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Microbiology 2 Flashcards

1
Q

Describe Caliciviridae

A
  • Non-enveloped
  • Icosahedral symmetry
  • 180 identical protein molecules arranged in dimers forming 90 arch like structural units, form 32 cup shaped surface depressions
  • Single molecule of linear +ve ssRNA
  • 5’ end capped by covalently bound Vpg and 3’ end is poly adenylated
  • Cytoplasmic replication
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2
Q

Describe the vesicular exanthema of swine virus

A
  • Now extinct disease
  • Virus present in marine mammals, act as reservoirs
  • Acute disease characterised by vesicles in oral cavity, interdigital space and coronary bands
  • Indistinguishable from other vesicular diseases
  • Laboratory diagnosis - virus isolation, direct EM or PCR
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3
Q

Describe the causative pathogen of feline calicivirus

A
  • Vesicirus of Caliciviridae family
  • +ve RNA
  • Small
  • Non-enveloped
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4
Q

Describe the epidemiology of feline calicivirus

A
  • Acute or sub-acute disease
  • Incubation period 2-3 days
  • Recover in 7-10 days when not complicated by secondary bacterial infections
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5
Q

Describe the clinical signs of feline calicivirus

A
  • Conjunctivitis
  • Rhinitis
  • Tracheitis
  • Pneumonia
  • Vesiculation of oral epithelium
  • Fever
  • Lethargy
  • Anorexia
  • Stiff gait
  • Rarely may get virulent systemic FCV: alopecia, cutaenous ulcers, subcutaenous oedema, high mortality
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6
Q

Describe the diagnosis of feline calicivirus

A

Virus isolation

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7
Q

Describe the causative agent of feline herpesvirus

A
  • Herpesviridae
  • Alphaherpesvirinae subfamily
  • Feline herpes virus 1 (genus)
  • dsDNA
  • Large
  • Enveloped
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8
Q

Describe the clinical signs of feline herpesvirus

A
  • Sneezing
  • Nasal discharge
  • Dehydration
  • Anorexia
  • Pyrexia
  • Ocular signs (chemosis, keratoconjunctivitis, corneal ulceration)
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9
Q

Describe the diagnosis of feline herpesvirus

A
  • Virus isolation

- PCR

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10
Q

Describe the treatment of FHV and FCV

A
  • Supportive and symptomatic
  • Fluid therapy
  • Broad spectrum antibiotics (prevent secondary bacterial infections)
  • Tends to be self regulating disease, supportive treatment more than anything
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11
Q

How can FCV adn FHV be controlled?

A
  • Inactivated and attenuated vaccines

- Quaratine for hospitalised cases

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12
Q

What are the 2 main causes of vesicular disease in cats?

A
  • Feline calicivirus

- Feline herpesvirus

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13
Q

Describe feline rhinotracheitis

A
  • Caused by feline herpes virus 1
  • Sudden onset of sneezing, coughing, profuse nasal and ocular discharges, corneal ulcers
  • acute disease similar to feline calicivirus infection
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14
Q

What are teh 6 genera of Piconaviridae and give the diseases they cause

A
  • Apthovirus (FMDV)
  • Enterocirus (SVDV)
  • Cardiovirus (encephalomyocarditis)
  • Rhinovirus (bovine rhinovirus 1-3)
  • Hepatocirus (human hepatitis A)
  • Parechovirus (human echovirus 22-23)
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15
Q

Give an example of an autoimmune disease of the oral cutaneous junction

A
  • Pepmphigus vulgaris
  • Usually dogs (rare)
  • Antibodies directed against intracellular layers above basal cell layer
  • Separation of epidermal cells
  • Chemicals may give similar lesions
  • Vesicles often burst before you can see them
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16
Q

What are the 4 bacterial forms

A
  • Bacillus form (Lactobacillus acidophilus)
  • Staphylococcus form (Staphylococcus aureus)
  • Streptococcus form (Streptococcus equi)
  • Spirulis (Leptospira, Campylobacter, H. pylori)
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17
Q

What are the different bacterial flagellal forms?

