The CDC is warning about a steep increase in the number of infections from antibiotic-resistant infections from Shigella, which is often foodborne.

In a health advisory from the Centers for Disease Control and Prevention’s Health alert Network (HAN), it was revealed that 5 percent of Shigella infections, known as Shigellosis, were caused by resistant strains, up from zero percent in 2015.

“Shigellosis is a gastrointestinal condition caused by one of the four species of Shigella bacteria: Shigella sonnei, S flexneri, S boydii, or S dysenteriae. Symptoms range from mild diarrhea to severe dysentery. Most cases are self-limiting, but antibiotics are frequently used to treat more severe symptoms and reduce shedding, which can help limit transmission,” according to the CDC.

The CDC says that, in addition to limiting the treatment options for patients, the XDR Shigellastrains are a concern because they can spread antimicrobial resistance genes to other enteric bacteria.

“Given these potentially serious public health concerns, CDC asks healthcare professionals to be vigilant about suspecting and reporting cases of XDR Shigellainfection to their local or state health department and educating patients and communities at increased risk about prevention and transmission,” the agency said.

The CDC alert was prompted by multiple reports of XDR Shigella from state health departments around the country. CDC officials said a key factor in the alert was the fact that clinicians were reporting that they did not know how to treat antibiotic-resistant infections.

The disease caused by Shigella, shigellosis, is often associated with food or water that has been contaminated by human feces. It only takes microscopic amounts of human waste to contaminate food or beverages. Shigellosis is highly contagious and can easily spread. It causes an estimated 450,000 infections every year in the United States, according to the CDC. 

“The CDC notes that historically, drug-susceptible Shigella has predominantly affected young children ages 1 through 4 in the United States, with spread commonly seen in daycare settings among children who haven’t been toilet-trained,” according to the agency.

And because Shigella is so easily transmissible, there is concern about the wider spread of XDR strains beyond people in vulnerable populations, who may work in the food service industry or healthcare or take care of young children or the elderly, Louise Francois Watkins, MD, MPH, told CIDRAP News of the University of Minnesota.

It does seem that we’ve seen a demographic shift towards more cases that are occurring among adult men, said Watkins. And while the CDC doesn’t routinely collect sexual history when it receives case reports, Watkins noted that in specific outbreak investigations, male patients have been reporting new sexual partners.

According to the agency, the median age of case patients was 42 years, and of the 232 patients with available information, 82 percent were men. Of the 41 patients who answered questions about sexual activity, 88 percent reported male-to-male sexual contact.

And because Shigella is so easily transmissible, there is concern about the wider spread of XDR strains beyond people in vulnerable populations, who may work in the food service industry or healthcare or take care of young children or the elderly, Watkins added.

“This is not a disease that anyone is going to be completely safe from just because of the nature of the way it can spread through different modes of transmission,” she said.

Messages for clinicians

The CDC is urging clinicians to consider shigellosis in the diagnosis of acute diarrhea, especially in higher-risk groups such as MSM, the homeless, international travelers, people who have HIV, and young children. They also want clinicians to ask about relevant exposures and social history and to obtain cultures for further analysis.

The HAN health advisory notes that, because there are no data from clinical studies of XDR Shigella treatment, the CDC does not have recommendations for optimal antibiotic treatment. XDR strains can be resistant to both the standard empiric treatments — azithromycin, ciprofloxacin, or ceftriaxone — and alternative options such as trimethoprim-sulfamethoxazole and ampicillin. But the agency wants clinicians to know that with the increase in XDR infections, they need to be careful about which antibiotic they prescribe.

“Part of our messaging in this health alert is that we want healthcare professionals to be aware that if you try to make a guess about which antibiotic is going to work for Shigella, the odds are really increasing that you’re going to guess wrong,” Watkins said.