The role of methicillin-resistant Staphylococcus aureus in skin and soft tissue infections

Draft genome sequence data of methicillin-resistant Staphylococcus aureus, strain 4233

Staphylococcus aureus is a conditionally pathogenic microorganism and one of the main causative agents of antibiotic resistant nosocomial infections. In immunocompromised people, S. aureus infection can cause folliculitis, furuncles, impetigo, osteomyelitis, septic arthritis, sepsis, endocarditis, pneumonia and meningitis. In the presented work, sequencing of a methicillin-resistant S. aureus, strain 4233, was performed on the Illumina MiSeq platform, followed by bioinformatics processing and gene annotation using SPAdes, RAST and CARD programs and databases. The submitted genome is a total of 2,790,390 bp long and contains 2759 genes, including 82 RNA genes. 33 % of the genes are functionally significant and represent 25 functional groups. Fourteen genes encoding resistance factors to 14 different types of antibacterial drugs were predicted. The information provided on the genome of S. aureus, strain 4233 will be of value in investigating the evolution and formation of antibiotic-resistant forms of S. aureus.

The Effectiveness of Polyhexanide in Treating Wound Infections Due to Methicillin-Resistant Staphylococcus Aureus: A Prospective Analysis

Purpose

Polyhexanide is a safe and effective wound care antiseptic commonly used in clinics as wound rinsing solution and gel. However, the efficacy of Polyhexanide in treatment of wound infected with MRSA (methicillin-resistant Staphylococcus aureus) is unknown. The aim of this study is to assess the effectiveness of polyhexanide with povidone iodine in treating wound infected with MRSA.

Patients and Methods

A prospective analysis of 62 patients with wound infections, who were admitted to our department from 2016 to 2020, was conducted in order to assess the efficacy of different treatment approaches. The patients were divided into two groups: the experimental group and the control group. In the experimental group, 30 patients underwent treatment with a combination of diluted povidone iodine and polyhexanide immersion. Conversely, in the control group, 32 patients received treatment with diluted povidone iodine along with systemic antibiotic therapy. The time required for dressing changes, bacterial clearance rates, and the Bates-Jasen wound assessment tool (BWAT) scores were utilized as indicators to evaluate the effectiveness of the treatments.

Results

In our study, the findings indicated that the experimental group exhibited a lesser number of days for the bacteria culture to turn negative compared to the control group, with statistical significance (p<0.05). Furthermore, the decline in the BWAT score was significantly greater in the experimental group than in the control group (p<0.05). However, no significant differences were observed in terms of dressing times and wound coverage between the two groups (p>0.05).

Conclusion

Polyhexanide combined with povidone iodine can effectively remove MRSA infection in wounds and reduce antibiotic dosages.

Small Molecule Attenuates Bacterial Virulence by Targeting Conserved Response Regulator

Antibiotic tolerance within a biofilm community presents a serious public health challenge. Here, we report the identification of a 2-aminoimidazole derivative that inhibits biofilm formation by two pathogenic Gram-positive bacteria, Streptococcus mutans and Staphylococcus aureus. In S. mutans, the compound binds to VicR, a key response regulator, at the N-terminal receiver domain, and concurrently inhibits expression of vicR and VicR-regulated genes, including the genes that encode the key biofilm matrix producing enzymes, Gtfs. The compound inhibits S. aureus biofilm formation via binding to a Staphylococcal VicR homolog. In addition, the inhibitor effectively attenuates S. mutans virulence in a rat model of dental caries. As the compound targets bacterial biofilms and virulence through a conserved transcriptional factor, it represents a promising new class of anti-infective agents that can be explored to prevent or treat a host of bacterial infections. IMPORTANCE Antibiotic resistance is a major public health issue due to the growing lack of effective anti-infective therapeutics. New alternatives to treat and prevent biofilm-driven microbial infections, which exhibit high tolerance to clinically available antibiotics, are urgently needed. We report the identification of a small molecule that inhibits biofilm formation by two important pathogenic Gram-positive bacteria, Streptococcus mutans and Staphylococcus aureus. The small molecule selectively targets a transcriptional regulator leading to attenuation of a biofilm regulatory cascade and concurrent reduction of bacterial virulence in vivo. As the regulator is highly conserved, the finding has broad implication for the development of antivirulence therapeutics that selectively target biofilms.

Small-molecule compound SYG-180-2-2 attenuates Staphylococcus aureus virulence by inhibiting hemolysin and staphyloxanthin production

