Microbiology- Basic Bacteriology Flashcards
Pilus/fimbria
Mediate adherence of bacteria to cell surface;
sex pilus forms during conjugation.
Spore
Gram ⊕ only.
Survival: resist dehydration, heat, chemicals.
Capsule
Protects against phagocytosis
Outer membrane
Gram ⊝ only.
Endotoxin: lipid A induces TNF and IL-1; antigenic O polysaccharide component.
Most OMPs are antigenic.
Porins: transport across outer membrane.
Cytoplasmic
membrane
Phospholipid bilayer sac with embedded
proteins and other enzymes.
Lipoteichoic acids (gram ⊕ only) extend from membrane to exterior.
PBPs involved in cell wall synthesis
Gram ⊕ examples: Spherical (coccus)
Staphylococcus (clusters)
Streptococcus (chains or pairs)
Enterococcus (pairs or short chains)
Gram ⊝ examples: Spherical (coccus)
Moraxella catarrhalis
Neisseria
Gram ⊕ examples: Rod (bacillus) Bacillus
Clostridium Corynebacterium Gardnerella (gram variable) Lactobacillus Listeria Mycobacterium (acid fast) Cutibacterium (formerly Propionibacterium)
Gram ⊝ examples: Respiratory Rod (bacillus) Bacillus
Acinetobacter baumannii Bordetella Burkholderia cepacia Haemophilus (pleomorphic) Legionella (silver stain)
Gram ⊝ examples: Enteric Rod (bacillus) Bacillus
Bacteroides Campylobacter E coli Enterobacter Fusobacterium Helicobacter Klebsiella Proteus Pseudomonas Salmonella Serratia Shigella Vibrio Yersinia
Gram ⊝ examples: Zoonotic Rod (bacillus) Bacillus
Bartonella
Brucella
Francisella
Pasteurella
Gram ⊕ examples: Branching filamentous
Actinomyces
Nocardia (weakly acid fast)
Gram ⊝ examples: Pleomorphic (no cell wall)
Anaplasma, Ehrlichia
Chlamydiae (Giemsa)
Rickettsiae (Giemsa)
Mycoplasma (contains sterols, which do not Gram stain), Ureaplasma
Gram ⊝ examples: Spiral Spirochetes:
Borrelia (Giemsa)
Leptospira
Treponema
Cell wall
Peptidoglycan is a sugar backbone with peptide side chains cross-linked by transpeptidase
Gram + : thick
Gram - : Thin
Wich bacterias dont stain well with gram
“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, Ehrlichia Primarily intracellular; also, Chlamydia lack classic peptidoglycan because of lowmuramic acid.
Giemsa stain
RICKiy got CHLAMYDIA as he TRIed to Please the
BORed “Geisha.”
Rickettsia, Chlamydia, Trypanosomes , Plasmodium, Borrelia
Periodic acid–Schiff stain
used to diagnose Whipple disease (Tropheryma
whipplei)
Ziehl-Neelsen stain
carbol fuchsin
Acid-fast bacteria (eg, Mycobacteria C , Nocardia; stains mycolic acid in cell wall); protozoa (eg, Cryptosporidium oocysts).
*Auramine-rhodamine stain is more often used for screening (inexpensive, more sensitive).
India ink stain
Cryptococcus neoformans
Silver stain
Fungi (eg, Coccidioides E , Pneumocystis jirovecii), Legionella, Helicobacter pylori
Fluorescent antibody stain
Used to identify many bacteria and viruses. Example is FTA-ABS for syphilis
Special culture requirements: H influenzae
Media used and content
Chocolate agar Factors V (NAD+) and X (hematin)
Special culture requirements: N gonorrhoeae, N meningitidis
Media used and content
Thayer-Martin agar
“Very Typically Cultures Neisseria”: Vancomicina, Trimpethoprim, Colistin, Nistatin
Special culture requirements: B pertussis
Media used and content
Bordet-Gengou agar (Bordet for Bordetella)
- Potato extract
Regan-Lowe medium
- Charcoal, blood, and antibiotic
Special culture requirements: M pneumoniae
Media used and content
Eaton agar
Requires cholesterol
Special culture requirements: M tuberculosis
Löwenstein-Jensen agar
Special culture requirements: C diphtheriae
Tellurite agar, Löffler medium
Special culture requirements: Lactose-fermentin enterics
MacConkey agar Fermentation produces acid, causing colonies to turn pink
Special culture requirements:
Fungi Sabouraud agar “Sab’s a fun guy!”
Special culture requirements: E coli
Eosin–methylene blue (EMB) agar Colonies with green metallic sheen
Anaerobes Examples
“Can’t Breathe Fresh Air”
Clostridium, Bacteroides, Fusobacterium, and Actinomyces israelii.
Facultative anaerobes Examples
Streptococci, staphylococci, and enteric gram ⊝ bacteria.
Facultative intracellular bugs
“Some Nasty Bugs May Live FacultativeLY”
Salmonella, Neisseria, Brucella, Mycobacterium,
Listeria, Francisella, Legionella, Yersinia pestis
Obligate intracellular bugs
Stay inside (cells) when it is “Really CHilly and COld”.
