Methicillin-resistant S. aureus infections among patients in the emergency department

The Staphylococcus aureus regulatory program in a human skin-like environment

Staphylococcus aureus is a Gram-positive pathogen responsible for the majority of skin and soft tissue infections (SSTIs). S. aureus colonizes the anterior nares of approximately 20-30% of the population and transiently colonizes the skin, thereby increasing the risk of developing SSTIs and more serious infections. Current laboratory models that mimic the skin surface environment are expensive, require substantial infrastructure, and limit the scope of bacterial physiology studies under human skin conditions. To overcome these limitations, we developed a cost-effective, open-source, chemically defined media recipe termed skin-like media (SLM) that incorporates key aspects of the human skin surface environment and supports growth of several Staphylococcal species. We utilized SLM to investigate the transcriptional response of methicillin-resistant S. aureus (MRSA) following growth in SLM compared to a commonly used laboratory media. Through RNA-seq analysis, we observed the upregulation of several virulence factors, including genes encoding functions involved in adhesion, proteolysis, and cytotoxicity. To further explore these findings, we conducted qRT-PCR experiments to determine the influence of media composition, pH, and temperature on the transcriptional response of key factors involved in adhesion and virulence. We also demonstrated that MRSA primed in SLM adhered better to human corneocytes and demonstrated adhesin-specific phenotypes that previously required genetic manipulation. These results support the potential utility of SLM as an in vitro model for assessing Staphylococcal physiology and metabolism on human skin.

Importance

Staphylococcus aureus is the major cause of skin diseases, and its increased prevalence in skin colonization and infections present a need to understand its physiology in this environment. The work presented here outlines S. aureus upregulation of colonization and virulence factors using a newly developed media that strives to replicate the human skin surface environment, and demonstrates roles for adhesins ClfA, SraP, and Fnbps in human corneocyte adherence.

Polyiodo Azole-Based Metal-Organic Framework Energetic Biocidal Material for Synergetic Sterilization Applications

Biological hazards caused by bacteria, viruses, and toxins have become a major survival and development issue facing the international community. However, the traditional method of disinfection and sterilization is helpless in dealing with viruses that spread quickly and are highly infectious. Metal-organic framework (MOF) biocidal materials hold promise as superior alternatives to traditional sterilization materials because of their stable framework structures and unique properties. Now, we demonstrate for the first time the synthesis of a MOF (TIBT-Cu) containing Cu metal centers and tetraiodo-4,4'-bi-1,2,4-triazole as the main ligand. This novel MOF biocidal material has good thermal stability (Td = 278 °C), excellent mechanical sensitivity, and a high bacteriostatic efficiency (>99.90%). Additionally, the particles produced by the combustion of TIBT-Cu are composed of active iodine substances and CuO particles, which can act synergistically against harmful microorganisms such as bacteria and viruses. This study provides a new perspective for the preparation of highly effective bactericidal materials.

Efficacy and safety of vancomycin for the treatment of Staphylococcus aureus bacteraemia: a systematic review and meta-analysis

OBJECTIVES

To evaluate the safety and efficacy of vancomycin with the other anti-Gram-positive bacteria antibiotics in the treatment of Staphylococcus aureus bacteraemia.

METHODS

We searched the PubMed, MEDLINE, Embase and Cochrane Library databases until August 2022 for studies that compared vancomycin with other antibiotic regimens for treating Staphylococcus aureus bacteraemia. Clinical and microbiological responses, adverse events, relapse rate and mortality were considered.

RESULTS

Fifteen randomized controlled trials and nine retrospective studies were included. The efficacy and safety data of vancomycin differed from those of the comparators group. After subgroup analysis, the differences came mainly from the trials compared with daptomycin. Compared to daptomycin, vancomycin showed a lower microbiological cure rate (OR = 0.58, 95% CI = 0.41∼0.82, I2 = 0%, P = 0.002) and clinical cure rate (OR = 0.53, 95% CI = 0.42∼0.68, I2 = 3%, P < 0.00001), as well as more adverse events (OR = 3.21, 95% CI = 1.43∼7.19, I2 = 59%, P = 0.005).

CONCLUSION

The efficacy of vancomycin in treating Staphylococcus aureus bacteraemia is still excellent but slightly inferior in adverse events. However, this does not affect its use as a first-line drug. Daptomycin is expected to be a better antimicrobial drug.

A multilocus sequence typing method of Staphylococcus aureus DNAs in a sample from human skin

The skin and mucous membranes are the primary sites of Staphylococcus aureus colonization, particularly those of health care personnel and patients in long-term care centers. We found that S. aureus colonized with a higher abundance ratio on skins which had recovered from pressure injury (PI) than on normal skins in our earlier research on the skin microbiota of bedridden patients. Multilocus sequence typing (MLST) is a useful tool for typing S. aureus isolated from clinical specimens. However, the MLST approach cannot be used in microbiota DNA owing to the contamination from other bacteria species. In this study, we developed a multiplex-nested PCR method to determine S. aureus MLST in samples collected from human skins. The seven pairs of forward and reverse primers were designed in the upstream and downstream regions, which were conserved specifically in S. aureus. The first amplifications of the seven pairs were conducted in a multiplex assay. The samples were diluted and applied to conventional PCR for MLST. We confirmed that the method amplified the seven allele sequences of S. aureus specifically in the presence of untargeted DNAs from human and other skin commensal bacteria. Using this assay, we succeeded in typing sequence types (STs) of S. aureus in the DNA samples derived from the skins healed from PI. Peaks obtained by Sanger sequencing showed that each sample contained one ST, which were mainly categorized into clonal complex 1 (CC1) or CC5. We propose that this culture-free approach may be used in detecting S. aureus in clinical specimens without isolation.

Emergency department care of ABSSSI with dalbavancin infusion, direct discharge, and outpatient telemedicine follow up: a study protocol

Novel therapeutic strategies such as the long-acting lipoglycopeptide antibiotics allow for the treatment and discharge of selected emergency department (ED) patients with Acute Bacterial Skin and Skin Structure Infections (ABSSSI), who require intravenous antibiotics and would otherwise be hospitalized. The COVID-19 pandemic highlighted the need to develop strategies that may reduce hospitalization. The telehealth approach has shown success in remote management of cellulitis patients and could aid in the remote follow up of overall ABSSSI patients. This article describes a study protocol for the telemedicine follow up of patients diagnosed with ABSSSI in the ED, requiring intravenous treatment, receiving a single dalbavancin dose, and directly discharged. A telehealth system for remote follow up is evaluated as well as the possible inclusion of point-of-care ultrasound for the appropriate diagnosis of ABSSSI. The study will be conducted in compliance with regulatory requirements; and all collected data will be kept strictly confidential and in accordance with all relevant legislation on the control and protection of personal information. Dissemination of the study protocol may help increasing knowledge and awareness on this topic, with the aim of optimizing patient management, reducing hospitalization and lower the impact on healthcare associated costs.

Comparing the Phylogenetic Distribution of Multilocus Sequence Typing, Staphylococcal Protein A, and Staphylococcal Cassette Chromosome Mec Types in Methicillin-Resistant Staphylococcus Aureus (MRSA) in Korea from 1994 to 2020

Staphylococcus aureus (S. aureus) bacteremia is one of the most frequent and severe bacterial infections worldwide. Methicillin-resistant Staphylococcus aureus (MRSA) is a serious human pathogen that can cause a wide variety of infections. Comparative genetic analyses have shown that despite the existence of a vast number of genotypes, genotypes are restricted to certain geographical locations. By comparing multilocus sequence typing (MLST) and SCCmec types from 1994 to 2020, the present study intended to discover which genotype genes were related to MRSA infections. MLST, Staphylococcus aureus protein A (spa), and SCCmec typings were performed to determine their relationship during those years. Results revealed that MRSA isolates in the Republic of Korea were distributed among all major staphylococcal cassette chromosome mec (SCCmec) types. The majority of SCCmec isolates belonged to SCCmec type II and type IV. The majority of MLST had the sequence type (ST) 72, 239, 8, or 188. By contrast, minorities belonged to ST22 (SCCmec IV), ST772 (SCCmec V), and ST672 (SCCmec V) genotypes. The SCCmec type was determined for various types. The spa type was dispersed, seemingly regardless of its multidrug resistance property. The MLST type was found to be similar to the existing typical type. These results showed some correlations between resistance characteristics and types according to the characteristics of the MLST types distributed, compared to previous papers. Reports on genotype distribution of MLST and SCCmec types in MRSA are rare. These results show a clear distribution of MLST and SCCmec types of MRSA from 1994 to 2020 in the Republic of Korea.

