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Category: Clinical Microbiology
Streptococcus, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816728/9781555814632_Chap20-1.gif /docserver/preview/fulltext/10.1128/9781555816728/9781555814632_Chap20-2.gifAbstract:
This chapter presents the information and the identification schemes which adhere in many aspects to the phenotypic classification system. In a study of the genus Streptococcus based on sequence comparisons of small-subunit (16S) rRNA genes, five species groups of viridans group streptococci were demonstrated in addition to the pyogenic group (beta-hemolytic, large-colony formers. Streptococci can cause infections in humans and in many different animal species including mammals and fish. Reflecting the ongoing changes in the epidemiology of group B streptococcal disease, the highest attack rates were observed in patients less than 1 year and adults greater than 65 years of age. The predominant reservoir for S. dysgalactiae subsp. equisimilis strains is the human host, and transmission usually occurs among humans. A rapid method for the detection of S.pyogenes in pharyngeal specimens is based on a single-stranded chemiluminescent nucleic acid probe assay to identify specific rRNA sequences. It is important to distinguish Streptococcus from Enterococcus prior to L-pyrrolidonyl-β-naphthylamide (PYR) testing, and strains of other related genera may be PYR positive (including the genera Abiotrophia, Aerococcus, Enterococcus, Gemella, and Lactococcus). The VP test can be performed for the identification of beta-hemolytic streptococci. In the majority of cases, typing of streptococci has no immediate clinical or therapeutic consequences. It is most often performed by reference laboratories for the purposes of epidemiologic studies and the evaluation of vaccine efficacy. Determination of streptococcal antibodies is indicated for the diagnosis of poststreptococcal disease.
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Colony morphology of selected streptococci. (A) S. pyogenes strain ATCC12344; (B) clinical isolate of S. agalactiae; (C) clinical isolate of S. dysgalactiae subsp. equisimilis (Lancefield group G); (D) mixed culture of S. anginosus (ATCC12395, open arrow) and clinical isolate of S. dysgalactiae subsp. equisimilis (closed arrow) (note the difference in colony size); (E) clinical isolate of S. pneumoniae (note the central depression of the colonies); (F) clinical isolate of S. pneumoniae (note the mucoid appearance of colonies).
Colony morphology of selected streptococci. (A) S. pyogenes strain ATCC12344; (B) clinical isolate of S. agalactiae; (C) clinical isolate of S. dysgalactiae subsp. equisimilis (Lancefield group G); (D) mixed culture of S. anginosus (ATCC12395, open arrow) and clinical isolate of S. dysgalactiae subsp. equisimilis (closed arrow) (note the difference in colony size); (E) clinical isolate of S. pneumoniae (note the central depression of the colonies); (F) clinical isolate of S. pneumoniae (note the mucoid appearance of colonies).
CAMP factor test. An arrowhead-shaped zone of hemolysis in the zone of the S. aureus beta-hemolysin is shown. (A) Clinical isolate of a weakly beta-hemolytic S. agalactiae strain. (B) Beta-hemolytic S. agalactiae strain O90R. (C) Nonhemolytic S. agalactiae strain R268.
CAMP factor test. An arrowhead-shaped zone of hemolysis in the zone of the S. aureus beta-hemolysin is shown. (A) Clinical isolate of a weakly beta-hemolytic S. agalactiae strain. (B) Beta-hemolytic S. agalactiae strain O90R. (C) Nonhemolytic S. agalactiae strain R268.
Phenotypic characteristics of beta-hemolytic streptococci a
a Symbols and abbreviations: +, positive; −, negative; v, variable.
b S. dysgalactiae subsp. dysgalactiae is alpha-hemolytic on sheep blood agar plates.
c S. equi subsp. zooepidemicus, S. canis, and S. porcinus are primarily animal pathogens that are only rarely isolated from humans.
d Species included in the S. anginosus group can be beta-hemolytic, alpha-hemolytic, or nonhemolytic on sheep blood agar plates.
e Large colony size refers to colonies >0.5 mm after 24 h of incubation, whereas small colony size is <0.5 mm.
f Presence of the enzyme pyrrolidonyl aminopeptidase.
g CAMP factor reaction (cohemolysis in the presence of the Staphylococcus aureus beta-hemolysin)
h Voges-Proskauer test (formation of acetoin from glucose fermentation).
i Parenthetical entries indicate hosts from which the organism is rarely isolated.
