Micro - Basic Bacteriology (Bacterial Identification)

Question 1

What are the Gram-positive versus Gram-negative cocci?

Answer 1

GRAM-POSITIVE COCCI = Staphylococcus, Streptococcus; GRAM-NEGATIVE (diplo)COCCI = Neisseria

Question 2

What are the Gram-positive rods (bacilli)? Which 2 have special qualities related to classification, and what are those qualities?

Answer 2

(1) Clostridium (2) Bacillus (3) Corynebacterium (4) Listeria (5) Mycobacterium (6) Gardnerella; Mycobacterium = acid-fast; Gardnerella = Gram variable

Question 3

What are the categories of Gram-negative rods, and what bacteria within each category?

Answer 3

ENTERICS - Klebsiella, E. coli, Enterobacter, Serratia, Shigella, Salmonella, Proteus, Yersinia, Helicobacter, Pseudomonas, Bacteroides, Vibrio, Campylobacter; RESPIRATORY - Haemophilus (pleomorphic), Legionella (silver), Bordetella; ZOONOTIC - Francisella, Brucella, Pasteurella, Bartonella

Question 4

Again, what are Gram-negative rods known for respiratory infections? Which 2 have special qualities related to classification, and what are those qualities?

Answer 4

Haemophilus (pleomorphic), Legionella (silver stain), Bordetella

Question 5

What are the branching filaments bacteria? Which is weakly acid fast? What kind of gram stain do both have?

Answer 5

(1) Actinomyces (2) Nocardia (weakly acid fast); Gram-positive

Question 6

What are the pleomorphic bacteria? How are they stained? Under what Gram stain are they (theoretically) classified?

Answer 6

Rickettsiae, Chlamydiae; Giemsa; Gram-negative

Question 7

What are the spiral bacteria? Which Gram stain are they? Which one can be stained well with Giemsa?

Answer 7

Spirochetes: Leptospira, Borrelia (Giemsa), Treponema; Gram-negative

Question 8

Which bacteria has no cell wall? What kind of Gram stain does it have?

Answer 8

Mycoplasma; Does not Gram stain

Question 9

What is unusual about the cell membrane/wall of Mycoplasma?

Answer 9

Contain sterols (in cell membrane) and have NO cell wall

Question 10

What is unusual about the cell membrane/wall of Mycobacteria?

Answer 10

Contain mycolic acid and high lipid content

Question 11

Which bugs do not Gram stain well, and why?

Answer 11

(1) Treponema (too thin to be visualized - use dark-field microscopy & fluorescent antibody staining) (2) Rickettsia (intracellular parasite) (3) Mycobacteria (high lipid content in cell wall detected by carbolfuchsin in acid-fast stain) (4) Mycoplasm (no cell wall) (5) Legionella pneumophila (primarily intracellular - use silver stain) (6) Chlamydia (intracellular parasite; lacks muramic acid in cell wall); Think: These Rascals May Microscopically Lack Color

Question 12

What is used to stain Treponema? What about Legionella pneumophila?

Answer 12

Dark-field microscopy and fluorescent antibody staining; Silver stain

Question 13

Which bugs work best with Giemsa stain?

Answer 13

Chlamydia, Borrelia, Rickettsiae, Trypanosomes, Plasmodium; Think: Certain Bugs Really Try my Patience

Question 14

What does PAS stand for? What kind of molecules does it stain? Which disease is it used to diagnose, and what microbe causes that?

Answer 14

Periodic acid-Schiff; Stains glycogen, mucopolysaccharides; Think: PASs the sugar; Used to diagnose Whipple’s disease (Tropheryma whipplei)

Question 15

What is another name for Ziehl-Neelsen stain? What kind of organisms does it stain? What are 2 specific examples?

Answer 15

Carbol fuchsin; Acid-fast organisms; Nocardia, Mycobacterium

Question 16

What organism is India ink known for staining? What is another staining method that can be used on this organism, and why/how?

Answer 16

Crytococcus neoformans; Mucicarmine can also be used to stain thick polysaccharide capsule red

Question 17

What 3 organisms is Silver stain known for staining?

Answer 17

(1) Fungi (e.g., Pneumocystis) (2) Legionella (3) Helicobacter pylori

Question 18

What media is used for isolation of H. influenzae? Include names of specific factors in this agar.

Answer 18

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

Question 19

What media is used for isolation of N. gonorrhoeae and/or N. meningitidis? Include specific components of this agar and their purposes.

Answer 19

Thayer-Martin (or VPN) media - Vancomycin (inhibits gram-positive organism), Polymyxin (inhibits gram-negative organisms except Neisseria), and Nystatin (inhibits fungi); Think: “To connect to Neisseria, please use your VPN client”

Question 20

What media is used for isolation of B. pertussis?

Answer 20

Bordet-Gengou (potato) agar; Think: Bordet for Bordetella

Question 21

What media is/are used for isolation of C. diphtheriae?

Answer 21

(1) Tellurite plate (2) Loffler’s media

Question 22

What media is used for isolation of M. tuberculosis?

Answer 22

Lowenstein-Jensen agar

Question 23

What media is used for isolation of M. pneumoniae? What is required for their growth?

Answer 23

Eaton’s agar, requires cholesterol

Question 24

What media is used for isolation of Lactose-fermenting enterics? How are they distinguished in this media?

Answer 24

Pink colonies on MacConkey’s agar (fermentation produces acid, turning colony pink colony;

Question 25

What media is used for isolation of E. coli? How does it appear on this media?

Answer 25

(In addition to MacConkey’s agar) E. Coli is also grown on eosin-methylene blue (EMB) agar as colonies with green metallic sheen

Question 26

What media is used for isolation of Legionella? Include the specific components in this agar.

Answer 26

Charcoal yeast extract agar buffered with cysteine and iron

Question 27

What media is used for isolation of Fungi?

Answer 27

Sabouraud’s agar; Think: “SAB’s a FUN GUY!”