of a mutant with dysregulated autolytic activity lends support to the idea that PBPs and WTA biosynthesis play an important role in coordinating cell division with autolytic splitting of daughter cells, and that β-lactams do not kill S. aureus simply by weakening the cell wall.

The bacterium Staphylococcus aureus is a major cause of human disease, and the rapid spread of S. aureus strains that are resistant to almost all β-lactam antibiotics has made treatment increasingly difficult. β-lactams interfere with cross-linking of the bacterial cell wall but the killing mechanism of this important class of antibiotics is not fully understood. Here we provide novel insight into this topic by examining a defined S. aureus mutant that has the unusual property of growing markedly better in the presence of β-lactams. Without β-lactams this mutant dies spontaneously at a high frequency due to premature separation of daughter cells during cell division. Cell death of the mutant can, however, be prevented either by exposure to β-lactam antibiotics or by inhibiting synthesis of wall teichoic acid, a major component of the cell wall in Gram-positive bacteria with a conserved role in activation of autolytic splitting of daughter cells. The finding that β-lactam antibiotics can prevent lysis of a mutant with deregulated activity of autolytic enzymes involved in daughter cell splitting, emphasizes the idea that β-lactams interfere with the coordination between cell division and daughter cell splitting, and do not kill S. aureus simply by weakening the cell wall.

Novel Antibiotics for Multidrug-Resistant Gram-Positive Microorganisms

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

Dalbavancin Alone and in Combination with Ceftaroline against Four Different Phenotypes of Staphylococcus aureus in a Simulated Pharmacodynamic/Pharmacokinetic Model

Glycopeptides such as vancomycin have been used as the first-line therapy against MRSA infections for over half a century. Reduced susceptibility and emergence of resistance to first-generation glycopeptides has led to development of second-generation lipoglycopeptide derivatives such as dalbavancin which hold broader ranges of activity and enhanced pharmacokinetic properties. We evaluated the MIC values for a total of 100 isolates, including 25 methicillin-resistant Staphylococcus aureus (MRSA), 25 heterogeneus vancomycin-intermediate S. aureus, 25 daptomycin nonsusceptible (DNS), and 25 vancomycin-intermediate S. aureus strains against dalbavancin, ceftaroline, and vancomycin alone and in combination. Dalbavancin was highly active against hVISA, DNS, and MRSA strains, achieving 96 to 100% susceptibility and 72% susceptibility against VISA strains. The combination of dalbavancin plus ceftaroline reduced dalbavancin MICs 62.5-fold and demonstrated enhanced killing against all four phenotypes in pharmacokinetic/pharmacodynamic models. Four strains of the aforementioned phenotypes were randomly chosen for pharmacodynamic/pharmacokinetic simulation models. Of interest, while both dalbavancin and vancomycin in combination with ceftaroline demonstrated significant improvement in glycopeptide fAUC/MIC values against these four phenotypes, the dalbavancin-ceftaroline combinations exhibited a 44- to 11,270-fold higher fAUC/MIC value in comparison to vancomycin-ceftaroline combinations. In addition, the time to detection limit was reduced for this combination (24 to 32 h) versus the vancomycin-ceftaroline combination (24 to 72h). To our knowledge, this is the first comprehensive study of dalbavancin and vancomycin combinations with ceftaroline. These data provide a novel approach for combating recalcitrant MRSA infections.

A Mini-Review on Ceftaroline in Bacteremia Patients with Methicillin-Resistant Staphylococcus aureus (MRSA) Infections

OBJECTIVE

The objective of this review is to describe the outcomes of patients treated with ceftaroline in the non-Food and Drug Administration (FDA) approved indication of methicillin-resistant Staphylococcus aureus (MRSA) infections in both pediatric and adult populations.

DATA SOURCES

A systematic overview was conducted by searching PubMed, Medline, and The Cochrane Library up to January 2019.

STUDY SELECTION AND DATA EXTRACTION

All English-language clinical trials and case reports related to the efficacy of ceftaroline in new, not-yet-approved FDA indications in MRSA infections in pediatric or adult populations.

DATA SYNTHESIS

In the case of MRSA bacteremia (MRSAB) infections, three different randomized studies in pediatric patients showed effectiveness of ceftaroline. When used in the case of adult populations with MRSA bacteremia, a small trial of 16 patients showed 50% clinical success in patients with acute bacterial skin and skin structure infections versus 63% clinical success in patients with community-acquired bacterial pneumonia. Another case series of six refractory case reports showed 50% clinical success of ceftaroline in patients with MRSA.

