Streptococcus salivarius: Bacteremia & Endocarditis in Healthy Patients

A 40-year-ancient man presented with a four-month history of fever, fatigue, weight loss, and joint pain, ultimately diagnosed with infective endocarditis caused by Streptococcus salivarius, a bacterium typically found in the oral cavity, according to a case study presented at Hospital Medicine 2014.

The patient, who had a history of remote intravenous drug employ, initially exhibited symptoms including myalgias, migratory polyarticular pain, and an 18 kg unintentional weight loss. Initial tests revealed mild leukocytosis, elevated liver enzymes, microscopic hematuria, and elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels. Blood cultures identified gram-positive cocci in pairs and chains. A transthoracic echocardiogram revealed abnormalities in the aortic valve, which were later confirmed by a transesophageal echocardiogram to be echo-densities consistent with endocarditis and an ascending aortic valve aneurysm.

While Streptococcus salivarius is a common inhabitant of the human mouth, it is a rare cause of bacteremia and infective endocarditis. A study cited in the case report identified only 4 out of 183 cases of endocarditis caused by Viridans streptococci as being attributable to S. Salivarius. The infection is typically linked to a breakdown in the mucosal lining of the gastrointestinal tract and may indicate an underlying medical condition or malignancy, though a CT scan of the patient’s chest, abdomen, and pelvis did not reveal any evidence of cancer.

The patient was initially treated with empirical vancomycin, which was later switched to ceftriaxone after speciation confirmed susceptibility. Repeat blood cultures were negative following antibiotic treatment. He was evaluated by gastroenterology, infectious disease, and cardiothoracic surgery specialists. A follow-up plan including elective colonoscopy and aortic valve and aneurysm repair was established. The patient was discharged to complete a long-term course of intravenous antibiotics and was reported to be doing well at the time of the case study’s presentation.

Research indicates that the prevalence of infective endocarditis varies depending on the specific streptococcal species involved. A study published in 2023 investigated the prevalence of IE at the species level in patients with streptococcal bloodstream infections, highlighting the need to understand species-specific risks. Another study aimed to identify which streptococcal species are closely associated with IE and to evaluate risk factors for mortality in patients with the condition.

Streptococcus salivarius-related endocarditis is uncommon, and its association with colon malignancy is not strong, according to the case study’s conclusions. The case underscores the potential for opportunistic infections from commensal bacteria in the context of underlying vulnerabilities, such as a history of intravenous drug use or a compromised mucosal barrier.