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Objective: To evaluate the effect of meticillin-resistant Staphylococcus aureus(MRSA)on the pyroptosis of bone-marrow derived macrophages(BMDM)and investigate the mechanism of MRSA-induced pyroptosis in macrophages. Methods: The BMDM were triggered by the combination of lipopolysaccharide(LPS, 100 ng/ml)with adenosine-triphosphate(ATP, 3 mmol/L)or nigericin(Ng, 10 mmol/L)or treated with MRSA(multiplicity of infection 200, MOI 200)alone to induce pyroptosis in vitro. The cell morphology examination and lactate dehydrogenase(LDH)assay were applied to evaluate the cytotoxicity. The expression of pro- inflammatory cytokines, the interleukin(IL)- 1β, IL- 6 and tumor-necrosis factor(TNF)-α was detected by ELISA. The cleaved caspase-1 and mature IL-1β in the cells and released into the supernatant were detected by Western blotting. The signal pathway for the induction of pyroptosis by MRSA was investigated via the transfection of lentivirus- mediated short- hairpin RNA(shRNA)into the BMDM. Results: The treatment of BMDM with LPS/ATP, LPS/nigericin or MRSA alone caused cytotoxicity and up-regulated the expression of pro-inflammatory cytokines, IL-1β, IL-6 and TNF-α, as well as the caspase-1 activation and mature Zl-1β (P<0.01). After silencing NLRP3 or NLRC4, the expression of IL-1β induced by MRSA was significantly lessened(P< 0.01). Conclusion: MRSA could induce BMDM pyroptosis probably via activating NLRP3 inflammasome or NLRC4 inflammasome.
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En la última década han sido cada vez más frecuentes los informes de infecciones causadas porcepas de Staphylococcus aureus resistente a meticilina asociadas a la comunidad (CA-MRSA,por Community-associated methicillin-resistant S. aureus). La colonización juega un papelimportante en la epidemiología de tales infecciones. Sin embargo, los estudios de colonizaciónse han centrado principalmente en el ambiente hospitalario y se han hecho muy pocos en lacomunidad. En este trabajo se investigó la frecuencia de colonización por S. aureus en generaly por MRSA en las manos de individuos de la población general no relacionados con el área dela salud, empleando métodos fenotípicos y moleculares. Se obtuvieron mediante hisopado 800muestras de las manos de otros tantos individuos. Se halló colonización por Staphylococcusaureus en 65 muestras (8,1%) y por MRSA en 5 (0,63%). Las 5 cepas de MRSA presentaban elcasete cromosómico mec (SCCmec) de los tipos IV o V, típicamente relacionados con CA-MRSA.Nuestro trabajo evidenció la colonización de las manos por MRSA en individuos de la comunidad,lo cual constituye un importante factor de riesgo, no solo por su asociación con el desarrolloulterior de infecciones, sino también por el potencial de diseminar este microorganismo a lapoblación general.
Community-associated methicillin-resistant Staphylococcus aureus infections (CA-MRSA) havebeen reported with increasing frequency during the past decade. Colonization plays an importantrole in the epidemiology of such infections. However, colonization studies have focused mostlyon hospital settings and only a few have been carried out in communities. This was a study of thefrequency of hand colonization by S. aureus in generaland by CA-MRSA, by means of phenotypical andmolecular methods, in 800 adults from the communitywho had no relationship with the health area.Staphylococcus aureus colonization was found in 65individuals (8.1%) and MRSA was present in 5 (0.63%).The 5 MRSA strains were found to have mecchromosomic cassettes (SCCmec) of either type IV orV, typical of CA-MRSA. Our study provides evidence ofCA-MRSA colonization in the hands of individuals fromthe community. This constitutes an important riskfactor, not only by its association with subsequentinfections, but also for the risk of dissemination of thismicroorganism to the general population.
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Humans , Staphylococcus aureus/growth & development , Staphylococcus aureus/pathogenicityABSTRACT
OBJECTIVE To investigate the resistance of meticillin-resistant Staphylococcus aureus(MRSA) and the occurrence of gene erm.METHODS ATB Staph and microdilute tests were performed to detect the susceptibility to 15 kinds of antibiotics in 50 strains of the S.aureus(SAU).Gene erm of these strains was detected by polymerase chain reaction(PCR).RESULTS There were no strains resistant to vancomycin,teicoplanin,fusidic acid and quinupristin-dalfopristin in 42 strains of MRSA detected.There were no strains sensitive to penicillin,oxacillin,gentamicin,tetracycline,ciprofloxacin and levofloxacin.Thirty-five strains habored gene erm in 42 strains of MRSA.The positive rate of gene erm was 83.3%.CONCLUSIONS The multiple-resistance of the MRSA is a serious issue.The resistance to erythromycin in MRSA is mediated by gene erm which encodes the methylase and changes the target site of drug action.
