Oral Surgery

Question 1

What are the features of Gram Negative bacteria

Answer 1

1. Has an inner and outer membrane (2 membranes)
2. Releases endotoxins (LPS) + exotoxins
3. Stains RED

Question 2

What are features of Gram Positive bacteria

Answer 2

1. No outer membrane but is surrounded by layers of peptidoglycan which is thicker than that of gram negative
2. Contains teichoic acid + lipteichoic acid in cell wall
3. Releases exotoxins only
4. Stains purple

Question 3

Why does gram negative stain pink

Answer 3

organic solvent used disrupts membrane and stain is washed out of cell

Question 4

Why does gram positive stain violet

Answer 4

as it retains the fixed violet dye within the cell

Question 5

What is an example of a gram positive cocci

Answer 5

s. anginosus
streptococcus mutans (facultative)

Question 6

What is an example of a gram negative cocci

Answer 6

veillonella species

Question 7

What is an example of a gram positive bacilli

Answer 7

actinomyces israelii (anaerobic)
clostridium difficile (anaerobic)

Question 8

What is an example of a gram negative bacilli

Answer 8

prevotella intermedia

Question 9

What does aerobic growth conditions mean

Answer 9

requires oxygen

Question 10

What does capnophilic growth conditions mean

Answer 10

requires carbon dioxide

Question 11

What does facultative growth conditions mean

Answer 11

can survive with/without oxygen

Question 12

What does strictly anaerobic growth conditions mean

Answer 12

requires no oxygen, oxygen can be toxic. Metronidazole is the only antibiotic that works on these

Question 13

What is antimicrobial resistance

Answer 13

occurs when microorganisms change in ways that render the medications used to cure the infections they cause ineffective

Question 14

What are the 2 main types of resistance

Answer 14

intrinsic
acquired

Question 15

What is intrinsic resistance

Answer 15

bacterial species is naturally resistant to a certain antibiotic/family of antibiotics without the need for mutation/gain of further genes

Question 16

What are the 2 types of acquired resistance

Answer 16

mutation
acquisition of new DNA

Question 17

How does mutations result in resistance

Answer 17

• E.g single, spontaneous chromosomal mutation in one bacterial cell which results in synthesis of an altered protein
• If this protein is a target site for a particular antibiotic then the antimicrobial effectiveness will be severely compromised in mutant cells giving them a selective advantage

Question 18

What are the 3 methods that a bacterium can acquire new DNA

Answer 18

Transformation, transduction, conjugation

Question 19

What are the 2 mechanisms of resistance

Answer 19

altered target
enzymatic deactivation

Question 20

Describe altered target mechanism of resistance and give an example

Answer 20

Target enzyme may change sufficiently e.g by mutation to cause a lower affinity for the drug

Additional target enzyme that is resistant to the drug may be produced

E.g is penicillin resistance due to modified penicillin binding proteins

Question 21

What is the enzymatic deactivation mechanism of resistance

Answer 21

 Production of enzymes that inactivate the antibacterial agent
 E.g prevotella and fusobacteriam species produce beta-lactamases which inactivate penicillins
 Carbapenem antibiotics protect from betalactamases

Question 22

What are the 2 types of antibiotic testing

Answer 22

diffusion and dilution

Question 23

What is the minimum inhibitory concentration

Answer 23

this is the lowest concentration of a chemical, usually a drug which prevents visible growth of a bacteria or bacteria

Question 24

What is the breakpoint

Answer 24

the chosen concentration of an antibiotic which defines whether a species of bacteria is susceptible or resistant to the antibiotic

Question 25

What is clinical resistance defined as

Answer 25

when infection is highly unlikely to respond even to a maximum dose of antibiotics

Question 26

Why are we trying to move more towards pen V in dentistry

Answer 26

Currently in Scotland, amoxycillin is prescribed more than Pen V Amoxycillin is a broad spectrum AB and is more likely to encourage the development of resistance so there is a move in Scotland to make pen V the first line drug which is narrow spectrum for dentoalveolar infections

Question 27

Are dental abscesses usually endogenous or exogenous

Answer 27

endogenous

Question 28

Are dental abscesses usually aerobic or anaerobic bacteria

Answer 28

mixed

Question 29

What is the ideal specimen for dental abscess

Answer 29

pus aspirate

Question 30

What is the common microbiology for a dental abscess

Answer 30

streptococcus anginosus and prevotella intermedia

Question 31

What is the microbiology of pericoronitis

Answer 31

* Predominantly mixed oral anaerobes

Question 32

What are predisposing factors of osteomyelitis

Answer 32

* Bisphosphonate therapy (most common) - MRONJ * Impaired vascularity of the bone (radiotherapy, pagets disease) * Foreign bodies (implants) * Compound fractures * Impaired host defences (diabetes)

Question 33

What is the microbiology of osteomyelitis

Answer 33

* Anaerobic gram negative rods * Anaerobic streptococci * Examples include streptococcus anginosus & staphylococcus aureus

Question 34

What is the microbiology of a salivary gland infection

Answer 34

o Mixed anaerobes o S. aureus

Question 35

What is the treatment for a salivary gland infection

Answer 35

o Drain o Flucloxacillin & metronidazole o Flucloxacillin is for the staph. Aureus o Metronidazole is for the mixed anaerobes

Question 36

What should you always document with any infection

Answer 36

1. Document your diagnosis 2. Document your antibiotic of choice, it’s dose, route & duration 3. Document a review date (usually 24-48 hours) 4. Document any deviation from guidance and justification

Question 37

What is Ludwig's angina

Answer 37

bilateral infection of the submandibular space

Question 38

What is the most common bacteria in Ludwig's angina

Answer 38

anaerobic gram negative bacilli but it can be caused by staphylococcus aureus

Question 39

What is the definition of sepsis

Answer 39

life threatening organ dysfunction caused by dysregulated host response to infection

Question 40

What is septic shock

Answer 40

sepsis + unresponsive + unresponsive to fluid resuscitation subset of sepsis with circulatory / cellular metabolic dysfunction associated with higher risk of mortality

Question 41

How does sepsis occur

Answer 41

bacteria enter blood stream and detected by culture --> bacteraemia when this matches with certain signs and symptoms, called sepsis host defence mechanisms activated, cascade of cytokines mediate systemic response excessive/prolonged activation can lead to problems including development of organ dysfunction and circulatory septic shock

Question 42

What can microbial products can trigger sepsis

Answer 42

LPS (endotoxin) from gram negative bacteria and exotoxins, teichoic acid and peptidoglycan from gram-positive bacteria and exotoxins/supernatigens from both gram positive and gram negative bacteria

Question 43

What is SIRS

Answer 43

systemic inflammatory response syndrome SIRS + infection = sepsis need 2 or more signs

Question 44

What are the 4 signs of SIRS

Answer 44

o Temperature >38 or <36 o Heart rate > 90 BPM o Respiratory rate > 20 breaths per minute o White blood cell count >12000 or <4000

Question 45

What is the most common bacteria behind sepsis

Answer 45

ecoli

Question 46

What is the sepsis 6

Answer 46

o Give high flow oxygen o Take blood cultures o Give IV antibiotics o Give a fluid challenge o Measure lactate o Measure urine output