Emerging Food Safety Issues: Clostridium difficile and MRSA J Scott Weese DVM DVSc DipACVIM
Clostridium difficile Gram positive anaerobic sporeforming bacterium first isolated in early 1900 s Cause of enteric disease in humans and various animal species Most commonly diagnosed cause of antimicrobial- and hospital-associated diarrhea in humans
http://jb.asm.org/content/vol191/issue17/cover.dtl
Cartman et al 2011
Food animals Species Bovine Pigs Chickens Country Prevalence Ref Canada 15% Rodriguez 2006 US 25% (diarrheic) Hammitt 2007 Austria 4.5% 45% Indra 2009 Canada 49% (cumulative) Weese 2009 Slovenia 2% Pirs 2008 Austria 3.3% Indra 2009 Slovenia 52% Pirs 2008 Canada 95% (cumulative) Weese 2009 Slovenia 62% Zidaric 2008 Zimbabwe 17.4% Simango 2006 Zimbabwe 29% Simango 2008 Austria 3.4% Indra 2009
Slaughter age Cattle 12% 1.2% (Rodriguez et al 2011) 5.5% (Weese et al 2010) Pigs 6.9% (Weese et al, in press) 70 60 50 Weese et al 2010 40 0% (Hoffer et al 2010) 30 Chickens 20 10 100% at 2 weeks but 41% at 18 0 1 2 3 4 weeks (Zidarici et al 2008) Sampling Period Individual Group housed Total Costa et al, in press
Food animal types Species es Bovine Country Ribotype 078/TT V Ribotype 027/NAP1/ TT III Human Ref Canada 26% 12% 100% Rodriguez 2006 US 94% 0 97% Keel 2007 Canada 65% 0% (1%) 100% Costa 2009 Canada 94% 0% 100% Weese in press Chickens Pigs Slovenia 0 0? Zidaric 2008 US 83% 0 98% Keel 2007 Slovenia 0 (77%) 0? Pirs 2008 Canada 94% 0 100% Weese 2009
Food Species Country animal Ribotype types Bovine 078/TT V Ribotype 027/NAP1/ TT III Human Ref Canada 26% 12% 55% Rodriguez 2006 US 94% 0 97% Keel 2007 Canada 65% 0% (1%) 100% Costa 2009 Chickens Pigs Slovenia 0 0? Zidaric 2008 US 83% 0 98% Keel 2007 Slovenia 0 (77%) 0? Pirs 2008 Canada 94% 0 100% Weese 2009
C. difficile in meat Product Region Prevalence Ref Beef, veal Various Beef, veal Pork Chicken Beef,,p pork Beef, pork, chicken Various Canada 20% Rodriguez 2007 US Beef: 42%, Pork 41%, Turkey: 44% Songer 2009 Canada Beef, 6.7%: veal 4.6% Rodriguez 2009 Canada 2% Metcalf et al,2010 Canada 15% Weese et al, 2010 Canada 12% each Weese et al 2009 Austria 0% Indra 2009 Netherlands 1.6% de Boer et al 2011
Types Study Rodriguez et al 2007 Product 078 (TT V) 027 (TT III) Human Ground beef and veal 0% 0% (67%) (100%) Songer et al 2009 Various 73% 27% 100% Rodriguez et al Beef, veal 0% 0% (27%) 100% 2009 Weese et al, 2009 Weese et al, 2009 Metcalf et al, 2010 Pork, beef 79% 7.1% (11%) 100% Chicken 96% 0% 100% Pork 0% 43% (57%) 100%
Sources: meat Animal gastrointestinal tract Healthy muscle tissue Slaughterhouse environment Processing environment Hands of personnel n=27, 0% prevalence at shipping Hawken et al, unpublished data
How much is there? Ground pork/beef 71% positives only detected with enrichment culture, < 10 CFU/g Quantifiable samples 20 spores/g: 5 samples 60 spores/g: 1 sample 120 spores/g: 1 sample 240 spores/g: 1 sample Weese et al 2009
Food Toxin production in food CDI Food Ingestion of spores CDI
Food Toxin production in food CDI Food Ingestion of spores CDI Colonization Transmission
What do we need to know? If ingestion causes disease. How meat becomes contaminated How to reduce contamination On-farm or off-farm farm control?
Staphylococcus aureus Commensal of nasal mucous membranes and skin of various mammals Nasal colonization in 29-38% people Variable in animals Opportunistic pathogen Skin and soft tissue infections Pneumonia, bloodstream infections
Colonization vs infection Colonization Presence on a body surface with no clinical effect or host response Transient or long-term Infection
S. aureus blaz Penicillin-resistant S. aureus meca Methicillin-resistant S. aureus
MRSA Hospital-associated (HA) disease Estimated 94000 invasive infections in US in 2005 (Klevens et al 2008) Community-associated (CA) disease Emerging epidemic
Livestock-associated MRSA Identification of identical strains of MRSA in pigs and pig farmers/families in the Netherlands (Voss et al 2005) Prompted by unexpected MRSA colonization in 6 month old child Parents also colonized
Later diagnosis of MRSA infection in pig farmer and son of pig vet All unrelated cases 23% of pig farmers at regional meeting colonized Pig farmers 760 times more likely to carry MRSA than the general Dutch population 1 pig colonized with same strain: ST398
ST398 now commonly found in pigs in Europe and beyond Contact with food animals important risk factor for MRSA infection in some countries Higher carriage rates by healthcare workers that live on farms Isolation of pig farmers upon hospital admission in some regions
Canada Europe
Pigs: Canada Ontario (Khanna et al 2008) 45% farm prevalence, 30% pig prevalence 0-100% of pigs on farms 20% of farmers Always same strain as pigs ST398 and CMRSA-2 Canada-wide; slaughter age pigs (Weese et al. in press) 4.5% (20/440) of pigs on 9.1% (4/44) of farms 80% ST398 (3 different spa types) 15% CMRSA-2 5% CMRSA-5
Feedlot cattle Nasal swabs and fecal samples in feedlot cattle, Alberta MRSA from 0/365 Weese et al, unpublished data
Retail meat: Canada Retail pork: 7.8% (31/396) ST398 and human epidemic strains Pork chops: 14% (14/89) Ground pork: 6.3% (8/127) Ground beef: 5.6% (11/178) Chicken: 1.6% (2/126) Most <100 CFU/g, one 3940/g All common human clone Weese et al, et al 2010 a, 2010b)
Retail meat: Canada Retail pork: 7.8% (31/396) ST398 and human epidemic strains Pork chops: 14% (14/89) Ground pork: 6.3% (8/127) Ground beef: 5.6% (11/178) Chicken: 1.6% (2/126) Most <100 CFU/g, one 3940/g All common human clone Weese et al, et al 2010 a, 2010b)
Possible sources Animal nasal passages Animal intestinal tract Animal hide Processing environment People
Pilot study, n=27, pig prevalence before slaughter 4% Hawken et al, unpublished data
Foodborne Concerns Food poisoning Food as a source of intestinal colonization Indirect infection Food as a source of nasal colonization Indirect infection Food as a direct source of infection
MRSA In food animals in Canada In Canadian retail meat In other food products? Human health concern Animal health concern +/- +/- Zoonotic pathogen? Foodborne pathogen?*? Consumer concern C. difficile