Week 6 Flashcards

Question

Describe mucosal B-lymphocytes in GALT

Answer 1

1. B cells are activated by cytokines from Th lymphocytes 2. Differentiate into plasma cells 3. IgM secreted first (but very large & vulnerable to intestinal enzymes) 4. Cytokines stimulate plasma cells to class switch their antibody isotype from IgM to secretory IgA (protected from enzymatic digestion)

Answer 2

IgA1 - predominant IgA subclass found in serum IgA2 - predominant IgA subclass found in secretory lymphoid tissues e.g., GALT - Secretory component is added to IgA antibody in lamina propria as it passes through mucosal epithelial cells - --> protected from enzymatic digestion

Answer 3

Secretory IgA captures antigens in lumen: 1. IgA binds to receptor on basolateral aspect of epithelial cell 2. IgA-receptor complex is internalised into epithelial cell 3. IgA-receptor complex is translocated to apical aspect where secretory component is wrapped around IgA molecule 4. On mucosal surface of cells secretory IgA is either released into lumen or captures antigen directly 5. Secretory IgA interferes with binding of pathogen to receptors on the epithelial cells to prevent pathogen invasion - --> Immune exclusion rather than immune elimination

Answer 4

Mucosal immunity also stimulates IgG production in circulation which can go into lumen but… Mostly in serum & lamina propria Neutralises bacterial toxins - limit toxic effects Opsonises invading pathogens, enhancing their phagocytosis or complement mediated lysis - reduce numbers or eliminate pathogen - --> Immune elimination

Answer 5

Salmonella Listeria Yersinia Some E. coli Rotavirus Cryptosporidium

Answer 6

when an animals immune response reacts to normally innocuous environmental antigens

Answer 7

phase 1: - sensitisation phase (no clinical signs yet) 1. allergen exposure via respiratory or skin 2. antigen presenting cells capture antigens 3. causes naive T cells to differentiate 4. release cytokines causing B cell proliferation 5. class switch for B cells from IgM to IgE 6. IgE binds to mast cells phase 2: 1. same allergen encountered 2. primed IgE coated mast cells bind to antigen of allergen 3. release of cytoplasmic granules 4. immediate hypersensitivity - pruritis, broncho-constriction, oedema

Answer 8

type 1 hypersensitivity

Answer 9

1. mediated by IgG antibodies that recognise antigens on cell surface - intrinsic or extrinsic antigens 2. activates classical complement pathway 3. destruction of cells (phagocytosis)

Answer 10

Can occur if there is no return to steady state conditions following acute inflammation Often infectious cause, may be immune mediated - e.g. chronic colitis/inflammatory bowel disease in dogs - --> Constant immune output occurs Granuloma may form --> e.g. enteric granuloma seen commonly in ruminant Johne’s disease (paratuberculosis) Granuloma may take long time to develop & is e.g. of delayed type hypersensitivity (Type IV) response

Answer 11

Autoimmune disorders - e.g. diabetes, rheumatoid arthritis, IBD Exposure to toxins - e.g. pollution, exposure to chemicals Chronic exposure to irritant or foreign material - e.g. foreign body granuloma Auto-Inflammatory (Hyper-Inflammatory) Syndromes - Hyper-inflammatory Syndrome in Weimaraner Infection - e.g. bacteria: * e.g. gingivitis, Johne’s disease Trauma - e.g. injury

Answer 12

1. Macrophages (Histiocytes – macrophages in tissues) fail to clear foreign agent & become chronically infected 2. Activated macrophages constantly secrete TNF-α & other proinflammatory cytokines which promote influx of T-cells - Removing TNF-α causes breakdown of granuloma 3. T cells around periphery secrete IFN-γ 4. Stimulated macrophages can further mature into epithelioid cells 5. Epithelioid cells sustain granuloma 6. Prolonged stimulation leads epithelioid cells to fuse together & form multinucleated ‘Giant Cells’ or Langhans cells 7. Giant cells are capable of phagocytosis & cytokine secretion 8. T-cell & macrophages stimulate fibroblasts promoting fibrosis which can lead to organ damage

