Microbiology Flashcards
What is a microorganism?
They can be in any place on earth
What are microorganisms that live under extreme conditions called?
extremophiles
What is the environment of halophiles?
high salt conditions
What is the environment of Thermophiles?
Temperatures between 60-120 degrees celsius
What is the environment of Cryophiles
Temperatures below 15 degrees
What is the environment of acidophiles?
ph below 3
What is the environment of alkaliphiles?
ph above 9
What is the environment of xerophiles?
extremely dry desiccating conditions
Name the different bacterial morphology shapes?
coccus, bacillus, coccobacillus, fusiform bacillus, vibrio, spirillium, spirochete
What are the different ways that microorganisms can be classified into?
Shapes, Kingdom, Phylum, class, order, family, genus, species, nucleus and other structures, gram negative or positive, size, type of chromosome, diversity, way they move and reproduction.
Name and describe the different external structures of the bacteria.
Flagellum - via a motor (proton motive force), the flagella whips so that the cell can move.
Pili/sex pili/fimbriae - it has a protein at the tips so that it can attach to the host for the bacteria to colonize. It has a plasmid which can be passed on to another cell via replication (DNA double stranded).
Slime layers - excreted by cells is a gelatinous material that attaches loosely to surfaces and allows smooth movement. Formation of biofilms on teeth. Not highly organised.
Capsules - thick polysaccaride layer that strongly attaches to solid surfaces. Protects cell from desiccation and evades the immune system by preventing phagocytosis. Highly organised.
Describe the gram negative bacteria and positive
The gram positive bacteria has peptidoglycan. The peptidoglycan chains are made up of 2 sugars that each have a peptide. The sugars link and the peptide link to make a long chain thus a strong membrane. The peptidoglycan makes up 90% of the cell wall. 1 membrane.
The negative bacteria has the same structure but thinner and is only 5-20% of the cell wall. This means that it can easily lyse but also it has good ability to transport material. 2 membrane (inner phospholipid and outer)
Describe endospores
• resistant to heat, cold, drying, and many chemicals
• can survive for many years in soil or dust by being latent
• spores germinate after landing on moist, nutrient- rich surface and develop into vegetative cell.
Endospores can be latent until sufficient nutrient is provided and then it can turn into bacteria.
• important for survival, not reproduction (dormant)
• produced by Bacillus and Clostridium
What are the 4 different ways that bacterial diversity can be classified?
Strain - genetic variation within subtypes
isolate - from which infected individual the bacteria was isolated from
serotype - what specified antibody attaches to it
Pathovar - from which tissue in the host it is found in
What is the imune system?
It is everything that has access and in constant motion and change.
What does the immune system do?
monitors molecular shapes of cells that is non self or self in wrong places (antigens), distinguishes between self and non self. Following this it removes, neutralises, alters or assimilate non self.
protects, assists in recofery from infection or tissue damage. Also maintains a relationship with the external environment
What are the sources of antigens?
Viruses, Bacteria, Parasites, Dust particles or cells from other people (transfusion and transplants).
What does the immune system do with the antigen?
Stores it to form a repertoire of different antigenic shapes for recognition. Anything can be an antigen as long as it is large enough to be recognized.
What is innate immunity?
> First line barrier, not improved by repeated antigen exposure.
InvolvesLysozyme, complement, acute phase proteins, interferon
Cells=Phagocytes, Natural
Killer (NK) cells
What is adaptive immunity?
> Comes after innate immunity fails. Improved by repeated exposure.
Involves Lysozyme, complement, acute phase proteins, interferon
Cells= lymphocytes, monocytes, antigen presenting cells
What are the differences and similarities between innate and adaptive immunity?
Difference is adaptive immunity improves on repeated exposure while innate does not improve. innate is a physical barrier and a first line of defense. The are dependent on each other.
Innate immunity has physical, microbial, cellular and humoral factors. Adaptive immunity has cellular and humoral factors.
How do neutrophils work and when do they work?
Work when surface barriers are breached. They phagocytose foreign material. (ingest and digest). The surface receptors on the phagocytes recognize the common features of the bacteria cell wall. The neutrophils then stick and get activated. At which point the phil folds its membrane around the bacteria ingesting it. Digestive enzymes in the phil digest the bacteria.
what is the complement system?
The system is structured with 20 blood proteins that freely move to protect any surface breaches. They do this by
- changing vascular permeability for neutrophils to move- vasodialate
- attracting phagocytic neurtophils - chemotaxis
- coat the foreign material so that they can be easily phagocytosed - opsonisation
- breach the integrity of bacterial cell walls - lysis
how the complement system work?
The system works to
amplify enzymatic cascade
1. One protein gets activated by adhering to the bacterial cell wall
2. That protein then activates other proteins
3. Those proteins activate other proteins which results in the amplification of enzymatic cascade
How does the immune system recognize antigens?
Receptors. Two types of receptors = cell surface receptors and antibodies.
What happens after antigen recognition?
