Unraveling the efficacy of verbascoside in thwarting MRSA pathogenicity by targeting sortase A.

In the fight against hospital-acquired infections, the challenge posed by methicillin-resistant Staphylococcus aureus (MRSA) necessitates the development of novel treatment methods. This study focused on undermining the virulence of S. aureus, especially by targeting surface proteins crucial for bacterial adherence and evasion of the immune system. A primary aspect of our approach involves inhibiting sortase A (SrtA), a vital enzyme for attaching microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) to the bacterial cell wall, thereby reducing the pathogenicity of S. aureus. Verbascoside, a phenylethanoid glycoside, was found to be an effective SrtA inhibitor in our research. Advanced fluorescence quenching and molecular docking studies revealed a specific interaction between verbascoside and SrtA, pinpointing the critical active sites involved in this interaction. This molecular interaction significantly impedes the SrtA-mediated attachment of MSCRAMMs, resulting in a substantial reduction in bacterial adhesion, invasion, and biofilm formation. The effectiveness of verbascoside has also been demonstrated in vivo, as shown by its considerable protective effects on pneumonia and Galleria mellonella (wax moth) infection models. These findings underscore the potential of verbascoside as a promising component in new antivirulence therapies for S. aureus infections. By targeting crucial virulence factors such as SrtA, agents such as verbascoside constitute a strategic and potent approach for tackling antibiotic resistance worldwide. KEY POINTS: • Verbascoside inhibits SrtA, reducing S. aureus adhesion and biofilm formation. • In vivo studies demonstrated the efficacy of verbascoside against S. aureus infections. • Targeting virulence factors such as SrtA offers new avenues against antibiotic resistance.

News sequences types of Staphylococcus aureus isolated from human pathologicals fluids in Burkina Faso.

Staphylococcus aureus is a pathogen with high epidemic potential frequently involved in nosocomials and communities infections. The pathogenicity of Staphylococcus aureus is due to both its ability to resist antibiotics and to Produce toxins. This work aims at studying the resistance and Molecular Epidemiology of Staphylococcus aureus. Antibiotic susceptibility of the 70 strains isolates of Staphylococcus aureus was determined by agar diffusion while Multiplex PCR and MLST were used to search toxin-coding genes and MRSA typing, respectively. 14.28% of isolates were multidrug resistant. Staphylococcus aureus showed high susceptibility to aminoglycoside and Macrolides familly. lukS-PV/lukF-PV and sea genes were detected in 45% and 3% of Staphylococcus aureus respectively. Ten (10) sequence types including ST5710, ST2430, ST5289, ST5786, ST6942, ST6943, ST6944, ST6945, ST6946, ST6947 have been reported. The study showed a diversity of antibiotic resistance phenotypes and a great diversity of MRSA clones causing infections.

Nasal carriage of virulent and multidrug resistant Staphylococcus aureus: a possible comorbidity of COVID-19.

BACKGROUND: Staphylococcus aureus (S. aureus) associated with COVID-19 has not been well documented. This cross-sectional study evaluated the association between nasal S. aureus carriage and COVID-19. METHODS AND RESULTS: Nasopharyngeal samples were collected from 391 participants presenting for COVID-19 test in Lagos, Nigeria, and S. aureus was isolated from the samples. Antimicrobial susceptibility test was done by disc diffusion method. All S. aureus isolates were screened for the presence of mecA, panton-valentine leucocidin (PVL) and toxic shock syndrome toxin (TSST) virulence genes by polymerase chain reaction. Staphylococcal protein A (spa) typing was conducted for all the isolates. Participants with COVID-19 had double the prevalence of S. aureus (42.86%) compared to those who tested negative (20.54%). A significant association was seen between S. aureus nasal carriage and COVID-19 (p = 0.004). Antimicrobial sensitivity results showed resistance to oxacillin (100%), cefoxitin (53%), and vancomycin (98.7%). However, only 41% of the isolates harbored the mecA gene, with SCCmecV being the most common SCCmec type. There was no association between the carriage of virulence genes and COVID-19. A total of 23 Spa types were detected, with t13249 and t095 being the two most common spa types. CONCLUSION: This study examined the association between nasal S. aureus carriage and SARS-COV-2 infection. Further research is required to fully explore the implications of S. aureus co-infection with COVID-19.

Collaborative Cross mice have diverse phenotypic responses to infection with Methicillin-resistant Staphylococcus aureus USA300.

