Bacteria, Fungi, Viruses and Parasites Flashcards
What are the different types of bacteria morphology?
Coccus- circle shaped, single, pairs, chains, 4s, 8s or clusters
Bacillus- rod shaped, single, chains or pairs, curved, helical, club shaped or filamentus
Coccobacillus- elongated ball
Pleomorphic- multiple possible shapes
List the features of bacterial structure
Capsule Cell wall Plasma membrane Periplasmic membrane Inclusion bodies- nutrient store Ribosomes Mesosome- folding of membrane to keep proteins in place Neucleoid Flagellum Surface proteins Glycocalyx- capsules and slime layers Fimbrae- small extensions outside cell
What is meant by protoplast?
Plasma membrane, cytoplasm and all its contents
Describe how the gram positive cell wall works
Outside plasma membrane
Shrinks in dehydration to form full barrier around cell to conserve water
What is the structure of the gram positive cell wall
Peptidoglycan cross link proteins stabilised by lipoteichoic acid and teichoic acid
Describe where the gram negative cell wall is found
Surrounding plasma membrane is periplasmic space and then an outer membrane
What is the structure of the gram negative cell wall?
Liposaccharides present in bilayer
What is the structure of liposaccharides?
Lipid A linked into outer membrane connected to core chain and O specific side chain
What is the function of chromosomal DNA in bacteria and where is it found?
Codes all functions
In nuclear region, usually only one present
What are plasmids?
Extra chromosomal DNA
Usually auxiliary genes and carry antibiotic resistance
Define auxiliary genes
Modulate host cell metabolism during infection to make replication efficient
What are the types of plasmids?
Resistance Virulence- causes harm Colicin- toxic protein prodcuing Fertility- plasmid moves between bacteria Degradative
What is the effects of genetic variation?
Evolution
Affects virulence, resistance to hosts defences and resistance to treatments
What are the different methods of variation?
Affects resident genome- mutation, slowly happens and most lead to death
New DNA- recombination, rapid
When is variation retained by bacteria?
When it causes increase in survivability
What are the different nutritional requirements by different bacteria? Name an example for each and other important information
Simple- glucose, phosphate, sulphate, ammonium. e cColi. Tend to live in gut and make nutrients using lots of genes and pathways
Complex- growth factors, vitamins, nucleotides. Fastidious bacteria. Unable to make certain compounds due to less genes and pathways
Unknown needs- cant grow in lab, probable need lots of requirements from host. Parasites
Define fastidious
Microorganism that must live in host to survive
What is the oxygen requirement and energy production in obligate aerobes?
Lots of oxygen
Aerobic respiration
What is the oxygen requirement and energy production in microaerophiles?
Some oxygen as unable to remove toxic products of oxygen metabolism
Aerobic respiration
What are the oxygen requirements and energy production in facultative anaerobes?
Live with or without oxygen, lots of energy pathways
Aerobic respiration, anaerobic respiration and fermentation
What are the oxygen requirements and energy production in strict anaerobes?
Die in oxygen
Anaerobic respiration and fermentation
Define saprophytes
Free living bacteria
Define parasites
Organisms that live in or on animals
What are the two different sources of infections?
Exogenous- from environment or another host carrying commensals
Endogenous- from animals own commensals
Define symbiotic
Bacteria and host benefit from each other
Define commensal
Bacteria gain from host but cause no harm
Define pathogenic bacteria
Bacteria gain and cause harm, either obligate or facultative
What is meant by facultative bacteria?
Opportunistic
Normally harmless until host conditions change
What are opportunities for facultative bacteria to cause harm?
Entry into new body site
Change in body site, temperature, pH, commensal imbalance etc
Reduced defences
What are the requirements for bacterial growth?
Slightly alkaline pH
Optimum temperature varies
CO2 from body catabolism or environment
Nutrients
What are the products of oxygen metabolism and why do they need to be mopped up?
Hydrogen peroxide and superoxide radical
Destroy cell
What mops up the products of oxygen metabolism?
Hydrogen peroxide- catalase
Superoxide radical- superoxide dismutase
Why cant anaerobes survive in oxygen?
They dont produce catalase or superoxide dismutase
What are the mechanisms of nutrient uptake by bacteria?
