Species-level assessment of the molecular basis of fluoroquinolone resistance among viridans group streptococci causing bacteraemia in cancer patients

Sahasrabhojane, Pranoti; Galloway-Peña, Jessica; Velázquez, Luís; Saldaña, Miguel A.; Horstmann, Nicola; Tarrand, Jeffrey J.; Shelburne, Samuel A.

doi:10.1016/j.ijantimicag.2014.01.031

Cited by 15 publications

(14 citation statements)

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“…Thus, for our invasive VGS isolates, the analysis of the partial GyrB sequence correctly identified species. Furthermore, although we had previously shown that 79/102 of our strains were fluoroquinolone nonsusceptible, none of the strains had determinative polymorphisms in the GyrB QRDR (32). Therefore, in our cohort of invasive VGS strains, fluoroquinolone resistance does not influence the ability of the GyrB sequence to distinguish VGS species (32).…”

Section: Resultsmentioning

confidence: 60%

“…3, we offer a workflow for VGS species identification that can be used in either a research or clinical setting. Importantly, although gyrB encodes part of DNA gyrase, which is a target of fluoroquinolones, polymorphisms in GyrB are not a major mechanism by which VGS strains develop fluoroquinolone resistance (32,36). Therefore, fluoroquinolone resistance does not influence the ability of GyrB to assign VGS strains to a particular species.…”

Section: Discussionmentioning

confidence: 99%

“…VGS species determination was performed using the gold standard approach of MLSA, as described by Bishop et al (3). We previously determined the specific species identities of the 102 VGS isolates from cancer patients in a separate study (32).…”

Section: Methodsmentioning

confidence: 99%

“…In a previous work, we sequenced the quinolone resistancedetermining regions (QRDRs) of four genes (gyrA, gyrB, parC, and parE) in order to better understand the molecular basis for fluoroquinolone resistance in VGS causing bacteremia in cancer patients (32). We noted that an amino acid change in GyrB seemed to distinguish S. oralis strains from S. mitis strains (32).…”

mentioning

confidence: 99%

“…We noted that an amino acid change in GyrB seemed to distinguish S. oralis strains from S. mitis strains (32). In this study, we performed systematic analyses of 102 unique VGS bloodstream isolates, using the gyrB nucleotide and amino acid sequences, in an attempt to categorize them into individual species.…”

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confidence: 99%

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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: Resultsmentioning

confidence: 60%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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