Neonatal methicillin-resistant Staphylococcus aureus pneumonia-related recurrent fatal pyopneumothorax: A case report and review of literature

BACKGROUND Although neonatal Staphylococcus aureus pneumonia is common and usually curable,it can also be refractory and life-threatening.Herein,we report a case of severe neonatal community-acquired methicillin-resistant Staphylococcus aureus(CA-MRSA)necrotizing pneumonia with bilateral recurrent pyopneumothorax,respiratory failure,heart failure,and cardiac arrest.We hope our report will add to the understanding of this disease.CASE SUMMARY An 18-d-old boy presented with cough for five days,fever for three days,and dyspnea for two days.Preadmission chest radiograph revealed high-density shadows in both lungs.On admission,his oxygen saturation fluctuated around 90%under synchronized intermittent mandatory ventilation.He was unconscious,with dyspnea,weak heart sounds and hepatomegaly.Moist crackles were present throughout his left lung,while the breath sounds in the right lung were decreased.After high-frequency oscillatory ventilation,empiric antimicrobials(meropenem and vancomycin),improved circulation,and right pleural cavity drainage for right pneumothorax(approximately 90%compression),his oxygen saturation level stayed above 95%,and recruitment of the right lung was observed.His condition did not deteriorate until the 5th day of hospitalization(DOH 5).On the morning of DOH 5,his oxygen saturation decreased.Subsequent chest radiograph showed bilateral pneumothorax with nearly 100%compression of the left lung.Desaturation was not relieved after urgent left pleural cavity drainage,and cardiac arrest occurred soon thereafter.Although his spontaneous heartbeat returned through emergency resuscitation and salvage antibacterial therapy(linezolid and levofloxacin)was administered given the detection and antimicrobial susceptibility of MRSA,he showed no improvement,with recurrent pyopneumothorax and continued drainage of purulent fluid and necrotic lung tissue fragments from the pleural cavity.Eventually,his parents refused extracorporeal membrane oxygenation(ECMO)and gave up all the treatments,and the newborn passed away soon after withdrawal on DOH 13.CONCLUSION Neonatal MRSA pneumonia can be refractory and lethal,especially in cases where necrotizing pneumonia leads to extensive lung necrosis and recurrent pneumothorax.Despite treatment with linezolid and other medical measures,it may still be ineffective.Currently,ECMO has been a remedial therapy,but if the lung tissue is too severely eroded to be repaired,it may be useless unless the infection can be controlled and lung transplantation can be performed.Regardless of whether ECMO is initiated,the key to successful treatment is to achieve control over the pneumonia caused by MRSA as soon as possible and to reverse lung injury as much as possible.

甘草提取物对Staphylococcus aureus的抑菌活性及作用机理

食源性病菌为食品安全带来了巨大挑战,甘草提取物作为食品添加剂对金黄色葡萄球菌(Staphylococcus aureus)具有良好的抑菌作用,可作为天然食品防腐剂的候选原料,但目前对其抑菌机理的研究还不深入,影响了其应用。为探究甘草提取物对S.aureus的抑菌机理,该研究通过生长曲线、氧化损伤实验、细胞膜壁分析、蛋白质分析和DNA分析,评价了甘草提取物对S.aureus的抑菌作用机制。结果表明,甘草提取物导致S.aureus核酸渗漏,说明其膜完整性被破坏;同时,甘草提取物降低了几种能量代谢酶:琥珀酸脱氢酶(succinate dehydrogenase,SDH)和总ATP酶的活力;此外,光谱和竞争分析表明,甘草提取物与DNA发生了静电结合和凹槽结合。总之,甘草提取物主要是通过对S.aureus细胞壁膜、蛋白质合成、细菌代谢活力和遗传物质发挥作用,从而抑制其生长。该研究为甘草提取物在食品防腐方面的应用提供了理论基础。

Elimination of methicillin‑resistant Staphylococcus aureus biofilms on titanium implants via photothermally‑triggered nitric oxide and immunotherapy for enhanced osseointegration