Passive diffusion- very slow, ineffective unless in nutrient rich environment
Facilitated diffusion- moves through channels
Active transport- uses lots of energy, need constant respiration or fermentation
What different types of medium can be used to provide nutrition in a lab to bacteria?
Simple- agar
Enriched- non-specific, grow everything present
Selective- mimics ideal conditions and inhibits other bacteria
Differential- visually differentiates bacteria colonies
Blood agar- shows if haemolytic
MacConkeys bile lactose agar- mimics gut growing bacteria that grow in bile
Describe bacterial growth in a closed system
Lag to start as bacteria adapting enzymes and proteins to new conditions
Exponential growth
Growth stationary as lack of resources
Decreases in number as bacteria starve or poison to death
Define obligatory parasites
Spend whole life in host to be able to reproduce, intermittent or continuous feeders
Define facultative parasites
Spend part of life in host, can reproduce on or off host, intermittent feeders
What are the general symptoms parasites have on the host?
Blood loss Tissue damage Inflammation Itching Allergic responses Reduced weight gain Skin wounds Microbial infection
What animals is sarcoptic mange mainly found in and in which area of the body?
Dogs- pinnae, elbows and ventral abdomen
Pigs- ear canals and dorsal trunk
How does sarcoptic mange spread?
Zoonotic
Why is sarcoptic mange hard to find after infection?
Mites are hard to find
Can be asymptomatic for a long time
What are the symptoms of scabies/sarcoptes?
Intense itching
Infalmmation
Hair loss
Dry skin
Explain the life of scabies
Adult females burrow into upper skin layers and lay eggs
Eggs grow to adult in 17-21 days
Can survive 2-3 weeks off host but usually find new host after 2 days
Host dies after 2-4 months`
Define mange
Severe skin disease caused by ectoparasitic mites
List the life cycle of mites
Egg Larvae Protonymph Deutonymph Tritonymph Adult
How do mites increase their size?
Slough off exoskeleton
What disease is caused by trombicula autumalis?
Pruritic skin disease
Describe the life cycle of trombiculidae
Large yellow larvae are found on vegetation mid-late summer and autumn particularly on soft fruits
Larvae attach to host and feed on tissue fluid
Fall off and finish life cycle in environment
What are the symptoms of trombiculidae?
Hypersensitivity and severe pruritus
Where does cheyletiella live?
Skin surface usually on hairs in rabbits, cats and dogs
How long can cheyletiella live off the host?
10 days
What are the symptoms of cheyletiella?
Irritation
Highly contagious dermatitus
What hosts does otodectes cynotis live in and where are they found?
Cats
Dogs
Carnivores
Ear canal
How long to females otodectes cynotis live and how many eggs can they produce?
2-3 weeks
15-20 eggs
Where is demodicosis found and how can they be found?
Deep in skin in sebaceous glands and hair follicles
Deep skin scrapes, hair plucks or biopsy
What type of parasite is demodicosis?
Obligate parasite
How long do demodicosis live and how are they passed on?
18-24 days
Dam suckling from mum
What is meant by ticks questing?
Crawling up vegetation and waiting for host to come close to climb on
Describe the lifecycle of a tick
Adult female engorges Lays eggs after blood feed Larvae Nymph Adult
What makes ticks effective at holding onto their host?
Backward facing teeth
Why do ticks cause inflamation?
Saliva contains vasodilative prostaglandins
Describe the lifecycle of ixodes ricinus tick
Adults feed on cattle Fully fed adult drops Lays eggs which hatch in ground Larvae feed on rodents or birds Fully fed larvae drops to ground Moults to lymph Nymphs feed on small animals Fully fed nymph drops to ground Nymph moults to adults
Describe the lifecycle of fleas
Adult lays eggs 48 hours after mating and feed
Larvae hatches 1-10 days after laying
Move away from light to feed on organic debris
Pupa forms ater 5-11 days, spinning cocoon and staying deep in carpets for weeks-months
Adult usually emerges after 5-10 days to look for host and blood meal
Once on host must feed as gut changes and can only survive 3 days away from host
How long can unfed fleas survive?
10-60 days
What symptoms do fleas cause?
Pruritus/itching Alopecia Self wounding Hypersensitivity Anaemia
What adaptations do lice have?
