| Summary: | 碩士 === 國立臺灣大學 === 醫事技術學系 === 86 === In recent years, Streptococcus pneumoniae strains become one of
the most prevalent bacteria in clinical setting. The increasing
incidence of drug-resistant S. pneumoniae has a great impact
especially on the efficacy of penicillin and extended-spectrum
cephalosporins. The emergence of drug-resistant S. pneumoniae
provides a clinical dilemma for treating patients with bacteremia,
pneumonia, and meningitis caused by this organism. For bacteria
strains with resistance against penicillin or multiple antimicrobial
agents, their serotypes are only limited to a few specific types
(such as 14, 6B, 19F, 23F, 9V, 4, and 18C). Therefore, the medical
field shows its deep concern for vaccines against S. pneumoniae
again. The effectiveness of vaccines is related to the distribution
of serotypes of isolated bacteria strains in a given geographic
region and the inclusion of their species in the serotypes of
vaccines. Previous studies pointed out that for S. pneumoniae having
multiple drug resistance, their drug-resistant genes not only are
transmitted among bacteria strains of the same species or of the same
genus, but also can be spread by means of bacteria carriers among
different geographic regions. There are three main research
directions of this study. They are (1) to test the minimum inhibitory
concentrations (MICs) of five common antibiotics by means of the agar
dilution method for 156 clinical isolates of S. pneumoniae recovered
from the northern regions of Taiwan from 1995 to 1997; (2) to
identify all the serogroups of the 156 clinical isolates of S.
pneumoniae; (3) to study chromosomes and drug-resistant genotypes (
penicillin-binding protein genes ) of the penicillin-resistant
clinical isolates ( serogroup 23, 19, and 6), by means of molecular
biology. By doing so, its objective is to understand the correlation
and the resistant mechanism of the penicillin-resistant clinical
isolates. We find out that the penicillin resistance of these
clinical isolates of S. pneumoniae even attains such a high
percentage like 61.5%. The serogroups of penicillin-resistant
bacteria strains are mainly 23, 19, and 6. We apply the PCR-RFLP
(restriction fragment length polymorphism) to analyze and understand
the differences in penicillin-resistant mechanisms among 68 clinical
isolates of penicillin-resistant S. pneumoniae (serogroup 23, 19, and
6). We find that for these bacteria strains, there are altogether
five RFLP types for the pbp2b genes and five RFLP types for pbp2x
genes. In order to study the molecular epidemiology of infection, we
used the random amplified polymorphic DNA (RAPD) patterns generated
by arbitrarily primed PCR and pulsed-field gel electrophoresis
patterns to analyze 68 clinical isolates of penicillin-resistant S.
pneumoniae (serogroup 23, 19,and 6) into sixteen types ( clones ) and
then analyze them further into fifteen types by means of PFGE. We
conclude that the majority ( 61.5 ﹪) of these 156 clinical isolates
are resistant to penicillin, and the most ( 85﹪) of their serotypes
belong to the serotypes of the current 23-valent S. pneumoniae
vaccines. Among the 68 clinical isolates ( serotype 23, 19, and 6) of
penicillin-resistant S. pneumoniae, it is found that there is the
possibility of the horizontal transfer of PBP genes among clones.
Moreover, from the results of the PFGE and the RAPD, it can be seen
that clonal spreading among clinical isolates of S. pneumoniae did
occur. This should be taken into consideration.
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