10.6.7 Neurological infections
Bacterial infections of the central nervous system
are uncommon, but can have a devastating impact
(Table 10.9). Accessibility to the site of infection for
collection of diagnostic specimens, and administration
of antimicrobials, is highly variable. The BBB
and blood–cerebrospinal fluid barriers have a major
impact on the penetration of most drugs. In general,
drugs that are lipid soluble, non-ionized, not highly
protein bound and small molecular size, penetrate better. Nevertheless, even drugs with these properties
often poorly penetrate the CNS because the main
determinant of the BBB passage is the presence
of efflux pumps (i.e. P glycoprotein, MRP, etc.).
Inflammation can result in increased drug penetration,
however this cannot necessarily be relied on,
so treatment choices should be based on knowledge
of the aetiologic agent and drug penetration.
Aminoglycosides penetrate poorly even in the presence
of inflammation, however they are often used in
combination therapy. Unlike other third-generation
cephalosporins, central nervous system (CNS) penetration
of ceftiofur is poor (22).