Comparison of species identification of endocarditis associated viridans streptococci using rnpB genotyping and 2 MALDI-TOF systems

Isaksson, Jenny; Rasmussen, Magnus; Nilson, Bo; Stadler, Liselott Svensson; Kurland, Siri; Olaison, Lars; Ek, Elisabeth; Herrmann, Björn

doi:10.1016/j.diagmicrobio.2014.12.007

Cited by 51 publications

(43 citation statements)

References 30 publications

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“…The overall prevalence of S. tigurinus was 53% in 51 patients and there was no difference in the frequencies of detection between the two groups (21). MALDI-TOF MS misidentifies S. tigurinus as Streptococcus oralis, Streptococcus pneumoniae, or other member of the mitis group with scores Ͼ2.0 (16,19,22). Identification requires the use of 16S rRNA partial or full-gene sequencing or other molecular methods (21).…”

Section: Gram-positive Coccimentioning

confidence: 99%

What's in a Name? New Bacterial Species and Changes to Taxonomic Status from 2012 through 2015

Munson

Carroll

2017

J Clin Microbiol

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Technological advancements in fields such as molecular genetics and the human microbiome have resulted in an unprecedented recognition of new bacterial genus/species designations by the International Journal of Systematic and Evolutionary Microbiology. Knowledge of designations involving clinically significant bacterial species would benefit clinical microbiologists in the context of emerging pathogens, performance of accurate organism identification, and antimicrobial susceptibility testing. In anticipation of subsequent taxonomic changes being compiled by the Journal of Clinical Microbiology on a biannual basis, this compendium summarizes novel species and taxonomic revisions specific to bacteria derived from human clinical specimens from the calendar years 2012 through 2015.KEYWORDS anaerobes, bacteria, Gram-negative bacteria, Gram-positive bacteria, taxonomy H uman microbiome studies, particularly those involving genome sequencing, have resulted in a seeming explosion of novel bacterial taxonomy. While many of these organisms appear to play a commensal role in site-specific ecology, some of the organisms may be of clinical significance in various patient populations. Moreover, enhanced studies of known bacterial genomes in a variety of applications, including those of an epidemiologic nature, have given rise to revisions and amendments to accepted bacterial taxonomy. Summaries of microbial taxonomy updates, such as those introduced in this edition of the Journal of Clinical Microbiology, are essential to routine practice in the clinical microbiology laboratory.Since 2014, laboratories subscribing to the College of American Pathologists accreditation program have encountered checklist standard MIC.11375 in the context of biennial inspection exercises. The standard (1) requires laboratories to assimilate "taxonomic changes that potentially affect the choice of appropriate antimicrobials to report and/or the interpretative breakpoints to use." Cited as an example for the context of this standard is the Gram-negative bacillus with the former taxonomic designation Actinobacillus actinomycetemcomitans. The taxonomic revision in 1985 (2) resulting in organism classification within the genus Haemophilus subsequently enabled antimicrobial susceptibility testing of clinically significant isolates using standards outlined in Table 2E of CLSI supplement M100S (example provided in [3]). Haemophilus test medium, with a 16-to 18-hour incubation in 5% CO 2 enrichment, could be utilized for disk diffusion. Haemophilus test medium broth could also be inoculated for broth microdilution testing with 20-to 24-hour incubation in ambient air.Subsequent reclassification of this organism into the genus Aggregatibacter (4) has resulted in the transition of susceptibility testing guidelines to those specific to (former) HACEK group organisms (Aggregatibacter spp., Cardiobacterium spp., Eikenella corrodens, and Kingella spp.) in Table 9 of the CLSI guideline M45 (5).

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Section: Gram-positive Coccimentioning

confidence: 99%

What's in a Name? New Bacterial Species and Changes to Taxonomic Status from 2012 through 2015

Munson

Carroll

2017

J Clin Microbiol

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“…MALDI-TOF MS was also used to identify each isolate. As spectra for S. tigurinus are not in the Bruker or the Vitek MS databases (13), the Bruker MALDI-TOF MS misidentified all of the isolates tested, usually as Streptococcus oralis ( Table 1).…”

Section: Resultsmentioning

confidence: 99%

“…S. tigurinus is not contained in the database for the Vitek 2 microbial identification system. As S. tigurinus spectra are not present in either of the currently available Biotyper (Bruker) or Vitek MS (bioMérieux) databases, S. tigurinus is not reliably identified by the most commonly used MALDI-TOF MS systems at this time (13). Currently, sequencing methods must be used to successfully identify S. tigurinus.…”

Section: Discussionmentioning

confidence: 99%

Clinical Significance and Characterization of Streptococcus tigurinus Isolates in an Adult Population

