Inhibitory Effect of Non-Saccharomyces Starmerella bacillaris CC-PT4 Isolated from Grape on MRSA Growth and Biofilm

Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious pathogen with biofilm-forming and drug-resistant properties that make it difficult to eradicate. In this study, the inhibition of MRSA (ATCC 43300) by Starmerella bacillaris CC-PT4 (CGMCC No. 23573) was evaluated. The results showed that the inhibition of MRSA growth and biofilm was caused by S. bacillaris CC-PT4 cell-free supernatant (CFS). The CFS of S. bacillaris CC PT4 at different times can effectively inhibit the formation of MRSA biofilm, remove the preformed biofilm, and down-regulate the related genes that promote the formation of biofilm. Afterwards, untargeted metabolomics was performed to analyze the CFS of S. bacillaris CC-PT4. Several molecules with antibacterial and inhibitory biofilm effects from the CFS were found, one of which, 2-amino-1-phenylethanol (APE), has not been reported to have antiMRSA ability before. In this study, molecular docking analysis and in vitro experiments were used to verify the function of APE to inhibit MRSA. These results indicate that S. bacillaris CC-PT4 CFS can effectively inhibit MRSA which has potential application value in controlling MRSA.

Combinatory effects of Dipterocarpus alatus twig emulgel: Wound-restoring, antibacterial, and anti-inflammatory activities against methicillin-resistant Staphylococcus aureus-infected mouse superficial wounds

Dipterocarpus alatus has been used for the treatment of infectious skin diseases and ulcerative wounds in Thai traditional medicine. A major pathogen in human superficial skin infections is methicillin-resistant Staphylococcus aureus (MRSA). This study determined the wound healing, antibacterial, and anti-inflammatory activities of D. alatus twig emulgel against MRSA-infected mouse superficial skin wounds. Ethyl acetate-methanol crude extract of D. alatus twig was incorporated into emulgel at concentrations of 20 and 40 mg/g (D20 and D40) and its activity was compared to tetracycline emulgel (160 μg/g, Tetra). MRSA-infected superficial wounds demonstrated decreased skin barrier strength, increased transepidermal water loss (TEWL), and mast cell accumulation. Expression of toll-like receptor 2 (TLR-2), NF-κβ, TNFα, IL-1β, IL-6 and IL-10 genes were induced after MRSA infection. Daily application of 100 μL of D20 or D40 for 9 days restored skin barrier strength and TEWL while reducing mast cell and MRSA numbers compared to the non-treated group (MRSA-NT). The wounds treated with D20 and D40 were entirely healed on day 9. Expression of TLR-2 and cytokine-related genes NF-κβ, TNFα, IL-1β, IL-6 and IL-10 were normalized by treatment with either D20 or D40. Therefore, emulgel containing 20 to 40 mg/g ethyl acetate-methanol crude D. alatus twig extract is a good candidate for development as a topical formulation for MRSA-infected ulcerated wounds.

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.

MRSA compendium of epidemiology, transmission, pathophysiology, treatment, and prevention within one health framework

Staphylococcus aureus is recognized as commensal as well as opportunistic pathogen of humans and animals. Methicillin resistant strain of S. aureus (MRSA) has emerged as a major pathogen in hospitals, community and veterinary settings that compromises the public health and livestock production. MRSA basically emerged from MSSA after acquiring SCCmec element through gene transfer containing mecA gene responsible for encoding PBP-2α. This protein renders the MRSA resistant to most of the β-lactam antibiotics. Due to the continuous increasing prevalence and transmission of MRSA in hospitals, community and veterinary settings posing a major threat to public health. Furthermore, high pathogenicity of MRSA due to a number of virulence factors produced by S. aureus along with antibiotic resistance help to breach the immunity of host and responsible for causing severe infections in humans and animals. The clinical manifestations of MRSA consist of skin and soft tissues infection to bacteremia, septicemia, toxic shock, and scalded skin syndrome. Moreover, due to the increasing resistance of MRSA to number of antibiotics, there is need to approach alternatives ways to overcome economic as well as human losses. This review is going to discuss various aspects of MRSA starting from emergence, transmission, epidemiology, pathophysiology, disease patterns in hosts, novel treatment, and control strategies.