Multi-drug resistant Staphylococcus aureus infection is still a serious threat to global health. Therefore, there is an urgent need to develop new antibacterial agents based on virulence factor therapy to overcome drug resistance. Previously, we synthesized SYG-180-2-2 (C21H16N2OSe), an effective small molecule compound against biofilm. The aim of this study was to investigate the anti-virulence efficacy of SYG-180-2-2 against Staphylococcus aureus. MIC results demonstrated no apparent antibacterial activity of the SYG-180-2-2. The growth curve assay showed that SYG-180-2-2 had nonlethal effect on S. aureus. Besides, SYG-180-2-2 strongly inhibited the hemolytic activity and staphyloxanthin synthesis in S. aureus. Inhibition of staphyloxanthin by SYG-180-2-2 enhanced the sensitivity of S. aureus to oxidants and human whole blood. In addition, SYG-180-2-2 significantly decreased the expression of saeR-mediated hemolytic gene hlb and staphyloxanthin-related crtM, crtN and sigB genes by quantitative polymerase chain reaction (qPCR). Meanwhile, the expression of oxidative stress-related genes sodA, sodM and katA also decreased. Galleria Mellonella assay revealed that SYG-180-2-2 was not toxic to larvae. Further, the larvae infection model showed that the virulence of bacteria was significantly reduced after 4 μg/mL SYG-180-2-2 treatment. SYG-180-2-2 also reduced skin abscess formation in mice by reducing bacterial burden and subcutaneous inflammation. In conclusion, SYG-180-2-2 might be a promising agent to attenuate the virulence of S. aureus by targeting genes associated with hemolytic activity and staphyloxanthin synthesis.

Lipopeptide surfactin ameliorates the cell uptake of platensimycin and enhances its therapeutic effect on treatment of MRSA skin infection

OBJECTIVES

The rapid development of drug-resistant bacteria, especially MRSA, poses severe threats to global public health. Adoption of antibiotic adjuvants has proved to be one of the efficient ways to solve such a crisis. Platensimycin and surfactin were comprehensively studied to combat prevalent MRSA skin infection.

METHODS

MICs of platensimycin, surfactin or their combinations were determined by resazurin assay, while the corresponding MBCs were determined by chequerboard assay. Growth inhibition curves and biofilm inhibition were determined by OD measurements. Membrane permeability analysis was conducted by propidium iodide staining, and morphological characterizations were performed by scanning electron microscopy. Finally, the therapeutic effects on MRSA skin infections were evaluated in scald-model mice.

RESULTS

The in vitro assays indicated that surfactin could significantly improve the antibacterial performance of platensimycin against MRSA, especially the bactericidal activity. Subsequent mechanistic studies revealed that surfactin not only interfered with the biofilm formation of MRSA, but also disturbed their cell membranes to enhance membrane permeability, and therefore synergistically ameliorated MRSA cellular uptake of platensimycin. Further in vivo assessment validated the synergistic effect of surfactin on platensimycin and the resultant enhancement of therapeutical efficacy in MRSA skin-infected mice.

CONCLUSIONS

The combination of effective and biosafe surfactin and platensimycin could be a promising and efficient treatment for MRSA skin infection, which could provide a feasible solution to combat the major global health threats caused by MRSA.

A Phage Receptor-Binding Protein as a Promising Tool for the Detection of Escherichia coli in Human Specimens

Escherichia coli is a problematic pathogen that causes life-threatening diseases, being a frequent causative agent of several nosocomial infections such as urinary tract and bloodstream infections. Proper and rapid bacterial identification is critical for allowing prompt and targeted antimicrobial therapy. (Bacterio)phage receptor-binding proteins (RBPs) display high specificity for bacterial surface epitopes and, therefore, are particularly attractive as biorecognition elements, potentially conferring high sensitivity and specificity in bacterial detection. In this study, we elucidated, for the first time, the potential of a recombinant RBP (Gp17) to recognize E. coli at different viability states, such as viable but not culturable cells, which are not detected by conventional techniques. Moreover, by using a diagnostic method in which we combined magnetic and spectrofluorimetric approaches, we demonstrated the ability of Gp17 to specifically detect E. coli in various human specimens (e.g., whole blood, feces, urine, and saliva) in about 1.5 h, without requiring complex sample processing.

Distinctions between Fournier's gangrene and lower extremity necrotising fasciitis: microbiology and factors affecting mortality

OBJECTIVES

In this study, we aimed to illustrate distinctions between Fournier's gangrene (FG) and lower extremity necrotising fasciitis (NF) and screen out possible risk factors of poor prognosis for each cohort.

METHODS

The medical records of qualified patients with NF admitted to the Second People's Hospital of Yibin from January 2016 to June 2021 were retrospectively reviewed. All participants were anatomically categorised into FG and lower extremity NF groups, and their baseline data and microbiological results were compared. Further comparisons of critical parameters were conducted between survivors and nonsurvivors within each group.

RESULTS

A total of 49 patients were included in the study with a median age of 58 years, and overall mortality was 20.4%. There were 18 patients with FG and 31 patients with lower extremity NF. A microbiology distinction was found-the predominance of gram-negative infection in FG and gram-positive infection in lower extremity NF. High Fournier's gangrene severity index scores (greater than 7), advanced age, procalcitonin and D-dimer value were identified as risk factors for FG, and the presentation of sepsis was an alarming indicator for lower extremity NF.

CONCLUSIONS

The distinction of microbiology might provide advice for appropriate antibacterial administrations. In addition, with practical prognostic predicting tools, clinicians might be able to identify patients at increased risk and intervene promptly to avoid unfavourable outcomes.

Sonographically Occult Abscesses of the Buttock and Perineum in Children

BACKGROUND

Ultrasound (US) is used to differentiate abscess from cellulitis. At our institution, we observed children who had purulent fluid obtained after a negative abscess US. We sought to determine the incidence of sonographically occult abscess (SOA) of the buttock and perineum, and identify associated clinical and demographic characteristics.

