Micro FA Bacteriology p124 - 133 Flashcards
What is Pilus/fimbria function and what is it made of?
Function:
Mediate adherence of bacteria to cell surface, sex pilus forms during conjugation;
Made of: glycoprotein
Which organisms are spores found in?
Some G+ bact (Bacillus and Clostridum) and fungi.
What is the chemical composition and function of capsule?
Chemical compostion:
Organized, discrete polysaccharide layer (except poly-d-glutamate on B anthracis).
Function:
Protects against phagocytosis
What is the function and chemical compostion of slime layer?
Composed of:
Loose network of polysaccharides.
Chemical composition:
Mediates adherence to surfaces, especially foreign surfaces (eg, indwelling catheters)
What is chemical compostion and the function of periplasm?
chemical composition:
Space between cytoplasmic membrane and outer membrane in gram negative bacteria. (Peptidoglycan in middle.)
Function:
Accumulates components exiting gram negative cells, including hydrolytic enzymes (eg Beta lactamases)
Where is LPS found? components?
LPS found in outer membrane of gram ⊝ bacteria (both cocci and rods).
Composed of : O antigen + core polysaccharide + lipid A (the toxic component).
What is the chemical compositon and function of cytoplasmic membrane?
Chemical compositon:
- Phospholipid bilayer sac with embedded proteins (eg, penicillin-binding proteins [PBPs) and other enzymes.
- Lipoteichoic acids (gram positive) only extend from membrane to exterior.
Function:
- Site of oxidative and transport enzymes;
- PBPs involved in cell wall synthesis.
- Lipoteichoic acids induce TNF alpha and IL-1
What is the chemical composition and function of cell wall?
Chemical compositon:
- Peptidoglycan is a sugar backbone with peptide side chains Cross-linked by transpeptidase aka ( pencillin binding proteins)
Function:
- Net-like structure gives rigid support, protects against osmotic pressure damage.
Which is Unique to Gram positive & Gram negative bacteria?
GP+:
- Has Lipoteichoic acid,
- 2 layers,
- thick peptidoglycal cell wall.
GN-:
- 3 layers ( outer membrane, pepitdoglycan layer, cell wall.
- Endotoxin/LPS and porin in outer membrane
- Periplasmic space (Beta-lactamase location
Cytokines induced by the outer membrane in GN bacteria and cytoplasmic membrane in GP bacteria?
GN- bact
- Outer membrane Endotoxin - Lipid A induces TNF and IL-1,
GP
- Lipoteichoic acids induce TNF-alpha and IL-1
Pleomorphic bact - what does that mean? ex?
Have no cell wall
Chlamydiae (Giemsa)
Rickettsiae (Giemsa)
Ehrlichia
Anaplasma,
Mycoplasma (contains sterols, which don’t gram stain),
Ureaplasma
Explain the gram stain procedure?
1) Pour in crystal violet stain ( blue dye) and wait 60 seconds
2) Wash off with water and flood with iodine solution. Wait 60 seconds
3) Wash off with water and then “decolorize” with 95% alcohol
4) Finally, counter-stain with safranin and appear red.
GP = blue for gram stain
GN = red for gram stain
First-line lab test in bacterial identification. Bacteria with thick peptidoglycan layer retain crystal violet dye (gram +);
GN bacteria with thin peptidoglycan layer turn red or pink (gram -) with counterstain.
These bugs do not gram stain well
(These Little Microbes May Unfortunately Lack Real Color But Are Everywhere).
Treponema, Leptospira——Too thin to be visualized.
Mycobacteria——–Cell wall has high lipid content.
Mycoplasma, ureaplasma———-No cell wall.
Legionella, Rickettsia, Chlamydia, Bartonella, Anaplasma, Ehrilica———–Primarily intracellular; also, Chlamydia lack classic peptidoglycan because of decrease muramic acid.
Giemsa staining is for
Rickettsia, Chlamydia, Trypanosomes , Plasmodium, Borrelia, Helicobacter pylori
Ricky got Chlamydia as he Tried to Please the Bored Hot “Geisha.”
Branching filamentous (gram positive) examples
Actinomyces Nocardia (weakly acid fast)
What does PAS stain diagnose with?
Periodic acid-Schiff stain
Stains glycogen, mucopolysaccharides; used to diagnose Whipple disease
Ziehl- Neelsen stain (carbol fuchsin)
Is for Acid-fast bacteria staining the mycolic acid in cell walls; also protozoa.