Background:Treatment of methicillin-resistant Staphylococcus aureus(MRSA)biofilm infections in implant placement surgery is limited by the lack of antimicrobial activity of titanium(Ti)implants.There is a need to explore more effective approaches for the treatment of MRSA biofilm infections.Methods:Herein,an interfacial functionalization strategy is proposed by the integration of mesoporous polydopamine nanoparticles(PDA),nitric oxide(NO)release donor sodium nitroprusside(SNP)and osteogenic growth peptide(OGP)onto Ti implants,denoted as Ti-PDA@SNP-OGP.The physical and chemical properties of Ti-PDA@SNP-OGP were assessed by scanning electron microscopy,X-ray photoelectron spectroscope,water contact angle,photothermal property and NO release behavior.The synergistic antibacterial effect and elimination of the MRSA biofilms were evaluated by 2′,7′-dichlorofluorescein diacetate probe,1-N-phenylnaphthylamine assay,adenosine triphosphate intensity,O-nitrophenyl-β-D-galactopyranoside hydrolysis activity,bicinchoninic acid leakage.Fluorescence staining,assays for alkaline phosphatase activity,collagen secretion and extracellular matrix mineralization,quantitative real‑time reverse transcription‑polymerase chain reaction,and enzyme-linked immunosorbent assay(ELISA)were used to evaluate the inflammatory response and osteogenic ability in bone marrow stromal cells(MSCs),RAW264.7 cells and their co-culture system.Giemsa staining,ELISA,micro-CT,hematoxylin and eosin,Masson's trichrome and immunohistochemistry staining were used to evaluate the eradication of MRSA biofilms,inhibition of inflammatory response,and promotion of osseointegration of Ti-PDA@SNP-OGP in vivo.Results:Ti-PDA@SNP-OGP displayed a synergistic photothermal and NO-dependent antibacterial effect against MRSA following near-infrared light(NIR)irradiation,and effectively eliminated the formed MRSA biofilms by inducing reactive oxygen species(ROS)-mediated oxidative stress,destroying bacterial membrane integrity and causing leakage of intracellular components(P<0.01).In vitro experiments revealed that Ti-PDA@SNP-OGP not only facilitated osteogenic differentiation of MSCs,but also promoted the polarization of pro-inflammatory M1 macrophages to the anti-inflammatory M2-phenotype(P<0.05 or P<0.01).The favorable osteo-immune microenvironment further facilitated osteogenesis of MSCs and the anti-inflammation of RAW264.7 cells via multiple paracrine signaling pathways(P<0.01).In vivo evaluation confirmed the aforementioned results and revealed that Ti-PDA@SNP-OGP induced ameliorative osseointegration in an MRSA-infected femoral defect implantation model(P<0.01).Conclusions:Ti-PDA@SNP-OGP is a promising multi-functional material for the high-efficient treatment of MRSA infections in implant replacement surgeries.

Structural insights on anti-biofilm mechanism of heated slightly acidic electrolyzed water technology against multi-resistant Staphylococcus aureus biofilm on food contact surface

Slightly acidic electrolyzed water(SAEW)has proven to be an efficient and novel sanitizer in food and agriculture field.This study assessed the efficacy of SAEW(30 mg/L)at 40℃on the inactivation of foodbome pathogens and detachment of multi-resistant Staphylococcus aureus(MRSA)biofilm.Furthermore.the underlying mechanism of MRS A biofilm under heated SAEW at 40℃treatment on metabolic profiles was investigated.The results showed that the heated SAEW at 40℃significantly effectively against foodbome pathogens of 1.96-7.56(lg(CFU/g))reduction in pork,chicken,spinach,and lettuce.The heated SAEW at 40℃treatment significantly reduced MRS A biofilm cells by 2.41(lg(CFU/cm^(2))).The synergistic effect of SAEW treatment showed intense anti-biofilm activity in decreasing cell density and impairing biofilm cell membranes.Global metabolic response of MRSA biofilms,treated by SAEW at 40℃,revealed the alterations of intracellular metabolites,including amino acids,organic acid,fatty acid,and lipid.Moreover,signaling pathways involved in amino acid metabolism,energy metabolism,nucleotide synthesis,carbohydrate metabolites,and lipid biosynthesis were functionally disrupted by the SAEW at 40℃treatment.As per our knowledge,this is the first research to uncover the potential mechanism of heated SAEW treatment against MRSA biofilm on food contact surface.

