question

Normal resident flora (biota)

answer

refers to large array of microorgs that favorably inhabit the human body in abundance

A) Total cells in human body = 1013

B) Total bacteria in the mouth = 1010

C) Total bacteria on the skin = 1012

D) Total bacteria in the G.I. tract = 1014

question

Acquiring resident flora

answer

A) Microbes accumulate over time immediately following birth by simple interaction w/ environment
B) Microbes are found almost everywhere on & in body but more prominent in locations exposed to environment (skin & GI tract)
C) Levels of specific microbes can fluctuate a great deal up & down but normally stay relatively constant
1) Competition w/ other organisms & repeated interaction w/ environment play a role in this balance
D) Some pathogens can be found in normal flora but generally don’t cause
problems BC competition limits their growth
1) In compromised state,can cause problems = opportunistic pathogens
E) The flora even plays a role in the body’s defense by producing antibodies & inhibiting entry & growth of other pathogens

question

Initial colonization

answer

A) The uterus is normally sterile during development
B) As fetal membrane breaks, microbes in the vagina can enter womb & begin to colonize the skin
C) During the birth the baby is exposed to an even larger # of microbes
D) Colonization of resp. system begins w/ the baby’s first breath
E) Exposure continues as baby comes into contact w/ mother, other family,
hospital staff, etc.
F) Colonization of intestines begins during first feeding
1) The microbes vary dependent on whether the baby is bottle or breast fed
G) Stabilization of eventual adult flora occurs following weaning, the intro of solid food, & eruption of teeth

question

Flora of specific regions

answer

1. Skin
2. GI tract
3. Respiratory tract
4. Urogenital tract

question

Skin region

answer

A) Flora resides on or in the skin layer
B) Dryness of the skin, humidity, occupational exposure, & clothing influence make-up of flora
C) A very rich flora community is located at regions where the skin joins w/ the mucus membrane
D) 2 distinct populations: transient & resident

question

Transient flora (skin)

answer

a) clings to the surface but doesn’t usually grow there

b) acquired during routine exposure to the environment or other people

c) is drastically influenced by hygiene

question

resident flora (skin)

answer

a) inhabits deeper portions of the epidermis and in glands and follicles

b) population is more stable and predictable and less influenced by hygiene

c) primarily composed of bacteria (usually Staphylococcus sp.) & fungi (Candida albicans)

question

Flora of mouth & esophagus

answer

1) Streptococcus species is most common

question

Flora of stomach

answer

Helicobacter pylori is the only known bacteria that can live in the stomach

question

flora of large intestine and rectum (enterics)

answer

Almost entirely composed of anaerobes

a) Bacteroides, Fusobacterium, & Clostridium are prevalent

b) Coliforms, including E. coli, Enterobacter, and Citrobacter are found in smaller numbers

i) coliforms – Gram-negative, lactose-fermenting, facultative anaerobic bacteria found in the colon
ii) Contribute to intestinal odor & discomfort caused by lactose intolerance

question

Flora of respiratory tract

answer

A) Primarily seen in upper respiratory tract and varies in different regions of the respiratory pathway
1) nasal entrance – Staphylococcus
2) nasopharynx – Neisseria
3) oropharynx – Streptococcus
4) laryngopharynx & tonsils –Haemophilus

B) Conditions in the lower respiratory tract are unfavorable for permanent residents

question

Flora of urogenital tract (urethra)

answer

1) Usually sterile but can sometimes find nonpathogenic Streptococci,
Staphylococci, & occasionally coliforms
2) The shorter female urethra contributes to increased susceptibility to urinary tract infections (UTI’s)

question

flora of the urogenital tract (vagina)

answer

1) Before puberty
a) Staph, Strep & Candida are common
b) pH is about 7
2) After puberty
a) Estrogen causes the vaginal mucosa to secrete glycogen which is fermented
by bacteria releasing lactic acid
b) pH lowers to about 4.5
i) Thought to prevent the establishment of microbes that could be harmful to a developing fetus
c) Lactobacilli becomes prevalent bacteria; Candida is still present
3) After menopause flora & pH return pre-puberty levels

