Oral Surgery Flashcards
What are the features of Gram Negative bacteria
- Has an inner and outer membrane (2 membranes)
- Releases endotoxins (LPS) + exotoxins
- Stains RED
What are features of Gram Positive bacteria
- No outer membrane but is surrounded by layers of peptidoglycan which is thicker than that of gram negative
- Contains teichoic acid + lipteichoic acid in cell wall
- Releases exotoxins only
- Stains purple
Why does gram negative stain pink
organic solvent used disrupts membrane and stain is washed out of cell
Why does gram positive stain violet
as it retains the fixed violet dye within the cell
What is an example of a gram positive cocci
s. anginosus
streptococcus mutans (facultative)
What is an example of a gram negative cocci
veillonella species
What is an example of a gram positive bacilli
actinomyces israelii (anaerobic)
clostridium difficile (anaerobic)
What is an example of a gram negative bacilli
prevotella intermedia
What does aerobic growth conditions mean
requires oxygen
What does capnophilic growth conditions mean
requires carbon dioxide
What does facultative growth conditions mean
can survive with/without oxygen
What does strictly anaerobic growth conditions mean
requires no oxygen, oxygen can be toxic. Metronidazole is the only antibiotic that works on these
What is antimicrobial resistance
occurs when microorganisms change in ways that render the medications used to cure the infections they cause ineffective
What are the 2 main types of resistance
intrinsic
acquired
What is intrinsic resistance
bacterial species is naturally resistant to a certain antibiotic/family of antibiotics without the need for mutation/gain of further genes
What are the 2 types of acquired resistance
mutation
acquisition of new DNA
How does mutations result in resistance
- 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
What are the 3 methods that a bacterium can acquire new DNA
Transformation, transduction, conjugation
What are the 2 mechanisms of resistance
altered target
enzymatic deactivation
Describe altered target mechanism of resistance and give an example
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
What is the enzymatic deactivation mechanism of resistance
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
What are the 2 types of antibiotic testing
diffusion and dilution
What is the minimum inhibitory concentration
this is the lowest concentration of a chemical, usually a drug which prevents visible growth of a bacteria or bacteria
What is the breakpoint
the chosen concentration of an antibiotic which defines whether a species of bacteria is susceptible or resistant to the antibiotic
What is clinical resistance defined as
when infection is highly unlikely to respond even to a maximum dose of antibiotics
Why are we trying to move more towards pen V in dentistry
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
Are dental abscesses usually endogenous or exogenous
endogenous
Are dental abscesses usually aerobic or anaerobic bacteria
mixed
What is the ideal specimen for dental abscess
pus aspirate
What is the common microbiology for a dental abscess
streptococcus anginosus and prevotella intermedia
What is the microbiology of pericoronitis
- Predominantly mixed oral anaerobes
What are predisposing factors of osteomyelitis
- Bisphosphonate therapy (most common) - MRONJ
- Impaired vascularity of the bone (radiotherapy, pagets disease)
- Foreign bodies (implants)
- Compound fractures
- Impaired host defences (diabetes)
What is the microbiology of osteomyelitis
- Anaerobic gram negative rods
- Anaerobic streptococci
- Examples include streptococcus anginosus & staphylococcus aureus
What is the microbiology of a salivary gland infection
o Mixed anaerobes
o S. aureus
What is the treatment for a salivary gland infection
o Drain
o Flucloxacillin & metronidazole
o Flucloxacillin is for the staph. Aureus
o Metronidazole is for the mixed anaerobes
What should you always document with any infection
- Document your diagnosis
- Document your antibiotic of choice, it’s dose, route & duration
- Document a review date (usually 24-48 hours)
- Document any deviation from guidance and justification
What is Ludwig’s angina
bilateral infection of the submandibular space
What is the most common bacteria in Ludwig’s angina
anaerobic gram negative bacilli but it can be caused by staphylococcus aureus
What is the definition of sepsis
life threatening organ dysfunction caused by dysregulated host response to infection
What is septic shock
sepsis + unresponsive + unresponsive to fluid resuscitation
subset of sepsis with circulatory / cellular metabolic dysfunction associated with higher risk of mortality
How does sepsis occur
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
What can microbial products can trigger sepsis
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
What is SIRS
systemic inflammatory response syndrome
SIRS + infection = sepsis
need 2 or more signs
What are the 4 signs of SIRS
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
What is the most common bacteria behind sepsis
ecoli
What is the sepsis 6
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
