prokaryotic disease Flashcards
bacteria and mammals
- most bacteria we come into contact with are non-pathogenic
- the surface tissues (skin and mucous membranes) of a healthy individual are colonised by microorganisms
- many are mutualistic
friendly bacteria
- protect against harmful bacteria by occupying space on surface tissues
- helps with nutrient absorption
pre and probiotics
- prebiotics enhance bacterial growth
- probiotics are friendly bacteria
Koch’s postulates
- conditions that must be met to link a specific microorganism to a specific disease
1. suspected causative agent must be absent from all healthy organisms but present in all diseased organisms
2. the causative agent must be isolated from the diseased organism and grown in pure culture
3. the cultured agent must cause the same disease when inoculated into a healthy susceptible organism
4. the same causative agent must then be reisolated from the inoculated organism
problems with Koch’s postulates
- ethical issues, animal testing, cannot be used in diseases that are human specific
- not all microorganisms can be cultured in a lab
- ignores that disease is the interaction between the pathogen and the host, so pathogens affect different individuals differently depending on health status
pathogenesis, overcoming physical barriers
- skin, entry through cut/wound/pore/hair shaft/splinter/vector e.g. mosquitos, aphids (plants)
- damage to lung cilia from smoking means particulates aren’t pushed out lungs
- damage to stomach acid from antacids, raises pH
- antibiotics kill ‘friendly bacteria’ occupying space in the digestive system
steps in disease process
- contamination, bacteria present
- infection, bacteria multiplying on/in host
- disease, disturbance of host’s normal functions as a result of bacterial growth
pathogen
capable of causing disease in a host
host
organism that harbours another organism
pathogenicity
capability to cause disease
virulence
intensity of disease produced
- can be modified to produce live vaccines that are more adapted to a lab environment and less to a human environment (attenuated bacteria)
direct actions of bacteria adherence
- adhesins = proteins on surface of bacteria/pili/capsule
- anchor organism to host and sticks while bacteria divide, creating a film of bacteria on surface
invasion of deep tissues using hyaluronidase, enzymatic virulence factors
- hyaluronidase enzyme digests hylaronic acid which holds tissues together
- calls can then be pushed apart and bacteria can invade deeper tissues
e.g. Streptococcus spp, necrotising fascitits
invasion of deep tissues using coagulase, enzymatic virulence factors
- coagulase triggers clotting of blood plasma around pathogens, protecting them against the immune system
- the bacteria can then divide and grow in number until there are enough of them to have more chance of overwhelming the host’s defences
- then release streptokinase which dissolves the clot, releasing the bacteria
e.g. S.aureus (mRSA)
exotoxins
soluble, secreted into host tissues
endotoxins
part of the cell wall in gram-negative bacteria, released into host (often when bacteria is killed)
stages in the course of an infectious disease
- incubation period, no symptoms
- prodromal phase, vague symptoms
- invasive phase, most severe signs and symptoms
- acme
- decline phase, declining signs and symptoms
- convalescence period
spreading factors
factors that allow bacteria to spread through tissue e.g. enzyme hyaluronidase
Tuberculosis
- Mycobacterium tuberculosis
- grows very slowly
- ancient disease that mainly affects the lungs
- acidfast bacteria (can be stained using acidfast technique)
- typically inhaled, sometimes digested
- can invade white blood cells, divide then burst
- rapid onset pneumonia like symptoms
- can enter dormancy and cause disease later on when immune system is weaker
- can form granulomas, TB is surrounded by WBCs
- can cause lung scarring
- can cause bone damage, seen in ancient skeletons when vertebrae are fused i spinal column
resurgence of TB
- HIV coinfection
- more common in people with diabetes, malnutrition, alcoholism, IV-drug users
- drug resistant strains e.g. isoniazid and rifampicin
- more strains likely to develop as a long course of antibiotics is needed because of its slow growth, more people stopping antibiotic courses early
bacterial stomach infections
- Helicobacter pylori
- peptic ulcers and chronic gastritis
- treated with antibiotics
- rod shaped with flagella
- thickened end of flagella allows it to swim through protective mucous stomach lining and create ulcers in stomach wall
- produces ammonia, neutrilising stomach acid and raising the pH in its localised area