Retrospective Study on Staphylococcus aureus Resistance Profile and Antibiotic Use in a Pediatric Population

The growing phenomenon of antibiotic resistance and the presence of limited data concerning the pediatric area prompted us to focus on Staphylococcus aureus infection in this study, its antibiotic resistance profile, and the therapeutic management of affected children. We conducted a retrospective study by collecting clinical data on infants and children with antibiogram-associated S. aureus infection. We enrolled 1210 patients with a mean age of 0.9 years. We analyzed the resistance patterns and found 61.5% resistance to oxacillin, 58.4% resistance to cephalosporins, 41.6% resistance to aminoglycosides, and 38.3% resistance to fluoroquinolones. Importantly, we found no resistance to glycopeptides, a key antibiotic for MRSA infections whose resistance is increasing worldwide. We also found that the main risk factors associated with antibiotic resistance are being aged between 0 and 28 days, the presence of devices, and comorbidities. Antibiotic resistance is a growing concern; knowing the resistance profiles makes it possible to better target the therapy; however, it is important to use antibiotics according to the principles of antibiotic stewardship to limit their spread.

Epidemiology of Methicillin-Resistant Staphylococcus aureus in Slovakia, 2020 - Emergence of an Epidemic USA300 Clone in Community and Hospitals

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of health care-associated infections. Additionally, over the decades, the spread of community-associated (CA-MRSA) clones has become a serious problem. The aim of this study was to gain data on the current epidemiology of MRSA in Slovakia. Between January 2020 and March 2020, single-patient MRSA isolates (invasive and/or colonizing) were collected in Slovakia from hospitalized inpatients (16 hospitals) or outpatients (77 cities). Isolates were characterized via antimicrobial susceptibility testing, spa typing, SCCmec typing, the detection of mecA/mecC, genes coding for Panton-Valentine leukocidin (PVL), and the arcA gene (part of the arginine catabolic mobile element [ACME]). Out of 412 isolates, 167 and 245 originated from hospitalized patients and outpatients, respectively. Inpatients were most likely older (P < 0.001) and carried a strain exhibiting multiple resistance (P = 0.015). Isolates were frequently resistant to erythromycin (n = 320), clindamycin (n = 268), and ciprofloxacin/norfloxacin (n = 261). 55 isolates were resistant to oxacillin/cefoxitin only. By clonal structure, CC5-MRSA-II (n = 106; spa types t003, t014), CC22-MRSA-IV (n = 75; t032), and CC8-MRSA-IV (n = 65; t008) were the most frequent. We identified PVL in 72 isolates (17.48%; 17/412), with the majority belonging to CC8-MRSA-IV (n = 55; arcA+; t008, t622; the USA300 CA-MRSA clone) and CC5-MRSA-IV (n = 13; t311, t323). To the best of our knowledge, this is the first study on the epidemiology of MRSA in Slovakia. The presence of the epidemic HA-MRSA clones CC5-MRSA-II and CC22-MRSA-IV was found, as was, importantly, the emergence of the global epidemic USA300 CA-MRSA clone. The extensive spread of USA300 among inpatients and outpatients across the Slovakian regions warrants further investigation. IMPORTANCE The epidemiology of MRSA is characterized by the rise and fall of epidemic clones. Understanding the spread, as well as the evolution of successful MRSA clones, depends on the knowledge of global MRSA epidemiology. However, basic knowledge about MRSA epidemiology is still fragmented or completely missing in some parts of the world. This is the first study of MRSA epidemiology in Slovakia to identify the presence of the epidemic HA-MRSA clones CC5-MRSA-II and CC22-MRSA-IV and, importantly and unexpectedly, the emergence of the global epidemic USA300 CA-MRSA clone in the Slovakian community and hospitals. So far, USA300 has failed to spread in Europe, and this study documents an extensive spread of this epidemic clone in a European country for the first time.

Exploring novel aryl/heteroaryl-isosteres of phenylthiazole against multidrug-resistant bacteria

Antimicrobial resistance has become a concern as a worldwide threat. A novel scaffold of phenylthiazoles was recently evaluated against multidrug-resistant Staphylococci to control the emergence and spread of antimicrobial resistance, showing good results. Several structural modifications are needed based on the structure-activity relationships (SARs) of this new antibiotic class. Previous studies revealed the existence of two key structural features essential for the antibacterial activity, the guanidine head and lipophilic tail. In this study, a new series of twenty-three phenylthiazole derivatives were synthesized utilizing the Suzuki coupling reaction to explore the lipophilic part. The in vitro antibacterial activity was evaluated against a range of clinical isolates. The three most promising compounds, 7d, 15d and 17d, with potent MIC values against MRSA USA300 were selected for further antimicrobial evaluation. The tested compounds exhibited potent results against the tested MSSA, MRSA, and VRSA strains (concentration: 0.5 to 4 μg mL-1). Compound 15d inhibited MRSA USA400 at a concentration of 0.5 μg mL-1 (one-fold more potent than vancomycin) and showed low MIC values against ten clinical isolates, including linezolid-resistant strain MRSA NRS119 and three vancomycin-resistant isolates VRSA 9/10/12. Moreover, compound 15d retained its potent antibacterial activity using the in vivo model by the burden reduction of MRSA USA300 in skin-infected mice. The tested compounds also showed good toxicity profiles and were found to be highly tolerable to Caco-2 cells at concentrations of up to 16 μg mL-1, with 100% of the cells remaining viable.

Prevalence and antibiotic resistance of Staphylococcus aureus associated with a college-aged cohort: life-style factors that contribute to nasal carriage

Staphylococcus aureus is an opportunistic human pathogen that can frequently be found at various body locations, such as the upper respiratory tract, nostrils, skin, and perineum. S. aureus is responsible for causing a variety of conditions, which range from minor skin infections and food poisoning to life-threatening sepsis and endocarditis. Furthermore, S. aureus has developed resistance to numerous antimicrobial agents, which has made treatment of S. aureus infections difficult. In the present study, we examined lifestyle factors that could increase the likelihood of S. aureus carriage, the overall prevalence of S. aureus, as well as assessed the antibiotic resistance profiles of the S. aureus isolates among a population of college students. Five hundred nasal samples were collected and analyzed via selective growth media, coagulase and protein A testing, as well as polymerase chain reaction and DNA sequencing. One hundred four out of the 500 samples collected (21%) were identified as containing S. aureus. The S. aureus isolates were resistant to penicillin (74%), azithromycin (34%), cefoxitin (5%), ciprofloxacin (5%), tetracycline (4%), and trimethoprim (1%), but sensitive to gentamicin and rifampin. Lastly, we identified several lifestyle factors (i.e., pet exposure, time spent at the university recreational facility, musical instrument usage, and tobacco usage) positively correlated with S. aureus nasal colonization.

Validation of a Clinical Decision Rule for Ultrasound Identification of MRSA Skin Abscesses in Children

OBJECTIVE

The aim of this study was to validate an adult-derived clinical decision rule for ultrasound identification of methicillin-resistant Staphylococcus aureus (MRSA) skin abscesses in a pediatric cohort.

METHODS

We conducted a retrospective study of skin and soft tissue infections in patients <21 years presenting to the emergency department who had radiology performed ultrasounds completed and wound cultures obtained. Ultrasound scans were reviewed for edge definition, volume, and shape by 2 pediatric emergency physicians with expertise in point-of-care ultrasound, with approximately 25% of scans reviewed by both experts to evaluate interrater reliability. A third, blinded expert weighed in for discrepancies before analysis. Test performance characteristics were calculated for the clinical decision rule in children.

RESULTS

Two hundred nine patients were enrolled, with mean age of 9.8 (±6.7) years; 87 (42%) were male. Sixty-nine (33%) patients had a wound culture positive for MRSA. The clinical decision rule had a sensitivity of 86% (95% confidence interval [CI], 75%-93%), specificity of 32% (95% CI, 25%-41%), positive predictive value of 38% (95% CI, 35%-42%), negative predictive value of 82% (95% CI, 71%-89%), positive likelihood ratio of 1.26 (95% CI, 1.08-1.46), negative likelihood ratio of 0.45 (95% CI, 0.24-0.84), and an odds ratio of 2.8 (95% CI, 1.31-5.97).

CONCLUSIONS

This clinical decision rule for ultrasound identification of MRSA abscesses had moderately high sensitivity and negative predictive value in pediatric patients, with similar sensitivity compared with the original adult validation group. Ultrasound may help identify MRSA abscesses, allowing for improved antibiotic choices and outcomes for children with MRSA abscesses.

