Despite the improvements in prosthetic valve design and material, prosthetic valve endocarditis (PVE) remains a serious complication occurring in up to 3.7% of patients who undergo primary or redo replacement surgeries.1 2
A variety of microorganisms are involved in the pathogenesis of PVE. In early cases, S epidermidis
is the responsible bacterium in most cases, followed by S aureus
and fungi. However, in late PVE, Streptococci
are the main causative organisms together with S aureus
and the HACEK group (Haemophilus
).1 3 4
rarely cause endocarditis. These organisms are usually regarded as contaminants from skin and mucus membranes. However, they are being reported as emerging pathogens in immunocompromised patients and have been described in severe infections.5
The genus Kytococcus
was established in 1995 with the type K sedentarius
. It was classified as a member of the family Dermatophilaceae
is a new micrococcal species that was first described in 2002.7
Cells are spherical and occur usually in pairs or tetrads. Colonies are between 1.5 and 2.5 mm in diameter after 48 h of incubation, muddy yellow, non-haemolytic, circular, convex and smooth, and they develop rather slowly. This species is negative by oxidase test, positive for alkaline phosphatase, arginine dihydrolase and pyrazinamidase, and negative for lecithinase, β-galactosidase and urease. It hydrolyses gelatin and Tween 80 but does not hydrolyse esculin or starch. The optimum growth temperature is 37 °C. K schroeteri
is resistant to penicillin G, oxacillin and erythromycin, and susceptible to imipenem, chloramphenicol, ciprofloxacin, gentamicin, tetracycline, vancomycin and teicoplanin. The type strain is strain Muenster 2000.7
is likely to emerge as an increasingly important bacterial pathogen as five infections due to K schroeteri
were described within a 5-year period: four cases of K schroeteri
endocarditis and recently a fatal K schroeteri
bacteraemic pneumonia in a patient undergoing chronic corticosteroid treatment.8
Sequencing of the 16S rRNA is the diagnostic tool for the correct identification of K schroeteri
. However, Gram positive cocci that are arranged in tetrads and which are oxacillin resistant and arginine dihydrolase positive should raise a concern of a possible Kytococcus
- K schroeteri is a newly described organism, which rarely can cause endocarditis.
- This organism can be misdiagnosed and should be suspected if Gram positive cocci are cultured but are oxacillin, penicillin G and erythromycin resistant.
- Sequencing of the 16S rRNA is the diagnostic tool for the correct identification of K schroeteri.
- K schroeteri is sensitive to imipenem, chloramphenicol, ciprofloxacin, gentamicin, tetracycline, vancomycin and teicoplanin.