Zoonotic Diseases Exam 1 Review

How are bacterial names written?

capital genus, lowercase species

What factors contribute to emerging infectious diseases?

overuse of antibiotics, increased population density, human-animal interaction, exotic pets, poverty, malnutrition, urbanization, climate change

Where do new infectious diseases come from?

85% from animals, 70% of those from wildlife

What are some negative impacts of zoonotic diseases?

threat to biodiversity of ecosystems, food security, farmers, ecotourism, economy

How can zoonotic diseases be prevented?

surveillance by training community to detect/report, improve diagnostics and control by quarantine, cull livestock, disinfection, and vaccination

Define sporadic

occurring occasionally, individually, scattered

Define outbreak

sudden increase in activity, disease, infection

Define epidemic

disease/condition affects a large number of people at once

Define endemic

expected “normal” incidence of disease transmitted at expected rate

Define pandemic

disease/condition occurs throughout population of country/world, plague

What is SARS?

severe acute respiratory syndrome, caused by SARS coronavirus, outbreak in Hong Kong 2002 nearly became pandemic, greatest economic impact

What is BSE?

bovine spongiform encephalopathy/mad cow, prion disease, UK had to cull 4.4 million cattle

What is H1N1?

highly pathogenic avian influenza/HPAI, 220 million birds culled, >60% fatality in humans

What contributes to the cost of disease?

lab costs like diagnostics, PCR, culture, cost of food lost, medicine costs like hospital stays, doctor visits, medicine, cost to clean facilities/equipment, cost of lost labor

What are the risk factors associated with farm practice?

dietary impact, water quality, worker/animal health, farm location/environment, equipment used, biosecurity practices, type of animal

How is disease controlled on farms?

remove deadstock quickly, add pre/pro/synbiotics in feed, treat waste, minimize stress, vet care, low sticking density

What are the risk factors associated with the processing plant?

carcass contamination via contact with hide, other carcasses or worker gloves, knives, clothing

What are the intrinsic parameters?

inherent properties of the animal’s tissue: pH, moisture content, nutrient content, red-ox potential, antimicrobial constituents, biological structures

How does pH contribute to disease risk?

different bacteria are inhibited/thrive in different pH environments

How does moisture content contribute to disease risk?

microbes are 80% water, their requirement is water activity, most fresh food has a_w > .99

How does red-ox potential contribute to disease risk?

ease in which substrate gains/lose electrons, microbes are sensitive to this and grow in different ranges

What is ORP?

measure of tendency of a chemical species to acquire electrons and thereby be reduced

How does nutrient content contribute to disease risk?

microbes need water, energy source, vitamins, minerals, all of which are abundant in animal food

How do microbial constituents contribute to disease risk?

milk has some antimicrobials like lactoferrin, conglutinin and lactoperoxidase, eggs have lysozyme

How does biological structure contribute to disease risk?

natural covering of some foods provides protection such as skin covering, fresh cut more susceptible to colonization/growth

What are the risk factors associated with the host?

age, immunodeficiencies like AIDS chemotherapy, hep B/C, pregnancy, stress, nutrient deficiencies, fatty foods protect against stomach acid, antacid consumption

What bacteria should pregnant women avoid?

listeria, Toxoplasma gondii, EHEC 0157:H7, Salmonella

What are the stages of infection?

exposure, adherence, invasion, colonization, tissue damage

Which bacteria adhere via type 1 pili?

E. coli, Salmonella, Shigella

Which bacteria adhere via flagella?

Campylobacter jejuni, Salmonella

How do bacteria survive intracellularly?

resist innate immunity of lysozymes, resist acquired immunity, adapt to bacterially hostile environment, gain access to protected/nutrient environment

What is lethal dose?

