FA-Microbiology 1

kcunnu's version from 2015-05-20 03:44

Bacterial Structures

Question Answer
Peptidogycan fn and chem compositionFn: Major bacterial cell wall component. Rigid cell support, protect against osmotic pressure // Chem comp: Sugar backbone with cross-linked (by transpeptidase) peptide side chains
Cell wall components of gram +cytoplasmic membrane, peptidoglycan, capsule, pilus, flagellum, teichoic acid
Cell wall components of gram -cytoplasmic membrane, periplasmic space, peptidoglycan, capsule, endotoxin (LPS), pilus, flagellum
Unique to gram +teichoic acid
Unique to gram -endotoxin/LPS, periplasmic space (location of many beta-lactamases)
Major surface antigen of gram +cell wall/cell membrane. Teichoic acid induces TNF and IL-1
Major surface antigen of gram -outer membrane. Lipopolysaccharide acts as endotoxin. Lipid A induces TNF and IL-1 and o-polysaccharide is the antigen
Periplasm fn and compspace b/w cytoplasmic membrane and outer membrane in gram -. Contains many hydrolytic enzymes, including Beta-lactams
Capsule fn and compprotects against phagocytosis. Polysaccharide (except Bacillus anthracis - D-glutamate)
Pilus/fimbria fn and compmediates adherence of bacteria to cell surface, sex pilus during conjugation. Glycoprotein
Flagellummotility, protein
Sporeprovides resistance to dehydration, heat, and chemicals. Keratin-like coat, dipicolinic acid
Plasmidcontains variety of genes for Abx resistance, enzymes, and toxins. DNA
Glycocalyxmediates adherence to surfaces, esp foreign sorfuaces (indwelling catheters). Polysaccharides

Bacterial Taxonomy

Question Answer
Gram neg coccusNeisseria
Gram pos rodsClostridium, Corynebacterium, Bacillus, Listeria, Mycobacterium
Gram neg rodsEnterics (E. coli, Shigella, Salmonella, Yersinia, Klebsiella, Proteus, Enterobacter, Serratia, Vibrio, Campylobacter, Helicobacter, Pseudomonas, Bacteroides), Haemophilus, Legionella, Bordetella, Yersinia, Francisella, Brucella, Pasteurella, Bartonella, Gardnerella
Branching filamentous gram +Actinomyces, Nocardia
Pleomorphic gram -Rickettsiae, Chlamydiae (= both obligate intracellular)
Spiral gram -Spirochetes (Leptospira, Borrelia, Treponema)
No cell wallmycoplasma. Contain sterols and have no cell wall.
Mycobacteria vs. Mycoplasma cell membrane/wallsMycobacteria contain mycolic acid. High lipid content (high-lipid-content requires Acid fast stain). Mycoplasma cell membranes contain sterols and have no cell wall.

Stains, Cultures

Question Answer
Bugs that do not gram stain"These Rascals May Microscopically Lack Color" Treponema (too thin), Rickettsia (intracellular parasites), Mycobacteria (acid-fast), Mycoplasma (no cell wall), Legionella pneumophila (mostly intracellular), Chlamydia (intracellular parasites)
GiemsaChlamydia, Borrelia, Rickettsiae, Trypanosomes, (malaria)-Plasmodium; Geez, certain bugs really try my patience
PAS (periodic acid-Schiff)diagnose Whipple's Disease (Tropheryma whippelii). Stains glycogen, mucopolysaccharides; PASs the SUGAR, Mr. Whipple!
Ziehl-NeelsonAcid-fast organisms; Zeel can kneel super fast!
India inkCryptococcus neoformans capsule; The secret code was written in CRYPTIC INK
Silver stainfungi (pneumocystis), Legionella, H. Pylori

Special Culture Requirements

Question Answer
Special culture req for H.influenzaeChocolate agar w factors V (NAD+) and X (hematin); FIVE NAbs of CHOCOLATE hits the spot when I have the FLU. But HIM ATE TEN
Special culture req for N.gonnorheaeThayer-Martin (or VPN) media. Vancomycin (inhibits gram+s); Polymyxin (inhibits gram-s); and Nystatin (inhibits fungi). "Martin, To connect to Neisseria, please use your VPN client"
Special culture req for B.pertussisBordet-Gengou (potato) agar (Bordet for Bordetella)
Special culture req for C.diptheriaeTellurite plate, Loffler's media; TELL U what, Diptheria is no LAUGING matter
Special culture req for M.tuberculosisLowenstein-Jensen agar; This TB's got me feeling so LOW
Special culture req for M.pneumoniaeEaton's agar; The pup's EATIN My PNEU MOP
Special culture req for Lactose-fermenting entericspink colonies on MacConkey's agar (fermentation produces acid, turning plate pink); E.coli is also grown on eosin-methylene blue (EMB) agar as colonies with green metallic sheen; PINK MONKEYS like MILK; E Coli has mean green sheen with that eosin-methylene
Special culture req for Legionellacharcoal yeast extract agar buffered w cysteine; Legionnaire with his SILVER helmet, sitting around a campfire (charcoal) with his IRON dagger and a cold glass of beer (yeast). He's no SISSY
Special culture req for fungiSabouraud's agar; Hey, this Sab's a Fun Guy!

