MICROBIOLOGY & IMMUNOLOGY

MICRO: Clinical Bacteriology

Click on the -?- to reveal/hide the answer.

Bacterial Structures:
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
Main Features of Exotoxins & Endotoxins:
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

Name the bugs that do not Gram stain well:
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
The pathogenic N -?-Neisseria species are differentiated on the basis of sugar fermentation.
Pigment-producing bacteria:
-?-S. aureus Produces a yellow pigment
-?-Psudomonas aeruginosa Produces a blue-green pigment
-?-Serratia marcescens Produces a red pigment
lgA proteases allow 4 organisms to colonize mucosal surfaces. Name the four.
-?-Streptococcus pneumoniae, -?-Neisseria meningitides, -?-N. gonorrhoeae, -?-Haemophilus influenzae
Match bug with special culture requirements:
-?-(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
Match the stains:
-?-(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
In conjugation, the DNA is transferred from one bacterium to -?-another: the type of cells involved is -?-prokaryotic.
In transduction, DNA is transferred by a -?-virus from one cell to another; the type of cells involved is -?-prokaryotic.
In transformation, purified -?-DNA is taken up by a cell; the types of cell involved are -?-prokaryotic or -?-eukaryotic.
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