European health worries: High levels of drug resistance in zoonotic bacteria

High levels of resistance were also reported in Campylobacter isolates from humans. Among isolates of C jejuni, the most common species identified in 2016, 54.6 percent were resistant to ciprofloxacin, with several countries (Portugal, Spain, Italy, Cyprus, Estonia, and Lithuania) reporting ciprofloxacin resistance levels of between 84 percent and 95 percent. Levels of resistance to tetracyclines in C jejuni were also high (42.8 percent). Among Campylobacter coli isolates, 63.8 percent were resistant to ciprofloxacin and 64.8 percent were resistant to tetracyclines. Resistance to erythromycin was higher in C coli isolates (11 percent) than in C jejuni isolates (2.1 percent).

While combined clinical and microbiological resistance to both ciprofloxacin and erythromycin—which are critically important for treatment of Campylobacteriosis—was low overall (0.6 percent in C jejuni and 8 percent in C coli), resistance to this combination was found in more than a third of all tested human Campylobacter isolates in three member states.

Campylobacter and Salmonella are the two most common foodborne zoonotic bacteria in Europe, with Campylobacter being the most-reported cause of food poisoning. Most infections occur through eating food contaminated with the bacteria, and abdominal pain and diarrhea are the main symptoms. But infections with drug-resistant Salmonella and Campylobacter can cause more severe illness.

“We are concerned to see that Salmonella and Campylobacter bacteria in humans show high levels of antimicrobial resistance,” Mike Catchpole, PhD, the ECDC’s chief scientist, said in an ECDC press release. “The fact that we keep detecting multidrug-resistant bacteria means that the situation in not improving. We need to investigate the origins and prevent the spread of highly resistant strains, such as ESBL-producing Salmonella Kentucky.”

High levels of resistance found in poultry
Among the Salmonella isolates from poultry meat (broilers and turkeys), resistance to tetracycline, ampicillin, and sulfamethoxazole ranged from moderate to extremely high, with the highest levels of resistance to these drugs found among S Infantis isolates from broiler meat. Multidrug resistance was reported in 50.3 percent of Salmonella isolates from broilers and 23.7 percent from turkey meat. In Salmonella isolates from poultry populations, most member states reported moderate to high or extremely high resistance to tetracyclines and sulfonamides, and similar or slightly lower levels of ampicillin resistance.

Observed levels of resistance among C jejuni and C coli isolates from broilers, turkeys, and their meat to ciprofloxacin, nalidixic acid, and tetracylines were generally high (ranging from 50 percent to nearly 90 percent), but the prevalence of multidrug-resistance was low (around 1 percent).

Analysis of commensal E coli isolates from broilers, turkeys, and their meat found high levels of resistance to ampicillin, tetracyclines, ciprofloxacin, and sulfamethoxazole. The level of multidrug-resistance was also high (50.2 percent in broilers and 48.7 percent in turkeys), with considerable variation between the reporting member states.

Specific monitoring of commensal E coli isolates in poultry and poultry meat for production of ESBL, AmpC beta-lactamase, and carbapenemase enzymes, conducted for the first time in 2016, showed that the prevalence of ESBL-producing E coli isolates was low overall also varied widely among member states. Of note was the detection of 14 carbapenemase-producing E coli isolates from Romania and Cyprus.

Zoonotic bacteria carrying ESBL and carbapenemase enzymes are considered a public health concern because they are resistant to a wide spectrum of antibiotics, including penicillin derivatives, cephalosporins, and carbapenems—a class of last-resort antibiotics. Monitoring commensal E coli bacteria for these resistance mechanisms is important for both human and animal health because they can potentially be transferred to other types of bacteria that can spread among people and animal herds.

Also of note, two linezolid-resistant livestock-associated MRSA isolates were identified from the pig production sector in Belgium. The isolates were found to harbor a transferable linezolid resistance gene. Since linezolid is one of the last remaining treatments for highly resistant strains of MRSA, this finding could have important implications for workers on pig farms, who are the most at-risk for LA-MRSA infections.

“The detection of resistance to carbapenems in poultry and to linezolid in methicillin-resistant Staphylococcus aureus in pigs is alarming because these antibiotics are used in humans to treat serious infections,” said Marta Hugas, PhD, EFSA chief scientist. “It is important that risk-managers follow-up on these findings.”

— Read more in European Food Safety Authority and European Centre for Disease Prevention and Control, “The European Union summary report on antimicrobial resistance in zoonotic and indicator bacteria from humans, animals and food in 2016,” EFSA Journal 16, no. 2 (2018)