Origins of Resistance and Resistance Transfer: Food-Producing Animals.

Size: px

Start display at page:

Download "Origins of Resistance and Resistance Transfer: Food-Producing Animals."

Roxanne Norman
5 years ago
Views:

1 Origins of Resistance and Resistance Transfer: Food-Producing Animals. Chris Teale, AHVLA.

2 Origins of Resistance. Mutation Brachyspira hyodysenteriae and macrolide and pleuromutilin resistance. Campylobacter spp and fluoroquinolone resistance. Salmonella and fluoroquinolone resistance No need for anything extraneous; bacterial spontaneous mutations then antimicrobial use selects resistant sub-population.

3 Transfer of Resistance. Abattoir Worker. Nurse. Rare or unusual mutations in clones of organisms can provide a useful means of tracing spread... Denmark; cluster of 27 cases of S. Typhimurium DT104 infection, all with same rare mutation ti in the gyrase gene.traced back to pigs on one farm.

4 Transfer of Resistance. Types of transfer... Direct contact. Food borne spread. Secondary spread.

5 Origins of Resistance.. Acquisition of resistance mechanisms by bacteria. Enzymes; may modify target or modify antimicrobial. Aminoglycoside modifying enzymes in Salmonella. Strains from different epidemiological niches in contact provides opportunities for genetic exchange.

6 Transfer of Resistance. AAC(3)IV Aminoglycoside modifying enzyme. Aminoglycoside gy acetyltransferase. Confers resistance to gentamicin and apramycin. E. coli in calves S. Typhimurium in calves E. coli, S. Typhimurium, Kl. pneumoniae hospitals in Belgium.

7 Evidence that AAC(3)IV emerged because of veterinary use of apramycin rather than use of gentamicin in man: -incidence of resistance in human and animal populations. -AAC(3)IV not widespread in other human enterobacteriaceae. -AAC(3)IV resistance gene linked to hphb gene encoding enzyme hygromycin B phosphotransferase, which confers resistance to the veterinary drug hygromycin B (also an aminoglycoside...but is active as an anthelmintic).

8 Transfer of Resistance. AAC(3)II Aminoglycoside modifying enzyme. Aminoglycoside gy acetyltransferase. Confers resistance to gentamicin...but not apramycin. Widespread in French hospitals in the 1970s... Limited diffusion to calves in western France.

9 Origins of Resistance... Salmonella Typhimurium DT 104. tetr; unusual in Salmonellas... mainly in Vibrio spp. flor; first detected in a fish pathogen. Ampicillin resistance BLA carb2 ; often found in Pseudomonas spp.

10 Origins of Resistance.. Efflux pumps Activation of efflux pumps Removal of antimicrobial from bacterial cell. Alternative metabolic pathways Folate metabolism

11 Origins of Resistance. Many antimicrobials derived from bacteria. These possess resistance to the antimicrobial i they produce. Therefore many resistance genes already exist in nature Growth promoter avoparcin; DNA related to resistance cluster detected in product (Lu et al. 2004).

12 Strains of E. coli HUMAN E. coli STRAINS POULTRY E. coli STRAINS Scenarios; Poultry strain colonises humans. Poultry strain transiently colonises humans. Poultry strain passes through human intestine. Poultry strain transfers resistance to human strain while passing through. 12

13 Gene Transfer and Conjugation... vana resistance gene confers resistance to vancomycin and the former growth promoter avoparcin. Enterococcus faecium from animals given to human volunteers. Resistance gene transferred from animal E. faecium to human E. faecium, without any antibiotic use and during transient colonisation of the human intestine by the animal strain (Lester et al. 2004). 13

14 Common Epidemiological Pool. Same strain in: Animals e.g. poultry Meat produced from those animals. Humans Exchange between the pools. Direction of transfer? Prevalence in different hosts. Exposure. Attribution rate. Vegetarians. 14

15 Evidence. (EFSA Biohaz Opinion). Few studies describe clear evidence of direct transmission of ESBL E. coli from food-producing animals or food to man. Data does exist regarding common clones of ESBL E. coli in humans and food-producing d animals, providing indirect evidence of transmission. Limited evidence for spread of ESBL E. coli via direct contact with animals or indirectly via the environment. Nevertheless, people working with poultry have a higher risk for intestinal ti carriage of ESBL E. coli (30% poultry farmers had ESBL bacteria; versus 5% general population p Dierikx et al. 2010).

16 General Bacterial Organisation: The resistance gene. The plasmid carrying the resistance gene. The bacterial isolate. 16

17 ESBLs hydrolyse the beta-lactam ring of penicillins and cephalosporins: S H 2 O S O N O NH OH 17

18 Overdevest Dutch retail Meat Survey: Chicken 89 samples Beef 85 samples Pork 57 samples. ESBL E. coli prevalence: Chicken 80% Beef 5% Pork 2% 18

19 Overdevest et al. Compare genes, plasmids, bacterium. Same gene (CTX-M-1, TEM-52) 30% Same gene, same plasmid 19-20% Same gene, same plasmid, same strain of E. coli 11% c. 1 in 3 patients had a poultry-associated (PA) ESBL c. 1 in 5 patients had a PA ESBL encoded by a PA plasmid (pmlst) c. 1 in 10 patients had a PA ESBL encoded by a PA plasmid in a PA E. coli strain

20 Overdevest Conclusions. Extensive reservoir of ESBL genes in poultry, shown from on-farm studies. Most E. coli strains containing the ESBL genes CTX-M-1 ortem-52 belong to clusters containing isolates from both sources. Suggests contamination of chicken meat and appearance of ESBL genes in humans are related. Cross-transmission in hospitals in Holland controlled effectively, therefore acquisition from food more easily detected. Circumstantial evidence for an animal reservoir for a substantial part of ESBL genes in humans. 20

21 MRSA ST398. Rarer types of resistance again allow epidemiological i i l tracing... Portugal... Isolates resistant to clindamycin, but susceptible to erythromycin. Plasmid; similar in a human clinical isolate and an isolate from a pig.

22 MRSA ST398 Livestock-associated MRSA. Geenen et al.2012

23 ESBL E. coli...

Human health impacts of antibiotic use in animal agriculture

Human health impacts of antibiotic use in animal agriculture Beliefs, opinions, and evidence Peter Davies BVSc, PhD College of Veterinary Medicine, University of Minnesota, USA Terminology Antibiotic Compound