Zusammenfassung der Ressource
Microbiology: Systematic Bacteriology
- Microorganisms are classified by 4 characteristics
- Appearance/Structure
- 5 features
- Shape
- Cocci
- Sphere shaped
- Diplococcus
- Divides in one to procduce two cocci
- Gram Negative
- Gram Positive
- Aerotolerant
- Streptococcus
- Divides in one plane to produce CHAINS of 4 - 20
- Growth is indifferent to oxygen level
- Streptococcus pneumoniae
Anmerkungen:
- Gram positive alpha haemolytic cocci.
Part of the normal upper respiratory tract flora in many people.
Commonest cause of pneumonia
Also causes severe form meningitis.
- 90+ different capsular types - vaccines available against the commonest 23 types
Majority of UK strains are sensitive to penicillin.
- Commonest cause of pneumonia
Anmerkungen:
- Pneumonia is an acute inflammation of the lungs often caused by pneumococci of the species streptococcus pneumonia.
The alveoli and bronchioles of the lung becomes plugged with a fibrous exudate.
- Also causes severe form meningitis
- Vaccines available
Anmerkungen:
- Against commonest 23 types of streptococcus pneumonia.
- Found in dental plaque of most mammalian species
- Classified using haemolysis
- GAS
- Group A Streptoccoci
- SIGNIFICANT PATHOGENIC STREPTOCOCCI
- Causes various diseases including
- Streptococcal sore throat (scarlet fever)
- Invasive diseases
- Necrotising fasciitis
- Puerperal sepsis
- Infection of pregnant and post natal women
- Aerobic
- Enterococcus
- Causes enteric infections
- Enterococcus faecalis
- Not particularly pathogenic
- Enterococcus faecium
- Part of normal bowel flora
- Cause problems if they get into a normally sterile site
- These are commonest cause of UTIs
- MOST IMPORTANT GROUP OF NON-HAEMOLYTIC STREPTOCOCCI
- Facutative aerobes
Anmerkungen:
- They are versatile organisms, capable of growth under both aerobic and anaerobic conditions. They preferentially use oxygen as terminal electron acceptor.
- Staphylococcus
Anmerkungen:
- Gram positive non-motile bacteria that form irregular grape-like clusters.
- Divides in three planes to produce clumps
Anmerkungen:
- Forms irregular grape-like clusters.
- Infection sources are nosocomial and community
- Nosocominal
- (of a disease) originating in a hospital.
- Types of infection associated with foreign devices
- For example
- Catheter
- MRSA
- Mainly nosocomial
- More commonly affects the elderly and immunocompromised
- Individuals:
- In ICU
- Burns
- Dialysis
- Surgical patients
- With intravenous lines
- Non-motile bacteria
- S.aureus
- Commonest cause of skin, soft tissue and wound infection
- Anaerobic
- Clostridium ssp
- Produces spores
- Clostridium difficile
- Opportunistic pathogen
- Proliferates in the absence of normal flora
- Part of the normal flora of man and animals
- Produces endotoxins that cause severe tissue damage
- Pseudomembranous colitis
Anmerkungen:
- Swelling or inflammation of the large intestine (colon) due to an overgrowth of clostridium difficile bacteria.
- Causes antibiotic associated diarrhoea in the elderly
Anmerkungen:
- Occurs as a result of pseudomembranous colitis (mild to severe 2 days to 6 weeks after antibiotic treatment.
- Endemic could occur
- Strains are producing more toxins
- Antibiotic resistance
- Increased sporulation
- Clostridium perfringens
- Causes "gas" gangrene
Anmerkungen:
- A severe soft tissue infection following contamination of wound.
- Clostridium tetanus
- Causes tetanus
Anmerkungen:
- Tetanus is a usually fatal paralytic illness.
- Bacilli
- Rod shaped
- Can form chains
- May be slightly curved
- For example vibrio (gram negative bacteria)
- Fusiform bacteria
Anmerkungen:
- Small bacteria that are spindle-shaped rods.