Bourassa

Clarridge

2015

J Clin Microbiol

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Streptococcus tigurinus is a newly described member of the Streptococcus mitis group. Due to the difficulty in distinguishing viridans group streptococci (VGS) by phenotype, analysis of 16S rRNA sequences is necessary for the accurate identification of most species. Through a laboratory policy of analyzing all clinically significant isolates from the VGS group by16S rRNA gene sequencing, we identified 14 S. tigurinus isolates from 11 patients. The Vitek 2 system most commonly gave an excellent rating to an incorrect identification (e.g., Streptococcus mitis), as did matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (e.g., Streptococcus oralis). S. tigurinus strains were recovered from numerous body sites, including the blood, peritoneal fluid, bone, synovial fluid, a perianal abscess, and an arm wound. Retrospective chart review indicated that most isolates were clinically significant, with bacteremia (n ‫؍‬ 5), soft tissue infections (n ‫؍‬ 3) osteomyelitis (n ‫؍‬ 2), infected joint prosthesis (n ‫؍‬ 2), and peritonitis (n ‫؍‬ 2) being the most common, thus expanding the spectrum of disease associated with S. tigurinus. Streptococcus tigurinus was first described after isolation from a patient with infective endocarditis. Isolates of alpha-hemolytic, catalase-negative Gram-positive cocci were recovered from multiple blood cultures of a 74-year-old patient. The isolates were initially identified as viridans group streptococci (VGS). However, analysis of 16S rRNA sequences revealed that the isolates were distinct members of the Streptococcus mitis group (SMG) and were closely related to Streptococcus pneumoniae, Streptococcus pseudopneumoniae, Streptococcus mitis, Streptococcus infantis, and Streptococcus oralis (1). This novel Streptococcus strain was named Streptococcus tigurinus. Since the first report of S. tigurinus infection in 2012, S. tigurinus has been isolated from several additional sterile sites, including cerebrospinal fluid, heart valves, and joint fluid (2, 3). It has been associated with serious invasive infections, including infective endocarditis, culture-negative endocarditis, spondylodiscitis, bacteremia, meningitis, prosthetic joint infections, and thoracic empyema (2, 4). Small colony variants of S. tigurinus were associated with a prosthetic joint infection (3). S. tigurinus has also been isolated from the subgingival plaque of a patient with periodontitis (5). In vitro studies have shown S. tigurinus to be highly virulent in a rat model of experimental endocarditis (6).Because of its relatedness to SMG, S. tigurinus has been hypothesized to be a commensal of the human oral cavity. Data to support this hypothesis, however, are conflicting (7). In a screen of saliva specimens from 31 volunteers, S. tigurinus was not identified among the more than 600 strains of alpha-hemolytic bacterial colonies isolated (2). In a second study that used a specific 16S rRNA gene real-time TaqMan PCR assay, however, S. tigurinus was detected in the saliva and subgingiv...

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“…In recent years, the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) technique has emerged as an alternative for clinical microbiology laboratories for the identification of a wide range of bacteria and fungi (33)(34)(35). Identification of S. pneumoniae and VGS by MALDI-TOF MS has been widely studied previously (27,(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49). The close relationship between S. pneumoniae and other S. mitis species group streptococci, especially S. mitis and S. oralis, poses considerable challenges for the reliable distinction between species of these groups by this technique as well.…”

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confidence: 99%

“…Therefore, several other streptococcal genes have been targeted in identification and phylogenetic studies, sometimes using an MLSA approach (17)(18)(19)(20)(21)(22). Some of the most commonly used targets have been housekeeping genes ddl (21,23), groESL (24), rnpB (25)(26)(27), rpoB (28), sodA (29,30), tuf (31), and recA (32). However, currently, MLSA is too time-consuming and expensive to be used routinely in a clinical microbiology laboratory but is a useful tool for taxonomic studies.…”

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confidence: 99%

Improved Differentiation of Streptococcus pneumoniae and Other S. mitis Group Streptococci by MALDI Biotyper Using an Improved MALDI Biotyper Database Content and a Novel Result Interpretation Algorithm

et al. 2017

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Reliable distinction of Streptococcus pneumoniae and viridans group streptococci is important because of the different pathogenic properties of these organisms. Differentiation between S. pneumoniae and closely related Sreptococcus mitis species group streptococci has always been challenging, even when using such modern methods as 16S rRNA gene sequencing or matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. In this study, a novel algorithm combined with an enhanced database was evaluated for differentiation between S. pneumoniae and S. mitis species group streptococci. One hundred one clinical S. mitis species group streptococcal strains and 188 clinical S. pneumoniae strains were identified by both the standard MALDI Biotyper database alone and that combined with a novel algorithm. The database update from 4,613 strains to 5,627 strains drastically improved the differentiation of S. pneumoniae and S. mitis species group streptococci: when the new database version containing 5,627 strains was used, only one of the 101 S. mitis species group isolates was misidentified as S. pneumoniae, whereas 66 of them were misidentified as S. pneumoniae when the earlier 4,613-strain MALDI Biotyper database version was used. The updated MALDI Biotyper database combined with the novel algorithm showed even better performance, producing no misidentifications of the S. mitis species group strains as S. pneumoniae. All S. pneumoniae strains were correctly identified as S. pneumoniae with both the standard MALDI Biotyper database and the standard MALDI Biotyper database combined with the novel algorithm. This new algorithm thus enables reliable differentiation between pneumococci and other S. mitis species group streptococci with the MALDI Biotyper.KEYWORDS MALDI-TOF, Streptococcus pneumoniae, algorithm, mitis group streptococci, phenotypic identification, pneumococcus T raditional classification of streptococci was based on the potential to cause hemolysis on sheep blood agar. The term "viridans" is used to refer to the greenish coloring (alpha-hemolysis) of the medium around the colonies due to partial lysis of red blood cells. Streptococcus pneumoniae, one of the most common causative agents of bacterial meningitis, community-acquired pneumonia, and otitis media, is clinically the most important alpha-hemolytic streptococcus. Because of the different pathogenic potentials of S. pneumoniae and other alpha-hemolytic streptococci, the practical dichotomy in clinical laboratories has been between S. pneumoniae and viridans group

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Comparison of species identification of endocarditis associated viridans streptococci using rnpB genotyping and 2 MALDI-TOF systems

Cited by 51 publications

References 30 publications

What's in a Name? New Bacterial Species and Changes to Taxonomic Status from 2012 through 2015

What's in a Name? New Bacterial Species and Changes to Taxonomic Status from 2012 through 2015

Clinical Significance and Characterization of Streptococcus tigurinus Isolates in an Adult Population

Improved Differentiation of Streptococcus pneumoniae and Other S. mitis Group Streptococci by MALDI Biotyper Using an Improved MALDI Biotyper Database Content and a Novel Result Interpretation Algorithm

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