Answer 13

pros: 1. Granuloma form focal killing point in which micro-organisms may eventually be killed 2. Granuloma prevent dissemination since it ‘walls off’ micro-organisms cons: 1. Break-down of granuloma can have serious effects since bacteria can disseminate 2. Granuloma may cause severe tissue necrosis & hence affect organ function 3. Granuloma can cause fibrosis & tissue thickening impairing organ function

Answer 14

Chronic Diarrhoea (>14 days) Causes: - Idiopathic - Chronic infection - Allergic response (e.g. food) * --> thus, immunosuppressive therapy may be effective - May be a genetic component Although granuloma may not be present, cytokines & immune cell infiltrate & maintain chronic inflammatory state Chronic enteropathy is most common gastrointestinal disorder in older cats, with rising prevalence over past decade Classified into 4 forms

Answer 15

Most common form of chronic enterocolitis in dogs & cats (commonly middle aged) Characterised by increased lymphocyte & plasma cell infiltrate into lamina propria (Ileum & colon common) In cats it may be difficult to differentiate from small cell lymphoma

Answer 16

Less common that lymphocytic plasmocytic enteritis No. of different breeds- usually younger animals Infiltrate is predominantly eosinophils Chronic parasitic infections/allergy e.g. food.

Answer 17

Neutrophil infiltrate Possible causes: - Idiopathic - Response to normal bacterial microbiota - Invasion of Campylobacter spp - Trichomonas foetus infection

Answer 18

A variant of eosinophilic enteritis Overproduction of eosinophils in bone marrow Widely disseminated eosinophilic infiltration of multiple organs Organs commonly affected include: - Bone marrow - Small intestine - Liver - Spleen - mesenteric & peripheral lymph nodes - Skin lesions Poor prognosis

Answer 19

Rare - Seen in young Boxer dogs, French bulldogs Thickened, partially obstructed segment of bowel (ileum & colon most commonly) Large foamy, Periodic acid-Schiff (PAS) +ve macrophages present in colonic mucosa (pro-inflammatory macrophage type) True granulomas are not present. Caused by E. coli

Answer 20

Lymphocytes leave LN, enter blood, then emigrate back from capillaries to intestine Addressins (adhesion molecules) on high endothelial venules interact with homing receptors on lymphocytes to ensure they reach mucosal surface

Answer 21

Bacterial DNA CpG dinucleotides are un-methylated Most mammalian CpG di-nucleotides are methylated TLR-9 in mammals recognises un-methylated CpG in bacterial DNA & initiates inflammation

Answer 22

Typically circular DsDNA Separate from the chromosomal DNA Some have a suicide gene to ensure maintenance Some are transmissible by conjugation Variable in sizes

Answer 23

Binary fission They have a generation time - Length of time required for single bacterial cell to divide to 2 daughter cells Binary fission leads to clones of bacteria

Answer 24

Mutation of genes Transfer of genes Rearrange their DNA Delete genes New genes inserted

Answer 25

Introduction of new DNA into and between bacteria: - Transformation - Conjugation - Transduction - Recombination Movement of DNA already in bacteria: - Transposition - Recombination

Answer 26

Transformation is the uptake of naked DNA DNA contacts the bacteria and is taken up Some bacteria are… - Naturally competent. They can take up DNA without treatment. Have competence mechanisms - Require treatment to become competent (laboratory competent) Once naked DNA is taken up into cells there are two options: - It is degraded by nucleases - It recombines into the genome

Answer 27

Bacterial conjugation is transfer of genetic material between bacteria through direct cell-to-cell contact (horizontal gene transfer) It's transfer of genetic information from a donor cell to a recipient donor must host conjugative or mobilisable genetic element (plasmid or transposon) Most conjugative plasmids have systems ensuring that recipient cell doesn't already contain similar element

Answer 28

Viruses that infect bacteria are known as bacteriophage Each virus is specific for a specific species of bacteria They need to bind (specific receptor) Then inject their genome and this infects the bacteria

Answer 29

Lytic and generalised transduction Temperate phage and specialised transduction

Answer 30

Process by which any bacterial DNA may be transferred to another bacterium via a bacteriophage