LD₅₀ is the cfu of pathogenic agent that kills 50% of test group

What are exotoxins?

released into surroundings, heat-labile, highly immunogenic/toxic, protein with a and b subunits

What are endotoxins?

toxic to specific hosts, heat stable, lipid a

What is quorum sensing?

cell-cell communication that helps make biofilms

What are sigma factors?

subunit of RNA polymerase needed to recognize the promoter

Describe the morphology of Campylobacter

gram (-), spiral, single flagella, microaerophilic

What are the common species of Campylobacter?

jejuni (99%), coli, fetus

What are the symptoms of campylobacteriosis?

most common cause of diarrhea, enteritis, colitis, pain, septic abortion, reactive arthritis, GBS where immune system attacks nerves

What role does flagella play in virulence of campylobacter?

adhesion/colonization, assembled by >40 genes, initiated by sigma factors

How does campylobacter invade?

receptor mediated endocytosis/coated pit formation

What is Cdt?

cytolethal distending toxin A-D in campylobacter, causes irreversible cell arrest, DNA damage, lose plasma membrane integrity

What are the secreted proteins of campylobacter?

campylobacter invasion antigen, need stimuli to secrete like fetal bovine serum

What role does iron play in campylobacter virulence?

iron normally tightly bound to lactoferrin/transferrin, bacteria grab it back and transfer it inside bacterial cell

How is campylobacter treated?

erythromycin antibiotics for severe cases, fluids

Describe the morphology of Salmonella enterica

gram (-), rod, facultative anaerobe

What are serotypes/serovars?

serological classification scheme based on surface proteins, O antigen readily recognized, H antigen is flagellar, specific combinations of O/H antigens are serotypes

What are some common serovars of Salmonella enterica?

enteridis, typhimurium, heidelberg, newport, hadar, agona, montevideo, oranienburg, muenchen, thrompson

What are the symptoms of salmonellosis?

diarrhea, fever, cramps, vomiting for 2-7d, onset 12-36h

How is Salmonella enterica transmitted?

fecal-oral via contaminated food, found in most species, especially reptiles/chickens

What is a type III secretion system?

>24 genes needle complex that transmits toxins into host cell

What are SPI?

Salmonella pathogenicity islands, cluster of genes for virulence factors

What is the role of SPI-1?

entry, needle formation, adherence, cytoskeleton rearrangement,

What is the role of SPI-2?

inhibit host defense by producing homocysteine/superoxide dismutase that inactivate toxic macrophage compounds, maturation/lysis of phagosome, intracellular bacterial replication, systemic infection

What are the genes in SPI-1?

invA, orgA, sipA, sipB, sipC, sopE

What are the genes in SPI-2?

spiC, ssaJ, sopB

What role does flagella play in Salmonella virulence?

middle is variable, switch from phase 1 to 2 helps avoid cell mediated immunity

What is the role of sipA SPI-1 effector protein?

binds actin, stabilizes filaments, allows actin polymerization, enhances Salmonella invasion

What is the role of sipC SPI-1 effector protein?

aids entry of others, G-actin to F-actin, aids cytoskeleton rearrangement/membrane ruffling

What is the role of sopB SPI-2 effector protein?

main virulence factor of Salmonella, enterotoxin increases Cl- and Na+ secretion into lumen, water follows ions out, causing diarrhea

What is membrane ruffling?

cytoskeleton proteins relocate to site of bacterial entry triggered by bacterial effector proteins, causing structural change/endocytosis

What is the role of TNF-a?

tumor necrosis factor alpha, induced by Salmonella flagella

How is Salmonella treated?

vaccinate chicks, human vaccine is heat denatured killed whole-cell bacteria

Describe the morphology of Escherichia coli

gram (-), motile, facultative aerobe, have fimbria/pili

What are some sources of Escherichia coli?

fecal flora of many animals, especially cattle, contaminated food

What are the virulence factors of Escherichia coli?

fimbriae/pili, hemolysins, siderophores, flagella, heat labile/stable toxins, LPS, capsules, K antigens, drug resistant plasmids

How are virotypes of Escherichia coli classified?

attachment pattern, effect of attachment, toxin production, invasion/translocation ability

What is localized adherence?

number of bacterial cells attached on a particular location of enterocyte surface

What is aggregative adherence?

distinct stacked brick pattern of bacteria cells

What is diffuse adherence?

bacteria uniformly cover entire cell surface

How does Escherichia coli invade?

type 3 secretion system

What are the major virotypes of Escherichia coli?

enterotoxigenic (ETEC), enteroinvasive (EIEC), enteropathogenic (EPEC), enterohemorrhagic (EHEC)

What are the heat labile toxins of ETEC?