Antibacterial and antifungal action of CTAB-containing silica nanoparticles against human pathogens

New antibiotic agents are urgently needed worldwide to combat the increasing tolerance and resistance of pathogenic fungi and bacteria to current antimicrobials. Here, we looked at the antibacterial and antifungal effects of minor quantities of cetyltrimethylammonium bromide (CTAB), ca. 93.8 mg g^-1, on silica nanoparticles (MPSi-CTAB). Our results show that MPSi-CTAB exhibits antimicrobial activity against Methicillin-resistant Staphylococcus aureus strain (S. aureus ATCC 700698) with MIC and MBC of 0.625 mg mL^-1 and 1.25 mg mL^-1, respectively. Additionally, for Staphylococcus epidermidis ATCC 35984, MPSi-CTAB reduces MIC and MBC by 99.99% of viable cells on the biofilm. Furthermore, when combined with ampicillin or tetracycline, MPSi-CTAB exhibits reduced MIC values by 32- and 16-folds, respectively. MPSi-CTAB also exhibited in vitro antifungal activity against reference strains of Candida, with MIC values ranging from 0.0625 to 0.5 mg mL^-1. This nanomaterial has low cytotoxicity in human fibroblasts, where over 80% of cells remained viable at 0.31 mg mL^-1 of MPSi-CTAB. Finally, we developed a gel formulation of MPSi-CTAB, which inhibited in vitro the growth of Staphylococcus and Candida strains. Overall, these results support the efficacy of MPSi-CTAB with potential application in the treatment and/or prevention of infections caused by methicillin-resistant Staphylococcus and/or Candida species.

In Vitro Activities of Ceftobiprole, Dalbavancin, Tedizolid and Comparators against Clinical Isolates of Methicillin-Resistant Staphylococcus aureus Associated with Skin and Soft Tissue Infections

Skin and soft tissue infections (SSTIs) are associated with significant morbidity and healthcare costs, especially when caused by methicillin-resistant Staphylococcus aureus (MRSA). Vancomycin is a preferred antimicrobial therapy for the management of complicated SSTIs (cSSTIs) caused by MRSA, with linezolid and daptomycin regarded as alternative therapeutic options. Due to the increased rates of antimicrobial resistance in MRSA, several new antibiotics with activity against MRSA have been recently introduced in clinical practice, including ceftobiprole, dalbavancin, and tedizolid. We evaluated the in vitro activities of the aforementioned antibiotics against 124 clinical isolates of MRSA obtained from consecutive patients with SSTIs during the study period (2020-2022). Minimum inhibitory concentrations (MICs) for vancomycin, daptomycin, ceftobiprole, dalbavancin, linezolid and tedizolid were evaluated by the MIC Test Strip using Liofilchem strips. We found that when compared to the in vitro activity of vancomycin (MIC₉₀ = 2 μg/mL), dalbavancin possessed the lowest MIC₉₀ (MIC₉₀ = 0.094 μg/mL), followed by tedizolid (MIC₉₀ = 0.38 μg/mL), linezolid, ceftobiprole, and daptomycin (MIC₉₀ = 1 μg/mL). Dalbavancin demonstrated significantly lower MIC₅₀ and MIC₉₀ values compared to vancomycin (0.064 vs. 1 and 0.094 vs. 2, respectively). Tedizolid exhibited an almost threefold greater level of in vitro activity than linezolid, and also had superior in vitro activity compared to ceftobiprole, daptomycin and vancomycin. Multidrug-resistant (MDR) phenotypes were detected among 71.8% of the isolates. In conclusion, ceftobiprole, dalbavancin and tedizolid exhibited potent activity against MRSA and are promising antimicrobials in the management of SSTIs caused by MRSA.

Toward Rapid and Accurate Molecular Diagnostics at Home

The global outbreaks of infectious diseases have significantly driven an imperative demand for rapid and accurate molecular diagnostics. Nucleic acid amplification tests (NAATs) feature high sensitivity and high specificity; however, the labor-intensive sample preparation and nucleic acid amplification steps remain challenging in order to carry out rapid and precision molecular diagnostics at home. This review discusses the advances and challenges of automatic solutions of sample preparation integrated with on-chip nucleic acid amplification for effective and accurate molecular diagnostics at home. The sample preparation methods of whole blood, urine, saliva/nasal swab, and stool on chip are examined. Then, the repurposable integrated sample preparation on a chip using various biological samples is investigated. Finally, the on-chip NAATs that can be integrated with automated sample preparation are evaluated. The user-friendly approaches with combined sample preparation and NAATs can be the game changers for next-generation rapid and precision home diagnostics.

Skin and soft tissue infections in the elderly

PURPOSE OF REVIEW

To highlight the peculiarity of skin and soft tissue infections (SSTIs) in elderly patients and to provide useful elements for their optimal management.

RECENT FINDINGS

In the COVID-19 era, early discharge from the hospital and implementation of outpatient management is of key importance.

SUMMARY

Elderly patients are at high risk of SSTIs due to several factors, including presence of multiple comorbidities and skin factors predisposing to infections. Clinical presentation may be atypical and some signs of severity, such as fever and increase in C-reactive protein, may be absent or aspecific in this patients population. An appropriate diagnosis of SSTIs in the elderly is crucial to avoid antibiotic overtreatment. Further studies should explore factors associated with bacterial superinfections in patients with pressure ulcers or lower limb erythema. Since several risk factors for methicillin-resistant Staphylococcus aureus (MRSA) may coexist in elderly patients, these subjects should be carefully screened for MRSA risk factors and those with high risk of resistant etiology should receive early antibiotic therapy active against MRSA. Physicians should aim to several objectives, including clinical cure, patient safety, early discharge and return to community. SSTIs in the elderly may be managed using long-acting antibiotics, but clinical follow-up is needed.

Clinical Impact of Staphylococcus aureus Skin and Soft Tissue Infections

The pathogenic bacterium Staphylococcus aureus is the most common pathogen isolated in skin-and-soft-tissue infections (SSTIs) in the United States. Most S. aureus SSTIs are caused by the epidemic clone USA300 in the USA. These infections can be serious; in 2019, SSTIs with S. aureus were associated with an all-cause, age-standardized mortality rate of 0.5 globally. Clinical presentations of S. aureus SSTIs vary from superficial infections with local symptoms to monomicrobial necrotizing fasciitis, which can cause systemic manifestations and may lead to serious complications or death. In order to cause skin infections, S. aureus employs a host of virulence factors including cytolytic proteins, superantigenic factors, cell wall-anchored proteins, and molecules used for immune evasion. The immune response to S. aureus SSTIs involves initial responders such as keratinocytes and neutrophils, which are supported by dendritic cells and T-lymphocytes later during infection. Treatment for S. aureus SSTIs is usually oral therapy, with parenteral therapy reserved for severe presentations; it ranges from cephalosporins and penicillin agents such as oxacillin, which is generally used for methicillin-sensitive S. aureus (MSSA), to vancomycin for methicillin-resistant S. aureus (MRSA). Treatment challenges include adverse effects, risk for Clostridioides difficile infection, and potential for antibiotic resistance.

Primary skin abscess microbiota a systematic review

An abscess is a collection of pus forming a cavity in the tissue, for example, the skin. They are generally perceived as the result of infection but infection is not mandatory for the diagnosis. Skin abscesses may occur independently (primary) or be part of other diseases such as the recurrent inflammatory skin disease hidradenitis suppurativa (HS). HS is noninfectious but nevertheless abscesses are a common differential diagnosis. The purpose of this study is to review the microbiome of bacteria positive primary skin abscesses in order to explore the reported microbiota. EMBASE, MEDLINER, and COCHRANE LIBRABRY were searched on 9th of October 2021 for microbiome, skin, and abscesses. Studies with more than 10 patients reporting the microbiome in human skin-abscesses were included and studies with abscess microbiota sampled from HS patients, microbiota not sampled from skin-abscesses, missing information on microbiome data, sampling bias, studies in other language than English or Danish, reviews and meta-analyses were excluded. In total 11 studies were included for further analysis. S. aureus is likely to dominate the microbiome of bacteria positive primary skin abscesses in contrast to the polymicrobial microbiome of HS.

Bioengineered materials with selective antimicrobial toxicity in biomedicine

Fungi and bacteria afflict humans with innumerous pathogen-related infections and ailments. Most of the commonly employed microbicidal agents target commensal and pathogenic microorganisms without discrimination. To distinguish and fight the pathogenic species out of the microflora, novel antimicrobials have been developed that selectively target specific bacteria and fungi. The cell wall features and antimicrobial mechanisms that these microorganisms involved in are highlighted in the present review. This is followed by reviewing the design of antimicrobials that selectively combat a specific community of microbes including Gram-positive and Gram-negative bacterial strains as well as fungi. Finally, recent advances in the antimicrobial immunomodulation strategy that enables treating microorganism infections with high specificity are reviewed. These basic tenets will enable the avid reader to design novel approaches and compounds for antibacterial and antifungal applications.

