New data suggest Group B Streptococcus infections are more common than previously recognized

LOUISVILLE, Ky. – Detailed results were published this week of the first study to show the burden of both invasive and non-invasive Group B Streptococcus (GBS) infections among hospitalized adults in the United States. The study, a collaboration with University of Louisville Division of Infectious Diseases and Pfizer Inc., was published in The Journal of Infectious Diseases. The authors estimated that 188,570 GBS-related hospitalizations and 5,660 deaths occur each year among US adults 18 or older when including both invasive and non-invasive GBS infections.

Bacteria called Group B Streptococcus or Streptococcus agalactiae (Group B strep, GBS) commonly live in people’s gastrointestinal and genital tracts. Most of the time, the bacteria are not harmful and do not make people feel sick or have any symptoms. Sometimes, however, the bacteria invade the body and cause certain infections, which are known as GBS disease. GBS bacteria can cause bacteremia (bloodstream infection) and sepsis (the body’s extreme response to an infection), meningitis, pneumonia, bone and joint and skin and soft-tissue infections. An invasive GBS infection is one that involves blood or internal organs, whereas a noninvasive infection could involve skin or other soft tissue, the urinary tract or bones and joints.

Previous studies describing the burden of GBS infection in adults have primarily focused on invasive disease because existing surveillance systems rely on blood culture collection. In the new study, however, non-invasive disease was three to four times more common than invasive disease, suggesting that adult GBS burden is considerably greater than previously recognized. Of the infections reviewed, 79 percent were non-invasive. In 60 percent of the infections, GBS was identified as the only pathogen.

“These new data suggest that the burden of GBS infection is considerably greater than previously recognized in earlier surveillance studies that only focused on invasive disease, ” said Julio Ramirez, M.D., chief of the Division of Infectious Diseases at UofL. “Importantly, we found that the rates of GBS infection in this study are comparable to that of other adult infections for which vaccines are routinely recommended, which underscores the need for developing approaches for preventing this infectious disease among an aging adult population.”

In conducting the study, the researchers reviewed laboratory and medical records from six hospitals in Louisville between Jan. 1, 2014 and Dec. 31, 2016. Louisville’s population is generally similar to the United States in terms of demographics and prevalence of underlying chronic medical conditions.

Rates of GBS-associated hospitalization were significantly higher in adults 65 years and older, African Americans and people with underlying chronic medical conditions such as obesity, diabetes, chronic renal disease and coronary artery disease. The finding that obesity and diabetes put patients at increased risk for GBS-associated hospitalization is especially noteworthy given that recent Centers for Disease Control and Prevention (CDC) reports have highlighted that 42 percent of U.S. adults are obese and that as many as 34 million American adults (roughly 13 percent of all U.S. adults) have diabetes, with another 88 million having pre-diabetes.

Additional findings from the study included the following:

• Annual rates of GBS infection in African American adults were 2.6 times higher than in white adults, or 157 per 100,000 in African American vs. 60 per 100,000 in white adults.
• Compared with the general population, annual GBS infection rates were 2 to 6 times higher among adults with underlying chronic medical conditions, such as chronic kidney disease, diabetes, obesity or heart disease.

“This type of study, evaluating both invasive and non-invasive GBS infections, is essential for understanding the full spectrum of GBS disease burden among adults,” said John M. McLaughlin, Ph.D., Global Epidemiology and Scientific Affairs Lead, Pipeline Vaccines, Pfizer Inc., and the lead study author. “These data should aid health care providers with clinical decision-making. Our population-based study gives the first estimates of total annual GBS burden in the United States, emphasizing the importance of preventive efforts in the growing population of adults who are older or have chronic medical conditions, and will inform future vaccination strategies.”

In January, Pfizer launched its Vaccines Division’s Centers of Excellence Network, a global program of collaborations with academic institutions to conduct real-world epidemiologic research to accurately identify and measure the burden of specific vaccine-preventable diseases and potentially evaluate vaccine effectiveness in adults. At that time, the UofL Division of Infectious Diseases was designated as the first Center of Excellence for epidemiological research of vaccine-preventable diseases by Pfizer Vaccines. This collaboration is aimed at determining the human health burden of important infectious diseases and potential vaccine effectiveness.

The GBS collaborative study between UofL and Pfizer was completed prior to the university being named as Pfizer Vaccine’s first Center of Excellence site.

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