16S-23S rDNA Spacer Region Research Articles

An evaluation of intergenic rRNA gene sequence length polymorphism analysis for the identification of Legionella species.

There are currently more than 40 species of Legionella and the identification of most of these by standard methods is technically difficult. The aim of this study was to assess the suitability of a previously published PCR-based method of identifying Legionella spp. Intergenic 16S-23S rDNA spacer regions were amplified with primers complementary to conserved regions of the rRNA genes. Following electrophoretic separation of the products, data analyses were performed with the Taxotron software package. Computer-assisted analysis (with an empirically derived error tolerance of 3%) could differentiate only 26 of the 43 strains (representing 43 species), with the remaining 17 species clustering into four groups (group I, comprising 10 species; group II, three species; group III, two species and group IV, two species). Analysis of well-characterised 'non-type' strains of some Legionella spp. (e.g., from type culture collections) resulted in patterns distinct from the corresponding type strain in most cases. Furthermore, recent isolates (identified by conventional methods) were identified by this PCR method to the presumed correct species (or species group) in only a minority of cases. Well characterised strains and recent isolates of Legionella showed heterogeneity within many species. This intra-species variation severely limits the usefulness of the method for the identification of isolates. However, this property may be useful for epidemiological typing within such species.

Random amplified polymorphic DNA and amplified ribosomal DNA spacer polymorphism: powerful methods to differentiate Streptococcus thermophilus strains.

Streptococci from different collections and dairy materials were characterized by conventional and molecular methods. After amplification of the 16S-23S rDNA spacer region, all the strains referable to the genus Streptococcus exhibited a single polymerase chain reaction (PCR) product, allowing their differentiation from enterococci. Cleaving this PCR product with Hae III, two different restriction patterns could be observed, allowing Streptococcus salivarius DSM 20560T, Strep. thermophilus NCDO 822 and two strains of Streptococcus spp. to be gathered in one group and all the other strains in another. In order to achieve strain typing, all the cultures were investigated by random amplified polymorphic DNA (RAPD)-PCR analysis employing two selected primers. The results were treated by cluster analysis, appearing significantly consistent with both the taxonomic position and the origin of the strains. Pulsed-field gel electrophoresis (PFGE) of Sma I digests of the genomic DNA from 11 representative strains with decreasing levels of RAPD similarity allowed their diversity to be confirmed, even though RAPD-PCR proved to be less discriminating than PFGE analysis. The results are discussed with reference to the capability of the analytical procedures used to aid both identification and strain typing of streptococci, as well as the taxonomic structure of the species Strep. thermophilus.

Genomic Diversity of Several Corynebacterium Species Identified by Amplification of the 16S–23S rRNA Gene Spacer Regions

In order to investigate whether 16S–23S ribosomal DNA (rDNA) spacer region length polymorphisms are suitable identification of Corynebacterium strains at the species level, the 16S–23S rDNA intergenic spacer region strains belonging to 11 Corynebacterium species were studied by a PCR-based method. The lengths 16S–23S rDNA spacer regions varied from 394 to 585 bp, fragment lengths which are similar to those described for other genera. A single PCR profile was obtained for each of the following species: Corynebacterium renale, Corynebacterium urealyticum, Corynebacterium diphtheriae, Corynebacterium ulcerans, Corynebacterium pseudodiphtheriticum, and Corynebacterium kutscheri. In contrast, two and three PCR patterns were detected for Corynebacterium minutissimum, Corynebacterium striatum, Corynebacterium amycolatum, and Corynebacterium jeikeium, suggesting that genomic heterogeneity occurs in these four species. The 16S–23S rDNA spacer region length polymorphisms allowed us to discriminate among C. minutissimum, C. striatum, and C. amycolatum, three species that are frequently isolated and misidentified in clinical laboratories. Type strain Corynebacterium xerosis ATCC 373, which exhibited a PCR pattern similar to that of C. amycolatum strains classified in PCR group I, could nevertheless be discriminated from PCR group II (C. amycolatum) strains, as Well as minutissimum and C. striatum strains. Type strain C. xerosis ATCC 373 and C. amycolatum strains classified PCR group I could not be distinguished from strains belonging to C. diphtheriae, C. ulcerans, and C. pseudodiphtheriticum. The lipophilic species C. urealyticum and C. jeikeium, which are frequently encountered in clinical specimens, could be clearly distinguished from each other by this method. The use of 16S–23S spacer region length data determined by PCR-mediated amplification is suitable for identification of several Corynebacterium species. This rapid and easy method may be a useful identification tool for clinical microbiologists.

