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CDC Reports Increase in Extensively Drug-Resistant Shigella Infections in the United States

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CDC Reports Sharp Rise in Drug-Resistant Shigella Infections

A new report from the U.S. Centers for Disease Control and Prevention (CDC) details a significant increase in infections caused by an extensively drug-resistant (XDR) strain of Shigella bacteria. The proportion of shigellosis cases attributed to this strain rose from 0% in 2011 to 8.5% in 2023. The CDC has described the strain as a public health threat and called for strengthened surveillance.

Report Findings and Infection Trends

The CDC's analysis, based on data from its PulseNet surveillance network from January 2011 to October 2023, identified 16,788 shigellosis infections. Of these, 505 were caused by the XDR strain.

  • Recent Increase: Infections from the XDR strain were rare until 2020, after which they increased notably.
  • 2023 Data: In 2023, the XDR strain was identified in 280 of approximately 3,500 recorded shigellosis infections.

Characteristics of the XDR Strain

The XDR strain shows resistance to multiple antibiotics typically used for treatment.

  • Bacterial Types: Of the 505 XDR cases analyzed, approximately 66% were caused by Shigella sonnei, which is resistant to at least three antibiotics. The remaining 172 cases were caused by Shigella flexneri, resistant to at least four antibiotics.
  • Increased Severity: About one-third (approximately 33%) of patients infected with the XDR strain were hospitalized. The typical hospitalization rate for shigellosis is about 1%. No deaths from the XDR strain have been reported in the United States.

Demographic and Geographic Patterns

The demographic profile for the XDR strain differs from historical patterns for shigellosis.

  • Patient Demographics: Among patients with the XDR strain, 86.2% were male, with an average age of 41. Historically, shigellosis has been most common in children under five years old.
  • Travel History: 76% of patients with the XDR strain reported no recent travel, and 82% reported no recent international travel.
  • Geographic Distribution in 2023:
    • Western United States: 54% of XDR infections
    • Northeast: 38%
    • South and Midwest: Approximately 10% each

Background on Shigellosis

Shigellosis is a gastrointestinal infection caused by Shigella bacteria.

  • Transmission: The bacteria are transmitted through contact with feces. This can occur through contaminated food or water, or through direct person-to-person contact, including sexual activity.
  • Symptoms: Illness causes diarrhea, which can be bloody, stomach pain, and fever. Symptoms typically last about one week.
  • Annual Burden: The CDC estimates approximately 450,000 shigellosis infections occur in the United States annually, resulting in about 6,000 hospitalizations and 40 deaths.

Broader Context on Antibiotic Resistance

The emergence of XDR Shigella occurs within the wider context of antimicrobial resistance.

The CDC reports that more than 2.8 million drug-resistant bacterial infections are diagnosed in the United States each year, resulting in approximately 35,000 deaths.

  • Antibiotic Use: The agency estimates about 236 million antibiotic prescriptions are written for people in the United States annually, with additional doses administered to animals. Extensive antibiotic use can contribute to the development of drug-resistant bacteria.