Shigella and Antibiotic Resistance
Antibiotic resistance in
isolates is a developing issue here and around the country. Ciprofloxacin is a reasonable empiric outpatient treatment option, but
resistance to ciprofloxacin has been increasing in the County. In the first five months of 2018, 17% of isolates tested have been ciprofloxacin-resistant. In June of this year, the Centers for Disease Control and Prevention (CDC) reported an increasing number of
isolates that test susceptible to ciprofloxacin (minimum inhibitory concentration [MIC] values of 0.12-1 μg/mL), but harbor one or more resistance mechanisms. The clinical significance of this low-level resistance is uncertain. But given this information, combined with the resistance patterns seen in
isolates in the County, providers should be mindful that ciprofloxacin will not always be effective.
Azithromycin is another appropriate empiric treatment option. Most clinical laboratories do not test for azithromycin susceptibility, but like ciprofloxacin,
isolates that are azithromycin-resistant are increasingly being identified nationally.
Resistance of both
isolates to ampicillin and trimethoprim/sulfamethoxazole remains high in the County, neither should be used for empiric initial therapy.
Providers should monitor patients placed on antibiotic treatment for potential treatment failure. If not obtained initially, clinicians should submit a stool specimen for antimicrobial susceptibility testing if treatment failure is suspected. Providers should also report any possible clinical failures with use of ciprofloxacin or azithromycin to Orange County Public Health.