Staphylococcus aureus (S. aureus) is an opportunistic pathogen causing diseases ranging from mild skin infections to life threatening conditions, including endocarditis, pneumonia, and sepsis. To identify host genes modulating this host-pathogen interaction, we infected 25 Collaborative Cross (CC) mouse strains with methicillin-resistant S. aureus (MRSA) and monitored disease progression for seven days using a surgically implanted telemetry system. CC strains varied widely in their response to intravenous MRSA infection. We identified eight 'susceptible' CC strains with high bacterial load, tissue damage, and reduced survival. Among the surviving strains, six with minimal colonization were classified as 'resistant', while the remaining six tolerated higher organ colonization ('tolerant'). The kidney was the most heavily colonized organ, but liver, spleen and lung colonization were better correlated with reduced survival. Resistant strains had higher pre-infection circulating neutrophils and lower post-infection tissue damage compared to susceptible and tolerant strains. We identified four CC strains with sexual dimorphism: all females survived the study period while all males met our euthanasia criteria earlier. In these CC strains, males had more baseline circulating monocytes and red blood cells. We identified several CC strains that may be useful as new models for endocarditis, myocarditis, pneumonia, and resistance to MRSA infection. Quantitative Trait Locus (QTL) analysis identified two significant loci, on Chromosomes 18 and 3, involved in early susceptibility and late survival after infection. We prioritized Npc1 and Ifi44l genes as the strongest candidates influencing survival using variant analysis and mRNA expression data from kidneys within these intervals.

Resistome, Virulome, and Clonal Variation in Methicillin-Resistant Staphylococcus aureus (MRSA) in Healthy Swine Populations: A Cross-Sectional Study.

This cross-sectional study investigates the methicillin-resistant Staphylococcus aureus (MRSA): its prevalence, antimicrobial resistance, and molecular characteristics in healthy swine populations in central Portugal. A total of 213 samples were collected from pigs on twelve farms, and MRSA prevalence was assessed using selective agar plates and confirmed via molecular methods. Antimicrobial susceptibility testing and whole genome sequencing (WGS) were performed to characterize resistance profiles and genetic determinants. Among the 107 MRSA-positive samples (83.1% prevalence), fattening pigs and breeding sows exhibited notably high carriage rates. The genome of 20 isolates revealed the predominance of the ST398 clonal complex, with diverse spa types identified. Antimicrobial susceptibility testing demonstrated resistance to multiple antimicrobial agents, including penicillin, cefoxitin, and tetracycline. WGS analysis identified a diverse array of resistance genes, highlighting the genetic basis of antimicrobial resistance. Moreover, virulence gene profiling revealed the presence of genes associated with pathogenicity. These findings underscore the significant prevalence of MRSA in swine populations and emphasize the need for enhanced surveillance and control measures to mitigate zoonotic transmission risks. Implementation of prudent antimicrobial use practices and targeted intervention strategies is essential to reducing MRSA prevalence and safeguarding public health. Continued research efforts are warranted to elucidate transmission dynamics and virulence potential, ultimately ensuring food safety and public health protection.

Genomic characterization of Staphylococcus aureus isolated from patients admitted to intensive care units of a tertiary care hospital: epidemiological risk of nasal carriage of virulent clone during admission.

We conducted a molecular epidemiological study of Staphylococcus aureus using whole-genome sequence data and clinical data of isolates from nasal swabs of patients admitted to the intensive care unit (ICU) of Hiroshima University hospital. The relationship between isolate genotypes and virulence factors, particularly for isolates that caused infectious diseases during ICU admission was compared with those that did not. The nasal carriage rates of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) in patients admitted to the ICU were 7.0% and 20.1%, respectively. The carriage rate of community-acquired (CA)-MRSA was 2.3%, accounting for 32.8% of all MRSA isolates. Whole-genome sequencing analysis of the MRSA isolates indicated that most, including CA-MRSA and healthcare-associated (HA)-MRSA, belonged to clonal complex (CC) 8 [sequence type (ST) 8] and SCCmec type IV. Furthermore, results for three disease foci (pneumonia, skin and soft tissue infection, and deep abscess) and the assessment of virulence factor genes associated with disease conditions [bacteremia, acute respiratory distress syndrome (ARDS), disseminated intravascular coagulopathy (DIC), and septic shock] suggested that nasal colonization of S. aureus clones could represent a risk for patients within the ICU. Particularly, MRSA/J and MSSA/J may be more likely to cause deep abscess infection; ST764 may cause ventilation-associated pneumonia, hospital-acquired pneumonia and subsequent bacteremia, and ARDS, and tst-1-positive isolates may cause DIC onset.IMPORTANCENasal colonization of MRSA in patients admitted to the intensive care unit (ICU) may predict the development of MRSA infections. However, no bacteriological data are available to perform risk assessments for Staphylococcus aureus infection onset. In this single-center 2-year genomic surveillance study, we analyzed all S. aureus isolates from nasal swabs of patients admitted to the ICU and those from the blood or lesions of in-patients who developed infectious diseases in the ICU. Furthermore, we identified the virulent clones responsible for causing infectious diseases in the ICU. Herein, we report several virulent clones present in the nares that are predictive of invasive infections. This information may facilitate the design of preemptive strategies to identify and eradicate virulent MRSA strains, reducing nosocomial infections within the ICU.