METHODS

Retrospective chart review including children younger than 18 years old presenting to pediatric emergency department with soft tissue infection of the buttock or perineum and diagnostic radiology US read as negative for abscess. We defined SOA as wound culture growing pathogenic organism obtained within 48 hours of the US. Clinical and demographic characteristics included age, sex, race, ethnicity, fever, history of spontaneous drainage, duration of symptoms, previous methicillin resistant Staphylococcus aureus (MRSA) infection, or previous abscess. We used univariate and multivariate logistic regression to assess correlation between these characteristics and SOA.

RESULTS

A total of 217 children were included. Sixty-one (28%) children had SOA; 33 of 61 (54%) had incision and drainage within 4 hours of the US. Of children with SOA, 49 (80%) grew MRSA and 12 (20%) grew methicillin-sensitive S. aureus. In univariate analysis, a history of MRSA, symptom duration 4 days or less, age of younger than 4 years, and Hispanic ethnicity increased the odds of having SOA. In multivariate analysis, history of MRSA and duration of 4 days or less were associated with SOA.

CONCLUSIONS

Twenty-eight percent of children in our institution with US of the buttock and perineum negative for abscess had clinical abscess within 48 hours, most within 4 hours. History of MRSA and shorter symptom duration increased the odds of SOA.

Multi-Omics Analysis Reveals Anti-Staphylococcus aureus Activity of Actinomycin D Originating from Streptomyces parvulus

Staphylococcus aureus (S. aureus) is a common pathogen that causes various serious diseases, including chronic infections. Discovering new antibacterial agents is an important aspect of the pharmaceutical field because of the lack of effective antibacterial drugs. In our research, we found that one anti-S. aureus substance is actinomycin D, originating from Streptomyces parvulus (S. parvulus); then, we further focused on the anti-S. aureus ability and the omics profile of S. aureus in response to actinomycin D. The results revealed that actinomycin D had a significant inhibitory activity on S. aureus with a minimum inhibitory concentration (MIC) of 2 μg/mL and a minimum bactericidal concentration (MBC) of 64 μg/mL. Bacterial reactive oxygen species (ROS) increased 3.5-fold upon treatment with actinomycin D, as was measured with the oxidation-sensitive fluorescent probe DCFH-DA, and H₂O₂ increased 3.5 times with treatment by actinomycin D. Proteomics and metabolomics, respectively, identified differentially expressed proteins in control and treatment groups, and the co-mapped correlation network of proteomics and metabolomics annotated five major pathways that were potentially related to disrupting the energy metabolism and oxidative stress of S. aureus. All findings contributed to providing new insight into the mechanisms of the anti-S. aureus effects of actinomycin D originating from S. parvulus.

Staphylococcus aureus uses the ArlRS and MgrA cascade to regulate immune evasion during skin infection

Skin is one of the most common sites of host immune response against Staphylococcus aureus infection. Here, through a combination of in vitro assays, mouse models, and intravital imaging, we find that S. aureus immune evasion in skin is controlled by a cascade composed of the ArlRS two-component regulatory system and its downstream effector, MgrA. S. aureus lacking either ArlRS or MgrA is less virulent and unable to form correct abscess structure due to de-repression of a giant surface protein, Ebh. These S. aureus mutants also have decreased expression of immune evasion factors (leukocidins, chemotaxis-inhibitory protein of S. aureus [CHIPS], staphylococcal complement inhibitor [SCIN], and nuclease) and are unable to kill neutrophils, block their chemotaxis, degrade neutrophil extracellular traps, and survive direct neutrophil attack. The combination of disrupted abscess structure and reduced immune evasion factors makes S. aureus susceptible to host defenses. ArlRS and MgrA are therefore the main regulators of S. aureus immune evasion and promising treatment targets.

A Strong Synergy Between the Thiopeptide Bacteriocin Micrococcin P1 and Rifampicin Against MRSA in a Murine Skin Infection Model

Antibiotic-resistant bacterial pathogens have become a serious threat worldwide. One of these pathogens is methicillin-resistant Staphylococcus aureus (MRSA), a major cause of skin and soft tissue infections. In this study we identified a strain of Staphylococcus equorum producing a substance with high antimicrobial activity against many Gram-positive bacteria, including MRSA. By mass spectrometry and whole genome sequencing the antimicrobial substance was identified as the thiopeptide bacteriocin micrococcin P1 (MP1). Based on its properties we developed a one-step purification protocol resulting in high yield (15 mg/L) and high purity (98%) of MP1. For shorter incubation times (5-7 h) MP1 was very potent against MRSA but the inhibitory effect was overshadowed by resistance development during longer incubation time (24h or more). To overcome this problem a synergy study was performed with a number of commercially available antibiotics. Among the antibiotics tested, the combination of MP1 and rifampicin gave the best synergistic effect, with MIC values 25 and 60 times lower than for the individual drugs, respectively. To assess the therapeutic potential of the MP1-rifampicin combination, we used a murine skin infection model based on the use of the multidrug-resistant luciferase-tagged MRSA strain Xen31. As expected, neither of the single antimicrobials (MP1 or rifampicin) could eradicate Xen31 from the wounds. By contrary, the MP1-rifampicin combination was efficient not only to eradicate but also to prevent the recurrence of Xen31 infection. Furthermore, compared to fucidin cream, which is commonly used in skin infection treatments, MP1-rifampicin combination was superior in terms of preventing resistance development. Our results show that combining MP1, and probably other thiopeptides, with antibiotics can be a promising strategy to treat SSTIs caused by MRSA and likely many other Gram-positive bacteria.