Rickettsia, CHlamydia, COxiella
Encapsulated bacteria
“Please SHiNE my SKiS”
Asplenics need vaccines to protect against:
(No Spleen Here)
N meningitidis
S pneumoniae
H influenzae
Encapsulated bacteria vaccines
Pneumococcal vaccines: PCV13 (pneumococcal conjugate vaccine), PPSV23 (pneumococcal polysaccharide vaccine with no conjugated
protein)
H influenzae type b (conjugate vaccine)
Meningococcal vaccine (conjugate vaccine)
Urease-positive organism
“Pee CHUNKSS”
Proteus, Cryptococcus, H pylori, Ureaplasma, Nocardia, Klebsiella, S epidermidis, S saprophyticus
Pigment-producing bacteria
Actinomyces israelii—yellow “sulfur” granules
S aureus—yellow pigment
P aeruginosa—blue-green pigment (pyocyanin and pyoverdin).
Serratia marcescens—red pigment.
In vivo biofilmproducing bacteria
S epidermidis, Viridans streptococci, P aeruginosa, Nontypeable (unencapsulated) H influenzae
Bacterial virulence factors
Protein A Binds Fc region of IgG. (S. auerus)
IgA protease Enzyme that cleaves IgA (No Spleen Here)
M protein Helps prevent phagocytosis, by Group A streptococci, Reumatic fever.
Type III secretion system (injectismoe)
Needle-like protein appendage facilitating direct delivery of toxins from certain gram ⊝ bacteria (eg, Pseudomonas, Salmonella, Shigella, E coli)
Bacterial genetics: Transformation
Competent bacteria can bind and import short pieces of environmental naked bacterial chromosomal DNA. (No Spleen Here)
Bacterial genetics: Conjugation F+ × F–
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”).
Bacterial genetics: Conjugation Hfr × F–
F+ plasmid can become incorporated into bacterial chromosomal DNA, termed highfrequency recombination (Hfr) cell.
Bacterial genetics :Transduction (Generalized)
A packaging “error.” Lytic phage infects bacterium, leading to cleavage of bacterialDNA. Parts of bacterial chromosomal DNAmay become packaged in phage capsid. Phage infects another bacterium, transferring these genes.
Bacterial genetics :Transduction (Specialized)
Lysogenic phage infectscbacterium; 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.
5 bacterial toxins are encoded in a lysogenic phage
(ABCD’S): Group A strep erythrogenic toxin, Botulinum toxin, Cholera toxin, Diphtheria toxin, Shiga toxin.
Bacterial genetics: Transposition
Segment of DNA (eg, transposon) that can “jump” (copy/excise and reinsert) from one location to another, can transfer genes from plasmid to chromosome and vice versa.
critical process in creating plasmids with
multiple antibiotic resistance
Spore-forming bacteria
Bacillus anthracis: Anthrax Bacillus cereus: Food poisoning Clostridium botulinum: Botulism Clostridium difficile: Pseudomembranous colitis Clostridium perfringens: Gas gangrene Clostridium tetani: Tetanus
Endotoxin
LPS found in outer membrane of gram ⊝ bacteria (both cocci and rods). Composed of O antigen + core polysaccharide + lipid A (the toxic component).
ENDOTOXINS: Edema Nitric oxide DIC/Death Outer membrane TNF-α O-antigen + core polysaccharide + lipid A eXtremely heat stable IL-1 and IL-6 Neutrophil chemotaxis Shock
Exotoxins which Inhibit protein synthesis:
- Corynebacterium diphtheriae
- Pseudomonas aeruginosa
Inactivate elongation factor (EF-2)
- Diphtheria toxina
- Exotoxin A
Exotoxins which Inhibit protein synthesis:
- Shigella spp.
- Enterohemorrhagic E coli
Inactivate 60S ribosome by removing adenine from rRNA
- Shiga toxin (ST)a
- Shiga-like toxin (SLT)a
Exotoxins which Increase fluid secretion:
-Enterotoxigenic E coli
Heat-labile toxin (LT)a: Overactivates adenylate
cyclase
Heat-stable toxin (ST): Overactivates guanylate
cyclase
Exotoxins which Increase fluid secretion:
- Bacillus anthracis
- Vibrio cholerae
Edema toxina: Mimics adenylate cyclase ( cAMP).
Cholera toxina: Overactivates adenylate cyclase ( cAMP).
Exotoxins which inhibit phagocytic ability:
- Bordetella pertussis
Pertussis toxina Overactivates adenylate cyclase ( cAMP)
Exotoxis which Inhibit release of neurotransmitter:
- Clostridium tetani
- Clostridium botulinum
Both are proteases that cleave SNARE
- Tetanospasmina: prevents release of GABA from Renshaw cells
- Botulinum toxina: prevents release of ACh signals at neuromuscular junction.
Exotoxins which Lyse cell membranes:
- Clostridium perfringens
- Streptococcus pyogenes
Alpha toxin: Phospholipase (lecithinase) that degrades tissue and cell membranes.
Streptolysin O: Protein that degrades cell
membrane
Exotoxins which are Superantigens causing shock:
- Staphylococcus aureus
- Streptococcus pyogenes
Toxic shock syndrome toxin (TSST-1): Cross-links β region of TCR to MHC class II.
Erythrogenic exotoxin A: overwhelming release of IL-1, IL-2, IFN-γ, and TNF-α.