Sequence types 8, 59, and 45 methicillin resistant Staphylococcus aureus as the predominant strains causing skin and soft tissue infections in Taiwan's prisons and jails

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is the predominant cause of skin and soft tissue infections (SSTIs), which is a problem in prisons and jails. We conducted this study to understand MRSA molecular characteristics among inmates with SSTIs, and we chose MRSA isolates from a community hospital as a comparison.

METHODS

A total of 219 MRSA isolates from three custodial facilities and 134 isolates from a community hospital in Taiwan were collected in the 2017 calendar year. MRSA isolates were investigated molecularly by staphylococcal chromosome cassette mec (SCCmec) type, mupirocin, and chlorhexidine genotypical resistance, and multi-locus sequence typing (ST).

RESULTS

Of the 219 MRSA isolates from custodial facilities, SCCmec IV was the most prevalent type (65.3%), followed by type V_T (32.4%) and type V (1.8%). Regarding sequence types, ST59 (36.4%), 8 (35.3%), and 45 (17.9%) were the leading three predominant types out of 184 selected MRSA isolates, and ST45 MRSA was more prevalent in custodial facilities (p = 0.019). The antimicrobial resistance rates varied for different MRSA strains, with ST45 MRSA having the lowest rates of resistance to most antimicrobials. Overall, 91.5% of isolates carried mupA gene and 25.8% were positive for qacA/B gene, this was independent of the MRSA sequence types.

CONCLUSIONS

ST59, ST8, and ST45 MRSA are the leading three MRSA strains causing SSTIs in Taiwan, 2017, but the molecular distribution varied distinctly between the custodial facilities and hospital settings. The genotypical mupirocin resistance rate is quite high in this study. The frequency of chlorhexidine resistance gene is relatively low, especially in MRSA isolates from custodial facilities.

Nasal microbiota evolution within the congregate setting imposed by military training

The human microbiome is comprised of a complex and diverse community of organisms that is subject to dynamic changes over time. As such, cross-sectional studies of the microbiome provide a multitude of information for a specific body site at a particular time, but they fail to account for temporal changes in microbial constituents resulting from various factors. To address this shortcoming, longitudinal research studies of the human microbiome investigate the influence of various factors on the microbiome of individuals within a group or community setting. These studies are vital to address the effects of host and/or environmental factors on microbiome composition as well as the potential contribution of microbiome members during the course of an infection. The relationship between microbial constituents and disease development has been previously explored for skin and soft tissue infections (SSTIs) within congregate military trainees. Accordingly, approximately 25% of the population carries Staphylococcus aureus within their nasal cavity, and these colonized individuals are known to be at increased risk for SSTIs. To examine the evolution of the nasal microbiota of U.S. Army Infantry trainees, individuals were sampled longitudinally from their arrival at Fort Benning, Georgia, until completion of their training 90 days later. These samples were then processed to determine S. aureus colonization status and to profile the nasal microbiota using 16S rRNA gene-based methods. Microbiota stability differed dramatically among the individual trainees; some subjects exhibited great stability, some subjects showed gradual temporal changes and some subjects displayed a dramatic shift in nasal microbiota composition. Further analysis utilizing the available trainee metadata suggests that the major drivers of nasal microbiota stability may be S. aureus colonization status and geographic origin of the trainees. Nasal microbiota evolution within the congregate setting imposed by military training is a complex process that appears to be affected by numerous factors. This finding may indicate that future campaigns to prevent S. aureus colonization and future SSTIs among high-risk military trainees may require a ‘personalized’ approach.

Biofilm Formation of Multidrug-Resistant MRSA Strains Isolated from Different Types of Human Infections

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the main pathogens causing chronic infections, mainly due to its capacity to form biofilms. However, the mechanisms underlying the biofilm formation of MRSA strains from different types of human infections are not fully understood. MRSA strains isolated from distinct human infections were characterized aiming to determine their biofilm-forming capacity, the biofilm resistance to conventional antibiotics and the prevalence of biofilm-related genes, including, icaA, icaB, icaC, icaD, fnbA, fnbB, clfA, clfB, cna, eno, ebpS, fib and bbp. Eighty-three clinical MRSA strains recovered from bacteremia episodes, osteomyelitis and diabetic foot ulcers were used. The biofilm-forming capacity was evaluated by the microtiter biofilm assay and the biofilm structure was analyzed via confocal scanning laser microscopy. The antimicrobial susceptibility of 24-h-old biofilms was assessed against three antibiotics and the biomass reduction was measured. The metabolic activity of biofilms was evaluated by the XTT assay. The presence of biofilm-related genes was investigated by whole-genome sequencing and by PCR. Despite different intensities, all strains showed the capacity to form biofilms. Most strains had also a large number of biofilm-related genes. However, strains isolated from osteomyelitis showed a lower capacity to form biofilms and also a lower prevalence of biofilm-associated genes. There was a significant reduction in the biofilm biomass of some strains tested against antibiotics. Our results provide important information on the biofilm-forming capacity of clinical MRSA strains, which may be essential to understand the influence of different types of infections on biofilm production and chronic infections.

