Streptococcus gallolyticus is often found as a normal member of the gut microflora of various animals, while it has been reported to cause mastitis in cattle, septicemia in pigeons, and meningitis, sepsis, and endocarditis in humans (2). The species, which includes strains formerly identified as Streptococcus bovis biotye I and S. bovis biotype II/2, can be distinguished from other related taxa or biotypes (i.e., Streptococcus equinus and S. bovis biotype II/1) based on the results of DNA-DNA reassociation experiments (3). Recently, Schlegel et al. (6) demonstrated that S. gallolyticus, S. bovis biotype II/2, Streptococcus macedonicus, and Streptococcus waius form a single DNA cluster and thus proposed S. gallolyticus subsp. gallolyticus subsp. nov., S. gallolyticus subsp. macedonicus subsp. nov., and S. gallolyticus subsp. pasteurianus subsp. nov. within this species.
Meanwhile, Poyart et al. (4) demonstrated that a partial sequence of the manganese-dependent superoxide dismutase gene (sodA) provides a useful approach for species differentiation within the so-called S. bovis-Streptococcus equinus group. Consequently, Sasaki et al. (5) has developed a novel PCR-based assay targeting a partial sequence of S. gallolyticus specific sodA for species identification. We therefore performed this PCR assay on type or reference strains of the three subspecies of S. gallolyticus and closely related species, including S. equinus and Streptococcus infantarius. As shown in Table 1, the species-specific PCR product was only detected in the three subspecies, supporting the view of Schlegel et al. (6) that these subspecies forms a distinct single taxon at the species level.
TABLE 1.
Genotypic and metabolic characteristics of strains belonging to three subspecies of S. gallolyticus and its closely related species
| Strain designationa | Former classification | S. gallolyticus species specific sodA targeted PCR productb | Aromatic acid metabolizedc
|
|||||
|---|---|---|---|---|---|---|---|---|
| Tannic | Gallic | Protocatechuic | p-Coumaric | Caffeic | Ferulic | |||
| S. gallolyticus subsp. gallolyticus | ||||||||
| ACM 3611T (HDP 99204T) | S. gallolyticus type strain | + | + | + | + | + | + | + |
| ACM 3546 (NCDO2019) | S. bovis biotype I | + | + | + | + | + | + | + |
| ACM 3902 (CDC002) | S. bovis biotype I | + | + | + | + | + | + | + |
| S. gallolyticus subsp. macedonicus | ||||||||
| HDP 98362r (ACA-DC 206r) | S. macedonicus type strain | + | − | − | − | + | + | − |
| HDP 99050 (ACA-DC 207) | S. macedonicus | + | − | − | − | + | + | − |
| HDP 99422 (NZRCC 20100) | S. waius type strain | + | − | − | − | + | + | − |
| S. gallolyticus subsp. pasteurianus | ||||||||
| HDP 90084 (Api 79.04.159) | S. bovis biotype II/2 | + | − | + | + | + | + | + |
| ACM 3870 (CDC1723-81) | S. bovis biotype II/2 | + | − | + | + | + | + | + |
| ACM 3869 (CDC2266-81) | S. bovis biotype II/2 | + | − | + | + | + | + | + |
| S. infantarius subsp. infantarius | ||||||||
| HDP 90056T (NCDO 599T) | − | − | − | − | − | − | − | |
| HDP 90104 | − | − | − | − | − | − | − | |
| S. infantarius subsp. coli | ||||||||
| HDP 90246T (NCDO946T) | − | − | − | − | − | − | − | |
| S. equinus | ||||||||
| ACM 3541T(NCDO1037T) | − | − | − | − | − | − | − | |
| ACM 3544 (NCDO2445) | − | − | − | − | − | − | − | |
| ACM 3545 (NCDO2446) | − | − | − | − | − | − | − | |
| ACM 3539 (NCDO597) | S. bovis type strain biotype II/1 | − | − | − | − | − | − | − |
| ACM 3540 (NCDO598) | S. bovis biotype II/1 | − | − | − | − | − | − | − |
| ACM 3542 (NCDO1251) | S. bovis biotype II/1 | − | − | − | − | − | − | − |
| ACM 3543 (NCDO2128) | S. bovis biotype II/1 | − | − | − | − | − | − | − |
HPD strains were generously gifted from A. Bouvet of Centre National de Référence des Streptocoques, Service de Microbiologie, Université Paris VI; Paris, France. Culture collection: ACA-DC, Culture Collection of the Laboratory of Dairy Research, Agricultural University of Athens, Athens Greece; ACM, Australian Collection of Microorganisms, University of Queensland, Brisbane, Australia; Api, AP1-bioMérieux Collection, La Balme-les-Grottes, France; CDC, Centers for Disease Control, Atlanta, Ga.; HDP, Centre National de Référence des Streptocoques, Service de Microbiologie, Université Paris VI, Paris, France; NCDO, National Collection of Dairy Organisms, Reading, United Kingdom; NZRCC, New Zealand Reference Culture Collection, Palmerston North, New Zealand.
Following the methodology of PCR described by Sasaki et al. (5).
Most, if not all, of the strains belonging to S. gallolyticus are able to decarboxylate gallate as well as produce tannase, by which a hydrolyzable tannin (i.e., gallotannin) is hydrolyzed to release gallic acid, which is subsequently decarboxylated to pyrogallol (3). Recently, Chamkha et al. (1) demonstrated that S. gallolyticus ACM 3611T also decarboxylated other aromatic compounds, including protocatechuic acid, p-coumaric acid, caffeic acid, and ferulic acid. In this context, we examined the metabolism of these phenolic acids by type strains of the three subspecies of S. gallolyticus, their respective reference strains, and closely related species, including S. equinus and S. infantarius. Tannase and gallate-decarboxylating activities of the strains were determined by the methodology described previously (3). Metabolism of protocatechuic, p-coumaric, caffeic, and ferulic acids by the strains were detected spectrophotometrically, as described by Chamkha et al. (1). Our results showed that all S. gallolyticus strains tested, inclusive of the three subspecies strains, decarboxylated p-coumaric acid and caffeic acid, while the closely related species did not decarboxylate any of the substrates (Table 1). It should also be noted that the strains belonging to S. gallolyticus subsp. macedonicus did not decarboxylate either protocatechuic acid or ferulic acid, which may prove to be useful phenotypic characteristics for identification at the subspecies level.
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