Phenotypic characteristics of beta-hemolytic streptococci a
a Symbols and abbreviations: +, positive; −, negative; v, variable.
b S. dysgalactiae subsp. dysgalactiae is alpha-hemolytic on sheep blood agar plates.
c S. equi subsp. zooepidemicus, S. canis, and S. porcinus are primarily animal pathogens that are only rarely isolated from humans.
d Species included in the S. anginosus group can be beta-hemolytic, alpha-hemolytic, or nonhemolytic on sheep blood agar plates.
e Large colony size refers to colonies >0.5 mm after 24 h of incubation, whereas small colony size is <0.5 mm.
f Presence of the enzyme pyrrolidonyl aminopeptidase.
g CAMP factor reaction (cohemolysis in the presence of the Staphylococcus aureus beta-hemolysin)
h Voges-Proskauer test (formation of acetoin from glucose fermentation).
i Parenthetical entries indicate hosts from which the organism is rarely isolated.
Phenotypic characteristics of major streptococcal groups a
a Symbols and abbreviations: +, positive; −, negative; v, variable.
b This group comprises the species S. mitis, S. sanguinis, S. parasanguinis, S. gordonii, S. cristatus, S. oralis, S. infantis, S. peroris, S. australis, S. sinensis, S. orisratti, S. oligofermentans, S. massiliensis. S. sanguinis, S. parasanguinis, S. gordonii, and S. cristatus are arginine hydrolysis positive; other species from the S. mitis group are arginine hydrolysis negative.
c S. anginosus, S. constellatus, and S. intermedius belong to the S. anginosus group.
d The S. mutans group includes S. mutans, S. sobrinus, and the following species rarely isolated from humans: S. criceti, S. ratti, and S. downei.
e The S. salivarius group contains S. salivarius, S. vestibularis, and S. thermophilus. S. salivarius is variable, S. vestibularis is positive, and S. thermophilus is negative for urea hydrolysis.
f The S. bovis group now includes S. equinus, S. gallolyticus, S. infantarius, and S. alactolyticus. S. gallolyticus subsp. gallolyticus is positive for the acidification of mannitol; the other species from the S. bovis group are negative.
Phenotypic characteristics of major streptococcal groups a
a Symbols and abbreviations: +, positive; −, negative; v, variable.
b This group comprises the species S. mitis, S. sanguinis, S. parasanguinis, S. gordonii, S. cristatus, S. oralis, S. infantis, S. peroris, S. australis, S. sinensis, S. orisratti, S. oligofermentans, S. massiliensis. S. sanguinis, S. parasanguinis, S. gordonii, and S. cristatus are arginine hydrolysis positive; other species from the S. mitis group are arginine hydrolysis negative.
c S. anginosus, S. constellatus, and S. intermedius belong to the S. anginosus group.
d The S. mutans group includes S. mutans, S. sobrinus, and the following species rarely isolated from humans: S. criceti, S. ratti, and S. downei.
e The S. salivarius group contains S. salivarius, S. vestibularis, and S. thermophilus. S. salivarius is variable, S. vestibularis is positive, and S. thermophilus is negative for urea hydrolysis.
f The S. bovis group now includes S. equinus, S. gallolyticus, S. infantarius, and S. alactolyticus. S. gallolyticus subsp. gallolyticus is positive for the acidification of mannitol; the other species from the S. bovis group are negative.
Phenotypic characteristics of streptococcal species of the S. anginosus group a
a Symbols and abbreviations: +, positive; –, negative; v, variable. Data are from Summanen et al. ( 113 ), Facklam ( 36 ), and Whiley et al. ( 129 ).
b The species S. constellatus subsp. pharyngis is β-D-fucosidase, β-D-acetylglucosaminidase, β-D-acetylgalactosaminidase, and β-D-glucosidase positive, in contrast to S. constellatus subsp. constellatus, which is negative for these activities.
c Voges-Proskauer test (formation of acetoin from glucose fermentation).
Phenotypic characteristics of streptococcal species of the S. anginosus group a
a Symbols and abbreviations: +, positive; –, negative; v, variable. Data are from Summanen et al. ( 113 ), Facklam ( 36 ), and Whiley et al. ( 129 ).
b The species S. constellatus subsp. pharyngis is β-D-fucosidase, β-D-acetylglucosaminidase, β-D-acetylgalactosaminidase, and β-D-glucosidase positive, in contrast to S. constellatus subsp. constellatus, which is negative for these activities.
c Voges-Proskauer test (formation of acetoin from glucose fermentation).