Eugenol targeting CrtM inhibits the biosynthesis of staphyloxanthin in Staphylococcus aureus

Staphylococcus aureus is a serious foodborne pathogen threatening food safety and public health.Especially the emergence of methicillin-resistant Staphylococcus aureus(MRSA)increased the difficulty of S.aureus treatment.Staphyloxanthin is a crucial virulence factor of S.aureus.Blocking staphyloxanthin production could help the host immune system counteract the invading S.aureus cells.In this study,we first screened for staphyloxanthin inhibitors using a virtual screening method.The outcome of the virtual screening method resulted in the identification of eugenol(300μg/mL),which significantly inhibits the staphyloxanthin production in S.aureus ATCC 29213,S.aureus Newman,MRSA ATCC 43300 and MRSA ATCC BAA1717by 84.2%,63.5%,68.1%,and 79.5%,respectively.The outcome of the growth curve assay,field-emission scanning electron,and confocal laser scanning microscopy analyses confirmed that eugenol at the test concentration did not affect the morphology and growth of S.aureus.Moreover,the survival rate of S.aureus ATCC 29213 and MRSA ATCC 43300 under H_(2)O_(2) pressure decreased to 51.9%and 45.5%in the presence of eugenol,respectively.The quantitative RT-PCR and molecular simulation studies revealed that eugenol targets staphyloxanthin biosynthesis by downregulating the transcription of the crtM gene and inhibiting the activity of the CrtM enzyme.Taken together,we first determined that eugenol was a prominent compound for staphyloxanthin inhibitor to combat S.aureus especially MRSA infections.

Electrochemical and colorimetric dual-signal detection of Staphylococcus aureus enterotoxin B based on AuPt bimetallic nanoparticles loaded Fe-N-C single atom nanocomposite

Sensitive detection of Staphylococcus aureus enterotoxin B(SEB)is of importance for preventing food poisoning from threatening human health.In this work,an electrochemical and colorimetric dual-signal detection assay of SEB was developed.The probe(Ab2/AuPt@Fe-N-C)was bound to SEB captured by Ab1,where the Ab2/AuPt@Fe-N-C triggered methylene blue degradation and resulted in the decrease of electrochemical signal.Furthermore,the probe catalyzed the oxidation of 3,3’,5,5’-tetramethyl biphenyl to generate a colorimetric absorbance at 652 nm.Once the target was captured and formed a sandwich-like complex,the color changed from colorless to blue.SEB detection by colorimetric and electrochemical methods showed a linear relationship in the concentration ranges of 0.0002-10.0000 and 0.0005-10.0000 ng/mL,with limits of detection of 0.0667 and 0.1670 pg/mL,respectively.The dual-signal biosensor was successfully used to detect SEB in milk and water samples,which has great potential in toxin detection in food and the environment.

Genotypic Characterization of Methicillin-resistant Staphylococcus aureus Isolated from Pigs and Retail Foods in China

Objective To investigate the genotypic diversity of Methicillin-resistant Staphylococcus aureus （MRSA） isolated from pigs and retail foods from different geographical areas in China and further to study the routes and rates of transmission of this pathogen from animals to food. Methods Seventy-one MRSA isolates were obtained from pigs and retail foods and then characterized by multi-locus sequencing typing （MLST）, spa typing, multiple-locus variable number of tandem repeat analysis （MLVA）, pulsed-field gel electrophoresis （PFGE）, and antimicrobial susceptibility testing. Results All isolated MRSA exhibited multi-drug resistance （MDR）. Greater diversity was found in food-associated MRSA （7 STs, 8 spa types, and 10 MLVA patterns） compared to pig-associated MRSA （3 STs, 1 spa type, and 6 MLVA patterns）. PFGE patterns were more diverse for pig-associated MRSA than those of food-associated isolates （40 vs. 11 pulse types）. Among the pig-associated isolates, CC9-ST9-t899-MC2236 was the most prevalent clone （96.4%）, and CC9-ST9-t437-MC621 （20.0%） was the predominant clone among the food-associated isolates. The CC9-ST9 isolates showed significantly higher antimicrobial resistance than other clones. Interestingly, CC398-ST398-t034 clone was identified from both pig- and food-associated isolates. Of note, some community- and hospital-associated MRSA strains （t030, t172, t1244, and t4549） were also identified as food-associated isolates. Conclusion CC9-ST9-t899-MC2236-MDR was the most predominant clone in pigs, but significant genetic diversity was observed in food-associated MRSA. Our results demonstrate the great need for improved surveillance of MRSA in livestock and food and effective prevention strategies to limit MDR-MRSA infections in China.

