Danish Veterinary Laboratory Bacterial populations and resistance development: Intestinal tract of meat animals Frank Møller Aarestrup
12 Antibiotic production 10 Mill. Kg 8 6 4 2 0 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 Animal feed Therapy Total
Use of antimicrobials in agriculture Therapy treatement of disorders or disease in sick animals Metaphylaxis Treatment of groups of healthy animals after clinical signs in pen mates Prophylaxis Use of antibiotics in advance of symptomatic disease e.g. medicated early weaning Growth promotion antibiotics used as feed additives increases growth rate, but mechanism not entirely known
Classes of antimicrobials used in agriculture All classes also used in humans, including the substances considered the most potent for human therapy today (Fluoroquinolones, 3rd gen. Cephalosporins, Glycopeptides, streptogramins, etc.)
200,00 180,00 160,00 Usage of Antimicrobials for Food-animals in the EU Milligram of antibiotics for growth promotion per kg meat produced Milligram of antibiotics for therapy per kg meat produced 140,00 120,00 100,00 80,00 60,00 40,00 20,00 0,00 Austria Belgium & Lux Denmark Finland France Germany Greece Ireland Italy Netherlands Portugal Spain Sweden United Kingdom Average EU
Distribution of Animal Health products in United Kingdom Producer Veterinary whole sale Non-veterinarian whole sale Products sold freely Veterinarian Pharmacy Retail sale >40% of income!! Food animal producer
Distribution of Animal Health products in Denmark Producer Medicines Vaccines Products sold freely Whole sale Veterinary Services Retail sale Pharmacy Veterinarian < 5% profit! Food animal producer
Selection of antimicrobial resistance and bacterial transfer in the farm-to-fork chain Wild fauna Environment (Natural antimicrobials) (Detergents) Environment Sewage, etc. (Antibiotic waste) Oral use Prophylaxis Mass medication Long duration Low doses Long term carriage Therapeutic use in rare cases Clinical disease and short term carriage Selective pressure favoring antibiotic resistance development
% resistance 16 14 12 10 8 6 4 2 0 Fluoroquinolone resistance in Campylobacter Endtz et al. 1991 Use of enrofloxacin for animals 1982 1987 1989 Human Poultry
Transfer of resistance genes Streptothricin Used in Eastern Germany for growth promotion Resistant E. coli in pigs - Transferable plasmid Resistant E. coli in pig farmers Resistant E. coli in community acquired UTI Plasmid in Shigella Tschäpe et al. (1984), Hummel et al. (1986), Witte (1998)
Special concerns Fluoroquinolone-resistant Salmonella 3rd gen. Cephalosporin-resistant Salmonella Fluoroquinolone-resistant Campylobacter Macrolide-resistant Campylobacter Vancomycin-resistant E. faecium Synercid-resistant E. faecium
Potential problems with AGP Growth promoter Avilamycin Avoparcin Tylosin/spiramycin Virginiamycin Bacitracin Therapeutic Ziracin* Vancomycin Erythromycin Synercid *: No longer developed for human use Carbadox, olaquindox Flavomycin, monensin, salinomycin
Occurrence of glycopeptide resistant enterococci (GRE) 1986: Humans (Leclercq et al. 1988, Uttley et al. 1988) 1993: Environment and pigs (Klare et al. 1993, Bates et al. 1994) 1994: Poultry, pigs and humans (Klare et al. 1995)
Steps in a causal link Selection of resistance by the use of AGP Transfer of resistance from animals to humans Directly, Food, Environment Infections caused by resistant bacteria of animal origin Clone, Gene
Epidemiological studies Broilers GRE Pigs GRE + - + - Avoparcin + 11 1 8 4 use - 2 10 2 8 Fishers exact: 0.0006 Fishers exact: 0.04 Bager et al. 1997
Map of glycopeptide resistance transposon Tn1546 ORF1 ORF2 vanr vans vanh vana vanx vany vanz
Spread of GRE to humans GRE in food of animal origin (Klare et al. 1995, Wegener et al. 1997, Klein et al. 1998) GRE in humans outside hospitals in Europe, not USA, not in vegetarians (Gordts et al. 1995, van der Auwera et al. 1996, Coque et al. 1996, van den Braak et al. 1997, Endtz et al. 1997)
Spread of GRE to humans Identical strains of GRE from humans and food animals (van den Bogaard et al. 1997, Simonsen et al. 1998, Descheemaeker et al. 1999, Willems et al. 2000) Identical types of Tn1546 among food animals and humans (Werner et al. 1997, Jensen et al. 1998, Woodford et al. 1998, Simonsen et al. 1998, Descheemaeker et al. 1999, Willems et al. 2000)
AFLP typing of glycopeptide resistant E. faecium Geno-group Origin and No. of isolates Calf Volunteer Patient Chickens Pigs 29 29 2 109 10 2 3 32 1 4 164 1 39 Willems et al. 2000 & pers. comm.
