| 病原 | 線索 |
| Mycobacterium tuberculosis | Acid-fast、Th1 granuloma |
| Chlamydia | Obligate intracellular、NAAT、STI |
| Rickettsia/Orientia | Tick/chigger、rash/eschar、doxycycline |
| Coxiella | Q fever、culture-negative endocarditis |
| Mycoplasma | No cell wall、walking pneumonia、cold agglutinin |
| Legionella | Water aerosol、hyponatremia、diarrhea |