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OBJECTIVE To study the drug resistance,drug-resistant genes and disinfectant-resistant genes of clinical MRSA isolates.METHODS The sensitivity to penicillin and other 15 antibacterial agents was detected in 56 strains of MRSA by K-B paper disk diffusion.The mecA gene of the ?-lactamase and disinfectant-resistant genes qac(A/B)were detected by PCR.RESULTS All of the 56 strains of MRSA were sensitive to vancomycin and teicoplanin.Drug resistant rate of sulfamethoxzole/trimethoprim,nitrofurantoin,rifampin,tetracycline,levofloxacin,clindamycin and azithromycin were 17.9%,23.2%,82.1%,87.5%,89.3%,92.9% and 96.4%,respectively.All of the 56 strains were resistant to erythromycin,gentamicin,amikacin,penicillin,ampicillin/sulbactam,cefoxitin and ampicillin.In all 56 strains of MRSA,54(96.4%)MRSA isolates were mecA positive and 31(55.4%)MRSA isolates were qac(A/B)positive.CONCLUSIONS Clinically isolated MRSAs is multi-drug-resistant and the qac(A/B)positive rate is very high.
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OBJECTIVE To investigate and analyze the reasons of nosocomial infection(NI) in patients in intensive care unit( ICU),to find effective countermeasures for preventing NI and reducing the incidence rate of NI in ICU,and to enhance the management of ICU.METHODS All data of patients who suffered MRSA in ICU from Dec 2005 to Feb 2006,were analyzed by prospective monitoring and retrospective studies.RESULTS The nine patients were with lower respiratory tract.All were infected by the same MRSA.The same MRSA strain was found from hand,mouth and nose among the treating doctor and nurses based on the sample-analysis.CONCLUSIONS The incidence rate of NI in ICU is much higher than that in other departments.Risk factors depend on the severity of underlying diseases,invasive procedure,the quality of disinfection and sterilization,the incorrect use of the antibiotic,and patients′ immunity status especially among elderly.The key way to reduce incidence rate of NI is to take comprehensive measures and strengthen the antibiotic management.
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OBJECTIVE To study the drug resistance,drug-resistant genes and(disinfectant)-resistant genes of(MRS)A.METHODS The drug resistance and mecA gene of the ?-lactamase and aac(6′)/aph(2″),aph(3′)-Ⅲ,ant(4′,4″) genes of aminoglycoside and qac(A/B) disinfectant-resistant genes were(detected) in 47 strains of MRSA.(RESULTS) In all 47 strains of MRSA,46 MRSA isolates were mecA positive,39 MRSA isolates were aac(6′)/aph(2″) positive,30 MRSA isolates were aph(3′)-Ⅲ positive,6 MRSA isolates were ant(4′,4″) positive,and 19 MRSA isolates were qac(A/B) positive.CONCLUSIONS MRSA is multiple-drug resistant.The main resistant mechanisms of MRSA to aminoglycosides and disinfectant are related to the drug-resistant genes of aminoglycoside and disinfectant-resistant genes.Clinic physician must pay attention to the diagnosis and(therapy) of MRSA,and control the hospital infection.
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OBJECTIVE To screen the anti-meticillin-resistant Staphylococcus aureus(MRSA)traditional Chinese materia medica(TCMM)by biosensor technique,targeted on the soluble penicillin binding protein 2a(PBP2a)of clinical MRSA.METHODS The soluble PBP2a with amino acid sequence from 25 to 668 from clinical MRSA were expressed in Escherichia coli by gene recombination technique.Then,the expressed product was identified and its biological function was analyzed.After the PBP2a was immobilized into the carboxymethyl dextran cuvette(CMD),the anti-MRSA TCMM was screened by means of biosensor.RESULTS The soluble protein PBP2a had been successfully expressed,whose relative molecular mass was 74?103.It was confirmed that the soluble PBP2a had transpeptidase activitiy and ?-lactamase activitiy.Subsequently,10 kinds of anti-MRSA TCMM were screened out by biosensor technique.Moreover,Radix Scutellariae,Rhizoma Coptidis and Spica Prunellae had greater anti-MRSA effect than others.CONCLUSIONS Anti-MRSA TCMM has been successfully screened out by biosensor technique,targeted on the soluble PBP2a of clinical MRSA.
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OBJECTIVE To investigate the genotypes of meticillin-resistant Staphylococcus aureus(MRSA)and its resistance.METHODS A total of 73 MRSA clinical isolates were collected in Anhui Province,MIC of sixteen different antibacterial agents against the isolates were determined by agar dilution method.PCR amplified the mec associated hypervariable region(HVR)of MRSA,and the genotypes were classified based on the fragments of amplified products.The correlation of genotypes and antimicrobial resistance was analyzed.RESULTS Seventy three strains of MRSA from Anhui Province were grouped into A,B and C genotypes based on HVR polymorphism,and respectively 17.8%,23.3%,and 58.8%.All strains were sensitive to vancomycin.CONCLUSIONS MRSA is multi-drug resistant and can be divided into 3 genotypes based on the HVR PCR amplified products.HVR PCR method is a rapid and convenient method for molecular epidemiology study of MRSA infections.