February 18, 2019
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Group B Streptococcus rises among nonpregnant adults

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The incidence of invasive group B Streptococcus rose among nonpregnant adults between 2008 and 2016, particularly among those with obesity and diabetes, according to a study published in JAMA Internal Medicine.

Group B Streptococcus (GBS) is an important cause of invasive bacterial disease,” Louise K. Francois Watkins, MD, MPH, from the Epidemic Intelligence Service Program at the CDC, and colleagues wrote. “Previous studies have shown a substantial and increasing burden of GBS infections among nonpregnant adults, particularly older adults and those with underlying medical conditions.”

Watkins and colleagues conducted a population-based surveillance study to estimate the updated trends in invasive GBS infections among nonpregnant adults aged 18 years or older who were residents of an Active Bacterial Core surveillance (ABCs) catchment site between 2008 and 2016.

The researchers defined a case as isolation of GBS from a normally sterile body site. They abstracted demographic and clinical data from medical records and calculated GBS rates using U.S. Census data. They also performed antimicrobial susceptibility testing and serotyping on a subset of isolates.

A total of 21,250 patients with invasive GBS were identified via the ABCs network. There was a significant increase in GBS incidence from 8.1 cases per 100,000 population in 2008 to 10.9 in 2016.

In 2016, 3,146 cases were reported (59% male; median age, 64 years; age range, 18 to 103 years). There was a higher rate of GBS among men vs. women and among blacks vs. whites. Additionally, the incidence of GBS rose with age.

The researchers estimated that in 2016, there were 27,729 cases of invasive disease and 1,541 related deaths in the United States. Underlying conditions, such as obesity (53.9%) and diabetes (53.4%), were observed in 95% of cases in 2016.

There was an increase in resistance to clindamycin from 37% in 2011 to 43.2% in 2016. This rise is concerning “given its clinical use in the management of skin and soft tissue infections, a common manifestation of GBS disease,” according to the researchers.

Most isolates (86.4%) were serotypes Ia, Ib, II, III and V in 2016. There was an increase in serotype IV from 4.7% in 2008 to 11.3% in 2016.

“The incidence of invasive GBS in nonpregnant adults continues to rise, with rates now exceeding those for invasive pneumococcal disease,” Watkins and colleagues concluded.

“A multivalent vaccine could target a substantial portion of adult disease but would be most influential if it included serotype IV, as well as the other major serotypes,” they added. “Ongoing surveillance to monitor future trends in serotype distribution and antibiotic resistance is warranted. Improved physician awareness and efforts aimed at reducing risk factors, such as obesity and diabetes, along with efforts to maintain skin integrity and provide optimal wound care, may help prevent invasive GBS infections.”

In an accompanying editorial, Miriam Baron Barshak, MD, from the division of infectious diseases at Massachusetts General Hospital and Harvard Medical School, wrote that the findings by Watkins and colleagues demonstrates that the population at risk for GBS is now “much more heterogenous than the obstetric and neonatal populations who were the predominant hosts for these infections in the past.”

“As GBS infections come of age with the obesity and diabetes epidemics, the burden of preventing, diagnosing, and treating invasive GBS infections in the US population has shifted from obstetricians and neonatologists to internists,” she wrote. “While we hope for progress in developing an effective GBS vaccine, we must continue to prevent, diagnose, and treat diabetes, obesity, and other underlying conditions that predispose patients to GBS infections.” – by Alaina Tedesco

 

Disclosures: Barshak and Watkins report no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures.

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