Frequently asked questions about ESBL

1. What is ESBL?

ESBL, or Extended Spectrum Beta Lactamase, is an enzyme produced by certain bacteria found in the intestinal system and mucous membranes (particularly Escherichia coli and Klebsiella). The acronym ESBL is often also used to refer to these bacteria. Other ESBL-type enzymes exist as well, one of the more common ones is AmpC. These enzymes do an effective job of cutting up some of the most commonly used antibiotics, in other words antimicrobial drugs, such as third-generation cephalosporins and usually also penicillins and first- and second-generation cepholosporins.  The bacteria producing ESBL enzymes are often resistant to many other common antimicrobial drugs as well.

2. What do ESBL bacteria cause?

E. coli and Klebsiella are part of the normal bacterial growth in humans and animals, but they can cause infections in both, including urinary infections and mastitis. E. coli bacteria or other enteric bacteria found in intestinal systems or the environment may begin to produce ESBL enzymes if this property is transmitted to them from some other bacteria, or they contract this property through mutation due to heavy use of antiobiotics, for instance. The ability to produce the ESBL enzyme does not itself increase a bacterium's pathogenic capability, but it can significantly hamper the treatment of infections caused by these bacteria by means of antimicrobial drugs.

3. ESBL occurring in animals in Finland

Bacteria producing the ESBL enzymes are found increasingly often in companion animals and pets. The majority of these bacteria cause diseases in animals, but they are also found in monitoring or surveillance samples taken from healthy animals.

 In Finnish production animals, the bacteria producing ESBL/pAmpC enzymes have been found most often in the broiler production chain.  Bacteria producing resistant enzymes have sporadically also been found among slaughtered cattle and pigs. 

4. How does ESBL spread?

ESBL strains can be transmitted between humans and animals. At the moment, very little information exists on the ESBL sources of production animals or on the spread of ESBLs. However, it would seem apparent that the ESBL/AmpC bacteria have found their way into the Finnish broiler production chain in the intestinal systems and on the mucous membranes of imported newly hatched birds from the grandparent generation. The use of certain broad-spectrum antiobiotics - third- and fourth-generation cephalosporins - in the treatment of animals is considered a major risk factor in the generation of ESBL strains. In Finland, the use of third- and fourth-generation cephalosporins is restricted by means of legislation.

5. Are foods safe with respect to ESBL?

Bacteria producing ESBL enzymes can be found in food. The E. coli bacterium, for instance, is part of the normal bacterial flora of the intestinal systems of animals, and it is commonly found in the environment. Meat may become contaminated with bacteria producing ESBL enzymes during slaughter, while vegetables may become contaminated via irrigation water, for instance. The contamination of food by various harmful or pathogenic bacteria (including bacteria producing ESBL enzymes) can be prevented by maintaining good production hygiene.

In Sweden, a comparative study that included ESBL producing E. coli bacteria isolated from humans, production animals, food, the environment and waste water was conducted. According to this study, the ESBL types found in food and production animals are different from the ones found in humans, waste water and the environment. This Swedish study suggests that food and production animals are not significant sources of ESBL infections in humans (Report  2014, www.livsmedelsverket.en). German and Danish studies produced the same result: meat does not seem to be a major source of ESBL infections in humans (Int J Med Microbiol. 304 (5–6): 678–84; Infect Ecol and Epidemiol 4: 22924). However, a Dutch study found suggestions of ESBL being transmitted from poultry to humans (Clin. Microbiol. Infect. 2011; 17: 873–880). The significance of animals and food to ESBL infections in humans has not thus far been investigated in Finland.

ESBL producing bacteria are commonly found in meat. The 2014 EU monitoring project focused on pork and veal, and on average, about 40 % of the samples tested positive for ESBL producing bacteria (EFSA Journal 2017; 15(2): 4694, 212 pp.). The survey results for iler meat in the EU states in 2016 will be published later, but the occurrence of ESBL in broiler meat has been analysed in some countries also previously. In Denmark and the Netherlands, ESBL producing bacteria or similar E. coli bacteria have been found commonly in broiler meat: in Denmark, for example, 25 % of domestic and 64% of imported chicken meat was found to contain ESBL/AmpC producing bacteria in 2015 (DANMAP 2015).  In the Netherlands in 2014, ESBL/AmpC producing bacteria were found in 67 % of fresh meat  and in 87 % of imported meat (MARAN 2015).

6. ESBL in meat in Finland

The foods analysed in Finland for bacteria producing ESBL/AmpC enzymes include domestic broiler chicken meat as well as beef and pork marketed in retail stores. These bacteria were for the first time found in domestic broiler chicken meat in 2010. Initially the prevalence of bacteria producing the ESBL enzyme appeared to increase in domestic broiler chicken meat, but in 2013 prevalence was already found to be clearly lower. In 2012, 18% of the analysed broiler chicken meat tested positive for E. coli bacteria that produces the ESBL/pAmpC enzymes, whereas in 2013 it was only found in 13% of the samples. Evira analysed in 2016 a total of 309 samples of chicken meat: 22% tested positive for ESBL/AmpC producing bacteria. The analysed samples were all domesticbroiler meat.

Evira to analyse 300 broiler chicken samples for ESBL in 2016.  An EU-wide ESBL surveillance programme that also covers beef and pork marketed in retail stores was started in 2014. Evira studied in 2015 the prevalence of ESBL bacteria in raw pork and beef as part of surveillance executed in all EU states. Of the 303 pork samples analysed, only one was tested positive for E. coli bacteria that produces an ESBL-like enzyme. All of the 300 beef samples that were analysed were free from ESBL or ESBL-like bacteria. The number of products of foreign origin was 14 for beef and 11 for pork.

7. Can Finnish eggs contain ESBL producing bacteria?

Finnish eggs have so far not been positive for ESBL producing bacteria (Were Nyando: ESBL- ja AmpC-entsyymiä tuottavan Escherichia coli -bakteerin esiintyvyys kananmunissa, opinnäytetyö Metropolia Ammattikorkeakoulu, 2016).  It is usually not possible for bacteria to gain access inside the egg. There are bacteria on the egg shell, on the other hand, but they are in most cases harmless. You should always wash your hands after handling eggs.

8. Can I have an influence?

Bacteria producing ESBL enzymes are spread through touch, in other words via hands. Good work and hand hygiene can be used to prevent ESBL infections - and other infections - related to cooking. Bacteria producing ESBL enzymes can be destroyed in food by means of heating properly. Cooked meat and other products do not contain ESBL bacteria, provided that the contamination of these foods has been prevented after cooking.