Background Staphylococcus aureus （S. aureus） remains as an important microbial pathogen resulting in community and nosocomial acquired infections with significant morbidity and mortality. Few reports for S. aureus i...Background Staphylococcus aureus （S. aureus） remains as an important microbial pathogen resulting in community and nosocomial acquired infections with significant morbidity and mortality. Few reports for S. aureus in lower respiratory tract infections （LRTIs） have been documented. The aim of this study was to explore the molecular epidemiology of S. aureus in LRTIs in China.Methods A multicenter study of the molecular epidemiology of S. aureus in LRTIs was conducted in 21 hospitals in Beijing, Shanghai and twelve other provinces from November 2007 to February 2009. All the collected S. aureus strains were classified as minimum inhibitory concentration （MIC）, mecA gene, virulence genes Panton-Valentine Leukocidin （PVL） and y-hemolysin （hlg）, staphylococcal cassette chromosome mec （SCCmec） type, agr type, and Multilocus Sequence Typinq （MLST）.Results Totally, nine methicillin-sensitive S. aureus （MSSA） and 29 methicillin-resistant S. aureus （MRSA） strains were isolated after culture from a total of 2829 sputums or bronchoalveolar lavages. The majority of MRSA strains （22/29） had a MIC value of 〉512 μg/ml for cefoxitin. The mecA gene acting as the conservative gene was carried by all MRSA strains. PVL genes were detected in only one S. aureus strain （2.63%, 1/38）. The hlg gene was detected in almost the all S. aureus （100% in MSSA and 96.56% in MRSA strains）. About 75.86% of MRSA strains carried SCCmec Ⅲ. Agr type 1 was predominant （78.95%） among the identified three agr types （agr types 1,2, and 3）. Totally, ten sequence type （ST） of S. aureus strains were detected. A new sequence type （ST1445） was found besides confirming ST239 as the major sequence type （60.53%）. A dendrogram generated from our own MLST database showed all the bootstrap values 〈50%. Conclusion Our preliminary epidemiology data show SCCmec Ⅲ, ST239 and agr type 1 of S. aureus as the predominant strains in LRTIs in Mainland of China.展开更多
Background Nosocomial infection caused by methicillin-resistant Staphylococcus aureus （MRSA） and vancomycin-resistant enterococci （VRE） could lead to increased morbidity and mortality. In 2006, VRE nosocomial spre...Background Nosocomial infection caused by methicillin-resistant Staphylococcus aureus （MRSA） and vancomycin-resistant enterococci （VRE） could lead to increased morbidity and mortality. In 2006, VRE nosocomial spread became a reality in our hospital since the first VRE nosocomial infection in 2003. Little is known about the prevalence of coexistence with VRE and MRSA in the patients. The primary objective of the study was to identify the molecular characteristics of epidemic MRSA clones in our hospital and the prevalence of the coexistence with MRSA and VRE in same patients during the 2-year period, 2006-2007. Methods The clinical features, laboratory test results, and therapeutic outcomes of 129 cases who isolated MRSA collected from January 2006 to December 2007 were retrospectively analyzed. Polymerase chain reaction （PCR） was used to determine mecA-femB type and staphylococcal cassette chromosome mec （SCCmec） type. All the participants were screened for clinical and microbiological data to identify the coexistence of VRE strains with MRSA. Results One hundred and twenty-nine MRSA isolates were included in the study： 71 （55%） from the intensive care unit, 35 （27.2%） from the surgical wards and 23 （17.8%） from the medical wards. The most frequent source of isolation of MRSA was sputum （76.7%）. From seven patients we isolated MRSA and VRE （E. faecium） simultaneously during their inpatient stay. One hundred and twenty-seven （127/129, 98.4%） MRSA isolates harboured SCCmec type Ⅲ, only 2 MRSA strains contained SCCmec type Ⅱ. All of the 129 MRSA isolates remained sensitive to vancomycin, teicoplanin and linezolid. Higher sensitivity rates were noted for chloramphenicol 99.2% （128/129）. Only 20.2% （26/129） of the MRSA isolates were sensitive to rifampin. All isolates presented resistance to multiple antimicrobial agents with high minimum inhibitory concentrations （MICs）, including： β-Iactams （penicillin, oxacillin, cefoxitin, and cefazolin）, tetracycline展开更多
