Shigella spp. OFour species (boydii, Shigella spp. and dysenteriae, flexneri, sonnei) Yersinia enterocolitica = serogroups OShigellosis = bacillary Dean O. Cliver dysentery PHR 250 OHost-adapted to humans (primates)
Characteristics of Characteristics of the disease: the disease: OInfectious dose is 10–100 O(illness on next 2 slides) organisms ODuration: 4–7 days; shedding up to 4 weeks; OIncubation period is ½–4 both shortened by (usually 1–3) days; up to a appropriate antibiotics week for S. dysenteriae 1 (multiple resistance common)
Illness: Illness: ODiarrhea with fever ODysentery—blood and and nausea mucus in stools; may cause hemolytic uremic OSometimes toxemia, syndrome; most severe vomiting, cramps, in infants (cf. E. coli and tenesmus O157:H7) OMild and asymptomatic infections occur Characteristics of Characteristics of the organism the organism ONonmotile, nonsporing, OTemperature range for gram-negative short rods; close genetic relationship growth (strain-dependent) to E. coli 7–46EC, optimum 37EC OInvades the colonic epithelium; many strains OpH range for growth 5–8, produce shigatoxin or acetic acid stops growth shiga-like toxin at pH 6
Transmission via food: Transmission via food: OFourth-ranked cause of OCDC estimates ~90,000 cases foodborne disease in U.S., per year, 14 deaths 1998–2002 (~735/yr), as OFoodNet (2005) ≈ 14,000 reported by CDC cases O CAST estimates 90,000– OSurvives well in neutral-pH 163,000 cases per year, foods, poorly in acid foods, #180 deaths, $390 average may grow (e.g., in cost/case watermelon)
Transmission via food: Isolation & identification: OVehicles may be anything OFood at 4EC or frozen if held contaminated with infectious >24 hr human feces: OEnrichment broths and water (2 outbreaks in U.S., 1994) selective media fairly typical for gram-negative bacteria baked goods, fruits and vegetables, chicken, OUsually lactose-negative; hamburger, potato salad, many other biochemical tests finfish implicated in apply outbreaks Isolation & identification: Treatment, prevention, OSpecies identification is summary largely serological. OTreatment with antibiotics O“Molecular” detection, (resistance) typing and subtyping OPrevention ≈ sanitation methods are available.
Treatment, prevention, YERSINIA summary ENTEROCOLITICA OShigella is widespread, OYersinia spun off from potentially deadly; shed Pasteurella in human feces. OIncludes Y. pestis (cause of plague) O Frequent transmission via OY. enterocolitica is principal food indicates frequent foodborne species; reservoir sanitation failure. in swine
Characteristics of Characteristics of disease: disease: OIncubation usually 3–7 days, OMay mimic acute generally <10 days appendicitis OAcute febrile diarrhea OPostinfectious arthritis in OEnterocolitis adolescents and young adults Characteristics of Characteristics of organism: organism: OGram-negative, OGrowth range of nonsporeforming rods; temperatures is -2–42EC, facultatively anaerobic; optimum 28–29EC motile by peritrichous OIn raw pork at 7EC, has flagella (only at grown to 109–1010 cells/g temperatures #35EC) within 10 days
Characteristics of Transmission via food: organism: OCDC: 8 outbreaks (87 cases), OpH range for growth is 4.2– 9.0, with an optimum of 7–8 1998–2002 OGrows in the presence of OCAST report: 3,250–20,000 5% but not >7% NaCl cases/yr (1 death?); $5,450 OVirulence is plasmid- per case dependent and is limited to a few serotypes
Transmission via food: Transmission via food: O OCDC estimates ~87,000 Y. enterocolitica isolated from foodborne cases/year, foods other than pork 2 deaths appears to be avirulent for humans OFoodNet (2005) ~1,080 OTransmission via water & dairy products; tofu packed in spring water Isolation & Isolation & identification: identification: OSamples held at 4EC if OEnrichment culture possible sometimes treated with 0.5% KOH for 15 sec before OCold enrichment: PBS; plating—kills many 4EC for 2–4 weeks (or competing organisms 10EC, 3 days; 15EC, 2 days?) OSelective media—use #32EC
Treatment & prevention Summary OTreated with antibiotics OShould be prevented by other than penicillin and its careful handling & cooking derivatives. of pork & avoiding cross- OFoodborne yersiniosis is a contamination of other highly specialized problem foods; however, milk and involving transmission from dairy products have also swine. been vehicles.