Antimicrobial Agents 2 Flashcards
What are broad spectrum antibiotics good for?
An optimal initial choice for nosocomial pneumonia and severe sepsis.
What methods are used to help identify the pathogen?
Gram stain: CSF, Joint aspirate, Pus
Rapid antigen detection: Immunofluorescence, PCR
When is each route of antibiotic administration appropriate?
IV: Serious (or deep/ CNS) infection.
PO: Avoid if poor GI function or vomiting. Different classes of antimicrobial have different oral bio-availabilities
IM: Not an option for long-term use. Avoid if bleeding tendency or drug is locally irritant.
Topical: Limited application + may cause local sensitisation.
When is it recommended to switch from IV to PO?
Recommended in hospital for most infections if the patient has stabilised after 48 hours IV therapy
What are the three patterns of activity for antibiotics?
Type I: Conc. dependent killing + prolonged persistent effects
Type II: Time-dependent killing + minimal persistent effects
Type III: Time-dependent killing + moderate to prolonged persistent effects.
What are the Type I antibiotics?
Aminoglycosides
Daptomycin
Fluoroquinolones
Ketolides
What is the goal of Type I antibiotic therapy?
Maximize concentrations
The higher the peak above MIC the better the response
What are the Type II antibiotics?
Carbapenems
Cephalosporins
Erythromycin
Linezolid
Penicillins
What is the goal of Type II antibiotic therapy?
Maximize duration of exposure
The longer the time above the MIC the better
What are the Type III antibiotics?
Azithromycin
Clindamycin
Oxazolidinones
Tetracyclines
Vancomycin
What is the goal of Type III antibiotic therapy?
Maximize amount of drug for maximal time
Often given as infusion
Constant big area under curve
What is the recommended length for a course of antibiotics for N. meningitidis meningitis?
7 days
What is the recommended length for a course of antibiotics for Acute osteomyelitis (adult)?
6 weeks
What is the recommended length for a course of antibiotics for bacterial endocarditis?
4-6 weeks
What is the recommended length for a course of antibiotics for Gp A Streptococcal pharyngitis?
10 days
What is the recommended length for a course of antibiotics for Simple cystitis (in women)?
3 days
What are common skin infections and what pathogens cause them?
Impetigo, Cellulitis + Wound Infections
Common organisms include S. aureus + beta-haemolytic Streptococci
What antibiotics are used to treat skin infections?
Flucloxacillin (unless penicillin allergy or MRSA)
What is the treatment for Invasive Group A Streptococcal (iGAS)?
Aggressive + early debridement
Abx: adjunctive use of protein synthesis inhibitors esp. clindamycin (also has good skin + soft tissue penetration)
Use of IVIg
What is the Eagle effect?
Penicillin doesn’t have a good effect at a higher conc., also pencillin isn’t good against high conc. of bacteria.
Why does the Eagle effect happen?
In cases of high bacterial burden, the bacteria isn’t actually replicating so penicillin doesn’t really work.
What is the treatment for pharyngitis?
Benzyl penicillin x 10 days
What is the treatment for mild community acquired pneumonia?
Amoxicillin
What is the treatment for severe community acquired pneumonia?
Co-amoxiclav + clarithromycin
What are hospital-acquired respiratory tract infections?
2nd most common cause of HAI
Associated with highest mortality (23%)
Greatest risk associated with tracheal intubation + mechanical ventilation
What is the treatment for hospital-acquired respiratory tract infections?
Cephalosporin; ciprofloxacin; piperacillin/ tazobactam
If MRSA colonised/ risk, consider addition of Vancomycin
What are the main bacteria for meningitis?
N. Meningitidis
S. pneumoniae
Listeria in the very young/ elderly/ immuno-compromised
What is the treatment for meningitis?
Ceftriaxone (+/- amoxycillin if Listeria likely)
What is the treatment for meningitis in a baby less than 3 months old?
Cefotaxime PLUS Amoxicillin (to cover for listeriosis)
Ceftriaxone not used in neonates as displaces BR from albumin + because it can cause biliary sludging
What is the treatment of Neisseria meningitidis?
Benzylpenicillin (high dose) or Ceftriaxone/Cefotaxime
What is the treatment for community acquired simple cystitis?
Trimethoprim x 3d (7 for men + pregnant women)
Nitrofurantoin x 3d (7 for men + pregnant women)
Nitro preferred in first 2 trimesters
What is the treatment for hospital-acquired UTI (commonest type of HAI)?
Cephalexin or co-amox
What is the treatment for an infected urinary catheter?
Change under gentamicin cover
What is the treatment for C. diff?
STOP the offending abx (usually a cephalosporin);
If severe, Rx with PO vancomycin.
If above fails, use PO fidaxomicin.
Final step IV metronidazole + oral vanc.
What are things to recover if there is no improvement within 48 hours?
Does the patient really have a bacterial infection? (Have I collected the relevant cultures?)
Is there a persistent focus present (e.g. an infected vascular or urinary catheter)?
Is there a deep-seated collection (e.g. intra-abdominal) that requires drainage?
Could the patient have bacterial endocarditis?
Am I using the correct dose of the antimicrobial?
Is another infection present (esp consider Candida)?
Give 6 common side effects of antibiotics
GI upset
Hepatitis
Fever
Rash
Renal dysfunction
Acute anaphylaxis
When are IV antibiotics used?
When patient not absorbing PO
When deep sites/ CNS involvement
What is the MIC? How is this measured?
the least amount of antibiotic required to inhibit growth in vitro
Gradient strips or disc diffusion
What does MIC relation to the breakpoint line indicate?
Above= unlikely to be successful at normal doses used. Reported as resistant
Below= likely to be successful: either reported as “susceptible” or “susceptible with optimized dosing” (not at normal BNF dosing)
