Randall Singer, DVM, MPVM, PhD

ANTIBIOTIC RESISTANCE Randall Singer, DVM, MPVM, PhD Associate Professor of Epidemiology Department of Veterinary and Biomedical Sciences University of Minnesota

Overview How does resistance develop? What might we expect when the feed efficiency label is eliminated? What is co- selection? What s on the horizon? 12:234-248, 2013

Antibiotics Antibiotic Compounds Low molecular- weight compounds that kill or inhibit the growth of microorganisms Many antibiotics are naturally produced by bacteria or fungi What is the role of antibiotic production in nature? Germ warfare theory Levels are low, almost undetectable Signaling molecules?

Definition of Resistance Clinically defined as the inability to treat a specific bacterial infection with an antibiotic Phenotypic traits of antibiotic resistance Focus on factors associated with isolates possessing a Minimum Inhibitory Concentration (MIC) above a specific resistant threshold

Definition of Resistance Genotypically defined as the presence of a resistance gene within the bacterium that is capable of rendering an antibiotic useless Prevalence and distribution of bacteria that possess a certain gene that confers resistance to a given antibiotic Focus on factors that affect spread of resistance genes

Is Resistance New? Bhullar el al., PLoS ONE (2012)

Is Resistance New? D Costa el al., Nature (2011)

Antibiotic Use and Resistance In 1913, Ehrlich publishes Chemotherapeutics: Scientific Principles, Methods and Results in Lancet He states that treatment should hit hard and early This idea was used for tuberculosis infections Resistance in Mycobacterium tuberculosis is often mediated by a single point mutation The goal of treatment is to prevent subpopulations of mutant bacilli (the resistant ones) from emerging

Antibiotic Use and Resistance Lipsitch and Samore, Emerg Inf Dis, 2002

Antibiotic Use and Resistance How does this relate to other situations? Vancomycin- resistant Enterococcus sp. Methicillin- resistant Staphylococcus aureus (MRSA) Multidrug resistant E. coli Both of these are based on the acquisition of genes These resistances are unlikely to occur de novo in a single person or animal following treatment Also important to recognize that these organisms are NOT obligate pathogens

Antibiotic Use and Resistance Lipsitch and Samore, Emerg Inf Dis, 2002

Antibiotic Use and Resistance Which is worse for resistance (and health): long- term low dose or short- term high dose? Dogma: high doses given over short term are best Many current research studies show that high doses may select strongly for resistance and spread of resistance - advantage to resistant populations Low doses for growth and disease prevention have reduced effects Do not significantly alter the normal bacterial flora in the host do not kill the susceptible population

Ag Antibiotic Use and Human Health Woolhouse and Ward, Science 2013

Ag Antibiotic Use and Human Health Agricultural Antibiotic Use Selection on farm A Resistance in pathogens Horizontal gene transfer Via food Via environment Increased resistant infections in humans Release of active antimicrobials into environment Selection in environment B C Resistance in non-pathogens Human colonization and horizontal gene transfer Human Antibiotic Use Singer and Williams-Nguyen, Curr Opin Microbiol 2014

Antibiotic Use and Resistance

Antibiotic Use and Resistance Van der Horst et al., FPD, 2013

FDA- CVM Document #209 The Judicious Use of Medically Important Antimicrobial Drugs in Food- Producing Animals Growth promotion / feed efficiency = production use not directed at any identified disease, but rather are expressly indicated and used for the purpose of enhancing the production of animal- derived products (e.g. increasing rate of weight gain or improving feed efficiency) Uses of antibiotics that are in- feed are often equated with production uses and are assumed to be long- term low- dose regimens of antibiotic administration for the sole purpose of improving weight gain

Proposed Veterinary Feed Directive Replace the federally- defined, code of veterinary professional conduct known as the veterinarian- client- patient relationship (VCPR) with the requirement that veterinarians ordering the use of VFD drugs must do so in compliance with all applicable veterinary licensing and practice requirements. Revise the definition of Category II drugs Reduce the recordkeeping requirement for copies of VFDs for all involved parties

FDA- CVM Document #213 Guidance for Industry on New Animal Drugs and New Animal Drug Combination Products Administered in or on Medicated Feed or Drinking Water of Food Producing Animals: Recommendations for Voluntarily Aligning Product Use Conditions With Guidance for Industry #209

The Danish Experience - Resistance

Estimating Impact on Human Health If these values were extrapolated to all of Europe (i.e., if 56% of G3CREC were derived from poultry), 1,518 additional deaths and an associated increase of 67,236 days of hospital admissions would be counted as a result of cephalosporin and other antimicrobial drug use in poultry. http://www.wired.com/wiredscience/2013/08/chicken-abx-deaths/

Estimating Impact on Human Health 15,183 episodes of G3CREC BSIs were associated with 2,712 excess deaths and 120,065 extra hospital days.

