Intracellular Niche and Beta-Lactam Exclusion
intrinsic resistance
Obligate and facultative intracellular bacteria invade and persist within host cells (phagocytes, endothelium, epithelium), where they are shielded from antibodies, complement, and — critically for therapy — from antibiotics that cannot cross or accumulate within the eukaryotic cell membrane. The beta-lactams are the paradigm case: they diffuse poorly into and do not concentrate within host cells, so they are ineffective against intracellular pathogens even when the organism is susceptible in vitro. This is the gating principle that excludes cell-wall-active therapy for this class of infection.
Used by disorders
Brucellosis
as Facultative Intracellular Niche (Cell-Penetrant Drug Requirement)
Leprosy
as Intracellular Residence in Macrophages and Schwann Cells (Cell-Penetrant Drug Requirement)
Murine typhus
as Obligate Intracellular Niche (Cell-Penetrant Drug Requirement)
Oroya fever
as Intracellular Niche in Erythrocytes and Endothelium (Cell-Penetrant Drug Requirement)
Psittacosis
as Inhalation and Obligate Intracellular Chlamydial Infection
Q Fever
as Coxiella-Containing Vacuole Biogenesis and Dot/Icm Effector Secretion
Q Fever
as Inhalation and Intracellular Replication in Alveolar Macrophages
Scrub typhus
as Cytosolic Replication in an Obligate Intracellular Niche
Downstream
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Requirement for Cell-Penetrant Antimicrobials
Because the niche excludes poorly penetrant drugs, effective therapy is restricted to agents that accumulate intracellularly.
Show evidence (1 reference)
"The intracellular location of some microorganisms allow them to resist antibiotics with poor ability to penetrate eukaryotic cell membranes, such as the beta-lactam compounds."
Review of intracellular organisms stating that the intracellular niche confers resistance to poorly cell-penetrant antibiotics such as beta-lactams. Evidence source is OTHER as this is a review article.
Requirement for Cell-Penetrant Antimicrobials
therapeutic vulnerability
Therapeutic efficacy against intracellular bacteria tracks the intracellular concentration the drug achieves, not just its in vitro MIC. Tetracyclines (doxycycline), macrolides, fluoroquinolones, and rifamycins accumulate within host cells and are therefore the mainstays for rickettsioses, bartonelloses, brucellosis, Q fever, Legionella and Mycoplasma pneumonia, and chlamydial infection. This node is the cell-penetrant-drug requirement that conforming intracellular-infection treatments target; the drug's molecular target (usually the ribosome) is captured by the relevant target-based module.
Used by disorders
Melioidosis
as Intracellular persistence and eradication-phase requirement
Show evidence (1 reference)
"Therapeutic efficacy against intracellular pathogens has been correlated mainly with the intracellular concentrations achieved by the different antimicrobial agents."
Review of intracellular antibacterial pharmacokinetics establishing that efficacy against intracellular pathogens depends on the intracellular concentration achieved — the cell-penetrant requirement this node represents. Evidence source is OTHER as this is a review article.