Infections Flashcards
What are the characteristics of Gram negative bacteria?
- They have a cell wall
- Have a low amount of peptidoglycan
- Not sensitive against penicillin or lysozyme
- Are sensitive against mechanical pressure
e.g. E.coli
What are the characteristics of Gram positive bacteria?
- Have a cell wall
- High amount of peptidoglycan
- Sensitive against penicillin lysozyme
- Not sensitive against mechanical pressure
E.g. Bacillus anthracis
What is venereal transmission?
Skin to skin contact in the genital area- STDs
How does vector transmission occur?
Bites via an infected vector e.g mosquito
How does vertebrate reservoir transmission occur?
Via contact with animals e.g dogs
How does vector-vertebrate reservoir transmission occur?
When an insect/vector infects an animal and then the animal infect us
What are some examples of diseases transmitted via a vector?
Malaria
Sandfly fever
Typhus
What are some examples of diseases transmitted via a vertebrate reservoir?
Rabies
What are some examples of diseases transmitted via vector-vertebrate transmission?
Plague
Yellow fever
What is horizontal transmission?
Humans infecting the community via air, water, food etc
What is vertical transmission?
Infecting others through generations e.g. milk, placenta
What causes borrelia burgdorferi?
Ticks
What can aborrelia burgdorferi infection lead to?
Lyme disease
How can pneumonia be acquired?
Community or hospital
What bacteria is the largest cause of community and hospital acquired UTIs?
E.coli
Community- 80%
Hospital- 40%
What does bacillus anthracis cause?
Anthrax
What does bacillus cereus cause?
Food poisoning
How can cholera be transmitted?
Drinking contaminated water
improperly cooked seafood
What are the symptoms of cholera?
Diarrhoea
Abdomincal cramps
Nausea
Vomiting
Dehydration
What usually5 leads to a cholera outbreak?
A natural disaster as there is a disruption of sanitation in most cases.
What bacteria causes cholera?
Vibrio Cholerae
What is the mechanism of action of cholera?
- The vibrio cholerae bacterium produces a cholera toxin
- This cholera toxin binds to GM1 (Ganglioside receptor) receptors in the GI tract
- A subunit of the toxin, enters the epithelial cell and binds to and activates the G-alpha-s subunit
- The g-alpha-s subunit activates adenyl cyclase
- Adenyl cyclase produces cAMP which activates the CFTR (Cystis fibrosis transmembrane conductance regulator)
- This leads to an efflux of Cl- ions out of ht expel and into the lumen of the GI tract. As Cl- leaves it also causes an efflux of Na+ and H20 into the lumen.
- This movement of water leads to watery diarrhoea
Name two pyogenic cocci bacteria?
- Staphylococcus aureus
- Methicilin resistant Staphylococcus aureus (MRSA)
What can be used to treat MRSA?
Vancomycin
What can Clostridium petani cause?
Tetanus
What can clostridium perfringens cause?
Food poisoning, wound infection and gangrene
What can clostridium difficile cause?
Sever colitis (inflammation of the colon and rectum)
What is the first sign of tetanus ( Clostridium tetani) and what is the progression?
First sign is lock jaw
The causes stiffness of the neck and back
30% of people die from tetanus
How does tetanus (Clostridium tetani) cause stiffness?
The clostridium tetani bacteria produces a toxin called tetanospasmin.
This toxin blocks the inhibitory transmitter release from the pre-synaptic neuron. As this inhibitor is blocked, it means constant stimulation of excitatory transmitters so the muscles are unable to relax.
What is salmonella
Food associate diarrhoea
How does the salmonella bacteria make us ill?
- The salmonella enteriditis is ingested through food
- The bacteria gets absorbed by epithelial cells in the small intestine
- The bacteria can then penetrate these cells and reach the lamina propria layer of the ileocecal region
- The bacteria will then multiply in the lymphoid follicles causing hyperplasia of the reticuloendothelial cells and hypertrophy.
- The inflammatory response also mediates the control of prostaglandins which stimulates the production of cAMP and therefore active fluid secretion = diarrhoea
What is the incubation period of salmonella?
6 hours- 2 days
What fungus causes Vaginal thrush?
Candida albicans
Why is polio much rarer nowadays?
Due to the success of the polio vaccine
What is the breakdown of the severity if polio infections?
- asymptomatic illness: 90% of infections
- abortive poliomyelitis: non-specific febrile illness, occurring in 5% of infected people: fever, headache, sore throat, vomiting
- nonparalytic poliomyelitis or aseptic meningitis: in 1-2% of patients, progression of virus into CNS causes back pain and muscle spasms in addition to symptoms of above
- paralytic polio: occurs in 0.1-2% of patients, appears 3-4 days after the first symptoms have subsided, thereby producing a biphasic illness, virus spreads from the blood to the anterior horn cells of the spinal cord and the motor cortex of the brain, severity of paralysis is determined by the extent of the neuronal infection and which neurons are affected
How can polio be spread?
