bacteria (gram) Flashcards
Define pathogen
Organisms that causes of is capable of causing disease
Define commensal
Organism which colonises the hose but causes no diseases in normal circumstances (staph aureus)
Define opportunistic pathogen
Microbe that only. causes disease if the host defences are compromised
Define virulence/pathogenicity
What is the resolving eye of the naked eye
100um
What is the resolving power of a light microscope?
0.2um
what is bacterial nomenclatus
Genus then species
what colour does gram negative stain
pink
What colour does gram-positive stain
Purple
where is DNA transcribed in a bacterium
Cytoplasm
what are the features of a gram positive cells
capsule
peptidoglycan thick
Lipoteichoic acid
What are the features of gram negative cells?
Capsules
peptidoglycan thin
LPS (ENDOTOXIN)
periplasmic space
Describe bacterial environments
can be stored at -80-+80
ph 4-9
can survive without water
some can survive UV
Some can survive radiation
What is the doubling time for E.coli
20-30 mins
what is the doubling time for S.aureus
20-30mins
What is the doubling time for mycobacterium, tuberculosis
24 hours
What is the doubling time for candida albicans
30 mins
What is the doubling time for Mycobacterium leprae
2 weeks
what are the 2 main toxins from bacterium
Endotoxin and exotoxin
endotoxin is LPS (gram neg)
What type of toxin is tetanus
Exotoxin
What cells produce exotoxin
Gram-positive and negative
What cells produce endotoxin
Gram negative LPS
How can bacteria transfer genes
Transformation via plasmid
transduction via phage
conjugation via pilli
what are the obligate intraceuular bacteria
Rickettsia
Chlamydia
Coxiella
What are the 3 classed of spirochaeted
Leptospira
TREPONEMA
BORRELIA
What are tej important GRAM NEGATIVE aerobic and anaerobic bacterium
Aerobic -NEISSERIA
N. meningitidis
N. gonorrhoeae
etc
Anaerobic - VEILLONELLA
What are the important GRAM POSITIVE aerobic and anaerobic bacterium
Aerobic - STAPHYLOCOCCUS
S. aureus
S. epidermidis
STREPTOCOCCUS
Anaerobic - PEPTOSTREPTOCOCCUS
What are the important streptococcus?
BETA-HAEMOLYTIC
S. pyogenes (A)*
S. agalactiae (B)*
etc
ALPHA-HAEMOLYTIC
S. pneumoniae
S. oralis
S. milleri
S. sanguis
etc
NON-HAEMOLYTIC
S. bovis
ENTEROCOCCUS
E. faecalis (D)*
what stain with the ziehl Neelsen stain-positive
Myobacteria
What are the GRAM POSITIVE rods? aerobic and anaerobic
ANAEROBIC - CLOSTRIDIUM
C. perfringens
C. tetani
C. botulinum
C. difficile
etc
PROPIONIBACTERIUM
P. acnes
AEROBIC -CORYNEBACTERIUM
C. diphtheriae
etc
LISTERIA
L. monocytogenes
etc
BACILLUS
B. anthracis
B. cereus
etc
What are the GRAM NEGATIVE RODs aerobic and anaerobic?
ANAEROBIC - BACTEROIDES
B. fragilis
AEROBIC ESCHERICHIA VIBRIO KLEBSIELLA SALMONELLA
staph and strep what what type of bacteria
Cocci - gram-positive - aerobic
staph typically form
a) clusters
b)chains
Clusters
What is the habitat is Staphylococci?
nose and skin
How is Staphylococcus aureus spread?
Aerosol and touch
Whar are Staphylococcus aureus virulence factors
Pore-forming toxins (some strains) - alpha haemolysin & Panton-Valentine Leucocidin
Proteases -Exfoliatin
Toxic Shock Syndrome toxin (stimulates cytokine release)
Protein A (surface protein which binds Ig’s in wrong orientation)
What is MRSA resistant to
Beta lactams, gentamicin, erythromycin, tetracycline
what is haemolysis
Beta = complete clearing
Alpha =some clearing
what is S.pyogenes virulence factors
Exported factors
Enzymes
Hyaluronidase - spreading
Streptokinase - breaks down clots
C5a peptidase - reduces chemotaxis
Toxins
Streptolysins O&S - binds cholesterol
Erythrogenic toxin - SPeA – exaggerated response
Surface factors
Capsule - hyaluronic acid
M protein – surface protein
(encourages complement degradation)
What are some infections caused by s.pyogenes
cellulitis
tonsillitis + pharengutis
Impetigo
scarlet fever
what are some important gram positive bacilli AEROBIC
lISTERIA MONOCYTOGENES -can cause menigitis
BACILUSS ANTHACIS -anthrax
CORYNEBACTERIUM DIPTHERIAE -diptheria
What are some important gram-positive bacilli ANAEROBIC?
