Species-Specific Difference in Antimicrobial Susceptibility Among Viridans Group Streptococci

Chun, Sejong; Huh, Hee Jae; Lee, Nam Yong

doi:10.3343/alm.2015.35.2.205

Cited by 43 publications

(39 citation statements)

References 23 publications

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“…Although antimicrobial resistance is an increasing problem with many bacterial groups (43,44), SAG remain susceptible to most antibiotic classes, as was observed in the present study. The only significant resistance found was to clindamycin, erythromycin, and tetracycline.…”

Section: Discussionsupporting

confidence: 70%

Comparing Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry and Phenotypic and Molecular Methods for Identification of Species within the Streptococcus anginosus Group

et al. 2015

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The heterogeneity of members of the Streptococcus anginosus group (SAG) has traditionally hampered their correct identification. Recently, the group was subdivided into 6 taxa whose prevalence among human infections is poorly described. We evaluated the accuracy of the Rapid ID32 Strep test, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and a PCR multiplex method to identify 212 SAG isolates recovered from human infections to the species and subspecies level by using multilocus sequence analysis (MLSA) as the gold standard. We also determined the antimicrobial susceptibilities of the isolates. Representatives of all SAG taxa were found among our collection. MALDI-TOF MS and the Rapid ID32 Strep test correctly identified 92% and 68% of the isolates to the species level, respectively, but showed poor performance at the subspecies level, and the latter was responsible for major identification errors. The multiplex PCR method results were in complete agreement with the MLSA identifications but failed to distinguish the subspecies Streptococcus constellatus subsp. pharyngis and S. constellatus subsp. viborgensis. A total of 145 MLSA sequence types were present in our collection, indicating that within each taxon a number of different lineages are capable of causing infection. Significant antibiotic resistance was observed only to tetracycline, erythromycin, and clindamycin and was present in most taxa. MALDI-TOF MS is a reliable method for routine SAG species identification, while the need for identification to the subspecies level is not clearly established. Initially included in the viridans group streptococci, the species now recognized as the Streptococcus anginosus group (SAG) were first described as Streptococcus milleri in 1956 (1), but their taxonomic classification has remained in flux. Currently, the group includes three species, Streptococcus anginosus, Streptococcus constellatus, and Streptococcus intermedius (2-5) with unique genome signature regions (5). The species S. constellatus was subdivided into the subspecies S. constellatus subsp. pharyngis and S. constellatus subsp. constellatus (6). Recently, Jensen et al., based on multilocus sequence analysis (MLSA), divided S. anginosus into two subspecies-S. anginosus subsp. anginosus (the isolates formerly classified as S. anginosus) and S. anginosus subsp. whileyi-and they described the novel subspecies S. constellatus subsp. viborgensis (7).Most SAG strains share common features, such as small colony size, low growth rate, and a distinctive caramel smell (8, 9). However, SAG also present diversity in their other characteristics. These organisms may be nonhemolytic or display beta-or alphahemolysis when grown on blood agar plates (4, 5, 10), and they may present any of the A, C, F, or G Lancefield group antigens or lack Lancefield group antigen altogether (4,5,8,10). SAG, as with other members of the viridans group streptococci, are part of the human microbiota, colonizing the oral cavity, nasopharynx, and g...

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Section: Discussionsupporting

confidence: 70%

Comparing Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry and Phenotypic and Molecular Methods for Identification of Species within the Streptococcus anginosus Group

et al. 2015

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“…mitis and S. oralis are major causative agents of VGS bacteremia and IE (6–9). Although these organisms are unquestionably significant for human health, very little is known about the physiology and virulence of S.…”

Section: Introductionmentioning

confidence: 99%

Streptococcus mitis and S. oralis Lack a Requirement for CdsA, the Enzyme Required for Synthesis of Major Membrane Phospholipids in Bacteria

Adams

Joyce

Guan

et al. 2017

Antimicrob Agents Chemother

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Synthesis and integrity of the cytoplasmic membrane are fundamental to cellular life. Experimental evolution studies have hinted at unique physiology in the Gram-positive bacteria Streptococcus mitis and S. oralis. These organisms commonly cause bacteremia and infectious endocarditis (IE) but are rarely investigated in mechanistic studies of physiology and evolution. Unlike in other Gram-positive pathogens, high-level (MIC ≥ 256 μg/ml) daptomycin resistance rapidly emerges in S. mitis and S. oralis after a single drug exposure. In this study, we found that inactivating mutations in cdsA are associated with high-level daptomycin resistance in S. mitis and S. oralis IE isolates. This is surprising given that cdsA is an essential gene for life in commonly studied model organisms. CdsA is the enzyme responsible for the synthesis of CDP-diacylglycerol, a key intermediate for the biosynthesis of all major phospholipids in prokaryotes and most anionic phospholipids in eukaryotes. Lipidomic analysis by liquid chromatography-mass spectrometry (LC-MS) showed that daptomycin-resistant strains have an accumulation of phosphatidic acid and completely lack phosphatidylglycerol and cardiolipin, two major anionic phospholipids in wild-type strains, confirming the loss of function of CdsA in the daptomycin-resistant strains. To our knowledge, these daptomycin-resistant streptococci represent the first model organisms whose viability is CdsA independent. The distinct membrane compositions resulting from the inactivation of cdsA not only provide novel insights into the mechanisms of daptomycin resistance but also offer unique opportunities to study the physiological functions of major anionic phospholipids in bacteria.

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“…Penicillin resistance is rare [13][14][15]. According to a recent study, penicillin is proved to be an effective antimi- [16]. The recent increase in MICs to penicillin G suggests that initiation of penicillin G combined with gentamicin may be prudent.…”

Section: Discussionmentioning

confidence: 99%

Unusual Presentation of Streptococcus anginosus With Severe Sepsis, Liver Abscess Secondary to Biliary Tract Perforation

et al. 2015

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Species-Specific Difference in Antimicrobial Susceptibility Among Viridans Group Streptococci

Cited by 43 publications

References 23 publications

Comparing Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry and Phenotypic and Molecular Methods for Identification of Species within the Streptococcus anginosus Group

Comparing Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry and Phenotypic and Molecular Methods for Identification of Species within the Streptococcus anginosus Group

Streptococcus mitis and S. oralis Lack a Requirement for CdsA, the Enzyme Required for Synthesis of Major Membrane Phospholipids in Bacteria

Unusual Presentation of Streptococcus anginosus With Severe Sepsis, Liver Abscess Secondary to Biliary Tract Perforation

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