Currently, therapy for squamous cancer （SqC） is unsatisfactory. Staphylococcal enterotoxin B （SEB） has strong immune regulatory activity. This study tests the hypothesis that SEB enforces the effect of immunothera...Currently, therapy for squamous cancer （SqC） is unsatisfactory. Staphylococcal enterotoxin B （SEB） has strong immune regulatory activity. This study tests the hypothesis that SEB enforces the effect of immunotherapy on SqC growth in a mouse model. C3H/HeN mice and the SqC cell line squamous cell carcinoma VII were used to create an SqC mouse model. Immune cell assessment was performed by flow cytometry. Real-time RT-PCR and western blotting were used to evaluate target molecule expression. An apoptosis assay was used to assess the suppressive effect of T helper-9 （Th9） cells on the SqC cells. The results showed that immunotherapy consisting of SEB plus SqC antigen significantly inhibited SqC growth in the mice. The frequency of Th9 cells was markedly increased in the SqC tissue and mouse spleens after treatment. SEB markedly increased the levels of signal transducer and activator of transcription 5 phosphorylation and the expression of histone deacetylase-1 （HDAC1） and PU.1 （the transcription factor of the interleukin 9 （IL-9） gene） in CD4^＋ T cells. Exposure to SqC-specific Th9 cells markedly induced SqC cell apoptosis both in vitro and in vivo. In conclusion, the administration of SEB induces Th9 cells in SqC-bearing mice, and theseTh9 cells inhibit SqC growth.展开更多
Staphylococcal enterotoxin A(SEA)derived from Staphylococcus aureus,as a superantigen,shows potential for cancer immunotherapy,but systemic immunotoxicity restricts its clinical application.Targeted delivery of SEA to...Staphylococcal enterotoxin A(SEA)derived from Staphylococcus aureus,as a superantigen,shows potential for cancer immunotherapy,but systemic immunotoxicity restricts its clinical application.Targeted delivery of SEA to tumor site provides a promising option for reducing the systemic toxicity.Here,we constructed an iRGD peptide(H-[Cys-Arg-Gly-Asp-Lys-Gly-Pro-Asp-Cys]-NH_(2))modified nanoparticle(iDPP)to deliver plasmids encoding SEA for melanoma treatment.The iDPP/SEA nanocomplexes efficiently mediated SEA expression in B16-F10 cells in vivo and in vitro and induced the activation of lymphocytes and maturation of murine bone marrow-derived dendritic cells(BMDCs)in vitro.In the subcutaneous B16-F10 melanoma model,the iDPP/SEA nanocomplexes could effectively enhance immune response and T lymphocytes infiltration in tumor site after intravenous administration,thereby considerably decreased melanoma growth.Meanwhile,no obvious adverse effect was observed after intravenous administration of the iDPP/SEA nanocomplexes in vivo.Our findings demonstrated that gene therapy of SEA is a potential candidate for melanoma treatment.展开更多
In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the re...In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.展开更多
The coagulase-negative staphylococci (CoNS) have long been considered to be low pathogenicity. The possibility of a horizontal transfer of resistance and virulence genes from S. aureus to CoNS could increase the patho...The coagulase-negative staphylococci (CoNS) have long been considered to be low pathogenicity. The possibility of a horizontal transfer of resistance and virulence genes from S. aureus to CoNS could increase the pathogenicity of these bacteria. The objective of this work is to contribute to a better knowledge of the pathogenicity of (CoNS) strains isolated from surfaces and medico-technical materials of the University Hospital of Abomey-Calavi/Sô-Ava. Seventy strains of CoNS isolated from surfaces and medico-technical materials of the University Hospital of Abomey-Calavi were tested for methicillin resistance. The resistance to methicillin was evaluated phenotypically by the resistance of the strains to cefoxitin and then confirmed by the search for the mecA gene using PCR. The genes encoding staphylococcal chromosomal cassette (SCCmec) types I, II and III originally found in S. aureus were tested in CoNS by multiplex PCR using specific primers. All the strains studied showed resistance to methicillin. However, only 28.5% (20/70) carried the mecA gene. SCCmec was identified in only 17.14% (12/70) of these strains. Four strains carried mecA gene as well as one of the three types of SCCmec searched. SCCmec types I, II and III were identified in CoNS strains studied. SCCmec type I was the most frequent chromosomal cassette in mecA<sup>+</sup> strains, only or in association with another SCCmec. The study also revealed methicillin-resistant strains carrying SCCmec lacking the mecA gene. Finally, 60% (12/20) of the strains were found to be non-typeable. Our results show that CoNS strains present a high resistance to methicillin and the source of this resistance in the CoNS of our study is not only the mecA gene. There is also a high diversity of SCCmec, justified by a large number of non-typeable CoNS strains. The mecA<sup>−</sup> SCCmec<sup>+</sup> methicillin-resistant strains deserve to be sequenced for further studies.展开更多
Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model an...Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model and Baranyi model were applied to model growth data of S. aureus between 15℃ and 37℃. Model comparisons indicated that Baranyi model described the growth data more accurately than two others with a mean square error of 0.0129. Growth rates generated from Baranyi model matched the observed ones with a bias factor of 0.999 and an accuracy factor of 1.01, and ft a square root model with respect to temperature; other two modifed models both overestimated the observed ones. SEA amount began to be detected when the cell number reached106.4 cfu ？ mL-1, and showed the linear correlation with time. Besides, the rate of SEA production ftted an exponential relationship as a function of temperature. Predictions based on the study could be applied to indicate possible growth of S. aureus and prevent the occurrence of staphylococcal food poisoning.展开更多
Objective:To determine the pattern of antibiotic resistance among Staphylococcus aureus(S. aureus) isolates from clinical specimens and to identify community-acquired methicillin-resistant Staphylococcus aureus(CA-MRS...Objective:To determine the pattern of antibiotic resistance among Staphylococcus aureus(S. aureus) isolates from clinical specimens and to identify community-acquired methicillin-resistant Staphylococcus aureus(CA-MRSA) in specimens that have been collected from patients referring to one of the hospitals of Ahvaz.Methods:S.aureus isolates from a hospital in Ahvaz were screened for resistance to various antibiotics including methicillin.The susceptibility of the isolates was determined by Kirby-Bauer disc diffusion method.The MRSA was also treated with ethidium bromide to find the origin of resistance.Results:Among the bacterial isolates,all of 11 S.aureus were resistant to methicillin and cefixime,2 were resistant to ciprofloxacin,6 were resistant to tetracycline and the reminder were sensitive or intermediate to other antibiotics.The treated isolates were reminded resistant to methicillin and this suggested that the plasmid was not the origin of resistance in these isolates.Conclusions:These results showed that infection due to MRSA is widespread in Ahvaz and with respect to the spread of vancomycin resistance among MRSA and appearance of overwhelming infections.It is necessary to identify continuously the profile of antibiotic resistance among S.aureus isolates in other regions and finding appropriate antibiotic for infection control and eradication.展开更多
The anti-tumor effect and mechanism of the staphylococcal enterotoxin A (SEA) were studied. The mouse gastric tumor model was produced by subcutaneously inoculating gastric tumor ceils (MGC80-3). The experimental grou...The anti-tumor effect and mechanism of the staphylococcal enterotoxin A (SEA) were studied. The mouse gastric tumor model was produced by subcutaneously inoculating gastric tumor ceils (MGC80-3). The experimental group was treated with SEA, and the control group was treated with normal saline. The percentage of tumor generation and tumor mass was measured. The results showed that the percentage of the tumor generation in the SEA-treated mice was lower than in the control group, but there was no significant difference (P>0. 05). However, the tumor mass in the experimental group was significantly lighter than in the control group, with the difference being very significant (P<0. 001). There were more CD4+ T cells and CD8+ T cells in the tumor of the mice treated with SEA than those of the control group. SEA has an obvious anti-tumor effect on mice gastric tumor. The mechanism might be that SEA induces the effect of superantigen-dependent cell mediated cytotoxicity to the tumor cells.展开更多
