Antimicrobial resistance of bacteria isolated from animals
Antibiotic, or antimicrobial, refers to a substance that kills other micro-organisms, or inhibits their growth. Antimicrobials’ spectrum of activity varies, as some are broad spectrum, i.e. they act against a broad spectrum of bacteria, while others only act against specific types of bacteria (narrow spectrum antimicrobials).
Bacteria have both natural and acquired resistance mechanisms. The natural resistance of bacteria is a characteristic of bacterial families or species, meaning that not all groups of antimicrobials are effective against all bacteria. Acquired resistance, in turn, refers to strains formerly sensitive to a certain medicinal substance transforming and becoming resistant, for example as a result of genetic mutation or horizontal gene transfer. Multi-resistant bacteria are simultaneously resistant to several groups of antimicrobials.
Antimicrobial resistance, which has become more common in recent years, increases the morbidity and mortality of humans and animals, and health care costs. The increased prevalence of antimicrobial resistance is one of the most serious threats to human and veterinary health care. The aim is therefore to prevent the formation and spread of bacterial strains resistant to antimicrobials. The Government Decree prohibiting the veterinary use of certain medicinal products (1054/2014) restricts or prohibits the veterinary use of antimicrobials used in the treatment of serious infections in humans. The Finnish Decree applies to all animal species and is one of the strictest regulations within this area in the EU.
FINRES-Vet, the Finnish Veterinary Antimicrobial Resistance Monitoring and Consumption of Antimicrobial Agents programme, has been running since 2002. The programme involves studying the antimicrobial susceptibility of zoonotic pathogens, which are bacteria transmissible from animals to humans, and that of certain bacteria pathogenic to animals, and indicator bacteria. The indicator bacteria included in the monitoring of resistance constitute a major component in the intestinal microbiota of healthy animals. Their resistance is thought to reflect the spectrum of antimicrobial treatments used in the animal populations in question.
In addition to the resistance situation, the programme monitors the use of feed additives and the sales of veterinary antimicrobials. In addition to the Finnish Food Safety Authority Evira, the Finnish Medicines Agency Fimea and, since 2012, the University of Helsinki Laboratory of Clinical Microbiology at the Faculty of Veterinary Medicine are participating in the implementation of the FINRES-Vet programme. In 2015, 12,300kg of antimicrobials classified as active substances were used as veterinary medicines in Finland. Throughout the 2010s, total sales of veterinary medicines have remained at around 13,500kg. Per animal unit, this is one of the lowest rates in the EU (Use of antibiotics). Consumption figures are based on product-specific statistics obtained from pharmaceutical wholesale license holders, and cannot be used as a basis for reliable calculations of the quantities of pharmaceutical substances administered to various animal species. In Finland, injectable penicillin is most commonly used as veterinary medicine.
The Joint Interagency Antimicrobial Consumption and Resistance Analysis (JIACRA) report by three organisations – the European Centre for Disease Prevention and Control (ECDC), European Food Safety Authority (EFSA) and European Medicines Agency (EMA) – analyses the use of antimicrobials and resistance in humans and animals in the EU area. The recent 2017 JIACRA report identifies the link between antimicrobials used in production animals and antimicrobial resistance.
The monitoring of resistance in the EU is currently based on EU legislation (Commission Implementing Decision 2013/652/EU), which defines the types of bacteria, animal species and foods being tested each year. The FINRES-Vet programme is implemented in accordance with the relevant EU legislation and Finland’s national decisions. The results are presented annually in the joint antimicrobial resistance report by the EFSA and ECDC, for the most significant zoonotic bacteria, salmonella and campylobacter, and the indicator bacterium Escherichia coli. In 2014, resistance monitoring focused on the poultry sector, followed by the cattle and pig sectors in 2015.