Teicoplanin combined with conventional vancomycin therapy for the treatment of pulmonary methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis infections

BACKGROUND Vancomycin and teicoplanin are both antibiotics that have significant antimicrobial effects on Gram-positive cocci.AIM To explore the value of teicoplanin combined with conventional(vancomycin only)anti-infective therapy for the treatment of methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis pulmonary infections.METHODS A total of 86 patients with methicillin-resistant Staphylococcus aureus or methicillin-resistant Staphylococcus epidermidis pulmonary infections,treated in our hospital between January 2018 and February 2020,were assigned to the study and control groups using a random number table method,with 43 patients in each group.The control group received conventional treatment(vancomycin),and the study group received both teicoplanin and conventional treatment.The following indicators were assessed in both groups:the time required for symptom relief,treatment effectiveness,serum levels of inflammatory factors(procalcitonin,interleukin-1β,tumor necrosis factor-α,C-reactive protein),clinical pulmonary infection scores before and after treatment,and the incidence of adverse reactions.RESULTS Patients in the study group were observed to have faster cough and expectoration resolution,white blood cell count normalization,body temperature normalization,and rales disappearance than patients in the control group(all P<0.05);the total rate of effectiveness was 93.02%in the study group,higher than the 76.74%in the control group(P<0.05).The pre-treatment serum levels of procalcitonin,interleukin-1β,tumor necrosis factor-α,and C-reactive protein as well as the clinical pulmonary infection scores were similar among the patients in both groups.However,the post-treatment serum levels of procalcitonin,interleukin-1β,tumor necrosis factor-α,and C-reactive protein as well as the clinical pulmonary infection scores were significantly lower in the study group than in the control group(P<0.05).There was no significant difference in the incidence of adverse reactions between the groups.CONCLUSION Compared with conventional(vancomycin only)therapy,teicoplanin and vancomycin combination therapy for patients with pulmonary methicillinresistant Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis infections can improve patient clinical symptoms,modulate serum inflammatory factor levels,and improve treatment efficacy,without increasing the risk of adverse reactions.

Potentiating activity of luteolin on membrane permeabilizing agent and ATPase inhibitor against methicillin-resistant Staphylococcus aureus

Objective:To investigate the mechanism of antibacterial activity of luteoiin(LUT) against methicillin-resistant Staphylococcus aureus(MRSA).Methods:The mechanism of anti-MRSA activity of LUT was analyzed by the viability assay in membrane permeabilizing agent ATPase inhibitors,and peptidoglycan(PGN) derived from Staphylococcus aureus(S.aureus).Also,transmission electron microscopy was used to monitor survival characteristics and changes in S.aureus morphology.Results:Compared to the LUT alone,the optical density of suspensions treated with the combination of 125 μg/mL Tris and 230 μg/mL DCCD were reduced to 60%and 46%,respectively.PGN(15.6 μg/mL) gradually impeded the activity of LUT,and PGN(62.5 μg/mL) completely blocked the activity of LUT on S.aureus.Conclusions:Increased susceptibility to LUT with me Tris and DCCD combinations is evident in all tested MRSA isolates.The results indicate LUT synergy in increasing cytoplasmic membrane permeability and inhibiting ATPase.S.aureus PGN directly blocks the antibacterial activity of LUT,suggesting the direct binding of LUT with PGN.These findings may be validated for the development of antibacterial agent for low MRSA resistance.

Postoperation of preauricular fistula cellulitis caused by methicillin-resistant staphylococcus aureus infection

A one-year-old baby girl with one-month history of recurrent pus fluid exuding from her left preauricular sinus orifice, who failed multiple courses of surgical drainage of the abscess and persistent debridement for the wound, presented with MRSA infection. The patient was treated with linezolid for three days. Her pain and paresthesia resolved, and C-reactive protein decreased to normal.

Surface-engineered liposomes for dual-drug delivery targeting strategy against methicillin-resistant Staphylococcus aureus(MRSA)