C.DIFF -
C.BOTULISM - botulism
C.TETANI - tetanius
what
Which gram has a periplasmic space
Gram negative
Which gram has LPS
Gram negative
What is the peptidoglycan wall made of
Murein
Which gram has a thin peptidoglycan layer
Negative
Which gram has a thick peptidoglycan layer
Positive
What are coliforms
Gram negative
Enterobacteria
Rod shaped
Facultativly anaerobic
Most are motile (flagellaa)
Colonise intestinal tract
Whar is maccoket lactose agar
Plate consisting of lactose ferments (red/pink)
Acid produced by fermentation turns neutral red dye in plate red
What is Xylose lysine deoxycholate plate?
Lactose fermenters turn phenol red into yellow
Isolated salmonella and Shigella
Shigella cannot ferment lactose (remains red)
Salmonella cannot ferment lactose but reduces thiosulphate to produce hydrogen sulphide (black)
is e.choli commensal
Yes
What are some principal infections caused by pathogens?
Wound infections (surgical)
Uti - cystitis
Gatroentitris
Meningitis (neonatal)
what are the 4 species of shigella
S.dysenterae
S. boydii
s. flecneri
S. sonnei
Describe pathogenesis of shigella
Acid tolerant
very low infective dose
Passes by person to person or contaminated food/water
Enters through colonic M cells
release Shiga toxin inhibiting protein synthesis (cell death)
Symptoms include blood diarrhoea
Describe the 2 species of salmonella
S.enterica
Responible for salmonellosis
S.bongori
What are the 3 forms of ssalmonellosis caused by S. enterica
Gastritis.enterocolitis
-food poisoning’s
-6-36hr incubation
Enteric fever (typhoid)
Describe the pathogenesis of salmonellosis
1)Initial ingestion of contaminated food.water
-High infective dose
-Invasion of gut epithelium (small intestine)
-Trancytosed to basolateral membrane
-Enters submucosal macrophages
Replication
- Enteric fever - typhoid/paratyphoid fever (serovars Typhi and Paratyphi)
Poor quality drinking water/poor sanitation
Systemic disease - Bacteraemia (serovars Cholerasuis and Dublin)
Uncommon
what is the omst importunate pseudomonas
Pseudomonas aeruginosa
Describe characterisics of pseudomonas aeroguinosa
Motile
Rod
Opportunistic
AMR
Acute infections
-local and systematic
what is the most famous vibrio
cholera
Describe the characteristics of vibrio cholera
Faculative anaerobe
Saline environments
Ingestion via shelfish an disinfected water
Causative agent of cholera
Most sever diarrhoea disease
Mostly cause by 01 serotype
Describe the pathogenesis of vibrio choler
Faecal oral route - high infective dose
Incubation of hours-5days
Voluminous watery stools
Can lose 20 litres/day + electrolytes
-Dehydration/death
No blood, pus or fever
50-60% mortality if untreated
What are the most important campylobacter?
C.jejuni
C.coli
Describe Campylo bacter
Spiral rods
Unipolar/bipolar flagella
Most common cause of food poisoning
Low infective dose
Mild to severe diarrhoea, often with blood
What type of bacteria is Haemophilus influenza
Parvo bacteria
Describe Haemophilus influenza
Exlusic himan reservoir
Opportunistic infection in children/smokers
-meningitis
Diagnostics
-fastidous
-chocolate agar
Non-motile
what are bacteroides
Gram negative
Rod
Obligate anaerobes
Non-motile
Opportunistic
Often present in polymicrobial infections
Describe Nisseria
Non flagellated diplocci
Gram-negative cocci
Aerobic
2 species
-N.menigititis
-N.gonorrhoea
only know to be found in humans
What is the main different between-N.menigititis and N.gonorrhoea in bacterial structure
the presence of a polysaccharide capsule
what bacterium is responsible for Lyme disease
Borrelia burgdorferi theroigh ticks
What is the most prominent sign to tell Lyme disease?
Bullseye rash
Where bacterium os responsible for weils disease (from rats)
Leptospira interrogans
what bacterium is responsible for syphilis
Treponema pallidum
Describe the bacterium chlamydia
Very small
Non-motile
Cannot gram stain
Cannot culture in media so must use PCR
what are the phases of bacterial growth
lag
exponential
stationary