Oral Vaccination with Engineered Probiotic Limosilactobacillus reuteri Has Protective Effects against Localized and Systemic Staphylococcus aureus Infection

Staphylococcus aureus is a Gram-positive bacterium responsible for most hospital-acquired (nosocomial) and community-acquired infections worldwide. The only therapeutic strategy against S. aureus-induced infections, to date, is antibiotic treatment. A protective vaccine is urgently needed in view of the emergence of antibiotic-resistant strains associated with high-mortality cases; however, no such vaccine is currently available. In our previous work, the feasibility of implementing a Lactobacillus delivery system for development of S. aureus oral vaccine was first discussed. Here, we describe systematic screening and evaluation of protective effects of engineered Lactobacillus against S. aureus infection in terms of different delivery vehicle strains and S. aureus antigens and in localized and systemic infection models. Limosilactobacillus reuteri WXD171 was selected as the delivery vehicle strain based on its tolerance of the gastrointestinal environment, adhesion ability, and antimicrobial activities in vitro and in vivo. We designed, constructed, and evaluated engineered L. reuteri strains expressing various S. aureus antigens. Among these, engineered L. reuteri WXD171-IsdB displayed effective protection against S. aureus-induced localized infection (pneumonia and skin infection) and, furthermore, a substantial survival benefit in systemic infection (sepsis). WXD171-IsdB induced mucosal responses in gut-associated lymphoid tissues, as evidenced by increased production of secretory IgA and interleukin 17A (IL-17A) and proliferation of lymphocytes derived from Peyer's patches. The probiotic L. reuteri-based oral vaccine appears to have strong potential as a prophylactic agent against S. aureus infections. Our findings regarding utilization of Lactobacillus delivery system in S. aureus vaccine development support the usefulness of this live vaccination strategy and its potential application in next-generation vaccine development. IMPORTANCE We systematically screened and evaluated protective effects of engineered Lactobacillus against S. aureus infection in terms of differing delivery vehicle strains and S. aureus antigens and in localized and systemic infection models. Engineered L. reuteri was developed and showed strong protective effects against both types of S. aureus-induced infection. Our findings regarding the utilization of a Lactobacillus delivery system in S. aureus vaccine development support the usefulness of this live vaccination strategy and its potential application in next-generation vaccine development.

Escalation of antimicrobial resistance among MRSA part 2: focus on infections and treatment

INTRODUCTION

MRSA is associated with causing a variety of infections including skin and skin structure infections, catheter and device-related (e.g. central venous catheter, prosthetic heart valve) infections, infectious endocarditis, blood stream infections, bone, and joint infections (e.g. osteomyelitis, prosthetic joint, surgical site), central nervous system infections (e.g. meningitis, brain/spinal cord abscess, ventriculitis, hydrocephalus), respiratory tract infections (e.g. hospital-acquired pneumonia, ventilator-associated pneumonia), urinary tract infections, and gastrointestinal infections. The emergence and spread of multidrug resistant (MDR) MRSA clones has limited therapeutic options. Older agents such as vancomycin, linezolid and daptomycin and a variety of newer MRSA antimicrobials and combination therapy are available to treat serious MRSA infections.

AREAS COVERED

The authors discuss infections caused by MRSA as well as common older and newer antimicrobials and combination therapy for MRSA infections. A literature search of MRSA was performed via PubMed (up to September 2022), using the keywords: antimicrobial resistance; β-lactams; multidrug resistance, Staphylococcus aureus, vancomycin; glycolipopeptides.

EXPERT OPINION

Innovation, discovery, and development of new and novel classes of antimicrobial agents are critical to expand effective therapeutic options. The authors encourage the judicious use of antimicrobials in accordance with antimicrobial stewardship programs along with infection-control measures to minimize the spread of MRSA.

Multidrug-Resistant Bacteria on Critically Ill Patients with Sepsis at Hospital Admission: Risk Factors and Effects on Hospital Mortality

Purpose

To evaluate the effect of MDRO infection on hospital mortality and the risk factors among critically ill patients with sepsis at hospital admission.

Patients and Methods

A cross-sectional study was performed between April 2019 and May 2020, followed by a cohort to evaluate hospital mortality that prospectively included all consecutive patients 18 years or older with sepsis admitted within 48 hours of hospital admission to an adult ICU in Brazil. Patients' characteristics, blood samples within one hour of ICU admission, and microbiological results within 48h of hospital admission were collected. In addition, descriptive statistics, binary logistic regression, and propensity score matching were performed.

Results

At least one MDRO was isolated in 85 patients (9.8%). The extended-spectrum beta-lactamase-producing Enterobacterales are the most frequent organism (56.1%). Hypoxemic acute respiratory failure (OR 1.87, 95% CI 1.02-3.40, p = 0.04), Glasgow Coma Score below 15 (OR 2.57, 95% CI 1.38-4.80, p < 0.01), neoplasm (OR 2.66, 95% CI 1.04-6.82, p = 0.04) and hemoglobin below 10.0 g/dL (OR 1.82, 95% CI 1.05-3.16, p = 0.03) were associated with increased MDRO. Admission from the Emergency Department (OR 0.25, 95% CI 0.14-0.43, p < 0.01) was associated with decreased MDRO. In the multivariate analysis, MDRO at hospital admission increased hospital mortality (OR 2.80, 95% CI 1.05-7.42, p = 0.04). After propensity score-matching adjusted to age, APACHE II, SOFA, and dementia, MDRO at hospital admission was associated with significantly high hospital mortality (OR 2.80, 95% CI 1.05-7.42, p = 0.04). The E-value of adjusted OR for the effect of MDRO infection on hospital mortality was 3.41, with a 95% CI of 1.31, suggesting that unmeasured confounders were unlikely to explain the entirety of the effect.

Conclusion

MDRO infection increased hospital mortality, and MDRO risk factors should be accessed even in patients admitted to ICU within 48 hours of hospital admission.

Staphylococcal Corneocyte Adhesion: Assay Optimization and Roles of Aap and SasG Adhesins in the Establishment of Healthy Skin Colonization

Staphylococcus aureus is an opportunistic pathogen that causes the majority of wound and soft tissue infections. The accumulation-associated protein (Aap) from S. epidermidis and surface protein G (SasG) from S. aureus are cell wall-anchored (CWA) proteins known to be important in adhesion to healthy corneocytes from human skin. We investigated the mechanisms by which S. aureus colonizes healthy human skin by developing an optimized corneocyte adhesion assay. Trypan blue was used for enhanced red autofluorescent visualization of corneocytes with an overlay of green-fluorescent bacteria. The percent area of bacterial adhesion for images acquired by a fluorescence microscope was quantified using Fiji ImageJ. Using this optimized imaging procedure, differences in adhesion between various species and strains of staphylococci were measured. The ability of purified SasG to reduce Staphylococcus epidermidis adhesion was investigated in order to determine if these CWA proteins can compete for binding sites. To further test CWA-mediated adhesion, we engineered a nonadhering S. carnosus strain to express full-length SasG from two methicillin-resistant S. aureus (MRSA) strains. Finally, we demonstrated that the SasG A domain was a critical region of this surface protein for adherence to healthy human corneocytes. The developed imaging and expression methods are useful for studying staphylococcal adhesion to healthy human skin and have the potential to be used with a wide variety of fluorescently labeled organisms on both healthy and disease-state (such as atopic dermatitis) corneocytes. IMPORTANCE The skin is the largest organ of the human body and acts as a shield against hazards such as harmful bacteria like Staphylococcus aureus. A diverse skin microbiota and immune cross talk control S. aureus numbers. S. aureus can bind to healthy skin and subsequently proliferate when the skin barrier is compromised, such as in a wound or in patients with atopic dermatitis (AD). It is important to understand these mechanisms in an effort to prevent pathogenic bacteria from causing infection. We describe an augmented corneocyte adhesion assay using fluorescence microscopy to study binding of various staphylococcal species to healthy human skin cells. In addition, we tested the ability of homologous proteins from different staphylococcal species to reduce binding, and developed a new S. carnosus expression system to test individual protein binding properties. Our newly developed methods and findings will enhance the understanding of how staphylococci bind to healthy human skin.