question

Pathogenicity

answer

A) Refers to a microorganism’s potential to cause an infection or disease
1) True pathogens are microbes with the ability to cause disease in individuals with
normal immune systems
2) Opportunistic pathogens cause disease when the defenses are compromised

question

Virulence factors

answer

A) Properties that enable a microbe to invade and infect a host

B) Virulence
1) The ability of a microbe to cause infection that takes the presence or absence of
virulence factors into account

question

Portal of entry

answer

A) The characteristic route that a microbe takes to enter body tissues
1) Exogenous agents enter the body from the outside environment; ex. common cold
2) Endogenous agents already exist in the body; ex. candidiasis (yeast infection)

B) Many pathogens only cause disease when they enter through a specific portal

question

Skin as a portal

answer

1) Most pathogens enter through damaged areas in the skin

2) Some can burrow through the skin or enter through insect bites

3) The conjunctiva is also susceptible to infection

question

GI tract as a portal

answer

1) A large number of microbes enter through the mucus membranes

2) The rectum isn’t a normal portal of entry for microbes but may become a portal with individuals who practice anal sex

question

Respiratory tract as a portal

answer

Smaller microbes are more likely to enter through this portal

question

Urogenital tract as a portal

answer

1) The agents of sexually transmitted diseases and urinary tract infections (UTI’s) enter here

2) Some enter directly through the skin (broken or unbroken); others enter via the urethral mucosa or vaginal lining

question

Adhesion

answer

Process by which microbes gain a more stable position in the body

a) Bacteria attach via fimbrae, flagella, pili, slime layers, capsules

b) Virus often attach to a specific receptor on the cell surface; may involve specific viral proteins (spikes)

c) Protozoa use their structures of locomotion to burrow into the host cell

d) Worms mechanically fasten using suckers, hooks or barbs

question

Tissue damage

answer

Often caused by a microbe’s virulence factors

1. enzymes

2. bacterial toxins

question

Enzymes (tissue damage)

answer

i) Directly inflict tissue damage
ii) Breakdown a host’s defenses and allow the microbe to move deeper into
the tissue

question

Mucinase

answer

digest the protective coating on mucus membranes

question

Keratinase

answer

digests keratin, a primary component of skin, hair, and nails

question

collagenase

answer

digests the collagen fibers of connective tissue

question

Hyaluronidase

answer

digests the component holding animal cells together

question

Bacterial toxins

answer

i) Toxin is any chemical that is poisonous to another organism
(a) Exotoxin – released by living bacterial cells into infected tissue
(b) Endotoxin – released when the bacteria is damaged or destroyed

question

Exotoxin

answer

released by living bacterial cells into infected tissue

question

Endotoxin

answer

released when the bacteria is damaged or destroyed

question

Neurotoxins

answer

damage nervous tissue
(i) ex. tetanospasmin and anthrax toxin

question

Enterotoxins

answer

cause symptoms associated with intestinal disturbances
(i) ex. cholera & shiga toxina

question

Cytotoxins

answer

damage a variety of cells by damaging cell membranes or interfering with metabolism

(i) ex. streptolysin and other hemolysins

question

Localized infection

answer

1) A single microbe enters the body and remains confined to a specific tissue
2) Examples: boils & fungal skin infections
3) Mixed infection

a) Several microbes establish themselves simultaneously at the infection site

b) Examples: dental caries, wound infections and human bite infections

question

Systemic infections

answer

1) An infection spreads to several sites and tissue fluids usually in the bloodstream

2) Examples: viral diseases such as measles, chickenpox and AIDS, and bacterial diseases such as diphtheria, typhoid fever and syphilis

question

Localized infection

answer

1) A single microbe enters the body and remains confined to a specific tissue
2) Examples: boils & fungal skin infections
3) Mixed infection

a) Several microbes establish themselves simultaneously at the infection site

b) Examples: dental caries, wound infections and human bite infections

question

Focal infection

answer

1) When an infectious agent breaks free of its local infection and is carried to other tissues