Molecular characterization of Staphylococcus aureus isolated from hospital-acquired infections in Ilam, Iran.

OBJECTIVE: This research study was undertaken to investigate antimicrobial resistance patterns and the prevalence of hospital-acquired infections (HAIs). The study focuses on common microorganisms responsible for HAIs and explores emerging challenges posed by antimicrobial drug-resistant isolates. METHODS: A comprehensive analysis of 123 patients with HAIs, hospitalized in surgical department and intensive care unit (ICU) at Imam Khomeini Hospital, Ilam, Iran, was conducted over a six-month period. Pathogenic bacterial isolates, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Staphylococcus aureus (VRSA), were isolated and subjected to antibiotic susceptibility testing. RESULTS: The study findings revealed a significant prevalence of multidrug-resistant (MDR) isolates, of which 73.3% were MRSA. Notably, 6.7% of S. aureus isolates exhibited resistance to vancomycin, indicating the emergence of VRSA. Respiratory infections were identified as the most prevalent HAI, constituting 34.67% of cases, often arising from extended ICU stays and invasive surgical procedures. Furthermore, patients aged 60 and above, particularly those associated with MDR, exhibited higher vulnerability to HAI. CONCLUSIONS: This research sheds light on the intricate interplay between drug resistance and HAI, highlighting the imperative role of rational antibiotic use and infection control in addressing this critical healthcare challenge.

The 3' UTR of vigR is required for virulence in Staphylococcus aureus and has expanded through STAR sequence repeat insertions.

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are alarmingly common, and treatment is confined to last-line antibiotics. Vancomycin is the treatment of choice for MRSA bacteremia, and treatment failure is often associated with vancomycin-intermediate S. aureus isolates. The regulatory 3' UTR of the vigR mRNA contributes to vancomycin tolerance and upregulates the autolysin IsaA. Using MS2-affinity purification coupled with RNA sequencing, we find that the vigR 3' UTR also regulates dapE, a succinyl-diaminopimelate desuccinylase required for lysine and peptidoglycan synthesis, suggesting a broader role in controlling cell wall metabolism and vancomycin tolerance. Deletion of the 3' UTR increased virulence, while the isaA mutant is completely attenuated in a wax moth larvae model. Sequence and structural analyses of vigR indicated that the 3' UTR has expanded through the acquisition of Staphylococcus aureus repeat insertions that contribute sequence for the isaA interaction seed and may functionalize the 3' UTR.

Exploration of agr types, virulence-associated genes, and biofilm formation ability in Staphylococcus aureus isolates from hemodialysis patients with vascular access infections.

Introduction: Staphylococcus aureus, is a pathogen commonly encountered in both community and hospital settings. Patients receiving hemodialysis treatment face an elevated risk of vascular access infections (VAIs) particularly Staphylococcus aureus, infection. This heightened risk is attributed to the characteristics of Staphylococcus aureus, , enabling it to adhere to suitable surfaces and form biofilms, thereby rendering it resistant to external interventions and complicating treatment efforts. Methods: Therefore this study utilized PCR and microtiter dish biofilm formation assay to determine the difference in the virulence genes and biofilm formation among in our study collected of 103 Staphylococcus aureus, isolates from hemodialysis patients utilizing arteriovenous grafts (AVGs), tunneled cuffed catheters (TCCs), and arteriovenous fistulas (AVFs) during November 2013 to December 2021. Results: Our findings revealed that both MRSA and MSSA isolates exhibited strong biofilm production capabilities. Additionally, we confirmed the presence of agr types and virulence genes through PCR analysis. The majority of the collected isolates were identified as agr type I. However, agr type II isolates displayed a higher average number of virulence genes, with MRSA isolates exhibiting a variety of virulence genes. Notably, combinations of biofilm-associated genes, such as eno-clfA-clfB-fib-icaA-icaD and eno-clfA-clfB-fib-fnbB-icaA-icaD, were prevalent among Staphylococcus aureus, isolates obtained from vascular access infections. Discussion: These insights contribute to a better understanding of the molecular characteristics associated with Staphylococcus aureus, infections in hemodialysis patients and provided more targeted and effective treatment approaches.