International Validation of a Methicillin-Resistant Staphylococcus aureus Risk Assessment Tool for Skin and Soft Tissue Infections

INTRODUCTION

To promote judicious prescribing of methicillin-resistant Staphylococcus aureus (MRSA)-active therapy for skin and soft tissue infections (SSTI), we previously developed an MRSA risk assessment tool. The objective of this study was to validate this risk assessment tool internationally.

METHODS

A multicenter, prospective cohort study of adults with purulent SSTI was performed at seven international sites from July 2016 to March 2018. Patient MRSA risk scores were computed as follows: MRSA infection/colonization history (2 points); previous hospitalization, previous antibiotics, chronic kidney disease, intravenous drug use, human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), diabetes with obesity (1 point each). Predictive performance of MRSA surveillance percentage, MRSA risk score, and estimated MRSA probability (surveillance percentage adjusted by risk score) were quantified using the area under the receiver operating characteristic curves (aROC) and compared. Performance characteristics of different risk score thresholds across varying baseline MRSA prevalence were examined.

RESULTS

Two hundred three patients were included. Common SSTI were wounds (28.6%), abscess (25.1%), and cellulitis with abscess (20.7%). Patients with higher risk scores were more likely to have MRSA (P < 0.001). The MRSA risk score aROC (95%CI) [0.748 (0.678-0.819)] was significantly greater than MRSA surveillance percentage [0.646 (0.569-0.722)] (P = 0.016). Estimated MRSA probability aROC [0.781 (0.716-0.845)] was significantly greater than surveillance percentage (P < 0.001) but not the risk score (P = 0.192). The estimated negative predictive value (NPV) of an MRSA score ≥ 1 (i.e., a score of 0) was greater than 90% when MRSA prevalence was 30% or less.

CONCLUSION

The MRSA risk score and estimated MRSA probability were significantly more predictive of MRSA compared with surveillance percentage. An MRSA risk score of zero had high predictive value and could help avoid unnecessary empiric MRSA coverage in low-acuity patients. Further study, including impact of such risk assessment tools on prescribing patterns and outcomes are required before implementation.

Cephalosporins as key lead generation beta-lactam antibiotics

Abstract

Antibiotics are antibacterial compounds that interfere with bacterial growth, without harming the infected eukaryotic host. Among the clinical agents, beta-lactams play a major role in treating infected humans and animals. However, the ever-increasing antibiotic resistance crisis is forcing the pharmaceutical industry to search for new antibacterial drugs to combat a range of current and potential multi-resistant bacterial pathogens. In this review, we provide an overview of the development, innovation, and current status of therapeutic applications for beta-lactams with a focus on semi-synthetic cephalosporins. Cephalosporin C (CPC), which is a natural secondary metabolite from the filamentous fungus Acremonium chrysogenum, plays a major and demanding role in both producing modern antibiotics and developing new ones. CPC serves as a core compound for producing semi-synthetic cephalosporins that can control infections with different resistance mechanisms. We therefore summarize our latest knowledge about the CPC biosynthetic pathway and its regulation in the fungal host. Finally, we describe how CPC serves as a key lead generation source for the in vitro and better, in vivo synthesis of 7-aminocephalosporanic acid (7-ACA), the major core compound for the pharmaceutical synthesis of current and future semi-synthetic cephalosporins.

Key points

•Latest literature on cephalosporin generations

•Biotechnical production of cephalosporins

•In vivo production of 7-ACA

The association between antibiotics and community-associated Staphylococcus aureus colonization in the United States population: Analysis of the National Health and Nutrition Examination Survey (NHANES)

Staphylococcus aureus nasal colonization is a seriously opportunistic infection. However, there is a lack of research of relationship between antibiotics and S aureus colonization in the general population. Through a cross-sectional investigation, this study intends to establish the parameters related to S aureus nasal colonization, specifically the function antibiotics play in colonization. The key information from 2001 to 2004 was abstracted from National Health and Nutrition Examination Survey (NHANES), including information on general demographics, health care status, antibiotic prescription, diabetes, alcohol consumption, and tobacco smoke exposure. The participants colonized with methicillin-susceptible S aureus (MSSA), or methicillin-resistant S aureus (MRSA) were defined as the case group, and the control group was subjects without positive S aureus colonization. Univariate and multivariate logistic regression models were used to identify the variables associated with MSSA and MRSA colonization. The records of 18,607 individuals were included, involving 13,205 cases without S aureus colonization, 5195 cases with MSSA, and 207 cases with MRSA. In the multivariate logistic regression analysis, the risk of MSSA colonization was significantly reduced with fluoroquinolone use (75% risk reduction, P = .02), sulfonamide use (98% risk reduction, P < .01), tetracycline use (81% risk reduction, P < .01) and antibiotic combination therapy (risk reduction 76%, P < .01). Female, race and total household size were strongly associated with MSSA carriage. On the other hand, regarding MRSA colonization, fluoroquinolone use, long-term care, and former smoker were positively associated with MRSA colonization, while high income was negatively associated with MRSA colonization. More proper use of broad-spectrum antibiotics contributes to reducing MSSA colonization. Former smokers should also practice better personal hygiene to limit the possibility of MRSA colonization.

Group B Streptococcus adaptation promotes survival in a hyperinflammatory diabetic wound environment

Diabetic wounds have poor healing outcomes due to the presence of numerous pathogens and a dysregulated immune response. Group B Streptococcus (GBS) is commonly isolated from diabetic wound infections, but the mechanisms of GBS virulence during these infections have not been investigated. Here, we develop a murine model of GBS diabetic wound infection and, using dual RNA sequencing, demonstrate that GBS infection triggers an inflammatory response. GBS adapts to this hyperinflammatory environment by up-regulating virulence factors including those known to be regulated by the two-component system covRS, such as the surface protein pbsP, and the cyl operon, which is responsible for hemolysin/pigmentation production. We recover hyperpigmented/hemolytic GBS colonies from the murine diabetic wound, which we determined encode mutations in covR. We further demonstrate that GBS mutants in cylE and pbsP are attenuated in the diabetic wound. This foundational study provides insight into the pathogenesis of GBS diabetic wound infections.

Does a Positive Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Screen Predict the Risk for MRSA Skin and Soft Tissue Infection?

Background:

Skin and soft tissue infections (SSTIs) are often caused by gram-positive bacteria that colonize the skin. Given the overuse of antibiotics, SSTIs are increasingly caused by resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Guidance on the utility of MRSA nasal screening for MRSA SSTI is limited.

Objective:

To determine whether MRSA nasal screening predicts the risk of MRSA SSTIs.

Methods:

This was a single-center, retrospective cohort study of adult patients with an SSTI diagnosis that had MRSA nasal screening and wound cultures obtained within 48 hours of starting antibiotics. Sensitivity, specificity, positive and negative predictive value, and positive and negative likelihood ratios were calculated using VassarStats. Pretest and posttest probabilities were estimated with Microsoft Excel.

Results:

A total of 884 patient encounters were reviewed between December 1, 2018, and October 31, 2021, and 300 patient encounters were included. The prevalence of MRSA SSTI was 18.3%. The MRSA nasal colonization had a sensitivity of 63.6%, specificity of 93.9%, positive predictive value of 70.0% (95% CI = 55.2%-81.7%), negative predictive value of 92.0% (95% CI = 87.7%-94.9%), positive likelihood ratio of 10.39 (95% CI = 6.12-17.65), negative likelihood ratio of 0.39 (95% CI = 0.27-0.55), positive posttest probability of 70.0%, and negative posttest probability of 8.0%.

Conclusions:

Given the high positive likelihood ratio, a positive MRSA nasal screen was associated with a large increase in the probability of MRSA SSTI at our institution, and a negative MRSA nasal screen was associated with a small but potentially significant decrease in the probability of MRSA SSTI.

Clinical features and antimicrobial treatment of skin infections caused by Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus

Skin infections caused by Panton-Valentine leukocidin (PVL)-positive methicillin-resistant Staphylococcus aureus (MRSA), especially the USA300 clone, have been increasing in Japan. To prevent an epidemic of PVL-positive MRSA, rapid diagnosis and effective antimicrobial therapy are essential. However, the clinical features of, and antimicrobial efficacy against, these skin infections are not well understood in Japan. Here, we report 10 cases of skin infections caused by PVL-positive MRSA that presented over a two-year period in our clinic. Genetic analyses revealed that 90% of the PVL-positive MRSA strains were identified as USA300 and its related clones. Notably, 70% of the patients had atopic dermatitis (AD) as an underlying disease. Average durations of antimicrobial therapy for AD patients (10.6 weeks) were 2.9-fold longer than those for non-AD patients (3.7 weeks). However, all cases were improved by a long-term course of fosfomycin, minocycline, doxycycline, and/or rifampicin. Our data suggest that AD may be an important risk factor for intractable skin infections caused by PVL-positive MRSA.