CONCLUSIONS

Although there are few case reports and limited data to date, ceftaroline fosamil should continue to be studied as an alternative therapy in MRSA infections in both pediatric and adult populations. Clinical success rates of ceftaroline were, in most cases, considered high when treating patients with MRSA infection. More clinical trials need to be studied. In the specific case of MRSA bacteremia, the treatment options remain few and ceftaroline should be extensively studied for the salvage treatment of MRSAB.

Use of Ceftaroline Fosamil in Osteomyelitis: CAPTURE Study Experience

BACKGROUND

Osteomyelitis is often challenging to treat. This analysis examined the clinical experience of patients with gram-positive osteomyelitis treated with ceftaroline fosamil in the phase 4 Clinical Assessment Program and Teflaro® Utilization Registry (CAPTURE) study.

METHODS

Data including patient demographics, past illnesses, risk factors, disease characteristics, antibiotic use, pathogens isolated, and clinical outcome were collected between September 2013 and February 2015 by review of randomly ordered patient charts from participating sites in the United States. Clinical success was defined as discontinuation of ceftaroline fosamil following clinical cure with no further need for antibiotics or clinical improvement with switch to another antibiotic treatment.

RESULTS

A total of 150 patients with gram-positive osteomyelitis were treated with ceftaroline fosamil. Most patients (117/150; 78.0%) were treated with 600 mg ceftaroline fosamil per dose; 143/150 patients (95.3%) received a dose every 12 h. The majority (89/150 patients; 59.3%) had been previously diagnosed with diabetes mellitus or peripheral arterial disease. Osteomyelitis was associated with hardware in 32/150 patients (21.3%). Methicillin-resistant and methicillin-susceptible Staphylococcus aureus (MRSA; MSSA) were the most commonly isolated pathogens, observed in 93/150 (62.0%) and 21/150 (14.0%) patients, respectively. Clinical success with ceftaroline fosamil therapy was observed in 139/150 (92.7%) patients overall, 81/89 (91.0%) patients with diabetes or peripheral arterial disease, and 18/20 (90.0%) patients who had hardware implanted before ceftaroline fosamil therapy (none had hardware removed during therapy). Patients who received prior antibiotic therapy or ceftaroline fosamil as monotherapy experienced clinical success rates of 93.9% (107/114) and 91% (91/100), respectively. Among patients who received concurrent antibiotic therapy, the clinical success rate was 96.0% (48/50). Patients who were infected with MRSA or MSSA had clinical success rates of 92.5% (86/93) and 100% (21/21), respectively. A total of 2/150 (1.3%) patients discontinued ceftaroline fosamil therapy because of adverse events.

CONCLUSIONS

Clinical success rates with ceftaroline fosamil were high in patients with gram-positive osteomyelitis, including those with diabetes or peripheral arterial disease and those with MRSA or MSSA.

Advances in pediatric antimicrobial agents development

PURPOSE OF REVIEW

Rising rates of multidrug-resistant organisms has necessitated the development of novel antimicrobials. In this review, we will highlight agents that have recently received licensure and those that are in clinical development.

RECENT FINDINGS

In recent years, development of novel antimicrobial agents has accelerated. Although most studies have targeted the adult population, studies in pediatric patients are underway. Adequately powered clinical trials are needed to establish the safety and role of these new drugs.

SUMMARY

The recent development of novel antimicrobials to combat multidrug-resistant organisms is encouraging; however, more studies in the pediatric population are needed.

In vitro and in vivo evaluation of cephalosporins for the treatment of Lyme disease

Background

Lyme disease accounts for >90% of all vector-borne disease cases in the United States and affect ~300,000 persons annually in North America. Though traditional tetracycline antibiotic therapy is generally prescribed for Lyme disease, still 10%–20% of patients treated with current antibiotic therapy still show lingering symptoms.

Methods

In order to identify new drugs, we have evaluated four cephalosporins as a therapeutic alternative to commonly used antibiotics for the treatment of Lyme disease by using microdilution techniques like minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). We have determined the MIC and MBC of four drugs for three Borrelia burgdorferi s.s strains namely CA8, JLB31 and NP40. The binding studies were performed using in silico analysis.