This study focused on the encapsulation of vancomycin(VAN) into liposomes coated with a red blood cell membrane with a targeting ligand, daptomycin–polyethylene glycol–1,2-distearoyl-sn-glycero-3-phosphoethanolamine, formed by conjugation of DAPT and Nhydroxysuccinimidyl-polyethylene glycol-1,2-distearoyl-sn-glycero-3-phosphoethanolamine.This formulation is capable of providing controlled and targeted drug delivery to the bacterial cytoplasm. We performed MALDI-TOF, NMR and FTIR analyses to confirm the conjugation of the targeting ligand via the formation of amide bonds. Approximately 45% of VAN could be loaded into the aqueous cores, whereas 90% DAPT was detected using UV–vis spectrophotometry. In comparison to free drugs, the formulations controlled the release of drugs for > 72 h. Additionally, as demonstrated using CLSM and flow cytometry, the resulting formulation was capable of evading detection by macrophage cells. In comparison to free drugs, red blood cell membrane–DAPT–VAN liposomes, DAPT liposomes, and VAN liposomes reduced the MIC and significantly increased bacterial permeability, resulting in > 80% bacterial death within 4 h. Cytotoxicity tests were performed in vitro and in vivo on mammalian cells,in addition to hemolytic activity tests in human erythrocytes, wherein drugs loaded into the liposomes and RBCDVL exhibited low toxicity. Thus, the findings of this study provide insight about a dual antibiotic targeting strategy that utilizes liposomes and red blood cell membranes to deliver targeted drugs against MRSA.

Antimicrobial activity and synergism of Sami-Hyanglyun-Hwan with ciprofloxacin against methicillin-resistant Staphylococcus aureus

Objective: To investigate the antibacterial activity of SHHextracted with either water or ethanol against methicillin-resistant Staphylococcus aureus(MRSA) and combinatory antimicrobial effect with ciprofloxacin(CIP) by time kill assay and checkerboard dilution test. Methods: The antibacterial activity determined by broth dilution method indicated that the antibacterial activity of Sami-Hyanglyun-Hwan(SHH) water extract(SHHW) and SHH ethanol extract(SHHE) ranged from 250 to 2000 μg/m L and 125 to 1000 μg/m L against MRSA, respectively. Results: In the checkerboard method, the combinations of SHHE with CIP had a partial synergistic or synergistic effect against MRSA. The time-kill curves showed that a combined SHHE and CIP treatment reduced the bacterial counts dramatically after 24 h. Conclusions: The present study demonstrates the therapeutic ability of SHHE against MRSA infections.

Epidemiology,surveillance and control of methicillin-resistant Staphylococcus aureus:an Overview

Staphylococcus aureus(S.aureus) is one of the most common human pathogens,causing a wide range of afflictions from minor infections of the skin to serious wound infections,bacteraemia,pneumonia and endocarditis. Methicillin,the first semisynthetic derivative of penicillin,was a new hope to treat penicillin resistant 5.aureus in the early 1960s.Nevertheless,only one year after its introduction,the first methicillin-resistant 5.aureus (MRSA) strains were detected.There is no golden rule in the control of MRSA.Nevertheless,using surveillance cultures of patients and healthcare personnel,strictly enforced contact precautions,and judicious use of broad-spectrum antibiotics have helped several countries,including Finland,Denmark,and the Netherlands to keep MRSA at a very low level.Conversely,countries including China,Japan,US,Italy,Greece,UK, where stringent counter-measure were not able to be installed,MRSA have become hyper-endemic.Control of MRSA in those countries were obliged to concentrate available resources to prevent MRSA infections only at patients at high risk of serious morbidity and mortality.

Potentiating activity of rhein in targeting of resistance genes in methicillin-resistant Staphylococcus aureus

Objective: To investigate the synergistic effect between rhein(RHE) and oxacillin against Staphylococcus aureus(MRSA) at the gene level. Method: A minimum inhibitory concentration and checkerboard dilution test were conducted to evaluate antibacterial activity. Reverse transcriptase polymerase chain reaction was conducted to investigate the gene expressions. Results: RHE exhibited a minimum inhibitory concentration of 62.5-250.0 μg/mL against various MRSA strains and the reference strain, respectively. As revealed by the checkerboard assay, a combination of RHE and oxacillin exhibited synergistic or partially synergistic effects against MRSA strains. RHE decreased the expressions of mecA/blaZ in a dose-dependent manner. RHE also decreased the expressions of the regulator genes mecI/blaI and mecR1/blaR1. Conclusions: We suggest that RHE affects the activity of mecR1/blaR1, which is located in the cell membrane of MRSA and results in the suppression of mecA/mecI/mecR1 and blaZ/blaI/blaR1 gene expressions.

