OCCC – Mbio 3813 Unit 3

Normal Flora
Microbes that are normally found in humans
when microbe penetrates host defenses, invades sterile tissues, and multiplies
Microbes are considered a __________
Infectious disease is when infection causes:
damage or disruption to tissues and organs
Normal Flora Sites
Upper Resp. Tract
GI Tract
Outer urethra
External genitals
External eyes and ears
Sterile Sites
Internal organs
Brain and spinal cord
Middle and Inner ear
Inner eye
Blood, urine, other fluids.
Normal Flora of skin
Only on dead layers of epidermis, gland and follicles

Sterile below Dermis layer

Normal Flora of GI Tract
Epidermal layer of cheeks, gum
Teeth surface
Saliva (large numbers)
Mainly Anaerobes
Normal Flora of Respiratory Tract
All places EXCEPT bronchi, bronchioles, alveoli
Normal Flora of Eye
Normal Flora of Ear
External ear: similar to skin
Middle and Internal ear: sterile
Define: Pathogenicity
describes an organism’s potential to cause infection or disease
Define: True pathogens
pathogens capable of causing disease in healthy persons with normal immune defenses
Define: Opportunistic pathogens
Pathogens that cause disease when host defenses are compromised or when become established in a part of body not normal to organism
Define: Virulence
measurement of degree of pathogenicity

used to determine ability to establish in host and cause damage

Define: Virulence factor
Any characteristic or structure of microbe that contributes to the disease state
Process of a Disease: From portal of entry to portal of exit
Portal of Entry
Infection of Target
Portal of Exit
Event: Portal of Entry
microbe enters body
cutaneous or membranous boundary
outside or latent infection
Event: Adhesion
Microbes gain more stable foothold at portal of entry
Once stable, and attached, pathogen invade body compartment
Event: Resistance of host defenses
Phagocytes (WBC) engulf pathogen and destroy via enzymes and antimicrobial chemicals
Pathogen’s way of avoid phagocytes:
antiphagocytic factors (virulence factor)
Ways for pathogen to avoid Phagocytes:
Produce leukocidin

Secrete extracellular surface slime or capsule layer

Adapt to hide, survive, and grow within phagocytes

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