To the Editor—Shigellosis is a highly infectious bacterial infection with symptoms from mild, self-limiting gastroenteritis to severe illness. Shigella flexneri and S. sonnei are the 2 most common species in British Columbia. ¹ Most cases (62%) in British Columbia are travel related. Domestic outbreaks in daycares and through sexual contact are common owing to type of contact and low infectious dose for Shigella species—10 or fewer organisms.Reference Kothary and Babu ² Outbreaks in homeless populations are a concern owing to client vulnerability and risk of widespread transmission from inadequate sanitation. Healthcare workers are considered at high risk of transmission to others if they are ill with shigellosis; however, transmission of Shigella to healthcare workers is rarely documented in outbreak investigations. In April 2015, British Columbia public health officials investigated a shigellosis outbreak among persons associated with a homeless shelter and their attending healthcare providers.

Patient A, a middle-aged man with medical history including cirrhosis and hepatocellular carcinoma secondary to hepatitis B and C infection, developed bloody diarrhea and abdominal cramping on March 31, 2015, that persisted for 1 week before hospital admission on April 7, 2015. Episodes of uncontrollable loose bowel movements resulted in fecal contamination of his living environments, including a shelter day-program. Blood and stool cultures collected on April 7 grew S. sonnei. He was treated with ceftriaxone but remained in the hospital until April 30, 2015, owing to complications of his underlying medical conditions.

Patient B, a middle-aged man with a history of injection drug abuse and chronic hepatitis C, developed fever, confusion, and profuse diarrhea on April 1, 2015, while at the same shelter day-program patient A attended. Emergency services attended to him at the shelter and transported him to the hospital. On admission, he was covered in stool, was febrile (temperature, 39°C), and had delirium and decreased level of consciousness requiring sedation and intubation. Stool cultures collected on April 3 grew S. sonnei. He was treated with piperacillin/tazomycin while in the hospital. He left the hospital against medical advice on April 4.

Patient C, a previously healthy middle-aged man, was part of the first responder team who attended patient B at the shelter on April 1, including transferring and handling his soiled clothes. Patient C sprayed his contaminated boots, removed his gloves, and cleaned his hands with alcohol-based hand sanitizer. He developed symptoms of bloody diarrhea and abdominal discomfort on April 4; stool culture collected on April 11 grew S. sonnei.

Patient D, a previously healthy middle-aged healthcare worker, attended to patient B in the emergency department on April 1. She donned gown and gloves and followed hand hygiene per usual contact precautions but noted that patient B’s thrashing was spreading feces widely. She developed diarrhea on April 3; stool culture collected on April 10 grew S. sonnei.

Pulsed-field gel electrophoresis using both Xba and Bln enzymes are routinely performed on all S. sonnei in British Columbia using PulseNet Canada protocol. ³ Pulsed-field gel electrophoresis patterns of S. sonnei, subgroup D, for 3 of the 4 ill persons’ stool specimens were identical by both enzymes. Patient C had a closely related Xba pattern and identical Bln pattern. Susceptibility testing showed varying multidrug-resistance patterns, but all 4 isolates were resistant to ciprofloxacin and trimethoprim/sulfamethoxazole. Isolates of patients A and C were susceptible to ampicillin and ceftriaxone, whereas those of patients B and D were not. Patient B’s isolate was initially reported as resistant to azithromycin, but according to Salmonella Typhi minimal inhibitory concentration breakpoints for azithromycin sensitivity against Shigella, both patients B and D were sensitive to azithromycin.

We evaluated the potential exposures from each patient and conducted an environmental assessment to determine the risk for further disease transmission. Public health actions at the shelter included active case finding of other clients and staff, which revealed no additional cases. Shelter management and outreach medical clinic staff received education on transmission of diarrheal illness, and signage was posted to reinforce good personal hygiene. Thorough disinfection and cleaning of the shelter were undertaken.

Staff at the local hospital were notified of the outbreak and alerted to contact public health immediately with any additional suspect cases. All cases of shigellosis reported from March 25 through April 20, 2015, were reviewed for potential linkage to this cluster.

S. sonnei generally causes milder diarrheal illness compared with other Shigella species.Reference Heiman and Bowen ⁴ The severity of illness in patients A and B was likely related to chronic comorbid conditions, a consideration for treating shigellosis in a homeless population. Incomplete treatment of patient B posed a risk to the patient and risk of transmission of a multidrug-resistant strain. Recent reports that 87% of S. sonnei isolates in the United States were nonsusceptible to ciprofloxacin have raised awareness of drug resistance and the need for rational antibiotic treatment.Reference Bowen, Hurd and Hoover ⁵ Laboratory testing of isolates from all 4 cases in this outbreak showed nonsusceptibility to ciprofloxacin and additional resistance to typical first-line antibiotics. However, without Clinical and Laboratory Standards Institute guidelines for azithromycin susceptibility interpretation, testing for azithromycin is not routine and inconsistently reported.

Transmission to 2 healthcare workers, despite appropriate contact precautions, highlights the increased risk from explosive diarrhea due to shigellosis. Contact precautions are the recommended standard but droplet precautions, including foot coverings, masks, and goggles, may be more appropriate for managing a patient with uncontrolled diarrhea.Reference Siegel, Rhinehart, Jackson and Chiarello ⁶ Soap and water hand hygiene may be more effective than alcohol-based hand rub in removing gross contamination on hands and forearms.Reference Pickering, Davis and Boehm ^{7 ,} Reference Todd, Michaels, Holah, Smith, Grieg and Bartleson ⁸