A
  • Monotrichous
  • Amphitrichous
  • Lophotrichous
  • Peritrichous
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18
Q

What is mean by monotrichous flaggella?

A

A single flagellum extending from one end of the cell

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19
Q

What is meant by amphitrichous flagella?

A

One flagellum extending from either end of the cell

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20
Q

What is meant by lophotrichous flagella?

A

A tuft of flagella extending from one or both ends of the cell

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21
Q

What is meant by peritrichous flagella?

A

Multiple falgella randomly distributed over the entire bacterial cell

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22
Q

What are fimbriae?

A
  • Attachment pilus
  • Strand of peptides attached to a bacterium
  • Found on many Gram-ve and some Gram+ve bacteria
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23
Q

What are porins?

A
  • Allow diffusion through outer membrane

- Specific membrane proteins forming a pore to allow diffusion

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24
Q

What are endospores?

A
  • Highly resistant bodies produced by bacteria under specific conditions in order to survive
  • Contain high levels of small acid soluble proteins
  • Layered dehydrated structure
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25
Q

Describe the structure of the bacterial cell wall

A
  • Made up of peptidoglycans

- Peptidoglycans are polysaccharides cross-linked with polypeptides

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26
Q

How can the cell wall of bacteria be targeted?

A
  • Target hte peptidoglycans
  • Beta-lactan antibiotics e.g. penicillin
  • Lysosyme enzyme that cleaves disaccharides
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27
Q

Briefly outline the Gram stain process

A
  • Crystal violet solution applied to sample
  • Rinse
  • Iodine
  • Rinse
  • Alcohol
  • Safranin
  • Rinse gentrly
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28
Q

Breifly outline the Acid-Fast staining process

A
  • Ziel-Neelson carbolfuchsin added to slide, apply heat
  • Acid alcohol to decolourise
  • Wash with distilled water
  • Counter stain with methylene blue
  • Wash with distilled water
  • Acid fast bacteria retain red colour, non-acid fast go blue
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29
Q

Why do mycobacteria stain red with Acid fast staining?

A

Mycolic acids in cell wall retain the carbolfuchsin stain

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30
Q

What are the 4 main biochemical tests used to identify bacteria?

A
  • Catalase
  • Oxidase
  • Nagler
  • Urease
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31
Q

Describe the catalase test

A
  • Add hydrogen peroxide
  • If bubbles then is positive
  • Produce oxygen as catalase enzymes present to break down H2O2 into oxygen and water
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32
Q

Describe the oxidase test

A
  • Add solution to paper, if turns blue is positive
  • Detects presence of specific cytochrome-C-oxidases
  • These protect agains oxygen radical damage
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33
Q

What is the Nagler test used for?

A

To identify organisms that liberate phospholipases

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34
Q

Describe the urease test

A
  • Detects presence of urease enzyme
  • Urea to ammonia and carbon dioxide
  • Campylobacter like organisms
  • Positive is pink
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35
Q

What is an anaerobe?

A

An organism which requires oxygen for life

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36
Q

What is an aerobe?

A

An organism which does not require oxygen for life, and does not survive in oxygen environments

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37
Q

What is a facultative anaerobe?

A

Organisms which prefer non-oxygen environments but can survive in presence of oxygen

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38
Q

What are micraerophilic bacteria?

A

Need oxygen to ferment carry out respiration, but high concentrations of oxygen are toxic

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39
Q

What is meant by enriched media?

A

A medium that has had something added to it that is needed by an organism to grow e.g. blood

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40
Q

What is meant by selective media?

A

A medium that has had something added and so will restrict which bacteria are able to grow on the plate e.g. bile salts, deoxychlorate, selective antibiotics

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41
Q

What are indicator media?