Answer 31

Lysogenic (viruses that insert their DNA into bacterial chromosome) Bacterial genes that get transferred depend on where phage genome is inserted on chromosome When prophage excises it may do this imprecisely or package adjacent bacterial DNA These packaged particles can then infect another bacteria with bacterial DNA

Answer 32

Degraded – non specific (no recombination general nucleases degrade DNA) Degraded – by specific restriction endonucleases (DNA restriction) It manages to integrates with genome (DNA recombination)

Answer 33

Homologous recombination - Where 2 DNA sequences are same they can intercalate their strands. During replication these can get spliced Non homologous – less efficient, DNA doesn't match but can be in random positions Directed - Insertion elements have repeats which lead to homologous/directed insertions in specific sites or enzymes that direct integration at set sites - These have hot spots for insertions & are more effective

Answer 34

It's not good for bacteria to constantly take up DNA so they have restriction system They have Restriction endonuclease(s) Which degrade DNA not made in their own cell These restriction nucleases don't degrade self-DNA as they act on specific sites Bacteria methylates its own DNA where its own restriction nuclease cut so blocking enzyme (They don't chew up their own genome) Works on any DNA including non-self plasmids

Answer 35

Either addition or loss of single base moving reading frame in an out of position Frame shift adds or removes base to change codon position relative to reading frame

Answer 36

Transposons are sequences of DNA that can move around to different positions within genome Transposons encode their own transposases Transposase cut out & re-insert the DNA flanked by inverted repeats (IR) The process directed by these enzymes is transposition They pop into (integrate) and out of DNA If they insert into a gene they will disrupt it

Answer 37

IS elements are a type of transposon. They are…. - short DNA sequence that acts as simple transposable element - are small relative to other transposable elements - only code for proteins implicated in the transposition activity - are different from transposons, which carry accessory genes

Answer 38

If a mutations is beneficial to bacteria this will become more fit Alteration of antibiotic binding sites - E.g. mutations ribosomal binding sites can reduce binding of ribosome targeting drugs Avoidance of vaccines - If mutations alters amino acid sequence of epitope that antibodies bind to then this can reduce or abrogate binding Alteration of metabolism - Can be no. of reasons mutations in promotors can upregulate or down regulate critical functions. Making bacteria less or more competitive

Answer 39

Changes of over time by mutations of genomes

Answer 40

substances added to the feed or water of animals to promote growth and improve feed efficiency Prolonged and large scale use will select for antibiotic resistance Leading to a reservoir of transferable antibiotic resistance Banned in UK and EU

Answer 41

Gut flora bacteria can transform (alter) compounds. This can have different effects - Drugs activated - Drugs inactivated - Toxic metabolites (and carcinogens) Different compounds in food can also alter composition of gut flora - Can lead to increased bacteria associated either with ‘improved’ or ‘reduced’ gut health

Answer 42

Qualitative - General assessment of level low, med, high Quantitative - Enumeration normally vs. volume or weight Visual examination - microscopy total count or general assessment Culture: - Viable counts where you dilute count colonies & calculate original no. of bacteria Molecular detection - Detecting species by quantitation of their nucleic acid

Answer 43

Slides/smears - May work for some very characteristic spirochetes but rods & cocci can't be distinguished in faeces - Useful in discrete normally body sites/tissues where you would expect sterility or only single common morphologies (you can spot abnormal types or mixed infections) Culture: - For faeces, the most common method is culture.

Answer 44

Age Stress Use of drugs Genetics Diet Illness

Answer 45

Surface structures, for adhesion and stop wash out LPS and membrane integrity for tolerance of harmful factors Motility to get to target niches General gene regulation for stress responses to turn on genes required to adapt to GI-environment Specific transporters to take up GI-specific nutrients

Answer 46

“Natural” competitive exclusion: Existing bacterial flora present competitive barrier to incoming bacteria so can exclude & prevent colonisation &/or infection Competitive exclusion products: Deliberate use of desired microbial cultures to colonise animals that out-compete pathogens from colonising specific niches (so can exclude & prevent colonisation &/or infection) - Applied commercially