To investigate the clinical characteristics, diagnosis and therapy of influenza pneumonia with staphylococcal infection. One patient in our hospital was diagnosed and the literatures on the subject were reviewed. The ...To investigate the clinical characteristics, diagnosis and therapy of influenza pneumonia with staphylococcal infection. One patient in our hospital was diagnosed and the literatures on the subject were reviewed. The patient presented with high fever and dyspnea. Arterial gas analysis indicated type 1 respiratory failure. Chest X ray photographs showed bilateral infiltrations and bilatera encapsulated pleural effusions. Viral separation and culture of pharyngeal swab indicated H3N2 subtype of human influenza virus. Blood, sputum and bronchoalveolar lavage fluid (BALF) cultures showed Staphylococcus aureus. Pleural effusion was complex parapneumonic pleural effusion. After the administration of anti-virus, anti-staphylococcal antibiotics and pleural cavity drainage, the patient was cured. The infection of staphylococcus aureus is a typical characteristic of influenza pneumonia, and anti-staphylococcal antibiotic therapy (with MRSA activity in MRSA endemic regions) should be initiated in hospitalized cases of influenza pneumonia. If complex parapneumonic pleural effusion or empyema complicated, we should perform pleural cavity drainage in time. The oral neuraminidase inhibitor (oseltamivir) could significantly improve prognosis.展开更多
The carcinoembryonic antigen（CEA） is an oncofetal glycoprotein known as an important clinical tumor marker and is overexpressed in several types of tumors, including colorectal and lung carcinomas. We constructed a ...The carcinoembryonic antigen（CEA） is an oncofetal glycoprotein known as an important clinical tumor marker and is overexpressed in several types of tumors, including colorectal and lung carcinomas. We constructed a chimeric protein that exhibits both specific binding and immune stimulating activities, by fusing staphylococcal enterotoxin A（SEA） to the C-terminus of an anti-CEA single-chain disulfide-stabilized Fv（scdsFv） antibody （single-chain-C-terminus/SEA, SC-C/SEA）. The SC-C/SEA protein was expressed in Escherichia coli（E. coli）, refolded, and purified on an immobilized Ni2＋ affinity chromatography column. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis（SDS-PAGE） and Western blot analysis reveal that the target protein was expressed sufficiently. We used immunofluorescence assays to demonstrate that SC-C/SEA could bind specifically to human lung carcinoma cells（A549）, but almost human uterine cervix cells（HeLa）. We also used the L-lactate dehydrogenase（LDH） release assay to show that SC-C/SEA elicits a strong A549 tumor-specific cytotoxic T lymphocyte（CTL） response in vitro. The results suggest that SC-C/SEA shows specific activity against CEA-positive cells and has potential application in CEA-targeted cancer immunotherapy.展开更多
文摘Background Staphylococcus aureus （S. aureus） remains as an important microbial pathogen resulting in community and nosocomial acquired infections with significant morbidity and mortality. Few reports for S. aureus in lower respiratory tract infections （LRTIs） have been documented. The aim of this study was to explore the molecular epidemiology of S. aureus in LRTIs in China.Methods A multicenter study of the molecular epidemiology of S. aureus in LRTIs was conducted in 21 hospitals in Beijing, Shanghai and twelve other provinces from November 2007 to February 2009. All the collected S. aureus strains were classified as minimum inhibitory concentration （MIC）, mecA gene, virulence genes Panton-Valentine Leukocidin （PVL） and y-hemolysin （hlg）, staphylococcal cassette chromosome mec （SCCmec） type, agr type, and Multilocus Sequence Typinq （MLST）.Results Totally, nine methicillin-sensitive S. aureus （MSSA） and 29 methicillin-resistant S. aureus （MRSA） strains were isolated after culture from a total of 2829 sputums or bronchoalveolar lavages. The majority of MRSA strains （22/29） had a MIC value of 〉512 μg/ml for cefoxitin. The mecA gene acting as the conservative gene was carried by all MRSA strains. PVL genes were detected in only one S. aureus strain （2.63%, 1/38）. The hlg gene was detected in almost the all S. aureus （100% in MSSA and 96.56% in MRSA strains）. About 75.86% of MRSA strains carried SCCmec Ⅲ. Agr type 1 was predominant （78.95%） among the identified three agr types （agr types 1,2, and 3）. Totally, ten sequence type （ST） of S. aureus strains were detected. A new sequence type （ST1445） was found besides confirming ST239 as the major sequence type （60.53%）. A dendrogram generated from our own MLST database showed all the bootstrap values 〈50%. Conclusion Our preliminary epidemiology data show SCCmec Ⅲ, ST239 and agr type 1 of S. aureus as the predominant strains in LRTIs in Mainland of China.
