Infection- Antimicrobials and antibiotics Flashcards
What are examples of gram positive microbes? (purple)
- Cocci- s. aginosus
- Bacilli- actinomyces israelli
What are examples of gram negative microbes? (pink/red)
- Cocci- veillonella
- Bacilli- Prevotella Intermedia
What are the different classifications of microbes based on their growth conditions?
Aerobic = Oxygen
Capnophilic = Carbon dioxide
Facultative = With & without oxygen
Strictly Anaerobic = without oxygen
What is the only antimicrobial that works on strict anaerobes?
Metronidazole
Why are facultative anaerobes resistant to metronidazole?
Due to their metabolic pathways
What is antimicrobial resistance?
Occurs when microorganisms such as bacteria, viruses, fungi and parasites change in ways (due to selection pressures) that render the medications used to cure the infections they cause ineffective
What are the types of resistance?
Intrinsic
-> prevotella to vancomycin
Acquired- via mutation OR acquisition of new DNA (transformation, transduction, conjugation)
What are some examples of resistance mechanisms?
- Alteration of target site- changed receptor for antibiotics (e.g. penicillin resistance in strep. Mitis)
- Enzymatic inactivation- destroy antibiotics or prevent binding (Beta lactamase can destroy penicillin)
- Decreased uptake- Klebsiella pneumoniae
What occurred in the beta-lactam arms race?
Penicillinase previously developed by microbes to destroy beta-lactam in penicillin
Resistant penicillin was produced with side chains- but then bacteria developed beta-lactamase
Extended spectrum antibiotics were produced- but bacteria also produced extended spectrum beta-lactamase
What are carbapenems?
New AB- protect beta lactams in penicillin
What are the issues with carbapenems?
Bacteria have developed carbapenemase to destroy this
-> some bacteria are resistant to all ABs (Multi-drug resistant microorganisms can be found in dento-alveolar infections)
What are the microbes present in PA infections/abscesses? (endogenous)
Mixed- aerobic and anaerobic (synergy)
* Facultative- s.aginosus
* Strict anaerobe- prevotella intermedia (gram-)
What would be the ideal method to take a specimen from a dental abscess?
Pus apsirate
-> might be difficult to achieve (likely only done in hospital setting- severe infections)
What microbes are present in periodontal abscesses?
Anaerobic streptococci
Prevotella intermedia
What are the treatment options for removing dental infection?
Open pulp cavity
Extirpation of pulp
RCT
I/D of abscess
Extraction
What microbes are present in pericoronitis?
Mixed anaerobes :
P.intermedia
S.aginosis group
What are the treatment options for pericoronitis?
Local measures
Systemic (only if systemic signs/symptoms)
What is Dry Socket?
Blood clot becomes dislodged, so healing socket is exposed to oral flora
-> localised alveolar osteitis
How is dry socket treated?
LA, debridement and packing with AM gels (not antibiotics)
What occurs in osteomyelitis?
Dental infection spreads into ramus and lower border of mandible
What are the predisposing factors for Osteomyelitis of the jaws?
Biphosphonate therapy (BRONJ/MRONJ)
Impaired vascularity of bone (radiotherapy, Pagets disease)
Foreign bodies (implants)
Compound fractures
Impaired host defences (diabetes)
Which microbes are involved in osteomyelitis of the jaws?
Anaerobic Gram negative rods- p.intermedia
Anaerobic streptococci
Streptococcus anginosus
Staphylococcus aureus (common in bone infections- difficult to treat)
How is OM treated?
Curette bone out
6 weeks course of IV antibiotics
Which microbes are associated with MRONJ?
S. anginosus
Mixed anaerobes
Actinomyces israelii- gram + bacilli
What microbes are associated with salivary gland infection? What is used to treat these?
S.aureus (flucloxacillin)
Mixed anaerobes- metronidazole
-> drainage if required
What should be documented in the notes when prescribing antibiotics to treat dental infection?
Document your diagnosis
Document AB choice, dose, route & duration
Document a review date- 24-48 hours after presenting with acute infection
Document deviation from guidance
What is the classic presentation of a severe odontogenic infection (Ludwig’s angina)?
Bilateral infection of submandibular space
Which microbes are associated with SOI?
Anaerobic Gram negative bacilli
Streptococcus anginosus
Anaerobic streptococci
P.intermedia
-> s.aurues can also be involved inn head and neck infection of dental origin
What are the issues with people being referred to hospital for SOIs?
2-3 patients per week admitted to hospital for treatment of SOI
Many patients need to return to theatre for more treatment
Very costly to NHS- cause long stays in hospital up to 20 days (as patients had sepsis on admission)
What is sepsis?
Life-threatening organ dysfunction caused by dysregulated host response to infection:
Presence of infection AND Systemic Inflammatory Response Syndrome (SIRS)
-> can lead to septic shock
What are the features of SIRS
Pulse- > 90 BPM
Temp- < 36 or > 38
Resp rate- > 20/min
WCC- < 4 or > 12
What is septic shock?
Sepsis + unresponsive to fluid resuscitation
-> Subset of sepsis with circulatory and cellular/metabolic dysfunction associated with higher risk of mortality
What is the role in the primary care dentist in treating sepsis?
Diagnosis
-> seek advice and help
What are the aspects in the sepsis 6? (secondary care)
- Give high flow oxygen
- Take blood cultures
- IV antibiotics
- Give fluid challenge
- Measure lactate
- Measure urine output
-> all in first hour of admission
What is the issue with giving amoxicillin for RTI and UTI?
Resistance can persist a month after treatment (perhaps even a year
What is the issue with pseudomonas aueriginosa?
Resistant to ALL but 2 of available antibiotics
-> Colistin and Amikacin
How is resistance ascertained?
Usually based on in-vitro quantitative testing of bacterial suspensions to antibacterial agents
-> uses Automated susceptibility testing system
What is the break point?
Concentration of antibiotics which defines whether bacteria is resistant or sensitive
-> Clinically resistant- unlikely to respond to even high (or max) doses of AB
What are the issues with biofilms and resistance?
Increases chances of resistance and dose needed
-> Bacteria grow slower and metabolic rates are slower
-> can be almost impossible to treat clinically
What is recommended when foreign bodies are present in infection?
Removal
Why is s.aginosus particularly worrisome?
Can cause pus accumulation
Break point (minimum inhibitory concentration) has increased (different in EU/US)
Resistance has increased to erythromycin/clindamycin
What is antimicrobial stewardship?
Multidisciplinary team working to protect antimicrobial medicines and promote their control
What are ways that antibiotic prescribing can be reduced in dentistry?
Reducing incidence of acute infection and therefore systemic infections (via prevention/SICPs)
Reduce need for unintentional exposure via- prevention, diagnosis (document), making correct treatment decision
Why is metronidazole no longer the first line choice for acute dentoalveolar infection?
Needs to be a beta-lactam agent
-> Over-prescription is driving metronidazole resistance in strict anaerobes
-> Gram positive cocci are resistant to penicillin but not metronidazole
Why is amoxicillin not used as the first line of defence?
Amoxicillin is broader spectrum and is more likely to encourage resistance in oral cavity, RT, GIT
What is now used as the first line of defence against dentoalveolar infection?
Penicillin V (narrow spectrum- for oral infections)
