Introduction to Microbial World (Bacteria) Flashcards
what are the relationships between humans and microbiota?
symbiosis = the long-term interaction between 2 different biological species
what is an infection?
what is the difference between a primary pathogen and an opportunistic pathogen?
infection: multiplication of a bacterial pathogen within the host
- *primary pathogen:** causes disease when infection - not normally associated with host
- *opportunistic pathogen:** only causes disease in compromised host: sometimes part of normal flora
virulence: quantative ability of a microbe to cause disease
what are 4 basic microbes that can cause pathogens?
what kingdom are they each/
- *1. bacteria:** prokaryote
- *2. viruses:** non living
- *3. fungi:** eukaryote
- *4. protoza:** eukaryote
how do bacteria store DNA?
other general strucutture like?
- orgenelles like what?
- around outside?
how divide?
- *DNA/RNA:**
- *- single circular chromosome** that lies free in cytoplasm
- *-** sometimes: additional plasmids
structure:
- *-** free floating / non membrane organelles
- cell wall
- can have: flagella (motility)
- pili / fimbriae: adherence
- 70S rb (50S & 30S)
Division:
binary fission
what is S of bacteria ribosomes?
70S ribosomes (two subunits with densities of 50S and 30S)
what are some bacteria covered in?
what are pili used for?
what are bacteria spores?
some bacteria: capsulate (polysaccaride). evades immune response
pili: adherence to surfaces
bacterial spores: structures very resistant to physical & chemical agents. often go into dormant state. e.g. Bacillus anthracis, C. difficile
name functions of bacterial cell wall
what are the two different types of bacterial cell wall?
function:
- protects agaisnt desiccation, osmotic shock & mech. shock
- protection agaisnt host immune system: specifc and non-specific
- adherence to surfaces
types:
- *- gram postive
- gram negative**
what determines if bacterial cell wall is gram postive or gram negative?
what else is different between them?
what colours do they stain?
depends on level of peptidoglycan: (and therfore the staining)
- *- thick peptidoglycan:** gram postive - purple stain
a) just one membrane
b) lipotechoic acids sticking out - *- thinner peptidoglycan:** gram negative - negative stain
a) have inner and outer membranes
b) lipopolysaccarides sticking out
c) holes in outermembrane
which one of these is gram +ve / -ve?
+ve = left / -ve right
what are 3 main shapes of bacteria?
Spherical (cocci)
Cylindrical rod (bacilli)
Curved/spiral (spirochetes)
differences between bacteria and eu cells?
- nucleus: eukaryotes - membrane-bounded, bacteria: floating (also plasmids)
- RB: eukaryotes: 80S (60S & 40S), bacteria: 70S (50S & 30S)
- organelles: eukaryotes - mitochondria, golgi apparatus, lysosomes, peroxisomes and ER, bacteria: not those
bacteria divide by binary fission
what does gram stain rely on to show differences in bacteria?
what stain do u use for: a) Mycobacteria, b) fungi & c) spirochaetes? (probs dont need to know tbh)
differences in cell wall (amount of peptidoglycan):
- *- gram postive** = purple
- *- gram negative =** pink
- ( a) Mycobacteria: Zielh-Nielson stain
b) fungi: Cotton blue stain
c) spirochaetes: darkfield microscopy )*
process of gram staining?
Gram stain: Crystal violet –> Iodine –> Ethanol –> Safranin
how are gram postive cocci subclassed? how do u test?
gram postive cocci - to differentiate between cocci do catalase test
- streptococci: catalase negative
- straphylocci: straphylocci positiive
subclassify straphylocci further: coagulase stain:
- **straphylocci coagulase +ve
- straphylocci coagulase -ve**
subclassify Streptococci further:: if can lyse blood or not
- *- beta-haemolytic: lyse blood - complete haemolysis
- alpha-haemolytic:: partially lyse blood
- non-haemolytic: dont**
how do subdivde & test for different:
a) Staphylococci?
b) streptoccoi?
- *staphylococci**: if can coagulate human serum or not
- S. aureus (important human pathogen):* coagulates human serum: coagulase positive
- S. epidermidis (non disease):* does not coagulate human serum: coagulase negative
- *Streptococci:** if can lyse blood or not
- beta-haemolytic: lyse blood - complete haemolysis
- alpha-haemolytic:: partially lyse blood
- non-haemolytic: dont
what are staphylococcal disesases - localised and systemic/>
- *localised:
- pyogenic (**pus making)
- abscesses
- wound infections
- follicultis
- *- MSK:**
- osteomyelitis
- *- Resp infection:**
- sinustis
- pneumonia
- *generalised, systemic** (into blood)
- bacteraemia, sepsis, endocarditis (infection of heart)
name 3 staphylococcoal diseases that caused by entrotoxins?
