Bacterial Growth

Question 1

What are Pilli

Answer 1

(hair) - used in adhesion, can be antiphagocytic
Oral bacteria use them to stick to teeth

Question 2

How do bacteria multiply

Answer 2

Binary fission (exponential growth)

Question 3

If a bacteria’s doubling time is 30 mins how many are present after 10 hours

Answer 3

1,048,576

Question 4

What is facultative bacteria

Answer 4

Can survive with or without oxygen

Question 5

What are capniphilic bacteria

Answer 5

Survive on CO2

Question 6

What are microaerophillic bacteria

Answer 6

Require small amounts of oxygen

Question 7

What are the stages of a bacterial growth graph

Answer 7

Lag phase
Logarithmic phase
Stationary phase
Death

Question 8

What are the pharmacodynamics of antibiotics

Answer 8

How different classes of antibiotics interact with bacteria
-some are conc dependent (metranidazole)
-some only require doses to be above the inhibitory conc of the bacteria

Question 9

What makes it non-selective blood agar

Answer 9

Will grow many different bacteria
-Helps provide a broad overview

Question 10

Why is selective used

Answer 10

Can refine diagnoses by selecting for a particular pathogen
Will only grow some types

Question 11

What colour does S.aureas appear on mannitol salt agar

Answer 11

Yellow (ferments mannitol)

Question 12

What colour does S. epidermidis appear on mannitol salt agar

Answer 12

Pink

Question 13

How can gram positive and negative cells be distinguished

Answer 13

Gram positive retain the dye complex - appear blue black

Question 14

Why do gram positive bacteria stain blue/black

Answer 14

Thick peptidoglycan sticks to stain

Question 15

What are the differences between gram + and gram - cells

Answer 15

Negative
-thin peptidoglycan layer in (periplasmic space) cell wall
-purple stain cannot attach

Question 16

What are exotoxins

Answer 16

Proteins produced inside the cell and excreted outwards (produced by both bacteria)

Question 17

What are endotoxins

Answer 17

Fragments of the bacterial cell walls (gram negative)

Question 18

What is another name for endotoxins

Answer 18

Lipopolysaccharide

Question 19

Why is a gram stain useful

Answer 19

Helps provide a provisional diagnosis
Helps guide an empirical antibiotic treatment

Question 20

What microorganism causes dental caries

Answer 20

Streptococcus mutans

Question 21

What bacteria is staphylococcus aureus

Answer 21

Gram postive cocci

Question 22

What microorganism causes meningitis

Answer 22

Neisseria meningitidis
-Gram negative cocci

Question 23

What micro-organism causes periodontal disease

Answer 23

Prevotella intermedia
Gram negative bacilli

Question 24

What conditions does the bacteria which causes periodontal disease thrive in

Answer 24

Anaerobic conditions (black pigmentum anaerobes)

Question 25

What microorganisms are unidentifiable on gram stains

Answer 25

Mycobacterium

Question 26

Where does the name for staphylococcus aureus come from

Answer 26

Staphylos - grapes Coccus - round Aureus - golden (usually more dull grey)

Question 27

What are the subclassifications of S. aureus

Answer 27

Methicillin sensitive Methicillin resistant (MRSA)

Question 28

What is colonization

Answer 28

The presence of micro-organism (s) in or on a host, with growth and muliplication, but without any overt clinical expression (infection) at the time the micro-organism is isolated

Question 29

What sites are frequently colonised by S. aureus

Answer 29

Nose throat Axilla (armpit) Groin

Question 30

What are the carrier states

Answer 30

Persistent carriers Intermittent Non-carriers

Question 31

What are the risk factors for S. aureus colonisation

Answer 31

Antibiotic use Diabetes, Renal dialysis, HIV, Obesity Hospitalisation Colonised partner

Question 32

What is the definition of infection

Answer 32

Invasion of the body by pathogenic microbes and the reaction of the tissues to their presence and to the toxins generated by them Signs & Symptoms: -Redness, swelling, pain, loss of function

Question 33

What are the types of infections produced by S. aureus

Answer 33

Pyogenic (pus producing) Toxin mediated

Question 34

What pyogenic infections does S. aureus cause

Answer 34

Boils Abscesses Mastitis Endocarditis Impetigo

Question 35

What toxin mediated infections can S. aureus cause

Answer 35

Toxic shock syndrome Food poisoning PVL

Question 36

What oral infections are caused by S. aureus

Answer 36

Angular cheilitis (around mouth) Parotitis (parotid gland) Osteomyelitis Staphylococcal mucositis

Question 37

What is salt used for on mannitol agar

Answer 37

Supresses the growth of many microorganisms -Makes it selective

Question 38

How does the agar turn yellow when the mannitol is fermented by S. aureus

Answer 38

pH indicator present