similar to cholera, LT1 has human/animal origin, LT2 only in E. coli

What is the mechanism of heat labile toxins of ETEC?

one A subunit and five B subunits, internalized via endocytosis, increases intracellular cAMP, a membrane transport regulator, causing anion secretion/decrease NaCl absorption, causing diarrhea

What are the heat stable toxins of ETEC?

cysteine disulfide bonds for heat stability, STa methanol soluble, STb methanol insoluble

What is the mechanism of heat stable toxins of ETEC?

bind ST membrane receptor, activate GC-C, increasing cGMP, decreasing NaCl absorption, causing diarrhea

What are the colonization factor antigens of ETEC?

adhesins, 1 single protein subunit rigid rods, 2 at least two related adhesins, 3 bundle forming pilus, 4 multiple distinct fimbrial structures

How does EIEC infect cells?

plasmid mediated attachment, effector proteins secreted via type 3 system, endocytosis, vacuole lysis, infects adjacent cells

What is the mechanism of infection for EPEC?

a/e process by attachment with bundle forming pilus, microvilli disappear, protein injection that increases intracellular Ca, pedestal formation by actin accumulation

What are the effects of EPEC infection?

stx causes hemolytic uremic syndrome/kidney toxicity, diarrhea caused by loss of absorptive ability due to pedestal

What are the effects of stx from EHEC?

similar to EPEC, hemolytic uremic syndrome/kidney toxicity, 1 a subunit and 5 b subunits, a subunit inhibits protein synthesis and causes cell death

What are the major virulence factors of EHEC?

outer membrane proteins/ fimbriae adhesins, shiga toxins, hemolysin, LPS

How is EHEC treated?

no antibiotics because it would release all toxins at once, killing host, and kill other intestinal bacteria, increasing host absorption of toxin, no available vaccine

Describe the morphology of Listeria

gram (+), rods, motile, facultative anaerobe, no spores/capsule, beta hemolytic, favors cold, pH, and moisture ranges

What are some common species of Listeria?

monocytogenes, innocua, seeligeri, ivanovii, welshimeri, grayi

What are the serotypes of Listeria?

important ones 1/2a, 1/2b, 4b, division 1: 1/2b, 3b, 4b, 4d, 4e, division 2: 1/2a, 1/2c, 3a, 3c

How is Listeria transmitted?

establishes strains in food processing facilities, high risk in pregnancy/fetus, elderly, organ transplants, AIDS, cancer, cattle mastitis

How does Listeria monocytogenes infect cells?

InlA gene binds to E-cadherin, triggers actin cytoskeleton rearrangements to form tail that pushes them, phospholipases lyse phagosome,

How are Listeria monocytogenes biofilms formed?

extracellular polymericsubstance (EPS) matrix resistant to antibiotics, dependent on carbon availablity

What is the progression of perinatal infections of Listeria monocytogenes?

onset 4d-5w, spread throughout body via blood/phagocytes, cross placental barrier, 20-50% fatality

Describe the morphology of Shigella

gram (-), rods, facultative anaerobe,

What are the 4 species of Shigella?

dysenteriae, flexneri, boydii, sonnei

How is Shigella transmitted?

fecal-oral, only in human gut, food, fingers, feces, flies fomites, 100-200 will cause disease

What are the 2 stages of shigellosis?

early stage watery diarrhea due to stx, noninvasive colonization, fever due to neurotoxin, second stage adherence, invasion, more severe stx

What is the mechanism of infection of Shigella?

attachment via membrane ruffling, taken up via endocytosis with IpaD invasion plasmid, invade, survive host due to O antigen

Describe the morphology of Yersinia

gram (-), rods

What are the species of Yersinia?

enterocolitica, pseudotuberculosis, pestis

What are the major virulence genes of Yersinia?

Ail attachment-invasion locus, YadA binds integrins, fibronectin, collagen, laminin of host cells, Invasin binds integrins to help invade

What is the mechanism of infection of Yersinia?

invasin binds integrins, cell spreading over surface, actin polymerization, engulfment, later arthritis via HLA-B27 antigen

What are the effects of Yersiniosis?

onset24-48h, only enterocolitica/pseudotuberculosis cause gastroenteritis, sometimes followed by Reither’s syndrome arthritis