Inorganic nanosheets facilitate humoral immunity against medical implant infections by modulating immune co-stimulatory pathways

Strategies to manipulate immune cell co-inhibitory or co-activating signals have revolutionized immunotherapy. However, certain immunologically cold diseases, such as bacterial biofilm infections of medical implants are hard to target due to the complexity of the immune co-stimulatory pathways involved. Here we show that two-dimensional manganese chalcogenophosphates MnPSe₃ (MPS) nanosheets modified with polyvinylpyrrolidone (PVP) are capable of triggering a strong anti-bacterial biofilm humoral immunity in a mouse model of surgical implant infection via modulating antigen presentation and costimulatory molecule expression in the infectious microenvironment (IME). Mechanistically, the PVP-modified MPS (MPS-PVP) damages the structure of the biofilm which results in antigen exposure by generating reactive oxidative species, while changing the balance of immune-inhibitory (IL4I1 and CD206) and co-activator signals (CD40, CD80 and CD69). This leads to amplified APC priming and antigen presentation, resulting in biofilm-specific humoral immune and memory responses. In our work, we demonstrate that pre-surgical neoadjuvant immunotherapy utilizing MPS-PVP successfully mitigates residual and recurrent infections following removal of the infected implants. This study thus offers an alternative to replace antibiotics against hard-to-treat biofilm infections.

Genomic Epidemiology Suggests Community Origins of Healthcare-Associated USA300 Methicillin-Resistant Staphylococcus aureus

BACKGROUND

Hospital-onset (HO) methicillin-resistant Staphylococcus aureus (MRSA) infections have declined over the past decade due to infection control strategies; community-onset (CO) and healthcare-associated community-onset (HACO) MRSA, particularly USA300, has declined less. We examined the role of community strains to explain the difference.

METHODS

We performed whole-genome sequencing (WGS) on MRSA clinical isolates from Cook County Health patients during 2011-2014. We defined infections as CO, HO, or HACO epidemiologically. We integrated genomic, community exposure, and statewide hospital discharge data to infer MRSA origin.

RESULTS

Among 1020 individuals with available WGS, most were USA300 wound infections (580 CO, 143 HO, 297 HACO). USA300 HO, CO, and HACO infections were intermixed on the USA300 phylogeny, consistent with common strains circulating across community and healthcare settings. Community exposures (eg, substance abuse, incarceration, homelessness) were associated with HACO and HO infections, and genetically linked individuals from both groups had little overlap in healthcare facilities, supporting community origins. Most repeat infections-over months to years-occurred in individuals persistently carrying their own strains. These individuals were more likely to have genetic linkages, suggesting a role of persistent colonization in transmission.

CONCLUSIONS

Efforts to reduce presumed nosocomial USA300 spread may require understanding and controlling community sources and transmission networks, particularly for repeat infections.

Lymph-derived chemokines direct early neutrophil infiltration in the lymph nodes upon Staphylococcus aureus skin infection

A large number of neutrophils infiltrate the lymph node (LN) within 4 h after Staphylococcus aureus skin infection (4 h postinfection [hpi]) and prevent systemic S. aureus dissemination. It is not clear how infection in the skin can remotely and effectively recruit neutrophils to the LN. Here, we found that lymphatic vessel occlusion substantially reduced neutrophil recruitment to the LN. Lymphatic vessels effectively transported bacteria and proinflammatory chemokines (i.e., Chemokine [C-X-C motif] motif 1 [CXCL1] and CXCL2) to the LN. However, in the absence of lymph flow, S. aureus alone in the LN was insufficient to recruit neutrophils to the LN at 4 hpi. Instead, lymph flow facilitated the earliest neutrophil recruitment to the LN by delivering chemokines (i.e., CXCL1, CXCL2) from the site of infection. Lymphatic dysfunction is often found during inflammation. During oxazolone (OX)-induced skin inflammation, CXCL1/2 in the LN was reduced after infection. The interrupted LN conduits further disrupted the flow of lymph and impeded its communication with high endothelial venules (HEVs), resulting in impaired neutrophil migration. The impaired neutrophil interaction with bacteria contributed to persistent infection in the LN. Our studies showed that both the flow of lymph from lymphatic vessels to the LN and the distribution of lymph in the LN are critical to ensure optimal neutrophil migration and timely innate immune protection in S. aureus infection.

Proteome profiling of evolved methicillin-resistant Staphylococcus aureus strains with distinct daptomycin tolerance and resistance phenotypes

Methicillin-resistant Staphylococcus aureus (MRSA) is a highly dangerous pathogen, and daptomycin has been increasingly used to treat its infections in clinics. Recently, several groups have shown that tolerance and resistance of microbes can evolve rapidly under cyclic antibiotic exposure. We have previously shown that the same tolerance and resistance development occurs in MRSA treated with daptomycin in an adaptive laboratory evolution (ALE) experiment. In the present study, we performed proteomic analysis to compare six daptomycin-tolerant and resistant MRSA strains that were evolved from the same ancestral strain. The strain with a higher tolerance level than the others had the most different proteome and response to antibiotic treatment, resembling those observed in persister cells, which are small subpopulations of bacteria that survive lethal antibiotics treatment. By comparing the proteome changes across strains with similar phenotypes, we identified the key proteins that play important roles in daptomycin tolerance and resistance in MRSA. We selected two candidates to be confirmed by gene overexpression analysis. Overexpression of EcsA1 and FabG, which were up-regulated in all of the tolerant evolved strains, led to increased daptomycin tolerance in wild-type MRSA. The proteomics data also suggested that cell wall modulations were implicated in both resistance and tolerance, but in different ways. While the resistant strains had peptidoglycan changes and a more positive surface charge to directly repel daptomycin, the tolerant strains possessed different cell wall changes that do not involve the peptidoglycan nor alterations of the surface charge. Overall, our study showed the differential proteome profiles among multiple tolerant and resistant strains, pinpointed the key proteins for the two phenotypes and revealed the differences in cell wall modulations between the daptomycin-tolerant/resistant strains.

Skin infections in Europe: a retrospective study of incidence, patient characteristics and practice patterns

OBJECTIVE

Acute bacterial skin and skin structure infections (ABSSSIs) are associated with considerable morbidity and a heavy healthcare burden. The primary objectives of this two-phase study were to determine the incidence of skin infections and ABSSSIs in hospitalized patients (Phase A), and to describe the characteristics and treatment of hospitalized patients with ABSSSIs (Phase B).

METHODS

This non-interventional, retrospective study was based on data collected from adult patients hospitalized for skin infections in six European countries (Czech Republic, Greece, Italy, Portugal, Russia and Spain) between January 2014 and June 2016.

RESULTS

In Phase A, the total hospital incidence of skin infections and ABSSSIs was 2.4 and 1.8 per 1000 patient-days, respectively. Overall, 73.6% of 50,469 hospitalizations for skin infections were for ABSSSIs. Among the 750 patients with ABSSSIs included in Phase B, Gram-positive bacteria were isolated in 24.9%, most commonly methicillin-susceptible Staphylococcus aureus (11.5%). Empirical therapy was administered to 98.1% of patients, most often with a penicillin, with or without a β-lactamase inhibitor (42.1%). Complete cure was achieved in 46.5% and 34.5% of patients after initial treatment and treatment modification, respectively. Overall, 22.7% of patients had at least one additional ABSSSI-related hospitalization, 47.1% of patients visited the emergency room, 19.3% of patients visited primary care clinics, and 34.8% of patients visited a specialist.

CONCLUSION

Treatment of ABSSSIs in Europe is associated with a heavy healthcare burden, highlighting the need for optimized management strategies that may reduce healthcare utilization.

Rate of methicillin-resistant Staphylococcus aureus in pediatric emergency departments in Spain

INTRODUCTION

Staphylococcus aureus is a common germ in bacterial infections in children. The rate of methicillin-resistant S. aureus (MRSA) is increasing lately.

OBJECTIVES

The main aim is to know the rate of positive cultures to MRSA in Spanish pediatric emergency departments. The secondary aims are to analyse the risk factors for MRSA isolation (patient origin, history of hospitalization or surgery in the previous 90 days, antibiotherapy in the previous 60 days, presence of comorbidity, invasive devices, prior MRSA isolation) and to analyse the morbidity of these infections.

