CDC Warns About Drug-Resistant Stomach Bug on the Rise in the US: What to Know

A drug-resistant strain of Shigella bacteria is behind a growing number of infections that can cause severe, bloody diarrhea, among other symptoms, the Centers for Disease Control and Prevention (CDC) said last week.

The CDC issued a health advisory to warn clinicians and the public about this increase in extensively drug-resistant (XDR) shigellosis, the illness caused by the Shigella bacteria. By 2022, 5% of all shigellosis cases were caused by XDR strains, as compared to 0% in 2015.

Shigellosis is not an uncommon disease—about 450,000 people get it annually, and most stains can also be targeted with common antibiotics. The XDR strain mentioned in the health advisory, however, is different.

“Essentially, it’s resistant to all of the commonly [used] oral and IV empiric antibiotics,” Naeemah Logan, MD, lieutenant commander and medical epidemiologist for the CDC, told Health. “That’s concerning because that means providers don’t have options to treat Shigella.”

The demographics of those most affected by this shigellosis strain are also a bit more uncommon. Typically, shigellosis affects children ages 1 to 4. But of the 239 XDR shigellosis cases recorded since January 2015, over 80% were found in adult men, and among the 41 people who answered questions about sexual activity, 88% said they’re part of the population of men who have sex with men (MSM).

In most cases, the body can fight off the Shigella bacteria on its own, without the use of antimicrobial drugs, though people with weakened immune systems can, in rare cases, see life-threatening infections if the bacteria gets into the bloodstream.

Here’s what experts had to say about the Shigella bacteria, why shigellosis cases are growing among this certain population in the U.S., and what people can do in their everyday lives to keep safe.

What Makes XDR Shigellosis Different from Other Forms of Shigellosis?

XDR shigellosis is not a new type of bacteria, but it’s a strain of Shigella that has evolved to escape the most common forms of antibiotics, explained Karen Kotloff, MD, professor and head of the division of pediatric infectious disease at the University of Maryland School of Medicine.

“When bacteria are exposed to antibiotics, there is some at least temporary survival advantage for the bacteria to acquire mechanisms that allow them to be resistant to the antibiotic,” she told Health. “In areas where there’s high antibiotic [or] multiple antibiotic use, it’s to their advantage to have multiple resistance.”

All types of shigellosis—drug-resistant or not—cause the same symptoms. These usually include fever, abdominal cramps, and painful diarrhea that can have blood or mucus in it, Dr. Kotloff said. People may also experience tenesmus, or the feeling that you still need to pass stool even when your bowels are empty. Most of these cases are self-limiting, which means the body can typically rid the infection on its own.

In typical shigellosis cases, those who seek treatment are prescribed an antibiotic (azithromycin, ciprofloxacin, etc.) to help clear the infection quicker, cutting down time someone has symptoms by two days. But with XDR shigellosis, the bacteria won’t respond to the most commonly-prescribed antibiotics.

That leaves healthcare providers with fewer options to help their patients. A team of U.K. researchers outlined a strategy using two less common antibiotics that these XDR Shigella do not seem resistant to. But the CDC does not yet have a recommended treatment plan for people who do have XDR shigellosis.

“It is an infection that can be shortened and quickly improved with antibiotics. And the problem with antibiotics is that each time a new antibiotic is introduced […] in about 10 years, the Shigella learn to be resistant to it. And so we just keep going through antibiotics,” Dr. Kotloff said. “That gets very scary for people who need treatment who have more severe disease.”

The rise of these XDR Shigella means that for most who get them, they may not receive antibiotic treatment, or their doctor may just be more selective about which specific types of antibiotics they’re prescribing.

But for those who are immunocompromised in some way—those with HIV, for example, or some other medical condition—the growing number of XDR shigellosis could be a bigger cause for concern. If the Shigella can’t be treated by antibiotics, in very rare cases it could enter the bloodstream, Dr. Logan explained, which can require hospitalization and can be life-threatening.