Resistance Profiles and Biological Characteristics of Rifampicin-Resistant Staphylococcus aureus Small-Colony Variants

Background

Staphylococcus aureus (S. aureus) is a major contributor to nosocomial and community-acquired infections. S. aureus small colony variants (SCVs) which changed in relevant phenotype have made more limited and difficult for therapeutic options against S. aureus infections increasingly. Rifampicin is considered as the "last-resort" antibiotic against S. aureus. Our study investigated resistance profiles and biological characteristics of rifampicin-resistant S. aureus SCVs.

Methods

We collected S. aureus SCVs that were selected from 41 rifampicin-resistant clinical isolates. Then, biological characteristics, resistance spectrum, and rifampicin resistance mechanisms of tested S. aureus SCVs and corresponding parental strains were investigated by classic microbiological methods, agar dilution method, polymerase chain reaction (PCR). Moreover, the fitness cost of S. aureus SCVs, including growth, biofilm formation ability, and virulence profile, was also determined by bacterial growth curve assay, biofilm formation assay, and Galleria mellonella infection model.

Results

There were three S. aureus SCVs (JP310 SCVs, JP1450 SCVs, JP1486 SCVs) that were selected from 41 rifampicin-resistant S. aureus. S. aureus SCVs colonies were tiny, with decreased pigmentation, and the hemolysis circle was not obvious compared with corresponding parental strains. And SCVs could not be restored to normal-colony phenotype after hemin, menaquinone, or thymidine supplementation. Different rpoB mutations occurred in JP1486 SCVs. Antimicrobial susceptibility testing revealed MICs of SCVs were higher than corresponding parental strains. Besides, the growth ability and virulence of SCVs were lower, and biofilm formation ability of which increased compared with parental strains.

Conclusion

S. aureus SCVs share the rifampicin resistance mechanisms with parental strains, although there were some differences in the position of rpoB mutations. Moreover, we found that the biological characteristics of SCVs were significantly different from corresponding parental strains. In contrast, decreased susceptibility to other antibiotics of SCVs was observed during phenotype switch. Furthermore, SCVs incur the fitness cost.

Accurate and sensitive analysis of Staphylococcus aureus through CRISPR-Cas12a based recycling signal amplification cascades for early diagnosis of skin and soft tissue infections

Early-diagnosis and treatments of skin and soft tissue infections remain a huge challenge due to the difficulties in the detection of trace amounts of bacteria. We develop here a novel method through CRISPR-Cas12a based recycling signal amplification cascades and demonstrated its feasibility of Staphylococcus aureus detection in a sensitive and accurate way. The highlights of the proposed method are calculated as: i) the designed allosteric probe is responsible for accurate identification of SA through PBP2a-specific aptamer; ii) high sensitivity from three processes, including DNA polymerase-based target SA release, Nb.BbvCI enzyme induced ssDNA generation and attached CRISPR-Cas12a. As a result, the proposed method exhibited a detection range from 10⁶ to 10² CFU/ml. Eventually, we believe that the proposed method could be expanded for the construction of diverse sensing platforms for detecting different trace bacteria.

Community-associated MRSA among Indigenous children in remote settings: Best practices for NPs

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a major public health concern for Indigenous pediatric populations worldwide. It is the leading cause of skin and soft tissue infections in this demographic. This article reviews the literature and presents an evidence-based algorithm for the assessment and management of CA-MRSA among Indigenous children in remote settings.

Prevalence and molecular characterization of methicillin-resistant Staphylococcus aureus with mupirocin, fusidic acid and/or retapamulin resistance

Background

The data on the prevalence of resistance to mupirocin (MUP), fusidic acid (FA) and retapamulin (RET) in methicillin-resistant Staphylococcus aureus (MRSA) from China are still limited. This study aimed to examine these three antibiotics resistance in 1206 MRSA clinical isolates from Eastern China. Phenotypic MUP, FA and RET resistance was determined by minimum inhibitory concentrations (MICs), and genotypic by PCR and DNA sequencing of the mupA/B, fusB-D, cfr, vgaA/Av/A_LC/B/C/E, lsaA-C/E and salA and mutations in ileS, fusA/E, rplC, and 23S RNA V domain. The genetic characteristics of resistance isolates were conducted by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).

Results

Overall MRSA MUP, FA and RET resistance was low (5.1, 1.0 and 0.3%, respectively). MupA was the mechanism of high-level MUP resistance. All low-level MUP resistance isolates possessed an equivocal mutation N213D in IleS; of these, 2 reported an additional V588F mutation with an impact on the Rossman fold. FusA mutations, such as L461K, H457Q, H457Y and V90I were the primary FA mechanisms among high-level resistance isolates, most of which also contained fusC; however, all low-level resistance strains carried fusB. Except lsaE gene detected in one isolate, no other resistance mechanisms tested were found among RET-resistant isolates. Additionally, sixteen PFGE types (A-P) were observed, among which type B was the most common (49/76, 64.5%), followed by types E and G (4/76, 5.3% each) and types C and M (3/76, 3.9% each). All resistant strains were divided into 15 ST types by MLST. ST764 (24/76, 31.6%), ST630 (11/76, 14.5%), ST239 (9/76, 11.8%) and ST5 (7/76, 9.2%) were the major types. PFGE type B isolates with the aforementioned STs were mainly found in mupirocin resistant isolates.

