In Vitro Activity of Telavancin Against Clinically Important Gram-Positive Pathogens from 69 U.S. Medical Centers (2015): Potency Analysis by U.S. Census Divisions

Difficult-to-Treat Pathogens: A Review on the Management of Multidrug-Resistant Staphylococcus epidermidis

Multidrug-resistant Staphylococcus epidermidis (MDRSE) is responsible for difficult-to-treat infections in humans and hospital-acquired-infections. This review discusses the epidemiology, microbiology, diagnosis, and treatment of MDRSE infection and identifies knowledge gaps. By using the search term "pan resistant Staphylococcus epidermidis" OR "multi-drug resistant Staphylococcus epidermidis" OR "multidrug-resistant lineages of Staphylococcus epidermidis", a total of 64 records have been identified from various previously published studies. The proportion of methicillin resistance in S. epidermidis has been reported to be as high as 92%. Several studies across the world have aimed to detect the main phylogenetic lineages and antibiotically resistant genes through culture, mass spectrometry, and genomic analysis. Molecular biology tools are now available for the identification of S. epidermidis and its drug resistance mechanisms, especially in blood cultures. However, understanding the distinction between a simple colonization and a bloodstream infection (BSI) caused by S. epidermidis is still a challenge for clinicians. Some important parameters to keep in mind are the number of positive samples, the symptoms and signs of the patient, the comorbidities of the patient, the presence of central venous catheter (CVC) or other medical device, and the resistance phenotype of the organism. The agent of choice for empiric parenteral therapy is vancomycin. Other treatment options, depending on different clinical settings, may include teicoplanin, daptomycin, oxazolidinones, long-acting lipoglycopeptides, and ceftaroline. For patients with S. epidermidis infections associated with the presence of an indwelling device, assessment regarding whether the device warrants removal is an important component of management. This study provides an overview of the MDRSE infection. Further studies are needed to explore and establish the most correct form of management of this infection.

Clinical Response and Hospital Costs of Therapeutic Drug Monitoring for Vancomycin in Elderly Patients

Cost-effectiveness analysis has been widely used to assess and compare the costs and benefits of a clinical service. The cost-effectiveness of vancomycin therapeutic drug monitoring (TDM) has not been studied in the elderly, who are susceptible to vancomycin-induced adverse effects. This study was performed to evaluate if vancomycin TDM is cost-effective in elderly patients in the Republic of Korea. Using the electronic medical records at a tertiary university hospital, we performed a retrospective observational study to evaluate the cost-effectiveness of vancomycin TDM in 850 elderly patients who underwent vancomycin TDM with an appropriate, recommended dosing regimen and 1094 elderly patients who did not. Cost-effectiveness variables such as clinical outcomes and medical expenses were evaluated using univariate and multivariate analyses. The TDM group spent significantly less than the non-TDM group per patient for total medical expenses (by USD 841.40) and medication expenses (by USD 16.70). However, no significant difference was noted between the TDM and non-TDM groups in clinical outcomes such as microbiological cure, prevention of nephrotoxicity, or reduced mortality, irrespective of admission to the intensive care unit. Vancomycin TDM in elderly patients was associated with economic benefits, but not with better clinical outcomes.

Repurposing of the Tamoxifen Metabolites to Treat Methicillin-Resistant Staphylococcus epidermidis and Vancomycin-Resistant Enterococcus faecalis Infections

Repurposing drugs provides a new approach to the fight against multidrug-resistant (MDR) bacteria. We have reported that three major tamoxifen metabolites, N-desmethyltamoxifen (DTAM), 4-hydroxytamoxifen (HTAM), and endoxifen (ENDX), presented bactericidal activity against Acinetobacter baumannii and Escherichia coli. Here, we aimed to analyze the activity of a mixture of the three tamoxifen metabolites against methicillin-resistant Staphylococcus epidermidis (MRSE) and Enterococcus species. MRSE (n = 17) and Enterococcus species (Enterococcus faecalisn = 8 and Enterococcus faeciumn = 10) strains were used. MIC of the mixture of DTAM, HTAM, and ENDX and that of vancomycin were determined by microdilution assay. The bactericidal activity of the three metabolites together and of vancomycin against MRSE (SE385 and SE742) and vancomycin-resistant E. faecalis (EVR1 and EVR2) strains was determined by time-kill curve assays. Finally, changes in membrane permeability of SE742 and EVR1 strains were analyzed using fluorescence assays. MIC₉₀ of tamoxifen metabolites was 1 mg/liter for MRSE strains and 2 mg/liter for E. faecalis and E. faecium strains. In the time-killing assays, tamoxifen metabolites mixture showed bactericidal activity at 4× MIC for MRSE (SE385 and SE742) and at 2× MIC and 4× MIC for E. faecalis (EVR1 and EVR2) strains, respectively. SE385 and EVR2 strains treated with the tamoxifen metabolites mixture presented higher membrane permeabilization. Altogether, these results showed that tamoxifen metabolites presented antibacterial activity against MRSE and vancomycin-resistant E. faecalis, suggesting that tamoxifen metabolites might increase the arsenal of drug treatments against these bacterial pathogens.