A

Media that have an idicator included in it in orde to identify colonies of bacteria e.g. a substrae is added that leads to a pH change when utilised and in turn leads to a colour change.
Often combined with selective media as done in MacConkey

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42
Q

Describe MacConkey agar

A
  • Selective indicator
  • Restricts which bacteria are able to grow through use of bile salts
  • Lactose and neutral red pH indicator used to identify specific colonies
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43
Q

Outline the agglutination test

A
  • Serological test
  • Detects presence of serum agglutinins H and O
  • H antigen is thread like portion of flagella
  • O antigen is outermost portion of LPS on bacterial surface
  • Positive result is where agglutination occurs
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44
Q

What is the Baltimore classification system for viruses?

A

Classification of viruses based on characteristics of genetic information e.g. dsDNA vs dsRNA etc

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45
Q

What types of infection can you get from viruses?

A
  • Latent
  • Persistent
  • Lytic
  • Transformation
46
Q

What is a latent viral infection?

A
  • The virus is present but not causing harm to cell, may later emerge in lytic infection
  • E.g. Herpesvirus
47
Q

What is persistend viral infection?

A
  • Slow release of virus without cell death

- E.g. hepatitis

48
Q

What is a lytic viral infection?

A
  • Death of cell and release of virus

- e.g. FMD

49
Q

What is a transformation infection?

A
  • Transformation of normal cells to tumour cells

- E.g. Feline leukaemia virus, canine oral papilloma virus

50
Q

Describe the key stages in viral infection

A
  • Acquition into host (e.g. breathed in)
  • Attachment and entry
  • Initiation of infection at primary site
  • Incubation as virus amplified
  • Translation or immediate replication using host cell machinery
  • Assembly of new virus particles
  • Release from cell via cytolysis or budding
51
Q

What methods can be used to detect viruses?

A
  • Detection of viral proteins
  • Detection of virus genetic material
  • Serology
  • Live virus culture
  • Electron microscopy
52
Q

How can viruses spread in the body?

A
  • New virus made is released into body by cell
  • Can be enveloped
  • Taken up by other cells
53
Q

Why are soe infections localised and others more general?

A
  • Ability of virus to either infect only one cell types or more than one
  • Some cell types are found everywhere, others only in specific areas
  • Depends on surface proteins cells express as these are needed to viral attachment
54
Q

What features are used to identify filamentous fungi?

A
  • Made up of hyphae
  • Fuzzy appearance
  • Often have conidia at top that release spores
  • Multicellular
55
Q

What is a dimorphic fungus?

A

One that can grow as yeast or hyphal form depending on the environmental conditions (temperature)
- e.g. Cryptococcus neoformans

56
Q

Describe the main features of a yeast

A
  • Asexual division by budding
  • Can also reproduce sexually
  • Spores formed more like gametes
  • Round shape of cells
  • Form neat blobs rather than fuzzy shapes
57
Q

What is the importance of the gut flora?

A
  • Protects against establishment of pathogens
  • Important in physiological health of animal
  • Role in resistance to infection (exclusion and competition)
  • Role in nutrition (metabolism)
  • Role in bowel cancer
  • Role in immune development (primes immunity)
  • Role in evolution
58
Q

What is meant by competitive exlusion?

A
  • Competition for nutrition, electron acceptors and a carbon source
  • Nutrition is not as readily available
  • Is the use of desired microbial cultures that out-compete pathogens from colonising specific niches
59
Q

What are some of the nutritional benefits of gut flora?

A
  • Fore-gut fermentation in ruminants
  • Hind-gut fermentation e.g. horses
  • Vitamin production e,g in pigs Clostridium butyricum synthesises B12
60
Q

What samples can be used to study the gut flora?

A
  • Faecal
  • Post mortem (fresh/not fresh)
  • Samples during surgery
  • In vivo analysis
61
Q

What are some qualitative methods of gut flora study?

