## Empiric heuristics ![[Pasted image 20250221182613.png|500]] - Empiric coverage often consider an item that cover Gram(+) (Staph A, coag neg Staph) and Gram(-) w/ pseudomonas coverage - Delivery to regions with tight junctions (e.g. blood brain barrier, eye, testes) need smaller agents ± higher dose (Further review: https://foamid.com/2018/03/11/cns-penetration-of-antimicrobials/) ### Beta Lactams ![[Pasted image 20250220183227.png | 500]] - The development and ladder of abx stewarship revolves around the OG penicillins, a β-lactam - As bacteria develop β-lactamase, we paired inhibitors that gobble up these enzymes to improve β-lactam function - However, β-lactamase inhibitors are large and do not cross the BBB or other vascular regions with tight junctions - Cross reactivity between a newer β-lactam and PCN is less than 3% ⇒ allergy to PCN is not a contraindication to other β-lactam > When prescribing oral abx for wound dehiscence, **cefadroxil** attains more consistent skin penetration than cephalexin ##### Development and Coverage ![[Pasted image 20250220190013.png | 500]] ![[Pasted image 20250220191057.png | 500]] ![[Pasted image 20250220191105.png | 500]] ## Anti-anaerobe - **Metronidazole** - the preferred agent as it kill anaerobe and can cross the BBB - Clindamycin - CONS: - **bacterial-static ⇒ does not treat endocarditis, high treatment failure** - **large ⇒ does not cross BBB** - **high C diff risk** - Pro: fast acting mechanism of action → niche use for septic shock or necrotizing fascitis ## Other special notes - Rifampin - improves penetration of other abx (e.g. vanc) into biofilm and osteomyelitis by staph - easy to develop resistant to, use a few days after initial abx course to reduce colony size - TMP-Sulfa (Bactrim) - doesn't work well with pus in stasis #clinicalscience