Evolution, Molecular ; Methicillin Resistance ; Staphylococcus aureus ; classification ; drug effects ; genetics ; isolation & purification

OBJECTIVETo detect the enterotoxin genes of Staphylococcus aureus (SA) isolated from clinical specimens and analyze the correlation between enterotoxin genes and drug resistance of SA.

METHODSThe mecA gene and enterotoxin genes A-F of clinical SA isolates were identified by polymerase chain reaction (PCR), and the genes were sequenced to investigate the correlation of these genes to drug resistance.

RESULTSThe detection rate of enterotoxin genes was 100% in 67 methicillin- resistant SA (MRSA), showing no significant difference from the rate in 57 methicillin-sensitive SA (MSSA) (83.5%, χ(2)=0.203, P>0.05). Of the 116 strains carrying enterotoxin genes (93.5%), the detection rates of SEA, SEB, SEC, SED and SEF were 90.5%, 6.9%, 61.3%, 5.2%, 25.9% and 93.5%, respectively, and none of the strains were positive for SEE gene. In these strains, 78 (67.2%) carried 2 or more enterotoxin genes, and the main genotypes were SEA and SEC (33.6%), SEA and SEF (7.8%), and SEA and SEC and SEF (13.8%). Compared with the strains carrying a single enterotoxin gene, those with multiple enterotoxin genes showed a higher drug resistance rate, among which 75% of the SA strains carrying SEA+SEC+SEF were resistant to SXT, significantly higher than the rates of SA carrying SEA (28.6%) and SEA+SEC (38.7%) (P<0.05). The SA strains carrying SEA+SEC+SEF and SEA+SEF showed significantly higher amikacin resistance rates than SA strain carrying SEA (75.0%, 77.0%, 21.5%, respectively, P<0.05).

CONCLUSIONClinical isolates of SA carrying multiple enterotoxin genes have a higher drug resistance rate than those with a single enterotoxin gene, suggesting the the important role of enterotoxin in multidrug resistance.

Drug Resistance, Multiple, Bacterial ; genetics ; Enterotoxins ; genetics ; Humans ; Staphylococcal Infections ; microbiology ; Staphylococcus aureus ; drug effects ; genetics ; isolation & purification

BACKGROUND: Susceptibility testing of Staphylococcus aureus often requires cumbersome supplementary tests. MicroScan Pos Breakpoint Combo Panel Type 28 (PBC28) (Siemens, USA) includes cefoxitin screening to detect methicillin-resistant Staphylococcus aureus (MRSA), inducible clindamycin resistance detection (ICD), and determination of low-range minimum inhibitory concentration of vancomycin (0.5-16 microgram/mL). The purpose of this study was to evaluate the performance of PBC28 in comparison with that of Pos Combo Type 1A (PC1A) (Siemens). METHODS: From December 2009 to March 2010, 500 non-duplicate clinical isolates of S. aureus were tested with PC1A and PBC28. Categorical agreements (CA) between the interpretations of the 2 panels were estimated. The presence of the mecA gene was determined by PCR, and double-disk diffusion test (D-test) was performed on the isolates resistant to erythromycin but susceptible or intermediately resistant to clindamycin. Ninety-six isolates representing various vancomycin minimum inhibitory concentrations (MICs) were tested in parallel with repeat PBC28, broth macrodilution, and epsilometer test (E test). RESULTS: The CA was 99.3% with a very major error (VME) of 0.2%, major error (ME) of 0.1%, and minor error (mE) of 0.4% in total. PBC28 showed 100% CA for 1 isolate with vancomycin MIC of 4 microgram/mL and 35 isolates (7.0%) with MIC of 2 microgram/mL. However, only 15, 27, and 35 isolates with vancomycin MIC of 2 microgram/mL showed 100% CA in repeat PBC28, broth macrodilution, and E test, respectively. PC1A and PBC28 detected all 314 mecA-positive isolates. Among the 63 isolates tested with the D-test, 58 (92.1%) were positive, and the results were 100% concordant with those of ICD. CONCLUSIONS: PBC28 can be appropriate susceptibility testing of S. aureus, including MRSA detection and ICD. However, the lower-range vancomycin MIC test was not reproducible enough to reliably differentiate MIC of 2 microgram/mL from MIC< or =1 microgram/mL.
Anti-Bacterial Agents/*pharmacology ; Bacterial Proteins/genetics ; Cefoxitin/*pharmacology ; Clindamycin/*pharmacology ; Drug Resistance, Bacterial ; Methicillin-Resistant Staphylococcus aureus/genetics/isolation & purification ; *Microbial Sensitivity Tests ; Reagent Kits, Diagnostic ; Sensitivity and Specificity ; Staphylococcus aureus/*drug effects/genetics/isolation & purification ; Vancomycin/*pharmacology

