Subcutaneous abscess caused by Streptococcus pneumoniae serotype 28F in an infant: a case report

Invasive pneumococcal disease (IPD) is defined by the detection of Streptococcus pneumoniae on culture from samples obtained from a normally sterile site. Pneumococcal conjugate vaccines (PCV) have been developed for the prevention of IPD that is caused by highly virulent serotypes. Despite the effective reduction of IPD caused by vaccine serotypes after the introduction of PCV, there has been a rapid increase in the incidence of IPD caused by non-vaccine serotypes, and serotype replacement has become a global issue. We report a previously healthy 4-month-old girl presenting with a large subcutaneous abscess caused by S. pneumoniae, identified as non-vaccine serotype 28F. The patient had received routine vaccination, including PCV vaccination. After the incision and drainage of the subcutaneous abscess, the patient was treated with antibiotics. She was discharged on Day 7 of hospitalization without any residual sequelae. Subcutaneous abscess is a common pediatric skin and soft tissue infection, whereas pneumococcal subcutaneous abscesses are quite rare. As the pneumococcal serotype 28F caused a subcutaneous abscess, this serotype possibly has a high virulence. The incidence of IPD caused by non-vaccine serotypes, such as 28F, is expected to increase in the future. The consolidation of international data on pneumococcal serotypes is important for the development of novel PCV.