| Summary: | 博士 === 國立中興大學 === 分子生物學研究所 === 92 === (一) In Taiwan, the number of pertussis cases has been increasing in the recent years, especially in 1997. In addition to the sporadic cases, pertussis also occurred in outbreaks of household, elementary school, and nosocomial infections. Since 71% of reported cases concentrated in the Taipei metropolitan area, it elicited a great deal of concern that a highly contagious strain of Bordetella pertussis might have appeared in Taipei. Therefore, a total of 114 strains of B. pertussis were collected and typed by the molecular method of pulsed-field gel electrophoresis (PFGE). These examined strains include 61 clinical isolates in 1997 and 53 control strains isolated in the previous years (1992~1996). All these strains were classified into 21 subtypes and among them the 1997 collection showed 17 subtypes with 9 new subtypes as compared to those collected in the previous years. This result indicated that the pertussis outbreaks in 1997 were not results of a sole specific virulent strain. It also implies that highly dense population may facilitate the spread and accelerate the genetic divergency of this pathogen.
(二) With 6 separate wards accommodating over 1,600 patients, VNC is a long-stay psychiatric nursing center in eastern Taiwan. During 2001-2003, 39 shigellosis cases occurred in VNC. Different from the notion that most of shigellosis cases are caused by Shigella sonnei, these strains were all S. flexneri except one S. sonnei isolate. O-antigen serotyping showed that the 38 S. flexneri strains were either type 1a (n=20) or 4a (n=18), the two less prevalent serotypes in Taiwan. NotI-PFGE analyses, using 8 1a and 9 4a non-VNC strains isolated during 1996-2003 for comparison, divided the 28 1a and 27 4a strains into 7 and 10 subtypes, designated P1A to P1G and P4A to P4J, respectively. P1A and P4A, appearing in three consecutive years in VNC as well as outside of VNC, are the most prevalent subtypes. Relatedness analyses of the VNC strains based on banding patterns grouped the 1a and 4a strains into 4 and 5 clusters, respectively. The 1a strains, except one, share 95% similarity indicating a common parent, whereas the 4a strains share similarities ranging from 77 to 93% suggesting diverse origins. In two of the outbreaks, less related subtypes of 4a strains were found in the same VNC wards in consecutive years, suggesting possible existence of different subtypes in VNC all the time. Antibiotic susceptibility test showed that the S. flexneri strains are sensitive to at least 7 antibiotics, except one isolate which is sensitive to 3 antibiotics. The data of the latter tests should be helpful for treating S. flexneri infections in Taiwan.
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