ABSTRACT
Objective To study on virulence characteristics and multilocus sequence type of Vibrio parahaemolyticus isolated from clinic in Beijing Tongren hospital.Methods Total 152 strains of Vibrio parahaemolyticus isolates were collected from diarrheal patients of outpatients in Beijing Tongren Hospital,Capital Medical University from 2009 to 2011.PCR was used to detect hemolysin gene thermo stable direct themolysin gene (tdh),TDH-related hemolysin gene (trh),type Ⅲ secretion system 2 (T3SS2α,T3SS2β)and systematic functional gene (toxRS/new,orf8) for pandemic 03∶ K6 clone and its derivatives.The genetic features of these strains were determined by multilocus sequence typing (MLST).Results 96％ (146/152) VP harbored tdh gene,2％ (3/152) VP harbored trh gene and 100％ (152/152) VP harbored T3SS2 gene.In this study there were 107 pandemic strains (both tdh and toxRS/new positive and trh negative),38 pathogenic strains (tdh positive and/or trh positive) and 6 nonpathogenic strains (both tdh and trh negative).All nonpathogenic strains harbored systematic functional gene (toxRS/new,orf8).Only one pathogenic strains harbored orf8 gene.One clone harbored all virulence gene.In this study there were 16 sequence types,and ST3 is the pandemic sequence type,including 113 strains,and four new sequence types were found.Conclusions In this study more than 90％ Vibrio haemolyticus harbored tdh gene and ST3 was the pandemic sequence type in Beijing.One can get bacterial pathogenic charateristic and population genetics information by virulence gene testing and MLST.
ABSTRACT
Objective To study the genotypic and biological characteristics of catheter-related MRSE isolates and to further provide information for the diagnosis and prevention of catheter-related bloodstream infection. Methods Thirty strains of catheter-related MRSE isolates were collected from venosus blood and whole blood of 30 inpatients including 20 males and 10 females from Beijing Tongren Hospital, Capital Medical University from January 2006 to December 2009. The genetic features of these strains were determined by MLST. PCR was used to detect the icoA gene (encoding the polysaccharide intercellular adhesion associated with pathogenicity), and the antimicrobial susceptibility test was detected by disc diffusion test. Results A total of 15 STs were obtained from 30 strains ST259, ST20, ST2 and ST235 were common clones obtained from 17 strains. Four novel STs were found and uploaded to the MLST database (http://www. mlst. net), including ST259 (6 strains), ST260 (1 strain), ST261 (1 strain) and ST262 (1 strain). The ST259 was the dominant clone of catheter-related MRSE isolates in this hospital, and 3 strains carrying icaA gene were detected in this study. Conclusion Some ST259 isolates express high pathogenesis among the four novel STs, which may make them as the pandemic strains in nosocomial infection, and this would increase the difficulty of the prevention and control of nosocomial infection.
ABSTRACT
Objective Based on active monitoring MRSA carriage for hospitalized patients, the relationship between colonization pressure and MRSA cross transmission in wards without rigorous contactisolation measures was analyzed, and the role of colonization pressure in predicting MRSA cross transmission was further evaluated. Methods From March to December 2009, active MRSA colonization screening was performed for 240 hospitalized patients in emergency ward and 94 cases in RICU in our hospital. rep-PCR method was employed to do homology analysis on MRSA strains obtained in this study. MRSA weekly colonization pressure, threshold colonization pressure ,cross transmission rate were calculated respectively. RR of MRSA cross transmission under higher level of colonization pressure and lower level of colonization pressure was analyzed. Results MRSA carriage rates on admission for patients in emergency wards and RICU were 6. 25% (15/2A0) and 13. 83 % (13/94) ,and MRSA cross transmission occurred in 13 weeks and 14 weeks in above two units, respectively. Threshold colonization pressures for above two units were 6. 49%and 17. 66%, respectively. For emergency ward, the MRSA cross transmission rate under higher level of colonization pressure was significantly higher than that under lower level of colonization pressure (x2 = 7. 10,P＜0. 01), the RR of MRSA transmission was 9. 61 (95% CI:1. 25-74.00). For RICU, the MRSA cross transmission rate under higher level of colonization pressure was significantly higher than that under lower level of colonization pressure(x2 = 12. 60, P＜0. 01 ), the RR of MRSA transmission was 15.87 (95% CI:2. 06-122. 10). Conclusions Higher level of colonization pressure is an important risk factor for MRSA transmission, and average colonization pressure can be used as a prediction index for MRSA transmission and strengthening prevention and control measures.