microbiology and antimircrobials Flashcards
aerobic bacteria
need oxygen to grow
capnophilic bacteria
need CO2 to grow
faculatative bacteria
can grow with and without oxygen
strictly anaerobic bacteria
can only grow without oxyegn (can be toxic for some)
Metronidazole only works on them
gram positive bacteria appear
on stain
purple on
gram negative bacteria appear
on stain
red/pink
cocci
round shape
bacilli
rod shape
e.g. gram positive cocci
S.anginosus
e.g. gram negative cocci
veillonella species
e.g. gram positive bacilli
actinomyces israelli
e.g. gram negative bacilli
prevotella intermedia
WHO defintion of anitmicrobial resistance
“Antimicrobial resistance occurs when microorganisms such as bacteria, viruses, fungi and parasites change in ways that render the medications used to cure the infections they cause ineffective.”
black pigmented – prevotella intermedia
2 main mechanisms of resistance through resistance genes
intrinsic resistance
acquired resistance
acquired resistance from resistance genes can be either
mutation or acquisition of New DNA
3 types of acquisistion of new DNA for resistance genes
transformation
transduction
conjugation
3 main mechanisms of antiobiotc resistance
altered target site
enzyme inactivation
decreased uptake
altered target site mechanism for resisstance
Bacteria have changed the shape of antibiotics receptor – no longer able to bind
- E.g.
- Viridans group Streptococci
- E.g. S. mitis
- Penicillin resistance due to modified penicillin binding proteins
- Viridans group Streptococci
ezyme inactivation mechanism for resistance
Enzymes destroy antibiotics or prevent them binding to target sites
E.g.
- Prevotella and Fusobacterium species against penicillin and amoxicillin (e.g. Penicillin V)
- mostly beta-lactamases
- Penicillin used – bacteria evolved penicillinase*
- Penicillinase resistant drugs made – beta-lactamase evolved*
- Chemist further modified the (extended spectrum beta-lactamases) and bacteria then evolved extended spectrum beta-lactamases (ESBL) to breakdown the new AB*
decreased uptake mechanism of resistance
Large capsule around bacteria – affecting uptake of AB
how many forms of resistance can bacteria utilise
multiple
type of infection that odontogenic ones are (e.g. acute periapical infection)
exo or endo
endogenous infection
bac orginate from us
single or multi organism infection for odotogenic infection
often multi/mixed infections
aerobic and anaerobic, work in symmetry
strict anaerobes are key to them
e.g. Streptococcus anginosus (common in acute dentoalveolar infection), Prevotella intermedia (gram negative, strict anaerobe)
ideal specimen for odontogenic infection
pus aspirate
can be hard to get in general practices
common bac in periodontal abscess
Anaerobic streptococci, Prevotella intermedia
tx principles for localised dental infection
- Establish a diagnosis & document it
- Remove the source of infection
- Pulp extirpation or incision and drainage or extraction
microbiology for periocornitis
Predominantly mixed oral anaerobes, e.g, P. intermedia, S. anginosus group
tx pericornitis
- Local measures
- Systemic (only if systemic signs/symptoms)
dry socket microbiology
- Localised alveolar osteitis
- Mixed oral flora
- Extremely painful
- Does not require antibiotic treatment
- LA, debridement and pack with antimicrobial gels/strips
osteomyelitis of jaw
predisposed by
- Biphosphonate therapy (BRONJ/MRONJ)
- Impaired vascularity of bone (radiotherapy, Pagets disease)
- Foreign bodies (implants)
- Compound fractures
- Communication either intra or extra orally
- Impaired host defences (diabetes)
what happened here
Post-dental extraction infection osteomyelitis of the jaws
- 48 removed
- 2nd x-ray – post op review, pt complained of dry socket, which was managed locally
- 3rd x-ray – pt developed infection which extended into ramus and border of mandible
- Needed to go back to surgical theatre and bone curetted out and then long course IV AB (6 weeks)
micrbiology in osteomyleitis of jaw
Anaerobic Gram negative rods
- Anaerobic streptococci
- Streptococcus anginosus
- Staphylococcus aureus
- Worry – effect AB choice, difficult to tx, need prolonged course of AB
Is aseptic necrosis of bone first or infection first?