Conclusions

MUP, FA and RET exhibited highly activity against the MRSA isolates. Acquired genes and chromosome-borne genes mutations were responsible for MUP and FA resistance; however, the mechanism for some RET-resistant isolates remains to be further elucidated. Also, the surveillance to MUP in MRSA should be strengthened to prevent elevated resistance due to the expansion of clones.

Dalbavancin for the Treatment of Complicated Gram-Positive Skin and Soft Tissue Infections

New antimicrobial agents have been developed to treat infections caused by methicillin-resistant Staphylococcus aureus and other multidrug-resistant pathogens. Dalbavancin is a novel semisynthetic lipoglycopeptide antibiotic, particularly active against methicillin-resistant Staphylococcus aureus. Due to its unique pharmacological characteristics and longer half-life, it can be administered once-weekly or every 15 days and in outpatient setting. Currently, it is indicated for complicated skin and soft tissue infections, but accumulating evidence points to its off-label efficacy in osteomyelitis and endocarditis. Further experience is still needed to increase our knowledge on the role of dalbavancin in a wider range of Gram-positive infections requiring prolonged antimicrobial treatment.

Early switch/early discharge opportunities for hospitalized patients with methicillin resistant Staphylococcus aureus complicated skin and soft tissue infections: Saudi Arabia and United Arab Emirates

OBJECTIVES

To describe opportunities for early switch (ES) from intravenous (IV) to oral (PO) antibiotics and early discharge (ED) of patients hospitalized in the Kingdom of Saudi Arabia (KSA) and the United Arab Emirates (UAE) with methicillin-resistant Staphylococcus aureus (MRSA) complicated skin and soft tissue infections (cSSTIs).

METHODS

This retrospective medical chart review study enrolled physicians from 16 KSA and UAE sites to collect data for 107 MRSA cSSTI patients.

RESULTS

Actual length of MRSA-active treatment was 13.3±9.3 mean days in KSA and 11.2±3.9 mean days in UAE, with a mean of 11.8±9.3 days of MRSA-targeted IV therapy in KSA and 10.7±4.3 days in UAE. 12.5% in KSA met ES criteria and potentially could have discontinued IV therapy 4.0±2.9 days sooner; 44.0% in UAE could have discontinued 6.6±3.6 days sooner. Patients were hospitalized for a mean 28.6±45.0 days in KSA and 13.1±5.9 days in UAE. 25.0% in KSA and 48.0% in UAE met ED criteria and potentially could have been discharged 6.1±8.0 days earlier in KSA and 7.9±5.0 days earlier in UAE.

CONCLUSIONS

A significant proportion of patients hospitalized for MRSA cSSTI could be eligible for ES or ED opportunities, resulting in potential for reductions in IV and bed days.

Evaluation of the Effect of Contezolid (MRX-I) on the Corrected QT Interval in a Randomized, Double-Blind, Placebo- and Positive-Controlled Crossover Study in Healthy Chinese Volunteers

Contezolid (MRX-I), a new oxazolidinone, is an antibiotic in development for treating complicated skin and soft tissue infections caused by resistant Gram-positive bacteria. This was a thorough QT study conducted in 52 healthy subjects who were administered oral contezolid at a therapeutic (800 mg) dose, a supratherapeutic (1,600 mg) dose, placebo, and oral moxifloxacin at 400 mg in four separate treatment periods. The pharmacokinetic profile of contezolid was also evaluated. Time point analysis indicated that the upper bounds of the two-sided 90% confidence interval (CI) for placebo-corrected change-from-baseline QTc (ΔΔQTc) were <10 ms for the contezolid therapeutic dose at each time point. The upper bound of the 90% CI for ΔΔQTc was slightly more than 10 ms with the contezolid supratherapeutic dose at 3 and 4 h postdose, and the prolongation effect on the QT/QTc interval was less than that of the positive control, moxifloxacin, at 400 mg. At 3 and 4 h after the moxifloxacin dose, the moxifloxacin group met the assay sensitivity criteria outlined in ICH Guidance E14 by having a lower confidence bound of ≥5 ms. The results of a linear exposure-response model which were similar to that of a time point analysis demonstrated a slightly positive relationship between contezolid plasma levels and ΔQTcF interval with a slope of 0.227 ms per mg/liter (90% CI, 0.188 to 0.266). In summary, contezolid did not prolong the QT interval at a therapeutic dose and may have a slight effect on QT interval prolongation at a supratherapeutic dose.

Current role of oxazolidinones and lipoglycopeptides in skin and soft tissue infections

PURPOSE OF REVIEW

An increase of skin and soft tissue infections involving Staphylococcus aureus has been reported in community and hospital settings. Methicillin resistance in S. aureus is associated with treatment failure and increased mortality. Recently, new antimicrobials with enhanced activity against methicillin-resistant Staph. aureus have been approved for the treatment of skin and soft tissue infections. Among these, novel oxazolidinones and lipoglycopeptides represent options with favorable pharmacokinetic characteristics and safety profiles.

