Taxonomy, Structure, Virulence Factors, and Toxins Flashcards by Diego Camacho

What are the components of the bacterial cell envelope?

Inner cell membrane
Cell wall (peptidoglycan layer)
Outer cell membrane
Cell capsule

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What color are gram + organisms? What color are gram - organisms?

Gram + stain blue

Gram - stain red

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What enzyme is responsible for formation of the peptidoglycan cell wall? What class of drugs inhibit this enzyme?

Transpeptidase (penicillin binding protein)

Penicillins

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What are key antigenic determinants for gram + / gram - bacteria?

Gram + : Lipoteichoic acid

Gram - : O-antigen

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What is the major component of the outer cell membrane of gram - bacteria?

LPS

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What component of LPS is an endotoxin?

Lipid A

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What are the 5 major shapes of bacteria?

Cocci
Rods
Branching filamentous
Pleomorphic
Spiral forms

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Classically, there are 7 gram + bugs that cause disease. Which of these are rods and which are cocci?

4 rods- Bacillus, Clostridium, Corynebacterium, Listeria

3 cocci- Streptococcus, Enterococcus, Staphylococcous

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Of the gram - organisms there are only 2 genera that are cocci; moreover, both are diplococci. What are these two genera?

Neisseria

Moraxella

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What bacterial genus does not have a cell wall and only has a cell membrane?

Mycoplasma

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What bacterial genus is acid fast?

Mycobacterium

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Bacteria have 70s ribosomes. What are the ribosomal subunits? What drug class targets each subunit?

30s- Tetracyclines, Aminoglycosides

50s- Macrolides, Chloramphenicol, Clindamycin, Linezolid

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What 2 genera of bacteria form endospores?

Bacillus

Clostridium

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Define exotoxin.

Toxin secreted by bacteria

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Define a bacterial neurotoxin.

Exotoxin that acts on nerves or motor end plates

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Define enterotoxin.

Exotoxin that acts on GI tract to cause diarrhea.

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Contrast infectious diarrhea and food poisoning.

Infectious diarrhea: bacteria colonize GI tract and release enterotoxin
Food poisoning: bacteria grow in food and release enterotoxin in the food

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List the bacteria that produce exotoxins that increased intracellular levels of cAMP.

Cholera (Vibrio cholera; Cholera toxin)- Permanent activation of Gs
Anthrax (Bacillus anthracis; Edema toxin)- Mimics AC
Montezuma’s revenge (ETEC; Heat labile toxin)- Permanent activation of Gs
Pertussis (Bordatella pertussis; Pertussis toxin)- Disables Gi

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What is glycocalyx?

Loose network of polysaccharides that mediates adherence to surfaces.

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What gram negative rods are enteric bacteria?

Bacteroides
Campylobacter
E. coli
Enterobacter
Helicobacter
Klebsiella
Proteus
Pseudomonas
Salmonella
Serratia
Shigella
Vibrio
Yersinia

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What gram negative rods cause respiratory illness?

Bordetella
Haemophilus
Legionella

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What gram negative rods are zoonotic?

Bartonella
Brucella
Francisella
Pasteurella

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What gram + bacteria are branching filamentous?

Actinomyces

Nocardia

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What gram negative bacteria are spirochetes?

Borrelia
Leptospira
Treponema

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What organisms stain with Giemsa?

``` Chlamydia Rickettsia Borrelia Trypanosomes Plasmodium ```

PAS (periodic acid-Schiff) stains glycogen. What disease is it used to diagnose?

Whipple disease- T. whipplei

What organisms is silver stain used for?

Fungi Leginoella Helicobacter pylori

What cytokines are induced by lipoteichoic acid?

TNF IL-1 IL-6

What is the location of gram negative β-lactamase?

Periplasmic space

What media is used to isolate H. influenzae?

Chocolate agar

What media is used to isolate Neisseria?

Thayer-Martin agar

What media is used to isolate C. diptheriae?

Tellurite agar

What agar is used to isolate M. tuberculosis?

Lowenstein-Jensen agar

What media is used to isolate M. pneumoniae?

Eaton agar

Lactose-fermenting enterics can be isolated using what agar?

MacConkey

What media is used to isolate E. coli?

Eosin-methylene blue (EMB) agar

What media is used to isolate fungi?

Sabouraud agar

TNF-α inhibitors can cause reactivation of what bacterial pathogen?

M. tuberculosis

Are aminoglyosides effective against anerobes?

No- require oxygen to enter the bacterial cell

What agar is used to isolate B. pertussis?

Bordet-Gengou agar

What bugs are obligate intracellular pathogens?

Chlamydia Coxiella Rickettsia

What bacteria are facultative intracellular pathogens?