A
  • Direct examination
  • EM
  • Microscopy
62
Q

What is a disadvantage of using qualitative methods for gut flora study?

A

Most pathogens look the same so is only useful if have easily distinguishable pathogen

63
Q

What are the disadvantages of using quantitative methods for gut flora study?

A
  • Need to carry out in same conditions as where pathogen would be found
  • May be better to use medium selecting for suspected cause of disease rather than total count
64
Q

What are the quantitative methods of gut flora study?

A
  • Total bacterial count

- Viable count

65
Q

Describe total bacterial counts

A
  • Direct count
  • Dilute and count no of bacteria in faecal matter, live and dead, independent of growth requirements
  • Does not show what is present
  • Can carry out DNA analysis if want to know presence of specific organism
66
Q

Describe viable bacterial counts

A
  • Samples, can be variety
  • Homogenise with buffer
  • Supports pathogens, then dilute
  • Dilution series and plating
  • Use selective media to ensure desired bacteria present
  • Combine with indicator to detect presence of particular groups
  • Likely to have mixture of commensals otherwise
67
Q

How can the presence of bacteria be assessed?

A
  • Smear of sample with simple staining
  • Direct counting by microscope
  • Colony counting on selective media
68
Q

What factors affect adult floral composition?

A
  • Establishment
  • Floral differentiation
  • Disruption to flora
69
Q

Describe how establishment affects adult floral composition

A
  • Foetus microbiologically sterile
  • Host supplied receptors for adhesins and niches for specific organisms
  • Organisms have different receptors providing tissue specificity and different biochemisty allowing growth in specific niches
  • Acquires organisms from surface parts of birth canal and immediate environment
  • Immediate environment contaminated with organisms excreted from dam and other animals
  • Once ingested compete for gut (the niche)
70
Q

Describe how floral differentiation in the gut occurs

A
  • Between species (anatomy, cell biology, diet, physiology, mucous composition)
  • Within species (age, use of drugs, diet, stress, genetics, illness)
  • Change over time maternal immuntiy/bottle feeding/pre-ruminant, antibacterial effects, acquired immunity, weaning, old age, complexity increases over time)
71
Q

Describe how floral disruption affects the floral composition in the gut

A
  • Antimicrobials remove sensitive organisms from particular niche
  • Space that is left repopulated
  • Antibiotics can aid colonisation by undesirable organsisms adn pathogens
  • Remove competition by commensals, pathogens able to take over
72
Q

What are the host factors that affect colonisation as the first stage of disease?

A
  • pH
  • Peristalsis
  • Mucus and mucus integrity
  • Bacterial competition
  • Immune defence
  • Antimicrobial products
  • Host genetics and immune stimulation
73
Q

What are the bacterial factors that affect colonisation as the first stage of disease?

A
  • Surface structures for adhesion
  • Nutrient acquisition
  • Adaptation to pH, anaerobic conditions, temperature change
  • Temperature only important in heterotherms
  • LPS and membrane integrity for tolerance of harmful factors
  • Motility to get to target niches
  • Specific transporters to take up GI specific nutrients
  • Toxins
74
Q

What are the constituents of the normal flora of the oral cavity?

A
  • On buccal surface, tongue and teeth: Streptococci, Pasteurellaceae, Actinomyces, E coli, Neisseria spp, Simonsiella
  • In gingival crevice: Bacteroides, Fusobacterium, Peptostreptococcus, Porphyromonas, Preyotella
75
Q

What are the constituents of the normal flora of the oesophagus?

