Lecture 13 Flashcards
Resident microbiota
Includes bacteria, fungi (yeasts), and Protozoa that are on most areas of the body that are in contact with the outside environment like the skin, upper respiratory tract, GI tract, urogenital tract
Benefit of resident microbiota
Prevent overgrowth of pathogenic microbes
Resident microbiota examples
Lactobacillus in the vagina keep pH low by fermenting glycogen preventing the overgrown of candida, E. coli in the large intestines secrete bacteriocins that prevent the overgrowth of bacteria like salmonella and shigella
Resident microbiota examples
Lactobacillus in the vagina keep pH low by fermenting glycogen preventing the overgrown of candida, E. coli in the large intestines secrete bacteriocins that prevent the overgrowth of bacteria like salmonella and shigella
Resident microbiota found
Skin, respiratory tract, gastrointestinal tract, external genitalia, vagina, external ear and canal, eye lids and lashes
Sterile sites and fluids
Organs including bones, brain, bladder, blood, urine, cerebrospinal fluid
Portal of entry
Characteristic routes that infectious microbes enter the body through, every microbe has a specific one
Exogenous
Infectious agent originates from source outside the body
Endogenous
Infectious agent already exists on or in the body
What have most pathogens adapted to
A specific portal of entry
Some pathogens
Can enter by more than one portal of entry to cause different infections
Infectious dose
The minimum number of microbes to be inoculated into the host for infection to proceed, varies for each organism
Ghonnorea
1000 Neisseria ghonnorea cells, through sexual contact
Measles
1 measles virus, through respiratory
Typhoid fever
10,000 salmonella typhi, through ingestion of fecal contaminated food or water
Cholera
1 million vibrio cholera, through ingestion of fecal contaminated water
Adhesion
The process by which microbes gain a stronger foothold at the portal of entry
Fimbriae
Short hair-like structures used in adhesion
Capsules
Extracellular slime or stocky layer used in adhesion
Viral spires
Attach to host receptors1 adhesion structure
Hooks or flagella
Used for attachment/adhesion
Virulence
Ability of microbes to invade a host, produce substances to evade host defenses, and bring damage to the host
Virulence factors
Substances that improve the microbe’s ability to establish an infection and promote their invasiveness
Virulence factors include
Physical structures, exoenzymes, antiphagolytic factors, and endo and exo toxins
Exoenzymes
Used to get deeper into the host, enzymes made and secreted by microbes that disrupt the structure of the hosttissue
Keratinase
Exoenzyme secreted by dermatophytes to digest the principal component of hair and nails
Mucinase
Exoenzyme, factor in amoebic dysentery, digests principal component of mucus membranes
Hyaluronidase
Secreted by staphylococcus and streptococcus to digest hyaluronic acid which is the ground substance cementing animal cells together
Antiphagocytic factors
Leukocidins, glycocalyx, and intracellular survival
Leukocidins
Toxic Substances Secreted by virulent strains of staphylococcus and streptococcus that kill WBCs
Punch holes causing cells to lyse
Glycocalyx
Extra cellular surface layers make it physically difficult for phagocytes to engulf them ( strep. pneumoniae, Neisseria meningitidis, Cryptococcus)
Intracellular survival
Some bacteria are well adapted to survive inside phagocytes like chlamydia, mycobacterium, listeria, etc
Toxins
Chemical products of an organism that have poisonous effects on other organisms
Exotoxins
Secreted by a living bacteria cell into the infected tissue ( usually targets specific tissue)
Endotoxins
Not secreted, released after the cell is damaged or lysed
Usually found in cell wall and released upon death causing fever, shock, watery eyes etc
Exotoxin properties
Made of small proteins, produced by gram neg and pos, released by live cells, toxic in small amounts, can be destroyed by heating, ingesting toxin or toxin secreted into tissues, specific to a cell type, quick illness variable recovery
Food poisoning, diarrhea, paralysis, tissue damage
Endotoxin properties
LPS and techoic acids, lipid/sugar based, LPS gram neg and TA gram plus, released from cell wall during lysis, toxic in higher doses, stable at higher temps, systemic
Inflammation, bleeding, GI problems, shock
Long incubation and recovery
Incubation period
Time from initial contact with the pathogen to the appearance of the first symptom
Majority of infections range 2-30 days
Prodromal stage
Short period 1-2 days when the earliest notable symptoms appear
Fatigue, head and muscle aches, upset stomach
Period of invasion
Pathogen multipliesat high levels, exhibits greatest toxicity, becomes well established in target tissue
Convalescent period
If patient doesn’t die, respond to infection and symptoms decline, can be dramatic or slow recovery
Localized infection
Pathogen confined to specific tissue
Examples: boils, warts, fungal skin infection
Systemic infection
Infection spreads to several sites through blood and lymph fluid
Examples: viral diseases like measles and chickenpox, secondary syphillis, cryptococcosis in hiv/aids
Focal infection
Infectious agent breaks loose from local infection and is seeded or disseminated into other specific tissues
Examples: mycobacterium tuberculosis, Streptococcus pyrogenes,
Mixed infection
Same site infected with several microbes at the same time
Examples: animal or human bite infections, wound infections
