IC1

Question 1

lab diagnostics - culture medium - MacConkey agar

Answer 1

• contains bile salts
• for enteric gram -ve bacteria
• differentiate lactose fermenting and non-lactose fermenting gram -ve bacteria

Question 2

timeline from specimen collection to identification, culture, and susceptibility results

Answer 2

day 1: gram stain
day 2-3: culture bacteria
day 3-4: identify bacteria
day 3-5: Abx susceptibility testing (AST)

Question 3

bacterial identification & microscopic classification - macroscopic appearance

Answer 3

1) shape
2) size (diameter)
3) elevation (Side view)
4) margin of border/edge of colony
5) surface of colony (smooth, glistening, rough, dull)
6) opacity
7) colour of pigmentation
8) breakdown of blood cells in blood agar

• complete haemolysis: beta-haemolytic streptococcus
• partial haemolysis: alpha-haemolytic streptococcus
• no haemolysis: gamma-haemolytic streptococcus

Question 4

bacterial identification & microscopic classification - microscopic

Answer 4

• gram stain: +ve, -ve (pink cuz counterstain)
• cocci, rod, curved, spiral
• diplococci, cocci in cluster/chain

Question 5

bacterial identification & microscopic classification - growth environment

Answer 5

aerobic, anaerobic

Question 5

bacterial identification & microscopic classification - need for specific nutrients

Answer 5

1) fermenter: ability to ferment carb/sugar
2) non-fermenter

Question 6

bacterial identification & microscopic classification - produce specific enzyme

Answer 6

1) Catalase
2) coagulase
3) oxidase

Question 7

common bacteria pathogen & location - gram positive - MRSA, MSSA

Answer 7

skin, bone, joint, IV lines, blood stream, implants, heart valves, lungs

Question 8

common bacteria pathogen & location - gram positive - streptococcus (group A, B, C, G)

Answer 8

skin, bone, joint, bloodstream

Question 9

common bacteria pathogen & location - gram positive - streptococcus pneumoniae

Answer 9

brain, ENT, joint, bloodstream

Question 10

common bacteria pathogen & location - gram positive - enterococcus pneumoniae

Answer 10

brain, ENT, joint, bloodstream

Question 11

common bacteria pathogen & location - gram positive - enterococcus fecalis

Answer 11

bloodstream, heart valves, abdomen, GI, urinary tract

Question 12

common bacteria pathogen & location - gram positive - anaerobe

Answer 12

1) finegoldia magna: skin, mouth, upper repi tract
2) clostridiodes difficile: abdomen, GI

Question 13

common bacteria pathogen & location - gram negative - anaerobe

Answer 13

bacteroids fragilis: abdomen, GI

Question 14

common bacteria pathogen & location - gram negative - haemophilus influenzae

Answer 14

ENT, lungs

Question 15

common bacteria pathogen & location - gram negative - E.coli, Klebsiella sp, P. Mirabilis

Answer 15

abdomen, GI, urinary tract, blood stream, DM foot (community acquired)

Question 16

common bacteria pathogen & location - gram negative - ESBL-producing E. coli, Kleb

Answer 16

hospital acquired

Question 17

common bacteria pathogen & location - gram negative - enterobacter (AMP-C producing GNR)

Answer 17

abdomen, urinary tract, bloodstream, DM foot

Question 18

common bacteria pathogen & location - gram negative - pseudomonas aeruginosa

Answer 18

lung, urinary tract, bloodstream, device-related DM foot

Question 19

description of bacteria - staphylococcus aureus

Answer 19

• gram pos
• cocci
• aerobic
• catalase +ve
• clusters
• coagulase +ve

Question 20

description of bacteria - coagulase -ve staphylococcus

Answer 20

• gram pos
• cocci
• aerobic
• catalase +ve
• cluster
• coagulase -ve

Question 21

description of bacteria - enterococcus faecalis, enterococcus faecium

Answer 21

• gram pos
• cocci
• aerobic
• catalase -ve
• pairs/chains
• enterococci (Group D)

Question 22

description of bacteria - beta haemolytic streptococcus

Answer 22

• gram pos
• cocci
• aerobic
• catalase -ve
• pairs/chains
• streptococci

Question 23

description of bacteria - different types of beta haemolytic streptococcus and their groups

Answer 23

• streptococcus pyogenes: group A
• streptococcus agalactiae: group B
• streptococcus suis: group C
• streptococcus bocis: group D

