Basic Bacteriology

Question 1

targets of antibiotics that prokaryotes have that eukaryotes don’t

Answer 1

ribosomes & cell wall

Question 2

pathogen associated molecular patterns

Answer 2

highly conserved motifs in the cell wall of bacteria, recognized by Pathogen Recognition Receptors
*can be targeted with antibiotics

Question 3

bacterial cell wall

Answer 3

*composed largely of NAG and NAM sugars, connected by beta-glycosidic bonds
*CROSS-LINKED by amino acids (L and D symmetry) to form SHEETS of peptidoglycan layers

Question 4

gram positive cell wall

Answer 4

*THICK peptidoglycan layer above cytoplasmic membrane
-traps and binds gram stain (stain PURPLE)
-small molecules can diffuse
*rich in techoic and lipotechoic acid, vital to cell survival

Question 5

techoic acid & lipotechoic acid

Answer 5

unique to gram POSITIVE cell wall
-help to anchor the cell wall

Question 6

gram negative cell wall

Answer 6

*THIN
*3 layers:
1. thin outer membrane, rich in LPS and porin molecules
2. periplasmic space (a pool for enzymes such as beta-lactamases)
3. cytoplasmic membrane

Question 7

periplasmic space

Answer 7

*unique to gram negative
*contains thin peptidoglycan and a pool for enzymes (like beta lactamases)

Question 8

LPS in the gram neg outer membrane

Answer 8

3 covalently linked components:
1. outer carbohydrate chains of 1-50 oligosaccharide units
2. core polysaccharide that is water soluble
3. lipid A (ENDOTOXIN) - stimulates TLR4 receptors when bacteria lyse)

Question 9

gram staining exceptions

Answer 9

*acid-fast organisms (mycobacterium) have lipid-rich membrane containing mycolic acid
*organisms that lack a cell wall
*some spirochetes are too small
*intracellular pathogens

Question 10

classification of bacteria based on shape/morphology

Answer 10

-coccus
-coccobacillus
-vibrio (comma-shaped)
-bacillus (rod)
-spirochetes

Question 11

obligate aerobes

Answer 11

-need oxygen
-use glycolysis, Krebs cycle, and ETC
-have enzymes to handle ROS

Question 12

facultative anaerobes

Answer 12

-prefer oxygen, but can use anaerobic fermentation as an alternative energy source
-have enzymes to handle ROS

Question 13

obligate ANaerobes

Answer 13

-lack enzymes needed to handle oxygen
-use anaerobic fermentation that produces gas such as gangrene

Question 14

superoxide dismutase

Answer 14

dispose superoxide radical to hydrogen peroxide

Question 15

catalase

Answer 15

dispose hydrogen peroxide to water

Question 16

catalase test: strep vs. staph

Answer 16

*staph is catalase (+)
*strep is catalase (-)

Question 17

enzyme deficiency in chronic granulomatous disease (CGD)

Answer 17

*lack of NADPH oxidase
*patients susceptible to catalase (+) organisms

Question 18

spores

Answer 18

*ONLY MADE BY GRAM POS
-metabolically dormant
-thick protective covering composed of multiple membranes, peptidoglycan mesh, keratin-like protein, and outer exporium
-resistant to heat, cold, drying, and chemical agents

Question 19

examples of spore-forming species

Answer 19

Bacillus and Clostridium
*ONLY GRAM +

Question 20

obligate intracellular organisms

Answer 20

-cannot live outside host
-steal ATP

Question 21

facultative intracellular organisms

Answer 21

-invade host and resist lysosome when it is advantageous
-evade host defenses
-ex: listeria monocytogenes

Question 22

coagulase

Answer 22

*converts fibrinogen to fibrin (to cause coagulation)
*bacteria use clotting to evade host immune defenses
*often used to differentiate types of Staph
*cloudy/clot at the bottom = positive

Question 23

urease

Answer 23

*converts urea to ammonia and CO2, raising pH
*organisms grown in buffered broth with pH indicators as a test
*PINK = POSITIVE; yellow = negative

Question 24

virulence factors

Answer 24

-molecules and structures that enhance bacterial effectiveness
-improve entry into host and formation of colonies
-aid in host immune system evasion or immunosuppression
-assist bacteria in acquiring nutrients

Question 25

examples of important virulence factors

Answer 25

-capsule
-exotoxins
-protein A
-IgA protease
-M protein

Question 26

virulence factor: capsule

Answer 26

-protect against phagocytosis
-polysaccharide outer layer

Question 27

virulence factor: exotoxins

Answer 27

-disrupt cellular functions of host cell or allow tissue evasion
-usually proteins
-made and RELEASED by bacterium

Question 28

virulence factor: protein A

Answer 28

-binds Fc region of IgG to prevent opsonization

Question 29

virulence factor: IgA protease

Answer 29

-cleaves IgA and allows pathogen to enter respiratory tract
-protein enzyme

Question 30

virulence factor: M protein

Answer 30

-resembles human cellular protein (mimicry) to prevent phagocytosis
-expressed by Strep known to cause rheumatic fever

Question 31

selective media

Answer 31

has additive (e.g. antibiotics) that inhibit the growth of non-desirable bacteria, but FAVORS bacteria of interest

Question 32

differential/indicator media

Answer 32

allows observable changes in media appearance based on bacterial growth; often pH based
-ex: MacConkey agar; citrate agar

Question 33

blood agar

Answer 33

contain sheep or horse blood to detect bacteria’s HEMOLYTIC ABILITY (allows bacteria to obtain iron)
*cooked at a lower temperature so that RBCs remain intact
*useful for diff kinds of Strep

Question 34

beta-hemolysis on blood agar

Answer 34

COMPLETE digestion of blood around a colony

Question 35

alpha-hemolysis on blood agar

Answer 35

PARTIAL lysis of RBCs with greenish-brown residual membranes

Question 36

gamma-hemolysis on blood agar

Answer 36

NO lysis of RBCs

Question 37

chocolate agar (selective media)

Answer 37

cooked blood agar, so that the RBCs are already lysed

Question 38

Kirby Bauer test

Answer 38

tests for antibiotic sensitivity
*larger rings of no growth mean that antibiotic is good against that bacteria