Microbiology and Parasitology

1. MC 3
MICROBIOLOGY AND
PARASITOLOGY
LESSON 10
INFECTION AND
HOST
RESISTANCE

2. Symbiotic Relationships Between Microbes and their Hosts
 Mutualism – both members both benefit from their interaction.
 Commensalism – one member of the relationship benefits without significantly affecting the other.
 Parasitism - a parasite derives benefit from its host while harming it, though some hosts sustain
only slight damage.
Normal Microbiota in Hosts
 Also called “normal flora” or the “indigenous microbiota” – microbes that colonize the surfaces of
the body without normally causing diseases.
 Resident Microbiota – remain a part of the normal microbiota of the person throughout life
 Transient Microbiota – remain in the body for only a few hours, days or months before
disappearing.

4. Infection and Microbial Invasiveness

5. Transmission or Spread of Infection

15. Specific Host Defense Mechanism
The Immune System
 Immunology - the scientific study of the immune system and immune responses.
 Immune Responses – involves complex interactions among many different types
of body cells and cellular secretions.
 There are two major arms of the immune system:
1. Humoral Immunity – always involves the production of antibodies, also known as
(AMI) antibody-mediated immunity
2. Cell-mediated Immunity – involves many different cell types including
macrophages, T helper cells, cytotoxic T cells, delayed hypersensitivity T cells,
(NKC) Natural Killer Cells, Killer cells and Granulocytes.