Microbial Infection Flashcards
Micro-organism
Microscopic organisms, includes all unicellular organisms - bacteria/protozoa
Koch’s Postulates
4 Postulates
- The suspected pathogen must be present in all cases of the disease and absent from healthy animals.
- The suspected pathogen must be grown in pure culture.
- Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal.
- The suspected pathogen must be reisolated and shown to be the same as the original.
What are some limitations of Koch’s postulates ?
Some human diseases cannot be replicated in animal hosts.
Cannot be fulfilled for viruses that do not replicate in cell culture.
Infection
A disease caused by a pathogen
What is meant by normal microbiota ?
Microorganisms that are in every human being.
These are not harmful to humans; some are even beneficial and most help maintain our health.
Physical Barriers
Skin, Mucous
Chemical Barriers
Lysozyme, Sebum
Phagocytic Cells
Macrophages
Monocytes
Dendritic Cells
Mast Cells
Basophils
Eosinophils
Neutrophils
Commensal
A micro-organism which forms part of the normal host microbiota.
Pathogen
Micro-organism that can invade the body and cause disease
Pathogenicity
The ability to cause disease. (Qualitative)
Pathogenesis
The development of a disease
Virulence
A pathogen’s power to cause severe disease. (Quantitative)
What are the 7 virulence factors ?
Toxin secretion
Pilus formation
Adhesion factors
Capsule
Iron transport systems
Enzymes
Antibiotic resistance
What do virulence factors do ?
Help to :
- Invade the host
- Cause disease
- Evade host defences
What are the 2 types of pathogen ?
Obligate
Opportunistic / Conditional
Obligate pathogen
Almost always associated with disease
e.g. HIV
Opportunistic pathogens
Don’t always cause disease, but if given the chance can.
Immune-compromoised host
HAI
e.g. Staph A
e.g. Cryptococcus neoformans
Stages of Infection
Recognition
Attachment & Entry
Multiplication
Evasion of host defences
Shedding
Damage
Endogenous infections
Disease arising from a pathogen already present in the body but previously asymptomatic.
Exogenous infections
Disease arising from a pathogen not normally present in the body and comes from the environment.
Tissue tropism
The cells and tissues of a host that support growth of a particular virus or bacteria.
Transmission
The means by which contagious, pathogenic microorganisms are spread from one person to another.
Types of transmission
HUMAN TO HUMAN
Respiratory / Salivary spread
Fecal / Oral spread
Venereal spread
ANIMAL TO HUMAN
Vector
Vertebrae reservoir
Vector-Vertebrae reservoir
Fomite transmission
A fomite refers to inanimate objects that can carry and spread disease and infectious agents.
Examples of HAI’s
Staph A
C-Difficile
HAI
Hospital Acquired Infections
Are bacteria pathogenic ?
Most bacteria ARE NOT pathogenic
Examples of bacterial infection
Tuberculosis
Bubonic Plague
Staph A
Name 5 micro-organisms
Bacteria
Protozoa
Helminths
Fungi
Viruses
Name 2 protozoal infections
Malaria
Giardiasis
Name 2 fungal infections
Candidiasis
Cryptococcus neoformans
(Infection of the lungs and brain)
Name 2 helminth infections
Schistosomiasis
Trichuriasis / Whipworm infection
