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VTEC – Preparing for the inevitable Dr. Fiona Thomson-Carter ESR

VTEC – Preparing for the inevitable Dr. Fiona Thomson-Carter ESR . Preparing for the Inevitable. Know thine enemy Know it’s environment Know how it is evolving Have robust systems in place Gold standard techniques International awareness Multi-disciplinary, cross-sectoral co-ordination .

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VTEC – Preparing for the inevitable Dr. Fiona Thomson-Carter ESR

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  1. VTEC – Preparing for the inevitableDr. Fiona Thomson-Carter ESR

  2. Preparing for the Inevitable • Know thine enemy • Know it’s environment • Know how it is evolving • Have robust systems in place • Gold standard techniques • International awareness • Multi-disciplinary, cross-sectoral co-ordination

  3. E. coli – the beginning In 1885, Theodor Escherich identifies a bacterium, that is a natural inhabitant of the human gut, which he names Bacterium coli. He shows that certain strains are responsible for infant diarrhoea and gastroenteritis. Escherich, T. 1885. Die Darmbakterien des Neugeborenen und Sauglings, Fortschr.d. Med. 3: 515-522; 251-251,

  4. VTEC – the story so far • Ninety-seven years (or 1.132M bacterial generations) laterin 1982, E. coli O157 identified as an emerging foodborne pathogen; first documented association with a case of human disease • 26.09.2003 Google >60, 000 hits • 06.05.2008 >1.21M in 0.23 seconds • exponential growth!

  5. VTEC – background information • http://www.ifst.org/uploadedfiles/cms/store/ATTACHMENTS/vtec.pdf • Institute of Food Science and Technology Information Statement

  6. E. coli - diversity of types • >1000 antigenic types • Somatic antigens O (171) • Capsular antigens K (80) • Flagellar antigens H (56) • Form basis of international reference lab method • WHO Collaborating Centre for E. coli and Klebsiella spp., Copenhagen, distribute antisera • International ring trials via EU

  7. VTEC - definition • VTEC Verocytotoxigenic E. coli (O157, O26, O103, O111, O118, O145) • STEC Shiga-like toxigenic E. coli • EHEC Enterohaemorrhagic E. coli • ETEC Enterotoxigenic E. coli (Cholera-like) • EIEC Enteroinvasive E. coli (Shigella-like) • EPEC Enteropathogenic E. coli (Neonatal diarrhoea) • EAEC Enteroaggregative E. coli • DAEC Diffuse adhering E. coli • OHEC

  8. VTEC - virulence • Vero(cyto)toxin; • Shiga-like toxin genes: s(v)tx1/stx2 (stx2e/stx2ev/stx2vha/stx2vhb) • LEE (PI): 3 regions – • type III secretion system; • induction of AE lesion; • eae, intimin (OMP, 7 variants) and tir (3 variants), intimin receptor • fliC – flagellar antigens (H) mosaic structure

  9. VTEC - virulence • pO157 (92 kb) – • encodes hlyA, its transport and activation, 13 components of Type II secretion system, catalase peroxidase, serine protease and other genes • pO113 (156 kb) – • encodes subtilase cytotoxin in highly-virulent LEE –ve STEC (O113:H21, O91:H21), which targets folding of nascent proteins in endoplasmic reticulum – new toxin (Paton et al.) and other genes

  10. E. coli O157 – genetic quirks • mutS gene– component of methyl-directed mismatch DNA repair system of bacteria • Barrier to HGT • Mutator phenotype - typified by high mutation rates and promiscuous recombination • Depleted 26 –fold in stationary cells cf. exponential cells • O157 greater depletion than seen in K12 • 10 –2 cf. 10 –6 natural occurrence

  11. VTEC – genomic quirks • Variation in genome size observed among E. coli O157 isolates (>100 kb) • Of questionable significance (microbiologically, clinically) • Effects on molecular epidemiology • Development of “Tenover’s Rules” for interpretation of PFGE profiles • 85% variably present genes (VAP) are phage related; diversify rapidly • Contribution to virulence by diverse phage gene content – not yet known

  12. E. coli O157 - in NZ • E coli O157 first isolated in 1993 • O157:H7 or O157:H- predominant strain • Human, animal, food and environmental sources • Majority of isolates are stx2, eaeA, EHEC hlyA • Multiple clonal lineages identified to date • http://www.esr.cri.nz Infectious Disease in NZ

