In vitro activity of telavancin and occurrence of vancomycin heteroresistance in isolates from patients enrolled in phase 3 clinical trials of hospital-acquired pneumonia

Global distribution of heterogeneous vancomycin-intermediate Staphylococcus aureus strains (1997-2021): a systematic review and meta-analysis

BACKGROUND

Heterogeneous vancomycin-intermediate Staphylococcus aureus is considered one of the main causes in treatment failure of vancomycin, which leads to poor clinical outcomes. Herein, we comprehensively evaluated characteristics such as global prevalence, trend, and genetic backgrounds of these strains.

METHODS

In this study, we conducted a meta-analysis based on PRISMA checklist 2020. In the beginning, global databases were searched to achieve the studies related to the prevalence of hVISA in clinical isolates of methicillin-resistant Staphylococcus aureus. After retrieving the eligible English studies, the prevalence of hVISA isolates and their trend changes were assessed using event rate with 95% confidence intervals.

RESULTS

In the present study, the prevalence of 114 801 MRSA isolates (of 124 studies) was 64%. According to our results, although the frequency of infection with hVISA is increasing in recent years, there is not a significant difference between Asian countries and Europe/America (6.1% vs. 6.8%). In addition, infection with hVISA bacteria was higher in bacteraemic patients than other infections (9.4% vs. 5.5%), which increases hospitalization, treatment costs, and mortality in these patients. Isolates harbouring SCCmec types II and III are most common genotypes in hVISA strains.

CONCLUSIONS

The prevalence of hVISA is increasing, which will reduce the effectiveness of vancomycin treatment in the coming years. The presence of hVISA stains in blood samples was higher than the other samples, which is threatening for bacteraemic patients. The results of the current study indicate a universal program to identify and control the spread of such strains in nosocomial infections.

Telavancin activity tested against Gram-positive clinical isolates from European, Russian and Israeli hospitals (2011-2013) using a revised broth microdilution testing method: redefining the baseline activity of telavancin

OBJECTIVES

To reassess the activity of telavancin when tested against Gram-positive clinical pathogens recovered from hospitalized patients in European and adjacent regions using a revised broth microdilution method.

METHODS

11 601 consecutive, non-duplicate isolates originating from 36 institutions among 18 countries recovered between 2011 and 2013 were tested for susceptibility using a revised broth microdilution method for telavancin. Interpretive telavancin breakpoints appropriate for the method were those recently approved by the FDA and EUCAST, as available.

RESULTS

Telavancin (MIC50/90, 0.03/0.06 mg/l; 100.0% susceptible) was equally potent against methicillin-susceptible ((MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus. All Enterococcus faecalis was susceptible to telavancin (MIC50/90, 0.12/0.12 mg/l) and inhibited at the susceptibility breakpoint (i.e. ≤ 0.25 mg/l), except for VanA-phenotype vancomycin-resistant isolates (telavancin MIC, >1 mg/l). Telavancin ( ≤ 0.015/0.03 mg/l) was active against vancomycin-susceptible Enterococcus faecium, while higher MIC values were obtained for VanA strains. Telavancin (both MIC50 and MIC90, ≤ 0.015 mg/l) was potent against Streptococcus pneumoniae, beta-haemolytic streptococci (MIC50/90, ≤ 0.015/0.06 mg/l) and viridans group streptococci (MIC50/90, ≤ 0.015/0.03 mg/l).

CONCLUSIONS

Telavancin exhibited potent activity against this contemporary (2011-2013) collection of organisms, inhibiting indicated pathogens at or below the FDA/EUCAST-approved breakpoints for susceptibility. VanA-phenotype enterococci were less susceptible to telavancin, a feature observed using the previous testing method. These results redefine telavancin's activity against isolates from Europe.