“It’s difficult for clinicians not to give antibiotics to someone who is suffering an illness when you have antibiotics that work,” Anthony Maurelli, PhD, researcher and professor of environmental and global health at the University of Florida, told Health. “But the downside is that when you give antibiotics, some bacteria survive and they mutate.”

How Does a Person Get Shigellosis?

Antibiotics have to be used sparingly and may not always work depending on the mutations of the Shigella a person is infected with, so the natural solution would be to focus on eliminating spread of the infectious diarrhea. But that’s not always so simple with a highly infectious bacteria like Shigella.

“Shigella is so incredibly transmissible,” Dr. Logan said. “It has a very low infective dose—less than 10 organisms.”

Shigella is spread through the fecal-oral route, or when a person comes into contact with the infected stool of another person. This can happen directly through person-to-person contact (including sexual contact), or indirectly through contaminated food or drinks. Large public settings, such as daycares or assisted-living facilities are most at-risk.

“You can see how easy it would be to transmit that to other individuals in that same setting,” he said. “You’ve introduced a highly infectious, highly transmissible pathogen into an environment where it’s easy to spread because of the underdeveloped personal hygiene habits of those children.” 

The bacteria can survive the stomach’s acidic environment, Maurelli said, which allows it to reach the large intestine where it then causes inflammation in the large intestine—that’s what causes the diarrhea, cramping, and fever. An infected person can continue to spread the bacteria through their stool for weeks after the illness.

The CDC said the current rise in XDR shigellosis cases is showing up mainly among MSM communities, those experiencing homelessness, people with HIV, and international travelers. A large driver of this transmission in the MSM community seems to be sexual encounters, Dr. Logan said.

“There’s been many gastrointestinal (GI) illnesses that have a higher prevalence in men who have sex with men—not just shigellosis, but even things like giardia, for example, which is a parasitic disease,” Amesh Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, told Health. “That has to do with sexual behaviors and exposure to a GI pathogen from oral-anal contact. And that’s likely what’s occurring in these situations.”

Managing and Preventing Infection

Though the increase in XDR shigellosis cases has some experts concerned, the CDC health advisory is just another reminder to clinicians and everyday Americans to educate themselves so that the bacteria can be dealt with in the best way possible.

If a person suspects they have shigellosis by way of symptoms or contact with a person who tested positive for the illness, they should seek medical treatment; especially if that person is immunocompromised or has other underlying health issues.

(It’s likely that most people will seek out medical care for shigellosis, as it can be incredibly painful and the severe, bloody diarrhea can be alarming to witness, said Louise Francois Watkins, MD, MPH, medical epidemiologist for the CDC.)

To diagnose a Shigella infection, a healthcare provider will collect a stool sample to test and determine what’s causing their symptoms. That sample may also undergo antimicrobial susceptibility testing to determine if there might be any antibiotics that may work to fight Shigella, Dr. Watkins said.

If antibiotics are necessary or helpful, they will be prescribed; if they aren’t, a healthcare provider will guide patients on other ways to help manage their symptoms at home.

“It’s really important with any diarrheal disease, including Shigella, to maintain a good fluid and electrolyte balance,” she told Health. “You can drink an official solution of oral rehydration salts, but also things like Gatorade or those types of products that are sold just over the counter, can be really helpful.”

Certain body positions—like the fetal position, or lying down on one’s side—or using heating pads may also be helpful, Dr. Watkins added.

As far as prevention goes, good hygiene is a must—washing hands frequently, especially if a person thinks they may have come into contact with stool, is a great way to prevent accidentally ingesting Shigella, experts said.

But it’s also crucial that all people—particularly those in the MSM community—commit to safe sex practices, including avoiding sexual encounters if a person is having any shigellosis symptoms and for two weeks afterwards.

“Our goals are not to terrify anyone. XDR Shigella is still a rare illness in the United States,” Dr. Watkins said. “But there’s a few concerns when we do see the rapid emergence of resistance like this. We know that what happens in Shigella can also happen in other pathogens. So we’re asking both members of the general public and healthcare professionals to be aware.”