Australian researchers are sounding the alarm over cases of a highly infectious intestinal illness that appear to be resistant to all forms of standard oral antibiotic treatment.
The disease is called shigellosis, a form of dysentery. So far, most cases have involved gay and bisexual men in the Australian state of Victoria, the researchers said.
“Shigellosis is an acute diarrheal disease,” explained study lead author Dr. Deborah Williamson, who directs microbiology at Royal Melbourne Hospital in Melbourne. Caused by a bacteria that infects the intestines, it’s thought to cause roughly 190 million cases of diarrhea around the world each year.
The illness “is highly infectious,” Williamson added. She characterized shigellosis as the most infectious of gastrointestinal pathogens, noting that exposure to just a small dose of the bacteria can make a person very ill.
In less-developed countries with poor sanitation, children are often the most vulnerable to shigellosis, as the infection is typically spread through tainted food and water. It’s much less of a threat in wealthier nations, where it is instead typically spread by close sexual contact, particularly among gay and bisexual men.
Prior to 2018 Australia had seen just a handful of cases. But since 2018, Williamson’s team has identified more than 170, mainly among gay men.
“Oral antibiotics is the current standard of care,” said Williamson, typically given as an outpatient regimen of either ciprofloxacin or azithromycin.
And while not all shigellosis patients end up needing medication, “it is important to treat some patients, such as those who have a deficient immune system, or those with severe disease, or those who are at high risk of passing the infection on, [including] food handlers,” she said.
However, since 2018, “we identified the emergence of a strain of Shigella that is resistant to all oral antibiotics,” said Williamson, who also serves as the deputy director of the Microbiological Diagnostic Unit at Melbourne’s Peter Doherty Institute for Infection and Immunity.
Genetic testing traced the Australian strain to one previously linked to travel in India.
“Previously, this strain has only been detected a handful of times around the world,” Williamson said. “But here we found over 170 cases of infection with this strain in Melbourne.” During the investigation — which ran from February 2018 through May 2019 — nearly 94% of these antibiotic-resistant cases occurred in men.
Dr. Bradley Ford is clinical associate professor of pathology and director of clinical microbiology with University of Iowa Hospitals and Clinics in Iowa City. He wasn’t involved in the new study, but said it highlights the growing threat of bacterial resistance to antibiotic drugs.
“Unfortunately, reports like this suggest that Shigella is becoming resistant to all of the oral antibiotics that are commonly used to fight it,” Ford said, “probably partly due to overuse for diarrheal illness, urinary tract infections, pneumonia and other infections.
“This paper also suggests that resistant Shigella is likely to travel across the world,” he said. “This places us all at risk of getting Shigella dysentery that is incurable with pills. But patients won’t know that their Shigella is resistant until several days have passed, at which point they may be sicker and need intravenous antibiotics.”
When oral antibiotics fail, doctors have the option of administering another antibiotic called ceftriaxone intravenously, Williamson’s team said.
Right now, it appears that the new strain is primarily being spread in the gay and bisexual community. But that should be worrisome for other countries, given that this is also one of the main ways this disease is spread across borders.
“The rapid emergence of this strain in our setting, in plain sight, is of major concern,” Williamson said, “both from a clinical and public health perspective. And it further highlights the need for a concerted international public health effort to tackle antibiotic resistance.”
Ford agreed, and said that the rampant overuse of antibiotics has helped create the problem.
“The best thing for patients and doctors to do is to be mindful that not all infections need antibiotics, and to work together to use the right drugs at the right time, or no antibiotics at all,” he said.
Williamson and colleagues published their findings in the Dec. 19 issue of the New England Journal of Medicine.
There’s more information about shigellosis at the U.S. Centers for Disease Control and Prevention.
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