3 pairs of legs- hold hair
Short pointed head- penetrating to feed
Flat head- chewing epidermis
Describe the life cycle of lice
Egg layed on hairs
Nymph
2 sheds and growth
Adult
What are the different types of lice?
Felicola subrostratus
Trichodectus canis
What makes animals more vulnerable for felicola subrostratus?
Elderly
Ill
Long haired breeds is harder to manage
Where is trichodectes canis found?
Base of hairs at head, neck and tail
What does a trichodectes canis infection cause and what animals is it most harmful to?
Itching Inflammation Alopecia Bacterial infection Intermediate host of tapeworm Puppies
What classifications of flies are there?
Dermal Subdermal Cutaneous Nasopharyngeal Ocular Intestinal Urogenital
Describe the lifecycle of gasterophilus spp. flies
Lay eggs on horses Get ingested and larvae swallowed Larvae reside in stomach Released in faeces Grow into adults in the environment
What are culicoides flies?
Small flies acting as vectors for alicoides hypersensitivity
What animals are common hosts for culicoides flies?
Horses
What is the vectors for canine leishmaniosis?
Sand flies
What is the life cycle of culicoides midges?
Egg
Aquatic larvae, stay as 4th stage larvae over winter
Pupa
Adult which can live 20 days in field
What are common rabbit parasties?
Blowfly strike
Myxomatosis
Mange mites
Coccidia
What causes rabbit strike?
Lucillia sericata when rabbits struggle to groom and cause skin damage that flies lay eggs in
What is strongyles and where is it found?
Large redowrm in horses gut
Describe the lifecycle of strongyles
Eggs layed in gut Leave in faeces Grow into larvae in environment Continue to grow as larvae when ingested by horse Mature in gut
How does strongyles cause disease?
Block blood vessels in gut causing colic
What are the common equine parasites?
Parascaris round worms Tapeworms Bot flies Midges Fly worry
What is anthelmintic resistance and what parasites have it?
Resistance to anthelmintic drugs from repeated infection and treatment
Widespread in redworm, parasacris and pinworms
What is cyathostomins and where are they found?
Small redworms
Horses gut
How does cyathostomins cause disease?
Larvae damage mucosa on emergence
What are the clinical signs of angiostrongylus?
Coughing Dyspnoea Anaemia Depression Anorexia Pneumonia Weightloss Pulmonary hypertension
Where is toxocara canis found?
Dogs and cats small intestines
Describe the lifecycle of toxicara canis
Lay eggs in faeces which are ingested
Grow and leave gut and enter liver and lungs
Describe the lifecycle of family taenidae
Adult tapeworms sit in gut and lay eggs in carnivores
Immature stage when eggs are ingested cause cysts in various organs of herbivores
What is the cell wall of fungi?
Chitin and complex carbohydrate polymers
What are the two main forms of fungi?
Mould
Yeast
Define dimorphic fungi
Produce both yeast and hyphae
Define and describe pseudomycelium
Intermediate form of growth between hypahe and yeast
Elongated budding cells from pseudohyphae
Define a colony of fungi
Mycelium or mass of yeast cells usually grown from a single cell
Define hyphae
Basic unit of moulds
Describe the structure of hyphae
Atypically elongating cylinder capable of branching
Cross walls at intervals to add strength but pores in to allow sharing of cytoplasm and nutrients
Acellular often having several nuclei per segment
Define mycelium
Network of hyphae forming body of mould
What are the two types of mycelium?
Submerged vegetative- burrowed into surface
Aerial- in air
How do moulds reproduce?
Release spores
Asexual
How do yeasts reproduce?
Budding
Where do yeasts live?
On surfaces
What is the structure of yeast cells?
Discrete ovoid cells
What are the phylums of fungi?
Zygomycota
Ascomycota
Basidomycota
Deuteromycota
What type of fungi fit into deuteromycota?
Fungi that dont fit into other phylum groups
Most pathogens
What are features of deuteromycota?
No sexual reproductive state, only produce conidia
How are fungal diseases diagnosed?
Skin scrapes
Culture and ID
Serology of antibodies
Molecular ID of fungal DNA by PCR
How are fungi introduced to the body?
Mycosis/infection
Inhaled
Toxicosis/ingesting
What are the two sources of fungal infection?
