Intro to ID 2

Question 1

What is the visual difference between gram-positive and gram-negative bacteria?

Answer 1

• gram-positive bacteria appear purple under a microscope due to thick peptidoglycan cell wall
• gram-negative bacteria appear pink/red under a microscope due to thin peptidoglycan cell wall

Question 2

How do atypical bacteria stain?

Answer 2

Atypical bacteria do not stain using gram-stain

Question 3

How do acid-fast bacilli (AFB) stain?

Answer 3

AFB are resistant to acids/ethanol based decolorization procedures

Question 4

What is the morphology of most medically important gram-positive pathogens?

Answer 4

cocci

Question 5

What form do staphylococcus take?

gram positive

Answer 5

clusters

Question 6

What form do streptococci and enterococci take?

gram positive

Answer 6

Streptococci & enterococci appear in pairs or chains

Question 7

Which biochemistry tests help to further differentiate gram-positive bacteria?

Answer 7

• catalase test
• coagulase test

• Catalase catalyzes the conversion of hydrogen peroxide to water oxygen. When a colony is placed in H2O2, liberation of O2 as gas bubble can be seen.
• Coagulase acts with plasma factor to convert fibrinogen to a fibrin clot.

Question 8

What does the catalase production test differentiate between?

Answer 8

• staphylococci are catalase positive
• streptococci are catalase negative

Staph and strep are both gram-positive

Question 9

What does the coagulase test differentiate between?

Answer 9

The coagulase test is used to differentiate staphylococcus aureus from other, less pathogenic staphylococci (CoNS)

• s. aureus is coagulase (+)
• s. epidermis is coagulase (-)
• CoNS = coagulase negative staphylococcus

Question 10

Which biochemical test helps differentiate between the gram-positive pairs/chains?

Answer 10

Blood agar/hemolysis test

• alpha is partially hemolytic
• beta is completely hemolytic
• gamma is nonhemolytic

Question 11

Which gram-positive, catalase-negative bacteria display alpha-hemolysis?

Answer 11

• streptococcus pneumoniae
• viridans streptococci

oral flora

Question 12

Which gram-positive, catalase-negative bacteria display beta-hemolysis?

Answer 12

• streptococci pyogenes (Group A)
• streptococci agalactiae (Group B)

skin, pharynx, genitourinary

Question 13

Which gram-positive, catalase negative bacteria display gamma-hemolysis?

Answer 13

• enterococcus faecium
• enterococcus faecalis

gastrointestinal

Question 14

How are the gram-positive bacilli further differentiated?

Answer 14

1. anaerobic vs aerobic
2. spore forming vs non-spore forming

Question 15

List the gram-positive bacilli bacteria that are anaerobic:

Answer 15

• spore forming: clostridium spp, clostridioides difficile
• non-spore forming: cutibacterium, actinomyces

spp = species

Question 16

List the gram-positive bacilli bacteria that are aerobic:

Answer 16

• Spore forming: bacillus spp
• non-spore forming: corynebacterium, lactobacillus spp, listeria monocytogenes

Question 17

What is the morphology of gram-negative bacteria?

Answer 17

• mostly bacilli
• some cocci
• some coccobacilli

Question 18

List the gram-negative cocci pathogens:

Answer 18

• aerobic: neisseria spp, moraxella catarrhalis
• anaerobic: veillonella spp

Question 19

List the gram-negative coccobacilli:

Answer 19

haemophilus spp

aerobic

Question 20

How are gram-negative bacilli further differentiated?

Answer 20

• anaerobic
• aerobic, fastidious
• aerobic, oxidase (+), lactose fermenters
• aerobic, non-lactose fermenters
• aerobic enterobacterales, lactose fermenters
• aerobic enterobacterales, non-lactose fermenters

Question 21

List the gram-negative, anaerobic, bacilli:

Answer 21

• bacteriodes spp
• fusobacterium spp
• prevotella spp

Question 22

List the gram-negative, aerobic, bacilli, enterobacterales, lactose fermenting pathoges:

Answer 22

• citrobacter spp
• enterbacter spp
• e. coli
• klebsiella spp

CEEK

Question 23

List the gram-negative, aerobic, bacilli, enterobacterales, non-lactose fermenting pathogens:

Answer 23

• morganella morgnaii
• proteus spp
• providencia spp
• salmonella spp
• serratia marcescens
• shigella spp

Question 24

List the gram-negative aerobic bacilli that are oxidase-positive lactose fermenters:

Answer 24

• aeromonas hydrophila
• pasteurella multocida
• vibrio cholerae

Question 25

List the gram-negative aerobic bacilli that are non-lactose fermenters:

Answer 25

• pseudomonas spp
• acinetobacter spp
• alcaligenes spp
• burkholderia cepacia
• stenotrophomonas maltophilia

Question 26

List the gram-negative aerobic bacilli that are fastidious:

Answer 26

• campylobacter
• helicobacter
• bartonella
• haemophilus
• actinobacillus
• cardiobacterium
• eikenella
• kingella

Question 27

List the atypical bacteria:

Answer 27

• chlamydia pneumoniae
• chlamydia trachomatis
• legionella pneumonphila
• mycoplasm pneumoniae

Question 28

List the spirochetes:

Answer 28

• treponema pallidum (syphilis)
• borrelia burgdorferi (Lyme disease)

Question 29

What is the oxidase test helpful in differentiating?

Answer 29

• Oxidase test help distinguish between enteric vs non-enteric lactose fermenters

Question 30

Which pathogens are a part of the normal flora for skin?

Answer 30

• diptheroids (Corynebacterium spp)
• staphylococci
• streptococci
• cutibacterium acnews
• propionibacterium spp

Question 31

Which pathogens compose the oropharynx (upper) normal flora?

Answer 31

• haemophilus spp
• streptococci (viridans group)
• diptheroids
• neisseria spp
• oral anaerobes

Question 32

Which pathogens compose the normal flora for the GI tract?

Answer 32

• bacteroides spp
• enterobacterales
• enterococci
• fusobacterium spp
• peptostreptococcus spp
• clostridium spp
• lactobacillus

Question 33

Which pathogens compose the normal flora for the genital tract?

Answer 33

• corynebacterium spp
• enterobacterales
• lactobacillus spp
• mycoplasma spp
• staphylococci
• streptococci
• anaerobes
• candida spp