Stains And Culture Requirements

Question 0

These bugs do not Gram stain well (11):

Answer 0

Treponema, Leptospira - too thin to be visualized.
Mycobacteria- high lipid content–> acid fast staining better choice.
Mycoplasma, Ureaplasma - no cell wall
Legionella, Rickettsia, Chlamydia-(lacks classic peptidoglycan bec. of low muramic acid), Bartonella, Anaplasma, Erlichia

Question 1

What stain is better used for Legionella?

Answer 1

Silver stain

Question 2

Giemsa stain (6 organisms):

Answer 2

Chlamydia, Borrelia, Rickettsia, H. Pylori, Trypanosomes, Plasmodium.

Question 3

PAS (periodic acid-Shiff)- what does it stain, and it is used to diagnose what?

Answer 3

Stains glycogen, mucopolysaccharides; used to diagnose Whipple disease (Tropheryma whipplei).

Question 4

Ziehl-Neelsen (carbol fuchsin) is used to stain what?

Answer 4

Acid-fast bacteria (Nocardia, Mycobacteria), Protozoa (cryptosporidium oocysts).

Question 5

India ink is used to stain what organism?

Answer 5

Cryptococcus neoformans (mucicarmine can also be used to stain thick polysaccharide capsule red). (PCP)

Question 6

Silver stain is used for what organisms (4)?

Answer 6

Fungi (e.g. Coccidioides, Pneumocystis jirovecii), Legionella, Helicobacter pylori.

Question 7

Special culture requirements/ media for: H. Influenzae

Answer 7

Chocolate agar- factors V (NAD+) and X (hematin)

Question 8

Special culture requirements/media for: N. gonorrhoeae, N. meningitidis

Answer 8

Thayer-Martin agar: 
Vancomycin inhibits G+ organisms
Trimethoprim, Colistin inhibits G- organisms except Neissseria 
Nystatin (inhibits fungi)
(So favors growth of Neisseria)

Question 9

Special culture requirements/media for: B. pertussis

Answer 9

Bordet-Gengou agar (Bordet for Bordetella)

Regan-Lowe medium: potato extract, Charcoal, blood, and antibiotic

Question 10

Special culture requirements/media for: C. diphtheriae

Answer 10

Tellurite agar, Löffler medium

Question 11

Special culture requirements/media for: M. tuberculosis

Answer 11

Löwenstein-Jensen agar

Question 12

Special culture requirements/media for: M. pneumoniae

Answer 12

Eaton agar –> requires cholesterol

Question 13

Special culture requirements/media for: Lactose-fermenting enterics

Answer 13

MacConkey agar: fermentation produces acid, causing colonies to turn pink (pH indicator)

Question 14

Special culture requirements/media for: E. coli

Answer 14

Eosin-methylene blue (EMB) agar –> produces colonies with green metallic sheen

Question 15

Special culture requirements/media for: Legionella

Answer 15

Charcoal yeast extract agar buffered with cysteine and iron

Question 16

Special culture requirements/media for: Fungi

Answer 16

Sabouraud agar

Question 17

Special culture requirements/media for: Aerobes

Answer 17

O2 dependent system to generate ATP. Ex: Nocardia, Pseudomona aeruginosa, and Mycobacterium tuberculosis.

Question 18

Special culture requirements/media for: Anaerobes

Answer 18

Examples include Fusobacterium, Clostridium, Bacteroides, and Actinomyces. They lack catalase and or superoxide dismutase and are thus susceptible to oxidative damage. Generally foul smelling (short chain fatty acids), are difficult to culture, and produce gas in tissue (CO2 and H2).

Question 19

Gram (+) cocci that is catalase (+), coagulase (+), and can ferment Maltose.

Answer 19

S. Aureus