Mechanism of Action
What does 'bacteriostatic' mean?
An agent that stops bacteria from growing/reproducing
Name 2 beta-lactams
Penicillins
Cephalosporins
Carbapenems
Beta-lactamase inhibitors (clavulanic acid)
What category of bacteria does vancomycin cover
Gram positive cocci (MRSA, MSSA, Strep)
50F from home with bilateral consolidation on CXR + fever + dyspnoea + shock requiring peripheral vasopressors. No travel. ICU admit. No allergies.
What are 2 causative pathogens for this disease, and what is the first line antibiotic therapy?
Severe community acquired pneumonia.
Most common bug: Strep. pneumoniae
Less common: mycoplasma/chlamydophilia pneumoniae, legionella, H. Influenzae
Rare: Staph. aureus, Pseudomonas. Aeruginosa
1st line therapy:
Ceftriaxone 1g BD + azithromycin 500mg daily
Give 2 examples of bactericidal antibiotics
Penicillins
Cephalosporins
Glycopeptides
Aminoglycosides
Quinolones
What class of antibiotic does Vancomycin belong to?
Glycopeptides
Name 3 antibiotics that treat Pseudomonas
Tazocin
Cefepime
CeftazadimeMeropenem
Ciprofloxacin
Gentamicin
45F presents with acutely decreased conscious state and is intubated in ED for airway protection.
CT scan demonstrates acute intracranial bleed. She is transferred to a neurosurgical hospital.
Should any antibiotics be given? If so what should be given and why?
The 2024 PROPHY-VAP supports the use of a single dose of ceftriaxone 2g IV for VAP prophylaxis
It's been shown to reduce rate of VAP, increased ventilator free days and increased antibiotic free days
This should be given to this patient post intubation.
Describe 3 different mechanisms of action of antibiotics (target site on bacteria)
1. Inhibition of cell wall synthesis
2. Disruption of cell membrane function
3. Inhibition of protein synthesis
4. Inhibition of RNA and DNA synthesis
5. Inhibition of folic acid synthesis
What category of bacteria do macrolides treat?
Full points if you name 3 genus/species in this category
Atypicals
Mycoplasma pneumoniae
Legionella pneumophila
CHalmydia pneumoniae
Name 3 antibiotics that treat MRSA
Vancomycin
Bactrim
Ciprofloxacin
32M IVDU with fever, janeway lesions and mobile echodensity on mitral valve. Shocked requiring circulatory support. No cardiac history, no allergies.
How many blood cultures are required?
Name 2 causative pathogens (1 must be the most common cause)List 1st line empirical antibiotic therapy
Strong suspicion for infective endocarditis of native valve- start workup for Dukes Criteria to diagnose.
Take at least 3 sets of blood cultures from different peripheral sites (ideally 2 initially and then 1 at least an hour later) - 100
Staph. Aureus (most common), Viridans streptococci (mitis, sanguinis, mutans, salivarius, anginosus - oral bugs). Enteroccus faecalis, enterococcus faecium. - 100
Benzylpenicillin 1.8g IV 4 hourly + flucloxacillin 2g 4 hourly + gentamicin (needs initial dose calculator)
Describe the mechanism of action of beta-lactam antibiotics
Bind to penicillin binding proteins to stop the final step of peptidoglycan synthesis for the bacterial cell wall
Name 6 different classes of antibiotics
Must name at least 6 for points
Beta-lactams
Cephalosporins
Aminoglycosides
Macrolides
Tetracyclines
Lipopeptides
Quinolones
Oxazolidonones
Sulfonamides
Ertapenem covers everything meropenem does except:
Pseudomonas
40F returned 2 weeks ago from Darwin during wet season. Went hiking through wet terrain.
She presents to ED with respiratory distress, and was identified to have distributive shock. CXR notes lobar pneumonia. She is intubated and brought to ICU
Apart from standard infectious disease workup (cultures, bloods), what specific bacterial culture requests will you put on the pathology form?What condition are you suspicious of, that will not be covered by standard severe CAP treatment
How else can it present?
Fever in a patient exposed during wet season. The usual bugs remain suspicious (strep pneumoniae) however specific culture requests for the following should be added to the form:
Meliodosis: blood culture + Ashdown's media culture for sputum (for non-sterile samples)
Acinetobacter baumannii: Standard culture
This patient needs to be covered with treatment for meliodosis with septic shock requiring ICU support:Meropenem 2g loading, then after 4 hours 2g 8 hourly
Melioidosis also presents as complications of bactaraemia (abscess formation in any organ), or neurological manifestations.
Neurological melioidosis is treated with meropenem + bactrim
Acinetobacter bau
Klebsiella
Meilliodosis
Legionella
What is the mechanism of action of linezolid
Binds to ribosomal RNA to stop protein synthesis.
Bacteriostatic to staphylococci and enterococci
Bactericidal to streptococci
Give an example of each generation of cephalosporin. Must name one from all to get points
1st gen: Cefazolin, cephalexin
2nd gen: Cefuroxime, cefmetazole
3rd gen: Ceftriaxone, cefotaxime, ceftazadime
4th gen: Cefepime, Cefpirome
5th gen: Ceftaroline, ceftobiprole
Name one drug that treats an ESCAPPM AND name 5 ESCAPPMs
ESCAPPM is an acronym for a group of gram-negative bacteria that can produce AmpC beta lactamase enzymes. As such they can be resistant to penicillins and third gen cephalosporins
Cefepime, carbopenems, gentamicin, tazocin, ciprofloxacin, bactrim
Enterobacter spp
serratia spp
Citrobacter freundii
Acinetobacter spp
Aeromonas spp
Proteus spp (excluding P. miribalis)
Providencia spp
Morganella morganii
32M from remote WA presenting with 5/7 of worsening neck swelling, sore throat and fever. He has obstructive upper airway sounds and you are concerned he will need to be intubated.
You observe white exudate in the pharynx on examination prior to intubation.
What bacteria, and what manifestation of it are you concerned about?
How do we investigate it?
Given the severity, what is the targeted treatment?
What are other manifestations of the severe pharyngeal version of this disease and briefly what causes it?
This is acute pharyngitis with pharyngeal exudate on a patient from remote Australia. Most common cause of severe pharyngitis is streptococcal pharyngitis.
Suspicion should be raised however with a recent outbreak of diptheria in remote WA
This presentation would be in keeping with toxigenic severe pharyngeal diptheria, caused by cornybacterium diptheriae or cornybacterium ulcerans.
Investigated by pharyngeal swab for culture, however diptheriae culture should be specified
Targeted therapy for severe, pharyngeal diptheriae is azithromycin 500mg IV and benzylpenicillin 1.2 IV 6 hourly
Despite not being registered in Australia, ETG recommends diptheria antitoxin as the primary treatment. It would need state approval
The toxin can also lead to myocarditis, so ECG +/- TTE should be performed.