Author: Maria Burke
A life-threatening drug-resistant bacteria is rarely transmitted to humans through animal or environmental contact as had been feared. An international group of researchers has discovered. Infections appear to be spread from person to person, meaning the best way to control spread is strict hygiene control.
Klebsiella is a genus of bacteria which lives in the intestines but can be dangerous in other parts of the body. The most well-known species is Klebsiella pneumoniae, which can cause pneumonia, meningitis, urinary tract infections and infections in the bloodstream.
‘These bacteria are a bigger problem in the UK than MRSA,’ says team leader Ed Feil from the University of Bath. ‘Klebsiella infections are becoming increasingly resistant to antibiotics, so whereas you used to be able to treat most urinary tract infections easily, now it is more common that patients are getting infections that keep coming back and causing problems. Klebsiella can also cause pneumonia, which kills around half of patients.’ Some strains are resistant to carbapenems, one of the ‘last resort’ class of antibiotics.
In the largest study ever conducted, the team looked for Klebsiella in different environments such as farms and wastewater, to monitor how it spreads with the aim of working out the best way to prevent and control outbreaks (Nature Microbiol., 2022, 7, 2054). They collected 6548 samples over a 15-month period from different locations in and around the Italian city of Pavia where Klebsiella is a major problem in hospitals. They swabbed patients in hospitals and healthy ‘carriers’ in the community, as well as taking samples from livestock, pets, puddles, house flies and other insects.
The samples were analysed using whole genome sequencing techniques to detect and identify any Klebsiella bacteria present. They found 3482 isolates, including 15 different species, with half of the positive samples containing K. pneumoniae. There was little overlap between those strains found in the hospitals and those found in the environment.
‘This is the biggest, most systematic study that has been conducted in a single geographical location,’ says Keil. ‘We found Klebsiella was present everywhere but were surprised that the strains found in hospital were different to those found in the environment, indicating there’s very little transfer between the two habitats: humans nearly always catch this from other humans.’
The fear was that farmers might catch these bacteria from their livestock or soil, or that people could get infected by eating contaminated salad or swimming in lakes. But the team did not find any evidence to support this. However, they did find resistant Klebsiella in pets, such as cats and dogs, implying these animals could pose a risk for spreading the bacteria.
‘This confirms the best way to control infection for these bacteria remains stringent hospital hygiene, and that there is less chance that outbreaks may be caused by contact with animals or the environment than previously feared, at least in a high-resource country like Italy,’ Keil concludes.
Klebsiella is one of the most important opportunistic pathogens globally, says Willem van Schaik of the University of Birmingham, UK. ‘Multidrug-resistant Klebsiella infections are on the rise globally and it is of consider-able importance to learn what factors drive the emergence and spread of these strains.’
Jose Bengoechea of Queen’s University Belfast, UK, agrees. ‘Klebsiella is one of the microbes sweeping the world in the pandemic of antibiotic-resistant infections. More than two thirds of the strains are resistant to three common antibiotics. Carbapenem-resistant K. pneumoniae, and third-generation cephalosporin-resistant K. pneumoniae account for at least 100,000 annual deaths. K. pneumoniae is one of the five pathogens responsible for 31% all infection-related deaths, and one of the leading causes of death in sub-Saharan Africa and Asia.’
This work settles a long-standing question about the transmission of Klebsiella, he says. ‘This is an important finding and highlights how we are polluting the environment with these microbes. Importantly, we do not know yet the consequences to the environment. On the other hand, I support the importance of strict hygiene solution to control the dissemination of microbes such as Klebsiella to the environment.’
This paper makes a convincing case that, at least for Klebsiella, spread from animals and food to humans is rare, with human-to-human transmission being the main driver, van Schaik believes. ‘For this reason, infection prevention [by stricter cleaning protocols and hand hygiene guidelines], may be key to minimise the spread of Klebsiella in human populations.’
Meanwhile, a new WHO report reveals high levels of resistance in bacteria causing life-threatening bloodstream infections, as well as increasing resistance to treatment in several bacteria that cause common infections (who.int/publications/i/item/9789240062702). It shows more than half of bacteria such as Klebsiella pneumoniae and Acinetobacter spp frequently causing hospital infections showed resistance. Around 8% of bloodstream infections caused by K. pneumoniae were reported as resistant to carbapenems.