Answer 47

Presence of one bacteria inhibits other due to it competing & winning in acquisition of growth factors ‘Nutrition’ is NOT free There is Competition (for….) - Space - co factors elements etc.. - Electron acceptors (Humans Oxygen) - Carbon sources Only compete if they require same type of nutrition

Answer 48

Antimicrobials can remove sensitive organisms from a particular niche Space left is then repopulated by intrinsically resistant bacteria Thus antibiotics can disrupt existing flora or allow over growth of undesirable organisms

Answer 49

also known feline infectious enteritis (FIE) or feline panleukopenia faecal-oral transmission infects lymph nodes of naso- & oro-pharynx & then spreads to other tissues - needs rapidly dividing cells to propagate then infects intestinal cells & bone marrow kittens most susceptible

Answer 50

enteric & respiratory pathogens commonly mutate

Answer 51

wet FIP - effusions dry FIP - pyogranulomatous lesions

Answer 52

Causes: - diarrhoea - decreased fertility/milk yield - abortion/congenital defects - immunosuppression - mucosal disease 2 genotypes: - BVDV 1 - classical form of disease - BVDV 2 - haemorrhagic syndrome (severe acute BVD)

Answer 53

BVDV can cross placenta infection during pregnancy may have various effects on foetus - if infected before development of foetal immunocompetance calf aborted or PI calf - if infected after calf aborted or born with congenital defects mucosal disease only develops in PI (infected in utero) animals around 2 years of age - invariably fatal

Answer 54

cattle plague highly infectious respiratory & alimentary tract disease high mortality clinical signs: - nasal discharge - pyrexia - oral & nasal erosions & ulcerations - diarrhoea with mucus, blood & debris - dehydration

Answer 55

young dogs transmitted by direct contact replicates in urinary tract spreads to tonsils & lymph nodes & then CNS clinical signs: - pyrexia - depression - ocular & nnasal discharge - vomiting - diarrhoea - hyperkeratosis of nose/pads - neurological signs if poor immune response

Answer 56

1. egg inoculation 2. harvesting allantoic fluid after 7 days 3. Haemagglutination test to detect viruses in allantoic fluid

Answer 57

acid-fast staining

Answer 58

slow (2-16 weeks) takes very long to culture so disease can spread while waiting

Answer 59

1. MAP colonises in intestinal epithelial cells by attaching to surface receptors 2. body forms granulomas to attempt to contain infection 3. causes disruption of normal digestive functions & leads to malabsorption 4. intestinal mucosa becomes damaged which leads to diarrhoea 5. contributes to weight loss

Answer 60

Relatively uncommon due to rapid passage of material through oesophagus & tough stratified epithelium Some viral infections can cause ulcers Most notable infections: - BVDV (Bovine viral Diarrhoea virus) & mucosal disease (Ovine Herpes virus 2) - Newcastle disease in poultry

Answer 61

Liver & spleen, GI Tract is a route for infection 1. Portal vein 2. Hepatic artery (billiary system) 3. Contagious spread from adjacent system

Answer 62

Zoonotic Associated with diarrhoea in dogs Gram negative Flagellated and Motile Microaerophilic Optimum growth temperature for C. jejuni is 42ºC. Grown on nutrient media or isolation using Campylobacter selective medium Can be seen as commensals in intestinal tract of warm-blooded animals The genera contains a number of species - C. jejuni, C. coli, C. lari Important because it is a common contaminant of meat

Answer 63

Samples depending on stage of production On farm: - Environmental samples - Faecal swabs - Boot swabs At abattoir: - Gut contents - Neck Swabs from birds - Skin samples At retail: - Swabs - Juice from meat packages - Whole meat samples

Answer 64

MLST looks at single base pair changes Done by sequencing 7 housekeeping (essential) genes & clustering strains based on differences These clusters are called clades Researchers have collected lots of strains from different sources & compared their MLS So if clinical isolate clusters in MLST clade it indicates potential source of infection MSLT systems exists for range of bacteria They get developed where there is clinical need to understand sources of infection

