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More ESBL bacteria at farms with high consumption of antibiotics

Friday 13 Jun 14
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Robert Skov
Chief physician at SSI
+45 32 68 83 48
rsk@ssi.dk

There is a connection between previous consumption of cephalosporin antibiotics and the amount of ESBL bacteria in pigs. At the same time, there is an increased occurrence of ESBL-producing bacteria in farm workers at farms where ESBL bacteria have been found in pigs. These findings appear from a new study undertaken by Statens Serum Institut (SSI), one of Denmark’s largest research institutions in the health sector, and the National Food Institute, Technical University of Denmark.

ESBL bacteria are coli and other gut bacteria resistant not only to ordinary penicillins, but also to cephalosporin antibiotics, which are critically important for treatment of severe infections in humans. ESBL bacteria can be found in the gut of both animals and humans without resulting in disease. However, they may also result in e.g. urinary tract infection, and as a consequence of resistance there may be only few treatment options.

In the past ten years an increasing number of infections caused by ESBL bacteria has been seen worldwide. One of the sources of ESBL bacteria may be farm animals such as pigs. Therefore, SSI and the National Food Institute have investigated the connection between consumption of 3rd and 4th generation cephalosporins and the occurrence of ESBL bacteria in pigs and humans living or working at pig farms.

Connection between consumption and ESBL
"We found significantly more ESBL bacteria in pigs at farms with high consumption of cephalosporins than in herds which had no consumption of these antibiotics. So there is a connection”, says Yvonne Agersø, senior researcher at the National Food Institute"

Faecal samples were taken from pigs and humans at 20 farms where cephalosporins were not used in the herds, and at 19 farms previously having a high consumption of cephalosporins. 

“We found significantly more ESBL bacteria in pigs at farms with high consumption of cephalosporins than in herds which had no consumption of these antibiotics. So there is a connection”, says Yvonne Agersø, senior researcher at the National Food Institute.

In July 2010, pig producers introduced a voluntary stop for the use of 3rd and 4th cephalosporins. This study was done in the months following the stop. At 79 % of the farms where, earlier, cephalosporins consumption was high ESBL bacteria were found in faecal samples from pigs, whereas this was only the case at 20 % of the farms where cephalosporins had not been used.

Same bacteria in pigs and humans

There are many different sources of ESBL bacteria. To investigate whether there were signs of spread between pigs and humans, 195 persons working or living at the 39 farms were examined as well. In 19 persons from 13 farms, ESBL bacteria were found in faecal samples. All persons, but one, had been in contact with pigs, and most of the persons with ESBL bacteria worked at farms where ESBL bacteria had been found in pigs as well.

Bacteria from both pigs and humans were studied further, and at four farms exactly the same bacterial clone was found in pigs and in persons working at the farm.

“This indicates that ESBL bacteria can spread between pigs and farmers. Farmers who had ESBL bacteria in their gut were not ill. However, the ESBL bacteria were resistant to several types of antibiotics, which would make treatment difficult, should they later cause an infection”, says Robert Skov, chief physician at SSI.

ESBL bacteria may cause urinary tract infections in humans. In rare cases, they may also lead to much more serious infections, e.g. bacteremia.

SSI monitors the number of bacteremia with ESBL-producing bacteria. In the first four months of 2014, SSI received 70 notifications of bacteremia with ESBL bacteria.

Read more

The findings of this study were recently published in Journal of Antimicrobial Chemotherapy: Characterization of extended-spectrum b-lactamase (ESBL)-producing Escherichia coli obtained from Danish pigs, pig farmers and their families from farms with high or no consumption of third- or fourth-generation cephalosporins.

Check out this link on ESBL on SSI’s homepage 

Facts about ESBL bacteria

ESBL stands for extended-spectrum beta-lactamase (ESBL)-producing bacteria.

Bacteria can protect themselves against antibiotics by developing resistance, e.g. by creating enzymes which break down penicillin or other antibiotics. ESBLs are enzymes which can break down ordinary penicillins, which are used for treating many different infections in humans, and cephalosporins, which are used for treating particulary severe infections in humans. Several hundred different variants of ESBL exist.

Those genes which make the bacteria resistant can be transferred between bacteria. You could say, bacteria can contaminate each other with antibiotics resistance.

In the past ten years, a big rise in the occurrence of ESBL-producing bacteria has taken place. This rise is observed in animals and humans, inDenmark and worldwide.

In some cases, the same types of resistant ESBL bacteria can be found in animals, meats as well as humans. This suggests contamination spread from animals to humans either direct or via meat.

A large part of infections with ESBL bacteria in humans is due to contamination spread from patient to patient and bears no connection with ESBL bacteria in animals.