MICROBIOLOGY & IMMUNOLOGY
MICRO: Clinical Bacteriology
Click on the
-?-
to reveal/hide the answer.
| STRUCTURE | FUNCTION | CHEMICAL COMPOSITION |
|---|---|---|
| Peptidoglycan | -?-Gives rigid support, protects against osmotic pressure | Sugar backbone with cross-linked peptide side chains |
| Cell wall/cell membrane (gram positives) | -?-Major surface antigen | Teichoic acid induces TNF & IL-1 |
| Outer membrane (gram negatives) | -?-Site of endotoxin (lipopolysaccharide); major surface antigen | Lipid A induces TNF & IL-1; polysaccharide is the antigen |
| Plasma membrane | -?-Site of oxidative & transport enzymes | Lipoprotein bilayer |
| Ribosome | -?-Protein synthesis | RNA & protein in 50S & 30S subunits |
| Periplasm | -?-Space between the cytoplasmic membrane & outer membrane in gram-negative bacteria | Contains many hydrolytic enzymes, including β-lactamases |
| Capsule | -?-Protects against phagocytosis | Polysaccharide (except Bacillus anthracis, which contains D-glutamate) |
| Pilus/fimbria | Mediates adherence of bacteria to cell surface; sex pilus forms attachment between 2 bacteria during conjugation | -?-Glycoprotein |
| Flagellum | Motility | -?-Protein |
| Spore | Provides resistance to dehydration, heat, & chemicals | -?-Keratin-like coat; dipicolinic acid |
| Plasmid | Contains a variety of genes for antibiotic resistance, enzymes & toxins | -?-DNA |
| Glycocalyx | Mediates adherence to surfaces, especially foreign surfaces (e.g., indwelling catheters) | -?-Polysaccharide |
| Property | Exotoxin | Endotoxin |
|---|---|---|
| Source | Certain species of some gram-positive & gram negative bacteria | -?-Cell wall of most gram-negative bacteria |
| Secreted from cell | -?-Yes | No |
| Chemistry | Polypeptide | -?-Lipopolysaccharide |
| Location of genes | -?-Plasmid or bacteriophage | Bacterial chromosome |
| Toxicity | High (fatal dose on the order of 1 pg) | -?-Low (fatal dose on the order of hundreds of micrograms) |
| Clinical effects | Various effects | -?-Fever, shock |
| Mode of action | Various modes | -?-Includes TNF & IL-1 |
| Antigenicity | -?-Induces high-titer antibodies called antitoxins | Poorly antigenic |
| Vaccines | Toxoids used as vaccines | -?-No toxoids formed & no vaccine available |
| Heat stability | -?-Destroyed rapidly at 60°C (except staphylococcal enterotoxin) | Stable at 100°C for 1 hour |
| Typical diseases | Tetanus, botulism, diphtheria | -?-Meningococcemia, sepsis by gram-negative rods |
Bugs with extoxins/Gram-positive bugs/mode of action:
-?-(b) Corynebacterium diphtheriae Inactivates EF-2 by ADP ribosylation (similar to exotoxin A of Pseudomonas); causes pharyngitis and "pseudomembrane" in throat
(a) S. aureus (b) corynebacterium diphtheriae (c) clostridium tetani
-?-(a) C. botulinum Blocks the release of Ach; causes anticholinergic symptoms, CNS paralysis; spores found in canned food, honey (causes floppy baby)
(a) C. botulinum (b) streptococcus pyogenes (c) C. perfringens
-?-(b) C. perfringens toxin is a lecithinase; causes gas gangrene; get double zone of hemolysis on blood agar.
(a) bacillus anthracis (b) C. perfringens (c) S. aureus
Bugs with extoxins/Gram-negative bugs/mode of action:
-?-(c) E. coli Heat-labile toxin stimulates adenylate cyclase by ADP ribosylation of G protein; causes watery diarrhea. Heat-stable toxin stimulates guanylate cyclase.
(a) vibrio cholerae (b) Bordetella pertussis (c) E. coli
-?-(b) Bordetella pertussis Stimulates adenylate cyclase by ADP ribosylation; causes whooping cough; inhibits chemokine receptor, causing lymphocytosis.
(a) vibrio cholerae (b) Bordetella pertussis (c) E. coli
| T | -?-Treponema | too thin to be visualized |
| R | -?-Rickettsia | intracellular parasite |
| M | -?-Mycobacteria | high-lipid-content cell wall requires acid-fast stain |
| M | -?-Mycoplasma | no cell wall |
| Lp | -?-Legionella pneumophila | primarily intracellular |
| C | -?-Chlamydia | intracellular parasite |
| -?-S. aureus | Produces a yellow pigment |
| -?-Psudomonas aeruginosa | Produces a blue-green pigment |
| -?-Serratia marcescens | Produces a red pigment |
-?-Streptococcus pneumoniae, -?-Neisseria meningitides, -?-N. gonorrhoeae, -?-Haemophilus influenzae
| -?-(c) H. influenzae | Chocolate agar with factors V (NAD) and X (hematin) |
| -?-(g) N. gonorrhoeae | Thayer-Martin (VCN) media |
| -?-(e) B. pertussis | Bordet-Gengou (potato) agar |
| -?-(d) C. diphtheriae | Tellurite plate, Loffler's medium, blood agar |
| -?-(a) M. Tuberculosis | Lowenstein-Jensen agar |
| -?-(f) Legionella pneumophia | Charcoal yeast extract agar buffered with increased iron & cysteine |
| -?-(b) Fungi | Sabouraud's agar |
| (a) M. Tuberculosis (b) Fung (c) H. influenzae (d) C. diphtheriae (e) B. pertussis (f) Legionella pneumophia (g) N. gonorrhoeae | |
| -?-(d) Ziehl-Neelsen | acid-fast bacteria |
| -?-(e) India ink | Cryptococcus neoformans |
| -?-(a) Congo red | Amyloid; apple-green birefringence in polarized light |
| -?-(b) Giemsa's | Borrelia, Plasmodium, trypanosomes, Chlamydia |
| -?-(c) PAS (periodic acid Schiff) | Stains glycogen, mucopolysaccharides; used to diagnose Whipple's disease |
| (a) Congo red (b) Giemsa's (c) PAS (periodic acid Schiff) (d) Ziehl-Neelsen (e) India ink | |