Accuracy of Phenotypic and Genotypic Testing for Identification of Streptococcus pneumoniae and Description of Streptococcus pseudopneumoniae sp. nov

Abstract

We have identified an unusual group of viridans group streptococci that resemble Streptococcus pneumoniae. DNA-DNA homology studies suggested that a subset of these isolates represent a novel species that may be included in the S. oralis-S. mitis group of viridans group streptococci. We suggest that this novel species be termed Streptococcus pseudopneumoniae. A combination of phenotypic and genetic reactions allows its identification. S. pseudopneumoniae strains do not have pneumococcal capsules, are resistant to optochin (inhibition zones, less than 14 mm) when they are incubated under an atmosphere of increased CO 2 but are susceptible to optochin (inhibition zones, >14 mm) when they are incubated in ambient atmospheres, are not soluble in bile, and are positive by the GenProbe AccuProbe Pneumococcus test. The bile solubility test is more specific than the optochin test for identification of S. pneumoniae. Genetic tests for pneumolysin (ply) and manganesedependent superoxide dismutase (sodA) and identification tests with a commercial probe, AccuProbe Pneumococcus, do not discriminate between the new species and S. pneumoniae.Streptococcus pneumoniae is the most common cause of community-acquired pneumonia and is also associated with bacteremia, meningitis, otitis media, and sinusitis, accounting for approximately 3,000 cases of meningitis, 50,000 cases of bacteremia, 500,000 cases of pneumonia, and 7 million cases of otitis media each year in the United States (1). Clinical laboratories must be able to accurately differentiate S. pneumoniae from other viridans group streptococci commonly found in clinical samples. An inability to correctly identify S. pneumoniae may result in inappropriate antimicrobial therapy.S. pneumoniae is a member of the Streptococcus mitis-Streptococcus oralis group (the Smit group) of viridans group streptococci, which includes S. mitis, S. oralis, Streptococcus cristatus, Streptococcus infantis, and Streptococcus peroris. Differentiation of S. pneumoniae from other viridans group streptococci, including members of the Smit group, has conventionally been based on phenotypic characteristics, most commonly by demonstrating optochin (OPT) susceptibility and/or solubility in bile (sodium deoxycholate) (18). Identification by these two tests is satisfactory when isolates from sterile sites are tested (16). However, identification is often problematic when samples from nonsterile sites, such as respiratory samples, are tested. The results of phenotypic testing can result in ambiguous OPT susceptibility and bile solubility (BS) test results (18).Although they are uncommon, OPT resistance has been reported in S. pneumoniae and OPT-resistant subpopulations have also been reported, both of which may lead to problems in identification, especially in association with atypical colony morphologies (4,13,36,42,45,46,55,60). Gardam and Miller (21) reported that variances in OPT zone sizes are dependent on the test medium and incubation environment used, as some media and environments may result in f...

Streptococcus rubneri sp. nov., isolated from the human throat

“…Table 1. Biochemical characteristics that differentiate the novel strains from other members of the mitis group Taxa: 1, S. australis (data from Willcox et al, 2001); 2, S. cristatus (Handley et al, 1991;Willcox et al, 2001); 3, S. gordonii (Kilian et al, 1989;Willcox et al, 2001); 4, S. infantis (Kawamura et al, 1998;Whiley & Hardie, 2009); 5, S. lactarius (Martín et al, 2011); 6, S. massiliensis (Glazunova et al, 2006); 7, S. mitis (Whiley & Hardie, 2009); 8, S. oligofermentans (Tong et al, 2003); 9, S. oralis (Bridge & Sneath, 1982;Whiley & Hardie, 2009); 10, S. parasanguinis (Whiley et al, 1990;Willcox et al, 2001); 11, S. peroris (Kawamura et al, 1998;Martín et al, 2011); 12, S. pneumoniae (Whiley & Hardie, 2009); 13, S. pseudopneumoniae (Arbique et al, 2004;Zbinden et al, 2012); 14, S. rubneri sp. nov. (this study); 15, S. sanguinis (Willcox et al, 2001); 16, S. sinensis (Woo et al, 2002); 17, S. tigurinus (Zbinden et al, 2012).…”

Use of Phylogenetic and Phenotypic Analyses To Identify Nonhemolytic Streptococci Isolated from Bacteremic Patients

“…The inherent problem of this approach is the large number of species relative to the limited number of biochemical traits that can be analyzed, the variability of several traits within species (33,35,36,44), the poor reproducibility of some tests (12,17,26,36,44), and the lack of sufficient phenotypic data on more recently described species in the underlying databases. The last problem applies to the species S. cristatus (23), S. peroris, S. infantis (31), S. australis (55), S. sinensis (57), Streptococcus macedonicus (51), Streptococcus infantarius, Streptococcus lutetiensis, Streptococcus gallolyticus (42), and S. pseudopneumoniae (1).…”

“…Many of the species of these five clusters are major constituents of the commensal microbiota of the human oral cavity and upper respiratory tract and are occasionally implicated in various pathologies. The anginosus group, formerly called "Streptococcus milleri" in some parts of the world (16), includes three recognized species (Streptococcus anginosus, Streptococcus intermedius, and Streptococcus constellatus) that are primarily associated with suppurative infections of tissues of the mouth and various body sites, including the meninges (9,37,44,54,56 Although they are commensals of the upper respiratory tract, S. pneumoniae is a major cause of both local and systemic infections and several of the other mitis group streptococci have long been recognized as important etiologic agents of subacute bacterial endocarditis (2,13); septicemia, particularly in neutropenic cancer patients (5,6,29); occasional cases of meningitis (8); and eye infections (1). The two species of the salivarius group associated with humans (Streptococcus salivarius and Streptococcus vestibularis) are usually considered to be of low virulence, although occasional life-threatening infections such as bacteremia and meningitis have been reported (11,43).…”

Streptococcus pseudopneumoniae as an emerging pathogen from patients with respiratory diseases

“…Streptococcus pseudopneumoniae as suggested by DNA-DNA homology studies is recorded as a species of the Streptococcus mitis/oralis members of viridans group Streptococci; they have some similar features to Streptococcus pneumoniae (Arbique et al, 2004). The principle characteristics of S. pseudopneumoniae are the lacking of pneumococcal capsule, bile insolubility, indeterminate sensitivity or resistance to optochin after *Corresponding author.…”