Antimicrobial Resistance Projects: Towards Antimicrobial Stewardship

This article was written by Drs. CJ Gebhart, KE Olsen and JL Torrison from the Veterinary Diagnostic Laboratory, University of Minnesota.

The emergence of antimicrobial resistance in humans, animals and the environment is a major global public health threat to both human and veterinary medicine.  Efforts to address this important issue involve government, industry, academia, and most notably, veterinary diagnostic laboratories (VDLs).  These efforts include surveillance to assess the extent resistance in human and animal pathogens and the development of policies to monitor and control antimicrobial resistance.

A collaborative effort involving the stakeholders listed above is the key to addressing this emerging threat of antimicrobial resistance and VDLs play major roles in these collaborative efforts.  As reported in a Commentary by GK Hendrix in the Journal of Veterinary Diagnostic Investigation in 2018, VDLs are the “nexus in the battle against antimicrobial resistance” (1). The University of Minnesota VDL Bacteriology Section performs almost 30,000 bacterial cultures annually, and most of the pathogenic isolates are archived for future use.  These uses include further testing (subtyping, virulence gene assays, serotyping, etc.), use in disease control efforts (autogenous vaccines, etc.), various research projects, and surveillance studies.  Almost 5,000 of these pathogenic bacteria are subjected to antimicrobial resistance testing annually, and these antimicrobial minimum inhibitory concentration data are archived for decades for further use.

Performing one of many antimicrobial susceptibility tests in the University of Minnesota Veterinary Diagnostic Laboratory, Bacteriology Section.

For our part in this aforementioned collaborative effort in antimicrobial stewardship, the University of Minnesota VDL is actively involved in two collaborative government-organized antimicrobial resistance projects as well as several collaborative academic research projects on antimicrobial resistance.  The common goal of the collaborative government projects is to determine the population and distribution of resistant bacteria in the U.S. 

The first of these projects is the U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service National Animal Health Laboratory Network (NAHLN) project (2).  This project has 19 AAVLD-accredited laboratories throughout the U.S. and Canada participating with the objective of monitoring antimicrobial resistance profiles in animal pathogens routinely isolated from VDLs.  Ultimately, this project will result in a national centralized data collection and reporting process, using harmonized methods and antimicrobial resistance interpretation and reporting standards.  It aims to monitor data for trends in antimicrobial resistance phenotypes (and eventually genotypes) by identifying new or emerging resistance profiles, monitoring usefulness of antimicrobials over time, and reporting these trends to facilitate antimicrobial stewardship efforts. 

This USDA project began in January, 2018, and initially involved collection of isolates and antimicrobial resistance data from Escherischia coli (all species), Salmonella enterica (all species), Mannheimia haemolytica (cattle) and Staphylococcus intermedius group (companion animals) from routine VDL submissions.  A target of about 3,000 isolates will be collected from the participating VDLs annually and archived for further testing.  The antimicrobial testing data will be tracked and stored by USDA for each isolate and an annual report will be prepared for stakeholders.  This report will include antimicrobial resistance trends for antibiotics important for human and animal health and the distribution of minimum inhibitory concentrations for each antimicrobial monitored for each bacterial pathogen for each animal species included in the study.

The second of these collaborative antimicrobial resistance projects is the Food and Drug Administration (FDA), Center for Veterinary Medicine, Veterinary-Laboratory Investigation and Response Network (Vet-LIRN) project (3). This project has 21 AAVLD-accredited laboratories participating with the objective of performing surveillance of antimicrobial susceptibility testing results and whole genome sequencing of pathogens from the National Antimicrobial Resistance Monitoring System scope of interest (4). 

This FDA project began in January, 2017, and initially involved collection of isolates and data for three zoonotic bacterial pathogens, with several other bacterial species added to the project in July, 2018.  About 2,000 isolates have been collected since project inception, and the FDA has randomly selected about 200 of these isolates for whole genome sequencing.  The remaining isolates have been archived for future studies.  As an additional benefit related to this project, the University of Minnesota VDL received funds from FDA to purchase an Illumina iSeq Sequencer and participate in a collaborative project designed to increase the number and capabilities of network laboratories involved in the whole genome sequencing portion of this FDA project.  Standardization and harmonization of these bacterial genome sequencing abilities among participating laboratories is further designed to increase the network capacity and facilitate future outbreak investigations.

In summary, in support of antimicrobial stewardship efforts, the University of Minnesota VDL Bacteriology Section provides clinical isolates and antimicrobial susceptibility testing data for two collaborative government-initiated projects, one in collaboration with the USDA and the other with the FDA.  Further, the VDL as a whole provides leadership in antimicrobial stewardship on a daily basis, cooperating with disease outbreak investigations, collaborating with academic and industrial researchers, and educating veterinarians, clients and the public on issues of antimicrobial stewardship (1).


1.  Hendrix, GK. 2018.  The Role of Veterinary Diagnostic Laboratories in the Fight Against Antimicrobial Resistance

2.  USDA. 2018. USDA’s Role in Combatting Antimicrobial Resistance. 

3.  FDA. 2018.  Veterinary Laboratory Investigation and Response Network

Science Page: Salmonella antimicrobial resistance and emergence of a new serotype S.4,[5],12:i:-

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

Monitoring antimicrobial resistance is a research topic of utmost importance in the swine industry. Dr. Julio Alvarez at the University of Minnesota is leading some of this effort and this week, his team is presenting the latest results regarding Salmonella antimicrobial resistance in the strains isolated by the University of Minnesota – Veterinary Diagnostic Laboratory between the years 2006 and 2015 and the emergence of a new serotype S.4,[5],12:i:-

Key Points

  • Swine is the reservoir most commonly associated with the S.4,[5],12:i: serotype.
  • The prevalence of S. agona and S. 4,[5],12:i:- in isolates of swine origin recovered from clinical samples received at the Minnesota Veterinary Diagnostic Laboratory (MVDL) in 2006-2015 has increased.
  • In these serotypes an increased proportion of isolates were resistant to ceftiofur and enrofloxacin, compared with other serotypes.
  • The increase in the frequency of isolation of the S.4,[5],12:i:- serotype in humans may be paralleled by a similar increase in swine clinical samples received in the MVDL.

The information synthesized in the figure below is the evolution, over the years, of the percentages of Salmonella isolated at the UMN – VDL, belonging to each of other the following serotypes: typhimurium, agona, derby, typhymurium var5, and 4,5,12:i:-. The increase in the proportion of S.4,5,12:i:- can be seen starting back in 2011-2012.

Salmonella antibiotic resistance

Click here to read the full report about Salmonella serotypes isolated at the UMN – VDL