Interventions in Denmark concerning antimicrobial growth promoters (AGP) Avoparcin ban in Denmark, May 1995 (EU 1997) Virginiamycin ban in Denmark, January 1998 Voluntary stop of AGP for finishing pigs and poultry 1998 EU ban on the use of 4 AGP s from July 1999 (Tylosin, Spiramycin, Virginiamycin, Bacitracin) Agreement of total stop with all use of AGP s in Denmark for pigs before 2000
Consumption of antimicrobial growth promoters 120 Consumption in Tonnes 90 60 30 0 1990 1992 1994 1995 1996 1997 1998 1999 2000 Avilamycin Avoparcin Carb/ola Tylosin Virginiamycin Andre
Occurrence of VRE 80 6 Percent resistance 70 60 50 40 30 20 10 Decreased use of tylosin 5 4 3 2 1 Consumption in Tonnes 0 0 1995 1996 1997 1998 1999 2000 E. faecium from broilers E. faecium from pigs Avoparcin use Aarestrup et al., 2001
GRE from pigs and transconjugants
Effect of prohibiting avoparcin in Germany and The Netherlands 14 80 % human samples 12 10 8 6 4 2 0 1994 1995 1996 1997 70 60 50 40 30 20 10 0 Humans Pigs Broilers 1997 1999 Klare et al., 1997; van den Bogaard et al. 2000
Occurrence of macrolide resistance Percent resistance 100 90 80 70 60 50 40 30 20 10 0 1995 1996 1997 1998 1999 2000 E. faecium E. faecalis Tylosin use 80 70 60 50 40 30 20 10 0 Consumption Aarestrup et al., 2000
Percent resistance 90 80 70 60 50 40 30 20 10 0 Avilamycin resistance 1995 1996 1997 1998 1999 2000 3 2,5 2 1,5 1 0,5 0 Consumption Aarestrup et al., 2000 E. faecium from broilers Avilamycin use
Salmonella Typhimurium DT104 Resistant to: Ampicillin, chloramphenicol, streptomycin, sulphonamides, tetracycline Emerged worldwide within the 1990 ties
Quinolone-resistant Salmonella Typhimurium DT104 (UK) Percent of isolates 18 16 14 12 10 8 6 4 2 0 November 93 Enrofloxacin licensed for animal use 92 93 94 95 96 97 Chickens Cattle Pigs Humans
10 8 Slaughterhouse contamination Number of cases 6 4 Outbreak recoqnised Swine herd identified 2 0 18 20 22 24 26 28 30 32 34 36 Mølbak et al., 1999 Week of 1998
Outbreak of QR, MR S. Typhimurium DT104, Denmark 1998 - Clinical features 27 patients identified (2 occupational, 1 nosocomial) 7 (26%) history of antibiotic use prior to onset 11 (44%) hospitalized 6 treated with fluoroquinolones Lack of treatment effect reported in at least 4 patients 2 patients died; one previously healthy patient died from complications of intestinal perforation Mølbak, NEJM, 1999
60 Quinolone resistance among E. coli 450 Percent resistance 50 40 30 20 10 400 350 300 250 200 150 100 50 Consumption 0 1995 1996 1997 1998 1999 2000 Broiler Cattle Pigs Enrofloxacin 0
Conclusions Use of antimicrobials selects for resistance The same clones and resistance genes can be found in bacteria from animal and human origin A more limited use of antimicrobial agents for food animals are followed by a decrease in the occurrence of resistance