<i>Streptococcus mitis</i>Strains Causing Severe Clinical Disease in Cancer Patients

Shelburne, Samuel A.; Sahasrabhojane, Pranoti; Saldaña, Miguel A.; Yao, Hui; Su, Xiaoping; Horstmann, Nicola; Thompson, Erika J.; Flores, Anthony R.

doi:10.3201/eid2005.130953

Cited by 122 publications

(115 citation statements)

References 38 publications

(60 reference statements)

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“…The recent development of accurate VGS species assignment using the seven-gene MLSA has already augmented the understanding of clinical correlations with VGS species assignment (5,6,39). Thus, having a practical and effective means for both research and clinical microbiology laboratories to assign VGS strains to particular species is becoming increasingly imperative.…”

Section: Discussionmentioning

confidence: 99%

“…Second, for relatively rare VGS species, such as S. infantis, S. constellatus, and S. australis, the low number of strains available for analysis means that additional strains will need to be tested to confirm our findings. Of note, although mutans group isolates are classically considered viridans group streptococci, they are not common causes of invasive disease and thus were not considered in these analyses (3,5,6). …”

Section: Discussionmentioning

confidence: 99%

“…Accurate species identification is pertinent not only for epidemiological purposes but has potential implications for the clinical management of VGS infections. For example, recent studies show that Streptococcus mitis strains cause a higher incidence of severe clinical disease and have higher rates of resistance to penicillin and fluoroquinolones than do other VGS species (2,(4)(5)(6). Additionally, other VGS species have predilections to cause distinct types of infections, such as endocarditis by Streptococcus sanguinis and gastrointestinal infections by Streptococcus anginosus (2,6).…”

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GyrB Polymorphisms Accurately Assign Invasive Viridans Group Streptococcal Species

et al. 2014

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Viridans group streptococci (VGS) are a heterogeneous group of medically important bacteria that cannot be accurately assigned to a particular species using conventional phenotypic methods. Although multilocus sequence analysis (MLSA) is considered the gold standard for VGS species-level identification, MLSA is not yet feasible in the clinical setting. Conversely, molecular methods, such as sodA and 16S rRNA gene sequencing, are clinically practical but not sufficiently accurate for VGS species-level identification. Here, we present data regarding the use of an ϳ400-nucleotide internal fragment of the gene encoding DNA gyrase subunit B (GyrB) for VGS species-level identification. MLSA, internal gyrB, sodA, full-length, and 5= 16S gene sequences were used to characterize 102 unique VGS blood isolates collected from 2011 to 2012. When using the MLSA species assignment as a reference, full-length and 5= partial 16S gene and sodA sequence analyses failed to correctly assign all strains to a species. Precise species determination was particularly problematic for Streptococcus mitis and Streptococcus oralis isolates. However, the internal gyrB fragment allowed for accurate species designations for all 102 strains. We validated these findings using 54 VGS strains for which MLSA, 16S gene, sodA, and gyrB data are available at the NCBI, showing that gyrB is superior to 16S gene and sodA sequence analyses for VGS species identification. We also observed that specific polymorphisms in the 133-amino acid sequence of the internal GyrB fragment can be used to identify invasive VGS species. Thus, the GyrB amino acid sequence may offer a more practical and accurate method for classifying invasive VGS strains to the species level.V iridans group streptococci (VGS) are a genetically heterogeneous group of commensal bacteria that cause a wide range of infections in humans, particularly in persons with hematologic disease or neutropenia as a result of chemotherapy (1, 2). Although Ͼ25 VGS species have been described, rapid and reliable identification to the species level eludes this group of organisms (3, 4). Accurate species identification is pertinent not only for epidemiological purposes but has potential implications for the clinical management of VGS infections. For example, recent studies show that Streptococcus mitis strains cause a higher incidence of severe clinical disease and have higher rates of resistance to penicillin and fluoroquinolones than do other VGS species (2, 4-6). Additionally, other VGS species have predilections to cause distinct types of infections, such as endocarditis by Streptococcus sanguinis and gastrointestinal infections by Streptococcus anginosus (2, 6).Routine tests and commercial kits used in clinical practice based on the phenotypic and biochemical traits of individual species, such as API Rapid ID32 Strep, Vitek 2, and Streptogram, have only a 30% to 80% accuracy rate for VGS, depending on the species (7-10). The inherent problems with these approaches lie in the variability of traits within V...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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GyrB Polymorphisms Accurately Assign Invasive Viridans Group Streptococcal Species

et al. 2014

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“…The GenBank accession number for the SGBS001 genome is CP010867. Of the remaining 208 ST-1 strains, whole-genome sequencing of 201 GBS strains (seven random strains were not sequenced for multiplexing convenience reasons) was performed by using Illumina HiSeq or MiSeq instruments with an average sequencing depth of 120× (38). Sequence data for the 208 genomes have been deposited in the NCBI Short Read Archive database (BioProject PRJNA274384).…”

