Antimicrobial resistance data reveals mixed findings

By Joseph James Whitworth contact

- Last updated on GMT

EFSA and ECDC antimicrobial resistance infographic
EFSA and ECDC antimicrobial resistance infographic

Related tags: Antimicrobial resistance, Antibiotic resistance

Antibiotic-resistant strains of Listeria monocytogenes in unprocessed salads are not as widespread as originally suspected, according to a study.

Seventy-one strains of L. monocytogenes isolated from raw salad vegetables in the minimally processed state in Malaysia were characterised by serotyping, random amplified polymorphic DNA-polymerase chain reaction analysis (RAPD-PCR) and antimicrobial susceptibility testing.

The isolates were evaluated against 16 antibiotics. Excluding nalidixic acid and oxacillin for which L. monocytogenes has natural resistance, the highest prevalence of resistance was against cephalexin.

None of the isolates were resistant against imipenem and kanamycin.

The multiple antibiotic resistance index (MARI) ranged from 0.06 to 0.63. Most (82%) isolates were susceptible to at least one of the 16 antibiotics commonly used in veterinary and human listeriosis treatment.

“The antimicrobial susceptibility testing indicates that the overall incidence of resistance in L. monocytogenes isolated from vegetables is still relatively low​,” according to the study in the International Journal of Food Safety, Nutrition and Public Health​.

“However it concurs with earlier findings that there are strains of the microbe, albeit in low numbers, that are resistant to a number of antibiotics.”

EFSA and ECDC report

Meanwhile, antimicrobial resistance (AMR) data in zoonotic and indicator bacteria from 2013 has been analysed by two EU agencies.

Multi-resistance and co-resistance to critically important antimicrobials in human and animal isolates were uncommon, said the European Food Safety Authority (EFSA) and the European Centre for Disease Control and Prevention (ECDC​).  

Treatment options for some of the most common foodborne infections are decreasing, as types of bacteria (or isolates) continue to show resistance to antimicrobial drugs, they added.

Microbiological’ resistance was assessed using epidemiological cut-off (ECOFF) values in animal and food isolates and if possible, human isolates.

Information on resistance was reported for Salmonella and Campylobacter isolates from humans, food and animals and data on indicator E. coli and indicator enterococci isolates were related just to animals and food.

The quantitative data on antimicrobial resistance in isolates from humans, food and animals were assessed using epidemiological cut-off values that detect ‘microbiological’ resistance, i.e. reduced susceptibility to the antimicrobials and as well as using clinical breakpoints where appropriate.

In Salmonella from humans, high proportions of isolates were resistant to ampicillin, sulfonamides and tetracyclines, while those resistant to third-generation cephalosporins and clinically non-susceptible to fluoroquinolones generally remained low.

In Campylobacter from humans, a high to very high proportion were resistant to ciprofloxacin and tetracyclines, while resistance to erythromycin was low to moderate.

The resistance to fluoroquinolones in some member states was extremely high; which means effective treatment option for human enteric Campylobacter infection may be significantly reduced.

“The monitoring of antimicrobial resistance in zoonotic and commensal bacteria in food-producing animals and food thereof is a prerequisite for understanding the development and diffusion of resistance, providing relevant risk assessment data, and evaluating targeted interventions,” ​said the report. 

Related topics: Food Safety & Quality

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