Usually via contact with infected stool
Can also be by droplets (much rarer)
What is special about small pox?
It has been eradicated since 1980
What causes measles?
A single-stranded, enveloped RNA virus from the paramyxovirusoviridae family.
What two factors greatly impact the impact of measles on a child?
- Level of nourishment
- Level of medical care available
How is measles spread?
Through coughing and sneezing, it then replicates in the respiratory tract and then the lymph nodes
How is hepatitis A spread?
Faecal-oral spread
How can you contract Hepatitis A?
Contaminated water or food ( especially shellfish)
What are the symptoms of hepatitis A?
- fever
- fatigue
- nausea
- loss of appetite
- abdominal pain
What percentage if people with hepatitis A get jaundice?
70-80% of adults
10% of children over 6
What may be given to treat/prevent hepatitis A?
Prophylaxis with immune serum globulin
What can increase cases if hepatitis A?
- Poor hygienic conditions
- Overcrowding
What are the major sources of infection for hepatitis B?
Blood, saliva, semen, milk
How is hepatitis B spread?
Injection into bloodstream
sexual contact
birth
What family do the influenza A, B and C viruses belong to?
orthodoxoviridae family
What causes the annual epidemic of influenza virus?
Genetic instability (mutation: drift)
What are rhinoviruses responsible for?
At least 30% of common colds
What is the incubation period of rhinoviruses?
8-10 hours
What is the second most prevalent causes of the common cold?
Coronaviruses (10-15% of common colds)
What is the incubation period of coronaviruses?
3 days
How are coronaviruses spread?
Via aerosols and droplets (coughs and sneezes)
What are zoonosis?
An infectious disease passed to humans from animals
What are the four ways you can catch a zoonosis virus?
- Bites and scratches e.g. rabies
- Vectors carrying pathogens e.g. Ticks carrying Rocky Mountain spotted fever
- Contact- dermatophyte fungi
- Faeces- e.g. hookworm disease
What are two infections caused by the family of viruses known as filovirus?
Ebola and Marburg virus
What are filoviruses?
Filamentous (thin, thread-like), enveloped, negative-strand RNA viruses
What do the filoviruses cause (ebola and Marburg virus)?
Severe or even fatal haemorrhagic fever
What were the tow species of ebola identifies in 1976?
Zaire Ebola virus- ZEBOV
Sudan Ebola virus- SEBOV
Fatality rates of 83% and 54%
How is the Ebola virus transmitted?
By coming into contact with infected blood or other bodily fluids.
What is the incubation period of Ebola virus?
2-21 days
What are the initial and secondary symptoms of ebola?
Initial:
- Nausea
- Exhaustion
- Headache
- High fever ( at least 38.8’)
- Muscle/joint/abdominal ain
- Sore throat
- Dizziness
Secondary: Internal and external bleeding
- Dark or bloody stools
- Vomiting blood
- Red eyes from swollen blood vessels
- Red spots on skin from subcutaneous bleeding
- Bleeding from nose, mouth, genitals and rectum
also low blood pressure, fast but weak pulse, and Logan damage of kidney ands liver
What animal is though to cause ebola?
Fruit bats
What do retroviruses look like?
Envelopes, positive-strand RNA genome
How does a HIV virus infect us?
- The HIV virus enters the body through transmission by blood or other bodily fluids, sex and injections.
- The HIV virus binds to a CD4 receptor (via gp120 and releases gp41 to allow virus into the cell.)
- This the needs to bind to a chemokine receptor- either CCR5 or CXCR4
- The virus can then enter the cell by fusion of viral envelope with the membrane
- The core of the virus is released and the RNA genome is reverse transcribed into a double stranded DNA strand
- This strand is ligated to a circular plasmid
- This plasmid will then integrate itself into host DNA- Forming A provirus
- It is then transcribed into a dingle strand of RNA and then translated to assemble a viral protein and assembles in a nucleocapsid
- This virus can now undergo budding with the membrane and be released to go on to infect other cells
The virus will infect macrophages and CD4+ t-cells and lyse them. This lack of CD4+ t-cells causes a lack of immune response leading to immunodeficient and can leas to AIDs dementia, lymphoma and kaposis sarcoma.
How can HIV be treated?
- CCR5 inhibitors e.g. Maraviroc
- Reverse transcriptase inhibitors- block this enzyme so virus can’t integrate into out genome
- Protease inhibitor- prevent budding of the virus to the membrane so it can’t leave the host cell to infect other cells.
What is a prion?
A proteinaceous infections particle made only of proteins ( no DNA or RNA).
- Unlike other pathogens, prions are resistant to denaturation.
