1967. Outbreak of extremely drug-resistant Shigella sonnei infections among men who have sex with men (MSM), derived from travel-associated outbreak of ciprofloxacin-resistant shigellosis—United States, May 2014 – April 2015
Session: Oral Abstract Session: Emerging Public Health Threats
Saturday, October 10, 2015: 2:15 PM
Room: 25--ABC
Background: Multidrug resistance is common among shigellae, but rates of ciprofloxacin and azithromycin (AZM) resistance have been <5% in the United States.  Clinical standards for AZM susceptibility among shigellae do not exist. We describe an outbreak of ciprofloxacin-resistant shigellosis linked to travel, and a secondary outbreak with elevated AZM minimum inhibitory concentrations (MICs) in MSM.

Methods: We defined a case as 1) S. sonnei infection with one of 5 highly similar PFGE patterns between May 21, 2014 and Apr 30, 2015; OR 2) S. sonnei infection resistant to ciprofloxacin in a resident of or visitor to San Francisco between Nov 1, 2014 and Apr 14, 2015. We identified cases using pulsed-field gel electrophoresis (PFGE) data in CDC’s PulseNet, and via case reports to the San Francisco Department of Public Health. Antimicrobial susceptibility (AS) data were summarized if available.

Results: PulseNet identified 179 cases in 34 states and Puerto Rico. Approximately 40% were associated with international travel, particularly to Hispaniola and India, and several MSM clusters were detected. Fourteen of the cases identified by PulseNet, and another 117 cases without PFGE data, were part of an outbreak of ciprofloxacin-resistant shigellosis largely among the homeless in San Francisco. Of 173 isolates with AS results, 154 (89%) were nonsusceptible to ciprofloxacin. Of 22 isolates tested by CDC, five (MT, 4; IL, 1) were resistant to ampicillin, trimethoprim/sulfamethoxazole, and ciprofloxacin; had AZM MICs >16 μg/ml; and harbored macrolide resistance genes mphA and ermB. Of the five patients, two reported diarrhea for >2 weeks and three identified as MSM.

Conclusion: At least 296 people from 34 states became ill during this outbreak of ciprofloxacin-resistant shigellosis, and a sub-cluster emerged with nonsusceptibility to AZM and ampicillin.  Clinicians should request stool cultures and AS when they suspect shigellosis; base treatment, if needed, on AS; and counsel patients about shigellosis prevention. Facilitation of care-seeking and hygiene among high-risk groups like travelers, the homeless, diapered children, and MSM can prevent spread. Clinical standards for AZM susceptibility testing would improve surveillance and patient management.

Anna Bowen, MD, MPH1, Cora Hoover, MD, MPH2, Akiko Kimura, MD3, Yvette Khachadourian, MPH4, Dana Fejes, MPH5, Alicia Siston, PhD, MPH6, Tanya Libby, MPH7, Sara Ehlers, MPH2, Jacqueline Hurd, MPH1, J. Corbin Norton, BS1, Amelia Bicknese, BS1, Davina Campbell, MS, MPH1 and Shamika Smith, MPH6, (1)Centers for Disease Control and Prevention, Atlanta, GA, (2)San Francisco Department of Public Health, San Francisco, CA, (3)California Department of Public Health, Los Angeles, CA, (4)Philadelphia Department of Public Health, Philadelphia, PA, (5)Montana Department of Public Health and Human Services, Helena, MT, (6)Chicago Department of Public Health, Chicago, IL, (7)California Emerging Infections Program, Oakland, CA


A. Bowen, P&G: Collaborator , Research support

C. Hoover, None

A. Kimura, None

Y. Khachadourian, None

D. Fejes, None

A. Siston, None

T. Libby, None

S. Ehlers, None

J. Hurd, None

J. C. Norton, None

A. Bicknese, None

D. Campbell, None

S. Smith, None

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