Silver stain is seen in
- *F**ungi (Coccidioides, Pneumocystis jirovecii) Legionella
- *H**elicobacter pylori
Hold the FLAg - Ag (Silver)
FTA-ABS stain for what?
syphilis
What medium is used to identify a bacteria with burning with urination (dysuria), increased urge to urinate, and a pus-like (purulent) discharge from the genitals?
Neisseria gonorrhoeae and menigitidis - Thayer-Martin agar (has 5% chocolate sheep blood and anitbiotics)
H. Influenza use the media; what does it contain?
Chocolate agar; Factor V (NAD+) and X (hematin)
For Bordetella, use the stain
Bordet-Gengou agar or Regan-Lowe medium
Culture media for for C diptheriae
Tellurite agar, Löffler medium
Medium for M tuberculosis
Löwenstein-Jensen agar
growth medium for M pneumoniae
Eaton agar - Mycoplasma pneumonia
Mike (Myc) be Eatin’ (Eaton)
Lactose-fermenting enterics use to grow
MacConkey agar (Fermentation produceds acid, causing colonies to turn pink)
Lactose - MILK-Conkey
E Coli - what growth medium, how do we describe the colonies?
Eosin-methylene blue agar; colonies with metallic green sheen
In somebody with fever and mild flu symptoms, but not pneumonia. You deduce they have Pontiac fever. To prove it, what growth media would you use?
Legionella - Charcoal yeast extract agar buffered with cysteine and iron
Legionella, Brucella, Francisella, and Pasteurella all require cysteine-enriched culture media.
Fungi media identification
Sabouraud agar Sab’s a fun guy!
Identify common Aerobic bacteria
- Nocardia
- Pseudomonas Aeruginosa
- Mycobacterium Tb
- Bordetella pertussis
Common Anaerobes; which enzymes do they lack?
- *A**ctinomyces
- *B**acteroides
- *C**lostridium,
- *F**usobacterium
Without O2, A Body Can Fail.
They lack catalase and/or superoxide dismutase and are thus susceptible to oxidative damage
Explain facultative anaerobes, give ex/
May use O2 as a terminal electron acceptor to generate ATP, but can also use fermentation and other O2-independent pathways.
Streptococci, staphylococci, and enteric gram ⊝ bacteria
Obligate intracelluar bugs
Rickettsia, Chlamydia, Coxiella (rely on host ATP) Stay inside when it is Really CHilly and COld
Facultative Intracellular
Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia
Some Nasty Bugs May Live FacultativeLY
Encapsulated bacteria
- *P**seudomonas Aeruginosa,
- *S**tep Pneumoniae,
- *H** Influenzae type B,
- *N**. meningitidis,
- *E** coli,
- *S**almonella,
- *K**lebsiella pneumoniae,
- *S**trep agalaticae.
Please SHiNE my SKiS
Capsules are the antiphagocytic virulence factor
Urease positive organisms; will predispose a pt to what condition?
Proteus
Ureaplasma
Nocardia
Cryptococcus
H pylori
Klebsiella
S epidermidis
S saprophyticus
Leads to struvite kidney stones
What does catalase do? Which def leads to recurrent catalase + organism infections?
Catalase degrades H2O2 into H2O and bubbles of O2 A before it can be converted to microbicidal products by the enzyme myeloperoxidase. People with chronic granulomatous disease (NADPH oxidase deficiency) have recurrent infections with certain catalase ⊕ organisms.
Catalase positive organisms examples
- Nocardia
- Pseudomonas
- Listeria
- Aspergillus
- Candida
- E coli
- Staphy
- Serratia
- B cepacia
- H pylori
Cats Need PLACESS to Belch their Hairballs.
Pigment producing bact - ex/
Actinomyces israelii - yellow sulfur granules
S aureus - yellow pigment
P aeruginosa - blue-green pigment
Serratia marcescens - red pigment
Catheter and prosthetic devices are at risk for which bacteria
Staph epidermidis
A dental plaque/infective endocarditis is seen with what biofilm producing bacteria
Viridans streptococci (s. mutans and S sanguinis)
Unencapsulated H influenzae gives what infection?
Otitis media
Virulence Factors of S.aureus and mechanism
Protein A, binding to Fc region of IgG. prevents opsonization and phagocytosis
IgA protease virulence factor does what? Which bact have it?
Cleaves IgA, then bacteria can adhere and colonize mucous membranes. From S pneumoniae, H influ type B, Neisseria (SHiN)
M protein function, which bact has it?
Virulence factor preventing phagocytosis expressed by Group A strep. Shares similar epitopes to human cellular proteins (molecular mimicry); possibly underlies the autoimmune response seen in acute rheumatic fever.
