Diarrhea-causing superbug is on the loose; stirs up trouble in Los Angeles

A dangerous diarrhea-causing superbug is spreading fast and stirring up trouble in Los Angeles. Researchers have managed to track down a worrying new strain of Shigella bacteria in the area. As per their research, the superbug in question, can resist almost every antibiotic thrown at it.
Scientists at the University of California, Los Angeles, conducted the study recently. The study looked at an unusual cluster of Shigella cases discovered between 2023 and 2024. Each of the cases were found to be carrying an extensively drug-resistant (XDR) strain of the bacteria.

Although the victims of the bacteria have recovered, the researchers are far from diluting the potential of harming capabilities of the bacteria.
They have tagged their discovery as ‘alarming’, especially since it’s likely that the superbug is still actively spreading in LA and possibly elsewhere.

Shigella is a genus of bacteria that is Gram negative, facultatively anaerobic, non–spore-forming, nonmotile, rod shaped, and is genetically nested within Escherichia. The genus is named after Kiyoshi Shiga, who discovered it in 1897.

Shigella infection symptoms usually begin 1 to 3 days after exposure to the bacteria. In most cases, the infection clears up on its own within a week. However, in some people, especially young children and the elderly, the diarrhea can be so severe that they need to be hospitalized.
Symptoms: Diarrhea that can be bloody or prolonged, fever, stomach pain, and feeling the need to pass stool even when the bowels are empty. Symptoms usually last about 5 to 7 days.
Spread: Shigella can spread through contaminated food or water, contact with someone who is sick, sexual activity with a sick person, or contaminated surfaces or objects. The germ usually spreads through contaminated food or drink, but it can also be transmitted sexually. This latter form of transmission tends to occur more frequently through anal contact among men who have sex with men.
Risk groups: Shigella kills about 200,000 people worldwide annually; in the U.S., it’s thought to infect about a half million people every year, with thousands hospitalized as a result. While most of the shigella infection cases only cause a week-long bout of misery, which clears up on its own, the infection can rarely trigger severe, even fatal complications, particularly in people who have underdeveloped immune systems, such as very young children. Travelers to certain foreign countries, people who have weakened immune systems, and people exposed to human feces (poop) through sexual contact are at greater risk.
Prevention: Don't share towels or linen with the infected person, and the infected person shouldn't prepare any meals at home for other family members.
Treatment: Treatment consists mainly of replacing fluids and salts lost because of diarrhea. Antidiarrheal drugs should not be used.
Antibiotics are used to treat severe Shigella infections or to keep infections under control in those at higher risk of illness. But as with many other bacteria, Shigella bacteria have increasingly learned how to fend off the most common antibiotics used against it. The most concerning strains are extensively drug-resistant, meaning that they can overcome a wide variety of antibiotics.
Diarrhea can be caused by a bacteria, virus, food intolerance, food allergy and a range of other factors. The main sign of the condition is stools that are loose and watery. You may also need to go to the bathroom more often. Diarrhea last 1 or 2 days and goes away on its own. If diarrhea lasts more than two days it may mean you have a more serious problem. It is important to take rest, stay hydrated, and non-spicy foods while recovering from diarrhea. Drink plenty of clear fluids, such as water, and avoid drinks with lots of sugar.


In their paper, published this month in the Journal of Infection Control, UCLA scientists detailed the discovery of a new XDR strain of Shigella sonnei in three of their patients. According to the report, the three cases were detected within a three-month period between 2023 and 2024. All three infections involved men who had a history of having sex with other men, with one patient reporting that a recent sexual partner of theirs had been diagnosed with Shigella a week earlier. Initial lab tests revealed that they carried an XDR strain, formally defined as having resistance to the antibiotics azithromycin, ciprofloxacin, ceftriaxone, trimethoprim-sulfamethoxazole, and ampicillin.
The ULCA scientists conducted a genetic analysis of the samples collected from their patients and found that all three patients carried a similar strain, though it was noticeably distinct from past XDR strains identified in other parts of the world. That likely means this version has been evolving and spreading in the area for some time, the researchers say.
As per the researchers, “The discovery of a novel XDR S. sonnei actively spreading in Los Angeles is alarming.”
The cases of infection were quite treatable or otherwise cleared up on their own. One person did develop a severe infection and ended up in intensive care as a result. But the real-time detection of XDR resistance in this case prompted the doctors to switch to a different recommended drug that appeared to work and the patient eventually recovered fully.


The emergence of XDR Shigella in the U.S. and worldwide is a serious and growing public health concern. These cases are way more difficult to treat than a typical Shigella infection. The delay in finding the right drug that works against an XDR strain can potentially be fatal.
Last year, scientists from the Centres for Disease Control and Prevention (CDC) issued a public health advisory over the superbug, that reported – about 5% of Shigella cases reported to the agency in 2022 were caused by XDR strains, up from 0% in 2015. Given these latest cases, the problem has likely only worsened since then. And the UCLA scientists say more has to be done to identify and curtail the spread of these dangerous bacteria.
As per the scientists, “These cases highlight the rapid expansion of XDR Shigella in the U.S. and urgent need for appropriate detection and management.”