What is ESBL?
ESBL (Extended Spectrum Beta Lactamase) is a type of enzyme produced by certain bacteria found in the bowel and on mucous membranes (particularly Escherichia coli and Klebsiella), that can break down antibiotics. The term ESBL is also often used to refer to the bacteria themselves. ESBLs and other similar kind of enzymes such as AmpC make bacteria resistant to most commonly used antibiotics. ESBL-producing bacteria may also be resistant to many other important antibiotics.
What do ESBL bacteria cause?
E. coli and Klebsiella are a normal part of the gut microbiome of humans and animals, but they can also cause infections e.g. mastitis and urinary tract infections. E. coli or other bacteria found in the bowel or in the environment may start to produce ESBL enzymes if this ability is transmitted to them from other bacteria, or they acquire this ability through mutation due to heavy use of antibiotics, for instance. The ability to produce ESBLs does not in itself increase the pathogenic capability of a bacterium, but it can significantly hamper the treatment of infections caused by these bacteria with antibiotics.
ESBL occurring in animals in Finland
Bacteria producing ESBLs are found increasingly in companion animals and pets in the 2010s. These bacteria are found in a variety of infections from animals as well as in monitoring or surveillance samples taken from healthy animals.
In Finnish food-producing animals, the bacteria producing ESBLs/AmpC enzymes have most often been found in the broiler production chain. Bacteria producing these resistance enzymes have sporadically also been found in slaughtered cattle and pigs.
How does ESBL spread?
ESBL strains can be transmitted between humans and animals. Currently, very little information exists on the ESBL sources or of the spread of ESBLs in food-producing animals. However, it would seem apparent that the ESBL/AmpC bacteria have found their way into the Finnish broiler production chain in the intestinal tract and on the mucous membranes of imported chicks of previous generations. The use of certain broad-spectrum antibiotics, third and fourth generation cephalosporins in particular, in the treatment of animals is considered a major risk factor in the formation of ESBL strains. In Finland, the use of third- and fourth-generation cephalosporins is restricted by law.
Are foods safe with respect to ESBL?
ESBL-producing bacteria can be found in foodstuffs. The E. coli bacterium, for instance, is a normal part of the gut microbiome of animals, and it is commonly found in the environment. Meat may become contaminated with ESBLs during slaughter, while vegetables may become contaminated via irrigation water or soil. The contamination of foodstuff by various harmful or pathogenic bacteria (including ESBL-producing bacteria) can be prevented by maintaining good production hygiene practices.
In Sweden, a comparative study on ESBL producing E. coli bacteria isolated from humans, production animals, food, the environment and waste water was conducted. The results of the study suggest that foodstuffs or production animals are not a significant source of human ESBL infections (Swedish Food Agency, report 2014). German and Danish studies report similar results: meat does not appear to be a significant source of ESBL infection in humans (source: Int J Med Microbiol. 304 (5–6): 678–684; Infect Ecol and Epidemiol 4: 22924). However, a Dutch study has found some evidence of ESBL-producing bacteria transmitting from poultry to humans (source: Clin. Microbiol. Infect. 2011; 17: 873–880). Thus far, the significance of animals and foodstuff to human ESBL infections has not comprehensively been investigated in Finland.
ESBL in meat in Finland
In Finland the foods analysed for ESBL/AmpC producing bacteria include domestic broiler chicken meat as well as retail pork and beef. Such bacteria were found in broiler chicken meat for the first time in 2010, whereafter they have appeared moderately in retail meat. Since 2016 fresh retail broiler meat has been studied throughout the EU.
Fresh retail pork and beef have been inspected for ESBL/AmpC producing bacteria since 2015 as a part of an EU-wide monitoring programme. Such bacteria have very rarely been found in pork and never in beef sold in Finland. The majority of the pork and beef samples have been of domestic origin. More information on the prevalence of the bacteria can be found on the Zoonosis Centre website.
Can raw pet food contain ESBL-producing bacteria?
ESBL and AmpC-producing bacteria have been found in raw pet food both in Finland and abroad. Raw pet food consists of raw meat as well as animal by-products, such as organ meats and cartilage, from animals approved for human food. Due to the nature of raw pet food products, the food is not heated in order to destroy possible pathogens.
Can Finnish eggs contain ESBL producing bacteria?
Finnish eggs have so far not been positive for ESBL producing bacteria (source: Were Nyandoto: Investigation of ESBL and AmpC producing Escherichia coli in chicken eggs, thesis, Metropolia University of Applied Sciences, 2016). Normally, bacteria cannot penetrate the egg-shell. Nonetheless, bacteria can be found on top of the egg-shell, but they are usually harmless. You should always wash your hands after handling eggs.
What can I do?
Bacteria producing ESBL enzymes are spread through touch, in other words via hands. Good work and hand hygiene while preparing food can prevent the spread of ESBL and other infections. Bacteria producing ESBLs can be destroyed by heating food properly. Cooked meat and other products do not contain ESBL bacteria, provided that the contamination of these foods has been prevented after cooking.