Clinical and immunologic differences in cellulitis vs. pseudocellulitis

Introduction: The immunologic mechanisms between cellulitis and pseudocellulitis differ greatly, even though their clinical presentations may overlap.Areas covered: This article discusses cellulitis and common entities within the pseudocellulitis spectrum including acute lymphedema, superficial venous thrombosis, allergic contact dermatitis, lipodermatosclerosis, stasis dermatitis, erythema nodosum, cutaneous gout, and bursitis. The literature search was conducted from PubMed search engine between March and May 2021.Expert commentary: While immunologic differences in cellulitis and the various entities of pseudocellulitis are clear, there is a practice gap in applying these differences to the clinic and hospital setting. Further, existing studies are weakened by the lack of a gold-standard diagnosis in this disease category. Additional work is necessary in developing a gold-standard for the diagnosis and secondly, to project these immunologic differences as biomarkers to differentiate sterile inflammation from a potential life threatening bacterial or fungal infection.

Systematic review and meta-analysis of the epidemiology of vancomycin-resistance Staphylococcus aureus isolates

BACKGROUND

Vancomycin‑resistant Staphylococcus aureus (VRSA) is a serious public health challenging concern worldwide.

OBJECTIVES

Therefore, the objective of present study of 62 published studies was to evaluate the prevalence of VRSA based on different years, areas, isolate source, antimicrobial susceptibility testing, and the genetic determinants.

METHODS

We searched the relevant articles that focused on the prevalence rates of VRSA in PubMed, Scopus, Embase, and Web of Science from 2000 to 2019. Statistical analyses were conducted using STATA software (version 14.0).

RESULTS

The prevalence of VRSA was 2% before 2006, 5% in 2006-2014, and 7% in 2015-2020 that showed a 3.5-fold increase in the frequency of VRSA between before 2006 and 2020 years. The prevalence of VRSA was 5% in Asia, 1% in Europe, 4% in America, 3% in South America, and 16% in Africa. The frequencies of VRSA isolated from clinical, non-clinical, and mixed samples were 6%, 7%, and 14%, respectively. The prevalence of VRSA was 12% using disk diffusion agar method, 7% using MIC-base methods, and 4% using mixed-methods. The prevalence of vanA, vanB, and vanC1 positive were 71%, 26%, and 4% among VRSA strains. The most prevalent genotype was staphylococcal cassette chromosomemec (SCCmec) II, which accounted for 57% of VRSA. The most prevalent staphylococcal protein A (spa) types were t002, t030, and t037.

CONCLUSION

The prevalence of VRSA has been increasing in recent years particularly in Africa/Asia than Europe/America. The most prevalent of genetic determinants associated with VRSA were vanA and SCCmec II. This study clarifies that the rigorous monitoring of definite antibiotic policy, regular surveillance/control of nosocomial-associated infections and intensive surveillance of vancomycin-resistance are required for preventing emergence and further spreading of VRSA.

Rhodomyrtone Accumulates in Bacterial Cell Wall and Cell Membrane and Inhibits the Synthesis of Multiple Cellular Macromolecules in Epidemic Methicillin-Resistant Staphylococcus aureus