BACKGROUND: We evaluated the performance of the BD MAX StaphSR Assay (SR assay; BD, USA) for direct detection of Staphylococcus aureus and methicillin resistance not only in S. aureus but also in coagulase-negative Staphylococci (CNS) from positive blood cultures. METHODS: From 228 blood culture bottles, 103 S. aureus [45 methicillin-resistant S. aureus (MRSA), 55 methicillin-susceptible S. aureus (MSSA), 3 mixed infections (1 MRSA+Enterococcus faecalis, 1 MSSA+MRCNS, 1 MSSA+MSCNS)], and 125 CNS (102 MRCNS, 23 MSCNS) were identified by Vitek 2. For further analysis, we obtained the cycle threshold (Ct) values from the BD MAX system software to determine an appropriate cutoff value. For discrepancy analysis, conventional mecA/mecC PCR and oxacillin minimum inhibitory concentrations (MICs) were determined. RESULTS: Compared to Vitek 2, the SR assay identified all 103 S. aureus isolates correctly but failed to detect methicillin resistance in three MRSA isolates. All 55 MSSA isolates were correctly identified by the SR assay. In the concordant cases, the highest Ct values for nuc, mecA, and mec right-extremity junction (MREJ) were 25.6, 22, and 22.2, respectively. Therefore, we selected Ct values from 0-27 as a range of positivity, and applying this cutoff, the sensitivity/specificity of the SR assay were 100%/100% for detecting S. aureus, and 97.9%/98.1% and 99.0%/95.8% for detecting methicillin resistance in S. aureus and CNS, respectively. CONCLUSIONS: We propose a Ct cutoff value for nuc/mec assay without considering MREJ because mixed cultures of MSSA and MRCNS were very rare (0.4%) in the positive blood cultures.
Anti-Bacterial Agents/pharmacology ; Bacteremia/diagnosis/microbiology ; Coagulase/metabolism ; Humans ; Methicillin-Resistant Staphylococcus aureus/drug effects/genetics/*isolation & purification ; Microbial Sensitivity Tests ; Oxacillin/pharmacology ; Reagent Kits, Diagnostic ; Staphylococcus/drug effects/enzymology/genetics/isolation & purification ; Staphylococcus aureus/drug effects/genetics/*isolation & purification

In recent years, Bacterial resistance is more and more serious for the irrational use of antibiotics produces resistant strains and other reasons. Human are trying to solve the problem from different ways, including the study of antimicrobial peptides. Defensin is one of the most important of antimicrobial peptides. A novel antimicrobial peptide, human beta-defensin 3, was isolated and demonstrated a salt-insensitive broad spectrum of potent antimicrobial activity against many potentially pathogenic microbes. The total RNA was extracted from human tonsil and the hbetaD-3 specific cDNA sequence was amplified with RT-PCR. After sequenced, the target DNA fragment was cloned into pQE-80L vector together with the DNA fragment encoding carrier protein DHFR. The recombinant vectors were transformed into E. coli M15 and the expression was induced based on the optimal values of the IPTG concentration incubation temperature and induction time determined in the previous section. The expressed proteins were analyzed by SDS-PAGE and Western-blotting. The mass of the recombinant protein was about 40% of total bacteria protein. Isolate and purify the target protein. The recombinant hbetaD-3 fusion proteins possess the antimicrobial activity to staphylococcus aureus, multiresistant staphylococcus aureus (only vancomycin-sensitive) and Candida albicans in the assay of drug susceptibility. Advanced study can be continued based on our experiments.
Cloning, Molecular ; Escherichia coli ; genetics ; Plasmids ; Recombinant Fusion Proteins ; biosynthesis ; isolation & purification ; pharmacology ; Staphylococcus aureus ; drug effects ; Tetrahydrofolate Dehydrogenase ; genetics ; beta-Defensins ; biosynthesis ; genetics ; pharmacology

OBJECTIVETo analyze the epidemiology of methicillin resistant Staphylococcus aureus (MRSA) in molecular level in burn centre of Shanghai Ruijin hospital.

