Location of Nutritionally Variant Streptococci
Nutritionally variant streptococci (now classified as Abiotrophia defectiva and Granulicatella species) are members of the normal oral flora found in healthy human oral cavities. 1, 2
Primary Anatomical Location
These organisms are oral commensals that colonize the mouth of healthy individuals. 2, 3
Specifically, they have been isolated from healthy human oral cavities in multiple studies examining their natural habitat. 2
As mouth commensals, they represent part of the normal bacterial flora that colonizes oral mucosal surfaces without causing disease in immunocompetent hosts. 3
Clinical Significance of Their Oral Location
Despite being normal oral inhabitants, these organisms are important causes of culture-negative endocarditis when they gain access to the bloodstream. 1
The oral location is clinically relevant because dental procedures or poor oral hygiene can lead to transient bacteremia, allowing these organisms to seed damaged or prosthetic heart valves. 2
Their presence in the oral cavity explains why they are frequently isolated from patients with endocarditis, as oral flora can enter the bloodstream through dental manipulation or spontaneous bacteremia. 2, 3
Critical Clinical Pitfall
The microbiology laboratory must be specifically notified when these organisms are suspected, as they will not grow on routine subculture media unless chocolate agar or media supplemented with pyridoxal hydrochloride or L-cysteine is used. 1
While automated blood culture systems can detect these organisms, they require special growth supplements (pyridoxal or L-cysteine) for subculture, which are not part of routine protocols. 1
Failure to use appropriate supplemented media will result in false-negative cultures and missed diagnoses, despite the organisms being present in blood cultures. 4, 1