First Japanese case of infectious endocarditis due to Enterococcus faecalis small-colony variants.
A male patient was admitted to our hospital due to infectious endocarditis. He had been treated with levofloxacin for 6 weeks, sulbactam/cefoperazone for 4 weeks, and benzylpenicillin for 2 days prior to valve replacement surgery. Gram-positive cocci, with morphology consistent with γ-Streptococcus, were detected in blood cultures obtained at admission, as well as in vegetation obtained from the aortic valve. However, the strain could not be identified using biochemical methods. Sequencing of the 16S rRNA gene indicated that the culture was a small-colony variant of Enterococcus faecalis. This is the first case in Japan of infectious endocarditis due to E. faecalis small-colony variants. Small-colony variants are subpopulations of bacteria with slow growth, reduced sugar fermentation, and unstable phenotype. As a result, these strains tend to be misidentified. Further, small-colony variants are associated with recurrent and persistent infections such as prosthetic joint infection and infectious endocarditis. These strains are found in various bacterial species, including Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa, but rarely in Enterococcus species. The case highlights the need to be vigilant of E. faecalis small-colony variants, especially in patients who received long-term courses of antibiotics.
Department of Clinical Laboratory, Tokyo Medical and Dental University Hospital of Medicine, 1-5-45 Yushima, Bunkyo-Ku, Tokyo 113-8519, Japan. Electronic address: ogihara.shi@gmail.com.
Shinji
S
Ogihara
Department of Microbiology and Immunology, Graduate School of Health Care Sciences, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Ryoichi
R
Saito
Department of Clinical Laboratory, Tokyo Medical and Dental University Hospital of Medicine, 1-5-45 Yushima, Bunkyo-Ku, Tokyo 113-8519, Japan.
Etsuko
E
Sawabe
Department of Clinical Laboratory, Tokyo Medical and Dental University Hospital of Medicine, 1-5-45 Yushima, Bunkyo-Ku, Tokyo 113-8519, Japan.
Michio
M
Hagihara
Department of Clinical Laboratory, Tokyo Medical and Dental University Hospital of Medicine, 1-5-45 Yushima, Bunkyo-Ku, Tokyo 113-8519, Japan.
Shuji
S
Tohda
D000368:Aged; D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000627:therapeutic use; D001021:Aortic Valve / Q000382:microbiology / Q000601:surgery; D004269:DNA, Bacterial / Q000302:isolation & purification; D004697:Endocarditis, Bacterial / Q000188:drug therapy / Q000382:microbiology* / Q000601:surgery; D013293:Enterococcus faecalis / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification*; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy / Q000382:microbiology* / Q000601:surgery; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D007564:Japan; D008297:Male; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
Enterococcus faecalis; Infectious endocarditis; Small-colony variants