Colistin is an antimicrobial polypeptide. It is often used to treat neonatal diarrhea and post-weaning diarrhea - caused by enterotoxigenic and Shiga toxin producing Escherichia coli (ETEC and STEC).
However, the spread of colistin-resistant E.coli is alarming. Resistance was first associated with mutations on chromosomes until Liu et al. 2015 identified the plasmid-mediated resistance gene mcr-1. Since then, five different mcr genes have been localised and a global spread of the resistance genes observed and documented by several studies.
The aim of the study "Co-occurrence of mcr-1, mcr-4 and mcr-5 genes in multidrug-resistant ST10 Enterotoxigenic and Shiga toxin-producing Escherichia coli in Spain" from 2006 to 2017 was the characterization of clonal groups of colistin-resistant E. coli in pigs affected by PWD in conventional husbandry.
76.9% of the 186 ETEC and STEC isolated in Spain showed resistance to colistin. Within the resistant groups 102 were identified as mcr-4 carriers, 37 as mcr-1 carriers and 5 as mcr-5 carriers, with mcr-1/mcr-4, mcr-1/mcr-5 and mcr-4/mcr-5 occurring simultaneously in five isolates. Three different mcr-4 variants were also discovered and the clonal group ST10-A (CH11-24) was described as mainly responsible for the spread of the mcr-4 gene.
The study shows the great importance of intensive pig farming as a reservoir for colistin-resistant ETEC and STEC. This can become a serious threat to human health.
Shiga toxin producing Escherichia (E.) coli (STEC) are important foodborne pathogens. They can cause severe diseases such as haemorrhagic Colitis or haemolytic uremic syndrome. A longitudinal cohort study in three finishing sites was conducted to study the epidemiology of STEC in final fattening pigs and examine the risks they may pose for human infections with STEC.
Consistent with our prior studies, Stx2e was the most frequently observed Stx variant in final fattening pigs (93,9%).
The results confirm that pigs raised for pork production are a reservoir for human STEC infections. Circulating serotypes within the cohorts as well as factors for site management have a significant influence on the prevalence of STEC.
Source: International Journal of Food Microbiology
Read the full study on www.sciencedirect.com
Last July, the European Commission adpoted an Implementing Decision regarding the authorisation of all the veterinary drugs containing 'colistin' in combination with other oral antimicrobial drugs.
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The Committee therefore recommended the refusal of the granting of the marketing authorisations and the withdrawal of the existing marketing authorisations for veterinary medicinal products containing zinc oxide.
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German researchers found more than 400 Escherichia coli isolates, which tested positive for the MCR-1 gene. This gene can make bacteria resistant to colistin, a powerful antibiotic. MCR-1 was found in 79,8% of colistin-resistant E.coli isolates. The study screened over 10.000 E.coli isolates, which have been gathered from German food and livestock from 2010 to 2015. The gene was most prevalent in poultry production and food chains. Overall, the scientists claim, that the prevalence of the MCR-1 gene is twice as high in Germany as it is in France. The colistin resistance in Germany is also higher than the average among European countries, which may be caused by higher use of polymixin antibiotics. More studies need to be conducted to better assess the findings.
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First results from resistance monitoring conducted at the Federal Institute for Risk Assessment (BfR) show that colistin resistant bacteria are wide spread among farm animals in Germany. The resistances were most frequently found in Escherichia coli of broilers. “The current results underline that the strategy of a responsible use of antibiotics must be consistently pursued in future", says the President of the BfR, Professor Dr. Dr. Andreas Hensel. Further biomolecular studies will be conducted to assess potential risks to consumers. It is recommended to follow careful kitchen hygiene, so germs are not transferred from meat to other food. Also, meat should be heated thoroughly before eating, so that it reaches a temperature of 70°C for 2 minutes at its core.
Read the full article on www.bfr.bund.de
To match the latest scientific literature regarding antimicrobial use in human and veterinary fields, the Pig Veterinary Society (PVS) has updated their prescribing principles for antimicrobials. These principles divide antimicrobials into 3 classes. Class 1 antimicrobials can be subscribed within responsible use guidelines, class 2 antimicrobials are not to be used unless sensitivity tests or clinical experience has proven that the first choice antimicrobials are not effective. Colistin has now been moved into Class 3, which are products of last resort. Those are only to be used when no other option is available and has to be supported by laboratory sensitivity tests. This step was necessary, because the importance of Colistin as a critically important antimicrobial in human medicine is increasingly evident. PVS advices their members to download the new version of the principles and follow the guidance within the document.
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Danish agricultural fields are increasingly contaminated with zinc. This is due to the high content of zinc in pig manure which is used as fertilizer on said fields.The Danish Ministry of Environment and Food called the presented data “worrying” and that alternatives have to be considered. In pigs zinc and copper are used after weaning, especially for the prophylaxis of diarrhea and edema disease. An alternative for the latter could be the one shot vaccination against Shiga toxin.
Read the full article on www.animal-health-online.de