A
  • No define flora

- Contaminated by organisms similar to those in saliva

76
Q

Describe the normal flora of the stomach

A
  • Hostile to organisms
  • Some pathogens endemic in number of populations
  • Problems in neonates where environment not fully developed
77
Q

Describe the normal flora of the rumen

A
  • Complex structure of organisms

- Mostly obligate anaerobes

78
Q

Describe the normal flora of the alimentary canal

A
  • Bacteria (anaerobes, Enterobacteriaceae, Streptococci, Enterococci, Lactobacillus)
  • Protozoa
  • Fungi/yeasts
  • Spiral organisms
79
Q

Describe the normal flora of GI associated organs (liver, gall bladder, pancreas)

A
  • No normal flora
  • Some transient asymptomatic bacteraemia
  • Clostridia spores in liver only germinate if oxygen tension drops very low and allows for germination
80
Q

Describe DNA replication in prokaryotes

A
  • Circular DNA
  • Fast
  • Single origin of replication
  • 2 bidirectional replication forks
81
Q

Describe DNA replication in eukaryotes

A
  • Linear DNA
  • Slow
  • 100s of origins of replication
  • Requires DNA polymerase and other enzymes
  • Replication forks move in both directions
  • Occurs in synthesis (S) phase of cell cycle
  • Replication “bubbles”
82
Q

Describe the polymerase chain reaction

A
  • Rapid, simple method for copying and amplifying specific DNA sequences
  • Repetitive cycles of DNA melting, annealing and synthesis
  • Need to know sequence of short reigion of DNA on each end of larger sequence that needs to be copied and amplified
  • Used to design 2 synthetic DNA oligonucleotides
  • Each is complementary to sequence on one strand of DNA double helix at opposite ends of region to be amplified
  • Serve as primers for in vitro synthesis
  • Different length strands of DNA produced
83
Q

What is agarose gel electrophoresis used for?

A
  • To separate DNA or RNA molecules produced by PCR by size
  • Negatively charged nucleic acid molecules move through agarose matrix with electric field
  • Shorter move faster, migrate further than longer strands
  • Visualisation by adding fluorescent dye that intercalates into DNA strands
84
Q

Outline PCR use in diagnostics for infectious and non-infectious diseases

A
  • Detection of bacteria
  • Equine coronavirus
  • Cancer diagnosis
  • Feline panleukaemia virus
85
Q

What are plasmids?

A
  • Small self replicating circles of DNA
  • Range in copy number per cell
  • Partition genes so when bacteria divide both cells gain plasmid
  • Not all bacteria have plasmids
  • Can transfer between relateed bacteria carrying range of properties
86
Q

What is often contained within plasmids?

A
  • Transfer genes
  • Replicating genes (regulate and copy number)
  • Resistance genes
  • Virulence genes
87
Q

Describe structural arrangement of bacterial chromosomes

A
  • Haploid
  • Circular DNA
  • Longer than typical prokaryote
  • To fit in cell is organised into DNA-protein complex called nuleiod
  • Supercoiling DNA using DNA gyrase
  • DNA binding proteins (histones) used to further package
88
Q

What is contained within bacterial nucleoids?

A
  • Large amount of RNA polymerase
  • RNA
  • Many different regulatory proteins
  • Not structural role
  • Reflect main data transfer within cell
89
Q

Describe bacterial transposons

A
  • Used in transposition, can be self transmissible
  • Sequences of DNA that can move to different positions within genome
  • Intefrate into and replicate as part of genome
  • Insertion can disrupt the genes they insert into
  • Have accessory genes associate in them
  • Sometimes carry additional genes e.g. antibiotic resistance
  • Some transposon shown to transfer genes but most piggy back on other transfer systems
90
Q

What is transposition?

A

The movement of chunks of DNA within the chromosome

91
Q

What are insertion sequences?

A
  • Type of transposon
  • Known as IS elements
  • Short DNA sequence that acts as simple transposable element
  • Small relative to other transposable elements
  • Only code for proteins implicated in transposition activity
  • Different from transposons which carry accessory genes
92
Q

What are the processes involved in bacterial gene transfer?