When the first contact occurs an the immune system responds and builds up tolerance by creating self antigens. The response allows the foreign antigen to be stored up for memory for a future improved response. Secondary contact the immune systems recollects the antibodies it used from the primary contact and forms a better response against the antigen.
What happens in the immune response?
The immune system neutralises, inactivates, destroys, disposes of and or assimilates the material recognized. It produces antibodies to recognize and cytotoxic lymphocytes to kill. The responses aren’t immediate.
What is the difference between self and non self?
The immune system learns not to respond to self but can also not respond to non self if the antigen is present before the system has matured. This is called acquired immunological tolerance.
What is the Koch’s postulate?
It is the proof of the germ theory.
- the m.organism must be found in similarly diseased animals. (abandon because germs can be carried asymptomatically so you don’t know if the animal has the disease)
- The germ must be isolated and cultured purely (some organisms cannot be grown in culture)
- the germ should be able to evoke the disease in another susceptible animal.(may not cause disease all the time)
- The germ again should be able to be isolated and cultured
What is symbiosis?
living together in close association
Mutualism?
beneficial to both symbionts
Neutralism:
neither symbiont is affected by relationship
Commensalism:
beneficial to only one symbiont
Parasitism
harmful to one symbiont (host), beneficial to other symbiont (parasite).
Synergism:
two or more microorganisms “team up” to
cause disease. Synergistic or polymicrobial infection.
Pathogen:
microorganism that cause disease (< 3%)
Opportunistic pathogen:
has the potential to cause disease
Ingestion
Salmonella
• Inhalation:
Legionella,
Trauma:
Clostridium tetani
Needlestick:
Pseudomonas
Arthropod bite
Rickettsia,
STD
Neisseria gonorrhoeae
Why does exposure not always lead to disease?
O can’t grow at site of contact, absence of host receptors, lysozyme in tears (antibacterial factors), microbial antagonism (indigenous flora are competitive or produce antibacterial factors), good health, immunity or elimination
What are the four periods in the course of an infectious disease?
1. Incubation period: time between infection and onset
of symptoms
2. Prodromal period: patient feels “out of sorts”
, but no disease symptoms
3. Illness: experience of symptoms associated with disease
4. Convalescent period: time during which the
patient recovers
What is a human carrier and name the 4 types?
A person infected with a particular pathogen without showing disease symptoms.
- Passive carrier: never had the disease
- Incubatory carrier: during incubation period
- Convalescent carrier: recovering from disease
- Active carrier: completely recovered
Localised infection:
pathogens are contained at site of
infection (e.g. abscess).
Systemic infection
pathogen spreads throughout the body
Acute infection:
rapid onset and rapid recovery
Chronic infection:
slow onset and slow recovery
Latent infection
pathogen not completely eradicated after
recovery and can cause symptoms in future (herpes, TB)
Secondary infection:
disease that follows primary infection
(ex. pneumonia after mild respiratory infection)
What are the steps in pathogenesis of infectious diseases?
- Entry: see ‘portal of entry’
- Attachment: binding to host tissue (colonisation)
- Multiplication: at infection site (localised infection)
- Invasion or spread (systemic disease)
- Evasion of host defenses (immune evasion)
- Damage to host tissue: symptoms, disability, death
What is the difference between infectious disease and Microbial intoxication?
In infectious diseae the pathogen causes the disease in the body and can take a while to occur and the immune system responds. With microbial intoxication a pathogen in a cake will produce a toxin which will then be ingested. The toxin will cause the disease quickly causing vomiting or diarrhoea. The toxin can be removed by these methods as well.
How does virulence factors change good bacteria into bad bacteria?
- promote attachment to host cells (adhesins)
- help bacterium to enter host cell (invasins)!
- damage host cell or tissue (e.g. cytolysins)!
- help bacteria to spread from local infection (spreading factors)!
- over-stimulate immune response (immunopathogenic factors)!
- mediate immune evasion !
What do invasins do?
get into cells that don’t have protective measures
What do cytolysins do?
bacteria for example lyse the RBC to take iron thereby destroying the tissue cells for bacteria to spread.
destroy erys, leukocytes and tissue cells
- access to nutrients
- immune evasion
- bacterial spreading
What do biofilms do?
The bacteria create a sticky web of secreted polysaccharides that don’t allow the body’s cells to reach and fix the damaged site.
What do bacteria do the cytokines?
cytokines release signals to attract WBC (chemotaxis) but bacteria destroy these interlukins.
How do bacteria evade the immune system?
- capsules (prevent opsonisation and phagocytosis)
- destruction of phagocytes
- inhibition of phagocyte chemotaxis
- inhibition of phagocytosis
- destruction of complement factors
- destruction of immunoglobulins
- intracellular replication
Why is recognition of self/ immune tolerance not genetic?
In the child genes for Mum’s
receptors against Dad’s
antigens, and Dad’s receptors against Mum’s antigens. Therefore, self tolerance is learned.
Explain the mechanism and give an example of exotoxins.
Clostridium inhibits the release of neurotransmitters across synapses causing tetanus and botulism.