As the burden of antibacterial resistance worsens and treatment options become narrower, rhodomyrtone—a novel natural antibiotic agent with a new antibacterial mechanism—could replace existing antibiotics for the treatment of infections caused by multi-drug resistant Gram-positive bacteria. In this study, rhodomyrtone was detected within the cell by means of an easy an inexpensive method. The antibacterial effects of rhodomyrtone were investigated on epidemic methicillin-resistant Staphylococcus aureus. Thin-layer chromatography demonstrated the entrapment and accumulation of rhodomyrtone within the bacterial cell wall and cell membrane. The incorporation of radiolabelled precursors revealed that rhodomyrtone inhibited the synthesis of macromolecules including DNA, RNA, proteins, the cell wall, and lipids. Following the treatment with rhodomyrtone at MIC (0.5–1 µg/mL), the synthesis of all macromolecules was significantly inhibited (p ≤ 0.05) after 4 h. Inhibition of macromolecule synthesis was demonstrated after 30 min at a higher concentration of rhodomyrtone (4× MIC), comparable to standard inhibitor compounds. In contrast, rhodomyrtone did not affect lipase activity in staphylococci—both epidemic methicillin-resistant S. aureus and S. aureus ATCC 29213. Interfering with the synthesis of multiple macromolecules is thought to be one of the antibacterial mechanisms of rhodomyrtone.

Antibacterial Activity of Arbutus pavarii Pamp against Methicillin-Resistant Staphylococcus aureus (MRSA) and UHPLC-MS/MS Profile of the Bioactive Fraction

Arbutus pavarii Pamp is a medicinal plant commonly used by local tribes in East Libya for the treatment of many diseases, such as gastritis, renal infections, cancer and kidney diseases. In this study, the antibacterial activity of the leaf and stem bark extracts of the plant against methicillin-resistant Staphylococcus aureus (MRSA), as well as the metabolite profiles of the bioactive fractions, was investigated. The antibacterial activity was determined by disc diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), while the microbial reduction by the bioactive fraction was evaluated using time-kill test. The bioactive fraction was further subjected to ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-ESI-MS/MS) analysis to putatively identify the chemical constituents contained therein. All the extracts and fractions showed different levels of antibacterial activity on the tested MRSA strains. The highest total antibacterial activity, i.e., 4007.6 mL/g, was exhibited by the crude leaf methanolic extract. However, the ethyl acetate fraction of the leaf showed moderate to significant antibacterial activity against MRSA at low MIC (0.08-1.25 mg/mL). Metabolite profiling of this fraction using UHPLC-ESI-MS/MS resulted in the putative identification of 28 compounds, which included phenolic acids, flavan-3-ols and flavonols. The results of this study showed that the ethyl acetate fraction of Arbutus pavarii leaf possessed potential antibacterial activity against MRSA and hence can be further explored for pharmaceutical applications as a natural antibacterial agent.

Natural brominated phenoxyphenols kill persistent and biofilm-incorporated cells of MRSA and other pathogenic bacteria

Due to a high unresponsiveness to chemotherapy, biofilm formation is an important medical problem that frequently occurs during infection with many bacterial pathogens. In this study, the marine sponge-derived natural compounds 4,6-dibromo-2-(2',4'-dibromophenoxy)phenol and 3,4,6-tribromo-2-(2',4'-dibromophenoxy)phenol were found to exhibit broad antibacterial activity against medically relevant gram-positive and gram-negative pathogens. The compounds were not only bactericidal against both replicating and stationary phase-persistent planktonic cells of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa; they also killed biofilm-incorporated cells of both species while not affecting biofilm structural integrity. Moreover, these compounds were active against carbapenemase-producing Enterobacter sp. This simultaneous activity of compounds against different growth forms of both gram-positive and gram-negative bacteria is rare. Genome sequencing of spontaneous resistant mutants and proteome analysis suggest that resistance is mediated by downregulation of the bacterial EIIBC phosphotransferase components scrA and mtlA in MRSA likely leading to a lower uptake of the molecules. Due to their only moderate cytotoxicity against human cell lines, phenoxyphenols provide an interesting new scaffold for development of antimicrobial agents with activity against planktonic cells, persisters and biofilm-incoporated cells of ESKAPE pathogens. KEY POINTS: • Brominated phenoxyphenols kill actively replicating and biofilm-incorporated bacteria. • Phosphotransferase systems mediate uptake of brominated phenoxyphenols. • Downregulation of phosphotransferase systems mediate resistance.

Wound Dressings Coated with Silver Nanoparticles and Essential Oils for The Management of Wound Infections

Infection represents one of the major risk factors in persistent and difficult to treat wounds. This study focuses on developing antimicrobial wound dressings coated with silver nanoparticles, sodium alginate and different essential oils, to avoid wound infection and biofilm formation. The design of the wound dressings was done by the dip coating method. The characteristics of the developed materials were analysed by physicochemical (FT-IR, XRD, SEM, TEM) and biological (antimicrobial tests) approaches. The results demonstrated uniform silver nanoparticle formation on the substrate, and the developed nanomodified dressings were proven to have increased antimicrobial and antibiofilm potential. The developed wound dressings based on silver nanoparticles, sodium alginate and essential oils have real potential in treating infections, and can be investigated as an efficient alternative to antibiotics and topical preparations for wound management.

