Sources and Routes of Pathogens Flashcards
Nasal cavity, sinuses + upper respiratory tract
Staphylococcus spp, S. pneumoniae, H. influenza, B. catarrhalis, Virus - Influenza, Rhinovirus (common cold), measles, Chicken pox. Usually extrinsically acquired from other people via droplets/airborne/hand transmission.
Diseases of the UPT due to bacterial pathogens: Pharyngitis, Tonsillitis, Sinusitis → (spread to adjacent tissue) - middle ear infection, brain abscess, meningitis → (or spread to lower resp. tract) bronchitis, pneumonia, emphysema → ( both spread to blood stream) Bacteraemia.
Mouth
Streptococcus spp Lactobacilli,Actinomyces,Fusobacterium
Mouth droplet transmission: Tonsilitis - Strep. Pyogenes. + Meningococcal septicaemia - neisseria meningitidis invade nasopharynx → epithelial → endothelial cells.
Stomach:
Lactobacilli, Candida, Helicobacter pylori
SI/LI
E.Coli, Bacteroids ap., E.Coli, Shigella, Chlera, Salmonella, C.difficle
Disease consequences - diarrhoea, vomiting, dysentery - bloody doodoo (invasive infection. Bacteriaemic/systemic infections: typhoid, listeriosis, salmonellosis and septic arthritis
Skin (and mouth)
Staphylococcus epidermidis, Staphylococcus aureas. Portal of entry = surgery/wound, skin disease (eczema, burns, pressure sores), drug use, scratching insect bites, i.v. cannulae.
Diseases of skin + mouth = staphylococcus aureas, Streptococcus pyogenes, MRS. unusual = pasteurella multocida (dog bites), aeromonas hydrophilia (leeches), clostridium perfringens (soil).
These diseases can causes cellulitis (skin infection), abscess(pus buildup), fasciitis (inflam of fascia - connective tissue surrounding muscle, blood vessels + nerves), myoitis (inflam of muscles), gangrene, bacteraemia.
Lower Genital Tract+Vagina
Intrinsic sources = large intestine, extrinsic sources = bladder. Intrinsic sources affect UT via LI; E.Coli, Candida, Streptococcus, Bacteroides. Extrinsic Bacteria can infect UT: E.coli, Klebsiella spp.
Intrinsic pathogens that infect GIT: Streptococcus group B, Candida. Extrinsic infections that infect GIT: Gonorrhoeae, Chlamydia, Syphilis, HIV,HSV.
Diseases of the Urogenital Tract Infection: UTI: cystitis, pyelonephritis, GIT: gonococcal urethritis, pelvic inflam. Disease, tubo-ovarian abscess → both can spread to bloodstream = bacteraemia.
Expected vs Unexpected Routes?
Routes of infection can be expected: i.e. harmless microbiota entering via expected route e.g. newborn and maternal microbiota or Unexpected harmless microbiota entering unusual site or pathogenic microbiota entering any site
Difference between a True and Opportunistic Pathogen?
Pathogens cause disease - True pathogen = conditions dont need to be perfect for it to cause infection in any susceptible host. e.g.staphylococcus aureus from skin can cause large abscess and bacteraemia. Opportunistic pathogen = when the pathogen takes advantage of an opportunity not normally available, such as a host with a weakened immune system, an altered microbiota (such as a disrupted gut microbiota), or breached integumentary barriers
Pathogenicity?
Pathogenicity = ability to cause disease
