- Volume 60, Issue 12, 2011

Oral streptococci are major pathogens of infective endocarditis. Prophylactic antibiotics are commonly given to subjects with certain kinds of heart disorders when invasive dental treatments are performed, with amoxicillin (AMPC) being widely used for this purpose. However, there is little information regarding AMPC-resistant oral streptococci. Here, a total of 344 dental plaque specimens collected from 253 healthy Japanese children, adolescents and young adults (aged 2–22 years) were diluted and streaked onto culture medium containing high-dose AMPC. The MICs for the isolated strains were evaluated using a macrodilution broth method described by the Clinical and Laboratory Standards Institute. Bacterial DNA was extracted from each strain and the entire sequences of the 16S rRNA gene were compared with those in GenBank to identify the species. The results showed that strains with AMPC MICs >16 µg ml−1 were isolated from 18 specimens from 14 patients. Analyses of the 16S rRNA gene sequences of these strains identified them as major oral streptococcal species, including Streptococcus oralis and Streptococcus mitis. These findings indicate that oral streptococci with elevated MICs for AMPC exist in certain small populations of healthy children, and highlight the need for further studies to determine risk factors that lead to the appearance of such strains.

Ankle arthritis was induced by a single subcutaneous (s.c.) infection of 1×107 c.f.u. of the Streptococcus dysgalactiae subspecies equisimilis strain RE378, which was isolated from a patient suffering from multiple organ failure due to septicaemia, into both hind footpads of human CD46-expressing transgenic (Tg) mice. In contrast, in non-Tg mice, the incipient foot lesions (swelling and redness) resolved before arthritis developed. The number of viable bacteria in tissue samples and the arthritis frequency on days 3 and 28 after infection were higher in CD46 Tg mice than in non-Tg mice. The histopathological findings in the hind ankle sections of CD46 Tg mice showed the stimulation of osteoclast formation associated with inflammation of the synovial membrane and the development of aggressive granulation tissue (pannus). In addition, increased expression levels of interleukin (IL)-6, receptor activator of NF-κB ligand, IL-1β and tumour necrosis factor alpha were detected in the foot bones of CD46 Tg mice but not in those of non-Tg mice. These observations suggest that the s.c. infection with S. dysgalactiae subsp. equisimilis induced arthritis in the ankle joints of CD46 Tg mice as a consequence of the prolonged inflammation associated with focal bone loss.

Trichoderma longibrachiatum is an emerging pathogen in immunocompromised patients. We report a case of Trichoderma post-operative mediastinitis and peritonitis in a child with complex congenital cardiac disease and functional asplenia. The patient was treated unsuccessfully, initially with caspofungin alone followed by a combination of voriconazole (systemic and topical), caspofungin and intraperitoneal amphotericin B.

Current practice guidelines recommend that pulmonary blastomycosis be treated with antifungal agents such as amphotericin B and itraconazole. Echinocandins are not recommended because of poor in vitro activity against Blastomyces dermatitidis and lack of supporting clinical data. We report a case of chronic pulmonary blastomycosis treated successfully with caspofungin.