Bacterial Pathogenesis I – Flashcards
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GRAM + |
Staphylococcus Streptococcus Enterococcus Listeria Bacillus/Clostridia (spores) Corynebacterium Mycobacterium (do not stain; acid fast) Mycoplasma (no cell wall, do not stain) Actinomyces |
GRAM - |
Enterobacteriaeceae Salmonella Shigella E. coli Proteus Yersinia, etc Acinetobacter Pseudomonas; Burholderia Legionella Helico/Campylobacter Vibrio Rickettsia/Ehrlichia/Coxiella (obligate intracell. parasites) Neisseria/Haemophilus Bordetella/Brucella/Bartonella Francisella/Pasteurella Bacteroides |
Spirochetes |
Borrelia Treponema Leptospira Do not stain |
Chlamydia |
C. trachomatis C. pneumoniae Obligate intracellular parasites |
Normally Sterile Sites |
Blood
Internal organs (except stomach, intestines)
Bones Central nervous system/cerebral spinal fluid
Lymph |
Importance of Normal Flora |
1.Protect from colonization by pathogens by competition for space and nutrients and producing substances to inhibit other organisms 2.Help in maturation of immune system (exposure to many antigens- Natural antibodies) 3.Stimulate development of tissues (eg. Peyer’s patches) 4.Metabolism: Digest substances (cellulose, pectin, xenobiotics), synthesize substances (Vitamin K, B6, B12, short-chain fatty acids), remove by-products (H2à CH4) 5. Modulate response to epithelial cell injury 6.Can contribute to or modulate obesity 7.Alter ratios of bile salts in the intestinal tract |
Adverse Effects of Normal Flora
|
1.Some opportunistic (eg. Clostridium difficile; Staph. epidermidis) 2.Dental caries (Streptococcus spp.)/ periodontal disease (anaerobes); SBE 3.Autoimmunity from some natural antibodies |
Biofilm |
Biofilms: a complex community of microbes in a 3 dimensional structure, in which the microbes secrete carbohydrates to adhere tightly to inanimate objects and to each other |
Events that take place in all infections |
•Encounter: The agent meets the host •Portal of Entry: The agent enters the host •Spread: The agent spreads from the site of entry (localized vs systemic) •Multiplication: The agent multiplies within the host •Damage: The agent, the host response, or both cause tissue damage •Outcome: The agent or the host is eliminated, or persistent infection occurs |
Portals of Entry |
Respiratory Tract Streptococcus pneumoniae GI Salmonella enterica Mucous Membranes Neisseriameningitidis Skin Staphylococcus aureus
Genitourinary Tract Neisseriagonorrhoeae Blood Arthropod-borne- Yersinia, Rickettsia
Borrelia, Malaria, West Nile Virus |
Vehicles of Transmission |
Fingers
Food
Feces
Flies
Fomites
Fucking |
Extracellular Pathogens |
–Restricted to extracellular environments •Must avoid phagocytosis •Must resist complement-mediated killing •Many produce exotoxins •May be tissue invasive but remain extracellular e. g.Staphylococcus aureus, Vibriocholerae, Pseudomonas |
Facultative Intracellular Pathogens |
–Can grow extracellularly –Can penetrate and grow within a variety of host cells •Specialized facultative intracellular- can grow within nonphagocytic cells but are killed by macrophages •Generalized facultative intracellular-can grow in normal macrophages but usually killed by activated macrophages •e. g. Salmonella, Mycobacteria, Listeria, Shigella |
Obligate Intracellular Pathogens |
–Require viable host cells for growth e. g., Rickettsia, Chlamydia Some protozoa; ALL VIRUSES |
