Streptococcus anginosus group is a subclass of viridans streptococci that consists of three distinct species: S. anginosus. S. constellatus, and S. intermedius. Organisms in this group are commonly found as commensal flora but have the potential to cause pyogenic infections such as empyema, brain abscess, liver abscess, infective endocarditis, and meningitis. Predisposing risk factors for such infections include recent surgery, malignancy, dental procedures, and tobacco use.
Within a few months, the general medicine service at our institution encountered several cases of deep visceral abscesses caused by the Streptococcus anginosus group in patients on chronic immunosuppressive medications without the above risk factors. These cases prompted an investigation of nontraditional risk factors, particularly immunosuppression, in the susceptibility to and morbidity from S. anginosus infections.
A microbiology database search was conducted to identify Streptococcus anginosus infections between 2005 and 2013. The clinical, radiographic, and treatment data were analyzed for each case.
There were twenty‐five cases of pyogenic Streptococcus anginosus group infections. The majority of these infections were caused by S. constellatus species (21/25), followed by S. anginosus (3/25), and lastly S. intermedius (1/25). The gastrointestinal tract was affected in 48%, thorax in 40%, head and neck in 20%, blood stream in 12%, and bone in 4%. All of the patients required surgical intervention and at least one week of intravenous antibiotics. An examination of the demographics, comorbidities, and medications showed that twelve of the twenty‐five patients (48%) had previously recognized risk factors. Six other patients were identified to carry a different risk factor: chronic immunosuppressant use (steroid or tumor necrosis factor alpha inhibitor), recent chemotherapy treatment, or HIV. Three of these six were the only patients to be readmitted to the hospital with recurrence of the original infection requiring prolonged antibiotic treatment and repeat surgical drainage. The remaining seven patients had no identifiable risk factors. Patients with any risk factor were more likely to have multi‐organ involvement (6/18 versus 0/7) and longer average length of stay (18 days versus 13 days) than those with no risk factor. All but one patient survived to discharge.
Pyogenic infections with Streptococcus anginosus resulted in significant morbidity, particularly for patients with identifiable risk factors as they were more likely to have disseminated disease and longer hospital stays. Additionally, we have identified emerging risk factors such as immunosuppressive medication use, recent chemotherapy, and HIV that increase the risk for recurrent infection and invasive procedures.
To cite this abstract:Wu 2, Burger A. Emerging Risk Factors for Pyogenic Streptococcus Anginosus Infections: A Review of 25 Cases. Abstract published at Hospital Medicine 2014, March 24-27, Las Vegas, Nev. Abstract 75. Journal of Hospital Medicine. 2014; 9 (suppl 2). https://www.shmabstracts.com/abstract/emerging-risk-factors-for-pyogenic-streptococcus-anginosus-infections-a-review-of-25-cases/. Accessed July 17, 2019.