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Flashcards in Intro Deck (35)
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1

Why ID important

- Common
- Diagnosable
- Communicable
- High Morbidity and mortality
- Treatable
- Newly emerging Pathogens

2

what 3 variables affect development of infection/disease

-Host (behavior, susceptibility, age, sex genetics, immune status)
-Environment (geography, sanitation, crowding, pollutants, social, cultural, political, economic)
- Agent (pathogenicity, prevalence, ecologic niche, tissue tropism, mechanism of immune control)

3

how do you do a gram stain

- Heat slide (kill/bind bacteria)
- Crystal violet (binds peptidoglycan)
- Add iodine to bind CV to gram positive cell wall
- Rinse
- add Acetone alcohol: removes stain from gram negative cells
- Rinse
- Add Safranin (counterstain)

4

Gram Positive vs Gram Negative structure

Gram Positive: have Teichoic acid in cell wall as well as thick peptidoglycan layer

Gram Negative: Lack Teichoic acid but have outer membrane of Endotoxin/LPS with thin peptidoglycan wall

5

Peptidoglycan in gram positive vs gram negative

up to 90% of cell wall in gram positive and up to 5-20% in gram negative

6

Appearance of Gram positive vs negative on gram stain

positive-- dark purple, because they hold onto the crystal violet

Negative: due to thin peptidyglycan layer, the acetone alcohol removes the crystal violet from gram negative cells, which then stain pink with Safranin (counterstain)

7

Common Gram Positive cocci

Staph (clusters, pairs), Strep (pairs/chains)
(Catalase +/-)

8

common Gram negative cocci

- Neisseria- GC, meningococcus (CSF; lung)
- Moraxella - pneumonia
- Acinetobacter

9

Gram positive rod examples

Listeria, Clostridium

10

Gram negative rods

E. coli, Pseudomonas
(lactose-ferment +/-)

11

Non-staining organisms

+/- Legionella
Mycobacteria
Spirochetes
Rickettsia--intracellular
Mycoplasma
Chlamydia--intracellular

12

Encapsulated organisms

S. pneumoniae, H. influenzae, Neisseria meningitidis, K. pneumoniae, Bacillus anthracis

13

Multi-drug resistant organisms

M. tuberculosis, Ps. aeruginosa, methicillin-resistant Staph aureaus, Vancomycin-resistant enterococcus (VRE); S. pneumoniae

14

Bacteria producing superantigens

S. aureus, Group A Strep

15

Bacteria producing A-B toxins

V. cholerae, C. diphtheria

16

Bacteria producing "other toxins" (not A-B or superantigens)

Clostridium

17

Obligate intracellular organisms

Rickettsia, Chlamydia

18

Facultative intracelular organisms

Salmonella, Mycobacteria, Legionella

19

How to differentiate between gram negative rods

Lactose fermentation-- most significant GNR are lactose fermentors

Pseudomonas,

20

Lactose Fermenting GNR

E. coli
Klebsiella
Enterobater
Citrobacter
Arizona

21

Non-lactose fermenting GNR

Pseudomonas aeruginosa, Salmonella, Shigella, H influenza, Acinetobater

22

How to distinguish E coli from other lactose fermenting GNR

Indole-- E coli is the only one that is positive (except a few Klebsiella species)

23

Top lactose fermenting GNR

E. coli (flat), Klebsiela (mucoid), Enterobacter (mucoid)

24

sources of GNR

- intestine: appendix, diverticulitis, gallbladder (not Ps. aer.)
- urine: +WBC, +sxs
- lung/line (nosocomial)

25

Is staph coagulase positive/negative

Aureus = positive
- epidermidis (on skin) = negative
- saprophyticus (UTI)= negative
-lugdanensis = negative

26

Staphylococcus bacteremia

100% of S. aureus are significant;
>90% of coagulase negative staph are contaminants

27

Staph aureus

- carrier
- localized infection (boils, cellulitis)
- disseminated (blood, heart, joints, metastatic)

causes abscesses due to coagulase-- pus!

28

When do you think of coagulase negative staph

plastic/metal in body (epidermidis)

2nd leading cause of UTI in sexually active females (S. saprophyticus)

29

hemolysis status

- alpha - green - S. pneumo, S. viridans
-beta- clear (bad; Gr. A, B, C, G Strep; S. aureus)
- gamma (none)- usually include Strept. Milleri (pus)

30

Bad bugs

S. aureus (incl MRSA)
Strep pneumoniae
Group A Strept