Answer 65

Mainly infects lower intestinal tract There is an inflammatory response during initial colonisation A correlation with Campylobacter colonisation and - reduced weight gain - Hock burn (which is associated with wet bedding i..e more watery faeces)

Answer 66

Diarrhoeas in dogs & other domesticated animals has been associated with Campylobacter However, Campylobacter is often found in healthy animals so what does this mean? Presence of large number of Campylobacter may indicate infection In older dogs evidence is unclear for campylobacter causing diarrhoea but there is some evidence in puppies It may be that disease is associated more with young or debilitated animals which are often increased at risk

Answer 67

Selective media - Blood agar plus selective antibiotics Stained faecal smear for spirochaetes Silver stain faecal smear PCR tests

Answer 68

Curved Gram-negative rod Obligate intracellular pathogen Microaerophilic In piglets & foals Diagnosis: - Clinical signs - Demonstration in mucosa or faeces by immunofluorescence or PCR - Staining of tissue sections - Serological tests

Answer 69

Invades enterocytes Causes lack of differentiation Undeveloped cells do not shed Leads to pseudo-stratified epithelium - Thickening of gut & thus poor absorption

Answer 70

Gram negative rods which are oxidase negative, facultative anaerobes & grow on MacConkey Major enteric pathogens - Escherichia coli (also commensal) - Salmonella enterica - Yersinia species Opportunistic pathogens

Answer 71

Differentiation by growth characteristics and biochemistry - Motility Test - Citrate utilization Test - Indole Test - Methyl Red (MR) Test - Voges–Proskauer (VP) Test - Triple Sugar Iron (TSI) Agar Test - Urease Test More common now for molecular tests to confirm species by: - PCR of unique genes - Whole genome sequence (WGS) - Ribosomal genome sequence - Mass Spectrophotomerty

Answer 72

Most members of this genus are low virulence They may cause opportunistic infections Pathogenic strains possess virulence factors which allow them to cause disease Basic genomes of E. coli are same but they will have gained some very specific properties. 3 main criteria - Adhesion factors *Presence or absence of LEE island - Type of enterotoxin present - Species associated with

Answer 73

Poor colostrum immunity ETEC receptors present Build-up of pathogenic E. coli Stress and environment

Answer 74

S. bongori S. enterica

Answer 75

Organisms found in: - Contaminated water sources - Carrier animals - Faecal contaminated environment Foodborne - Eggs (from infected birds) GI content contaminated food: - Raw Meat - Offal - Animal Feed - Plant material (Faecal contamination and uptake)

Answer 76

Profuse foul-smelling diarrhoea Fever Depression Anorexia Severely affected animals may become recumbent

Answer 77

1. TTSS-1 injects effector proteins into host enterocyte 2. Triggers actin changes that leads to engulfment of bacteria into vacuole 3. There are multiple TTSS-1 effectors but overall effect of different effector proteins is to - Trigger invasion by actin and tubulin remodelling - Trigger cytokine response - trigger Enteropathogenic response (fluid secretion) 4. Once bacteria is internalised in vacuole, host will try & attack bacteria moving antimicrobial vacuoles to form phagolysozome out of Salmonella containing vacuole. 5. These fusion is inhibited by TTSS-2

Answer 78

1. TTSS-2 injects SPI-2 effectors 2. These jam up in cytoskeletal movements in cell so cell can't mature vacuoles 3. This means Salmonella is in protected space 4. Salmonella replicates in controlled vacuole 5. In this space it's safe from adaptive responses as antibodies only survey outside cells

Answer 79

Common to specific host serotype combinations Host may vary in susceptibility with age Sudden high fever, depression, recumbence, rapid death Mucosa is route to deeper tissues Salmonella can spread in blood & lymph inside macrophages Organisms can spread to other organs liver & spleen (oviduct in birds)

Answer 80

Carrier state observed after recovery from enteric infection of - S. Enteritidis - S. Gallinarum Bacteria found in macrophages These reach oviducts and contaminate eggs Biosecurity & vaccination have reduced infection & egg contamination FSA guidance is that Lion Brand Eggs (or equivalent) in UK are now considered Salmonella ‘free’