RECENT FINDINGS

Newly approved compounds include tedizolid, characterized by the availability of both oral and intravenous formulation and once daily administration and dalbavancin, a long-acting antimicrobial allowing for weekly administration. These new molecules present advantages, such as enhanced activity against multidrug-resistant Gram-positive bacteria and favorable safety profiles.

SUMMARY

We have reviewed the pharmacokinetic characteristics and the implications for use in skin and soft tissue infections of tedizolid and dalbavancin. Advantages associated with the use of these compounds include the possibility for early patient discharge, reduced hospital length of stay, and outpatient treatment, with potential impact on morbidity, mortality, and overall health-care costs.

Staphylococcus aureus Internalized by Skin Keratinocytes Evade Antibiotic Killing

Staphylococcus aureus causes the majority of skin and soft tissue infections. Half of patients treated for primary skin infections suffer recurrences within 6 months despite appropriate antibiotic sensitivities and infection control measures. We investigated whether S. aureus internalized by human skin keratinocytes are effectively eradicated by standard anti-staphylococcal antibiotics. S. aureus, but not S. epidermidis, were internalized and survive within keratinocytes without inducing cytotoxicity or releasing the IL-33 danger signal. Except for rifampicin, anti-staphylococcal antibiotics in regular clinical use, including flucloxacillin, teicoplanin, clindamycin, and linezolid, did not kill internalized S. aureus, even at 20-fold their standard minimal inhibitory concentration. We conclude that internalization of S. aureus by human skin keratinocytes allows the bacteria to evade killing by most anti-staphylococcal antibiotics. Antimicrobial strategies, including antibiotic combinations better able to penetrate into mammalian cells are required if intracellular S. aureus are to be effectively eradicated and recurrent infections prevented.

Tedizolid Versus Linezolid for the Treatment of Acute Bacterial Skin and Skin Structure Infection: A Systematic Review and Meta-Analysis

This meta-analysis aims to assess the efficacy and safety of tedizolid, compared to linezolid, in the treatment of acute bacterial skin and skin structure infection (ABSSSI). PubMed, Web of Science, EBSCO (Elton B. Stephens Co.), Cochrane Library, Ovid Medline and Embase databases were accessed until 18 July 2019. Only randomized controlled trials (RCTs) comparing the efficacy of tedizolid with linezolid for adult patients with ABSSSIs were included. The outcomes included the clinical response, microbiological response, and risk of adverse events (AEs). A total of four RCTs involving 2056 adult patients with ABSSSI were enrolled. The early clinical response rate was 79.6% and 80.5% for patients receiving tedizolid and linezolid, respectively. The pooled analysis showed that tedizolid had a non-inferior early clinical response rate to linezolid (odds ratio (OR) = 0.96, 95% confidence interval (CI) = 0.77-1.19, I² = 0%). The early response rate was similar between tedizolid and linezolid among patients with cellulitis/erysipelas (75.1% vs. 77.1%; OR = 0.90, 95% CI = 0.64-1.27, I² = 25%), major cutaneous abscess (85.1% vs. 86.8%; OR = 0.93, 95% CI = 0.42-2.03, I² = 37%) and wound infection (85.9% vs. 82.6%; OR = 1.29, 95% CI = 0.66-2.51, I² = 45%). For methicillin-resistant Staphylococcus aureus patients, tedizolid had a favorable microbiological response rate of 95.2% which was comparable to linezolid (94%) (OR = 1.19, 95% CI = 0.49-2.90, I² = 0%). In addition to the similar risk of treatment-emergent AEs (a serious event, the discontinuation of the study drug due to AEs and mortality between tedizolid and linezolid), tedizolid was associated with a lower risk of nausea, vomiting and abnormal neutrophil count than linezolid. In conclusion, once-daily tedizolid (200 mg for six days) compared to linezolid (600 mg twice-daily for 10 days) was non-inferior in efficacy in the treatment of ABSSSI. Besides, tedizolid was generally as well tolerated as linezolid, and had a lower incidence of gastrointestinal AEs and bone marrow suppression than linezolid.

The role of dalbavancin in skin and soft tissue infections

PURPOSE OF REVIEW

The increase of skin and soft tissue infections (SSTIs) represents a major concern both in community and in the hospital setting. Staphylococcus aureus is the most frequently isolated pathogen, and the rise in infections due to methicillin-resistant Staphylococcus aureus (MRSA) has been associated with inadequate antibiotic treatment and increased morbidity.

RECENT FINDINGS

A number of new antimicrobials with activity against drug-resistant Gram-positive pathogens, including MRSA, have been recently approved for the treatment of SSTIs. New lipoglycopeptides, in particular dalbavancin, are long-acting antibiotics with potential for infrequent administration, offering the possibility for outpatient treatment and early hospital discharge.

SUMMARY

Dalbavancin is a new lipoglycopeptide showing high activity against Gram-positive bacteria, including drug-resistant strains. Dalbavancin presents a distinctive pharmacokinetic profile with a terminal prolonged half-life of approximately 14 days. This characteristic allows once-weekly dosing interval, avoiding the need for daily dosing and offering an advantage over other compounds for potential use in the outpatient setting or to promote early hospital discharge. Dalbavancin has a favorable adverse effect profile and appears to be a promising new alternative for treatment of SSTIs. We have reviewed the pharmacokinetic properties of dalbavancin and the clinical evidence for its use in complicated SSTIs and other potential applications.