What is periplasm made of? and fxn?
Space between cytoplasmic membrane and outer membrane in gram ⊝ bacteria. (Peptidoglycan in middle.) Accumulates components exiting gram ⊝ cells, including hydrolytic enzymes (eg, β-lactamases)
What is cell wall made of?
Peptidoglycan is a sugar backbone with peptide side chains cross-linked by transpeptidase.
Selective media? ex?
Favors the growth of particular organism while preventing growth of other organisms, eg, ThayerMartin agar contains antibiotics that allow the selective growth of Neisseria by inhibiting the growth of other sensitive organisms.
Differential media? ex?
Yields a color change in response to the metabolism of certain organisms, eg, MacConkey agar contains a pH indicator; a lactose fermenter like E coli will convert lactose to acidic metabolites –> color change.
How does an encapsulated bacteria vaccine work? ex?
Some vaccines containing polysaccharide capsule antigens are conjugated to a carrier protein, enhancing immunogenicity by promoting T-cell activation and subsequent class switching. A polysaccharide antigen alone cannot be presented to T cells. Pneumococcal vaccines: PCV13 (pneumococcal conjugate vaccine), PPSV23 (pneumococcal polysaccharide vaccine with no conjugated protein) H influenzae type b (conjugate vaccine) Meningococcal vaccine (conjugate vaccine)
Asplenic patients need vaccines against? why?
Asplenics (No Spleen Here) have dec opsonizing ability and thus inc risk for severe infections; need vaccines to protect against: N meningitidis S pneumoniae H influenzae
Which G+ bact produce spores?
Bacillus anthracis - Anthrax
Bacillus cereus - Food poisoning
Clostridium botulinum - Botulism
Clostridium difficile - Pseudomembranous colitis Clostridium perfringens - Gas gangrene
Clostridium tetani - Tetanus
How to kill spores?
Spores lack metabolic activity. Spores are highly resistant to heat and chemicals. Core contains dipicolinic acid. Must autoclave to kill spores (as is done to surgical equipment) by steaming at 121°C for 15 minutes.
What is the type III secretion system?
Also known as “injectisome.” Needle-like protein appendage facilitating direct delivery of toxins from certain gram ⊝ bacteria (eg, Pseudomonas, Salmonella, Shigella, E coli) to eukaryotic host cell.
What is transformation? Ex of bact that use this?
Competent bacteria can bind and import short pieces of environmental naked bacterial chromosomal DNA (from bacterial cell lysis). The transfer and expression of newly transferred genes is called transformation. A feature of many bacteria, especially S pneumoniae, H influenzae type b, and Neisseria (SHiN)
How to prevent transformation?
Adding deoxyribonuclease degrades naked DNA, preventing transformation
T or F Chromosomal DNA is transferred via plasmid in conjugation
F - No transfer of chromosomal DNA.
How does F+ x F- conjugation work?
F+ plasmid contains genes required for sex pilus and conjugation. Bacteria without this plasmid are termed F–. Sex pilus on F+ bacterium contacts F− bacterium. A single strand of plasmid DNA is transferred across the conjugal bridge (“mating bridge”)
What is a Hfr cell?
F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high frequency recombination (Hfr) cell.
In a Hfr x F- conjugation, does the F- cell become a F+?
No, in this type of conjugation, transfer of leading part of plasmid and a few flanking chromosomal genes occurs. High-frequency recombination may integrate some of those bacterial genes. Recipient cell remains F– but now may have new bacterial genes.
What happens in a generalized transduction?
Lytic phage infects bacterium, leading to cleavage of bacterial DNA. Parts of bacterial chromosomal DNA may become packaged in phage capsid. Phage infects another bacterium, transferring these genes.
What happens in a specialized transduction?
An “excision” event. Lysogenic phage infects bacterium; viral DNA incorporates into bacterial chromosome. When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is packaged into phage capsid and can infect another bacterium
Which bact have a toxin encoded by lysogenic phage?
(ABCD’S): Group A strep erythrogenic toxin, Botulinum toxin, Cholera toxin, Diphtheria toxin, Shiga toxin
What is transposition?
A “jumping” process involving a transposon (specialized segment of DNA), which can copy and excise itself and then insert into the same DNA molecule or an unrelated DNA (eg, plasmid or chromosome).
Endotoxins are found in what types of bacteria
eNdotoxins are in the outer cell mem of gram Negative bact
What are endo and exotoxins made of?