The role of Staphylococcus aureus in cystic fibrosis pathogenesis and clinico-microbiological interactions.

Cystic fibrosis (CF) is a progressive and inherited disease that affects approximately 70000 individuals all over the world annually. A mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene serves as its defining feature. Bacterial infections have a significant impact on the occurrence and development of CF. In this manuscript, we discuss the role and virulence factors of Staphylococcus aureus as an important human pathogen with the ability to induce respiratory tract infections. Recent studies have reported S. aureus as the first isolated bacteria in CF patients. Methicillin-resistant Staphylococcus aureus (MRSA) pathogens are approximately resistant to all ß-lactams. CF patients are colonized by MRSA expressing various virulence factors including toxins, and Staphylococcal Cassette Chromosome mec (SCCmec) types, and have the potential for biofilm formation. Therefore, variations in clinical outcomes will be manifested. SCCmec type II has been reported in CF patients more than in other SCCmec types from different countries. The small-colony variants (SCVs) as specific morphologic subtypes of S. aureus with slow growth and unusual properties can also contribute to persistent and difficult-to-treat infections in CF patients. The pathophysiology of SCVs is complicated and not fully understood. Patients with cystic fibrosis should be aware of the intrinsic risk factors for complex S. aureus infections, including recurring infections, physiological issues, or coinfection with P. aeruginosa.

Neobavaisoflavone Inhibits Biofilm Formation and α-Toxin Activity of Staphylococcus aureus.

Neobavaisoflavone had antimicrobial activities against Gram-positive multidrug-resistant (MDR) bacteria, but the effect of neobavaisoflavone on the virulence and biofilm formation of S. aureus has not been explored. The present study aimed to investigate the possible inhibitory effect of neobavaisoflavone on the biofilm formation and α-toxin activity of S. aureus. Neobavaisoflavone presented strong inhibitory effect on the biofilm formation and α-toxin activity of both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains at 25 µM, but did not affect the growth of S. aureus planktonic cells. Genetic mutations were identified in four coding genes, including cell wall metabolism sensor histidine kinase walK, RNA polymerase sigma factor rpoD, tetR family transcriptional regulator, and a hypothetical protein. The mutation of WalK (K570E) protein was identified and verified in all the neobavaisoflavone-induced mutant S. aureus isolates. The ASN501, LYS504, ILE544 and GLY565 of WalK protein act as hydrogen acceptors to form four hydrogen bonds with neobavaisoflavone by molecular docking analysis, and TRY505 of WalK protein contact with neobavaisoflavone to form a pi-H bond. In conclusion, neobavaisoflavone had excellent inhibitory effect on the biofilm formation and α-toxin activity of S. aureus. The WalK protein might be a potential target of neobavaisoflavone against S. aureus.

Enterotoxigenic methicillin resistant Staphylococcus aureus contamination in salted fish from Gwadar Balochistan / Contaminação de Staphylococcus aureus resistente à meticilina enterotoxigênica em peixes salgados de Gwadar Balochistan

Staphylococcus aureus is an important foodborne pathogen associated to food intoxication and other multiple infections in human being. Its presence in salted food is a serious issue due to its salt tolerance potential. A study was conducted to analyze the presence of enterotoxins producing drug resistance S. aureus in salted sea fish from Gwadar. Freshly persevered samples (n=50) of salted fish were subjected to analyze the presence of S. aureus using 16S rRNA and Nuc genes primers. The isolates were then evaluated for drug resistance and enterotoxins producing potential using specific primers for MecA (methicillin resistance gene), (SEA) staphylococcal enterotoxin A and (SEB) staphylococcal enterotoxin B genes. Total 13/50 (26%) of the samples were found positive for the presence of S. aureus, preliminary confirmed with biochemical profiling and finally with the help of target genes presence. The isolates were found showing 100% resistant to methicillin, which were molecularly confirmed by the presence of MecA gene present in genome. The isolates 5/13 (38%) were positive for SEA and 3/13 (23%) for SEB genes, whereas 2/13 (15%) were confirmed having both SEA and SEB genes in its genome. It was also confirmed that all the isolates were capable to form biofilm over the glass surfaces. It was concluded that the study confirmed the presence of enterotoxigenic methicillin resistance Staphylococcus aurous (MRSA) in salted fish product, that poses gross food safety concern. Preventive and control measures are necessary to handle this serious food safety concern.

