Lab Practical 3

Question 1

Spore forming G+ bacilli

Answer 1

Bacillus
Clostridium, clostridioides (anaerobes)

Question 2

Catalase positive G+ bacilli

Answer 2

Bacillus, corynebacterium, listeria

Question 3

Acid fast stain mechanism

Answer 3

Ziehl neelsen - hot, heat makes dye penetrate cell wall
Kinyoun - cold, phenol dissolves lipid material and penetrates

Method: carbolfuchin stain, then counterstain

Appearance: bacteria red, other stuff blue

Question 4

Modified acid fast stain for who? How does it work?

Answer 4

Aerobic actinomycetes
- Weak acid decolorizer instead of 3% HCL for mycobacteria

Question 5

Which G+ rod grows on SBA and CHOC?

Answer 5

All Bacillus, Listeria, most corynebacterium but some don’t grow on CHOC like jeikeum
Nocardia

Question 6

Corynebacterium diphtheriae special media is called and list properties

Answer 6

Cystine tellurite agar/modified tinsdale agar
- tellurite inhibits other growth and can reduce cystine
- positive for diphtheria: gray-black colonies

Question 7

What special nutritional requirments do anaerobes have

Answer 7

Vitamin K and hemin

Question 8

List the three main anaerobes

Answer 8

Clostridium, clostridioides, actinomyces

Question 9

G+ rods and growth timing

Answer 9

• Bacillus: within 24 hours
• Listeria, Erysipelothrix, coryneform: within 48 hours
• Nocardia and aerobic actinomycetes: within 3-6 days and up to 4 weeks

Question 10

G+ bacilli growth conditions

Answer 10

• Bacillus: 35-37 or in 5% CO2
• Listeria, erysipelothrix, coryneform: 35-37 air or 5% CO2
• Nocardia, aerobic actinomycetes: 37 C

Question 11

Mycobacteria growth requirements

Answer 11

Strict aerobes, slow growing
30-45 C

Question 12

Bacillus anthracis vs other bacillus on SBA

Answer 12

B. anthracis is non hemolytic and has filamentous “medusa head” colony growths, non motile

Question 12

Elek test for what and how does it work

Answer 12

Immunodiffusion, tests for toxin of diphtheria

Question 13

Listeria monocytogenes key characteristics

Hemolysis, motility, bile esculin, camp

Answer 13

Hemolysis: narrow beta
Motility: umbrella or tumbling at 25 C
Bile esculin: +
CAMP: +

Question 14

Specimen collection for anaerobes

Answer 14

• Abscesses
• Aspirates
• Fluids
• Tissue

Swabs are discouraged

Question 15

Gram stain of Clostridium and clostridioides

Answer 15

G+, spore forming rods
C. perfringens can be box car shaped

Question 16

Gram stain of Actinomyces

Answer 16

G+, non spire forming, branching bacilli

Question 17

Medium for bacteroides fragilis

Answer 17

BBE agar
Bacteroides bile esculin

Question 18

Medium for bacteroides and prevotella

Answer 18

KVLB agar
Kanamycin-vancomycin laked blood agar

Question 19

Medium for anaerobic bacteria

Answer 19

PEA agar
Phenylethyl alcohol agar

Question 20

Clostridioides difficile medium

Answer 20

Cycloserine cefoxitin fructose CCFA agar

Question 21

Gram stain for corynebacterium

Answer 21

V or L shape,clubs, palisades, G+ pleomorphic

Question 22

List the 4 Misc. gram neg rods

Answer 22

Acinetobacter baumanni
Burkholderia cepacia
Stenotrophomonas maltophilia
Pseudomonas aeruginosa

Question 23

Misc G- rods that are oxidase +

Answer 23

Burkholderia cepacia and pseudomonas aeruginosa

Question 24

Only misc G- rod that is non motile

Answer 24

Acinetobacter baumanni

Question 25

Campylobacter special medium

Answer 25

Campylobacter blood agar CAMPY-BA. selective enriched for C. jejuni from stool

Question 26

Special medium for Vibrio

Answer 26

TCBS Thiosulfate citrate bile salt sucrose agar

Question 27

O/F medium mechanism

Answer 27

Two tubes, one aerobic and one anaerobic - turns fully yellow if fermenter - turns slightly yellow if oxidizer - oil layer for true anaerobic conditions

Question 28

Pigment production on MH medium

Answer 28

Pseudomonas aeuroginosa

Question 29

Vibrio special growth requirements

Answer 29

Increased sale for all EXCEPT for V. cholerae

Question 30

Who has darting motility

Answer 30

Campylobacter

Question 31

O/129 disk susceptibility

Answer 31

Vibrio is sus

Question 32

Campylobacter special gram stain appearance

Answer 32

S shape, sea gull wings

Question 33

Burkholderia mallei vs pseudomallaei test differentiation

Answer 33

**Mallei oxidase:** -, variable, non motile **Pseudomallei oxidase:** +, motile

Question 34

Key points for lower respir tract diagnosis and collection

Answer 34

First morning sputum is the best

Question 35

Key points for diagnosis upper respir. tract

Answer 35

- swabs are NOT for otitis media or sinitus - Aspirates are better - Throat specimens use thorough swabs

Question 36

CNS diagnostic collection

Answer 36

- Before antimicrobial therapy - Do not fridge CSF - 2-4 blood cultures if bacterial meninigitis suspected

Question 37

Clostridium difficile stool collection requirement

Answer 37

DIARRHEA WET SLOPPY LOOSE STOOL ONLY

Question 38

UTI diagnostic collection key points

Answer 38

- If 3+ bacteria, suspect contamination

Question 39

When do you need to work up a colony on a stool MAC

Answer 39

Clear colorless, rule out shigella and salmonella

Question 40

When do you need to work up a colony on stool SMAC

Answer 40

Clear colorless, rule out O157

Question 41

When do you need to work up a colony on stool HE

Answer 41

Blue/blue green (w or w/o black) Rule out salmonella and shigella

Question 42

Urine specimen colony count

Answer 42

1 microliter loop: multiply by x1000 10 microliter loop: multiply by x100

Question 43

Direct smear report numbers

Answer 43

10x objective **WBCs** - 4+, >25 - 3+, 11-25 - 2+, 3-10 - 1+, <3 **SEC** - >10 or <=10 **Bacteria under oil** - 4+, >10 - Report gram and morph

Question 44

Oxacillin/methicillin resistant staphylococci ## Footnote what about it, what to do next

Answer 44

- Possess mecA gene - Report as resistant to all beta-lactams - Test with cefoxitin to predict mecA better