2) Example: tuberculosis

question

bacteremia

answer

circulation of bacteria in the bloodstream

question

septicemia

answer

acute illness caused by bacteria or toxin in the blood (a.k.a blood poisoning)

question

toxemia

answer

the agent remains localized but its toxins are spread throughout the
body

question

viremia

answer

circulation of a virus in the blood

question

Portal of exit

answer

A) Specific route taken by pathogens to leave the host

B) Often the exit is the same as the portal of entry

question

Respiratory and salivary portals

answer

1) Mucus, sputum, saliva, nasal drainage, and other moist secretions act as media for exit

2) Breathing, coughing, sneezing, laughing, and talking push these pathogens into the environment

question

Skin scales

answer

1) Most individuals shed billions of dead skin cells each day and it is the largest component of household dust

2) Potential exit for the agents of fungal skin infections, syphilis, herpes simplex,
and smallpox

question

Fecal exit

answer

1) Common exit for intestinal pathogens and helminth worms (specifically
eggs or larva)

2) Fecal contamination of drinking water and its use as a fertilizer often raise public
health issues

question

Urogenital tract (EXIT)

answer

1) Vaginal discharge/semen
a) STD’s
b) Vagina is also location of neonatal infectious agents

2) Urine
a) High acidity make is less common mode of exit but agents of typhoid fever and tuberculosis may exit in urine

question

Blood (exit)

answer

1)no natural exit 4 blood except menses

2) Blood-feeding insects often carry pathogens from human blood

3) Shared needles & small abrasions causes by intercourse can also result in transmission of pathogens especially HIV & hepatitis

question

Contaminants

answer

microbes present at a given place and time that is undesirable

question

Decontamination

answer

the removal or destruction of contaminants

question

Sterilization

answer

A) Process that removes all viable microorganisms including viruses & endospores

B) Generally applies only to inanimate objects and those essential to well-being
1) Surgical instruments, syringes, packaged foods

question

Disinfection

answer

A) Refers to the use of physical or chemical means to kill vegetative pathogens and most viruses but not endospores

B) Usually only involves non-living materials due to its harsh sometimes toxic nature

question

Sanitation

answer

any cleansing technique that mechanically removes microorganisms to reduce the contamination levels to acceptable
A) Washing dishes & clothes

question

Degermation

answer

reduction of the number of microbes on the human skin by scrubbing
A) Works by removing oils and microbes on the outer layer of the skin through physical or chemical means or both
1) Hand washing & surgical scrubbing
2) Swabbing with an alcohol wipe

question

Microbial Death

answer

The permanent loss of reproductive capability, even under optimum growth conditions is the accepted microbial definition of death

question

Factors affecting microbial death rate

answer

A) Number of microorganisms

B) Nature of the microorganisms in the target population

C) Temperature and pH of the environment

D) Concentration of the agent
E) Mode of action of the agent
F) Presence of solvents, interfering organic matter, and inhibitors

question

Mode of action

answer

1. Affect the cell wall

2. Affect the cell membrane

3. Affect protein synthesis

4. Affect protein function

question

Affect the cell wall

answer

A) Block its synthesis, digest it or break down its surface

B) Makes the microbe very susceptible to lysis

C) Penicillin, cephalosporins, vancomycin, detergents, and alcohol

question

Affect the cell membrane

answer

A) Disrupt the normal transport of materials in/out of the cell or allow the free flow of substances in/out of the cell

B) Surfactants – detergents that essentially open holes in the membrane

question

Surfactants

answer

detergents that essentially open holes in the membrane

question

Affect protein synthesis

answer

A) Disruption of DNA transcription or replication
1) Ciprofloxacin, sulfonamides, and radiation (gamma, UV and X)

B) Disruption of translation in the ribosomes
1) Streptomycin, tetracycline, chloramphenicol, and erythromycin

question

Affect protein function

answer

A) Generally work by altering the protein’s natural structure (conformation)
1) Denaturation – involves the breaking of bonds within the protein to disrupt its conformation
2) Coagulation – aggregation of proteins resulting in a non-functioning mass

question

Coagulation

answer

aggregation of proteins resulting in a non-functioning mass

question

Denaturation

answer

involves the breaking of bonds within the protein to disrupt its conformation

question

Moist heat

answer

A) Steam, boiling water, or hot water (pasteurization)
B) Causes protein denaturation and coagulation
C) Works well on all types of organisms although exposure time and temperature vary from microbe to microbe
1) Generally 80oC for 20 minutes is the accepted guideline for non-heat-resistant microbes

