A Few More Bacteria to Know: Difference between revisions

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* Beta-lactams
 
* Beta-lactams
** Penicillins: piperacillin/tazobactam
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** Penicillins: piperacillin-tazobactam
** Cephalosporins: ceftazidime and ceftolozane/tazobactam
+
** Cephalosporins: ceftazidime and ceftolozane-tazobactam
 
** Carbapenems: meropenem (+/- vaborbactam), ''not'' ertapenem
 
** Carbapenems: meropenem (+/- vaborbactam), ''not'' ertapenem
 
* Fluoroquinolones: ciprofloxacin, sometimes levofloxacin, but ''not'' moxifloxacin
 
* Fluoroquinolones: ciprofloxacin, sometimes levofloxacin, but ''not'' moxifloxacin
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* They are:
 
* They are:
 
** S: ''Serratia marcescens''
 
** S: ''Serratia marcescens''
** P: ''Providentia'' spp.
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** P: ''Providencia'' spp.
 
** I: Indole-positive ''Proteus'' (that is, ''P. vulgaris'')
 
** I: Indole-positive ''Proteus'' (that is, ''P. vulgaris'')
 
** C: ''Citrobacter'' spp.
 
** C: ''Citrobacter'' spp.

Latest revision as of 14:28, 27 March 2024

There are some special bacteria that you should know a little bit about.

Methicillin-resistant Staphylococcus aureus (MRSA)

  • A mutation in the penicillin-binding protein confers resistance to all beta-lactams (PBP 2a)
  • More common in patients with previous hospitalisations and antibiotic exposures, a history of being in prison or homeless shelters, participation in group sports especially wrestling

Intravenous antibiotics

  • Vancomycin is the most common
    • Dose is usually 10-20 mg/kg/day split bid to tid
    • Get a trough 0 to 60 minutes before the fourth dose after every dose change
    • Target trough is typically 10-15 for boring MRSA infections like SSTI, or 15-20 if they have a significant MRSA infection (bacteremia, osteomyelitis, pneumonia)
    • No specific target trough for non-MRSA infections, so just make sure that they're safe
  • Daptomycin is the step up, but you should probably call ID if you're going to use it

Oral antibiotics

  • There's a secret list of oral antibiotics that can be used to treat MRSA infections
  • Clindamycin
  • Septra (TMP-SMX)
  • Doxycycline
  • Linezolid ($$$)

Pseudomonas aeruginosa

  • A very resistant Gram-negative bacterium that is associated with water
  • Becomes more common when antibiotics kill off other bacteria
  • Can cause pneumonia (usually HAP/VAP), UTI, and bacteremia, and is also implicated in intraabdominal infections

Antipseudomonal antibiotics

  • Beta-lactams
    • Penicillins: piperacillin-tazobactam
    • Cephalosporins: ceftazidime and ceftolozane-tazobactam
    • Carbapenems: meropenem (+/- vaborbactam), not ertapenem
  • Fluoroquinolones: ciprofloxacin, sometimes levofloxacin, but not moxifloxacin
  • Aminoglycosides: tobramycin, gentamicin, amikacin
  • Monobactam: aztreonam
  • Polymixins: colistin

SPICE HAM organisms

  • A group of Gram-negative organisms that have an inducible extended-spectrum beta-lactamase (ESBL)
  • After 48 to 72 hours of antibiotics, they become resistant to all penicillins and cephalosporins, so usually need treatment with carbapenems or aminoglycosides
  • They are:
    • S: Serratia marcescens
    • P: Providencia spp.
    • I: Indole-positive Proteus (that is, P. vulgaris)
    • C: Citrobacter spp.
    • E: Enterobacter spp.
    • H: Hafnia spp.
    • A: Acinetobacter spp. (not inducible, but very resistant)
    • M: Morganella spp.