Meningitis is very literally inflammation of the meninges. Something swollen in a closed space is never good, so it’s important to not miss meningitis when it presents.
Classic triad of meningitis
- Neck stiffness
- Mental status change – in babies this can be an increase in somnolence or irritability (unconsolably crying)
- E. coli*
- GBS (Group B strep)*
- Neisseria meningitidis
- Strep pneumoniae
- Staph aureus
- Gram neg bacilli
- Haemophilus influenza
- Viral (“aseptic”)
* These are the common ones in the neonatal period
- Positive Gram stain
- CSF white blood cell (WBC) count >1000/uL with a predominance of neutrophils
- Low CSF glucose concentration <40 mg/dL (2.2 mmol/L)
- Empiric treatment: high doses of a 3rd generation cephalosporin (cefotaxime, ceftriaxone) and vancomycin (this covers antibiotic-resistant S. pneumoniae, N. meningitidis, and Hib)
Cephalosporins work much like penicillins, inhibiting peptidoglycan cell wall synthesis in bacteria (remember those sites of action and mechanisms?)
Of course the issue is that they just keep making new cephalosporins and each generation is a little bit different in terms of its spectrum and whether it’s better at fighting Gram positive or Gram negative bacteria. Generally the newer the generation, the more broad spectrum and less Gram positive coverage. To add another layer to the confusion, there are separate oral and IV cephalosporins for each generation and all of the cephalosporins are usually recognizable by starting with “CEF-” or “KEF-” (except for Suprax and Ancef, who ever came up with those brand names didn’t get the memo)
These are the different classes of medications and their mechanism of action. I’ve sorted them by which ones are exclusively Gram + or Gram – and which ones do both.
Here’s a handy mnemonic for remembering the antibiotics that act on the ribosomes (I find they’re the most confusing to remember):
Buy AT 30
CELL for 50
Antibiotics are the current bane of my existence. Most medical conditions there are a couple of different classes of drugs, but overall things are straight forward. Not so with antibiotics, not only are there a bunch of different classes, they all have different indications!
This is part 1 of my antibiotics doodles. This one outlines where the different commonly used antibiotics act on the cell, the class they belong to, and whether they are used mostly for Gram + (Staph, Strep), Gram -, or a little bit of both. Keep in mind that the bacterial cell in the drawing is a Gram + coccus.
Part 2 will go into a little more detail about the different classes.