question

Steam under pressure (steam sterilization)

answer

a) Steam can only reach 100 degrees under normal pressure; increasing the pressure allows for higher temps & better microbe killing
b) Destroys vegetative cells, spores, & viruses
c) Autoclave – the commercial device used for steam-heat sterilization
d) Similar in function to a pressure cooker
e) Avg settings are 15psi, 121 degrees, 15 mins
f) Effective at sterilizing heat-resistant materials glassware, cloth, metallic instruments, liquids) & any material that will be discarded(plastic Petri dishes & pipets)
g) Not effective in sterilizing substances that repel/absorb moisture(wax,oil,powder)

question

Methods of moist heat control

answer

1. Steam under pressure (steam sterilization)

2. Boiling Water

3. Pasteurization (hot water)

question

Methods of physical control

answer

1. Moist heat
2. Dry heat
3. Cold treatment
4. Desiccation
5. Radiation
6. Sound waves
7. Filtration
8. Osmotic pressure

question

Boiling water

answer

a) Relied on for disinfection not sterilization

b) 10 minutes will kill all non-spore-forming pathogens & most viruses

c) Used by many to decontaminate suspect drinking water

d) Recontamination after removal from water is the biggest downside with
disinfection objects with this method

question

Pasteurization

answer

a) technique in which heat is applied to liquids to kill potential agents of
infection and spoilage while maintaining the flavor & food value
b) does not sterilize liquid as thermoduric and thermophilic orgs still remain
c) 3 methods
i) high-temp-short-time (HTST) pasteurization – 71–74 degrees for 15–30 seconds (europe,asia)
ii) batch pasteurization – 63-66 degrees for 30 minutes (USA)
iii) ultrahigh-temp (UHT)
d) Goal to prevent transmission of milk-borne diseases from infected cows & milk handlers
e) Does not kill all microbes

question

Incineration

answer

(Dry heat)

1) Uses heat to reduce the microbe to gas and ash

2) Flaming the loop in lab is an example

3) Hospitals often use incineration to eliminate their infectious waste materials

question

Dry oven

answer

(Dry heat)
1) Electric coils radiate heat within an enclosed compartment

2) Sterilization occurs at 150-180 degrees for 1-4 hours

3) Used for heat-resistant materials that cannot be sterilized with moist heat (some
glassware, powders, oils, and metallic instruments)

question

Cold treatment (fridge & freezing)

answer

A) Designed to slow microbial growth

B) Common in food processing and storage

C) Not considered a viable method of sterilization or disinfection

question

Desiccation (drying)

answer

A) inhibits growth by removing water

B) inhibits the spread of most pathogens but not all of them

C) lyophilization – mixture of freezing & drying
1) used to preserve microbes and other cells

D) not considered a viable method of sterilization or disinfection

question

Ionizing radiation

answer

a) Excites electrons to the point that they are ejected from the molecule
i) DNA most sensitive
b)causes lethal chemical changes in organelles & the prod. of toxins
c) Used in sterilization of comm. food products
i) Potential probs: change flavor and nutritional value, & introduce undesirable chem. reactions
d) Is preferred methods for sterilizing drugs & tissues by hospitals
e) Potential danger to machine operators & possible damage to some materials are its disadvantages
f) Examples include gamma & X radiation

question

Nonionizing radiation

answer

a) Excites electrons causing them to jump orbitals but don’t leave molecule
i) Leads to abnormal linkages & bonds within molecules
ii) DNA again is very susceptible
(a) thymine dimers are a common result
(b) UV radiation is the primary example
i) Excellent for disinfecting air
(a) Commonly seen in lights found in hospitals, ORs, schools, nursing homes, cafeterias, & military housing
ii) Does not pass easily through solids but is used in some applications
iii) Poses threat to human tissue if overexposure occurs

question

Sound waves

answer

A) Used high-frequency sound waves to disrupt cell structure

B) Sonicator – water-filled chamber through which the sound waves become vibrations that can disrupt cell structure