Obligate Aerobes vs. Anaerobes...and more diagnostic bacteriology

Question Answer
Examples of obligate aerobesNocardia, Pseudomonas aeruginosa, Mycobacterium tuberculosis, Bacillus Nagging Pests Must Breathe
Aerobes seen in burn wounds, Nosocomial pneumonia, pneumonia in cystic fibrosisP. Aeruginosa
Examples of obligate anaerobesFusobacterium, Clostridium, Bacteroides, Actinomyces Frankly Can't Breathe Air
Lack of what enzymes make obligate anaerobes susceptible to oxidative damangecatalse and/or superoxide dismutase
General characteristics of Obligate anaerobesfoul smelling (short-chain fatty acids), difficult to culture, and produce gas (CO2 and H2). AminOglycosides are ineffective against anaerobes b/c these Abx require O2 to enter bacterial cell
Obligate intracellularRickettsia, Chlamydia. "Stay inside b/c it is Really Cold". Can't make its own ATP
Facultative intracellularSome Nasty Bugs May Live FacultativeLy Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella
What is a Quellung rxn?Diagnostic test to confirm capsular bacteria. Positive quellung rxn is when encapsulated bug capsule swells up when specific anticapsular antisera is added.
Encapsulated bacteria examples and role of capsulesStreptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, E. coli, Salmonella, Klebsiella penumoniae, group B Strep.Put on your CAP and SHiNE your SKiS Capsules serve as an antiphagocytic virulence factor, also antigen in vaccines; are opsonized and cleared by spleen (bad if asplenic)
Encapsulated bacteria vaccinesSome 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 vaccinePCV (pneumococcal conjugate vaccine, i.e., Prevnar); PPSV (pneumococcal polysaccharide vaccine with no conjugated protein, i.e., Pneumovax)
H. influenzae vaccinetype B (conjugate vaccine)
Meningococcal vaccine(conjugate vaccine)
Urease-positive bugsCHuck Norris hates PUNKSS. Cryptococcus, H. pylori, Proteus, Ureaplasma, Nocardia, Klebsiella, S. epidermidis, S. saprophyticus
Catalase positive bugsCats Need PLACESS to hide Catalase - Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E. coli, Staphylococci, Serratia.;
catalase degrades H2O2 before it can be converted to microbicidal products by myeloperoxidase, People with chronic granulomatous disease (NADPH oxidase deficiency) have recurrent infections with
certain catalase ⊕ organisms.
Actinomyces israelii pigment coloryellow "sulfar" granules. Israel has yellow sand
S.aureus pigment coloryellow Aureus (Latin) = gold.
Pseudomonas aeruginosa pigment colorglue/green Aerugula is green
Serratia marcescens pigment colorred - Serratia marcescens—think red maraschino

Bacterial virulence factors

Question Answer
Protein AS. Aureus, Binds Fc region of Ig. Prevents opsonization and phagocytosis.
IgA proteaseEnzyme that cleaves IgA. I Got A SHiN - S.pneumoniae, H.influenzae type B, and Neisseria. To colonize respiratory mucosa
M proteinGroup A Strep. Helps prevent phagocytosis- Anti Macro
Exotoxin vaccinestoxoids used as vaccines - induces high-titer antibodies aka antitoxins
Exotoxin diseasestetanus, botulism, diptheria
Endotoxin vaccinesNon-available.
Endotoxin diseasesmeningococcemia, sepsis by gram neg rods
Source of of endotoxinLPS in gram neg bacterial wall AND Listeria monocytogenes (gram-pos). Heat stable, remember?

Exo vs Endotoxins

Question Answer
SOURCECertain species of gram-positive and gram negative bacteria (exo) vs Outer cell membrane of most gram-negative bacteria
CHEMISTRY Polypeptide(exo) vs Lipopolysaccharide (structural part of bacteria; released when lysed)
LOCATION OF GENESPlasmid or bacteriophage(exo) vs Bacterial chromosome
TOXICITYHigh (fatal dose on the order of 1 μg)(exo) vs Low (fatal dose on the order of hundreds of micrograms)
CLINICAL EFFECTSVarious effects (see following pages)(exo) vs Fever, shock (hypotension), DIC
MODE OF ACTIONVarious modes (see following pages)(exo) vs Induces TNF, IL-1, and IL-6
VACCINESToxoids used as vaccines(exo) vs No toxoids formed and no vaccine available
HEAT STABILITYDestroyed rapidly at 60°C (except staphylococcal enterotoxin)(exo) vs Stable at 100°C for 1 hr
TYPICAL DISEASESTetanus, botulism, diphtheria(exo) vs Meningococcemia; sepsis by gram-negative rods


