How and Where to Infectious Agents Get Into Tissues?
The signs and symptoms may point to a particular site or organ system:
Ingested into the gastrointestinal tract, with abdominal pain, nausea, vomiting, diarrhea, melena - micro-organisms contaminating food or water (Shigella, Salmonella, Vibrio cholerae) Inhaled into the respiratory tract, with cough, chest pain, dyspnea, hemoptysis - micro-organisms in the air that is breathed Ascend into the urinary tract, with dysuria, hematuria, pelvic pain, flank pain - micro-organisms that get into the bladder via the urethra (or via a catheter) and can ascend as far as the kidneys Ascend into the biliary tree, with vague abdominal pain, jaundice - micro-organisms that gain access to the common bile duct from the gastrointestinal tract and can ascend as far as the intrahepatic ducts of the liver Cross mucosal surfaces, with local irritation, ulceration, pain, or late sequalae only - micro-organisms penetrate oral, anal, genital, or conjunctival mucosae (human papillomavirus, human immunodeficiency virus, herpes simplex virus, Neisseria gonorrheae)
Trauma - direct spread - micro-organisms are directly inoculated into
wound sites
How do they spread within the body?
Travel via the bloodstream - septicemia
Travel via the lymphatics - enlarged, tender lymph nodes suggest possible
infection at the site from which the lymphatics drain
Travel via a body cavity - can spread in the CSF, peritoneal fluid, joint
space, etc.
Cross the placenta to the fetus - basis for congenital infection
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