Exotoxins - polypeptides Endotoxins - Lipid A component of LPS
Effects of endotoxin
fever, shock (hypotension), DIC
How does endotoxin mediate its effects
thru inducing TNF, IL-1, and IL-6
Which 4 exotoxins inhibit protein synthesis?
Corynebacterium diphtheriae Pseudomonas aeruginosa Shigella spp Enterohemorrhagic E coli
Which two exotoxins inactivate elongation factor 2?
Diphtheria toxin, Exotoxin A (Pseudomonas)
Which two exotoxins inactivate 60S ribosome by removing adenine from rRNA?
Shiga toxin, Shiga like toxin (EHEC)
ShigA - 60S, by removing Adenine
Sx of Diptheria toxin?
Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)
Consequence of Shiga toxin?
GI mucosal damage –> dysentery; ST also enhances cytokine release, causing hemolyticuremic syndrome (HUS)
Shiga like toxin - how does it work? how is it diff from Shiga toxin?
SLT enhances cytokine release, causing HUS (prototypically in EHEC serotype O157:H7). Unlike Shigella, EHEC does not invade host cells
What is the chemical compostion and function of outer membrane?
Chemical compostion?:
Outer leaflet/outer layer: contains endotoxin (LPS/LOS).
Embedded proteins/middle layer: porins & other outer membrane proteins (OMPs)
Inner leaflet: phospholipids.
What is the function?
Gram negative only has outermembrane.
Endotoxin: Lipid A
- induces/release TNF and IL-I;
- antigen O polysaccharide component.
Most OMPs are antigenic.
Porins: transport across outer membrane.
Mech of action of Heat labile and heat stable toxin of ETEC?
HL: Overactivates adenylate cyclase (inc cAMP) –> inc Cl− secretion in gut and H2O efflux
HS: Overactivates guanylate cyclase (inc cGMP) –> dec resorption of NaCl and H2O in gut
Watery diarrhea: “labile in the Air (Adenylate cyclase), stable on the Ground (Guanylate cyclase
How does Bacillus’s edema factor work? leads to what sx?
mimic AC (inc cAMP) - edematous borders of black eschar in cutaneous anthrax
B. anthracis - BA = AC - edema, fluid formation.
Cholera toxin mech?
Overactivates adenylate cyclase (inc cAMP) by permanently activating Gs –> inc Cl− secretion in gut and H2O efflux
How does pertussis toxin work?
Overactivates adenylate cyclase (Inc cAMP) by disabling Gi, impairing phagocytosis to permit survival of microbe
Mech of clostridium tenani and botulinum toxins?
Both are proteases that cleave SNARE (soluble NSF attachment protein receptor), a set of proteins required for neurotransmitter release via vesicular fusion
Tetanospasmin action?
Toxin prevents release of inhibitory (GABA and glycine) neurotransmitters from Renshaw cells in spinal cord –> spastic paralysis, risus sardonicus, trismus (lockjaw)
Botulinum toxin action?
Toxin prevents release of stimulatory (ACh) signals at neuromuscular junction –> flaccid paralysis (floppy baby)
What do the A & B component of a AB toxin do?
B enabling binding and triggering uptake (endocytosis) of the active A component. The A components are usually ADP ribosyltransferases; others have enzymatic activities as listed in chart.
Mech of toxin of clostridium perfringens?
Phospholipase (lecithinase) that degrades tissue and cell membranes
Sx of clostridium perfringens toxin?
Degradation of phospholipids –> myonecrosis (“gas gangrene”) and hemolysis (“double zone” of hemolysis on blood agar
What is the name and mech of Strep pyogenes toxin?
Streptolysin O - prot that degrades cell membrane, esp RBCs
ASO titers (Ab vs ASO) is used to diagnose ___?
Rheumatic fever
Which two toxins cause shock and how?
S aureus - Toxic shock syndrome toxin (TSST-1)
S. pyogenes - Erythrogenic exotoxin A
Cross-links β region of TCR to MHC class II on APCs outside of the antigen binding site –> overwhelming release of IL-1, IL-2, IFN-γ, and TNF-α –> shock (fever, rash, shock)
What are the other two toxins of S. aureus? what do they cause?
other toxins cause scalded skin syndrome (exfoliative toxin) and food poisoning (heat-stable enterotoxin)
When is endotoxin released? 3 main effects?
Released upon cell lysis or by living cells by blebs detaching from outer surface membrane (vs exotoxin, which is actively secreted). Three main effects: macrophage activation (TLR4/CD14), complement activation, and tissue factor activation.