  13. O157 in NZ: Reference Laboratory • Serotyping; • EIA and Verocells used to detect toxin production; • Multiplex PCRs (e.g. stx1, stx2, eaeA, hlyA); • PFGE; • BioNumerics (NZ Microbial Typing Database); • Other VTEC; • Enter-Net ring trials and data submission • MLST; MLVA

  14. VTEC – clone hunting • PulseNet – USA • O157 infection • 5 states exchanging PFGE data • Grown into PulseNet with Enter-Net (EU), Pulsenet Pacific Rim, PulseNet Asia • PulseNet Aoteoroa • Exchange of O157 PFGE data with USA recently • Bala Swaminathan to visit NZ next month

  15. CENTRAL SCOTLAND OUTBREAK OF E. coli O157 INFECTION • Tenth anniversary • First isolation of the outbreak strain of E. coli O157 responsible for the CSO outbreak was made in Carluke, Lanarkshire on 21 st November 1996 • http://news.scotsman.com/scotland.cfm?id=1694712006 • By the end of the outbreak more than 21 people had died and more than 500 cases of infection microbiologically - confirmed

  16. CENTRAL SCOTLAND OUTBREAK OF E. coli O157 INFECTION INITIAL REF. LAB. LOAD (26/11/96-21/1/97) 2099 1256 766 77 ISOLATES:FAECES SERA PM SPECIMENS 1:5 AT 21/1/97 >6000 TESTS PERFORMED  10 YEARS WORK IN 8 WEEKS

  17. CENTRAL SCOTLAND OUTBREAK OF E. coli O157 INFECTION FINAL REF. LAB. LOAD (20/5/97) ISOLATES 3188 FAECAL/PM* 881 5259660 SERA 1190 * NEG. AFTER CULTURE/IMS/PCR

  18. VTEC – public health impact • West Lothian outbreak 1994 • HUS £62,354 (1994/5) • Investigation & control £171,848 • Cost over 30 years • £168,032 per case • £11.9 million

  19. VTEC – public health impact EstimatedTotalCost Type of Service Components 479,788 Hospital Specialised care & treatment Specialised (non-laboratory) investigations Diagnostic (laboratory) investigations 231,457 Micro-biology Haematology Biochemistry 172,200 PrimaryCare (SpecialclinicatWishaw CommunityNursing Medical InfectionControl PublicHealth 107,891 Epidemiologicalinvestigation OutbreakManagement PublicInformation& Communications 138,159 Media Health Promotion campaign Helpline TOTAL1,129,495

  20. O157 Outbreaks in Scotland 1996-2000 Main modes of transmission: Foodborne; Multiple modes of possible transmission; Person-to-person; Environmental; Waterborne; Zoonotic; http://www.scotland.gov.uk/library3/health/ecoli-00.asp

  21. RISK FACTORS FOR O157 INFECTION IN SCOTLAND Locking et al. (2001) Epid. Inf. 127:215-220 Prospective matched case-control study P-value <0.0005: contact/likely contact with animal faeces; contact with animals; visit to farms, smallholdings or zoos; garden next to farm, field etc. P-value 0.83: ate burgers

  22. VTEC - lessons learned? • CSO, other Scottish outbreaks • Welsh outbreak 2005 – butcher’s shop, cross-contamination? • http://news.bbc.co.uk/1/hi/wales/4546606.stm • 158 ill, 1 death (children from 42 schools screened) • “The firm was forced to stop trading on 22 September after Bridgend Council applied to magistrates for a prohibition order, claiming there were problems with hygiene and vacuum-packing procedures at the outlet.”

  23. VTEC – lessons learned? • US outbreak associated with consumption of raw spinach (bagged and washed) • 200 cases, 3 deaths • Salinas Valley, California • Dairy cattle grazing on slopes above spinach fields • Feral pigs • “hot strain” of O157, previously only 1% of cases in US – hyper-virulent?

  24. VTEC – the future • Hot houses of the human gut e.g. commensal microflora • and the broader environment .. • Ecotypic structure of strain populations from a range of wild hosts (81 mammalian species) • Hot mix of potential HGT and mutator strains • Avidity for uptake of foreign DNA”species”, “type” – new, different enteropathogens • SF+ O157 emerging in EU

  25. VTEC – the song! “Poop in the field And manure's to blame You give spinach a bad name I ate it fresh and it gave me pain You give spinach a bad name You give spinach a bad name” (Tune: Bon Jovi’s “You Give Love a Bad Name”)

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