- F.nucleatum
- Found in the dental plaque of many promates
- Gram negative
- Strict aerobes
- Pseudomonas aeruginosa
- Legionella pneumophila
- Causes Legionnaires disease
- Usually environmental chest infection
- Anaerobe
- Vibrio cholera
- Causes cholera
Anmerkungen:
- A severe diarrhoeal illness.
- Microaerophilic
Anmerkungen:
- Requires low but not full oxygen tension.
- Campylobacter ssp
- Spiral shaped
- Commonest cause of bacterial diarrhoea in the UK
- Helicobacter spp
- Infects the stomach
- Causes gastritis
- Causes duodenal ulcers
- Capnophiles
Anmerkungen:
- Capnophilic bacteria require increased concentration of carbon dioxide (5% to 10%) and approximately 15% oxygen. This condition can be achieved by a candle jar (3% carbon dioxide) or carbon dioxide incubator, jar or bags.
- Haemophilus influenzae
- Common cause of chest infection
- Controlled by vaccination
- Cocco bacillus
- Gram positive
- Spiral shaped
Anmerkungen:
- Spiral shaped bacteria can be gram positive or gram negative.
- 2 main types
- Rigid
- For example Spirillum
- Flexible
- Spirochaete
- Size
- Arragement
- Structures
- Capsules
Anmerkungen:
- A polysaccharide layer that lies outside the cell envelope of bacteria and is thus deemed part of the outer envelope of a bacterial wall.
It is a well-organised layer, not easily washed off and it can be the cause of various diseases.
- Polysaccharide layer
- Lies outside the cell envelope of bacteria
- Part of the OUTER envelope of a bacterial cell
- Well organised
- Not easily washed off
- Can cause various diseases
- THIS IS NOT THE 2nd LIPID MEMBRANE LATER OF GM -VE BACTERIA
- Found on both Gram Negative and Gram positive bacteria
- Flagella
- Spores
- Inert structures
- Resistant to physical and chemical challenge
- For example C.difficile produces spores
- Spore formation
- BINARY FISSION
- SPORULATION
- PRESPORE
- ENDOSPORE
- SPORE
- GERMINATION
- The development of a spore after a period of dormancy
- Spore-like structure produced by bacteria
- A dormant, tough, and non-reproductive structure produced by certain bacteria
- Cells that later differentiate into spores are then formed
- Formation of spores (the spontaneous division of a cell into four or more daughter cells, each of which contains a part of the original nucleus.
- Method of asexual reproduction in whihc an organism splits in two
- Pili
Anmerkungen:
- This term is interchangeable with fimbria
- AKA Fimbria
- Hair like appendage
- Found on the surface of many bacteria
- Cell wall
- Gram positive
- Examples of common gram positive infectious bacteria in the UK include:
- Streptococcus ssp
- Staphylococcus ssp
- Enterococcus ssp
- Clostridium
- Gram Negative
- Examples of common gram negative infectious bacteria in the UK include:
- Neisseria ssp
- Neisseria meningitidis
- Commonest cause of bacterial meningitis
- Neisseria Gonorrhoeae
- Causes gonorrhoea
- Echierichia ssp
- Verotoxin (VTEC) producing Escherichia coli
- E.coli O157
- E.coli O104
- SIGNIFICANT GUT PATHOGEN
- Salmonella ssp
- SIGNAFICANT GUT PATHOGEN
- Shigella ssp
- SIGNIFACENT GUT PATHOGEN
- Aerobic gram negative cocci
- Appear in pairs on gram film
- Diplococci
- Coliform
Anmerkungen:
- pertaining to fermentative gram-negative enteric bacilli, sometimes restricted to those fermenting lactose, i.e., Escherichia, Klebsiella, Enterobacter, and Citrobacter.
- Gram negative bacilli
- Sometimes restricted to describing lactose fermenting gram negative bacilli
- For example:
- Escherichia
- Klebsiella
- Enterobacter
- Citrobacter
- Can also grow anaerobically
- Grow best in aerobic environment
- Differentiated from each other by:
- Biochemical reactions
- Antigenic structure of cell wall
Anmerkungen:
- The presence of O antigens on the cell wall and H antigens on the flagella of a bacteria are examples of antigens that can be used to distinguish between coliform.