Vibrio cholera secrets electrolytes causing diarrhea.
Staphylococcus aureus releases toxin to cause:
necrosis around them.
cytokine causing toxic shock syndrome using syperantigens - bridge things
E.coli produces Shiga toxins which cause apoptosis.
Remember clown wears silly coloured eyeglasses
Explain the mechanism and give an example of endotoxin.
Gram negative bacteria have lipopolysaccharide in cell wall which causes an inflammatory cascade.
Explain and give an example of cell wall fragment in gram positive that illicit an inflammatory cascade
Gram positive bacteria has lipotechoic acid in its walls causing an inflammatory cascade.
Explain and give an example of hydrolytic enzymes that are produced by S.aureus.
S. aureus enable bacteria to spread through tissues by producing hyaluronidase and protease which digest tissue.
Explain and give examples of a bacteria that inhibit the release of products in the stomach and intestine respectively.
Helicobactor pylori inhibit stomach acid secretion allowing itself to survive in an acidic environment. Giardia lamblia inhibits and degrades digestive enzyme.
Explain and give an example of bacteria that causes the invasion and intracellular multiplication in the body.
Myobacterium tubercolosis takes our body cell shape but still has some bacterial characteristics causing our body to attack to our own body cells.
Explain and give an example of a bacteria that causes the induction of autoantibodies
Streptococcus pyogenes are microbial antigens similar to host antigens evoking an autoantibody response causing rheumatic fever.
Explain and give an example of a bacteria that causes mutation
HTLV-1 carry oncogenes that cause our cells to tumours.
Explain and give an example of a bacteria that causes obstructions in the body
Echinococcusform hydatid cysts that obstructs vessels and other areas.
What are the two ways that the hosts respond to microbes?
Inflammation(non specific) and immune response (antigen specific).
What are the five causes of inflammation?
ischaemic, physical, chemical, infectious or immunological
What are the cardinal signs of inflammation?
Redness Swelling Heat Pain Loss of function pyrexia
Why is the anatomical location of the inflammation important?
The type of tissue injured affects the course of events and structural changes which occur
Describe what Suppuration is
Pus forming organism/pyogenic organism that occurs on solid tissue i.e. an organ
Decribe Abscess
Localised fibroblast boundary
Necrotic, pus-filled centre
Ulcer description
Lesions in epithelial surfaces
Decribe Cellulitis
Inflammatory reaction spreading through connective tissue planes.
What are the primary and secondary responses of inflammation?
The release of mediators both from activated cells and plasma is the primary response.
The secondary response is the vasodialation i.e hyperaemia causing redness and heat at the injury area. Increase oressure in capillaries and veinules resulting lymphatic vessels taking out the fluid.
What are the systemics of inflammation
Monocytes and macrophages release cytokine interlukin or IL-1 which mediate pyrexia. increased temperature means increased kinetic energy and so increased metabolism. Also increased temperature decreases the optimal environment of the bacteria. But, pyrexia must be regulated.
Increased neutrophils (polymorphonuclear leukocytes) and monocytes being made from the bone marrow = leukocytosis
increased number of liver proteins which limit tissue damage, resolve infection and inflammation. Increased clotting factor = Acute Phase proteins
Increased glucocorticoid steroid hormones because of stress. Other organs could be affected when stress is severe or sustained. The hormones try to balance process that are going on.
What are the two groups of lymphoid organs?
Primary and secondary
What are the function of primary lymphoid organs?
Bone marrow = produces B lymphocytes
Thymus = T lymphocytes
What are the function of secondary lymphoid organs?
The mature lymphocytes from the primary lymphoid organs go to the secondary lymphoid organs.
filter foreign matter out of body fluids when immune responses occur.
10% of total lymphocytes circulate at any given time.
Lymph node, Spleen, Peyer’s patches, skin, Tonsils, Adenoids
What is the structure of lymphatic vessels?
Lymphatic vessels have entrances at the ends of the vessels taking interstitial fluid and other inflammatory components. The vessels also have valves which allow fluid flow in one direction which is towards the thoracic duct.
Why do we need to return fluid?
Increased fluid to damaged cells causes swelling of cells in the area. So, the fluid is collected slowly from the cells into the thoracic duct and back to the heart and blood vessels. The vessels do this by muscle movement when you relax and contract.
Lymphatic vessels also allow constant communication and thus status reports.
What do microfilaria parasitic worms do?
Attaches to walls of lymph vessels drinking the fluid and blocking vessels and lymphatic drainage. This causes swelling of the area because it can’t return fluid from cells. The vessels collapse. No drainage means massive swelling.
What are the two ways that the body knows about infection?
One =
bacteria get into lymphatic vessels and to the secondary lymphoid organs.
Two=
Langerhans’ cells ingest the bacteria which then get into the lymphatic vessels and thus into the secondary lymphoid organs. The cells become dendritic cells presenting the antigens. T Lymphocytes cluster around them in nodes test with their receptors if they should respond. Specific T lymphocytes respond.
