The Centers for Disease Control and Prevention (CDC) has identified an increasing number of Shigella isolates that test within the susceptible range for the fluoroquinolone antibiotic ciprofloxacin (minimum inhibitory concentration [MIC] values of 0.12 to 1 μg/mL), but harbor 1 or more resistance mechanisms. The CDC has also identified an increasing number of Shigella isolates with azithromycin MICs that exceed the epidemiologic cutoff value (ECV).

Shigellosis is a nationally notifiable condition; all cases should be reported to local health departments. Recommendations for clinicians are as follows:

  1. If antibiotic treatment is necessary, monitor patients carefully.
  2. If you identify or receive a report of a patient with Shigella infection and possible fluoroquinolone or azithromycin treatment failure:
    1. Consider consulting an infectious disease specialist to identify other treatment options, because some Shigella isolates with susceptible ciprofloxacin MICs may harbor one or more quinolone resistance mechanisms.
    2. Contact your local health department to coordinate reporting treatment failure information. This information should be reported to CDC.
    3. Collect a stool specimen for culture, and work with your clinical microbiology laboratory to submit for additional antimicrobial susceptibility testing.
    4. Request that your laboratory expedite submission of the Shigella isolate to your state public health laboratory. Your state laboratory should notify the CDC at [email protected] to coordinate additional laboratory testing and/or shipment of the isolate to CDC.

The CDC is particularly concerned about people who are at high risk for multidrug-resistant Shigella infections and are more likely to require antibiotic treatment, such as men who have sex with men, patients who are homeless, and immunocompromised patients. These patients often have more severe disease, prolonged shedding, and recurrent infections.

Continue Reading

Related Articles

The CDC is working with Clinical and Laboratory Standards Institute (CLSI) and other partners to collect isolates and clinical information from people with Shigella infection and possible clinical treatment failure occurring after treatment with a fluoroquinolone or azithromycin. If treatment failure is suspected, clinicians should consider consulting an infectious disease specialist to identify best treatment options and submit a stool specimen for antimicrobial susceptibility testing. Clinicians should monitor patients carefully and report cases of possible clinical treatment failure to the CDC.


CDC. Update – Recommendations for managing and reporting Shigella infections with possible reduced susceptibility to ciprofloxacin [news update]. June 7, 2018. Accessible at: