Superbugs are back in the news – and everybody loves a good germ panic story. The bugs raising alarm are called KPC (Klebsiella pneumoniae carbapenemase) or CRE (carbapenem-resistant Enterobacteriaceae).
The Enterobacteriaceae (pronounced enter-oh-bact-ear-ee-ay-cee-ee) are a large family of bacteria, which largely live as a normal part of people’s healthy gut bacteria. It includes E. coli as well as some more nasty bugs such as Salmonella and Shigella, which cause gastroenteritis.
A member of the family that doesn’t get as much press is Klebsiella. It’s a fairly common cause of infections in hospitals, such as urinary tract infections and pneumonia. Different species also live widely in the environment.
The C refers to a carbapenemase, which is an enzyme the bacteria produces that can break down the class of antibiotics called carbapenems. Carbapenems are the hospital’s “big guns”, used for patients who are critically ill, or where there is resistance to other antibiotics.
The problem is that carbapenems share a common structure with penicillins and cephalosporins. Together, this family of antibiotics account for the majority of antibiotic use in hospital.
These bugs sometimes carry extra resistance genes which stop other commonly used antibiotics from working. This often leaves antibiotics which we no longer commonly use (often because they have significant side-effects) as the only treatment option. There have been reports of bacteria resistant to all available antibiotics, and trials on the best way to treat these bugs are underway.
The first isolates of these bacteria seem to have been imported from travellers from overseas or Australians returning home. But these bugs may spread between people relatively easily, especially in health-care facilities. Reports suggest this has occurred in Victoria.
Although these infections may be easily transmitted, becoming sick from them is rare. As the bugs that carry the resistance are similar to normal gut bacteria, they can live there quite happily without causing you any bother. We call this being “colonised” by the bacterium. When they get into places they shouldn’t be (such as your lungs or into your blood) the bacteria can then cause infection. This is more likely in patients who are very unwell, such as people in intensive care units.
Most people who have tested positive for CRE are carrying the bacterium, but are not sick from it. Media reports are therefore carefully phrased with lines such as “have died with a … superbug in their systems”, which means the patient was colonised rather than infected.
When actual infection does occur, the outcomes are often poor. Intensive care units in Europe have reported death rates up to 50%. This is generally because patients who acquire CRE are very sick before their infection, but outcomes are certainly worse for very resistant infections than for more sensitive ones.
Resistance also increases the cost of care and hospital length of stay, impacting everybody in the health-care system.
New antibiotics are desperately needed to treat these infections. The United States government has announced the 10×20 initiative – ten new antibiotics by 2020. Australian researchers are also active in this area. But antibiotic development is a slow process, so in the meantime, a holding strategy is needed.
There are two ways to hold the bugs back – prevent people from acquiring them in the first place, and slow the development of antibiotic resistance.
Infection control is a critical, but often under-appreciated part of our hospitals. And the most important part of infection control is hand hygiene. The hands of health-care workers are critical to the transmission of bacteria between patients. Patients with resistant organisms are often kept isolated, but at least some of the benefit of this isolation comes from prompting health-care workers to clean their hands before and after patient care.
Australia has national guidelines for infection control generally, and specific guidelines for CRE.
The second key intervention is antimicrobial stewardship. Exposing bacteria to antibiotics is the way resistance comes about, and by reducing the use of antibiotics, we can delay resistance. Reducing the use of carbapenem is an important target of stewardship programs, which are now a mandatory requirement for hospitals to be accredited.
The last two years have been a time of rapid development in the fight against antimicrobial resistance. The World Health Organisation has increased its focus on resistance, and the Australian government has released its own national strategy.
Outbreaks such as this highlight the need for government, academia and industry to work together to help take these plans beyond the summits and discussion papers and into our hospitals. Understanding by and involvement of the public is also crucial.
Only with a united front can we hope to slow the “red tide” of resistance.
Trent has no financial disclosures relevant to this article, but has participated as an investigator in (industry-funded) clinical trials on new antimicrobial agents. He is a member of the Australian Society for Infectious Diseases, the Australian College of Infection Prevention and Control, and the Public Health Association of Australia. These views are his own, and not those of his employer or professional associations.