7-8 Bacteria: Gram+ Flashcards
Gram+ cell wall components
and which dye only stains gram+ bacteria ?
- Thick Peptidoglycan layer
- (Lipo)teichoic accids
- Cell membrane (phospholipid bilayer)
- Membrane proteins
Crystal Violet stains peptidoglycan of gram+ cells
Fuchsin will stain gram- bacteria
- Peptidoglycan components
+ - function
- Which antibiotics inhibits peptidoglycan formation and how ?
- N-Acetyl Glucosamine and N-Acetyl muramic acid alterated strain crosslinked by 2 crosslinked tetrapeptides
- Rigidity + protection
- Penicillin inhibits DD-transpeptidase whoch leads to crosslinking of the tetrapeptides
Characteristics of gram+ bacteria
1. mobility
2. cell wall components unique
- only few species have flagella
- teichoic acids: Glycerol phosphates bound to carbohydrates
Gram+ bacteria overview species and how to identify
Staphylococci
- Charcterization (3)
- Enzymes (2)
- Disease (2)
- Proteins 6)
- Further Protection from host mechanism (1)
- cluster cocci, non motile, facultative anaerobic
- Catalase+ (ROS protection like H2O2 into H2O and O)
Coagulase+: converts fibrinogen to fibrin -> blood clotting, fibrin decoration protects from phagocytosis
- pathobiont of skin and RT, CAP
- Surface Protein A bound to cell wall
collagen binding proteins for binding to host
Hemolysins (alpha)
Leukotoxin
Superantigen
C5a peptidase - Capsule
Pili in bacteria
1. species
2. function
3. Biogenesis
- gram+ and gram-
- Structures to adhere to host material
- Sortase mediated biogenesis of pili using SpaC and SpaA that are translocated via Sec translocation complex and sortase will stack them and in the end bind to peptidoglycan
MRSA
1. mechanism
2. Alternative
Methilin-resistant SA
1. SA ß-lactamase producer, but Methicillin is ß-lactamase stable, but resistancy is now >80%
Alternative: Vancomycin, but also emerging resitances
Staphylococcus epidermidis and saprophyticus
- Health care associated
- normal pathobiont
- Risk: surgical implant /catheder cause it forms biofilm on surfaces (epidermidis)
- UTIs (saprophyticus)
Hemolysins
alpha:
produced ROS oxidate Fe2+ in heme
beta:
secreted haemolysins lyse RBCs
gamma: no lysis
Enterococcus faecalis
1. Disease
2. Characteristics
3. Testing
- UTIs, Endocarditis
- bile and optochin sensitive
- Testing
Hydrolyses aesculin (culture additive) to form aesculetin (black agar)
Listeria monocytogenes
Shape, growth conditions and disease, characteristics
Chem. characterization
motile at 25°C, non motile at 37°C
Gastroenteritis, Meningitis/Sepsis neonatal or immunocompromised
Hemolytic, catalase+. NO3 reduction negative (test for nitrate reductase)
Which factor in Listeria is most important virulence factor and whats its function ?
Which mechanism is involved in PrfA activity ?
PrfA (positive regulatory factor A)
PrfA is the global regulator of virulence, that is almost silent at 30°C due to a inhibitory hairpin in PrfA RNA that loops mask ribosome entry site, it melts at 37°C so RNA can be translated
PRfA activated diffferent virulence factors like Internalin A,B,C, plcA,B and actA
Mechanism: Sugar transport
Enviroment:
Glucose/Cellobiose uptake via Phosphotransferase system, PEP Phosphat cascade to phosphorylate EIIB for uptake to start glycolysis
Intracellular
No PTS dependent Glucose-6-phosphate uptake via Hexose phosphate transporter,
EII2A stays phosphorylated so it cant inhibit PrfA
In which bacteria Internalin is present and whats the mechanism ?
Internalin A/B is present in Listeria
A
exploits tight junction protein E-cadherin as receptor for entry
B
exploits Hepatocyte growth factor receptor Met to promote cytoskeleton rearrangements and entry
How does Listeria escape from the phagosome ?
