Introduction Flashcards
Purposes of Clinical Microbiology
- control epidemics
- prevention
- treat infections
invasion by and multiplication of microorganisms in body tissue
infection
alteration that disrupts normal body function
disease
Causes of disease
- pathogens
- inheritance
- environment
Types of pathogens
- prions
- viruses
- bacteria
- fungi
- parasites
Ways to acquire infections
- nosocomial (hospital) infections
- community-acquired infections
- endogenous infections
- exogenous infection
non-infectious organisms
- normal flora
- opportunists
- contaminants
Germ Theory
- suggested by Louis Pasteur and Robert Koch
- first to say that diseases are caused by microorganisms
Koch’s Postulates
- pathogens are found in sick organisms, not healthy ones
- pathogen must be isolated and grown in pure culture
- purified pathogen should cause same disease when injected in a new host
- injected pathogen should be re-isolated and identical to the original
Body as a growth environment
- has nutrients
- moist, watery environment
- optimal temperature
- supports flora and pathogens
Disease process
- enter body
- disrupt function
- cause symptoms
Signs of infection
fever, chills, fatigue, weight loss, vasodilation, increased WBC count, abnormal peripheral blood differential, increased sedimentation rate type-specific antibodies
sedimentation rate
rate at which RBC’s settle out of blood in one hour; altered by inflammatory proteins, making RBC’s heavier and faster to fall
Modes of infection transmission
- direct transmission
- indirect transmission
direct transmission of infection
- congenital, sexual and physical contact
- hand-to-hand contact with body secretions and respiratory droplets
indirect transmission of infection
- contaminated food & water
- fomites
- airborne
- animals
- insects/arthropods
How infections disrupt body function
- produce toxins
- remove nutrients
- destroy tissue
Types of toxins
neurotoxins, cytotoxins, enterotoxins, endotoxins
Ways to fight infection
- prevention
- antibiotics, anti-fungals, anti-viremic, anti-parasitics
- host defense mechanism (immune system)
Purpose of the Immune System
- protection
- prevent disease
- destroy disease-causing agent
Components of the Immune System
- non-specific defenses
- specific defenses
Components of non-specific defense
- 1st line of defense (physical barriers)
- 2nd line of defense (inflammatory response)
1st Line of Defense
physical barriers, chemical barriers (i.e., sweat), secretions containing lysozymes, reflexes, secretions
2nd Line of Defense
inflammatory response to allow WBC’s to enter site of infection, WBC production, fever, interferon
What happens during an inflammatory response?
blood vessels near wound expand, WBC’s leak from vessel into infected tissue and engulf bacteria (phagocytosis)
Why is fever involved in the 2nd Line of Defense immune response?
- increased temperature isn’t ideal for some pathogens
- increases heart rate, allowing WBC’s to travel to site of infection more quickly
- increases rate of chemical reactions, to help repair tissue damage
interferon
antiviral that blocks viral replication by inhibiting the synthesis of viral proteins
Specific immunity
- immune response triggered by an antigen that involves phagocytosis of the antigen cells
- divided into cell-mediated immunity and humoral immunity
What is an antigen?
carbohydrates, lipids and proteins on the surfaces of bacteria, viruses, parasites and fungi
What is the function of monocytes/macrophages in the immune response?
phagocytosis; antigen presenting cells
What is the function of granulocytes in the immune response?
- Neutrophils: phagocytosis, inflammation
- Eosinophils: allergies, helminth destruction
- Basophils: allergic reactions (IgE receptors)
What is the function of lymphocytes in the immune response?
- T cells: cellular immunity, helper/cytotoxic or suppressor functions
- B cells: antibody production
- Large granular lymphocytes: natural killing
What is the function of mast cells, Langerhans cells, and Dendritic cells in the immune response?
- Mast cells: allergic reactions
- Langerhans cells: antigen presenting cells in skin
- Dendritic cells: antigen presenting cells in lymph tissue
Humoral Immunity
Deals with viral and bacterial infections
Cell-mediated Immunity
Deals with protozoal and some bacterial infections
Ways to classify organisms
- prokaryotic or eukaryotic
- size and physical properties
- characteristics (i.e., cell wall)
- site of infection in the body