A
  • Transformation
  • Conjugation
  • Transduction
93
Q

Describe transformation in bacterial gene transfer

A
  • Uptak eof naked DNA
  • DNA contacts bacteria, taken up
  • Some bacteria are naturally competent and can tak eup DNA without treatment, competence mechanisms
  • Others require treatment to become competent
94
Q

Describe conjugation in bacterial gene transfer

A
  • Transfer through cell to cell contact
  • Horizontal gene transfer (donor to recipient)
  • Donor must have conjugative or mobilisable genetic element (plasmid or transposon)
  • most conjugative plasmids have systems ensuring recipient cells does not already have similar element
  • Move whole blocksof properties
  • Most commonly antibiotic resistance, virulence factors
95
Q

Describe viral transduction in bacteria

A
  • Viruses infecting bacteria called bacteriophages
  • Each virus specific for specific species of bacteria
  • Need to bind to specific receptor
  • Then inject genome and infect bacteria
96
Q

How does the evolution of bacteria take place?

A
  • Rearranging DNA (transposition and recombination)
  • Deletion of genes
  • Insertion of new genes transformation, conjugation, transduction)
  • Mutation of genes already present
97
Q

Explain the role of bacteriophages in bacterial evolution

A
  • Viruses that infect bacteria
  • Different types of bacteriophage
  • Lytic or temperate
  • Lytic undergo lytic cycle in bacteria (infect, replicate, lyse)
  • Temperateintegrate in genome or act like plasmid, undergo lysis if triggered
  • If temperate integrate when reform virus can take host DNA, when next infect can trasnfer genes to new bacterium
98
Q

What are the possible outcomes of entrance of DNA into bacteria?

A
  • Degradation by non-specific nucleases (no recombination)
  • Degradation by specific restriction endonucleases (DNA restriction)
  • Integration with genome (DNA recombination)
99
Q

Outline genetic recombination in bacteria

A
  • Sequences of DNA from 2 seperate sources integrate
  • Can lead to inheritable changes in bacteria
  • May be host spots for recombination
  • Can have imperfect matches
  • May be homologous or non-homologous
100
Q

Define homologous genetic recombination

A

Aligment to similar sequences, crossover between aligned DNA strands

101
Q

Define non-homologous genetic recombination

A

Between DNA sequences that contain no sequence homology

102
Q

How is gene transfer restricted?

A
  • Restriction system to prevent constant uptake of DNA
  • Controlled by restriction endonucleases
  • Degrade DNA not made in own cell
  • Acts at specific sites
  • Bacteria methylates own DNA where own restriction nuclease would cut so do not destroy own genome
103
Q

What occurs in transcription?

A

DNA -> mRNA

104
Q

What occurs in translation?

A

mRNA -> protein

105
Q

What changes can occur to the DNA within bacteria?

A
  • Point mutation
  • Transposiion
  • Re-arrangement
  • Deletion
106
Q

What is point mutation in DNA?

A

Single base changes, can have dramatic effect or no effect

107
Q

What happens in rearrangement of bacterial DNA?

A
  • Inversions, reversals
  • CCross over and DNA strands interact
  • Copes, end up with jumbled strand or cut due to deletion
  • Cannot replicate from this
108
Q

What is deletion in DNA?

A

Removal of a sequences of bases

109
Q

Outline the methylation of DNA and CpG in post-translation events of bacteria and the effect on mammalian cells

A
  • Methylation patterns of DNA different between kingdoms
  • DNA from bacteria has stimulatory effect on mammalian immune cells
  • Depends on presence of unmethylated CpG dinucleotides in bacterial DNA
  • Mammalian DNA has low frequency of CpG
  • Mammalian CpG mostly methylated
  • Host immune responses stimulates as bacterial CpG DNA binds TLR9
  • Leads to strong Th1-like inflammatory response
  • CpG DNA therefore has potential as adjuvant
110
Q

What are CpG sites of DNA?

A

CpG sites are regions of DNA where cytosine nucleotide occurs next to guanine nucleotide

GI (31 decks)

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