Chapter 13 Collaborative Flashcards
What does normal resident microbiota mean?
Microbes that engage in mutual or commensal associations with humans
What is an infection?
A condition in which pathogenic microbes penetrate host defenses, enter tissues, and multiply
What is a pathogen?
A microbe acting as an infectious agent
What is an infectious disease?
An infection that causes damage or disruption to tissues and organs
What are transients?
Microbes that occupy the body for short periods. Influenced by hygiene, they don’t grow but just cling to the surface
What are residents?
Microbes that become established, stable, predictable, less influenced by hygiene. Primarily bacteria and yeasts
What is microbial antagonism?
When microbiota benefits the host by preventing overgrowth of harmful microbes
What are endogenous infections?
They occur when normal flora is introduced to a site that was previously sterile
What sites harbor normal resident microbes?
Skin and continguous mucous membranes, upper respiratory tract, gastrointestinal tract, outer opening of urethra, external genitalia, vagina, external ear and canal, external eye
What are some sterile (microbe-free) anatomical sites and fluids?
Blood, urine in kidneys, ureters, bladder, CSF, saliva prior to entering oral cavity, semen prior to entering urethra
Where are the most diverse and unique flora of the body located?
In the mouth
What kind of bacteria grow best in the intestines?
Anaerobic bacteria, such as Bacteroides, Bifidobacterium, Fusobacterium, Clostridium
What are probiotics?
Supplements to introduce known microbes back into the body
How do resident microbiota work?
They’re generally stable mitrobiota that usually benefit the host by preventing overgrowth of harmful microbes - microbial antagonism
How is resident flora first introduced to a person?
Breaking of the fetal membrane just before birth, and subsequent handling and feeding of the newborn
Most common residents of the mouth?
Aerobic Streptococcus species. Such as S. sanguis, S. salivarius, and S. mitis
How many microbes are found in feces?
More than/equal to 30% of fecal volume
How can microbes of the large intestine benefit the host?
Fermentation of waste materials in feces generates vitamins and acids, and bacterial digestive enzymes can convert disaccharides to monosaccharides or promote steroid metabolism
What flora are in the nasal entrance to the anterior nasopharynx?
S. aureus
What flora are in the mucous membranes of the nasopharynx?
Neisseria
What flora are found in the tonsils and lower pharynx?
Haemophilus
What sites harbor microflora in the genitals of females and males?
Females - vagina and outer opening of urethra
Males - anterior urethra
How are internal reproductive organs kept sterile?
Physical barriers, such as a cervical plug
How are the kidney, ureter, bladder, and upper urethra kept sterile?
By urine flow and bladder emptying
How do normal flora assist the body?
They create an environment that may prevent infections and enhance host defenses
What factors can weaken host defences and increase susceptibility to infection?
Old age and extreme youth, genetic and acquired defects in immunity, surgery and organ transplants, organic disease, chemotherapy/immunosuppressive drugs, physical and mental stress, other infections
What are the 2 types of pathogens?
True pathogens and opportunistic pathogens
What are true pathogens?
Capable of causing disease in healthy persons with normal immune defenses.
Influenza virus, plague bacillus, malarial protozoan
What are opportunistic pathogens?
Cause disease when the host’s defenses are compromised or when they grow in a part of the body that is not natural to them.
Pseudomonas sp. and Candida albicans
What is virulence factor?
A characteristic or structure that contributes to the ability of a microbe to cause disease; anything that allows organism to cause disease.
Ex: slime layer/capsule, fimbriae in E. coli
What are exogenous agents?
Flora originating from a source outside of the body
What are endogenous agents?
Flora that already exist in or on the body. Normal flora
What is STORCH?
Pathogens that can infect during pregnancy and become dangerous
What is an infectious dose?
The minimum number of microbes required for infection to proceed. Inversely related to virulence.
How are infectious dose and virulence factor related?
They are inversely related. A microbe with a high infectious dose will have a low virulence factor, meaning it cannot easily cause disease and must have a high number of organisms to do so. Likewise, a microbe with a low infectious dose has a high virulence factor since it can easily cause infection.
What is the difference between infection and infectious disease?
Infection is pathogenic microbes penetrating a host’s defenses, an infectious disease is an infection that causes damage or disruption
What are antiphagocytic factors?
Factors used to avoid phagocytosis (to survive host defenses)
What are leukocidins?
Factors toxic to white blood cells, to help survive host defenses
What is the slime layer or capsule?
A factor that makes phagocytosis difficult. To help survive host defenses
What is a toxin?
A specific chemical product of microbes, plants, and some animals that has poisonous effects on other organs
What are toxinoses?
Adverse effects of toxins
What is toxemia?
When a toxin is spread by the blood from the site of infection (like tetanus)
What is intoxication?
Caused by ingestion of toxins. Like botulism
What are the types of bacterial toxins?
Endotoxin and exotoxin
What is an endotoxin?
A toxin that is not secreted, but released after the host cell is damaged or killed
What is an exotoxin?
A toxin that is secreted by a LIVING bacterial cell into the infected tissue
What are the 4 stages of clinical infections?
- Incubation period
- Prodromal stage
- Period of invasion
- Convalescent period
What happens during the incubation period of a clinical infection?
First stage. Time from first contact w/ infectious agent to the appearance of the first symptoms. Microbe is multiplying but no symptoms
What happens during the prodromal stage of a clinical infection?
Second stage. Vague feelings of discomfort, nonspecific complaints
What happens during the period of invasion in a clinical infection?
Third stage. Microbe multiplies at high levels, become well-established, more specific signs and symptoms
What happens during the convalescent period of a clinical infection?
Fourth and final stage. As person begins to respond to the infection, symptoms decline
During which stage of a clinical infection can the disease be transmitted?
ANY stage. Also, the number of microbes is directly related to the intensity of the symptoms
What is a sign?
Objective evidence of disease noted by an observer
What is a symptom?
Subjective evidence of disease sensed by the patient