Of zoonotic bacteria, salmonella is rarely found in food-producing animals and domestic foodstuffs of animal origin in Finland, which is why the number of strains tested for resistance is low. The analysed salmonella strains tend to have been sensitive to various antimicrobials. This good situation is also illustrated by the fact that, in EU reports, data for Finland – together with Sweden – is generally missing from the resistance comparison of various salmonella strains isolated from animals, because the number of salmonella strains isolated is very low in both countries.
Proportion of completely susceptible and multi-resistant Salmonella spp. isolates from broilers in reporting countries in 2014
Source: EFSA and ECDC, 2016. The European Union summary report on antimicrobial resistance in zoonotic and indicator bacteria from humans, animals and food in 2014. EFSA Journal 2016;14(2):4380, page 64. Link to report
In international comparison, little resistance is found in campylobacter in Finland. Although resistance to ciprofloxacin increased in campylobacter isolated from all food-producing animal species in Finland, in 2010-2014, the occurrence of resistance remains below the EU average. For example, in 2014 ciprofloxacin resistance in Campylobacter jejuni isolated from broilers was found in Finland in a quarter of all bacterial strains analysed, while resistance was 70% when all Member States are taken into account. The good situation in Finland is also illustrated by the fact that the proportion of Campylobacter strains sensitive to all antimicrobials tested remains very high. In previous years, strains resistant to ciprofloxacin have been found very sporadically in broilers, and in 2015 resistance to ciprofloxacin was no longer present in campylobacter of broilers.
Proportion of completely susceptible and multi-resistant Campylobacter jejuni isolates from broilers in reporting countries in 2014
Source: EFSA and ECDC, 2016. The European Union summary report on antimicrobial resistance in zoonotic and indicator bacteria from humans, animals and food in 2014. EFSA Journal 2016;14(2):4380, page 123. Link to report
In 2014, in Finland, the level of resistance in E. coli indicator bacteria isolated from broilers was the second lowest in Europe, after Norway. E. coli bacteria are very commonly multiresistant (resistant to at least three different antimicrobial groups) throughout Europe outside the Nordic countries. Multiresistance in E. coli indicator bacteria isolated from broilers was second lowest in Finland, covering 2.9% of bacterial strains, after Norway. Statistics on multiresistance are presented in the PXWeb tables.
Proportion of completely susceptible and multiresistant Escherichia coli isolates from broilers in reporting countries, 2014
Proportion of Escherichia coli isolates completely susceptible to the tested antimicrobials from broilers in reporting countries, 2014 (%)
Source: EFSA and ECDC, 2016. The European Union summary report on antimicrobial resistance in zoonotic and indicator bacteria from humans, animals and food in 2014. EFSA Journal 2016;14(2):4380, page 141. Link to report
Correspondingly, resistance in E. coli indicator bacteria isolated from slaughter pigs is below the EU average in Finland. In many cases, E. coli indicator bacteria isolated from pigs were sensitive to all the antimicrobials studied; the number of fully sensitive strains found in Finland was the second highest in all European countries. In addition, multiresistance was the second lowest in Finland after Norway.
Proportion of completely susceptible and multiresistant Escherichia coli isolates from pigs in reporting countries, 2015
Proportion of Escherichia coli isolates completely susceptible to the tested antimicrobials from pigs in reporting countries, 2015 (%)
Source: EFSA (European Food Safety Authority) and ECDC (European Centre for Disease Prevention and Control), 2017. The European Union summary report on antimicrobial resistance in zoonotic and indicator bacteria from humans, animals and food in 2015. EFSA Journal 2017;15(2):4694, sivu 129. Link to report
Under the EU programme, the occurrence of ESBL bacteria in food-producing animals and meat derived from them is analysed in alternate years for poultry and cattle/pigs. In Finland, ESBL bacteria in pigs, beef and pork have been found in very low quantities, or not at all.
 EU report: more evidence on link between antibiotic use and antibiotic resistance, Link to report
Photo in upper edge: Merja Outavaara/Evira