Molecular Identification of Mutans Group Streptococci, NVS, and Gemella and Analysis on groESL Operon of Gemella morbillorum
Date Issued
2005
Date
2005
Author(s)
Hung, Wei-Chung
DOI
zh-TW
Abstract
Mutans group of streptococci is one of the five groups in viridans streptococci. Mutans streptococci consists of seven species which can be classified into eight serotypes a to h: Streptococcus mutans (serotypes c, e, and f), Streptococcus sobrinus (serotypes d and g), Streptococcus criceti (serotype a), Streptococcus downei (serotype h), Streptococcus ferus (serotype c), Streptococcus macacae (serotype c), and Streptococcus ratti (serotype b). According to previous reports, the most common species isolated from human sources are S. mutans and S. sobrinus. Species identification of mutans streptococci has been based on conventional methods including complicated biochemical tests, but it is time-consuming and sometimes unsatisfactory. In this study, we used groESL genes as a target for molecular identification. This PCR method could provide an alternative way for differentiation among members of mutans streptococci or from other viridans streptococci.
NVS (Abiotrophia defectiva, Granulicatella adiacens, and Granulicatella elegans) and Gemella species (Gemella haemolysans and Gemella morbillorum) were commensal organisms in humans and they were sometimes responsible for opportunistic endocarditis. NVS and Gemella species had some common features in phenotypic characteristics. They could not grow on blood agar plates but could grow on chocolate agars, although their colonies were very small. It was easily misidentified in the microscopic examination because NVS were pleiomorphic in gram stain while Gemella species were easily decolorized. Because of these common characteristics, we designed a multiplex PCR assay based on groESL genes to identify NVS and Gemella species. Four primers were used in the multiplex PCR assay in which the five organisms could classify into Abiotrophia species, Granulicatella species and Gemella species. Besides, a clinical isolate of Gemella haemolysans displayed <90% identity in groEL gene with its reference strain but they shared the highest degree of similarities in 16S rRNA gene. Gemella haemolysans may be more heterogeneous than Gemella morbillorum.
In our laboratory, we have successfully determined the full-length sequences of groESL operon in Gemella morbillorum. Unexpectedly, we could not find the CIRCE element, which was being found in groESL operons of gram positive bacteria, but found the CtsR binding site in the putative promoter region. This was an unusual event in gram positive bacteria. It was also confused that the heat shock response was not obvious in the data of northern blot and SDS-PAGE. Besides, it was seemed that termination of the groESL operon was not 100% efficient, and in some cases, the downstream gene could be cotranscribed as part of the operon. In this part of experiment, it relied on more data to confirm this observation.
Subjects
轉醣鏈球菌群
熱刺激蛋白
Mutans Group Streptococci
NVS
groESL
Gemella
Type
other
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