Estimating Impact on Human Health All but 1 of the ESBL-producing strains from other meat types clustered with strains from chicken meat. Twenty-five (56.8%) of 44 strains from rectal swab specimens and 9 (56.3%) of 16 strains from blood cultures clustered with strains from chicken meat.

Estimating Impact on Human Health 2,712 excess deaths * 56% attributable to poultry * 100% of resistance DUE TO antibiotic use in poultry AND 120,065 extra hospital days * 56% attributable to poultry * 100% of resistance DUE TO antibiotic use in poultry = 1,518 additional deaths and an associated increase of 67,236 days of hospital admissions would be counted as a result of cephalosporin and other antimicrobial drug use in poultry.

The Complexity of Resistance Co- selection When one compound can select for resistance to another compound

Multidrug Resistance Plasmids Call et al., Antimicrob. Agents Chemother., 2010

Multidrug Resistance Plasmids Johnson et al., Antimicrob Agents Chemother, 2005 Johnson et al., Antimicrob Agents Chemother, 2006 Johnson et al., J Bacteriol, 2006 Fernandez-Alarcon et al., PLoS ONE., 2011

Examples of Co- Selection Co- selection of ceftiofur and tetracycline resistance observed after ceftiofur treatment Lowrance et al. Am J Vet Res. 2007, 68(5):501-7 No increase in ceftiofur resistance after tetracycline administration Plam et al. Am J Vet Res. 2008, 69(8):988-96 While ceftiofur increased both ceftiofur and tetracycline resistance, tetracycline increased tetracycline resistance without ceftiofur Kanwar et al. PLoS ONE. 2013, 8(11):e80575

Antibiotic Alternatives?

Ag Antibiotic Use and Human Health Woolhouse and Ward, Science 2013

Residues in the Environment

Activity of Antibiotics in the Water For chlortetracycline, total bacteria counts did not differ among chemostats (P = 0.51) High- CTC chemostat selected for CTC resistance (P = 0.03) Count (log cfu / ml) Count (log cfu / ml) 10 8 6 4 2 0 10 8 6 4 2 0 Control 8 ug / L 800 ug / L 32000 ug / L 0 2 4 6 8 10 Time (Days) Control 8 ug / L 800 ug / L 32000 ug / L 0 2 4 6 8 10 Time (Days) Muñoz-Aguayo et al., Appl Environ Microbiol, 2007

Activity of Excreted Residues

Modeling Excretion of Residues Fecal Excretion (mg) Cow Fecal Excretion Fecal Concentration 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Time (days) Fecal Concentration (µg/g)

Modeling Excretion of Residues Milk Excretion (mg) Cow Milk Excretion Milk Concentration Milk Concentration (µg/l) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Time (days)

Modeling Excretion of Residues Fecal Excretion (mg) Calf Fecal Excretion Fecal Concentration Fecal Concentration (µg/g) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Time (days)

Excretion Data Gaps and Concerns Few data available concerning concentration of compound in each compartment Older compounds have very sparse data If environmental loading is of interest, additional trials might need to be conducted Dairy example highlights dilemma of discarding waste milk or feeding it to the calves

Take Home Messages Look for management changes that we can make that might reduce some antibiotic uses Stocking density Weaning age Carefully assess non- antibiotic practices in the poultry system that might select for resistance Copper in diet Disinfectants

Take Home Messages Relationship between antibiotic use and resistance may require: Long- term pressure (decades?) High density of selection (whole herd versus individuals) Specific doses Be prepared for the unintended consequences Hard to predict the diversity of pressures that can select for resistance

Take Home Messages Environmental concerns and waste management will continue to be key issues Residues will decrease with time in the environment, but the rate of decay will vary with many factors Biological activity in environment remains highly uncertain Excretion data from animals is lacking

United States Doug Call Charles Hofacre Richard Isaacson Tim Johnson Sue Kotarski Guy Loneragan Abigail Salyers H. Morgan Scott Tom Shryock United Kingdom Peter Silley