In vivo imaging/detection of MRSA bacterial infections in mice using fluorescence labelled polymeric nanoparticles carrying vancomycin as the targeting agent

This study aims to develop fluorescence labelled polymeric nanoparticle (NP) carrying vancomycin as the targeting agent for in vivo imaging of Methicillin-resistant Staphylococcus aureus bacterial infections in animal models. Maleimide functionalized 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[maleimide (polyethylene glycol)-2000] as the main was carrier matrix to prepare the NPs. A fluorescence probe, namely, poly[9,9'-bis (6″-N,N,N-trimethylammonium) hexyl) fluorene-co-alt-4,7-(2,1,3-benzothiadiazole) dibromide] was encapsulated within these NPs by ultrasonication successfully. UV-Vis spectro- photometry of the NPs showed the characteristic shifting on the peak of conjugated polymers indicating successful packaging of this compound with lipid bilayers in nanoscales. Zeta-sizer and TEM analysis showed that the prepared NPs have a diameter of 80-100 nm in a narrow size distribution. Thiolated vancomycin was synthesized and attached to the NPs as the targeting agent. FTIR and MALDI-TOF spectroscopy analysis confirmed the immobilization. The specific targeting properties of the vancomycin conjugated NPs to the target bacteria were first confirmed in in vitro bacterial cultures in which Escherichia coli was the non-target bacteria - using confocal microscopy and TEM. Imaging of bacterial infections in vivo was investigated in mice model using a non-invasive live animal fluorescence imaging technique. The results confirmed that bacterial infections can be detected using these novel polymeric NPs carrying fluorescence probes for imaging and vancomycin as the targeting agent - in vivo successfully.

Genotype Distribution of Panton-Valentine Leukocidin (PVL)-Positive Staphylococcus aureus Strains Isolated from Wound-Related Infections: a Three-Year Multi-Center Study in Tehran, Iran

The spread of Panton-Valentine leucocidin (PVL)-carrying S. aureus strains in patients with wound infections in both the community and hospitals is increasing in some areas of Iran. In the present study, we determined the molecular characteristics and distribution of PVL-producing S. aureus strains isolated from wound infections. Genes encoding resistance, toxins, and staphylococcal enterotoxins were analyzed by polymerase chain reaction assays. Genotyping was performed using multi-locus sequence typing. Aminoglycoside resistance genes including ant (4')-Ia (57.4%) and aac (6')-Ie/aph (2″) (45.7%) were the most prevalent genes in isolates. Staphylococcal enterotoxin type A, as the most frequent type, was present in 20.2% of isolates. Strains belonged to seven clonal complexes. The most frequent clonal complex was CC30 (ST30) (29.8%), followed by CC22 (ST22) (21.3%), CC8 (ST8 and ST931) (17%), CC88 (ST88) (10.6%), CC59 (ST59 and ST338) (8.5%), CC1 (ST772 and ST1) (7.5%), and CC15 (ST15) (5.3%). Our findings indicated an increasing trend of CC30, carrying a wide range of resistance and toxin genes, which could present an obstacle in the treatment of patients with wound infections. Further studies are required to investigate the carriage of resistance, the antibiotic susceptibility pattern, and toxins encoding genes in different molecular types.

Risk factors associated with methicillin-resistant Staphylococcus aureus skin and soft tissue infections in hospitalized patients in Colombia

OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections (SSTIs) represent a major clinical problem in Colombia. The aim of this study was to evaluate the risk factors associated with MRSA SSTI in Colombia.

METHODS

A multicenter cohort study with nested case-control design was performed. Patients with an SSTI with at least 48h of inpatient care were included. Patients with an MRSA SSTI were considered the case group and patients with either a non-MRSA SSTI or with an Methicillin-susceptible S. aureus (MSSA) SSTI were the control groups. A multivariate logistic regression approach was used to evaluate risk factors associated with MRSA SSTI with two different statistical models.