And how to transmit in next cell ?
Listeriolysin becomes pore forming oligomer at low pH, factors plcA/B involved
ActA: Actin assembly-inducing protein that helps to bound to actin tails for transmission to next cells
Endospores
7 stages + components
1: vegetative under unfavorable conditions
2: Asymetric cell division to form prespore with septum to mother cell
3: Engulfment of forespore by mother cell plasma membrane
4: Cortex (Peptidoglycan)
5: Uptake pf dipicolinic acid to decrease core water content and forming of spore coat to protect from toxins
6: Maturation
7: cell lysis
Core, Inner membrane, Cortex, Outer membrane, Spore coat, Interspace, Exosporium, Exosporium nap
Bacillus anthracis
Characteristics
Virulence factors and mechanism
Obligate pathogen
Capsule of D-glutamic acid to avoid phagocytosis
Exotoxins
1. Protective Antigen binds to receptor CM2 that normally binds Collagen 4/Laminin
- Processed by Furin
- Heptamer, binding of Endema factor (adenylate cyclase) or Lethal factor (Zn2+ dep. Metalloprotease that cleaves Map kinase kinase
- Endocytosis
- Release into cytosol by PA
leads to systemic immune dysregulation, in the end vascular leakage for long distance toxin effects
Clostridium difficile
Where does it occur and whats a risk factor ?
When symptomatic
Treatment
Virulence factors
Antibiotic associated in hospitals, only Vancomycin useful, others diarupt flora so Clostridium has advantage cause of resitancy
only symptomatic if toxigenic species and no igG response to ToxA
Vancomycin
Enterotoxin A and Cytotoxin B
receptor mediated, clathrin dependent endocytosis by epithelial cells > acess to cytosol > increase in epithelial permeability > cell death
Clostridium perfringens
Special disease
usually harmless, but in immunocompromised leads to death untreated
shortest generation time (6.3 min)
resitant to formaldehyde and heat, more 02 tolerant than other clostridium, hemolytic
Gas gangrene
Tissue necrosis caused by Exotoxins, antibiotics ineffective cause they do not reach necrotic tissue (25% fatality rate)
Therapy
Hyperbaric Oxygen chambers, removal of necrotic tissue,
Clostridium tetani
1. therapy
2. Disease + mechanism
- vaccination: inactive toxin
- infection via wounds:
Tetanospasmin that inhibits inhibitory neurons in the CNS causing muscle spasms
Endocytosis by motorneurons, retrograde transport to CNS, endocytosis by inhibitory neurons, translocation into cytosol, cleavage of synaptobrevin, inhibition of synaptic vesicle fusion, no release of GABA and glycin, motor neurone firing
Clostridium botunilum
deadliest toxin
same as Tetanus, but with activating neurons
Corynebacterium diphteria
Vaccination
Disease
Mechanism
- Toxoid based, >85% herd immunity
- often asymptomatic, but can lead to Myocarditis etc.
Mechanism
Diphtheria Exotoxin Fragment A & B
-Fragment B binds to heparin-binding epidermal growth factor-like growth factor)→ acidification: fragments A & B detach→ Fragment B forms pores in the endosomal membrane→release of fragment A into the cytosol→blocks elongation factor 2, which is responsible for transport of tRNA→inhibition of translation, protein synthesis
Streptococci strains
1 special fact and 4 virulence factors
Mutans
Dental caries
PspA: Aherence + Mn2+ permease
WapA: adherence
Acid production
SAG: salivary agglutinin
Pneumoniae
there is a vaccine (polysacchride-protein conjugate)
PspA
Capsule
Pneumolysin
Superoxide dismutase
Pyogenes
pathogen, test via agglutination assay (antiobody caoted latex beads)
protein M prevents phagocytosis
T-antiegn (pili backbone)
Capsule
C5a peptidase
MAC: IgG degradign protease
agalacticae
Capsule
C5a peptidase
Hemolysin
Complement factor H protects from colplement activation