Staphylococcus aureus é um importante patógeno de origem alimentar associado à intoxicação alimentar e outras infecções múltiplas em seres humanos. Sua presença em alimentos salgados é um problema sério devido ao seu potencial de tolerância ao sal. Um estudo foi realizado para analisar a presença de enterotoxinas produtoras de resistência a drogas S. aureus em peixes salgados do mar de Gwadar. Amostras recém-perseveradas (n = 50) de peixes salgados foram submetidas à análise da presença de S. aureus usando os primers dos genes 16S rRNA e Nuc. Os isolados foram então avaliados quanto à resistência a drogas e potencial de produção de enterotoxinas usando primers específicos para os genes MecA (gene de resistência à meticilina), (SEA) enterotoxina A estafilocócica e (SEB) enterotoxina B estafilocócica genes. Um total de 13/50 (26%) das amostras foi considerado positivas para a presença de S. aureus, confirmadas preliminarmente com perfis bioquímicos e finalmente com a ajuda da presença de genes-alvo. Os isolados foram encontrados com 100% de resistência à meticilina, os quais foram confirmados molecularmente pela presença do gene MecA no genoma. Os isolados 5/13 (38%) foram positivos para SEA e 3/13 (23%) para genes SEB, enquanto 2/13 (15%) foram confirmados tendo os genes SEA e SEB em seu genoma. Também foi verificado que todos os isolados foram capazes de formar biofilme sobre as superfícies de vidro. Concluiu-se que o estudo confirmou a presença de Staphylococcus aurous resistente à meticilina enterotoxigênica (MRSA) em produtos de peixe salgado, o que representa uma grande preocupação para a segurança alimentar. Medidas preventivas e de controle são necessárias para lidar com essa grave preocupação com a segurança alimentar.

Transparent Anti-SARS-CoV-2 and Antibacterial Silver Oxide Coatings.

Transparent antimicrobial coatings can maintain the aesthetic appeal of surfaces and the functionality of a touch-screen while adding the benefit of reducing disease transmission. We fabricated an antimicrobial coating of silver oxide particles in a silicate matrix on glass. The matrix was grown by a modified Stöber sol-gel process with vapor-phase water and ammonia. A coating on glass with 2.4 mg of Ag2O per mm2 caused a reduction of 99.3% of SARS-CoV-2 and >99.5% of Pseudomonas aeruginosa, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus compared to the uncoated glass after 1 h. We envisage that screen protectors with transparent antimicrobial coatings will find particular application to communal touch-screens, such as in supermarkets and other check-out or check-in facilities where a number of individuals utilize the same touch-screen in a short interval.

Comparative Assessment of Bacteriophage and Antibiotic Activity against Multidrug-Resistant Staphylococcus aureus Biofilms.

Problems connected with biofilm-related infections and antibiotic resistance necessitate the investigation and development of novel treatment strategies. Given their unique characteristics, one of the most promising alternatives to conventional antibiotics are bacteriophages. In the in vitro and in vivo larva model study, we demonstrate that phages vB_SauM-A, vB_SauM-C, and vB_SauM-D are effective antibiofilm agents. The exposure of biofilm to phages vB_SauM-A and vB_SauM-D led to 2-3 log reductions in the colony-forming unit number in most of the multidrug-resistant S. aureus strains. It was found that phage application reduced the formed biofilms independently of the used titer. Moreover, the study demonstrated that bacteriophages are more efficient in biofilm biomass removal and reduction in staphylococci count when compared to the antibiotics used. The scanning electron microscopy analysis results are in line with colony forming unit (CFU) counting but not entirely consistent with crystal violet (CV) staining. Additionally, phages vB_SauM-A, vB_SauM-C, and vB_SauM-D can significantly increase the survival rate and extend the survival time of Galleria mellonella larvae.