RESULTS

A total 1134 patients were included. Cultures were positive for 498 patients, of which 52% (n=259) were Staphylococcus aureus. MRSA was confirmed in 68.3% of the S. aureus cultures. In the first model, independent risk factors for MRSA SSTI were identified as the presence of abscess (P<0.0001), cellulitis (P=0.0007), age 18-44 years (P=0.001), and previous outpatient treatment in the previous index visit (P=0.003); surgical site infection was a protective factor (P=0.008). In the second model, the main risk factor found was previous outpatient treatment in the previous index visit (P=0.013).

CONCLUSIONS

Community-acquired SSTIs in Colombia are commonly caused by MRSA. Therefore, clinicians should consider MRSA when designing the initial empirical treatment for purulent SSTI in Colombia, although there seems to be low awareness of this fact.

Methicillin-resistant Staphylococcus aureus skin and soft tissue infections in young people in custody in New South Wales

AIM

Methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections (SSTIs) are problematic for incarcerated adolescents but have not been previously researched.

METHODS

This was a 2-year prospective study of all New South Wales Juvenile Custodial Centres involving incarcerated youth aged 12-20 years. The main outcomes measured were MRSA SSTIs, MRSA molecular subtypes and associations with MRSA infection. Variables included age, gender, SSTI site and type, Indigenous status, incarceration time, lifetime incarcerations, intravenous drug use, overweight/obesity, recent antibiotic use and health centre presentations.

RESULTS

From February 2013 to January 2015, there were 77 SSTIs (92.2% male, 59.2% Indigenous, mean age 16.9 years). The majority (77.9%) were collections, mostly on the lower limb (44.2%), and 33 (42.9%) isolates were MRSA; 94% were Panton-Valentine leukocidin positive. This represents 11 SSTIs per 1000 custodial admissions, and 4.7 MRSA SSTIs per 1000 custodial admissions. Independent associations with MRSA SSTI (vs. non-MRSA SSTI) were Indigenous status (adjusted odds ratio (AOR) 5.92, P < 0.001), presenting with a collection (AOR 18.29, P < 0.001) and recent antibiotic use (AOR 3.62, P < 0.05).

CONCLUSIONS

Incarcerated Australian youth have high rates of MRSA SSTIs, comparable to rates in US adult inmates, but with different molecular subtypes. At particular risk of MRSA infection are Indigenous youth, those with recent antibiotic use and those presenting with a collection. Many MRSA infections present at custodial admission, making surveillance and containment important, along with avoidance of unnecessary antibiotics and hand hygiene. Panton-Valentine leukocidin-positive MRSA predominates and is known for causing flu-associated necrotising pneumonia. Albeit a rare outcome, the seasonal influenza vaccination should be mandatory for youth in custody and custodial staff.

5-Arylideneimidazolones with Amine at Position 3 as Potential Antibiotic Adjuvants against Multidrug Resistant Bacteria

Searching for new chemosensitizers of bacterial multidrug resistance (MDR), chemical modifications of (Z)-5-(4-chlorobenzylidene)-2-(4-methylpiperazin-1-yl)-3H-imidazol-4(5H)-one (6) were performed. New compounds (7⁻17), with fused aromatic rings at position 5, were designed and synthesized. Crystallographic X-ray analysis proved that the final compounds (7⁻17) were substituted with tertiary amine-propyl moiety at position 3 and primary amine group at 2 due to intramolecular Dimroth rearrangement. New compounds were evaluated on their antibiotic adjuvant properties in either Gram-positive or Gram-negative bacteria. Efflux pump inhibitor (EPI) properties towards the AcrAB-TolC pump in Enterobacter aerogenes (EA289) were investigated in the real-time efflux (RTE) assay. Docking and molecular dynamics were applied to estimate an interaction of compounds 6⁻17 with penicillin binding protein (PBP2a). In vitro ADME-Tox properties were evaluated for compound 9. Most of the tested compounds reduced significantly (4-32-fold) oxacillin MIC in highly resistant MRSA HEMSA 5 strain. The anthracene-morpholine derivative (16) was the most potent (32-fold reduction). The tested compounds displayed significant EPI properties during RTE assay (37⁻97%). The naphthyl-methylpiperazine derivative 9 showed the most potent "dual action" of both oxacillin adjuvant (MRSA) and EPI (E. aerogenes). Molecular modeling results suggested the allosteric mechanism of action of the imidazolones, which improved binding of oxacillin in the PBP2a active site in MRSA.