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What is Shigella (and Why Should You Care)?
Shigella infections (aka. shigellosis) kill approximately 700,000 people a year, mostly in developing countries. An important cause of what was traditionally called “bacterial dysentery,” the World Health Organization (WHO) calls shigellosis “the most important cause of bloody diarrhea worldwide,” with at least 80 million illnesses every year. Shigellosis is highly contagious (Ingesting as few as 10 bacteria can transmit infection.) and also highly prone to drug resistance, making the more severe infections that require antibiotics increasingly difficult to treat. As with all drug resistance, overuse of antibiotics is making the problem worse.
Shigellosis spreads quickly in group settings like childcare facilities, military units, and homeless shelters. In an attempt to limit the spread of disease, local health departments are often guided by state laws to ban infected people from working as food handlers, healthcare workers, or childcare providers until the infected person is no longer contagious.
With diarrheal diseases in general, those people most at risk have compromised immune systems and/or are young children. Approximately 70% of cases and 60% of deaths are among children under 5 years old. WHO suspects that less than 1% of worldwide cases are ever seen in a hospital.
This year, bad news about drug-resistant shigellosis just keeps coming.
A dispatch in the July 2015 issue of the CDC journal Emerging Infectious Diseases , about a drug-resistant outbreak of Shigella sonnei in a South Korean daycare is just the latest in a series of warnings about emerging drug resistance among Shigella species.
On April 2, 2015, the US Centers for Disease Control and Prevention (CDC) issued a press release warning of multi-drug resistant Shigellosis circulating in the United States, with repeated introductions by travelers from abroad. In the May 2015 edition of Emerging Infectious Diseases, Irish physicians warned about a global trend of increased ciprofoxacin (Cipro) resistance among Shigella infections obtained during travel to India.
Most concerning to Americans, on June 4, 2015, the CDC’s emergency alert system, the Health Alert Network (HAN) raised the alarm that ciprofloxacin-resistant, azithromycin-resistant and XDR (extremely drug-resistant) Shigella are circulating among the MSM (men who have sex with men) of San Francisco, spreading to MSM clusters in Illinois, Minnesota and Montana. On June 5, the CDC’s Morbidity and Mortality Weekly Report (MMWR; 64 (21); 597-598) featured an article discussing azithromycin-resistant Shigella sonnei outbreaks among MSM in the Chicago and Minneapolis-St. Paul metros in 2014.
A Little Bit More About Shigella
There are four different species in the bacterial genus Shigella– S. dysenteriae (aka. Serogroup A), S. flexneri (serogroup B), S. boydii (Serogroup C), and S. sonnei (Serogroup D). The most severe illness and the cause of the biggest, deadliest epidemics is S. dysenteriae, serotype 1 (Sd1). The least pathogenic and also most common in the developing world is Shigella sonnei. Shigella symptoms usually emerge 1-2 days after exposure, and the illness lasts generally 5-7 days. Recovery is usually complete, although it may take several months for bowel habits to return to normal.
Like most diarrheal illnesses, shigellosis is spread by ingesting the bacteria from the feces (“poop”) of an infected person, generally through contaminated food, contaminated water, contaminated surfaces, or by sex practices that make ingestion of small amounts of infected feces more likely (oral-genital or oral-anal sex).
United States drug resistance with common foodborne illnesses
According to the CDC, there are 500,000 shigellosis cases and approximately 40 deaths annually are in the United States. In the U.S., resistance to ciprofloxacin (Cipro) and trimethoprim-sulfamethoxazole (Bactrim, Septra) has been steadily rising since 2006. Overall, the National Antimicrobial Resistance Monitoring System (NARMS, who monitors drug resistance among diarrheal diseases) has US cipro-resistance among Shigella species at approximately 3%. However, in the course of the last year, CDC and local health jurisdictions have investigated clusters of particular genotypes of Shigella in Massachusetts, California and Pennsylvania where nearly 90 percent of the cases tested were resistant to ciprofloxacin (Cipro), the first choice to treat Shigella infections among adults in the United States.
The National Antimicrobial Resistance Monitoring System (NARMS) released the report about its 2013 data on June 9, 2015. NARMS monitors antibiotic resistance among enteric (intestinal) bacteria. NARMS does this by collecting data about human infections via the CDC, about contaminated retail meats via the FDA, and about infected food animals via the USDA.
According to the 2013 NARMS Annual Human Isolates Report, multidrug resistance (MDR, defined as resistance to three or more classes of antibiotics) among Salmonella overall are holding steady at approximately 10%, although some isolates are 46% MDR. Of Campylobacter infections, one in four are already resistant to quinolone antibiotics like Cipro.
WHAT YOU CAN DO
Healthcare providers: Per CDC guidelines, reserve antibiotics for severe diarrhea, utilizing Pepto-Bismol for milder cases. Get cultures with drug sensitivities to guide treatment decisions.
Travelers: Use caution in travel eating, particularly cold or raw foods, including ice. Eat most foods steaming hot. Eat fruits that can be peeled and peel them yourself. For more information on safe eating while traveling, see the CDC page for Traveler Food and Water Safety.
Workers: If you work in food service, healthcare or childcare do not work when ill.
Sex partners: Avoid sex while ill with diarrhea and for several weeks afterward. Particularly, avoid any practices that make ingestion of feces more likely.
Swimmers: Avoid swimming while sick with diarrhea and do not allow children to share public swimming pools while ill. Avoid ingesting water from swimming pools or from freshwater sources (i.e. lakes, streams).
As with all diarrheal diseases, the best way to prevent disease spread is thorough hand washing with soap and water for at least 20 seconds after going to the bathroom, before preparing food, and before eating.
SOURCES FOR “MORE BAD NEWS ABOUT SHIGELLA INFECTIONS”
CDC press release re: MDR Shigellosis, April 2, 2015
Emerging Infectious Diseases, July 2015: South Korean daycare outbreak
Emerging Infectious Diseases, May 2015: Cipro resistance associated with India
June 2015 Health Alert Network advisory: Shigellosis among American Men Who Have Sex with Men (MSM)
MMWR, June 2015: Drug-resistant Shigellosis among MSM in Chicago and Minneapolis-St. Paul
MMWR April 2015: Domestic and imported Cipro-resistant Shigella
CDC: Prevention of Shigella infections among Men Who Have Sex with Men
CDC 2016 Yellow Book, Chapter 3: Infectious Diseases Related to Travel, Shigellosis
U.S NARMS 2013 human isolates report (released June 2015)
MORE ABOUT SHIGELLA AND ABOUT DRUG RESISTANCE
National Enteric Disease Surveillance: Shigella
CDC report: Antibiotic resistance threats in the United States, 2013 (This pdf is amazing.)