IMPORTANCE The development of new antimicrobial therapeutic strategies requires immediate attention to avoid the tens of millions of deaths predicted to occur by 2050 as a result of MDR bacterial infections. In this study, we assessed the antibacterial activity of three major tamoxifen metabolites, N-desmethyltamoxifen (DTAM), 4-hydroxytamoxifen (HTAM), and endoxifen (ENDX), against methicillin-resistant Staphylococcus epidermidis (MRSE) and Enterococcus spp. (E. faecalis and E. faecium). We found that the tamoxifen metabolites have antibacterial activity against MRSE, E. faecalis, and E. faecium strains by presenting MIC₉₀ between 1 and 2 mg/liter and bactericidal activity over 24 h. In addition, this antibacterial activity is paralleled by an increased membrane permeability of these strains. Our results showed that tamoxifen metabolites might be potentially used as a therapeutic alternative when treating MRSE and E. faecalis strains in an animal model of infection.

Clinical efficacy and safety of novel lipoglycopeptides in the treatment of acute bacterial skin and skin structure infections: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

This systematic review and meta-analysis aimed to investigate the clinical efficacy and safety of novel lipoglycopeptides in treating acute bacterial skin and skin structure infections (ABSSSIs).

RESEARCH DESIGN AND METHODS

PubMed, Embase, Cochrane Central Register of Controlled Trials, Turning Research into Practice, and ClinicalTrials.gov were searched from inception to 20 May 2021. Randomized controlled trials (RCTs) comparing the clinical efficacy and safety of lipoglycopeptides with other comparators in treating adult patients with ABSSSIs were included. The primary outcome was clinical response.

RESULTS

Eight RCTs (6416 patients; lipoglycopeptides: 3359, comparators: 3057) were enrolled. Clinical response rate was not significantly different between lipoglycopeptides and comparators at early-clinical-evaluation (odds ratio [95% confidence interval]: 1.01 [0.85-1.20], I² = 34%), end-of-treatment (0.94 [0.80-1.11], I² = 0%), and test-of-cure (1.05 [0.85-1.30], I² = 0%). Lipoglycopeptides showed a similar overall microbiological eradication rate (1.12 [0.90-1.38], I² = 21%) but a borderline higher microbiological eradication rate for methicillin-resistant Staphylococcus aureus (1.37 [1.00-1.86], I² = 0%) than the comparators. Lipoglycopeptides were not associated with a higher risk than comparators.

CONCLUSIONS

Lipoglycopeptides can achieve similar clinical and microbiological responses to other comparators in treating ABSSSIs. In addition, lipoglycopeptides are as tolerable as their comparators.

Molecular Characterization of Staphylococcus aureus Obtained from Blood Cultures of Paediatric Patients Treated in a Tertiary Care Hospital in Mexico

Purpose

Staphylococcus aureus is one of the main causative agents of hospital-acquired (HA) infections. In Mexico, information about the characteristics of clinical S. aureus isolates is limited. Our aim was to characterize S. aureus strains obtained from blood cultures of paediatric patients treated in a tertiary care hospital.

Materials and Methods

We analysed 249 S. aureus isolates over the period from 2006 to 2019, and their resistance profiles were determined. The isolates were classified into methicillin-resistant S. aureus (MRSA) or methicillin-sensitive S. aureus (MSSA). Staphylococcal cassettes chromosome mec (SCCmec) were detected. Virulence genes (cna, clfA, clfB, eta, etb, fnbA, fnbB, hla, pvl, sec, and tsst) were amplified, and their clonal relationships were established by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and clonal complex (CC) typing. We reviewed one hundred medical files to collect clinical information.