The Untargeted Phytochemical Profile of Three Meliaceae Species Related to In Vitro Cytotoxicity and Anti-Virulence Activity against MRSA Isolates.

BACKGROUND: A high mortality rate is associated with about 80% of all infections worldwide, mainly due to antimicrobial resistance. Various antimicrobial and cytotoxic activities have been proposed for Meliaceae species. This study aimed to evaluate the in vitro anti-virulence and cytotoxic effect of the leaf extracts of Aphanamixis polystachya, Toona ciliata and Melia azedarach against five MRSA strains and on three cancer cell lines, followed by biological correlation to their encompassed phytoconstituents. MATERIAL AND METHODS: We explored three plants of this family against a panel of Methicillin-resistant Staphylococcus aureus (MRSA) strains and several cancer cell lines to select the most promising candidates for further in vivo and preclinical studies. The phytochemical composition was evaluated by UHPLC-QTOF-MS untargeted profiling. Cell viability was assessed by SRB assay. Minimum Inhibitory Concentration was carried out by using the agar micro-dilution technique. Inhibition of biofilm formation and preformed biofilm disruption were assessed spectrophotomertically, according to the Sultan and Nabil method (2019). RESULTS: A total of 279 compounds were putatively annotated to include different phytochemical classes, such as flavonoids (108), limonoids/terpenoids (59), phenolic acids (49) and lower-molecular-weight phenolics (39). A. polystachya extract showed the most potent cytotoxic activity against Huh-7, DU-145 and MCF-7 cell lines (IC50 = 3, 3.5 and 13.4 µg mL-1, respectively), followed by M. azedarach, with no effect recorded for T. ciliata extract. Furthermore, both A. polystachya and M. azedarach extracts showed promising anti-virulence and antimicrobial activities, with A. polystachya being particularly active against MRSA. These two latter extracts could inhibit and disrupt the biofilm, formed by MRSA, at sub-lethal concentrations. Interestingly, the extracts inhibited hemolysin-α enzyme, thus protecting rabbit RBCs from lysis. A. polystachya extract reduced the pigmentation and catalase enzyme activity of tested pigmented strains better than M. azedarach at both tested sub-MICs. Consequently, susceptibility of the extract-treated cells to oxidant killing by 200 mM H2O2 increased, leading to faster killing of the cells within 120 min as compared to the extract-non-treated cells, likely due to the lower antioxidant-scavenging activity of cells exhibiting less staphyloxanthin production. CONCLUSION: These findings suggested that both A. polystachya and M. azedarach natural extracts are rich in bioactive compounds, mainly limonoids, phenolics and oxygenated triterpenoids, which can combat MRSA biofilm infections and could be considered as promising sources of therapeutic cytotoxic, antibiofilm and anti-virulence agents.

Secondary Amine Pendant ß-Peptide Polymers Displaying Potent Antibacterial Activity and Promising Therapeutic Potential in Treating MRSA-Induced Wound Infections and Keratitis.

Interest in developing antibacterial polymers as synthetic mimics of host defense peptides (HPDs) has accelerated in recent years to combat antibiotic-resistant bacterial infections. Positively charged moieties are critical in defining the antibacterial activity and eukaryotic toxicity of HDP mimics. Most examples have utilized primary amines or guanidines as the source of positively charged moieties, inspired by the lysine and arginine residues in HDPs. Here, we explore the impact of amine group variation (primary, secondary, or tertiary amine) on the antibacterial performance of HDP-mimicking ß-peptide polymers. Our studies show that a secondary ammonium is superior to either a primary ammonium or a tertiary ammonium as the cationic moiety in antibacterial ß-peptide polymers. The optimal polymer, a homopolymer bearing secondary amino groups, displays potent antibacterial activity and the highest selectivity (low hemolysis and cytotoxicity). The optimal polymer displays potent activity against antibiotic-resistant bacteria and high therapeutic efficacy in treating MRSA-induced wound infections and keratitis as well as low acute dermal toxicity and low corneal epithelial cytotoxicity. This work suggests that secondary amines may be broadly useful in the design of antibacterial polymers.

Anti-biofilm and anti-inflammatory effects of Lycosin-II isolated from spiders against multi-drug resistant bacteria.

