J Dairy Sci. 2016 Nov 16. pii: S0022-0302(16)30816-5. doi: 10.3168/jds.2016-11839. [Epub ahead of print]
- 1GD Animal Health, PO Box 9, 7400 AA Deventer, the Netherlands. Electronic address: i.santman@gdanimalhealth.com.
- 2GD Animal Health, PO Box 9, 7400 AA Deventer, the Netherlands.
- 3GD
Animal Health, PO Box 9, 7400 AA Deventer, the Netherlands; Department
of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht
University, PO Box 80151, 3508 TD Utrecht, the Netherlands.
Abstract
Extended-spectrum
β-lactamase and AmpC-producing Escherichia coli (ESBL/AmpC) are an
emerging problem and are hypothesized to be associated with
antimicrobial use (AMU), and more specifically with the use of third-
and fourth-generation cephalosporins. Whether ESBL/AmpC also occur in
organic dairy herds, which have restricted AMU, is not known.
Additionally, it is unknown whether, in addition to restricted AMU,
other factors in organic herd management are associated with ESBL/AmpC
herd status. The aim of this study was to estimate the prevalence of
ESBL/AmpC in organic dairy herds in the Netherlands. Subsequently, the
relationships between the ESBL/AmpC herd status and AMU and between
ESBL/AmpC herd status and farmers' management were assessed in organic
dairy herds. For this study, 90 randomly selected, officially registered
organic dairy herds were included. The ESBL/AmpC herd status was
determined based on the bacteriological culture result of a slurry
sample. The sensitivity of testing slurry samples for ESBL/AmpC herd
status is less than 100% for detecting herds with a low ESBL/AmpC
prevalence. For that reason, herds that tested positive for ESBL/AmpC in
slurry were defined as positive and herds with negative slurry samples
were defined as unsuspected. A comprehensive questionnaire on management
practices was conducted and records on specified antimicrobials that
were provided to these herds by the veterinary service providers were
obtained. From the data on antimicrobial supplies by the veterinarian,
the animal daily defined dose of antimicrobials per farm per year (DDDAF) was calculated. Descriptive statistics were used to describe the relation between the ESBL/AmpC herd status and DDDAF.
Multivariable logistic regression models were used to evaluate
management factors associated with the ESBL/AmpC herd status. We found
ESBL/AmpC in 12 of the 90 (13%; 95% confidence interval = 7-22%) slurry
samples from organic dairy herds. The median DDDAF in organic
dairy herds was 0.5, which was not significantly different between
ESBL/AmpC-positive and -unsuspected dairy herds. No association could be
found between the use of different types of antimicrobials, such as
third- and fourth-generation cephalosporins, and ESBL/AmpC herd status.
Factors that were associated with higher odds of being
ESBL/AmpC-positive were pig farms located within a 2-km radius of the
barn, applying parental treatment for clinical mastitis, and providing
milk replacer to the female calves after colostrum intake. The
prevalence of ESBL/AmpC in organic dairy herds appeared lower than the
prevalence in previous studies conducted in conventional dairy herds.
Apparently, ESBL/AmpC are also present in herds with low AMU; this
indicates that other factors than AMU are also associated with ESBL/AmpC
herd status.
Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
KEYWORDS:
antimicrobial resistance; antimicrobial use; dairy cattle; extended-spectrum β-lactamase; organic farming