- acute staph. enterocolitis (food pois)
- *2. staphylococcal ‘scalded skin’ syndrome:**
- Ritters disease
- caused by exofoliative exotoxin
- *3. toxic shock sydrome**
- severe immune response to certain strains of staph. cause superantigens: high fever, rash, low BP, coma, multple organ failure
difference in structure of steptococci and staphylococci bacteria?
streptococcus: chains
staphylococcus: clusters
how are beta-haemolytic steptococci divided?
groups: A-G
depends on which Lancefield antigen is detected on surface
disease caused by Streptococcus pyogenes (Group A)?
- Streptococcus pyogenes* (Group A)
- sore throat
- fever
- rash (strawberry tongue) - scarlet fever
- tonislitis
- infection of upper dermis. if on face: erysipelas ; arm: cellulitis. deeper that skin: can develop into sepsis, flesh eating strep
gram negative rod bacteria?
2 main groups?
gram negative rods:
-
Obligate pathogens:**
1. Salmonella sp: S. typhi, S. paratyphi*
2. Shigella sp: S. dysenteriae, S flexneri, S. sonnei, S. boydii
3. Klebsiella pneumoniae
4. Yersinia sp: Y. entrocolticia, pseudotuberculosis - *Opportunistic pathogens** (mostly live in our gut):
1. Escherichia coli
2. Enterobacter sp: E. aerogenes, cloacae
3. Acinetobacter baumanii
what are enterobacteriaciae?
Enterobacteriaceae are a large family of Gram-negative bacteria that includes a number of pathogens such as Klebsiella, Enterobacter, Citrobacter, Salmonella, Escherichia coli, Shigella, Proteus, Serratia and other species.
These pathogens are present in the human intestinal tract and are a normal part of the gut flora.
what happens when enterobacteriaciae leave gut?
not good !
quite serious:
- wound infection
- UTI
- septicaemia
- neurosurgial meningitis
- pneumonia
how can u classify enterobacteriaciae?
- *- fermentors
- non-fermentors**
- *fermentors**:
- bacteria differ in their ability to produce acids from different sugars (monosac, disac, polysac and alchohol fermentation). used to differentiate bacteria.
what are multitest ID systems?
- combine dozens or organic / inorganic substrates: determine breakdown by colour changes
- e.g. API (analytic profile index) 20: gives a biochemical code for the metabolic profile of that organism
which bacteria arent detected by gram stain - why?
which stain used instead - what shows up?
- *mycobacteria**
- waxy cell wall - lipid rich: resistance to drying, antiobiotics and disinfectants, acids and alkalis, survives in macrophages
- e.g. M**ycobacterium tuberculosis
stain:
Ziehl-Neelson stain -stained bright red
(dont take up gram stain: called Acid-fast)
why cant use gram stain for spirochaetes?
name 2 diseases caused by ^?
too thin cell wall to see with gram stain
- Boreelia burgdoferi: Lyme disease
- Treponema pallidium: syphilis
what important fungi that can see with gram stain?
Candida sp: much bigger cocci than bacteria. cause thrush
what is Aspergilliosis?
Aspergillosis is an infection caused by a type of mold (fungus). The illnesses resulting from aspergillosis infection usually affect the respiratory system, but their signs and severity vary greatly.
describe basic overview of protozoa
which kingdom?
how do u classify?
unicellular eu. organism: typical eu features but also species specific organelles
found in all aq. enviroment (incl. soil and humans)
kingdom: Protista
classify:
locomotion:
-pseudopodia
- flagella
- cilia
name some protozoal diseases pls (3 types)
Apicomplexa: Plasmodium sp (malaria), Toxoplasma gondii, Cryptosporidium
Ameobae: Entamoeba histolytica
Flagelletes: Giardia (diarrhea, malabsorbtion), Leishmania
what are Helminths?
how classified?
- helminths: worms (intestinal parasites)
- classifcation:
- trematodes: flat, non segemented (e.g. Schisosomiasis) - flukes
- cestodes: flat, segemented - tapeworms
- nematodes: round and non segmented
how do you diagnose infections?
need:
- history of patient (travel, symptoms & duration, animals, food)
- clinical exam
- lab investigations: haemotological, biochemical, microbiology / virology
what tests do u use if cant grow microbe (to test) ?
use serological / immunological diagnosis: look for antibodies being present / absent. important for viral infections and hard to grow bacteria
future of bacterial ID? what are the techniques
- MALDI-Tof MS (mass spec)
- *- molecular tests**: PCR (look for bacterial genes) - standard PCR, Real-time PCR, Cephoid GeneXpert
- *- whole genome sequencing
- sequencing bacteria on usb things**