Answer 81

The ‘majority’ Gram positive Found in various environments The group includes commensals and pathogens BUT exceptions - Mycoplasmas lack cell walls (e.g. of genetic reduction) Some Gram positive genera: - Produce endospores - Have porous pseudo-outer-membrane that causes them to stain Gram-negative

Answer 82

Gram negative Wide distribution in the environment, (soil, water GI tracts) Rarely pathogenic examples: - Bacteroides (abundant in the faeces) - Porphyromonas, (oral cavity)

Answer 83

All Gram Negative A major Phylum (with subgroups) - Alphaproteobacteria - Betaproteobacteria - Gammaproteobacteria - Deltaproteobacteria - Epsilonproteobacteria Includes commensals and pathogens Members can be facultative/obligate anaerobes or even microaerophilic Notable Genera clinically relevant to GI tract: - Escherichia, Salmonella, Vibrio (in humans), Helicobacter, Campylobacter

Answer 84

Pseudomonas found in lots of environments & can cause ear infections, burn infections, wool/skin in sheep infections It's good at forming biofilms in infections as it often produces exopolysaccharides (slime made form sugars) These films can make it more intransigent to treatment

Answer 85

Both are microaerophilic Helicobacter is important in stomach infections Campylobacter causes GI infection in humans & is foodborne zoonotic as its carried by number of large animals

Answer 86

Gram Positive, Anaerobes Can be branched Common commensal bacterium Niche gastrointestinal tract of mammals A major constituents of probiotic food supplements

Answer 87

A major component of mammalian gastrointestinal flora Gram negative, bacilli (morphology as in rod), anaerobes Non-endospore-forming Variable motility between species Will use simple sugars when available, but main source of energy is polysaccharides from plant sources

Answer 88

Gram Positive Facultative anaerobic / microaerophilic bacteria Major part of group can convert lactose & other sugars to lactic acid Common and benign Present on mucosa of reproductive and GI tract Production of lactic acid makes its environment acidic which inhibits growth of some harmful bacteria This ‘MAY’ help protect the gut against less pH tolerant bacteria

Answer 89

Gram Positive, Coccoid, facultative-anaerobes Members of phylum Firmicutes Cellular division on a single axis so they grow in chains or pairs Found in many body sites as commensals Can cause opportunistic disease

Answer 90

Gram Positive, Facultative anaerobe Commensal bacterium Niche gastrointestinal tracts mammals A major constituents of some probiotic food supplements Can cause opportunistic infections One of the ESKAPE pathogens

Answer 91

6 nosocomial pathogens that exhibit multidrug resistance & virulence Enterococcus faecium, Staphylococcus aureus, Enterobacter Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa & spp.

Answer 92

Gram Positive, Endospore forming, Rod shape, obligate anaerobes

Answer 93

Genetic material of animals, plants & bacteria consists of DNA Genome includes both genes (coding regions) & noncoding DNA In viruses genome can be double stranded or single stranded RNA or DNA

Answer 94

In animals mitochondrial genome is typically single circular chromosome that is approx. 16-kb long & has 37 genes Not all proteins necessary for mitochondrial function are encoded by mitochondrial genome Mitochondria divide by binary fission similar to bacterial cell division Mitochondria & thus mitochondrial DNA, usually comes from egg only Sperm's mitochondria enter egg but don't contribute genetic information to embryo – Maternal inheritance

Answer 95

Combined genetic material of microorganisms in particular environment – population level

Answer 96

study of structure & function of entire nucleotide sequences in bulk sample

Answer 97

Gut composed of widely divergent microbial lineages whose genomes contain functionally similar sets of genes that would give rise to coordinated single metabolic outcome Diversity & abundance level of microbes, genes, proteins & metabolites will influence energy balance, gut motility, inflammatory tone, mucosal integrity, appetite & signalling Gut key player (i.e., pathogens) may also negatively influence gut barrier - --> promoting inflammation Good flora can produce good products & also exclude detrimental bacteria Detrimental bacteria may produce toxins or interact with cells stimulating unwanted responses in gut mucosa