- Serotyping
- If these enter a normally sterile site:
- CAN CAUSE SERIOUS INFECTION
- For example:
- UTI
- Peritonitis
- Bilary tract infectoin
- Patients with coliform sepsis
- Become VERY unwell VERY quickly
- Due to endotoxin
- This is released from the cell wall of gram negative bacteria when they die
- Endotoxin shock
- SIRS
- Systemic Inflammatory Response Syndrome
- GENTAMICIN
- 1st line of antibiotic used to treat infections caused by coliforms
- Gram stain
- Distinguishes 2 major classes of bacteria according to cell wall structure
- Procedure
- 1)Heat fixed film of bacteria on a glass slide
- 2) Stain with CRYSTAL VIOLET for 1 minute and rinse off with water
- 3) Treat with Gram's iodine for 1 minute then rinse with water
- 4) Briefly decolourise with acetone or ethanol
- A few seconds depending on thickness of film
- Bacteria changes colour
- BLACK TO PURPLE
- GRAM POSITIVE BACTERIA
- BLACK TO COLOURLESS
- GRAM NEGATIVE BACTERIA
- 5) Counter stain with basic fuchsin or safranin (pink dye) for 1 minute and tinse with water
- GRAM POSITIVE BACTERIA WILL REMAIN PURPLE
- GRAM NEGATIVE BACTERIA WILL CHANGE FROM COLOURLESS TO PINK
- 6) Blot dry and view under oil emersion
- Has limitations
- There are:
- Gram variable bacteria and bacteria that do not stain with crystal violet/iodine complex
Anmerkungen:
- Examples of gram variable bacteria include mycobacterium tuberculosis and teponema pallidum (causes syphilis)
- Growth requirements
- Used to categorise bacteria
- Aerobic/Anaerobic
Anmerkungen:
- Aerobic bacteria grow in oxygen/air
- Strict anaerobes
- Strict aerobes
- Obligate anerobes
- Bacteria which are killed by oxygen
- Respiration uses electron acceptor other than oxygen
- Smaller reduction potential than O2
- Less protein motive force across membrane (ATP synthase)
- Less energy released per moleule oxidised
- Obligate aerobes
- Bacteria which require oxygen
- Fascilitative bacteria
- Bacteria which tolerate oxygen
- Requirement for blood products
- Serum proteins
- Sensitivity to inhibitory agents
- NaCl
- Bile
- K tellurite
- Media
- Bacteria are grown in selective media
Anmerkungen:
- Selective media: concept that the presence of specific substances permits the growth of one organism over the other.
- For example
- Mannitol salt agar (MSS): 7.5% salt allows preferential isonaltion of staphylococci
- Salmonella-Shingella (SS): Bile salts inhibit coliforms
- Differential media
Anmerkungen:
- Incorporation of chemicals produces visible change colonies that FASCILITATE IDENTIFICATION (differentiation)
- MacConkay Agar
- Fascilitates identification of enterobacteriacecae
- There are several types of blood agar including:
- MacConkey
- CBA
- Cooked Blood Agar
- Contains V factor
Anmerkungen:
- Required by some organisms for growth (complex nutritional requirement).
- This is trapped inside RBCs
- Heated then cooled to 50 degrees celsius in an autoclave
- Chocolate agar
Anmerkungen:
- A type of blood agar in whihchthe blood cells have been lysed by heating for growing fastidious organisms.
- Contains V factor
Anmerkungen:
- Required by some organisms for growth (complex nutritional requirement).
- Released from within erythrocytes
- Blood cells are lysed
- Used to grow fastidious organisms
- Contaminant
Anmerkungen:
- An organism that has gotten into a culture by accident.
