Identification of bovis group streptococci by PCR-RFLP based on groESL sequence and analysis of erythromycin-resistance determinant
Date Issued
2005
Date
2005
Author(s)
Chen, Hsiao-Jan
DOI
zh-TW
Abstract
Streptococcus bovis group is normal flora of the ruminant and human gut, but will also cause serious infections. Many reports have suggested a potential relationship between underlying infection with this organism and colon cancers. According to biochemical characteristics, S. bovis strains were divided into three biotypes, biotype I, Ⅱ/1 and Ⅱ/2. The clinical identification of bovis group depends on conventional methods or commercial rapid identification systems. But these two methods are time-consuming and not satisfactory. The diversity of biochemical characteristics of bovis group may lead to misidentification. Recently scientists have developed molecular identification based on 16S rRNA gene sequence. Limited to the highly conservation of 16S rRNA gene sequence, it is difficult to differentiate closely related species. Since the taxonomy of the species within bovis group has been proposed, the aim of this part of study was to develop a more rapid and reliable method for identification. In this study, we analyzed groESL sequences, which are ubiquitous and evolutionarily highly conserved, to understand the correlation between the phylogenetic evolution and the biotypes by PCR-direct sequencing method. The results revealed that isolates with the same biotype usually belong to the same genocluster. Then we designed specific PCR for the bovis group, and developed PCR-RFLP method to subsequently differentiate three biotypes.
Resistance to erythromycin in S. bovis is mostly due to the target modification, which is mediated by erythromycin ribosome methylation (erm) that methylates 23S rRNA and induces ribosome modification. Because the target site of erythromycin is overlap with Lincosamide and Streptogramin B，ribosome modification can cause three antibiotics resistance known as macrolide-lincosamide-streptogramin B (MLSB) resistance. Expression of MLSB resistance can be either constitutive (cMLSB) or inducible (iMLSB). In previous studies, we found high rate of iMLSB strains in S. bovis. Detection of erythromycin resistance genes by PCR and sequence indicated that some iMLSB strains had erm(T) that is not reported in streptococci before. In this study, we analyzed the structures of erm(T) gene in these iMLSB strains. The SmaI PFGE fragments revealed the heterogeneity and not the expansion of a single clone. Furthermore, we have confirmed that the erm(T) resistance gene is located on chromosome.
Subjects
groESL基因
PCR-RFLP鑑定
bovis群鏈球菌
紅黴素
groESL sequence
PCR-RFLP
bovis group streptococci
erythromycin
SDGs
Type
other