Group D Streptococcus (GDS) Infections (Streptococcus bovis/Streptococcus gallolyticus)

Updated: Aug 10, 2017
  • Author: Shirin A Mazumder, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Overview

Background

Group D Streptococcus (GDS) infections in humans are most often associated with bacteremia, with or without endocarditis. Other less-common infections involving group D streptococci include urinary tract infections, meningitis, neonatal sepsis, spontaneous bacterial peritonitis, septic arthritis, and vertebral osteomyelitis. Traditionally, group D streptococcal infections have predominantly been caused by Streptococcus bovis, but recent taxonomy changes have produced confusion among clinicians.

S bovis is well-established in the literature as a cause of bacteremia and endocarditis and has a well-known association with gastrointestinal malignancy. For simplicity, S bovis is the terminology used throughout this article.

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Pathophysiology

The portal of entry for S bovis bacteremia is the gastrointestinal tract. The urinary tract, hepatobiliary tree and the oropharynx can also be sources of infection in some cases. S bovis bacteremia, with or without endocarditis, is strongly associated with an underlying malignancy or premalignant lesions of the colon. S bovis has also been isolated more frequently from the stools of patients with such malignancies.

Associations with nonmalignant diseases of the colon have also been reported. A similar relationship between bacteremia (or endocarditis) and chronic liver disease has been established. [1] In rare cases, gastric cancer has been found upon investigation following S bovis bacteremia. [2] Every patient with S bovis bacteremia, with or without endocarditis, should undergo evaluation for gastrointestinal malignancy.

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Epidemiology

Frequency

United States

Isolation of S bovis from microbiology specimens, particularly blood cultures, is uncommon. The SENTRY Antimicrobial Surveillance Program in the United States does not list group D streptococci among the 10 most common organisms that cause bloodstream infections, accounting for no more than 1% of all cases. [3] According to the SCOPE Program, streptococci accounted for 6% of all blood culture isolates among 30 US hospitals, with S bovis accounting for 2.4% of those streptococci. [4]

Despite these findings, the microorganisms most commonly implicated as etiologic agents in subacute infective endocarditis occurring on native valves in patients who were not intravenous drug users were Streptococcus viridans and S bovis. Since 1997, a review of the International Collaboration on Endocarditis merged database (ICE-MD) found that S bovis accounted for 16.7% of all streptococcal infective endocarditis cases reported in the United States. [5] However, this study reported findings from only two US hospitals.

International

SENTRY data indicate that S bovis was isolated in 1.3% and 6.9% of streptococcal bloodstream infections in Canada and Latin America, respectively. Kupferwasser et al compared patients with S bovis endocarditis with patients with endocarditis secondary to other causative microorganisms. In this German study, 177 cases of definite infective endocarditis were reported between 1983 and 1996, with 22 cases (12.5%) caused by S bovis. [6]

More-recent studies have shown an increasing proportion of infective endocarditis caused by S bovis, particularly in France and neighboring areas of southern Europe. An analysis of 559 cases of infective endocarditis in France in 1999 found that 25% were caused by S bovis. [7] A Spanish study recently reported similar findings. [8]

Mortality/Morbidity

Morbidity: A study by Kupferwasser et al showed that S bovis endocarditis is a severe infection. The duration of fever and the increased acute-phase reactants after the onset of treatment were longer than with infective endocarditis caused by other bacteria. Involvement of multiple valves and valvular damage resulting in moderate-to-severe regurgitation were also more common. Embolic events were less common and correlated with the smaller sizes of S bovis vegetations observed on transesophageal echocardiograms. Gastrointestinal lesions were observed in nearly 50% of patients with S bovis endocarditis. [6]

Mortality: Mortality rates from the same study were 45% for S bovis endocarditis and 25% for non– S bovis endocarditis. This is higher than the 7.5-38% mortality range reported previously. The increased mortality was related to the virulence of S bovis and to a more common occurrence of underlying extracardiac disease of which patients died during follow-up care. [6]

Race

Streptococcus group D infections have no known racial predilection.

Sex

Streptococcus group D infections have no reported sexual predilection.

Age

Nearly all individuals with S bovis endocarditis are older than 50 years, with a mean age of 67 years and age range of 49-76 years. This once meant that patients with S bovis endocarditis were on average older than patients with endocarditis caused by other species. However, the mean age for all cases of endocarditis has recently increased, making patients with S bovis endocarditis generally no older than those with endocarditis from other causes. [9]

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