- EMB
- Eosin and methylene blue (EMB)
- Allows identification of LACTORSE FERMEMTERS
- For example E.coli
- Coliform
- Enzyme/ metabolic tests
- 3 features used
- Coagulate test
- Haemolysis
- STREPTOCOCCI ONLY
- ALPHA Haemolysis
- Bacteria causes INCOMPLETE lysis of red blood cells
- Therefore GREENISH zones around their colonies are formed
- BETA Haemolysis
- Bacteria causes COMPLETE lysis of red blood cells
- Therefore they form CLEAR zones around their colonies on the blood agar
- GAS
- Group A Streptococci
- GAMMA Haemolysis
- Bacteria cause NO haemolysis of red blood cells
- Biochemical profiling
- For example carbohydrates are metabolised
- Metabolic profiling
- Analyses chemical reactions that regulate humans' health
Anmerkungen:
- Some specific microbiology tests are directly involved with investigating a patients condition/disease.
e.g.
Blood culture
Urine culture
Faeces culture
Swab of pus
Specimens for polymerase chain rection (PCR tests)
Blood serology (Antibody/antigen etc)
- Bacteria utilisation of carbon sources and amino acids are analysed
- Fluids such as plasma and urine (exo-enzyme production of urease is analysed) are often used to gether the necessary information
- Molecular tests
- 3 features used
- Immunological tests
- For example cell surface antigens
- DNA Sequencing
- qPCR
- Real Time PCR
Anmerkungen:
- The process of detecting amplicon (a piece of DNA) (made possible by the labelling of primer, probes or DNA sections with fluorogenic molecules), enabling the visualisation of accumilating DNA sections as the amplification of a DNA progresses during PCR.
- 16sRNA
- Multi Locus Sequencing Typing
Anmerkungen:
- A technique of molecular biology for the typing of multiple loci. The procedure characterises isolates of mictobial species using DNA sequences of internal fragments of multiple housekeeping genes
- MLST
- Protein profiling
- For example mass spectroscopy analysis
- Serological tests
Anmerkungen:
- Tests that detect a specific molecule believed to be there (confirms its presence).
- Detect a specific molecule believed to be there ( it confirms its presence)
- Agglutination
Anmerkungen:
- Process of particles clumping that occurs if an antigen is mixed with its corresponding anti-body (called isoagglutinin)
- MALDI-TOF
Anmerkungen:
- Stands for:
MATRIX
ASSOCIATED
LASER
DESORPTION
-
TIME
OF
FLIGHT
- Various benefits:
Powerful (99% correct)
Rapid (Colony tested in 6 minutes)
Precise (Species, sub species and sometimes strains can be determined)
Cost effective (17 - 32% cost of conventional techniques)
- - Generates a series of ions from a sample dependent on its constituents
- Separates the ion according to mass and charge
- Detects the spectrum of proteins released
- Results in characteristic signature (mass spectroscopy)
- TOF
Anmerkungen:
- Charged ions of various sizes are genrated on the sample side.
Apotential difference between the sample slide and the ground attracts the ions to the detector.
- Velocity of the attracted ions is determined by the LAW OF CONCERVATION OF ENERGY
Anmerkungen:
- As the potenial difference V0 is constant with respect to all ions, ions with smaller mass per charge value (lighter ions) and more highly charged ions move FASTER though the drift space until they reach the detector.
Concequently, the time of ion flight differs according to the mass-to-charge ratio (m/z) value of the ion
- TIME
- OF
- FLIGHT
- MALDI
Anmerkungen:
- The matrix absorbs the ultraviolet light (nitrogen laser light, wavelength 337 nm) and converts it to heat energy.
A small part of the martix (down to 100 nm from top outer suface to analyte) heats rapidly (in several nanoseconds) and is vapourised together with the sample.
- MATRIX
- ASSOCIATED
- LASER
- DESORPTION
- Limitations
Anmerkungen:
- Not so good at identifying:
STREPTOCOCCI
STRAPHYLOCOCCI
- Not so good at identifying:
- STREPTOCOCCI
- STAPYLOCOCCI
- Various benefits:
- Powerful
- Rapid
- Precise
- ost effective
- Bacteria Colony characteristics
- 3 categories
- FORM
- Punctiform
- Circular
- Filamentous
- Irregular
- Rhizoid
- Spindle
- ELEVATION
- Flat
- Raised
- Convex
- Pulvinate
- Umbonate
- MARGIN
- Entire
- Undulated
- Lobate
- Erose
- Filamentous
- Curled
- Colony identification
- Colony innoculated/resuspended
- 100 microlitres is transferred to an automated biochemical profiling machine
- Automated biochemical profiling machine offeres a wide range of tests for common substances
- Pathogenesis
- Manner of development of a disease
- Pathogens are released/spread
- This results in a resevoir of pathogens
- Contact allows entry
- Pathogens infect host
- 5 stages
- Adhere/colonise and invade
- Evade host
- Multiply/ Complete its (pathogen) life cycle
- Exit host (host is damaged
- Release/Spread
- Pathogen
Anmerkungen:
- Harmful organism that produces a pathology.