Answer 98

via cell structural components (ie LPS) & with release of microbial metabolites which act on intestinal epithelium, then released into bloodstream & cross blood-brain barrier production of pro-inflammatory cytokines by immune cells stimulate enteric nervous system & its sensory neurons or induce secretion of neuropeptides by entero-endocrine cells Affects: - anxiety-like behaviour - memory capacities - social behaviour - feeding behaviour

Answer 99

portion of gene's DNA or RNA that is composed of exons

Answer 100

Long interspersed nuclear elements (LINEs): - expressed as RNA & encode reverse transcriptase that creates DsDNA copy that can then insert Short interspersed nuclear element (SINE) sequences: - Widely distributed in eukaryotic genomes & have crucial roles in genome organization, genome evolution & modulating gene expression

Answer 101

pathogen detection quanitification of gene expression detection of gene mutations

Answer 102

not very developed immune system GI tract not fully developed Incomplete gut flora lack of exposure exploring environment with mouth

Answer 103

Viruses shed in diarrhoea can create aerosols foodstuffs, drinking water & fomites can be contaminated & spread disease poor disinfection of environment

Answer 104

objects or materials which are likely to carry infection

Answer 105

have their genetic material divided into separate segments (each encoding for different genes) allows for genetic diversity (each segment can undergo reassortment to create new viral variants) increases adaptability to survive in different conditions some have antigenic variation (encode for proteins that undergo frequent changes to avoid immune system)

Answer 106

1. reaction mix is heated to 95 degrees 2. hydrogen bonds of DNA nucleotides are broken down 3. double stranded DNA will be denatured 4. reaction mix is cooled down to annealing temperature 5. primers align with complementary sequence of target DNA 6. primers form hydrogen bonds with target DNA 7. reaction mix is heated to reach optimum temperature for DNA polymerase 8. heat stable DNA polymerase extends primers in 5'->3' direction 9. temperature raised to 95 degrees again to start next cycle

Answer 107

1. PCR detects pathogen DNA & immunodiagnostics detect Ab that animal produced when in contact with pathogen 2. snap tests immediate. PCR & ELISA 24-72h 3. PCR more accurate

Answer 108

nucleotide substitution that leads to change of an amino acid Impact can vary: - new amino acid might have similar properties to the old one or the substitution is in a part of the protein that does not affect its structure or function and has no impact - It can cause a major change in the protein

Answer 109

A point mutation that changes a codon for an amino acid into a stop codon and causes the premature termination of translation. If that happens close the 3' end of the strand than that might not have much impact on the proteins. Most non-sense mutations lead to non-functional proteins.

Answer 110

Increase in frequency, fluidity, volume & water content of faeces

Answer 111

Secretion of exotoxin Invasion of target cells leading to cell death Invasion of host cells & lymphatic's leading to systemic disease

Answer 112

A functional disturbance of the intestinal epithelial cells Increased out flow or decrease re-absorption of water crypt cells can pump chloride ions (Cl-) into the crypt space Cl- ions attract sodium ions (Na+) into crypt space, increasing local osmotic pressure As osmotic pressure increases, water is pulled into intestine Some enterotoxins can trigger & lock ON chloride secretion leading to hypersecretory diarrhoea Done by activating adenylate cyclase Example cause: - ETEC (enterotoxigenic E. coli)

Answer 113

Hypersecretion Villous atrophy Infiltrative and proliferative distortion of mucosa Mucosal necrosis

Answer 114

Destruction of the epithelial cells on villi or in the crypts Villi become often stunted or fused Example pathogens: - Attaching and effacing E. coli (EHEC, VTEC) - Rotavirus (mild villous atrophy) - Canine parvovirus (severe villous atrophy)

Answer 115

Recruitment of large numbers of Macrophage & T-lymphocytes in lamina propria & sub-mucosa Leading to crypt compression and villous distortion Therefore reduce absorptive capacity Example Paratuberculosis (Johne’s disease)

Answer 116

Infection leads to cell death Severity and extent depend on virulence of pathogen Majority of Diarrhoea from reduced absorption Example pathogens: - Brachyspira hyodysenteriae

Week 6 Flashcards

(206 cards)