Results

The MIC order of the four drugs tested is cefoxitin (1.25 µM/mL) > cefamandole (2.5 µM/mL), > cefuroxime (5 µM/mL) > cefapirin (10 µM/mL). Among the drugs that are tested in this study using in vivo C3H/HeN mouse model, cefoxitin effectively kills B. burgdorferi. The in silico analysis revealed that all four cephalosporins studied binds effectively to B. burgdorferi proteins, SecA subunit penicillin-binding protein (PBP) and Outer surface protein E (OspE).

Conclusion

Based on the data obtained, cefoxitin has shown high efficacy killing B. burgdorferi at concentration of 1.25 µM/mL. In addition to it, cefoxitin cleared B. burgdorferi infection in C3H/HeN mice model at 20 mg/kg.

Comparative in vitro activity of ceftaroline and comparator agents against nosocomial Gram-negative and Gram-positive clinically significant bacterial isolates from patients in a teaching hospital in Kuwait

The objective was to test the in vitro activities of ceftaroline and comparator agents against clinical isolates of Gram-negative and Gram-positive bacteria. Isolates were identified with VITEK II. Susceptibility testing was with E test. A total of 1264 isolates were tested. Compared to other cephalosporins, ceftaroline demonstrated excellent in vitro activities (MIC90, ≤0.5 mg/L) against Escherichia coli, Salmonella spp. and Haemophilus influenzae. When matched with the comparator cephalosporins, ceftaroline demonstrated the greatest activity against methicillin-susceptible Staphylococcus aureus (MSSA), with MIC90 of 0.25 mg/L. Ceftaroline's MIC90s against both community-associated methicillin-resistant S. aureus (MRSA) and hospital-acquired MRSA were 0.5 and 1 mg/L, respectively. Major discrepancies were noted between E test and disc diffusion tests for ceftaroline only against 16 Gram-negative and 16 Gram-positive isolates. Ceftaroline demonstrated an excellent in vitro activity against the majority of clinically significant Gram-negative and Gram-positive isolates obtained from proven cases of bacterial infections.

Antibiotics-From There to Where?: How the antibiotic miracle is threatened by resistance and a broken market and what we can do about it

To fully appreciate the importance of antibiotics to everyday life, we must step back to the edge of the pre-antibiotic era when these lifesaving drugs were first introduced into clinical use.

New Antimicrobial Agents for the Treatment of Staphylococcal Infections in Children

Several new antimicrobial agents-daptomycin, ceftaroline, telavancin, dalbavancin, and-tedizolid have been approved for the treatment of staphylococcal infections, including methicillin-resistant Staphylococcus aureus (MRSA), in adults. Ceftaroline and daptomycin have been approved by the US Food and Drug Administration for use in children. Ceftaroline, a beta-lactam antibiotic with activity against MRSA, has been approved for treatment of community-acquired bacterial pneumonia and complicated skin and skin structure infections. Daptomycin has been approved for treatment of complicated skin and skin structure infections. In this article, we review the pharmacokinetics and pharmacodynamics of these antibiotics and available data on use in children.

Once-Daily Treatments for Methicillin-Susceptible Staphylococcus aureus Bacteremia: Are They Good Enough?

PURPOSE OF THE REVIEW

Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is a common cause of morbidity and mortality. First-line treatment requires frequent daily doses of an anti-staphylococcal beta-lactam. However, some physicians prescribe simpler once-daily regimens to improve compliance and improve healthcare utilization. We reviewed the literature regarding advantages, pitfalls, and efficacy of once-daily treatment options for MSSA bacteremia.

RECENT FINDINGS

Several once-daily antibiotics are effective in vitro against MSSA (ceftriaxone, daptomycin, telavancin, dalbavancin, oritavancin, tedizolid, ertapenem, fluoroquinolones, and others), but there is insufficient evidence to support these agents for MSSA bacteremia. Ceftriaxone may be considered for therapy completion with MSSA bacteremia from osteomyelitis, and daptomycin may be considered in patients who cannot tolerate first-line therapy. However, they have not been compared to traditional second-line agents, and their role remains uncertain. Current evidence does not support the use of once-daily treatment options for MSSA bacteremia.

