A drug-resistant strain of a highly contagious sexually-transmitted bowel infection that commonly causes gastro is circulating in Victoria.
The superbug strain of shigella bacteria, identified by researchers at the Doherty Institute in Melbourne, has been found to be resistant to all oral antibiotics with the vast majority of cases being suffered by men who have sex with men.
A drug-resistant strain of a highly contagious sexually-transmitted bowel infection that commonly causes gastro is circulating in Victoria, with the vast majority of cases being suffered by men who have sex with men.Credit: Alamy
Their findings, published in the New England Journal of Medicine , reveal there were 171 cases of the drug-resistant bacteria reported from early 2018 to mid-2019, compared to just a handful of cases for the same period the year before.
While anyone can contract the bacterial infection, researchers have warned it is far more easily transmitted through the sexual practices of gay and bisexual men. It is also more common among travellers returning to Australia.
Shigellosis, the bowel infection that results from shigella exposure, can result in vomiting, stomach cramps, diarrhoea, fever and nausea. Symptoms can appear between 12 hours and four days after exposure, and can last between four and seven days. It is estimated to cause 190 million cases of diarrhoea globally a year.
Researchers are not yet sure what is behind the outbreak, but they suspect it may be linked to a rise in casual sex through online dating and reduced fear of contracting HIV due to the increase in people taking pre-exposure prophylaxis medication known as PrEP. A jump in global travel is also thought to be linked to the surge.
"We know that the incidence of shigella has gone up, not just in Victoria, but across Australia over the past 10 years and it is a major public health concern," lead researcher and University of Melbourne Professor, Deborah Williamson, said.
"These things can seemingly emerge from nowhere and spread very rapidly. One of the most concerning aspects of our data is that 80 or so years ago we saw just a tiny handful of these very drug resistant cases and now it is becoming one of the more dominant strains of shigella."
To date this year, there have been 608 cases of shigella bacteria reported to the Victorian health department, compared to 520 for the same time last year.
As part of the study, researchers used genome sequencing to examine all reported cases of shigella, finding the clusters of the disease that were resistant to antibiotics were linked to each other.
“Our findings strongly suggested person-to-person transmission within specific sexual networks,” Professor Williamson said.
"Raising awareness of shigella as an STD is a key first step. Not everybody thinks of shigella as a sexually transmitted pathogen and they often don't think diarrhoea can be caused by a sexually transmitted disease so improved messaging around that is really important."
People with HIV or who have an otherwise compromised immune system may also experience more severe illness.
Professor Williamson, who is deputy director of the Microbiological Unit Public Health Laboratory at the Doherty Institute, said shigella was the most infectious of all gastrointestinal bacteria.
“Just two or three bacteria can make you really sick," Professor Williamson said.
People suffering the drug-resistant strain of shigellosis may need intravenous antibiotics to kill the infection.
Victoria’s Chief Health Officer Brett Sutton said it was of "enormous concern" that cases of shigella were unable to be treated through oral antibiotics and instead required hospitalisation.
“Antibiotic treatment should be reserved for priority cases, such as those who are immuno-suppressed, those who have severe disease and people who work in high-risk settings for onward transmission," Dr Sutton said.
He said suspected cases of shigellosis should have stool samples sent for culture and antibiotic resistance testing.
"As always, it is important to emphasise hygiene and safe-sex messages in advice to cases as well as recommending exclusion from work until symptoms cease," he said.
Last year, it was revealed that Melbourne was facing a rapid increase in cases of the sexually transmitted diseases syphilis and gonorrhoea, including a strain of gonorrhoea that is resistant to antibiotics.