Common bacteria cause of cultured bone specimens (difficult as get contamination by oral micro flora)
- S.angiosus
- Mixed anaerobes
- Actinomyces iraelii
SDCEP guidelines – Oral health management of pt at risk of MRONJ
microbiology of salivary gland infection
- S. aureus
- Mixed anaerobes
tx salivary gland infection
- Dx and Drainage
- Flucloxacillin & metronidazole
for all odontogenic infections - what you MUST do (4)
- Systematic history and examination. Document your diagnosis
- Document Ab choice, dose, route & duration
- Document a review date (24-48hr for acute)
- Document deviation from guidance
Ludwig’s angina defintion
bilateral infection of submandibular space
most common bacteria involved in ludwig angina
- Anaerobic Gram negative bacilli
- Streptococcus anginosus
- Anaerobic streptococci
Severe odontogenic infections, watch for S.aureus
why is taking specimen imp
not always the same common bacteria causing odontogenic infections
- important to take specimens for culture and sensitivity testing so can modify AB tx
Severe odontogenic infections, watch for S.aureus
sepsis
each hour delay in giving AB
For each hour delay in AB administration mortality increases by nearly 10%
- sooner given AB – better survival rate
Reassess antimicrobials daily:
- Optimise
- Reduce Resistance
- Avoid Toxicity
- Reduce costs
sepsis =
SIRS + suspected/confirmed infection
need to go to hospital
sepsis defintion
life threatening organ dysfunction caused by dysregulated host response to infection
SIRS
systemic inflammatory response syndrome
2 or more of
temp <36 or >38
pulse > 90/min
resp rate >20/min or PaCO2 <4.3
WCC <4 or >12
septic shock =
sepsis + unresponsis to fluid resuscitation
septic shock defintion
subset of sepsis with circulatroy and cellular/metabolic dysfunction associated with higher risk of mortality
sepsis in scotland
- Kills around 3,500 people in Scotland every year (any source)
- 1 person every 4 hours
- Mortality rates from sepsis have fallen by 21% since 2012
- Many public campaigns to spread knowledge of noticing signs
- sepsis 6
primary care tx principles for SOI and Ludwig’s angina
hx, exam, dx
seek advice/help - maxfax unit
secondary care tx principles for SOI and Ludwig’s angina
- Diagnosis
- Sepsis 6
- High flow oxygen
- Take blood cultures
- Give IV antibiotics
- Give a fluid challenge
- Measure lactate
- Measure urine output
- National Early Warning Score (NEWS – 2)
sepsis 6
- High flow oxygen
- Take blood cultures
- Give IV antibiotics
- Give a fluid challenge
- Measure lactate
- Measure urine output
what is more effective for localised infection
surgical tx or antibiotics
surgical tx (removal of source and good drainage)
need appropriate dx
antimicrobial resistance - biological defintion
Resistance definitions usually based on in-vitro quantitative testing of bacterial suspensions to antibacterial agents
- Minimum inhibitory concentration noted on e strips
- Automated susceptibility testing system (tests are usually automated now)
breakpoint defintion
chosen concentration (mg/L) of an antibiotic which defines whether a species of bacteria is susceptible or resistant to the antibiotic
antimicrobial resistance clinical defintion
When infection is highly unlikely to respond even to maximum doses of antibiotic (EUCAST)
confounding variable when working out resistance
need to try standardise them
- Laboratory
- Inoculum size, growth phase, planktonic (in solution), pH, atmosphere…
- Breakpoint calling
- -Biofilm (most infections in this form – bacteria grow slower, metabolic rates are slower, sometimes need 1000 times usual dosage of AB disinfectant to kill biofilm bacteria)
- Clinical
- Co-morbidities, pus collections (imp in acute dentoalveolar infections, hard to get AB to penetrate into pus – need to surgically remove pus when possible), foreign bodies, site of infection
- Biofilm – almost impossible to tx due to changes in bacterial phenotypes
- Pharmacokinetics – distributed through body
- Pharmacodynamics – antibiotic classes interact with bacteria
European resistance rate different to US – artificial due to differences in definitions used, careful when looking at data
surveillance of microbiology of acute dentoalveolar infections
needs to be
continually done
constantly evolving
how to improve surveillance of bacteral dental infections for AMR (3)
- Agree definitions of resistance for common isolates in SEVERE odontogenic infections (SOI’s)
- Standardised specimen collection, processing & reporting for SOI’s (Surveillance)
- Return to 1st choice Penicillin V IF antibiotics required
antimicrobial stewardship
- Teamworking
aim
- ‘preserve antimicrobial medicines by taking measures to promote their control’
good OH aid in antimicrobial stewardship
revents infection from spreading, reducing the need for antibiotics which helps limit antibiotic resistance
5 strategic objectives of the WHO global action plan on antimicrobial resistance
- Improve awareness and understanding
- Strengthen the knowledge through surveillance and research
- Reduce the incidence of infection
- Optimise the use of antimicrobial medicines
- Ensure sustainable investment
One health – work with colleagues, environment, animals (vets and farmers) to reduce antimicrobial resistance
UK action plan for AMR 2019-2024
key way to help
Reducing need for, and unintentional exposure to, antimicrobials (prevention of disease)
3 reasons for inappropriate AB prescribing
- 30% prescribed due to time/workload pressures
- 47% prescribed when unsure of diagnosis
- 72% prescribed where treatment had to be delayed
wrong tx for acute pulpitis
AB
antibiotics ineffective
wrong tx for chronic gingivitis
AB
antibiotics ineffective
wrong tx for sinusitis due to dental cause
AB
antibiotics ineffective
wrong tx for dry socket
AB
antibiotics ineffective
wrong tx for chronic perio
AB
antibiotics ineffective
pencillin and amoxicillin connection
same class
both beta-lactamase antiobiotics
1st line AB for dental alveolar infections
beta-lactamase agent (e.g. pencillin, amoxycillin)
not metronidazole
should dentists prescribe metronidazole
no
not 1st line AB for dental alveolar infection (not beta-lactamase agent)
drives selection of metronidazole strict anarobes - worry
amoxicillin or penicillin for dental-alevolar infections?
Main ab prescribed in Scotland is beta-lactame amoxicillin
- Wide spectrum agent
- Evidence to suggest that is more likely encourage development of resistance
Soon to switch to Pen V as 1st line
- Narrower spectrum
- Evidence as Norway and Sweeden have been doing this for decade
3 ways to contribute to slow AMR
- Prevent dental disease
- Prevent spread of disease
- Wash hands/SICPs
- Get vaccinated against flu
- Antibiotics don’t cure toothache