Efficacy and Safety of Tedizolid Phosphate versus Linezolid in a Randomized Phase 3 Trial in Patients with Acute Bacterial Skin and Skin Structure Infection

Tedizolid phosphate is approved for the treatment of acute bacterial skin and skin structure infection (ABSSSI) caused by Gram-positive bacteria in the United States, Europe, and other countries. In this multicenter, double-blind, phase 3 study, 598 adult ABSSSI patients in China, Taiwan, the Philippines, and the United States were randomized to receive 200 mg of tedizolid, intravenously (i.v.)/orally (p.o.), once daily for 6 days or 600 mg of linezolid, i.v./p.o.

Tedizolid phosphate is approved for the treatment of acute bacterial skin and skin structure infection (ABSSSI) caused by Gram-positive bacteria in the United States, Europe, and other countries. In this multicenter, double-blind, phase 3 study, 598 adult ABSSSI patients in China, Taiwan, the Philippines, and the United States were randomized to receive 200 mg of tedizolid, intravenously (i.v.)/orally (p.o.), once daily for 6 days or 600 mg of linezolid, i.v./p.o. twice daily for 10 days. The primary endpoint was early clinical response rate at 48 to 72 h. Secondary endpoints included programmatic and investigator-assessed outcomes at end-of-therapy (EOT) and posttherapy evaluation (PTE) visits. Safety was also evaluated. In the intent-to-treat (ITT) population, 75.3% of tedizolid-treated patients and 79.9% of linezolid-treated patients were early responders (treatment difference, –4.6%; 95% confidence interval [CI], –11.2, 2.2). After exclusion of patients who never received the study drug (tedizolid, n = 8; linezolid, n = 1; modified ITT), comparable early response rates were observed (tedizolid, 77.4%; linezolid, 80.1%; treatment difference, –2.7%; 95% CI, –9.4, 3.9). Secondary endpoints showed high and similar clinical success rates in the ITT and clinically evaluable (CE) populations at EOT and PTE visits (e.g., CE-PTE for tedizolid, 90.4%; for linezolid, 93.5%). Both drugs were well tolerated, and no death occurred. Eight patients experienced phlebitis with tedizolid while none did with linezolid; hence, drug-related treatment-emergent adverse events were reported in a slightly higher proportion in the tedizolid (20.9%) arm than in the linezolid arm (15.8%). The study demonstrated that tedizolid in a primarily Asian population was an efficacious and well-tolerated treatment option for ABSSSI patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT02066402.)

Etiology, characteristics, and outcomes of community-onset necrotizing fasciitis in Korea: A multicenter study

Background

Necrotizing fasciitis (NF) is a serious skin and soft tissue infection causing high mortality. Investigating region specific epidemiologic factors associated with NF is important for establishing appropriate treatment strategies. This multicenter study was done to provide an update of the microbial etiology, clinical characteristics, and outcomes of NF in Korea.

Materials and methods

A retrospective cohort of adult patients with NF was established using patient data from 13 general hospitals between January 2012 and December 2015 in Korea. We evaluated microbial etiology and clinical characteristics to identify risk factors associated with in-hospital mortality; analyses were performed using binary logistic regression models.

Results

A total of 161 patients with NF were included. The most common underlying disease was diabetes mellitus (66 cases, 41.0%). A total of 148 organisms were isolated from 119 (73.9%) patients. Enteric Gram-negative organisms (36 patients) were the most common pathogen, followed by Staphylococcus aureus (30 patients) and streptococci (28 patients). Methicillin-resistant Staphylococcus aureus (MRSA) was identified in 6.2% (10/161) of patients. Of 37 enteric Gram-negative isolates tested, 26 (70.3%) isolates were susceptible to ceftriaxone. The in-hospital mortality rate was 22.4%. Intensive care unit admission, septic shock, and Gram-negative organism infections were significantly associated with in-hospital mortality, and surgery was not a favorable prognostic factor.

Conclusions

As initial empirical antibiotics, glycopeptides against MRSA and broad-spectrum antibiotics against third-generation cephalosporin-resistant organisms should be considered for patients with community-onset NF in Korea.

A case of methicillin-resistant Staphylococcus aureus wound infection: phylogenetic analysis to establish if nosocomial or community acquired

Methicillin‐resistant Staphylococcus aureus (MRSA) infection is rapidly increasing in both hospital and community settings. A 71‐year‐old man admitted at the Department of Orthopaedics and Trauma Surgery, University Campus Bio‐Medico of Rome, with MRSA wound infection consequent to orthopedic surgery was studied and the MRSA transmission evaluated by phylogenetic analysis.

