Microbiology

Question 1

Gram positive bacteria appear…

Answer 1

Blue from crystal violet stain

Question 2

Gram negative bacteria appear…

Answer 2

red by absorbing safranin stain

Question 3

7 classic disease-causing GP bugs

Answer 3

3 are cocci: streptococcus + enterococcus form strips of cocci. Staphylococcus forms clusters of cocci.
2 of 4 GP rods produce spores: bacillus and clostridium
Corynebacterium and listeria do not form spores

Question 4

Which gram negative bacteria is a cocci?

Answer 4

Neisseria is a diplococci (kissing coffee beans)

Question 5

What is the GN group of spiral shaped rods called? Example?

Answer 5

Spirochetes, treponema pallidum

Question 6

What classification do most GN fall under?

Answer 6

rods or pleomorphic

Question 7

Is mycobacteria GP or GN?

Answer 7

Weakly GP but stained much better with acid-fast stain

Question 8

How are spirochetes visualized?

Answer 8

darkfield microscopy. They are too small to be seen with the light microscope

Question 9

Are mycoplasma GN or GP?

Answer 9

Neither. They do not have a cell wall. They only have a simple cell membrane.

Question 10

Please name the GP cocci.

Answer 10

Streptococcus, enterococcus and staphylococcus

Question 11

Please name the GN cocci.

Answer 11

Neisseria

Question 12

Please name the GP rods (bacilli)

Answer 12

Corynebacterium, listeria, bacillus, clostridium

Question 13

Please name the GN rods (bacilli)

Answer 13

Enterics:

• Escherichia coli
• Shigella
• Salmonella
• Yersinia
• Klebsiella
• Proteus
• Enterobacter
• Serratia
• Vibrio
• Campylobacter
• Helicobacter
• Pseudomonas
• Bacteroides (anaerobic)

Others: Haemophylus, bordetella, legionella, Yersinia, Francisella, Brucella, Pasteurella, Gardnerella.

Question 14

Please name the GN spirochetes.

Answer 14

Treponema, Borrelia, Leptospira

Question 15

Please name the gram positives with branching filamentous growth.

Answer 15

Actinomyces (anaerobic)

Nocardia (partially acid-fast)

Question 16

Which bacteria is neither GP or GN and has no cell wall?

Answer 16

Mycoplasma

Question 17

Name two GN diplococci

Answer 17

N. meningitidis

N. gonorrhoeae

Question 18

Name the GN “coccoid” rods

Answer 18

Haemophilus influenzae
Pasteurella (animal bites)
Brucella (brucellosis)
Bordetella pertussis

Question 19

Name the GN rods that are lactose fermenters

Answer 19

Fast

• Klebsiella
• E. coli
• Enterobacter

Slow

• Citrobacter
• Serrate
• Others

Question 20

Name the GN rods that are lactose nonfermenters

Answer 20

Oxidase +
- Pseudomonas

Oxidase - 
Shigella
Salmonella
Proteus
Yersinia

Question 21

Name the gram positive cocci and their common sites of invasion.

Answer 21

Staphylococcus and streptococcus.
Staph inhabits skin and is likely to infect wounds, surgical sites, and indwelling catheters (infective endocarditis).
Strep can cause CAP, adult bacterial meningitis, strep throat, rheumatic fever.

Question 22

Name common anaerobes and their common sites of invasion.

Answer 22

Bactericides fragilis, Clostridium difficile, fusobacterium, C. botulinum and C tetani.
Anaerobes colonize the mouth, GI tract and skin. Infections develop when anaerobes penetrate poorly oxygenated tissues (diabetic foot) or tissues that are normally sterile (peritoneum)

Question 23

Name common gram negative pathogens and their common sites of invasion.

Answer 23

Enterics: Escherichia, Shigella, Salmonella, Klebsiella, Enterobacter, Serratia, Proteus.
Others: Haemophilus influenza, Neisseria, pseudomonas
Enterics are responsible for many UTIs and aspiration pneumonia. Neisseria = gonorrhea. N. meningitides + H. influenza = meningitis. H. influenzae can cause pneumonia. Pseudomonas can occur at any site, particularly in immunocompromised. Its sticky.

Question 24

What does vancomycin cover?

Answer 24

PCN-resistant/MRSA. Bacteriostatic against enterococcus. Oral: C. difficile

Question 25

What does bacitracin cover?

Answer 25

GPs infecting skin. Eye infections.

Question 26

What do the carbapenems cover?

Answer 26

Acinetobacter. Excellent coverage of most GPs and GNs and pseudomonas.

Question 27

What does aztreonam cover?

Answer 27

Excellent GN, including pseudomonas. No GP coverage.

Question 28

What does daptomycin cover?

Answer 28

Skin infections caused by S. aureus, MRSA, strep species, Vanco-sensitive enterococcus

Question 29

What does penicillin cover?

Answer 29

Narrow spectrum. Covers GP cocci, Neisseria, most mouth anaerobes. NOT effective against GN aerobes or B-lactamase-producing organisms.

Question 30

What does nafcillin, oxacillin and dicloxacillin cover?

Answer 30

Narrow spectrum. GP cocci (including B-lactamase producers), some streptococci. NOT effective against GN aerobes.

Question 31

What does ampicillin and amoxicillin cover?

Answer 31

Broad spectrum. Some GN and GP. DOC for listeria and enterococcus. NOT effective against B-lactamases.

Question 32

What does Augmentin (amox/clav) cover?

Answer 32

GN and GP and B-lactamases. DOC for moraxella and H influenzae.

Question 33

What does Ticaracillin cover?

Answer 33

Extended spectrum. GN infections (especially pseudomonas) and amino penicillin-resistant proteus infections. Less effective against GP penicillinases.

Question 34

What does piperacillin cover?

Answer 34

Extended spectrum. Good for Enterobacteria and GP cocci.

Question 35

What does piperacillin/tazobactam cover?

Answer 35

Extended spectrum. GN infections (especially pseudomonas) and amino penicillin-resistant proteus infections. Less effective against GP penicillinases. Similar to ticaracillin but covers piperacillin-resistant GNs and GP penicillinase-producers.

Question 36

Name the first generation cephalosporins and their activity.

Answer 36

Cephalexin, cefadroxil, cefazolin. GP cocci except enterococci and MRSA. Some GN enteric. Not effective against anaerobes.

Question 37

Name the second generation cephalosporins and their activity.

Answer 37

Cofactor, cefprozil, cefuroxime, cefoxitin, cefotetan. | GP cocci. Extended GN activity (H. flu, Enterobacter, Proteus, Neisseria sp.) NONE are effective against pseudomonas.

Question 38

Name the third generation cephalosporins and their activity.

Answer 38

Ceftriaxone, cefotaxime, deftazidime, ceftizoxime, cefepime, ceftibuten, cefpodoxime, cefdinir, cefditorin. GN bacilli. Pseudomonas best covered by ceftazidime, cefepime). GP cocci.