METHODSThe vicissitude of Staphylococcus aureus in the burn centre from 2003 to 2005 was analyzed with software WHONET5. Multiprimer random amplified polymorphic DNA(RAPD) was used to analyze the homology of 17 MRSA strains.

RESULTSRAPD analysis (primer ERIC2 and RAPD7) showed that all 17 MRSA strains were identical (Burn-A type).

CONCLUSIONMRSA with same RAPD type is prevalent in our burn centre for many years, so emphasis should be laid on the anti-infection therapy and its cross infection control. Staphylococcus aureus;

Burn Units ; Humans ; Methicillin-Resistant Staphylococcus aureus ; drug effects ; genetics ; isolation & purification ; Microbial Sensitivity Tests ; Random Amplified Polymorphic DNA Technique ; Sequence Homology ; Staphylococcal Infections ; drug therapy ; microbiology

Staphylococcus aureus, or methicillin-resistant S. aureus (MRSA), is a significant pathogen in both nosocomial and community infections. Community-associated MRSA (CA-MRSA) strains tend to be multi-drug resistant and to invade hospital settings. This study aimed to assess the antimicrobial resistance and molecular characteristicsof nasal S. aureus among newlyadmitted inpatients.In the present study, 66 S. aureus isolates, including 10 healthcare-associated MRSA (HA-MRSA), 8 CA-MRSA, and 48 methicillin-sensitive S. aureus (MSSA) strains, were found in the nasal cavities of 62 patients by screening 292 newlyadmitted patients. Antimicrobial resistance and molecular characteristics of these isolates, including spa-type, sequence type (ST) and SCCmec type, were investigated. All isolates were sensitive to linezolid, teicoplanin, and quinupristin/dalfopristin, but high levels of resistance to penicillin and erythromycin were detected. According to D-test and erm gene detection results, the cMLSB and iMLSB phenotypes were detected in 24 and 16 isolates, respectively. All 10 HA-MRSA strains displayed the cMLSB phenotypemediated by ermA or ermA/ermC, while the cMLSB CA-MRSA and MSSA strains carried the ermB gene. Molecular characterization revealedall 10 HA-MRSA strains were derived from the ST239-SCCmec III clone, and four out of eight CA-MRSA strains were t437-ST59-SCCmec V. The results suggest that patients play an indispensable role in transmitting epidemic CA-MRSA and HA-MRSA strains.
Anti-Bacterial Agents/*pharmacology ; Bacterial Proteins/genetics ; Drug Resistance, Multiple, Bacterial/genetics ; Humans ; Inpatients ; Methicillin-Resistant Staphylococcus aureus/*drug effects/genetics/isolation & purification ; Methyltransferases/genetics ; Microbial Sensitivity Tests ; Nasal Cavity/*microbiology ; Staphylococcal Infections/diagnosis/microbiology ; Staphylococcus aureus/*drug effects/genetics/isolation & purification

OBJECTIVETo study the resistance of staphylococcus aureus (S. aureus) isolated from children in Hangzhou to antibiotics and analyze the clinical value of mecA-PCR in determining oxacillin-resistant isolates.

METHODSS. aureus isolates were screened by using latex agglutination test and identified with GPI card of Vitek system. Antibiotics sensitivity tests were performed using disk diffusion methods and tests for sensitivity to oxacillin and vancomycin were performed with a further E-test method. The mecA gene was detected with polymerase-chain reaction (PCR).

