Infections Flashcards
Dr. Idowu
Mention 5 characteristics of bacteria pathogens?
- Transmissibility
- Adherence to host cell
- Persistence
- Toxigenicity
- Invasion of host cells and tissue
- The ability to evade or survive the host’s immune system
Define adherence.
The process by which bacteria attach to the surface of host cells. It may also be referred to as adhesion or attachment.
Define the term “carrier”.
A person or animal with an asymptomatic infection that can be transmitted to another susceptible person or animal.
Define the term “infection”.
It is the invasion and multiplication of an infectious agent within the body.
Multiplication of bacteria that are part of normal flora in the GIT, skin etc., is generally not considered an infection.
Define the term “invasion”.
The process whereby bacteria, parasites, fungi, and viruses enter host cells or tissues and spread in the body.
What is microbiota?
Microbial flora harbored by normal, healthy individuals.
What is an opportunistic pathogen?
An agent capable of causing disease only when the host’s immunity is compromised.
Define pathogenicity.
Pathogenicity pertains to the ability of a infectious agent to cause disease.
What are super antigens?
These are protein toxins that activate immune response by binding to MHC molecules and T-cell receptors and stimulate T cells to produce copious amounts of cytokines.
What is toxigenicity?
The ability of a microorganism to produce a toxin that contributes to the development of disease.
What is virulence?
The quantitative ability of an agent to cause disease.
Virulent agents cause disease when introduced into the host in small numbers. Virulence involves adherence, persistence, invasion, and toxigenicity.
Highlight the Koch postulates.
- The microorganism should be found in all cases of the disease in question, and its distribution in the body should be in accordance with the lesions observed.
- The microorganism should be grown in pure culture in vitro (or outside the body of the host) for several generations.
- When such a pure culture is inoculated into susceptible animal species, the typical disease must result.
- The microorganism must again be isolated from the lesions of such experimentally produced disease
What is the adjunct to Koch postulates?
Development of a rise in specific antibody during recovery from disease is an important adjunct to Koch’s postulates.
Mention 2 exceptions to the Koch postulates.
- Treponema pallidum (syphilis) and Mycobacterium leprae (leprosy) cannot be grown in vitro; however, there are animal models of infection with these agents.
- There is no animal model of Neisseria gonorrhoeae (gonorrhea) infection even though the bacteria can readily be cultured in vitro
State the molecular Koch postulates.
Molecular cloning has allowed investigators to isolate and modify specific virulence genes and study them with models of infection.
1. The Phenotype or property under investigation should be significantly associated with pathogenic strains of a species and not with nonpathogenic strains.
2. Specific inactivation of the gene or genes associated with the suspected virulence trait should lead to a measurable decrease in pathogenicity or virulence.
3. Reversion or replacement of the mutated gene with the wild-type gene should lead to restoration of pathogenicity or virulence.