基金The study was supported by-grants from the National Natural Science Foundation of China （No. 30870094/C010603） and the Beijing Science ＆ Technology （No. Z08050700020801）.
文摘Background Nosocomial infection caused by methicillin-resistant Staphylococcus aureus （MRSA） and vancomycin-resistant enterococci （VRE） could lead to increased morbidity and mortality. In 2006, VRE nosocomial spread became a reality in our hospital since the first VRE nosocomial infection in 2003. Little is known about the prevalence of coexistence with VRE and MRSA in the patients. The primary objective of the study was to identify the molecular characteristics of epidemic MRSA clones in our hospital and the prevalence of the coexistence with MRSA and VRE in same patients during the 2-year period, 2006-2007. Methods The clinical features, laboratory test results, and therapeutic outcomes of 129 cases who isolated MRSA collected from January 2006 to December 2007 were retrospectively analyzed. Polymerase chain reaction （PCR） was used to determine mecA-femB type and staphylococcal cassette chromosome mec （SCCmec） type. All the participants were screened for clinical and microbiological data to identify the coexistence of VRE strains with MRSA. Results One hundred and twenty-nine MRSA isolates were included in the study： 71 （55%） from the intensive care unit, 35 （27.2%） from the surgical wards and 23 （17.8%） from the medical wards. The most frequent source of isolation of MRSA was sputum （76.7%）. From seven patients we isolated MRSA and VRE （E. faecium） simultaneously during their inpatient stay. One hundred and twenty-seven （127/129, 98.4%） MRSA isolates harboured SCCmec type Ⅲ, only 2 MRSA strains contained SCCmec type Ⅱ. All of the 129 MRSA isolates remained sensitive to vancomycin, teicoplanin and linezolid. Higher sensitivity rates were noted for chloramphenicol 99.2% （128/129）. Only 20.2% （26/129） of the MRSA isolates were sensitive to rifampin. All isolates presented resistance to multiple antimicrobial agents with high minimum inhibitory concentrations （MICs）, including： β-Iactams （penicillin, oxacillin, cefoxitin, and cefazolin）, tetracycline
基金This study was supported by grants from the Innovation of Science and Technology Commission of Shenzhen Municipality （JCYJ20140418095735538, JCYJ20120613161724279 JCYJ20120613172559904+3 种基金 JCYJ20130329110735981 JCYJ20120613173233810） International Collaboration Project （GJHZ20130408174112021） and the National Nature Science Foundation and China （81373176）.
文摘Currently, therapy for squamous cancer （SqC） is unsatisfactory. Staphylococcal enterotoxin B （SEB） has strong immune regulatory activity. This study tests the hypothesis that SEB enforces the effect of immunotherapy on SqC growth in a mouse model. C3H/HeN mice and the SqC cell line squamous cell carcinoma VII were used to create an SqC mouse model. Immune cell assessment was performed by flow cytometry. Real-time RT-PCR and western blotting were used to evaluate target molecule expression. An apoptosis assay was used to assess the suppressive effect of T helper-9 （Th9） cells on the SqC cells. The results showed that immunotherapy consisting of SEB plus SqC antigen significantly inhibited SqC growth in the mice. The frequency of Th9 cells was markedly increased in the SqC tissue and mouse spleens after treatment. SEB markedly increased the levels of signal transducer and activator of transcription 5 phosphorylation and the expression of histone deacetylase-1 （HDAC1） and PU.1 （the transcription factor of the interleukin 9 （IL-9） gene） in CD4^＋ T cells. Exposure to SqC-specific Th9 cells markedly induced SqC cell apoptosis both in vitro and in vivo. In conclusion, the administration of SEB induces Th9 cells in SqC-bearing mice, and theseTh9 cells inhibit SqC growth.
基金supported by the National Natural Science Foundation(No.82073363)the Sichuan Science and Technology Program(Nos.2020YFQ0059,2022YFQ0004)the Natural Science Foundation of Sichuan Province(No.2022NSFSC1304).