Endogenous- commensal flora, fungal overgrowth
Exogenous- fungus taken into body
What are the types of fungal infections?
Superficial- epidermis, nails, hair
Subcutaneous- traumatic inoculation through skin
Deep- inhaled, deep wound, endogenous
What are features of deep fungal infections?
Grow well at blood temperature
Not contagious as dont grow well enough to pass between individuals
Opportunistic
What are examples of yeast infections?
Candidosis- thrush
Cryptococcosis
Malassezia- cause dandruff
What are examples of mould infections?
Aspergillosis
Mucoromycosis
Mycotic abortion
What symptoms does cattle ringworm cause?
Loss of growth
Lower milk yield
Scarring (reduce value)
What treatment is used for cattle ringworm and why is it easy to treat?
Topical shampoos, washed or sprays
Decontaminate environment by burning, restricting movement and bleaching
Asexually reproduce so little variation
What is bovine mycotic abortion?
Non-contagious infection of placenta and foetus causing thickening of membranes and skin
What is candidosis?
Opportunistic infector found in normal gut flora
How is cryptococcosis spread and how does it cause disease?
Inhaled
Nasal granuloma, skin ulcers, mastitis
Opportunistic
What is the main source of aspergillosis?
Spores in hay and straw
How does aspergillosis cause disease?
Inhaled and travel to alveoli
Hyphae go into tissues
Acute in young as easily takes over airways, chronic in young animals
How were viruses first discovered?
Thought to be toxin, dilution didnt effect disease severity but less got infected overall
Foot and mouth disease was transmitted after bacterium had been removed
What does genome sequencing of viruses help understanding of?
Classification Replication Development of drugs Vaccines Evolution
How are viruses grown in labs?
In living tissues such as embryonic eggs or animal cells
How are viruses seen in labs?
Electron microscopes
Why cant viruses live outside host cells?
Rely on them for energy source, raw materials and machinery for replication
What are the structural components of viruses?
Genome Peplomers- virus derived proteins anchored in virus envelope Envelope- lipid bilayer Proteins Capsid
What are the features of viral genome?
No genes for energy metabolism
No protein synthesis enzymes or ribosomes
No genes for lipid or amino acid synthesis
Few introns
What are the possible structures of viral DNA?
Double stranded
+ve sense- directly translates to protein
-ve sense- translated after being copied into +ve sense
What is the common peplomer of viruses and what is their role?
Glycoproteins- sugar added by host enzyme in golgi
Adhere to host cells surface in first stage of infection
Gives specificity of virus
How is viruses envelope formed?
From host by budding within cell
Define nucleocapsid and explain its role
Capsid and nucleic acid together
Protect nucleic acid from UV light, nucleases
Provide attachment
Packages genome and essential enzymes
What are the two methods of capsid structures of viruses?
1- sheet rolls into cylinder with proteins forming spiral pattern and ends round over to close
2- pentagon in centre surrounded by hexagons leaving gaps whihc close to form football
How do viruses capsid sheets form?
Hexagon proteins surrounded by 6 more
Define viral pathogenosis?
Process viruses cause disease
What are the routes of viral infections and what type of infections are common with them?
Respiratory- upper respiratory epithelial cell infections, later systemic disease
Oral- intestines, systemic disease
Percutaneous- injection through skin
Cutaneous- entry through skin, localised but can become systemic
Sexually transmitted- localised or systemic
Explain highly specific viral infections
Interaction between cell and virus needs exact complementary fit limiting the cells and virus types involved
Explain non-specific viral interactions
Viruses bind to proteins common on many cell types allowing wide host potential
What is the effects of viruses on the host?
Inflammatory response caused by interferon, pro-inflammatory cytokines and chemokines
What are symptoms of virus infection?
Fever Decreased motor activity Reduced responsiveness Reduced food and water intake More sleep Altered cognition Increased pain sensitivity
How is the effect of viruses on cells determined?
How it alters, uses and leaves the cells
What are the two effects of viruses on cells?
Lytic infection- cause cell death when virus leaves cell, complete loss of function
Latent infection- virus persists in cell without causing death, alters growth and division, virus leaves by budding
What effects can latent viral infections have?
Persistent infection- failure of immune system to clear infection
Enhanced cell growth- virus manipulates cell growth causing tumour formation