Approved Glycopeptide Antibacterial Drugs: Mechanism of Action and Resistance

The glycopeptide antimicrobials are a group of natural product and semisynthetic glycosylated peptides that show antibacterial activity against Gram-positive organisms through inhibition of cell-wall synthesis. This is achieved primarily through binding to the d-alanyl-d-alanine terminus of the lipid II bacterial cell-wall precursor, preventing cross-linking of the peptidoglycan layer. Vancomycin is the foundational member of the class, showing both clinical longevity and a still preferential role in the therapy of methicillin-resistant Staphylococcus aureus and of susceptible Enterococcus spp. Newer lipoglycopeptide derivatives (telavancin, dalbavancin, and oritavancin) were designed in a targeted fashion to increase antibacterial activity, in some cases through secondary mechanisms of action. Resistance to the glycopeptides emerged in delayed fashion and occurs via a spectrum of chromosome- and plasmid-associated elements that lead to structural alteration of the bacterial cell-wall precursor substrates.

Potential role for telavancin in bacteremic infections due to gram-positive pathogens: focus on Staphylococcus aureus

Staphylococcus aureus bacteremia (SAB) is one of the most common serious bacterial infections and the most frequent invasive infection due to methicillin-resistant S. aureus (MRSA). Treatment is challenging, particularly for MRSA, because of limited treatment options. Telavancin is a bactericidal lipoglycopeptide antibiotic that is active against a range of clinically relevant gram-positive pathogens including MRSA. In experimental animal models of sepsis telavancin was shown to be more effective than vancomycin. In clinically evaluable patients enrolled in a pilot study of uncomplicated SAB, cure rates were 88% for telavancin and 89% for standard therapy. Among patients with infection due to only gram-positive pathogens enrolled in the 2 phase 3 studies of telavancin for treatment of hospital-acquired pneumonia, cure rates for those with bacteremic S. aureus pneumonia were 41% (9/22, telavancin) and 40% (10/25, vancomycin) with identical mortality rates. These data support further evaluation of telavancin in larger, prospective studies of SAB.

Aetiology of hospital-acquired pneumonia and trends in antimicrobial resistance

PURPOSE OF REVIEW

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) continue to present very significant diagnostic and management challenges. The development, introduction and use of a wider range of immunosuppressive therapies are leading to a broader spectrum of microorganisms causing HAP and VAP. The persistent clinical dilemma regarding their cause is that detection of a microorganism from a respiratory tract sample does not necessarily signify it is the causative agent of the pneumonia. The ever-increasing antibiotic resistance problem means that HAP and VAP are becoming progressively more difficult to treat. In this article, we review the cause, antimicrobial resistance, diagnosis and treatment of HAP and VAP and encapsulate recent developments and concepts in this rapidly moving field.

RECENT FINDINGS

Although the microbial causes of HAP and VAP remain at present similar to those identified in previous studies, there are marked geographical differences. Resistance rates among Gram-negative bacteria are continually increasing, and for any species, multiresistance is the norm rather than the exception. The development and introduction of rapid point-of-care diagnostics may improve understanding of the cause of HAP and VAP and has immense potential to influence the treatment and clinical outcomes in HAP/VAP, with patients likely to receive much faster, microorganism-specific treatment with obvious downstream improvements to clinical outcome and antimicrobial stewardship.

SUMMARY

We describe recent trends in aetiology of HAP and VAP and recent trends in antimicrobial resistance, including resistance mechanisms causing particular concern. The potential for novel molecular diagnostics to revolutionize the diagnosis and treatment of HAP/VAP is discussed.

