The Centers for Disease Control and Prevention (CDC) has issued an alert to healthcare professionals regarding new recommendations for the treatment of Shigella infection. 

Recent data indicate the presence of certain Shigella strains that have a quinolone resistance gene that may lead to reduced susceptibility to fluoroquinolone antibiotics. Specifically, the CDC has identified an increase in Shigella isolates with minimum inhibitory concentration (MIC) values of 0.12–1μg/mL for the fluoroquinolone antibiotic ciprofloxacin. This is concerning as fluoroquinolone treatment of an infection with a strain harboring a quinolone resistance gene may be less effective and may increase the risk of a more severe clinical course for the patient. It may also increase the risk of secondary cases if the treatment prolongs the duration or increases the quantity of organisms shed in the stool.

The alert provides specific recommendations for clinicians managing patients with suspected Shigella infection:

  • Order stool culture to obtain isolates for antimicrobial susceptibility testing
  • Order antimicrobial susceptibility testing when ordering stool culture for Shigella; request ciprofloxacin testing that includes dilutions of 0.12μg/mL or lower
  • Do not routinely prescribe antibiotic therapy; reserve antibiotics for patients for whom it is clinically indicated or in an outbreak setting
  • When antibiotic treatment is indicated, tailor antibiotic choice to antimicrobial susceptibility results as soon as possible with special attention given to the MIC for fluoroquinolone antibiotics; avoid prescribing fluoroquinolones if the ciprofloxacin MIC is 0.12μg/mL or higher even if the laboratory report identifies the isolate as susceptible
  • Obtain follow-up stool cultures in patients who have continued or worsening symptoms despite antibiotic therapy
  • Report all cases of shigellosis to your local health department
  • Clinicians who identify a patient with shigellosis and a ciprofloxacin MIC of 0.12–1μg/mL should include this finding along with other information regarding the case to their local health department to facilitate further testing of the isolate

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The CDC will continue to monitor trends in antimicrobial susceptibility and has notified representatives at the U.S. Food and Drug Administration and Clinical and Laboratory Standards Institute, who will review the findings to determine whether a change to the susceptible range of MIC values for ciprofloxacin in Shigella is warranted.

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