``` Salmonella Neisseria Brucella Mycobacetrium Listeria Francisella Legionella Yersinia ```

The capsule of bacteria is a virulence factor that inhibits phagocytosis. How are these organisms cleared from the body?

Opsonized, then cleared by the spleen

What vaccines are given to asplenic individuals?

S. pneumoniae H. influenzae N. meningitidis

In addition to S. pneumoniae, H. influenzae, and N. meningitidis, what other bugs have capsules?

E. coli Klebsiella Salmonella Group B Strep (S. pyogenes)

A polysaccharide antigen alone cannot be presented to T cells; however, there are vaccines that can be given to prevent infection by encapsulated organisms. How do these vaccines work?

Polysaccharide + protein conjugate

What organisms produce urease?

``` Cryptococcus H. pylori Proteus Ureplasma Nocardia Klebsiella S. epidermidis S. saprophyticus ```

Individuals with chronic granulomatous disease are susceptible to infections with what type of organism?

Catalase positive organisms

What organisms produce pigment?

Actinomyces israelii- yellow sulfur granules S. aureus- yellow pigment Pseudomonas aeruginosa- blue-green pigment Serratia marcescens- red pigment

Detail the mechanism of action of the virulence factor Protein A. What bacteria expresses this virulence factor?

Binds Fc region of IgG- prevents opsonization and phagocytosis Expressed by S. aureus

Detail the mechanism of action of the virulence factor IgA protease. What bacteria expresses this virulence factor?

Enzyme that cleaves IgA- facilitates colonization of respiratory mucosa S. pneumoniae Neisseria H. influensa

Detail the mechanism of action of the virulence factor M protein. What bacteria expresses this virulence factor?

Inhibits phagocytosis | S. pyogenes

What is the type 3 secretion system?

Injectisome- protein appendage that facilitates delivery of toxins into host cells

What bacteria produce exotoxins that inhibit protein synthesis?

Corynebacterium- diptheria toxin Pseudomonas- Exotoxin A Shigella- Shiga toxin E. coli (EHEC)- Shiga like toxin

Diptheria toxin and Exotoxin A have the same mechanism of action. What is this mechanism?

Inactivate elongation factor (EF-2)

Shiga toxin and Shiga-like toxin have the same mechanism of action. What is this mechanism?

Inactivates 60s ribosome- removes adenine from rRNA

What bacteria produce exotoxins that increase fluid secretion?

E. coli (ETEC)- Heat labile toxin and heat stable toxin Bacillus anthracis- Edema toxin V. cholerae- Cholera toxin

What is the mechanism of action of heat labile toxin? What is the mechanism of action of heat stable toxin?

Heat labile toxin- increases cAMP which leads to chloride secretion in gut Heat stable toxin- increases cGMP which decreases resorption of NaCl/water in gut

What is the mechanism of action of cholera toxin?

Permanently activates Gs- leads to Cl secretion in gut

What is the mechanism of action of pertussis toxin?

Disables Gi- increases cAMP which impairs phagocytosis

What bacteria produce toxins that inhibit release of neurotransmitters?

C. tetani- tetanospasmin | C. botulinum- botulinum toxin

What is the mechanism of action of tetanospasmin and botulinum toxin?

Proteases that cleave SNARE proteins

What cells does tetanospasmin effect?

Renshaw cells in spinal cord- prevent release of GABA

What cells does botulinum toxin effect?

End plate motor neurons- inhibit release of ACh

What bacteria produce toxins that lyse cell membranes?

Clostridium perfringens- Alpha toxin | S. pyogenes- Streptolysin O

What bacteria produce superantigens that cause toxic shock?

S. aureus- TSST-1 | S. pyogenes- Exotoxin A

What is the mechanism of action of superantigens?

Bind to MHCII and TCR to cause release of IL-1, IL-2, IFN-γ, and TNF-α

What is bacterial transformation? What enzyme can inhibit this processes?

Ability of bacteria to take up naked DNA from the environment. Inhibited by deoxyribonuclease

What is bacterial transposition?

Segment of DNA moves from one location to another (plasmid to chromosome and vice versa)

What 5 bacterial toxins are encoded by a lysogenic phage?

``` Shiga toxin Botulinum toxin Cholera toxin Diptheria toxin Erythrogenic toxin ```

What bacterial genus has gram + cocci that are catalase positive?

Staphylococcous

What bacterial genus has gram + cocci that are catalase negative?

Streptococcus

What species of Staph are coagulase negative?

S. epidermidis | S. saprophyticus

What gram + branching filament organism is acid fast?

Nocardia

Taxonomy, Structure, Virulence Factors, and Toxins Flashcards

(74 cards)