Antimicrobial Effects of Sulfonyl Derivative of 2(5H)-Furanone against Planktonic and Biofilm Associated Methicillin-Resistant and -Susceptible Staphylococcus aureus

The gram-positive opportunistic bacterium Staphylococcus aureus is one of the most common causatives of a variety of diseases including skin and skin structure infection or nosocomial catheter-associated infections. The biofilm formation that is an important virulence factor of this microorganism renders the antibiotic therapy ineffective, because biofilm-embedded bacteria exhibit strongly increased tolerance to antimicrobials. Here, we describe a novel 3-chloro-5(S)-[(1R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy]-4-[4-methylphenylsulfonyl]-2(5H)-furanone (F105), possessing a sulfonyl group and l-menthol moiety. Minimal inhibitory and bactericidal concentration values (MIC and MBC) of F105 were 10 and 40 mg/L, respectively, suggesting F105 biocidal properties. F105 exhibits pronounced activity against biofilm-embedded S. aureus and increases the efficacy of aminoglycosides (amikacin, gentamicin, and kanamycin) and benzalkonium chloride with fractional inhibitory concentration index values of 0.33–0.44 and 0.29, respectively, suggesting an alternative external treatment option, e.g., for wound infections. Moreover, low concentrations (0.5–1.3 mg/L) of F105 reduced the MICs of these antimicrobials twofold. By using confocal laser scanning microscopy and CFU counting, we show explicitly that F105 also restores the antimicrobial activity of gentamicin and ampicillin against S. aureus biofilms by several orders of magnitude. Biofilm structures were not destroyed but sterilized, with embedded cells being almost completely killed at twofold MBC. While F105 is quite toxic (CC₅₀/MBC ratio 0.2), our data suggest that the F105 chemotype might be a promising starting point for the development of complex topical agents for combined anti-staphylococcal biofilm-therapies restoring the efficacy of some antibiotics against difficult to treat S. aureus biofilm.

Clinical and pharmacokinetic drug evaluation of delafloxacin for the treatment of acute bacterial skin and skin structure infections

INTRODUCTION

In the era of multi-drug resistant pathogens, the adequate treatment of skin and skin structure infections remains a challenge for clinicians. Delafloxacin, with its broad spectrum against Gram-positive, Gram-negative and anaerobic organisms, represents a new therapeutic option in this setting, especially when coverage of methicillin-resistant Staphylococcus aureus is required in the empirical or targeted approach. Areas covered: In this drug evaluation, the Authors have reviewed the pharmacokinetic and pharmacodynamic characteristics of delafloxacin. In addition, recent data on clinical efficacy and safety from clinical trials have been included. Expert opinion: Delafloxacin represents an attractive therapeutic option due to a broad antimicrobial and favorable pharmacokinetic and pharmacodynamic profile. Several in vitro studies have demonstrated the low potential for resistance selection if used in empirical regimens. Delafloxacin is a promising candidate for the treatment of Gram-positive infections, especially if co-infection with other pathogens is suspected. This is because of the very low MIC of the agent for Gram-positive (including MRSA) and anaerobic bacteria and because of the wide spectrum of activity against Gram-negative organisms. For these interesting microbiological and PK/PD characteristics we expect future uses of this drug in other indications such as diabetic foot infection, osteomyelitis, prosthetic joint infections, abdominal infections and central nervous system infections.

Broad-range lytic bacteriophages that kill Staphylococcus aureus local field strains

Staphylococcus aureus is a very successful opportunistic pathogen capable of causing a variety of diseases ranging from mild skin infections to life-threatening sepsis, meningitis and pneumonia. Its ability to display numerous virulence mechanisms matches its skill to display resistance to several antibiotics, including β-lactams, underscoring the fact that new anti-S. aureus drugs are urgently required. In this scenario, the utilization of lytic bacteriophages that kill bacteria in a genus -or even species- specific way, has become an attractive field of study. In this report, we describe the isolation, characterization and sequencing of phages capable of killing S. aureus including methicillin resistant (MRSA) and multi-drug resistant S. aureus local strains from environmental, animal and human origin. Genome sequencing and bio-informatics analysis showed the absence of genes encoding virulence factors, toxins or antibiotic resistance determinants. Of note, there was a high similarity between our set of phages to others described in the literature such as phage K. Considering that reported phages were obtained in different continents, it seems plausible that there is a commonality of genetic features that are needed for optimum, broad host range anti-staphylococcal activity of these related phages. Importantly, the high activity and broad host range of one of our phages underscores its promising value to control the presence of S. aureus in fomites, industry and hospital environments and eventually on animal and human skin. The development of a cocktail of the reported lytic phages active against S. aureus–currently under way- is thus, a sensible strategy against this pathogen.

Lipophosphonoxins II: Design, Synthesis, and Properties of Novel Broad Spectrum Antibacterial Agents

The increase in the number of bacterial strains resistant to known antibiotics is alarming. In this study we report the synthesis of novel compounds termed Lipophosphonoxins II (LPPO II). We show that LPPO II display excellent activities against Gram-positive and -negative bacteria, including pathogens and multiresistant strains. We describe their mechanism of action-plasmatic membrane pore-forming activity selective for bacteria. Importantly, LPPO II neither damage nor cross the eukaryotic plasmatic membrane at their bactericidal concentrations. Further, we demonstrate LPPO II have low propensity for resistance development, likely due to their rapid membrane-targeting mode of action. Finally, we reveal that LPPO II are not toxic to either eukaryotic cells or model animals when administered orally or topically. Collectively, these results suggest that LPPO II are highly promising compounds for development into pharmaceuticals.