C) Gram-negative bacteria are most susceptible

D) Often used to clean debris from instruments before sterilization

E) Not a reliable form of disinfection or sterilization

question

Filtration

answer

A) Used to remove microbes from air & water
B) Involves the passage of these substances through filters perforated with precise, uniform pores
1) Pore size varies dependent on what needs to be trapped but can be small enough to trap viruses
C) Used to prepare liquids that cannot withstand heat
1) Serum and other blood products, vaccines, IV fluids, and enzymes
2) Has also been used to sterilize beer and milk without altering flavor
D) Also used to capture airborne contaminants

question

Osmotic pressure

answer

(Salt concentration)

A) involves the use of salt to create a hypertonic environment

B) results in water leaving the cell, inhibiting cellular processes

question

Methods of chemical control

answer

1. Phenols
2. Alcohols
3. Halogens
4. Oxidizing agents
5. Surfactants
6. Heavy metals
7. Aldehydes
8. Ethylene Oxide gas

question

Phenol

answer

A) AKA carbolic acid
B) effective against vegetative cells but not spores
C) phenolics
1) ex. orthophenylphenol (active ingredient in Lysol), hexylresorcinol (used in mouthwash), and hexochlorophene (Phisoderm)
D) they denature proteins & disrupt cell membranes
E) often have nasty odor & some side effects

question

Phenolics

answer

chemicals derived from phenol that have had additional functional groups added

ex. orthophenylphenol (active ingredient in Lysol), hexylresorcinol (used in mouthwash), and hexochlorophene (Phisoderm)

question

Alcohols

answer

A) effective against vegetative cells but not spores

B) isopropanol & ethanol are most commonly used in 70-90% mixtures

C) work by denaturing proteins & disrupting cell walls & membranes

D) one disadvantage is that they evaporate quickly & may not be in contact with the microbe long enough to be effective

question

Halogens

answer

A) effective against vegetative cells and some spores

B) although unclear, it is believed they disrupt enzyme function

C) ex. iodine, chlorine, bromine and fluorine

question

Oxidizing agents

answer

A) especially effective against anaerobic organisms
B) are also used to treat drinking water and to eliminate spores on open surfaces
C) work by oxidizing enzymes thus shutting down the microbe’s metabolism
D) ex. peroxides, ozone (used on dialysis equipment), paracetic acid

question

Surfactants

answer

A) “surface active” chemicals

B) generally work well against vegetative cells but not spores

C) work by disrupting cell membrane structure

D) ex. soaps, detergents and mouthwash

question

Heavy metals

answer

A) generally just slow growth but do not destroy the microbe
B) work by binding with sulfur in amino acids & altering protein’s shape thus inhibiting or eliminating function
C) ex. silver, mercury, zinc & copper
D) most are no longer used
1) copper is still used to control algae growth in water
2) copper, zinc, and mercury are used to control fungal growth in paint
3) silver nitrate is sometimes used to treat oral ulcers & silver ions are used in antimicrobial fabrics
a) silver nitrate was once required by law to be administered to the eyes of newborns to prevent ophthalmic gonorrhea
4) mercury (Mecurochrome) is still used today as antiseptic

question

Aldehydes

answer

A) work by denaturing proteins and inactivating nucleic acids
1) glutaraldehyde is used for cleaning lensed instruments and some respiratory
equipment
2) formaldehyde is used in vapor form to sterilize laboratories which have become contaminated
3) both are effective at sterilization

question

Ethylene Oxide Gas

answer

A) effective against all microbes, including endospores & viruses

B) works by reacting with proteins

C) useful in sterilizing fabrics (mattress,pillow) & implantable devices (pacemakers/artificial hips),as well as any heat or moisture sensitive items

D) objects need to be exposed for 3-12 hours for full sterilization

E) care must be used as the gas is toxic, explosive, and potentially carcinogenic
1) sterilization is followed by the object being treated with heated, forced air for 8-12 hours to dissipate any remaining ethylene oxide

question

Ultra high temp pasteurization

answer

– 140-150 degrees for 1-3 seconds
(a) allows milk to be stored for long periods at room temp (ex. coffee creamers)

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