chapter 14 study guide BIO205

Normal microbiota colonize parts of body without causing disease – resident or transient

both - some are mutualistic – bacteria in colon that produce vitamins, some are commensal – Staphylococcus epidermidis)

• many kinds...400-1000
• 400-1000 kinds in large intestine

some remain residents of body for life, some are transient)

skin, digestive tract, upper parts of respiratory tract, lower parts of urinary and reproductive tracts -urethra, vagina

during childbirth, during feeding, during handling

normally don't, but may cause opportunistic infection

when a person is sick, malnurished, under stress, etc

when a person starts using an antibiotic it may kill some nonpathogenic flora, allowing more pathogenic microbes to thrive

from rectum to urethra

(zoonoses) rabies carried by many mammals - transferred to humans by animal bite 

people who are actively sick; people who are not actively sick (asymp-tomatic), but still carry the pathogen; people who don't become sick, but still carry the pathogen

• soil – fecal contamination (Clostidium),
• water – contamination from feces or urine –
• = protozoans (Giardia), bacteria (cholera), =
• food – fecal or other contamination
• of meat, fruits, vegetables (E.coli)

• Contamination - presence of microbes in or on the body - may do no harm
• Infection - microbes multiply, become established in the body - may or may not cause disease
• Disease - loss of normal body function= morbidity, any change from state of “health” 

outer layer is thick layers of tightly packed, dead, dry cells(good barriers for most microbes) enter through hair follicles, sweat glands, abrasion, cuts, bites, scrapes, stab wounds.

Respiratory tract

2% of pregnancies, pathogens cross the placenta into embryo

A means by which portals of entry are circumvented(punctures by nails, thorns, hypodermic needles)

• Adhesion is necessary for successful infection by pathogen; loss of adhesion facto results in loss of pathogenicity
• Pathogens have adhesion factors- attachment structures of bacteria and viruses  

•                         examples: ligands - proteins, lipoproteins, glycoproteins
• bind to receptors on host

•                                     "Adhesins"
• of bacteria on fimbriae, flagella,  or glycocalyces

•                                     "Attachment
• proteins" of viruses

• Whooping cough pathogen (Bordetella) has more than one type of adhesin
• Malaria (Plasmodium) changes adhesins over time

subjective characteristics of a disease, felt by patient alone. ex: headache, pain, dizziness, fatigue

objective manifestations of disease that can be measured or observed by others.

group of signs and symptoms that characterize a particular disease.

• Purpose: to determine the causative agent of a disease.
• These 4 postulates must be satisfied in order:
• 1) Pathogen must be present in all cases. 2) Pathogen must be isolated and grown in pure culture.
• 3) Cultured pathogen must cause disease in health susceptible host.
• 4) Same pathogen must be re-isolated from diseased experimental host.
• Exceptions: 
• 1)Some pathogens cannot be cultured in the lab (Mycobacterium leprae)
• 2)Some diseases caused by a combination of pathogens, or pathogen plus physical or            genetic factors.

• Pathogenicity - ability to cause disease
• Virulence - a measure of the relative ability of a pathogen to infect a host and cause disease = degree of pathogenicity - not a measure of severity of disease.

• 1) Ability to enter host
• 2)Adhere to host cells
• 3)Gain access to nutrient
• 4)Escape detection/removal by immune system
• 5)Extracellular enzymes
• 6)Toxins
• 7)Antiphagocytic factors

These enzymes help microbes move deeper into tissues, andavoid body defenses

breaks down hyaluronic acid

- breaks down collagen

coagulates blood, providing a “hiding place” within the clot

break down blood clots

Toxins are chemicals that damage tissues or trigger immune response that causes damage          to tissues

kill host cells

interfere with nerve function

affect cells lining the GI tract

Lipid portion of lipopolysaccharide (outer bacterial membrane)

• Capsules - composed of chemicals normally found in the body - don't stimulate immune response
• Antiphagocytic chemicals - prevent fusion of lysosomes with phagocytiv vesicles
• M protein produced by Struptococcus pyogenes
• Leukocidins- destroy pathogen

• 1) Incubation period
• 2)Prodromal period
• 3)Illnes
• 4)Decline
• 5)Convalescence

Time between infection and occurrence of first symptoms or signs of disease

Generalized, mild symptoms that precedes illness

Most severe stage of thedisease

• Body gradually returns to normal
• Immune response peaks during this period
• If patient doesn’t recover, then he dies

• Patient recovers from illness- Tissues
• are repaired and returned to normal
• Length depends on Amount of damage, Nature of the pathogen, Site of infection, Overall health of the patient

• Time between infection and occurrence of disease
• 1,vurulence
• 2)Infective dose
• 3)State and health of host's immune system
• 4)Nature of pathogen
• 5)Generation time
• 6)Site of infection

by touching, phiscal contact, pregnancy

fomites (needles, toothbrushes, toys, money)

coughing, sneezing - less than 1 meter

farther than 1 meter -air conditioners, sweeping, changing bed linens,                                           flaming inoculating loops

contaminated water - fecal-oral route

inadequate cooking, poorly refrigerated, fecal-oral route

blood, saliva, urine outside the body - comes in contact with breaks in skin or mucous membranes

- transmits pathogen, serves as host, biting arthropods

- not required as hosts by pathogens, carry pathogens on feet or other body parts