A report today from the European Centre for Disease Prevention and Control (ECDC) and the European Food Safety Authority (EFSA) shows high levels of antimicrobial resistance in bacteria from humans, animals, and food across Europe, highlighted by "extremely high" multidrug resistance in a type of Salmonella that causes illness in humans.
The summary report is based on data on antimicrobial resistance in zoonotic and indicator bacteria submitted by 28 European Union (EU) member states in 2015 and jointly analyzed by scientists from the ECDC and the EFSA. It provides an overview of resistance in Salmonella isolates from humans, food-producing animals (pigs and calves), and their meat; Campylobacter isolates from humans and pigs; and Escherichia coli isolates from pigs, calves, and their meat. Data on the incidence of methicillin-resistant Staphylococcus aureus (MRSA) in pigs, calves, and their meat are also included.
Salmonella, Campylobacter, and E coli are all examples of zoonotic bacteria, which can be transferred from animals to humans via contaminated food or through the environment. The authors of the report say that monitoring these bacteria for antimicrobial resistance in humans, food animals, and food can help scientists understand how resistance develops and disseminates and how they can evaluate targeted interventions.
High resistance in human Salmonella isolates
The most concerning finding of the report regards Salmonella isolates from human cases, the second most commonly reported foodborne infection in the EU. Overall, multidrug resistance (MDR) was found in 29.3% of the human Salmonella isolates submitted by EU member states, with high proportions of isolates resistant to sulfonamides (32.1%), tetracyclines (28.1%), and ampicillin (27.8%). One of the most common Salmonella serovars in humans, monophasic Salmonella Typhimurium, exhibited extremely high MDR (81%), with 14 isolates exhibiting resistance to at least 7 antimicrobials.
The proportion of human Salmonella isolates that were resistant to the clinically important antimicrobials ciprofloxacin and cefotaxime, which are recommended for the treatment of severe enteric disease or invasive infection, were relatively low (13.3% and 0.9%, respectively). But the report notes that ciprofloxacin resistance rose from 8.8% in 2014, a 34% increase.
The report also found high levels of resistance in Campylobacter isolates from human cases, the most commonly reported foodborne disease in the EU. Very high to extremely high resistance to ciprofloxacin was reported in Campylobacter isolates from nearly all EU member states, with 11 countries reporting ciprofloxacin-resistance levels of 80% to 100% in Campylobacter coli, while 5 member states reported increasing trends of fluoroquinolone resistance in Campylobacter jejuni.
"The level of acquired resistance to fluoroquinolones is so high in some member states that this agent can no longer be considered appropriate for routine empirical treatment of human campylobacter infection," the authors write.
In addition, more than 10% of C coli isolates were found to be co-resistant to ciprofloxacin and erythromycin, the antibiotics considered critically important to treatment of Campylobacter infections
Resistance in animals, meat
Among the Salmonella isolates from pig meat, the highest levels of resistance were reported for ampicillin (44.7%), sulfamethoxazole (48.5%), and tetracyclines (49.1%). In isolates from bovine meat, resistance to most antimicrobials tested was mainly lower than those observed in pig meat, but resistance to sulfamethoxazole and tetracyclines was higher.
Among Salmonella isolates from fattening pigs, moderate or high to extremely high resistance was reported for tetracyclines and sulfonamides, with slightly lower levels of ampicillin resistance. Slightly lower levels of resistance to these drugs were found in isolates from calves under 1 year of age.
In C coli isolates from fattening pigs, overall resistance was very high for ciprofloxacin (62.1%), nalidixic acid (60.8%), and tetracycline (66.6%), and high for erythromycin (21.6%). In E coli from fattening pigs, high levels of resistance were found to tetracyclines (54.7%), sulfamethoxazole (44.2%), ampicillin (39.3%), and trimethoprim (35.3%), with 38.1% of isolates displaying MDR. Resistance levels in indicator E coli isolates from calves were also high, though generally lower than those found in pigs.
"The high levels of resistance to tetracyclines, sulfamethoxazole, ampicillin and trimethoprim in E. coli from both fattening pigs and calves under one year of age, as well as the frequent occurrence of resistance to these compounds as a core component of MDR patterns in many reporting countries, reflects extensive usage of these antimicrobials in these countries over many years," the authors write.
Member states also reported resistance to carbapenems and colistin, two last-resort antibiotics for the treatment of MDR infections, although the levels were low. Two countries (Belgium and Germany) detected carbapenemase-producing E coli in pigs and pig meat, while low levels of colistin resistance were detected in E coli and Salmonella isolates from pigs and calves.
MRSA was reported in pigs and calves in several member states, but resistance to vancomycin and linezolid was not detected in any isolates.
More needs to be done
European health officials say the findings are a sign that more needs to be done in the fight against antimicrobial-resistant bacteria, which cause an estimated 25,000 deaths in the EU each year.
"Antimicrobial resistance is an alarming threat putting human and animal health in danger," Vytenis Andriukaitis, EU commissioner for health and food safety, said in an ECDC press release. "We have put substantial efforts to stop its rise, but this is not enough. We must be quicker, stronger and act on several fronts."
Feb 22 EU summary report
Feb 22 ECDC press release