Results

Thirty-eight percent of the isolates were MRSA and showed an expanded profile of resistance to other non-beta-lactam antibiotics, while MSSA strains presented a reduced resistance profile. SCCmec-II was the most frequent element (86.3%). Eight virulence factors were detected in MSSA and six in MRSA. The pvl gene was detected in four MRSA-SCCmec-IV isolates (P≤0.0001). MRSA isolates were distributed among 14 clones and were classified into 15 sequence types (ST); the most frequent was ST1011 (17%). The most common CC in MRSA was CC5 (69%, P≤0.0001), and in MSSA, it was CC30 (30%, P≤0.0001). Eighty-seven percent of MRSA isolates were HA-MRSA, and 13% were community-acquired MRSA (CA-MRSA). Of 21 HA-MRSA isolates, 17 had SCCmec-II, while two CA-MRSA isolates had SCCmec-IV. Of MSSA isolates, 77% were derived from HA infections and 23% from CA infections.

Conclusion

MSSA isolates had more virulence factors. MRSA isolates were resistant to more non-beta-lactam antibiotics, and those with SCCmec-IV expressed a greater variety of virulence factors. Most S. aureus isolates belonged to CC5.

Regional analysis of telavancin and comparator antimicrobial activity against multidrug-resistant Staphylococcus aureus collected in the USA 2014-2016

OBJECTIVES

The in vitro antimicrobial activities of telavancin and comparator antimicrobials were evaluated against recent Staphylococcus aureus (S. aureus) clinical isolates collected in the United States of America (USA).

METHODS

A total of 15882 S. aureus isolates were collected (2014-2016) as part of the SENTRY Antimicrobial Surveillance Program from sites located in all US Census Bureau divisions. Broth microdilution MIC values were measured using current reference methods. Data were stratified by year and census division, and resistance rates were analysed for significant trends. Previously published data on methicillin-resistant S. aureus (MRSA) and multidrug-resistant (MDR) MRSA isolates (collected 2011-2013) were merged with the current isolate set to examine longer term resistance trends.

RESULTS

Telavancin antimicrobial activity against MRSA and MDR MRSA isolates (MIC_50/90 values, 0.03/0.06μg/mL for both subsets) remained unchanged over the 3-year surveillance period, and all isolates were susceptible to telavancin. No difference in telavancin activity was noted when MIC data were stratified by year or US Census Bureau division. When merged data (2011-2016) were analysed, the MRSA rate decreased for the entire USA and six individual census divisions, although the overall rate remained considerable. The overall US MDR MRSA rate also remained considerable and was unchanged from 2011-2016.

CONCLUSIONS

The sustained potent activity of telavancin against US S. aureus isolates (100% susceptible) and the high rates of MRSA and MDR MRSA in the USA support the continued use of telavancin to treat indicated serious infections caused by S. aureus.

Developments in Glycopeptide Antibiotics

Glycopeptide antibiotics (GPAs) are a key weapon in the fight against drug resistant bacteria, with vancomycin still a mainstream therapy against serious Gram-positive infections more than 50 years after it was first introduced. New, more potent semisynthetic derivatives that have entered the clinic, such as dalbavancin and oritavancin, have superior pharmacokinetic and target engagement profiles that enable successful treatment of vancomycin-resistant infections. In the face of resistance development, with multidrug resistant (MDR) S. pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA) together causing 20-fold more infections than all MDR Gram-negative infections combined, further improvements are desirable to ensure the Gram-positive armamentarium is adequately maintained for future generations. A range of modified glycopeptides has been generated in the past decade via total syntheses, semisynthetic modifications of natural products, or biological engineering. Several of these have undergone extensive characterization with demonstrated in vivo efficacy, good PK/PD profiles, and no reported preclinical toxicity; some may be suitable for formal preclinical development. The natural product monobactam, cephalosporin, and β-lactam antibiotics all spawned multiple generations of commercially and clinically successful semisynthetic derivatives. Similarly, next-generation glycopeptides are now technically well positioned to advance to the clinic, if sufficient funding and market support returns to antibiotic development.