The prevalence of methicillin-resistant Staphylococcus aureus colonization in emergency department fast track patients

BACKGROUND:Over the past two decades,methicillin-resistant Staphylococcus aureus(MRSA) has evolved from a hospital-associated infection to a significant public health threat in the community,causing outbreaks of soft tissue infections in otherwise healthy individuals.The goal of this study was to determine the prevalence of nasal MRSA colonization in low acuity Emergency Department(ED) Fast Track patients in order to better characterize the epidemiology of this pathogen.METHODS:We conducted a cross-sectional study of a convenience sample of adult patients from our ED Fast Track.Nasal swabs were analyzed for MRSA using a polymerase chain reaction assay.Study participants completed a survey assessing traditional risk factors for CA-MRSA colonization.RESULTS:A total of 106 ED Fast Track patients were tested.Four(3.8%,95%CI 1.5%-9.3%)were MRSA positive.Three traditional CA-MRSA risk factors(personal history of abscess,family history of abscess,and participation in contact sports) were examined.In patients with a positive MRSA nasal swab,only a personal prior history of abscess retained significance(OR 33,95%C11.7-676,P=0.02).CONCLUSION:This study found a higher prevalence of nasal MRSA colonization in low acuity ED Fast Track patients compared with historical community surveillance studies.A personal history of prior abscess was a significant risk for CA-MRSA carriage.

Treatment of methicillin-resistant Staphylococcus aureus infections:Importance of high vancomycin minumum inhibitory concentrations

Staphylococcus aureus(SA) infections remain a major cause of morbidity and mortality despite the availability of numerous effective anti-staphylococcal antibiotics.This organism is responsible for both nosocomial and community-acquired infections ranging from relatively minor skin and soft tissue infections to life-threateningsystemic infections.The increasing incidence of methicillin-resistant strains has granted an increasing use of vancomycin causing a covert progressive increase of its minimum inhibitory concentration(MIC)(dubbed the MIC "creep").In this way,the emergence of vancomycinintermediate SA(VISA) strains and heteroresistantVISA has raised concern for the scarcity of alternative treatment options.Equally alarming,though fortunately less frequent,is the emergence of vancomycin-resistant SA.These strains show different mechanisms of resistance but have similar problems in terms of therapeutic approach.Ultimately,various debate issues have arisen regarding the emergence of SA strains with a minimum inhibitory concentration sitting on the superior limit of the sensitivity range(i.e.,MIC = 2 μg/mL).These strains have shown certain resilience to vancomycin and a different clinical behaviour regardless of vancomycin use,both in methicillin-resistant SA and in methicillin-sensitive SA.The aim of this text is to revise the clinical impact and consequences of the emergence of reduced vancomycin susceptibility SA strains,and the different optimal treatment options known.

Synergistic Effect between Fucoidan and Antibiotics against Clinic Methicillin-Resistant <i>Staphylococcus aureus</i>

Fucoidan is a sulfated polysaccharide that is primarily extracted from brown seaweeds which has been broadly studied in recent years due to its numerous biological properties, including anticoagulant, antithrombotic, antitumor, and antiviral activities. In this study, fucoidan was evaluated against clinic isolated methicillin-resistant Staphylococcus aureus (MRSA) 1 - 20, either alone or with antibiotics, via broth dilution method and checkerboard and time kill assay. Minimum inhibitory concentrations (MICs)/Minimum bactericidal concentrations (MBCs) values for the fucoidan against all the tested bacteria ranged between 64 - 512/256 - 2048 microg/mL, for ampicillin 32 - 1024/64 - 1024 microg/mL and for oxacillin 8 - 64/16 - 256 microg/mL respectively. Furthermore, the MIC and MBC were reduced to one half-eighth as a result of the combination of the fucoidan with antibiotics. 2 - 6 hours of treatment with 1/2 MIC of fucoidan with 1/2 MIC of antibiotics resulted from an increase of the rate of killing in units of CFU/mL to a greater degree than was observed with alone. These results suggest that fucoidan could be employed as a natural antibacterial agent against multi-drug bacteria.

The Prevalence of Methicillin-Resistant Staphylococcus aureus Colonization in Patients with Complicated Skin and Skin Structure Infections after Treatment with Linezolid or Vancomycin