RESULTSOf all 259 S. aureus strains, 185 from clinical specimens in inpatients and 74 from pharyngeal swabs in healthy children, 247 strains (95.8%) were beta-lactamase-positive and resistant to penicillin, while 91.1% of all strains were sensitive to oxacillin. All the strains were sensitive to vacomycin and 91.9% of all the strains were susceptible to cefotaxime and ceftriaxone. Resistance to erythromycin, tetracycline, clindamycin, trimethoprim-sulfamethoxazole, chloramphenicol, ofloxacin and rifampin were 48.3%, 30.9%, 21.6%, 11.2%, 10.0%, 2.3% and 1.5%, respectively. The resistance rate to oxacillin, cefotaxime, and ceftriaxone in clinical strains were significantly higher than that in carried strains (P < 0.05), while erythromycin-resistance rate was significantly higher in carried strains than that in clinical isolates (P < 0.05). The mecA-PCR showed that the control strain ATCC25923 and all oxacillin-sensitive S. aureus were mecA-negative, while all oxacillin-resistant strains were mecA-positive instead. Only one strain was mecA-positive in 7 oxacillin-intermediate S. aureus strains.

CONCLUSIONOxacillin-resistance in S. aureus isolates was low, and mecA-PCR method is a good choice for rapid examination oxacillin-resistant strains.

Anti-Bacterial Agents ; pharmacology ; Bacterial Proteins ; genetics ; isolation & purification ; Cefotaxime ; pharmacology ; Ceftriaxone ; pharmacology ; Child ; Child, Preschool ; China ; Drug Resistance, Bacterial ; genetics ; Erythromycin ; pharmacology ; Humans ; Latex Fixation Tests ; Methicillin Resistance ; genetics ; Methicillin-Resistant Staphylococcus aureus ; drug effects ; Microbial Sensitivity Tests ; Oxacillin ; pharmacology ; Penicillin-Binding Proteins ; Penicillins ; pharmacology ; Polymerase Chain Reaction ; Staphylococcal Infections ; drug therapy ; microbiology ; Staphylococcus aureus ; drug effects ; genetics ; isolation & purification ; Vancomycin ; pharmacology

OBJECTIVETo investigate the contamination of Staphylococcus aureus isolates in ice cream by phenotypic typing and molecular typing.

METHODSThe Staphylococcus aureus isolates were separated from ice cream, filler, cutter, salves and material. The separated isolates were characterized by drug-resistance, staphylococcal enterotoxin (SEA-E), SE (A-E, G-J) genes and pulsed-field gel electrophoresis (PFGE) types.

RESULTTwo Staphylococcus aureus isolates were separated, one from ice cream, another from cutter. Their characteristics of drug-resistance, staphylococcal enterotoxin (SEA-E), SE (A-E,G-J) genes and PFGE type were the same.

CONCLUSIONThe two Staphylococcus aureus isolates were the same clone. The contaminated Staphylococcus aureus isolates could be traced to the contaminated cutters.

Anti-Bacterial Agents ; pharmacology ; Bacterial Typing Techniques ; Electrophoresis, Gel, Pulsed-Field ; Enterotoxins ; genetics ; Food Microbiology ; Ice Cream ; microbiology ; Microbial Sensitivity Tests ; Staphylococcus aureus ; classification ; drug effects ; isolation & purification

PBD-1 is an antibacterial peptide that plays an important role in defence system of porcine. To produce PBD-1 with bioactivity in Pichia pastoris, according to published amino acid sequence of porcine beta-defensin 1(PBD-1) and the partiality codon of yeast, the PBD-1 gene was synthesized by PCR and cloned into pPIC9K to construct the recombinant expression vector pPIC9K-PBD-1, the obtained recombinant plasmid was linearized by Sal I, and then transformed into SMD1168 by electroporation. Under the control of the promoter AOX1, an approximately 4.5 kD PBD-1 peptide was expressed. Antibacterial activity assay shows that the PBD-1 has the antibacterial activity on Staphylococcus aureus. This is the first secreted expression of porcine beta-defensin 1 gene in Pichia pastoris.
Animals ; Anti-Bacterial Agents ; biosynthesis ; isolation & purification ; pharmacology ; Cloning, Molecular ; Gene Expression ; Genetic Vectors ; genetics ; Pichia ; genetics ; Protein Engineering ; Staphylococcus aureus ; drug effects ; Swine ; genetics ; beta-Defensins ; biosynthesis ; genetics ; isolation & purification ; pharmacology