Section: Methodsmentioning

confidence: 99%

Sequence type 1 group B Streptococcus , an emerging cause of invasive disease in adults, evolves by small genetic changes

Galloway-Peña

Sahasrabhojane

Saldaña

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The molecular mechanisms underlying pathogen emergence in humans is a critical but poorly understood area of microbiologic investigation. Serotype V group B Streptococcus (GBS) was first isolated from humans in 1975, and rates of invasive serotype V GBS disease significantly increased starting in the early 1990s. We found that 210 of 229 serotype V GBS strains (92%) isolated from the bloodstream of nonpregnant adults in the United States and Canada between 1992 and 2013 were multilocus sequence type (ST) 1. Elucidation of the complete genome of a 1992 ST-1 strain revealed that this strain had the highest homology with a GBS strain causing cow mastitis and that the 1992 ST-1 strain differed from serotype V strains isolated in the late 1970s by acquisition of cell surface proteins and antimicrobial resistance determinants. Whole-genome comparison of 202 invasive ST-1 strains detected significant recombination in only eight strains. The remaining 194 strains differed by an average of 97 SNPs. Phylogenetic analysis revealed a temporally dependent mode of genetic diversification consistent with the emergence in the 1990s of ST-1 GBS as major agents of human disease. Thirty-one loci were identified as being under positive selective pressure, and mutations at loci encoding polysaccharide capsule production proteins, regulators of pilus expression, and two-component gene regulatory systems were shown to affect the bacterial phenotype. These data reveal that phenotypic diversity among ST-1 GBS is mainly driven by small genetic changes rather than extensive recombination, thereby extending knowledge into how pathogens adapt to humans.Streptococcus agalactiae | pathogenesis | evolution | single nucleotide polymorphisms | surface protein

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“…A mong the viridans group streptococci, the members of the Streptococcus mitis group are the most frequent cause of human infective endocarditis (IE) and the most common cause of the toxic streptococcal bacteremia syndrome seen in immunocompromised hosts (1)(2)(3)(4)(5)(6)(7)(8). This organism is often resistant in vitro to ␤-lactam antibiotics, including penicillin and ceftriaxone (9)(10)(11)(12)(13)(14)(15)(16).…”

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confidence: 99%

Impact of High-Level Daptomycin Resistance in the Streptococcus mitis Group on Virulence and Survivability during Daptomycin Treatment in Experimental Infective Endocarditis

García-de-la-Mària

Xiong

Pericàs

et al. 2017

Antimicrob Agents Chemother

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Among the viridans group streptococci, the Streptococcus mitis group is the most common cause of infective endocarditis. These bacteria have a propensity to be ␤-lactam resistant, as well as to rapidly develop high-level and durable resistance to daptomycin (DAP). We compared a parental, daptomycin-susceptible (DAP s ) S. mitis/S. oralis strain and its daptomycin-resistant (DAP r ) variant in a model of experimental endocarditis in terms of (i) their relative fitness in multiple target organs in this model (vegetations, kidneys, spleen) when animals were challenged individually and in a coinfection strategy and (ii) their survivability during therapy with daptomycin-gentamicin (an in vitro combination synergistic against the parental strain). The DAP r variant was initially isolated from the cardiac vegetations of animals with experimental endocarditis caused by the parental DAP s strain following treatment with daptomycin. The parental strain and the DAP r variant were comparably virulent when animals were individually challenged. In contrast, in the coinfection model without daptomycin therapy, at both the 10 6 -and 10 7 -CFU/ml challenge inocula, the parental strain outcompeted the DAP r variant in all target organs, especially the kidneys and spleen. When the animals in the coinfection model of endocarditis were treated with DAP-gentamicin, the DAP s strain was completely eliminated, while the DAP r variant persisted in all target tissues. These data underscore that the acquisition of DAP r in S. mitis/S. oralis does come at an intrinsic fitness cost, although this resistance phenotype is completely protective against therapy with a potentially synergistic DAP regimen.

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Streptococcus mitisStrains Causing Severe Clinical Disease in Cancer Patients

Cited by 122 publications

References 38 publications

GyrB Polymorphisms Accurately Assign Invasive Viridans Group Streptococcal Species

GyrB Polymorphisms Accurately Assign Invasive Viridans Group Streptococcal Species

Sequence type 1 group B Streptococcus , an emerging cause of invasive disease in adults, evolves by small genetic changes

Impact of High-Level Daptomycin Resistance in the Streptococcus mitis Group on Virulence and Survivability during Daptomycin Treatment in Experimental Infective Endocarditis

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