What's New ? - 2019

What's New ? - 2019

Monitoring antimicrobial resistance trends, the Netherlands, 1998 to 2016

Eurosurveillance: Volume 24, Issue 25, 20/Jun/2019 22 June, 2019

A recent study aimed to optimise interpretation of Antimicrobial resistance (AMR) monitoring data by modelling resistance trends in commensal E. coli from livestock and to evaluate if any trends (and trend changes) were observed from 1998 to 2016.In 1998, a monitoring programme of AMR in livestock started in the Netherlands (NL). The programme was initiated following recommendations given at the Invitational European Union (EU) Conference ‘The Microbial Threat’ hosted by the Danish Government in Copenhagen in 1998. The recommendations were ‘to monitor evolution and effects of interventions, through establishment of accurate surveillance systems on antimicrobial resistance in the human and veterinary sector’. Escherichia coli was chosen as the indicator organism for gut microbiota in order to monitor the effects of antimicrobials with Gram-negative spectra. Between 1998 and 2009, there were statistically significant increasing resistance trends for all antimicrobials, except for tetracyclines and sulfamethoxazole.
Between 2009 and 2016, significant decreasing resistance trends were observed for all antimicrobials in broilers. Additional analyses with the same modelling approach but using 2010 as reference year instead of 2009 showed that for most antimicrobials the decreasing trend started after 2010.
An increasing veterinary therapeutic antimicrobial use (AMU) was measured in NL between 1998 and 2009, corresponding to the AMR trends we found in the broiler data over this time period. For most antimicrobials resistant proportions started to decrease from 2010, confirmed in an additional analysis by the better fit of broiler data in models with 2010 as reference year. In 2010, the illegal prophylactic use of ceftiofur on day-old chicks in hatcheries ended following intensified control measures implemented by the Dutch Food Safety Authority. This may have resulted in the abrupt and significant decreases of cefotaxime- and ceftazidime resistant counts after 2010. Interestingly, however, the observed resistant proportions for ciprofloxacin in broilers remained high and although these proportions decreased significantly since 2009, it is at a slower rate than expected.
Fluoroquinolone-use has decreased considerably in broilers since 2009. As part of the intervention measures, fluoroquinolone-use in livestock was legally restricted as was the use of third generation cephalosporins. Since January 2014, these antimicrobials are only allowed to be used after veterinarians have confirmed by antibiogram that no alternative antibiotics are available (with exception of ceftiofur, which was never licensed in poultry). The relative persistence of ciprofloxacin-resistant E. coli in broilers may be explained by chromosomal mutations, which have a low bacterial fitness cost; ciprofloxacin-resistance is mostly not encoded on plasmids like cefotaxime-resistance is. It is speculated that ciprofloxacin-resistance may be transmitted between broiler flocks, or be introduced from parent stocks, from the farm environment or from hatcheries but it is currently unclear so further investigations are needed. Persistence of quinolone-resistance in livestock is very relevant since fluoroquinolones are marked as critically important antimicrobials by WHO.

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