What is the typical morphology of streptococci?
Streptococci often have a mucoid or smooth colonial morphology, and S pneumoniae colonies exhibit a central depression caused by rapid partial autolysis.
Which morphological property is characteristic of streptococci?
Morphology. Streptococci are coccoid bacterial cells microscopically, and stain purple (Gram-positive) when Gram staining technique is applied. They are nonmotile and non-spore forming. These cocci measure between 0.5 and 2 μm in diameter.
What is the key feature of the viridans group of streptococci?
Viridans streptococci possess the general characteristics common to all streptococci (see Chapter 198). They are facultatively anaerobic, gram-positive cocci that do not produce catalase or coagulase.
Is strep Viridans normal flora?
Streptococcus viridans, a heterogeneous group of alpha-hemolytic streptococci, is part of the normal flora of the mouth, usually responsible for dental caries (Streptococcus mutans, Streptococcus sanguinis), and pericoronitis, as well as for subacute infective endocarditis.
Where is Streptococcus Viridans?
The viridans streptococci are most prevalent in the oral cavity but also reside in the upper respiratory tract, the female genital tract, and all regions of the gastrointestinal tract; they also are occasionally found as part of the skin flora.
What group is viridans streptococci?
The viridans group streptococci (VGS) are a heterogeneous group of organisms that can be both commensal flora and pathogens in humans. They are the “grab bag” that remains when the beta-hemolytic streptococci, enterococci, and pneumococci are excluded from the streptococci.
Where is viridans streptococci?
What causes viridans streptococci?
Among the factors that predispose to development of viridans streptococcal sepsis are: profound neutropenia; mucositis, especially oral mucositis; cytarabine (Ara-C) therapy, which seems to have an effect beyond its association with mucositis; young age; and trimethoprim-sulphamethoxazole or quinolone administration.
What is Streptococcus viridans morphology and cell structure?
Streptococcus viridans morphology culture and cell structure. The most important species of the “viridans” group P. mutans, S. mitis, S. sanguinus, p anginosus, S. oralis and S. salivarius. most species are part of the normal oral flora. They are therefore referred to as “oral” streptococci.
Is viridans streptococci Gram positive or negative?
Viridans streptococci. The viridans streptococci are a large group of commensal streptococcal Gram-positive bacteria species that are α-hemolytic, producing a green coloration on blood agar plates (hence the name “viridans”, from Latin “vĭrĭdis”, green).
What is the role of viridans streptococci in the oral cavity?
Viridans streptococci. The viridans streptococci, and in particular the species of the mitis and salivarius groups, are dominant members of the resident microbiota of the oral cavity and pharynx in all age groups. They play an important role by inhibiting the colonization of many pathogens, including pyogenic streptococci.
What is the prevalence of viridans streptococci in the US?
Viridans streptococci are a rare cause of meningitis, accounting for approximately 0.3% to 3% of cases in adults. Few data exist for children, although one study implicated viridans streptococci in approximately 1% of pediatric cases.16 Most children are younger than 1 year of age and have concomitant BSI.