Ceftaroline Activity Against Multidrug-Resistant Streptococcus pneumoniae from U.S. Medical Centers (2014) and Molecular Characterization of a Single Ceftaroline Nonsusceptible Isolate

Streptococcus pneumoniae isolates (2,614) were collected from patients at 135 U.S. Medical Centers during 2014. Isolates were evaluated for multidrug resistance to penicillin, ceftriaxone, erythromycin, tetracycline, trimethoprim-sulfamethoxazole, and levofloxacin. A single isolate (853008) demonstrated a ceftaroline nonsusceptible minimal inhibitory concentration (MIC) value, and it was subjected to molecular characterization. Ceftaroline (MIC50/90, ≤0.015/0.12 μg/ml) was eightfold more potent than ceftriaxone (MIC50/90, ≤0.06/1 μg/ml) against all isolates. For multidrug-resistant (MDR) isolates (28.8% of tested strains), ceftaroline (MIC50/90, 0.06/0.25 μg/ml; 99.9% susceptible) was the most active agent tested, being eightfold more active than ceftriaxone (MIC50/90, 0.25/2 μg/ml; 81.5% susceptible at MIC, ≤1 μg/ml) and 16-fold more active than penicillin (MIC50/90, 0.25/4 μg/ml; 78.5% susceptible at MIC, ≤2 μg/ml). Isolate 853008 was a single locus variant of sequence type 377 and serotype 35B. It had multiple substitutions in the penicillin-binding proteins (PBPs), mainly PBP2x, when compared with reference sequences from the R6 strain. Isolate 853008 showed 31 amino acid alterations in MurM. The in vitro data presented here confirm that ceftaroline potency against S. pneumoniae to be higher than other β-lactams, including against those isolates demonstrating ceftriaxone nonsusceptible and MDR phenotypes.

Ceftriaxone Etest non-susceptible methicillin susceptible Staphylococcus aureus time-kill responses

We determined the correlation between Etest and BMD MICs with bactericidal activity in MSSA blood isolates. Ceftriaxone was bactericidal in 36% and 9% of isolates exposed to the Etest and BMD MIC, respectively. With the sub-optimal activity of ceftriaxone, the Etest MIC may be a conservative method in identifying clinical utility.

Pharmacodynamics of Ceftaroline plus Ampicillin against Enterococcus faecalis in an In Vitro Pharmacokinetic/Pharmacodynamic Model of Simulated Endocardial Vegetations

The combination of ampicillin plus ceftaroline has been suggested to be more reliably synergistic against Enterococcus faecalis than ampicillin plus ceftriaxone using time-kill methods. The purpose of this study was to determine if this trend persists in a two-compartment model of simulated endocardial vegetations (SEV) using clinically relevant pharmacokinetic exposures of these antimicrobials. Three clinically derived E. faecalis strains were included in the study. The MICs of study antimicrobials were determined by broth microdilution. Simulations of ampicillin (2 g every 4 h [q4h]; maximum concentration of drug in serum [Cmax], 72.4 mg/liter; half-life [t1/2], 1.9 h), ceftaroline-fosamil (600 mg q8h; Cmax, 21.3 mg/liter; t1/2, 2.66 h), ceftriaxone (Cmax, 257 mg/liter; t1/2, 8 h), and ampicillin plus ceftaroline and ampicillin plus ceftriaxone were evaluated against 3 strains of E. faecalis isolated from patients with endocarditis in an in vitro PK/PD SEV model over 72 h, with a starting inoculum of ∼9 log10 CFU/g. All strains were susceptible to ampicillin (MIC, ≤2 mg/liter). Ceftaroline MICs varied from 2 to 16 mg/liter. All strains had ceftriaxone MICs of 256 mg/liter. W04 and W151 exhibited high-level aminoglycoside resistance but W07 did not. Ampicillin plus ceftaroline resulted in significantly greater reductions in CFU per gram by 72 h than ampicillin for all strains (P ≤ 0.025) than ampicillin plus ceftriaxone for W04 (P = 0.019) but not W07 or W151 (P ≥ 0.15). A 4-fold increase in ampicillin MIC was observed for W07 at 72 h, but this was prevented by the addition of ceftaroline or ceftriaxone. The combination of ampicillin plus ceftaroline appears to be at least as efficacious as ampicillin plus ceftriaxone and may lead to improved activity against some strains of E. faecalis, but these differences may be small and the clinical significance should not be overestimated.