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18 Cards in this Set

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What does the term 'normal microflora' indicate?
Microorganisms usually found associated with human body tissue. Humans are colonized by microorganisms at birth.
Pathogen
Microbes that live on/in host and cause disease
Pathogenicity
The ability of a pathogen to inflict damage on the host
Virulence
Quantative measure of pathogenicity
Opportunistic pathogen
causes disease only in the absence of normal host resistance
Differentiate between the terms infection and disease.
Infection is a situation in which a microorganism is established and growing in a host, whether or not the host is harmed. Disease is damage or injury to the host that impairs host function
What are some factors that influence the composition of skin microflora?
Environmental factors such as weather and host factors such as age and personal hygiene
Saliva contains antimicrobial enzymes. However, we still harbor several microbes in our oral cavity. This statement is true/false? Explain.
True. The oral cavity is a complex, heterogeneous microbial habitat. High concentrations of nutrients near surfaces in the mouth promote localized microbial growth.
How do lactic acid bacteria contribute to tooth decay?
Lactic acid bacteria ferment sugars to lactic acid. The lactic acid dissolves some of the calcium phosphate in localized areas, and proteolysis of the supporting matrix occurs through the action of bacterial proteolytic enzymes. Bacterial cells slowly penetrate further into the decomposing matrix.
What is dental plaque made up of? Explain how dental plaque leads to dental caries.
Dental plaque is a mixed-culture biofilm. Microorganisms in dental plaque cause decalcification of the tooth enamel (dental caries).
What would happen if all microorganisms were completely eliminated from the gastrointestinal tract by the use of antibiotics?
Opportunistic infections can arise
What are some of the essential compounds made by the microorganisms in the intestinal tract?
Vitamins (B12 and K), gas, organic acids, odor and enzymes.
What are probiotics?
A live microorganism that when administered to a host, may confer a health benefit
Why are upper respiratory tract infections more common than lower respiratory tract infections?
The lower respiratory tract lacks microflora in healthy individuals.
What is the importance of Lactobacillus found in the urogenital tract of healthy adult women?
Produces lactic acid
What does the LD50 dose indicate? Explain how the LD50 test can be used to define virulence of a pathogen. (Explain fig. 27.14)
The virulence of a pathogen can be estimated from experiemental studies of the LD50 (lethal dose 50), the dose of an agent that kills 50% of the animals in a test group. Highly virulent pathogens frequently show the little difference in the number of cells required to kill 100% of the test froup as compared with the number required to kill 50%. Only a few cells of virulent strains of Streptococcus pneumoniae are required to establish a fatal infection and kill all mice in a test population. As a result, the LD50 for S. pneumoniae in mice is hard to determine. By contract, the LD50 for Salmonella enterica serovar Typhimurium, a much less virulent pathogen, is much higher. The number of cells of S. enterica ser. Typhimurium required to kill 100% of the population is more than 100 times greater than the number of cells needed to reach the LD50 and is propotionally related to the number of Salmonella cells introduced into the test mice.
Bacteria that initiate infection often adhere to host epithelial cells. Name some of the adherence factors/structures used by bacteria to do so.
Slime layer, capsule, fimbriae or pili
Differentiate between exotoxins and endotoxins. Which ones are generally considered less toxic and why?
Exotoxins are proteins released from the pathogen cell as it grows. Endotoxins are cell bound toxins. Endotoxins are generally less toxic than exotoxins, the lipopolysaccharide portion of the cell envelope of certain gram-negative Bacteria, which is a toxin when solubilized