L1. Introduction Flashcards
How many pathogenic bacterial species are described?
Less than 100 pathogenic bacterial species are described.
What percentage of bacterial diseases are caused by a small number of species?
1% of bacterial diseases are caused by several thousands of species, even though most infections are made up by the 100 described pathogenic species.
Does bacterial interaction occur in isolation?
No, bacterial interaction does not occur in a vacuum but only when interacting with a host (Nothing in this module happens in a vacuum, only when interacting with a host).
What happens during a real-life infection in terms of microbial presence?
During a real-life infection, there are lots of bacteria, fungi, archaea, etc., present in the environment, but the focus is on the one causing the disease; however, the others impact the infection massively.
How are non-pathogenic members of the normal flora described?
Non-pathogenic members of the normal flora are described as “commensals.”
Define commensalism.
Commensalism is an association between two organisms in which one benefits and the other derives neither benefit nor harm.
What is mutualism in the context of microbiota and an example?
Mutualism is a symbiotic relationship where both organisms benefit, such as the gut microbiome providing vitamin B12 and contributing to the calorie content of food.
How do gut microbiota benefit the host’s epithelial cells?
All energy supplied to epithelial cells comes from short-chained fatty acids produced by gut microbiota.
Describe a parasitic relationship in the context of microbiota.
A parasitic relationship causes slight harm to the host by using resources, but it is not too detrimental.
What can commensal organisms do under the right circumstances?
Commensal organisms can sometimes cause disease under the right circumstances, becoming opportunistic pathogens.
What is the focus of the module in terms of bacteria?
The focus is on bacteria that can become opportunistic pathogens.
What are the two possible outcomes of a pathogen infecting a host?
Asymptomatic carriage or disease development.
What is asymptomatic carriage?
When no symptoms of disease are shown, but the individual can still pass on the pathogen or even develop the disease later.
Give an example of an asymptomatic carrier.
Typhoid Mary.
Why don’t pathogens evolve to become less pathogenic?
It’s not in the pathogen’s interest to kill the host, but it makes no difference as once it can transmit and spread quickly, there is no selective pressure against death.
What happens if a pathogen isn’t good at transmitting?
Pathogenicity may decrease over time.
Why do some pathogens benefit from the host’s death?
Some anaerobes, like Clostridium tetanus, can’t live in the presence of oxygen and have evolved to kill the host, making the host an anaerobic fermenter (food source).
What are the two classes of virulence factors?
Factors for colonizing the host and factors that damage the host.
Name some virulence factors used for colonizing the host.
Adhesions, invasions, nutrient acquisition (e.g., Fe scavenging), motility, and chemotaxis.
Name some virulence factors that damage the host.
Exotoxins, endotoxins, proteases, DNase, lipase, and hemolysins.
How do host defenses push pathogens to become more asymptomatic or lead to recovery from disease?
Through physical barriers, innate immunity, and adaptive immunity.
What are the components of innate immunity that help fight pathogens?
Complement secretion, macrophages, and antimicrobial peptides.
What role do physical barriers play in host defense?
Skin and gut epithelium prevent bacteria from accessing more nutrients and usually need to be damaged for pathogens to enter.
What is the role of adaptive immunity in host defense?
B cells and T cells respond to pathogens, especially if the pathogen survives the initial innate immune response.