Molecular epidemiologic evaluation of endocarditis due to Oerskovia turbata and CDC group A-3 associated with contaminated homograft valves

Abstract

Oerskovia turbata is an unusual bacterial cause of endocarditis and septicemia in immunocompromised patients. In this study, we compared 12 isolates from a 1975 medical center cluster, 11 originally identified as O. turbata (four from the blood of a homograft aortic valve-associated endocarditis patient and seven from contaminated homograft valves) and one CDC group A-3 strain from the blood of a second endocarditis patient with fatal outcome, with eight control strains from unrelated locations. The control strains included type and reference strains of O. turbata, Cellulomonas hominis, and CDC group A-3. The four blood isolates from the first patient and six of the valve isolates shared identical biochemical, antimicrobial susceptibility, and BglI ribotype patterns that differed from the second patient's isolate and control strains. The blood isolate from the second patient and the remaining valve isolate shared a phenotypic and genotypic profile and were phenotypically identical to, but epidemiologically different from, the CDC group A-3 reference strain with the strain-specific enzyme. Also, these isolates differed from the type strain and the other reference strains of C. hominis and O. turbata. Our results indicate that the four blood isolates from the first patient and six of the homograft valve isolates represent a single clone of O. turbata associated with endocarditis. Additionally, our results indicate that the blood isolate from the second patient and one of the homograft valve isolates differ from O. turbata and C. hominis and represent a unique clone of CDC group A-3 associated with fatal endocarditis.

FIG. 1.

Ribotype patterns from BglI-digested genomic DNAs of medical center isolates and type and clinical reference isolates of O. turbata, CDC group A-3, and C. hominis. Lane 1, bacteriophage 8 DNA molecular size marker digested with EcoRI and HindIII; lane 2, type strain O. turbata ATCC 25835; lanes 3 to 6, clinical reference isolates of O. turbata, W6123, W2796, W4083, and W6035, respectively; lanes 7 to 10, 4 of 10 medical center isolates of O. turbata, W2622, W2728, W2729, and W6122 (patient 1's blood isolates) (homograft valve isolates [n = 6] not shown); lanes 11 and 12, medical center isolates of CDC group A-3, W6124 (homograft valve) and W6929 (patient 2's blood isolate), respectively; lane 13, type strain C. hominis DSM 9581; lane 14, clinical reference isolate of CDC group A-3, W6117.

FIG. 2.

Phylogenetic tree constructed by the neighbor-joining method showing the position of W6122 (patient 1's blood isolate) within the Cellulosimicrobium-Cellulomonas-Oerskovia lineage of the gram-positive bacilli with high G+C contents.

FIG. 3.

Phylogenetic tree constructed by the neighbor-joining method showing the position of W6929 (patient 2's blood isolate) within the Cellulomonas-Oerskovia-Sanguibacter lineage of the gram-positive bacilli with high G+C contents.