Specific Detection of Burkholderia plantarii and B. glumae by PCR Using Primers Selected from the 16S-23S rDNA Spacer Regions.

Specific Detection of Burkholderia plantarii and B. glumae by PCR Using Primers Selected from the 16S-23S rDNA Spacer Regions.

New approaches to typing and identification of bacteria using the 16S-23S rDNA spacer region.

New approaches to typing and identification of bacteria using the 16S-23S rDNA spacer region.

Typing of Staphylococcus aureus strains by PCR-amplification of variable-length 16S-23S rDNA spacer regions: characterization of spacer sequences

To develop a rapid and accurate method of typing large numbers of clinical isolates of Staphylococcus aureus, the spacer region C of the rRNA operon [1391-507 (16S-23S)] was enzymically amplified from 322 strains. When the products were separated by denaturing PAGE, 15 variable-length rrn alleles were demonstrated, ranging in size from 906 to 1223 bp. The variable-length HpaII-digested region C [(region E; 1446-196 (16S-23S)] amplification products were cloned into M13mp18RF to sequence separate variable-length alleles. A total of 17 region E inserts were sequenced, aligned and divided into nine alleles by length (938-1174) and sequence properties. The 16S-23S spacer rDNA varied in length (303-551 bp) and in properties; three alleles contained a tRNAIle gene alone, two alleles contained a tRNAIle and a tRNAAla gene, and four alleles lacked tRNA genes. The sequences of two alleles showed less than 1% variation when isolated from two or three S. aureus strains. The 48 penicillin- and methicillin-sensitive strains were divided into 26 ribotypes; in contrast, the 274 methicillin-resistant S. aureus (MRSA) strains were divided into nine ribotypes (A-I) with 97% typing as either ribotype A or B (rrnL was missing in B). The sequence conservation of the rrn operons argues for the use of the 16S-23S spacer region as a stable and direct indicator of the evolutionary divergence of S. aureus strains.

Typing of Clostridium difficile strains by PCR-amplification of variable length 16S-23S rDNA spacer regions.

To develop a rapid and accurate method of typing large numbers of clinical isolates of Clostridium difficile, four regions of the rRNA operon [A, 15-1407 and B, 907-1407 (16S-16S); C, 1392-507 and D, 907-507 (16S-23S)] were enzymically amplified from 24 strains. When region A was hybridized to HindIII-digested genomic DNA isolated from C. difficile strains, all of the variable length restriction fragments hybridized. When region B was hybridized to HindIII-digested genomic DNA isolated from C. difficile strains, a set of variable length restriction fragments (Group II) hybridized predominantly. When region C was separated by agarose gel electrophoresis, a series of products ranging in size from approximately 800-1300 bp was obtained. When regions C and D were digested with HindIII, a constant region of 430 bp was found in both products and in all strains. From the above experiments it was concluded that the variable length Group II restriction fragments and the variable length region C amplification products were due to variable length 16S-23S spacer regions between alleles of the one strain. When region C amplification products were separated by denaturing PAGE, 16 variable length rRNA alleles (rrnA-P) were demonstrated from 24 C. difficile strains ranging in size from 852-1210 bp. After analysis with maximum parsimony, the 24 strains were divided into 14 ribotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid identification of bacteria of the Comamonadaceae with amplified ribosomal DNA-restriction analysis (ARDRA)

Ribosomal rRNA gene fragments (rDNA) encompassing the 16S rDNA, the 16S-23S rDNA spacer region and part of the 23S rDNA of 95 strains belonging to 13 well-described taxa of the eubacterial family comamonadaceae (β subclass of the Proteobacteria or rRNA superfamily III) were enzymatically amplified using conserved primers. The fragments of approximately 2400 base pairs were subjected to restriction analysis. Restriction fragment length patterns obtained with HinfI enabled us to distinguish 9 of the 13 taxa studied. Restriction with CfoI was necessary to differentiate Acidovorax delafieldii from A. temperans and Hydrogenophaga flava from H. pseudoflava. The results indicate that amplified rDNA restriction analysis is a simple and reliable tool for the identification of bacterial species.