METHODOLOGY

Retrospective multicenter study (07/01/2017-06/30/2018) with review of patient histories with isolation of S. aureus in samples of any origin obtained in 8 pediatric emergency departments of the Infectious Diseases Working Group of the Spanish Society of pediatric Emergencies.

RESULTS

During this period, S. aureus was detected in 403 patients (average age 75.8 ± 59.2 months; 54.8% male): 28.8% hospital-related infections (HRI) and 71.2% community-related infections (CRI). Overall, MRSA rate was 16.6% (95% CI: 13-20.2%); 18.1% in HRI and 16.2% in CRI (p > 0.05). The highest rates of MRSA were obtained in skin abscesses (29.3%, CI 95%: 21.8-36.8%), patients not born in Spain (52%; CI 95%: 32-72%) or patients with a previous MRSA infection (90%; CI 95% 71.4-100%). 167 (41%) patients were admitted, 12 (3%) had complications and 4 (1%) suffered sequels. There were no deaths.

CONCLUSIONS

The overall MRSA rate was one in 6 staphylococcal infections. Higher MRSA rates were detected in samples of suppurating skin injuries and in foreign children or in children with a history of previous MRSA infection. In suppurative skin lesions, early drainage is essential and the change to an antibiotic with MRSA coverage should be considered if the evolution is inadequate.

Fate of antibiotic resistant genes in wastewater environments and treatment strategies - A review

Antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) have emerged in aquatic environments through the discharge of large amounts of antibiotics into wastewater. Well-designed wastewater treatment plants (WWTPs) with effective treatment processes are essential to prevent the release of ARGs directly into the environment. Although some systematic sequential treatment methods are used to remove ARGs, considerable gaps in removal mechanisms will be discussed. Therefore, deep analysis and discussion of various treatment methods are required to understand the ARGs removal mechanisms. In this manuscript, the role of antibiotics and the resistance mechanism of ARB are discussed in depth. In addition, the fate of ARGs in an aquatic environment and detection methods are compared comprehensively and discussed. In particular, the advantages and disadvantages of various methods are summarized and reviewed critically. Finally, combined technologies, such as advanced oxidation process (AOP) with biochemical systems, membrane separation with electrochemical AOP, ultrafiltration (UF) membrane coupled with photocatalytic treatment, and UF membrane separation coupled with sonication, are introduced. Overall, low-energy anaerobic treatment reactors with any of the above combined treatments might reduce the discharge of large quantities of ARGs into the environment. Finally, this review provides valuable insights for better ARG removal technologies by introducing combined effective treatment strategies used in real WWTPs.

Changes in the Genotypic Characteristics of Community-Acquired Methicillin-Resistant Staphylococcus aureus Collected in 244 Medical Facilities in Japan between 2010 and 2018: a Nationwide Surveillance

Although community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged worldwide, no nationwide CA-MRSA surveillance has been conducted in Japan to determine the changes in its molecular characteristics over time. We aimed to characterize the molecular epidemiology of Panton-Valentine leucocidin (PVL)-positive CA-MRSA strains collected from across Japan in the past decade. We isolated 1,770 MRSA strains from the skin and pus samples of outpatients of 244 medical facilities in 31 prefectures between 2010 and 2018 (2010, 2012, 2014, 2016, and 2018). Regions, hospitals, and periods in which strains were isolated and patient age group and sex were tabulated. Staphylococcal cassette chromosome mec (SCCmec) typing, detection of virulence factor genes, and antimicrobial susceptibility testing were performed. Whole-genome analysis was performed for the PVL-positive strains isolated in 2018. All strains harbored the mecA gene. Compared to that in 2010, the percentage of SCCmec type IV increased in 2018, with a corresponding increase in the proportion of PVL-positive strains (10% to 26%). Of the isolates obtained in 2018, clonal complex 8 (CC8) was dominant among PVL-positive strains. Core-genome single-nucleotide polymorphism analysis, using whole-genome sequencing, suggested that the CC8 PVL-positive strains spread throughout Japan over the last decade. Furthermore, a unique ST22 clone carrying both the PVL- and toxic shock syndrome toxin-1-encoding genes has emerged. We demonstrated that the molecular epidemiology of CA-MRSA in Japan differs from that in Europe and the United States; thus, it is crucial to monitor the trend of changes in CA-MRSA characteristics in Japan.

IMPORTANCE Community-associated MRSA, which is a multidrug-resistant organism and can cause infections in otherwise-healthy individuals, has become a global problem. This paper describes a nationwide surveillance conducted in Japan to investigate changes in molecular epidemiological characteristics of CA-MRSA over the past decade and provides a detailed review of the characteristics of Panton-Valentine leucocidin (PVL)-positive strains isolated in 2018. Although CA-MRSA is rare in Japan to date, we found that the isolation of PVL-positive strains has been increasing over the past decade. In particular, the PVL-positive strains wherein CC8 was dominant exhibited high interstrain similarity, suggesting that a limited number of clones have spread over the past decade. Furthermore, a unique ST22 clone carrying both PVL-encoding and toxic shock syndrome toxin-1-encoding genes has emerged. This study shows that various changes can be observed when molecular epidemiological analysis, combined with next-generation sequencing, is conducted over a long period.

Genome Sequences of Two Methicillin-Sensitive Staphylococcus aureus Healthy Skin Isolates

The USA300 and USA600 clonal lineages are the cause of many serious Staphylococcus aureus infections. Here, we report the complete genomes of two methicillin-sensitive S. aureus strains isolated from the healthy skin of adults in Colorado, which are most phylogenetically similar to the USA300 and USA600 lineages.

NWMN2330 May Be Associated with the Virulence of Staphylococcus aureus by Increasing the Expression of hla and saeRS

Introduction

Staphylococcus aureus is an opportunistic pathogen that can cause life-threatening bloodstream infections such as sepsis and endocarditis. In recent years, the emergence and increase of methicillin-resistant and multidrug-resistant S. aureus has posed a great challenge to the antibiotic treatment of infectious diseases. Anti-virulence strategies targeting virulence factors are an effective new therapy for the treatment of S. aureus infections.

Results

In this study, we constructed a NWMN2330 deletion mutant (Newman-ΔNWMN2330) and a complement (Newman-ΔNWMN2330-C) of S. aureus Newman to study the role of NWMN2330 in the virulence of S. aureus. Through transcriptome sequencing, it was found that the expression of 224 genes in Newman-ΔNWMN2330 was significantly different (>2-fold) compared with S. aureus Newman, and these differentially expressed genes were related to multiple functions of S. aureus. And we found that NWMN2330 could positively regulate the expression of S. aureus hla gene. Therefore, the deletion mutant Newman-ΔNWMN2330 exhibited lower hemolytic activity and lower α-toxin production than Newman. Newman-ΔNWMN2330 also exhibited lower lethality and pathogenicity in worm survival experiments and nude mouse skin abscess model. RT-qPCR results showed that compared with the wild-type strain, the expression of saeRS and hla in Newman-ΔNWMN2330 strain was significantly reduced at the mRNA level, which preliminarily indicated that NWMN2330 promoted the expression of hla by up-regulating saeRS.

Discussion

In general, our results indicated that NWMN2330 may be associated with the virulence of Staphylococcus aureus by increasing the expression of hla and saeRS.

Invasive pectoral abscess and costal osteomyelitis with bloodstream infection caused by methicillin-resistant Staphylococcus aureus after nasal septoplasty in an immunocompetent adult patient

There are few reports of multilocus sequence type (ST) 5/staphylococcal cassette chromosome (SCC) mec type IVc/toxic shock syndrome toxin (TSST)-1- positive methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections. We report a case of community-onset MRSA (CO-MRSA) bloodstream infection in a healthy 41-year-old Japanese man after nasal septoplasty, followed by pectoral abscess and costal osteomyelitis. The patient presented with right anterior chest pain and fever. After admission, MRSA was isolated from two sets of blood cultures, and vancomycin was administered. On the fifth day, contrast-enhanced computed tomography (CT) scan and contrast-enhanced magnetic resonance imaging (MRI) scan showed an abscess in the right anterior chest to the right subpleural region. The dosage of vancomycin (4 g/day) did not reach the effective blood concentration; therefore, there was a switch to daptomycin. On the 23rd day, contrast-enhanced MRI revealed osteomyelitis of the right first rib, and as a result, linezolid was initiated. Two weeks later, contrast-enhanced CT of the chest showed improvement in the abscess. The patient was treated for 6 weeks during hospitalization and then switched to minocycline for 10 weeks. Molecular characterization of this isolate showed that it was ST5/SCCmec type IVc/TSST-1-positive/Panton-Valentine leucocidin (PVL)-negative. PVL-negative CO-MRSA can lead to hematogenous osteomyelitis and abscess even if the patient is immunocompetent, and if isolated from blood cultures, it is important to repeat imaging studies, even if the initial imaging studies were normal. It is possible that this strain contributes to the pathogenesis of invasive CO-MRSA, but further case accumulation is needed.

