Bacteria and Viruses Flashcards
Define Colonisation
When a disease is present in or on a host but causes no harm or symptoms
Define Infection
The colonisation of an individual or host by a foreign microorganism
Define Disease
Occurs when normal bodily functions are sufficiently impaired to reduce performance leading to specific, recognisable clinical signs
Define Pathogen
Infectious agent that causes harm and disrupts physiological functions
Define Contagion
Spread of disease by close contact
Define Contagious
Spread by contagion directly or indirectly from one individual host to another
Define Virulence
Ability to cause harm to host
Define Transmissibility
The capacity to pass from one host to another, typically determined by the pathogens ability to survive outside the host
Define Infectivity
The ability to penetrate host defences
Define Epidemiology
The study of the occurrence, spread and distribution of disease in populations and is of vital importance in the design and monitoring of effective control policies
Define Endemic
A disease present at a normal level in a region or country
Define Epidemic
A disease where a pronounced increase in incidence has been observed within a country or region
Define Pandemic
An epidemic disease that spreads across many countries or continents
Define Epizoonotic
An animal disease epidemic
What is meant by an opportunistic pathogen?
Looking for opportunities to replicate (for example when a host’s immune system is compromised) and inevitably cause disease
Name the 4 organisms that can cause disease
Bacteria, Viruses, Fungi, Protozoa
What are the 4 characteristics of an ‘effective’ pathogen
Simple Lifecycle
Rapid Reproduction/ Replication
Small in size
Able to mutate
What 5 things do bacteria require to replicate
Nutrients Water Correct Temperature Correct pH Appropriate O2 conditions
What type of microorganism is the hardest for a host to fight off?
Virus
Bacterial Cells consist of a cell wall, plasma membrane, cytoplasm and nucleoid. Name 3 additional structures bacteria can have and their function.
Slime Capsule - Protective Barrier
Flagellae - facilitate movement
Pilli - attachment to other cells and DNA transfer
How do we classify bacteria?
By their cell wall - using a gram stain
Gram +ve cells retain a gram stain
Gram -ve cells don’t retain the stain
Describe Cell walls of Gram +ve bacteria and gram -ve bacteria
Gram + = thick and have very lipid content
Gram - = thin and have 2 layers
What is the purpose of a gram stain?
To determine what type of antibacterial we will use to treat the infection
Name 3 morphologies of Bacteria
Rod (bacilli)
Spiral
Spherical (cocci)
Describe Staphylococcus
Gram +ve
Cocci shape
primary cause of skin infections
resident bacteria of skin but opportunistic
Describe Salmonella
Gram -ve
Zoonotic
Found in digestive tract of animals especially reptiles. (Can be expelled in faeces and then cause issues in humans)
Describe Leptospirosis
Gram -ve
Spirochete morphology
Zoonotic
Usually contracted through infected urine
What causes acute nephritis?
Leptospira canicola
What causes hepatitis?
Leptospira icterohaemmorhagiae
Describe Campylobacter
Gram -ve
S-shape
Zoonotic
Cause campylobacteriosis
How do bacteria reproduce?
Binary Fission
Describe the process of binary fission
- DNA of bacterium uncoils and duplicates
- DNA is pulled to separate polls of the bacterium as it increases the size and prepares to split
- The growth of a new cell wall begins to split the bacterium
- The new cell wall fully develops resulting in complete split
- The new daughter cells have tightly coiled DNA rods, ribosomes and plasmids
What do bacteria do if the conditions for reproduction aren’t suitable?
Can produce endospores (the dormant version of the bacteria)
Define Bacteriocidal
Kills Bacteria
Define Bacteriostatic
Stops replication of bacteria
What Is the proper name for kennel cough?
Bordetella bronchiseptica or canine contagious respiratory disease
What is a virion?
A viral particle (not cell!) in a single complete infectious form of a virus that exists outside of a host cell
Viruses are obligate parasites. What does this mean?
They require another cell to replicate. They render this cell unable to function.
What is the treatment plan for a viral infection?
Supportive Treatment. Viruses cannot be treated therefore we alleviate symptoms until body fights it off
Describe the structure of a virus
Core of DNA or RNA. Surrounded by a protein coat/ capsid. Some may also have an additional envelope.
Name the four forms a virus comes in
- Icosehedral
- Helical
either naked or enveloped
What is a bacteriophage?
A ‘bacteria-eater’
Virus that infects bacteria
Can be used to treat pathogenic bacterial infections
What is a retrovirus
A virus that undergoes backwards replication (reverse transcriptase). Its capable of transforming RNA-DNA and then integrates into the host cell and take over. This way of replication makes these viruses very difficult to treat.
Describe the process of viral replication
- Virion attaches to the host cell membrane
- Enters the cell and injects DNA or RNA
- Takes over the host cell’s metabolism and redirects it to produce viral components
- Fully infective viral particles are released as the host cell bursts
Describe the Rabies Disease
Affects warm-blooded mammals.
Transmitted by saliva (usually bite) and bodily fluids
Zoonotic
Eradicated in the UK (except a species of bat that is still able to carry it)
Notifiable disease
Caused by Rhabdovirus
Incubation period is dependant on the proximity of the bite to the CNS
Reaction to infection can be furious or dumb
If animal has rabies its euthanised
