Centers for Disease Control and Prevention

Antimicrobial Resistance Threats Report

Clindamycin-resistantgroup B Streptococcus

Threat Level: CONCERNING

In the United States in 2023:

CDC changed methodologies and data sources to produce the most comprehensive AR Threats Report to date. Direct comparison of this threat's data to previous reports is not recommended.

What you need to know

Group B Streptococcus (GBS) bacteria commonly live in people's gastrointestinal and genital tracts. Most of the time, these bacteria are not harmful. However, sometimes the bacteria can cause very serious illnesses, including bloodstream infections, pneumonia, meningitis, and skin infections.

GBS are a common cause of serious infections in newborns because mothers can pass the bacteria to their infants during labor and delivery. Having a GBS infection during pregnancy can cause preterm delivery or stillbirth. When indicated, doctors will give mothers antibiotics, such as penicillin, ampicillin, or clindamycin (for mothers with a severe penicillin allergy), during labor to help protect newborns from GBS infections. In adults, GBS primarily cause illness among pregnant and postpartum women, older adults, and people with certain medical conditions.

Widespread use of antibiotics has raised concerns about the development of drug resistance in GBS. Half of infections caused by GBS are resistant to clindamycin. If additional GBS resistance develops and treatment and prevention options remain limited, more people could die from GBS infection.

Clindamycin-resistant group B Streptococcus data

The number of invasive clindamycin-resistant group B Streptococcus (GBS) infections has been increasing for more than a decade. In 2023, about half of invasive GBS infections were resistant to clindamycin.

Estimated number of clindamycin-resistant group B Streptococcus (GBS) infections by year and age group in the U.S.

In 2022 and 2023, there were more than 300,000 estimated clindamycin-resistant GBS infections per year. Most clindamycin-resistant GBS infections were in adults 18 years and older.

Between 2022 and 2023, the estimated number of invasive clindamycin-resistant GBS infections remained stable, with more than 11,000 occurring each year.

Estimated number of resistant and susceptible invasive group B Streptococcus (GBS) infections and percent clindamycin-resistant by year in the U.S.

The estimated number of invasive clindamycin-resistant GBS infections increased more than 30% between 2014 and 2023, while the total number of invasive GBS infections stayed relatively steady. The percentage of invasive GBS infections that were resistant to clindamycin increased between 2013 and 2023 from 42.5% to 53.4%, consistent with trends from earlier years. Invasive infections happen when GBS bacteria spread to normally sterile (free from germs) body sites, such as blood, cerebrospinal fluid, or internal body sites like bone.

Resistance threatens critical treatment options for group B Streptococcus

A mother holds her newborn baby in a hospital room.

Antibiotics given during labor and delivery to certain women who tested positive for GBS help prevent spread to newborns during birth. Unfortunately, growing drug resistance significantly limits options for preventing and treating GBS infections. Source: Centers for Disease Control and Prevention employee, Jennifer Liang.

One in every four pregnant women carry group B Streptococcus (GBS) bacteria in their body. Women carrying GBS during pregnancy can pass the bacteria to their newborns. Four to six percent of babies who develop GBS infections will die, even with good medical care. Healthcare providers give women who test positive for GBS penicillin or ampicillin during labor and delivery to prevent spread to newborns during birth. Clindamycin is the recommended alternative treatment for patients with severe penicillin allergies.
Previously, erythromycin was an alternative treatment for patients with severe penicillin allergies but is no longer recommended due to high resistance (60%) and less effectiveness in protecting newborns from infections. Unfortunately, resistance to clindamycin is also growing—about 50% of GBS infections are clindamycin-resistant. Drug resistance significantly limits options for preventing and treating GBS infections in people with severe penicillin allergies.
Appropriate antibiotic prescribing and use and testing for severe penicillin allergy are important strategies to fight the development and spread of drug resistance in GBS and to ensure these life-saving drugs will remain effective in the future. While GBS vaccines are in late stages of development, implementing existing infection prevention strategies remains critically important.

How CDC combats clindamycin-resistant group B Streptococcus

  • Supporting health departments

    CDC offers guidance and assistance to health departments for group B Streptococcus (GBS) infection prevention, control, and response. This includes rapid technical assistance during GBS outbreaks.

  • Conducting population- and laboratory-based surveillance

    CDC uses the Active Bacterial Core surveillance (ABCs) platform to conduct surveillance for invasive GBS infections and antimicrobial resistance. ABCs, part of CDC's Emerging Infections Program, operates in 10 sites across the United States, covering a population of 38 million people for GBS surveillance. Through surveillance, CDC can identify and investigate invasive GBS infections and perform antimicrobial susceptibility testing on all isolates (pure samples of a germ). CDC uses this established, long-term surveillance platform to monitor trends by estimating annual incidence of invasive GBS infections and drug-resistant infections.

  • Expanding state public health lab capacity

    CDC uses whole genome sequencing (WGS) for quicker and more accurate detection of emerging strains, to track drug-resistant GBS, and to stay alert for potential new threats. WGS facilitates timely detection of related GBS infections for effective public health outbreak responses. CDC provides guidance and technical assistance to state health departments, which includes performing WGS to enable more efficient outbreak investigations.

  • Increasing access to monitoring data

    CDC analyzed more than 20,000 GBS genomes through ABCs and made them available to the research community. This effort enhances understanding of GBS, strengthens drug resistance monitoring, and informs vaccine development.

Clindamycin-resistant group B Streptococcus resources

Illustration of Clindamycin-resistant group B Streptococcus