- Harmful organism
- Produces a pathology
- Opportunistic pathogen
Anmerkungen:
- An organism that causes infection when opportunity/change in natural immunity changes
(e.g. in an immunocompromised individual)
- Causes infection
- When environment changes
- Transient microbes
Anmerkungen:
- Microbes that may attempt to colonise the same areas of the body resistant to microbiota, but are unable to remain in the body for extended periods of time due to:
Difficulty competing with established resident microbes
Elimination by body's immune system
Physical or chemical changes within the body that discourage growth of transient microbes
- Virulence
Anmerkungen:
- Capacity of a microbe to cause damage to the host.
- Endogenous microorganisms
Anmerkungen:
- Microorganisms found externally or internally in the human body that contribute to the natural flora
- Found in human body
- Internally
- Externally
- Contribute to natural flora
- Commensal
Anmerkungen:
- An organism that is part of the normal flora.
(Often mutualistic relationship
Often endogenous organisms)
- Exogenous organisms
- Not part of the human flora
- Includes potential pathogens
- Microbiome
- Totality of:
- Microbes
- Genetic material of microbes
- Environmental interactions
- Toxins are KEY to virulence
Anmerkungen:
- Toxins that have bound to ans been internalised into intestinal epithelial cells (for example) may:
Impair the function of intestinal epithelial cells (diarrhoea)
Stimulate cytokine release and activation of macrophages and monocytes (inflammation)
- BACTERIA
Anmerkungen:
- Prokaryotic, single celled organisms
- Prokaryotic
- Single celled organisms
- Continuum of host response to infection
- 4 categories
- Infection
- May result in:
- Fever
- Mechanism
- 1) Antigen (component of micro-organisms) or lipopolysaccharide (endotoxin) interact with macrophages
- 2) Macrophages release CYTOKINES into bloodstream
- 3) Cytokines travel to ANVERIOR hypothalamus (brain)
- 4) Cytokines also stimulate adverse effects of sepsis
- Prostaglandin E is released, which INCREASES the body's thermal set point
Anmerkungen:
- Normal core body temperature is 37 degrees Celsius.
Body temperature at fever is greater than 38 degrees Celsius
Human pathogens grow best at 37 degrees Celsius. (Growth starts to slow if temperature increases).
- Raising the core temperature is an ADAPTIVE RESPONSE and is considered to be beneficial in fighting infection.
(However harm may result from fever).
- ADAPTIVE RESPONE
- The body now perceives that it is cold
- Starts to "shiver"
- Muscle tone increases>>voluntary muscle movement occur
- Increases metabolic ...
- Vasoconstriction of arterioles
- Limit heat loss by readiation
- Conserves heat
- Increases survival from infection
- Sepsis
- Mechanism
- 1)Small blood vessels become "leaky" and loose fluid into the tissues
- 2)Lower blood volume requires heart to work harder to maintain oxygenation
- HEART RATE INCREASES
- 3)Poor tissue perfusion
- Blood supply to LESS ESSENTIAL organs is shut down to try to maintain blood supply to brain
Anmerkungen:
- Less essential organs include skin, kidneys and liver.
- 4) Blood clotting system is activated
- This is an attempt to stop LOSS OF BLOOD in blood vessels
- BUT this blood loss has been caused by "leaking" as opposed to wound
- Results in clotting of tiny vessels
- Uses up all clotting factors
- Increased risk of hemorrhage
- Host response to SEVERE INFECTION
- Severe sepsis
- Septic shock