Background: Complicated skin and skin structure infections (cSSSIs) due to Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), are associated with significant morbidity. Re-ducing MRSA carriage has been a focus of infection control interventions. The prevalence of MRSA colonization after successful treatment of a MRSA cSSSI is unknown. Methods: Secondary analysis of a randomized controlled trial comparing linezolid and vancomycin for the treatment of MRSA cSSSI. Adult patients that had a colonization culture, confirmed MRSA cSSSI, received at least one dose of study treatment, and had an outcome recorded at end of study. Patient, clinical characteristics and prevalence of colonization were compared by treatment regimens. A multivariate regression model identified predictors of MRSA colonization at EOS. Results: There were 456 patients evaluated. The prevalence of MRSA colonization was higher for vancomycin treated patients compared to linezolid treated patients at end of treatment (EOT) (28% vs. 5%, p < 0.001) and EOS (34% vs. 22%, p < 0.01). Independent predictors of colonization at EOS after treatment for a MRSA cSSSI included diagnosis, primarily driven by abscess, black race, treatment with vancomycin, MRSA mixed infection and male gender. Conclusion: Patients treated with linezolid for a cSSSI had less MRSA colonization at EOT and EOS compared to those treated with vancomycin. Multiple independent predictors of MRSA colonization were identified. Additional studies evaluating the relationship of MRSA colonization after treatment of cSSSI are needed.

Inhibition mechanisms of secretome proteins from Paenibacillus polymyxa Kp10 and Lactococcus lactis Gh1 against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus

Objective:To determine the inhibition mechanisms of secretome protein extracted from Paenibacillus polymyxa Kp10(Kp10)and Lactococcus lactis Gh1(Gh1)against methicillin-resistant Staphylococcus aureus(MRSA)and vancomycin-resistant Enterococcus(VRE).Methods:The sensitivity and viability of MRSA and VRE treated with secretome proteins of Kp10 and Gh1 were determined using minimal inhibitory concentration,minimum bactericidal concentration,and time-to-kill assays.The morphological changes were observed using scanning electron microscopy and transmission electron microscopy.To elucidate the antimicrobial mechanism of secretome protein of Kp10 and Gh1 against MRSA and VRE,2D gel proteomic analysis using liquid chromatography-mass spectrometry was run by comparing upregulated and downregulated proteins,and the proton motive force study including the efflux of ATP,pH gradient,and the membrane potential study were conducted.Results:MRSA and VRE were sensitive to Kp10 and Gh1 secretome protein extracts and displayed apparent morphological and internal composition changes.Several proteins associated with cellular component functions were either downregulated or upregulated in treated MRSA and VRE by changing the membrane potential gradient.Conclusions:Kp10 and Gh1 secretome proteins reduce the growth of VRE and MRSA by damaging the cell membrane.Cell division,cell wall biosynthesis,and protein synthesis are involved in the inhibition mechanism.

Screening agars for MRSA:evaluation of a stepwise diagnostic approach with two different selective agars for the screening for methicillin-resistant Staphylococcus aureus(MRSA)

Background: Colonization with methicillin-resistant Staphylococcus aureus(MRSA) poses a hygiene risk that does not spare field hospitals or military medical field camps during military deployments. Diagnostic options for unambiguously identifying MRSA isolates are usually scarce in military environments. In this study, we assessed the stepwise application of two different selective agars for the specific identification of MRSA in screening analyses.Methods: Nasal swabs from 1,541 volunteers were subjected to thioglycollate broth enrichment and subsequently screened on CHROMagar MRSA selective agar for the identification of MRSA. The MRSA identity of suspiciouslooking colonies was confirmed afterwards or excluded by another selective agar, chrom ID MRSA. All isolates from the selective agars with MRSA-specific colony morphology were identified by biochemical methods and mass spectrometry.Results: The initial CHROMagar MRSA screening identified suspicious colonies in 36 out of 1541 samples. A total of 25 of these 36 isolates showed MRSA-like growth on chrom ID agar. Out of these 25 isolates, 24 were confirmed as MRSA, while one isolate was identified as Staphylococcus kloosii. From the 11 strains that did not show suspicious growth on chrom ID agar, 3 were methicillin-sensitive Staphylococcus aureus(MSSA, with one instance of cocolonization with Corynebacterium spp.), 2 were confirmed as MRSA(with 1 instance of co-colonization with MSSA), 2 were lost during passaging and could not be re-cultured, one could not be identified by the applied approaches, and the remaining 3 strains were identified as Staphylococcus saprophyticus, Staphylococcus hominis(co-colonized with Macrococcus caseolyticus) and Staphylococcus cohnii, respectively.Conclusion: The application of the selective agar CHROMagar MRSA alone proved to be too non-specific to allow for a reliable diagnosis of the presence of MRSA. The combined use of two selective agars in a stepwise approach reduced this non-specificity with an acceptably low loss of sensitivity. Accordingly, such a stepwise screening approach might be an option for resource-restricted military medical field camps.