文摘Staphylococcal enterotoxin A(SEA)derived from Staphylococcus aureus,as a superantigen,shows potential for cancer immunotherapy,but systemic immunotoxicity restricts its clinical application.Targeted delivery of SEA to tumor site provides a promising option for reducing the systemic toxicity.Here,we constructed an iRGD peptide(H-[Cys-Arg-Gly-Asp-Lys-Gly-Pro-Asp-Cys]-NH_(2))modified nanoparticle(iDPP)to deliver plasmids encoding SEA for melanoma treatment.The iDPP/SEA nanocomplexes efficiently mediated SEA expression in B16-F10 cells in vivo and in vitro and induced the activation of lymphocytes and maturation of murine bone marrow-derived dendritic cells(BMDCs)in vitro.In the subcutaneous B16-F10 melanoma model,the iDPP/SEA nanocomplexes could effectively enhance immune response and T lymphocytes infiltration in tumor site after intravenous administration,thereby considerably decreased melanoma growth.Meanwhile,no obvious adverse effect was observed after intravenous administration of the iDPP/SEA nanocomplexes in vivo.Our findings demonstrated that gene therapy of SEA is a potential candidate for melanoma treatment.
文摘In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.
文摘The coagulase-negative staphylococci (CoNS) have long been considered to be low pathogenicity. The possibility of a horizontal transfer of resistance and virulence genes from S. aureus to CoNS could increase the pathogenicity of these bacteria. The objective of this work is to contribute to a better knowledge of the pathogenicity of (CoNS) strains isolated from surfaces and medico-technical materials of the University Hospital of Abomey-Calavi/Sô-Ava. Seventy strains of CoNS isolated from surfaces and medico-technical materials of the University Hospital of Abomey-Calavi were tested for methicillin resistance. The resistance to methicillin was evaluated phenotypically by the resistance of the strains to cefoxitin and then confirmed by the search for the mecA gene using PCR. The genes encoding staphylococcal chromosomal cassette (SCCmec) types I, II and III originally found in S. aureus were tested in CoNS by multiplex PCR using specific primers. All the strains studied showed resistance to methicillin. However, only 28.5% (20/70) carried the mecA gene. SCCmec was identified in only 17.14% (12/70) of these strains. Four strains carried mecA gene as well as one of the three types of SCCmec searched. SCCmec types I, II and III were identified in CoNS strains studied. SCCmec type I was the most frequent chromosomal cassette in mecA<sup>+</sup> strains, only or in association with another SCCmec. The study also revealed methicillin-resistant strains carrying SCCmec lacking the mecA gene. Finally, 60% (12/20) of the strains were found to be non-typeable. Our results show that CoNS strains present a high resistance to methicillin and the source of this resistance in the CoNS of our study is not only the mecA gene. There is also a high diversity of SCCmec, justified by a large number of non-typeable CoNS strains. The mecA<sup>−</sup> SCCmec<sup>+</sup> methicillin-resistant strains deserve to be sequenced for further studies.
基金Supported by"Academic Backbone"Project of Northeast Agricultural University(15XG26)the National High-level Talents Special Support Program of China
文摘Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model and Baranyi model were applied to model growth data of S. aureus between 15℃ and 37℃. Model comparisons indicated that Baranyi model described the growth data more accurately than two others with a mean square error of 0.0129. Growth rates generated from Baranyi model matched the observed ones with a bias factor of 0.999 and an accuracy factor of 1.01, and ft a square root model with respect to temperature; other two modifed models both overestimated the observed ones. SEA amount began to be detected when the cell number reached106.4 cfu ？ mL-1, and showed the linear correlation with time. Besides, the rate of SEA production ftted an exponential relationship as a function of temperature. Predictions based on the study could be applied to indicate possible growth of S. aureus and prevent the occurrence of staphylococcal food poisoning.