Question Answer
SuperantigensBind directly to MHC II and T-cell receptor simultaneously, activating large numbers of T cells to stimulate release of IFN-gamma and IL-2 // S. aureus, S.pyogenes
S. Aureus superantigen1. TSST-1 superantigen causes toxic shock syndrome (fever, rash, shock). 2. Other toxins include enterotoxins that cause food poisoning as well as exfoliatin which causes staph scalded skin syndrome
ADP ribosylating A-B toxinsinterfere with host cell function. B (binding) component binds to a receptors on surface of host cell, enabling endocytosis. A (active) component then attaches an ADP-ribosyl to a host cell protein altering protein fxn. // C.diptheriae, V.cholerae, E.coli, B.pertussis
Corynebacterium diphtheriae toxinADP ribosylating A-B toxin. Inactivates elongation factor (EF-2) → causes pharyngitis & pseudomembrane in throat
Vibrio cholerae toxinADP ribosylating A-B toxin. ADP ribosylation of G protein stimulates adenylyl cyclase; increasing pumping of Cl- into gut & decreasing Na absorption. Water moves into gut lumen = voluminous rice water diarrhea
E.T E Coli toxinHeat-labile toxin stimulates adenylate cyclase- increase Cl secretion in gut; Heat-stable toxin stimulates guanyl cyclase- less gut resorption of Cl - both cause watery diarrhea (labile like the Air, stable like the Ground)
Bordetella pertussis toxinIncreases cAMP by inhibiting G_alpha_i → causes whooping cough; impairs phagocytosis
Clostridium perfringens toxinalpha toxin → gas gangrene; phospholipase- get double zone of hemolysis on blood agar
Clostridium tetani toxinblocks the release of inhibitory neurotransmitters GABA & glycine → “lockjaw”
C. Botulinum toxin1. blocks Ach release → anticholinergic symptoms - CNS paralysis, esp cranial nerves. 2. Spores found in canned food, honey → floppy baby
Bacillus anthracis toxinInduces Edema factor. edema factor = a bacterial adenylate cyclase ( ↑cAMP)
Shigella toxinShiga toxin (also produced by E. Coli O157:117) cleaves host cell rRNA - also enhances cytokine release causing HUS
S. Pyogenes toxinStreptolysin O is a hemolysin; antigen for ASO antibody, which is used in the diagnosis of rheumatic fever
Cholera toxin actioncAMP inducer. permanently activates Gs (turns the “on” on) → rice water diarrhea
Pertussis toxin actioncAMP inducer. disables Gi causing whooping cough (turns “off” off) - also inhibits chemokine receptors to promote lymphocytosis.
E coli (ETEC) toxin actionHeat-labile toxin - acts via ADP ribosylation - permanently activates endogenous adenylate cyclase
Endotoxin actions1. Heat stable 2. Activates macrophages --> IL-1, TNF, NO 3. Activates complement (alt pthwy) --> C3a, C5a 4. Activates Hageman factor --> DIC

Bacterial growth and genetics

Question Answer
Lag phase of bact growthmetabolic activity without division
Log phase of bact growthrapid cell division; Pens and Cephs act here because peptidoglycan is rapidly being made
Stationary phase of bact growthnutrient depletion slows growth. Spore formation in some bacteria
Death phase of bact growthprolonged nutrient depletion & buildup of waste leads to death
Spore forming bacterial growth phasestationary phase
Bact transformationAbility to Take up any DNA from environment (aka competence) - S. Pneum, H flu B, Nesseria (SHiN)
Bact F+ X F- conjugationF+ has genes required for conjugation & send their plasmid over through pilus - plasmid genes only, not chromosomal genes
Bact Hfr X F- conjugationF+ plasmid can become incorporated into chromosome of Hfr cell - more than plasmid can transfer (plasmid PLUS some chromosomal genes)
Bact generalized transduction“packaging” event - lytic (virulent) phage infects bacterium, leading to cleavage of bacterial DNA. Parts of bact chromosome DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes.
Bact specialized transduction“excision” event - lysogenic (temperate) phage infects bacterium; viral DNA incorporated into bacterial chromosome. When phage DNA is excised, flanking bacterial genes may come with it. DNA is packaged into phage viral capsid & can infect another bacterium
Bact transpositionSegment of DNA that can “jump” (excision and reincorporation) from one location to another, can transfer genes from plasmid to chromosome & vice versa. When excision occurs, may include some flanking chromosomal DNA which can be incorporated into a plasmid & transferred to another bacterium
Bact toxins encoded in lysogenic phagesABCDE - 1) shigA-like toxin, 2) Botulinum toxin (certain strains), 3) Cholera toxin, 4) Diptheria toxin, 5) Erythrogenic toxin of Strep pyogenes