Treatment of Gram-positive infections in critically ill patients

Gram-positive bacteria to include methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible Staphylococcus aureus (MSSA), and enterococci, to include vancomycin-resistant enterococci (VRE), display a remarkable array of resistance and virulence factors, which have contributed to their prominent role in infections of the critically ill. Over the last three decades infections with these pathogens has increased as has their overall resistance to available antimicrobial agents. This has led to the development of a number of new antibiotics for the treatment of Gram-positive bacteria. At present, it is important that clinicians recognize the changing resistance patterns and epidemiology of Gram-positive bacteria as these factors may impact patient outcomes. The increasing range of these pathogens, such as the emergence of community-associated MRSA clones, emphasizes that all specialties of physicians treating infections should have a good understanding of the infections caused by Gram-positive bacteria in their area of practice. When initiating empiric antibiotics, it is of vital importance that this therapy be timely and appropriate, as delays in treatment are associated with adverse outcomes. Although vancomycin has traditionally been considered a first-line therapy for serious MRSA infections, multiple concerns with this agent have opened the door for alternative agents demonstrating efficacy in this role. Similarly, the expansion of VRE as a pathogen in the ICU setting has required the development of agents targeting this important pathogen.

Baseline activity of telavancin against Gram-positive clinical isolates responsible for documented infections in U.S. hospitals (2011-2012) as determined by the revised susceptibility testing method

Telavancin had MIC50 and MIC90 values of 0.03 and 0.06 μg/ml (100.0% susceptible), respectively, against methicillin-resistant and -susceptible Staphylococcus aureus. Telavancin was active against vancomycin-susceptible Enterococcus faecalis (MIC50/90, 0.12/0.12 μg/ml; 100% susceptible) and Enterococcus faecium (MIC50/90, 0.03/0.06 μg/ml), while higher MIC values were obtained against vancomycin-resistant E. faecium (MIC50/90, 1/2 μg/ml) and E. faecalis (MIC50/90, >2/>2 μg/ml). Streptococci showed telavancin modal MIC results of ≤ 0.015 μg/ml, except against Streptococcus agalactiae (i.e., 0.03 μg/ml). This study reestablishes the telavancin spectrum of activity against isolates recovered from the United States (2011-2012) using the revised broth microdilution method.

Treatment of infections due to resistant Staphylococcus aureus

This chapter reviews data on the treatment of infections caused by drug-resistant Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). This review covers findings reported in the English language medical literature up to January of 2013. Despite the emergence of resistant and multidrug-resistant S. aureus, we have seven effective drugs in clinical use for which little resistance has been observed: vancomycin, quinupristin-dalfopristin, linezolid, tigecycline, telavancin, ceftaroline, and daptomycin. However, vancomycin is less effective for infections with MRSA isolates that have a higher MIC within the susceptible range. Linezolid is probably the drug of choice for the treatment of complicated MRSA skin and soft tissue infections (SSTIs); whether it is drug of choice in pneumonia remains debatable. Daptomycin has shown to be non-inferior to either vancomycin or β-lactams in the treatment of staphylococcal SSTIs, bacteremia, and right-sided endocarditis. Tigecycline was also non-inferior to comparator drugs in the treatment of SSTIs, but there is controversy about whether it is less effective than other therapeutic options in the treatment of more serious infections. Telavancin has been shown to be non-inferior to vancomycin in the treatment of SSTIs and pneumonia, but has greater nephrotoxicity. Ceftaroline is a broad-spectrum cephalosporin with activity against MRSA; it is non-inferior to vancomycin in the treatment of SSTIs. Clindamycin, trimethoprim-sulfamethoxazole, doxycycline, rifampin, moxifloxacin, and minocycline are oral anti-staphylococcal agents that may have utility in the treatment of SSTIs and osteomyelitis, but the clinical data for their efficacy is limited. There are also several drugs with broad-spectrum activity against Gm-positive organisms that have reached the phase II and III stages of clinical testing that will hopefully be approved for clinical use in the upcoming years: oritavancin, dalbavancin, omadacycline, tedizolid, delafloxacin, and JNJ-Q2. Thus, there are currently many effective drugs to treat resistant S. aureus infections and many promising agents in the pipeline. Nevertheless, S. aureus remains a formidable adversary, and despite our deep bullpen of potential therapies, there are still frequent treatment failures and unfortunate clinical outcomes. The following discussion summarizes the clinical challenges presented by MRSA, the clinical experience with our current anti-MRSA antibiotics, and the gaps in our knowledge on how to use these agents to most effectively combat MRSA infections.