bacteriology (done) Flashcards
what are bacteria?
(1 mark)
single cell microbe with simple cell structure
info of bacteria?
(6 marks)
- most bacteria are vital for animal life (commensal) with few being parasites / pathogens that cause disease
- cell contains no nucleus, allowing cells to reproduce rapidly by binary fission
- DNA replicated within the cell, which seperates into 2 daughter cells
- cocci, bacilli / spirochete shape commonly
- can be oxygen obligate aerobe / anaerobe / facultative (can do both)
- produce endo + exotoxin which cause damage to host cell
bacteria general requirements for life?
(4 marks)
- water
- essential nutrients - vary according to species (usually carbon + nitrogen)
- correct pH - most mammalian pathogens require pH of 7.4
- correct temp - optimum temp for most pathogens is body temp e.g. 37-40 degrees C.
danger of bacteria that can form endospores?
(2 marks)
- the endospores are often dormant + resistant to hostile environmental conditions e.g. heat, cold, radiation, disinfectants
- these bacteria commonly cause serious infectous disease that are toxic to many organisms e.g. Anthrax
structure of bacteria?
(11 marks)
- ribosome - protein building, repair damage
- cytoplasmic membrane surrounded by peptidoglycan cell wall gives structure
- gel like matrix ‘cytoplasm’ made up of water, nutrients, gases + waste. contains the cell structures (ribosomes, chromosomes, DNA loops + plasmids)
- various external structures - e.g. flagellae for locomotion
- pilli - enable bacterium to attach to host. also involved with conjunction.
the 3 groups of bacteria based on their response to gaseous exchange?
(3 marks)
- obligate aerobes
- obligate anaerobes
- faculative anaerobes (both O2 + none)
how is bacteria classified?
(4 marks)
- size
- shape
- arrangements
- structure
shapes of bacteria?
(4 marks)
- cocci
- bacillus
- vibro
- spirochette
why might the vet decide to conduct a bacterial culture?
(6 marks)
- disease diagnosis
- treatment management
- antimicrobial selection
- prevent antimicrobial resistance
- environmental surveillance
- post mortem
what does bacterial culture allow?
(4 marks)
- cultivation of bacteria from sample
- identification of cause of infection +/ antibiotic sensitivity test
- ensuring most appropriate antibiotic selected for treatment
- reduces risk of antibiotic resistance
what are the common sampling sites?
(16 marks)
- fluids - blood, urine, CSF. synovial fluid, exudates, semen, sputum
- swabs - ear, skin, wounds, abscess, mucosa
- other - infection control surveillance
how to collect specimen?
(5 marks)
- ensure appropriate PPE available - zoonotic risk
- obtain sample as soon as possible following onset of clinical signs
- obtain the sample prior to administration of medication / 7-10 days post medication if possible
- asepsis should be maintained during sampling process to prevent contamination
- swab samples obtained pre- and post-cleaning and debridement can be useful
swab collection considerations?
(4 marks)
- remove crusts to expose exudate of scabbed lesions
- obtain sample from the edges of the lesions where infection is most active
- sterile saline can be used to moisten swab + improve harvest of cells
- use appropriate transport media, for sample being collected
transport media preservation + storage aims?
(3 marks)
- maintain viability (keep alive)
- prevent reproduction (doesnt look worse than is)
- must contaim essential nutrients
oxygen requirements?
(3 marks)
- obligate aerobes - oxygen for growth
- obligate anaerobes - grow in abscence of oxygen
- facultative anaerobes - grow aerobically when oxygen present, also function in abscence of oxygen
swab preservation and storage?
(5 marks)
- correct use of transport media - depends on sample obtained
- aimies media with charcoal common for aerobic bacteria
- aimies without charcoal
- virus transport media for viral sample
- anaerobic transport media - specific container with vacuum to ensure abscence of oxygen
other sample storage and preservation techniques?
(10 marks)
- urine - boric acid preservative, refigerated
- blood - blood culture broth
- faeces - sterile tube, refridgerated
- CSF - EDTA (DO NOT refridgerate)
- synovial fluid - EDTA
speciment collection considerations?
(7 marks)
- keep specimen cool to avoid bacteria growth
- label container appropriately including potential zoonosis
- deliver quickly to external lab
- follow specific guidelines set by external lab to ensure valid resuts
- full clinical history + patient signalment should be provided to the lab
- ensure containers aterile to prevent erroneous results
- anaerobic bacterial samples should not be exposed to oxygen
bacterial culture aims?
(4 marks)
- maintain viability
- encourage reproduction
- inhibit growth of unwanted microflora
- isolate individual bacterial colonies for species identification
2 types of culture media?
(and what they are used for)
(4 marks(
- liquid nutrient broths - used for bacteria that grow within liquid e.g. blood
- solid (jelly) nutrient solutions - agar based media prepared in a flat petri dish
use of solid media?
(1 mark)
isolation of individual species can only be achieved on solid media
media types?
(4 marks)
- simple media
- enrinchment media
- selective / differential media
- transport media
use of simple basal media?
(and examples)
(2 marks)
provides basic nutrition for growth of nutritionally undemanding species
example: nutrient broth, nutrient agar
use of enrinchment media?
(2 marks)
nutrient agar base with added ingredients to encourage growth of fastidious bacteria e.g. blood, egg