Using tea nanoclusters as β-lactamase inhibitors to cure multidrug-resistant bacterial pneumonia: A promising therapeutic strategy by Chinese materioherbology

β-lactamase, a kind of hydrolase in multi-drug resistant pathogens, can hydrolyze β-lactam antibiotics and make these kinds of antibiotics invalid. Small-molecular inhibitors about the enzyme and their mechanism are widely investigated but they may result in unavoidable adverse reactions and drug-resistance. Herein, we propose a new therapeutic strategy of Chinese materioherbology, in which herbal medicine or traditional Chinese medicinal herbs can be employed as biological functional materials or refreshed/excited by means of materialogy. Natural tea nanoclusters (TNCs) were extracted from tea to inhibit β-lactamase. Different from the mechanism of small-molecular inhibitors inhibiting enzymes by binding to the corresponding active sites, the TNCs as a cap cover the protein pocket and create a spatial barrier between the active sites and antibiotics, which was named "capping-pocket" effect. TNCs were combined with amoxicillin sodium (Amo) to treat the methicillin-resistant Staphylococcus aureus (MRSA) pneumonia in mice. This combinatorial therapy remarkably outperforms antibiotic monotherapy in reducing MRSA infections and the associated inflammation in mice. The therapeutic strategy exhibited excellent biosafety, without any side effects, even in piglets. Hence, TNCs have great clinical value in potentiating β-lactam antibiotic activity for combatting multi-drug resistant pathogen infections and the "pocket capping" effect can guide the design of new enzyme inhibitors in near future.

Distribution and drug sensitivity of pathogenic bacteria in diabetic foot ulcer patients with necrotizing fasciitis at a diabetic foot center in China

Background

Diabetic foot ulcer is one of the major complications for patients with diabetes, and has become an important cause of non-traumatic amputation. Necrotizing fasciitis is a life-threatening soft-tissue infection involving the fascia and subcutaneous tissue. When diabetic foot ulcers are complicated by necrotizing fasciitis (DNF), this increases the risk for amputation and mortality, making DNF treatment more complicated, and eventually leading to amputation and mortality. However, studies on pathogenic bacteria’s distribution and drug sensitivity in DNF patients remain lacking. This study investigated the distribution and susceptibility of pathogenic bacteria in DNF patients, and provided empirical antibacterial guidance for the clinic.

Methods

In a single diabetic foot center, the results from microbial cultures and drug susceptibility tests of patients with DNF from October 2013 to December 2020 were collected and analyzed.

Results

A total of 101 DNF patients were included in this study, of whom 94 had positive culture test results. A total of 124 pathogens were cultured, including 76 Gram-positive bacterial strains, 42 Gram-negative bacterial strains, and six fungal strains. Polymicrobial infections accounted for 26.7% and monomicrobial infections accounted for 66.3%. Staphylococcus aureus was the most common bacterium isolated, followed by Enterococcus faecalis and Streptococcus agalactiae. Pseudomonas aeruginosa, Klebsiella pneumoniae, and Proteus mirabilis were the most common Gram-negative bacteria. Thirty-five strains of multi-drug resistant bacteria were isolated, representing 28.2% of the total isolates. Gram-positive bacteria were more sensitive to levofloxacin, moxifloxacin, vancomycin, teicoplanin, tigecycline, and linezolid, while Gram-negative bacteria were more sensitive to amikacin, piperacillin/tazobactam, cefoperazone/sulbactam, ceftazidime, cefepime, imipenem, and meropenem.

Conclusions

Gram-positive bacteria were the main bacteria isolated from DNF patients. The bacterial composition, the proportion of multi-drug resistant bacteria among the pathogens, and the high risk for amputation should be fully considered in the initial empirical medication, and broad-spectrum antibacterials are recommended.

Expression of Staphylococcal Virulence Genes In Situ in Human Skin and Soft Tissue Infections

BACKGROUND

Staphylococcus aureus, the most common pathogen in skin and soft tissue infections (SSTI), harbors many well-characterized virulence genes. However, the expression of many of them in SSTIs is unknown. In this study, S. aureus virulence genes expressed in SSTI were investigated.

METHODS

Fifty-three subjects presenting to the outpatient's care and emergency departments with a purulent SSTI at two medical centers in Wisconsin, USA, were enrolled in the study. Total mRNA was extracted from the purulent or swab materials, made into cDNA and sequenced on MiSeq platform. The relative cDNA counts to gmk and identifications of the transcripts were carried out with respect to USA300 reference genome and using SAMTOOLS v.1.3 and BWA, respectively.

RESULT

A significantly higher cDNA count was observed for many of the virulence and regulatory gene transcripts in the pus samples compared to the swab samples relative to the cDNA counts for gmk, a housekeeping gene. They were for lukS-PV (18.6 vs. 14.2), isaA (13.4 vs. 8.5), ssaA (4.8 vs. 3.1), hlgC (1.4 vs. 1.33), atl (17.7 vs. 8.33), clfA (3.9 vs. 0.83), eno (6.04 vs. 3.16), fnbA (5.93 vs. 0.33), saeS (6.3 vs. 1.33), saeR (5.4 vs. 3.33) and agrC (5.6 vs. 1.5).

CONCLUSIONS

A relative increase in the transcripts of several toxins, adhesion and regulatory genes with respect to a gmk in purulent materials suggests their role in situ during SSTIs, perhaps in an orchestrated manner.

New drugs for methicillin-resistant Staphylococcus aureus skin and soft tissue infections

PURPOSE OF REVIEW

Staphylococcus aureus is a pathogen incriminated in skin and soft tissue infections (SSTIs), with methicillin-resistant S. aureus (MRSA) becoming the predominant cause and representing a significant burden to the healthcare system. The last updated Infectious Diseases Society of America (IDSA) guidelines concerning MRSA infections and SSTIs management were published in 2011 and 2014, respectively. The UK updated guidelines for MRSA infection treatment were published in 2021. Older treatment options may be associated with toxicity and require frequent dosing. There is a paucity of recent reviews on the armamentarium of new agents for MRSA SSTIs treatment.

RECENT FINDINGS

Since 2005, several new antibiotics received a fast-track approval by the Food and Drug Administration (FDA) for SSTI treatment. These drugs include delafloxacin, omadacycline, tedizolid, ceftaroline, dalbavancin, oritavancin and telavancin. In this manuscript, we will review the data that led to these new drugs approval and discuss their advantages and disadvantages in MRSA SSTIs management.

SUMMARY

MRSA is a major cause of SSTIs. Several novel therapies covering MRSA were FDA-approved for SSTIs. However, the current IDSA guidelines for MRSA infection and SSTIs as well as the recently published UK guidelines on MRSA treatment only consider these drugs as alternative choices or do not mention them at all.

The Effect of Systemic Antibiotics for Suppurative Skin and Soft Tissue Infections on Skin Microbiome

Background

Skin and soft tissue infections (SSTIs) are very common bacterial infections. There are few data on the microbiome of persons with and without SSTIs and the effects of systemic antibiotic therapy.

Methods

We sampled the skin microbiome from 10 outpatients with acute suppurative SSTI before and after systemic antibiotic therapy and enrolled 10 matched controls. Samples were collected at 6 skin body sites (occipital scalp, axilla, interdigital hand web spaces, gluteal crease, inguinal creases, and popliteal fossa), 2 mucosal sites (throat, anterior nares), and the site of skin infection (for case subjects) at baseline and a week later after abscess incision, drainage, and oral antibiotics.

Result

Among 10 SSTI cases, mean age was 41.5 years and 3 had diabetes mellitus. The gluteal crease at baseline had higher α-diversity in controls vs cases (P = .039); β-diversity analysis showed significant differences in overall bacterial community composition (P = .046). However, at other body sites there were no significant differences by either α- or β-diversity. Systemic antibiotic use did not affect body site diversity indices except at the SSTI site (α-diversity increased, P = .001).

Conclusions

We surprisingly found no significant differences in microbiome comparing noninfected skin sites before and after systemic SSTI antibiotic therapy nor significant differences at noninfected skin sites between SSTI cases and uninfected controls. We also found minimal significant differences between microbiome diversity and bacterial signatures at noninfected skin sites between patients with acute skin infection and uninfected controls. Our findings challenge the dogma that systemic antibiotics impact the skin microbiome.