基金Shahid Chamran University for providing the research grant
文摘Objective:To determine the pattern of antibiotic resistance among Staphylococcus aureus(S. aureus) isolates from clinical specimens and to identify community-acquired methicillin-resistant Staphylococcus aureus(CA-MRSA) in specimens that have been collected from patients referring to one of the hospitals of Ahvaz.Methods:S.aureus isolates from a hospital in Ahvaz were screened for resistance to various antibiotics including methicillin.The susceptibility of the isolates was determined by Kirby-Bauer disc diffusion method.The MRSA was also treated with ethidium bromide to find the origin of resistance.Results:Among the bacterial isolates,all of 11 S.aureus were resistant to methicillin and cefixime,2 were resistant to ciprofloxacin,6 were resistant to tetracycline and the reminder were sensitive or intermediate to other antibiotics.The treated isolates were reminded resistant to methicillin and this suggested that the plasmid was not the origin of resistance in these isolates.Conclusions:These results showed that infection due to MRSA is widespread in Ahvaz and with respect to the spread of vancomycin resistance among MRSA and appearance of overwhelming infections.It is necessary to identify continuously the profile of antibiotic resistance among S.aureus isolates in other regions and finding appropriate antibiotic for infection control and eradication.
文摘The anti-tumor effect and mechanism of the staphylococcal enterotoxin A (SEA) were studied. The mouse gastric tumor model was produced by subcutaneously inoculating gastric tumor ceils (MGC80-3). The experimental group was treated with SEA, and the control group was treated with normal saline. The percentage of tumor generation and tumor mass was measured. The results showed that the percentage of the tumor generation in the SEA-treated mice was lower than in the control group, but there was no significant difference (P>0. 05). However, the tumor mass in the experimental group was significantly lighter than in the control group, with the difference being very significant (P<0. 001). There were more CD4+ T cells and CD8+ T cells in the tumor of the mice treated with SEA than those of the control group. SEA has an obvious anti-tumor effect on mice gastric tumor. The mechanism might be that SEA induces the effect of superantigen-dependent cell mediated cytotoxicity to the tumor cells.
文摘To investigate the clinical characteristics, diagnosis and therapy of influenza pneumonia with staphylococcal infection. One patient in our hospital was diagnosed and the literatures on the subject were reviewed. The patient presented with high fever and dyspnea. Arterial gas analysis indicated type 1 respiratory failure. Chest X ray photographs showed bilateral infiltrations and bilatera encapsulated pleural effusions. Viral separation and culture of pharyngeal swab indicated H3N2 subtype of human influenza virus. Blood, sputum and bronchoalveolar lavage fluid (BALF) cultures showed Staphylococcus aureus. Pleural effusion was complex parapneumonic pleural effusion. After the administration of anti-virus, anti-staphylococcal antibiotics and pleural cavity drainage, the patient was cured. The infection of staphylococcus aureus is a typical characteristic of influenza pneumonia, and anti-staphylococcal antibiotic therapy (with MRSA activity in MRSA endemic regions) should be initiated in hospitalized cases of influenza pneumonia. If complex parapneumonic pleural effusion or empyema complicated, we should perform pleural cavity drainage in time. The oral neuraminidase inhibitor (oseltamivir) could significantly improve prognosis.
基金Supported by the Innovation Fund of Graduate of Jilin University, China(No.20101035)the China Postdoctoral ScienceFoundation Project(No.20100481057)
文摘The carcinoembryonic antigen（CEA） is an oncofetal glycoprotein known as an important clinical tumor marker and is overexpressed in several types of tumors, including colorectal and lung carcinomas. We constructed a chimeric protein that exhibits both specific binding and immune stimulating activities, by fusing staphylococcal enterotoxin A（SEA） to the C-terminus of an anti-CEA single-chain disulfide-stabilized Fv（scdsFv） antibody （single-chain-C-terminus/SEA, SC-C/SEA）. The SC-C/SEA protein was expressed in Escherichia coli（E. coli）, refolded, and purified on an immobilized Ni2＋ affinity chromatography column. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis（SDS-PAGE） and Western blot analysis reveal that the target protein was expressed sufficiently. We used immunofluorescence assays to demonstrate that SC-C/SEA could bind specifically to human lung carcinoma cells（A549）, but almost human uterine cervix cells（HeLa）. We also used the L-lactate dehydrogenase（LDH） release assay to show that SC-C/SEA elicits a strong A549 tumor-specific cytotoxic T lymphocyte（CTL） response in vitro. The results suggest that SC-C/SEA shows specific activity against CEA-positive cells and has potential application in CEA-targeted cancer immunotherapy.