Question 24

description of bacteria - types of viridians type streptococci

Answer 24

streptococcus anginosa streptococcus constellatus streptococcus intermedius streptococcus salivarius streptococcus sanguis

Question 25

description of bacteria - viridians type streptococci characteristics

Answer 25

- gram pos - cocci - aerobic - catalase -ve - streptococci - alpha haemolytic - optochin resistant

Question 26

description of bacteria - streptococcus pneumoniae

Answer 26

- gram pos - cocci - aerobic - catalase -ve - pairs/chains - streptococci - alpha haemolyic - optochin sensitive

Question 27

description of bacteria - neisseria gonorrhoeae

Answer 27

- gram neg - cocci/coccobacilli - strict anerobic growth - oxidase positive

Question 28

description of bacteria - acinetobacter spp.

Answer 28

- gram neg - cocci/coccobacilli - aerobic/facultative growth - oxidase negative

Question 29

description of bacteria - pseudomonas aeruginosa

Answer 29

- gram neg - rods - strict aerobic growth

Question 30

description of bacteria - bacteriodes spp.

Answer 30

- gram neg - rods - strict anaerobic growth

Question 31

description of bacteria - escherichia coli

Answer 31

- gram neg - rods - aerobic facultative growth - simple growth requirements - oxidase negative - lactose fermenters

Question 32

description of bacteria - all oxidase positive bacteria

Answer 32

neisseria gonorrhoeae (gram neg) pseudomonas aeruginosa (gram neg)

Question 33

description of bacteria - all oxidase negative bacteria

Answer 33

e. coli (Gram neg) acinetobacter spp. (gram neg)

Question 34

description of bacteria - coagulase positive bacteria

Answer 34

staph aureus (Gram pos)

Question 35

description of bacteria - coagulase negative bacteria

Answer 35

coagulase-negative staphylocci (Gram pos)

Question 36

description of bacteria - catalase positive bacteria

Answer 36

- staph aureus (gram pos) - coagulase-negative staphylococci (gram pos)

Question 37

description of bacteria - cocci/coccobacilli

Answer 37

neisseria gonorrhoeae (gram neg) acinetobacter spp (gram neg) staph aureus (gram pos) enterocci (gram pos) coagulase-negative staphylococci (gram pos) enterocci (gram pos) beta haemolytic streptococcus (gram pos) viridans type streptococci (Gram pos) streptococcus pneumoniae (gram pos)

Question 38

description of bacteria - rods

Answer 38

pseudomonas aeruginosa (gram neg) E. coli (Gram neg)

Question 39

factors affecting in vivo activity of antimicrobial

Answer 39

1) immune system 2) drug protein binding 3) ability of drug to reach infection site 4) drainage/removal of infected foci 5) drug interactions 6) some bacteria only express enzymes that inhibit antibiotic in vivo

Question 40

how does each types of antimicrobial susceptibility testing work

Answer 40

1) agar/broth dilution method - uses MIC 2) Kirby-Bauer disk diffusion method - agar plate swabbed w standardised conc of microorganism - filter paper disc containing set conc of Abx - Abx diffuse outwards - diameter of zone of inhibition correlated to antimicrobial activity 3) E-test - agar based w graduated Abx concentrations layered on plastic strip - MIC where growth intersect w plastic strip

Question 41

how to use MIC/zone of inhibition to predict therapeutic response

Answer 41

* utilises breakpoints - concentration that predicts susceptibility/resistance - interpret S, I, R 1) S: susceptibility/susceptibility dose dependent - likely therapeutic success - infection can be treated w dosage of antimicrobial agent recommended 2) I: intermediate - uncertain response - infection treated if drug physically concentrated or if high dose used - buffer zone that prevent small, uncontrolled, technical factors from causing major discrepanices 3) R: resistant - therapeutic failure - X inhibited by drug

Question 42

what is antibiogram and its uses

Answer 42

- cumulative susceptibility results - antimicrobial susceptibility of common bacterial isolates collected in a hospital/institution - uses: 1) assess local susceptibility rate 2) monitor resistance over time 3) guide selection of antibiotic treatment (empiric therapy) when culture & susceptibility results X available

Question 43

how does antimicrobial resistance occur

Answer 43

mutation/gene transfer → selection pressure → drug resistant bacteria multiply & thrive