Currently, multidrug-resistant bacteria are rapidly increasing worldwide because of the misuse or overuse of antibiotics. In particular, few options exist for treating infections caused by long-persisting oxacillin-resistant strains and recently proliferating carbapenem-resistant strains. Therefore, alternative treatments are urgently needed. The antimicrobial peptide (AMP) Lycosin-II is a peptide consisting of 21 amino acids isolated from the venom of the spider Lycosa singoriensis. Lycosin-II showed strong antibacterial activity and biofilm inhibition effects against gram-positive and gram-negative bacteria including oxacillin-resistant Staphylococcus aureus (S. aureus) and meropenem-resistant Pseudomonas aeruginosa (P. aeruginosa) isolated from patients. In addition, Lycosin-II was not cytotoxic against human foreskin fibroblast Hs27 or hemolytic against sheep red blood cells at the concentration of which exerted antibacterial activity. The mechanism of action of Lycosin-II involves binding to lipoteichoic acid and lipopolysaccharide of gram-positive and gram-negative bacterial membranes, respectively, to destroy the bacterial membrane. Moreover, Lycosin-II showed anti-inflammatory effects by inhibiting the expression of pro-inflammatory cytokines that are increased during bacterial infection in Hs27 cells. These results suggest that Lycosin-II can serve as a therapeutic agent against infections with multidrug-resistant strains.

Differences Between Methicillin-susceptible Versus Methicillin-resistant Staphylococcus aureus Infections in Pediatrics: Multicenter Cohort Study Conducted in Bogotá, Colombia, 2014-2018.

BACKGROUND: The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) has changed in recent years. The present article is intended to establish differences between clinical, laboratory and imaging findings and outcomes of MSSA and MRSA infections, as well as among subgroups of infection such as skin and soft tissue infection, osteoarticular, bacteremia or pneumonia in a pediatric population from Bogota, Colombia. METHODS: Retrospective cohort study using clinical records of patients under 18 years of age treated at the participating centers in Bogota, Colombia, between 2014 and 2018. The first positive S. aureus culture was studied. MSSA and MRSA were compared. The χ2 test, Fisher exact test, and Kruskal-Wallis test were calculated, and the statistical significance was presented using the difference and its 95% CI. RESULTS: Five hundred fifty-one patients were included; 211 (38%) corresponded to MRSA and 340 (62%) to MSSA for a total of 703 cultures. A significantly higher probability of having an MSSA infection than MRSA was found in patients with previous heart disease (3.3% vs. 0.5%), neurologic disease (5.9% vs. 2.5%), recent major surgeries (11% vs. 5%) or who has an implanted device (11% vs. 4%). In contrast, in severe MRSA infections (bacteremia, osteoarticular infections and pneumonia), a higher rate of complications was seen (admission to the pediatric intensive care unit, mechanical ventilation and vasoactive support), and in osteoarticular MRSA, more than 1 surgery per case was seen (89% vs. 61%). Laboratory results and mortality were similar. CONCLUSIONS: MRSA was associated with a more severe course in bacteremia, osteoarticular infections and pneumonia. Some classical risk factors associated with MRSA infections were found to be related to MSSA. In general, with the exception of skin and soft tissue infection, there was an increased risk of pediatric intensive care unit admission and mechanical and inotropic support with MRSA in a pediatric population.

Identification of structurally diverse menaquinone-binding antibiotics with in vivo activity against multidrug-resistant pathogens.

The emergence of multidrug-resistant bacteria poses a threat to global health and necessitates the development of additional in vivo active antibiotics with diverse modes of action. Directly targeting menaquinone (MK), which plays an important role in bacterial electron transport, is an appealing, yet underexplored, mode of action due to a dearth of MK-binding molecules. Here we combine sequence-based metagenomic mining with a motif search of bioinformatically predicted natural product structures to identify six biosynthetic gene clusters that we predicted encode MK-binding antibiotics (MBAs). Their predicted products (MBA1-6) were rapidly accessed using a synthetic bioinformatic natural product approach, which relies on bioinformatic structure prediction followed by chemical synthesis. Among these six structurally diverse MBAs, four make up two new MBA structural families. The most potent member of each new family (MBA3, MBA6) proved effective at treating methicillin-resistant Staphylococcus aureus infection in a murine peritonitis-sepsis model. The only conserved feature present in all MBAs is the sequence 'GXLXXXW', which we propose represents a minimum MK-binding motif. Notably, we found that a subset of MBAs were active against Mycobacterium tuberculosis both in vitro and in macrophages. Our findings suggest that naturally occurring MBAs are a structurally diverse and untapped class of mechanistically interesting, in vivo active antibiotics.