Micro Test 2

refers to increase in numbers not size (no baby/adult bacteria)
binary fission-> one cell that divides into two

time required to divide
human pathogens can divide about every 20 to 30 minutes--time to double in numbers
usually this occurs for only a short period (often 24hrs) of time -> stops because runs out of space & nutrients
1 cell to 1,000,000 in 10 hours

Growth Curve

new environment--some DNA & RNA synthesis but little or no cell division

maximum cell replication (only short period of time)
most sensitive to antibiotics--especially penicillium

death rate = multiplication rate
often a result of decreased available nutrients
toxin production greatest

rate of cell death exceeds multiplication rate

heat and disinfectants

Planktonic & Biofilms

free floating--water, saliva, or infection in blood etc.

bacteria attached to a surface and to each other and form a multilayer of cells
can form complex microbial communities
form on heart valves, joint replacement, etc.
**are much more difficult to treat with antibiotics since they often cannot penetrate the biofilm layer of cells
cells can detach from biofilms and be carried to other areas (very serious infection)

1) Temperature
2) pH
3) Water availability
4) Oxygen requirements

enzymes are heat resistant so some bacteria can grow at high temperatures (some multiply at boiling point 100C)
refrigeration (4-10C) slows down growth
freezing--does not kill bacteria
most human pathogens are mesophiles grow best at approx. 37C/98.6F
relates to optimum enzyme activity

a medically important human pathogen that grows at refrigerator temperatures
all food is tested for
meats & dairy products & produce (slicer gets contaminated)
pregnancy-> immunocompromised & this can cause birth deficts

most bacteria like a pH of 6.5-7.5
fungi--can grow at more acididc pH--why it grows on fruit (more acidic)
few pathogenic bacteria grow below pH of 4--except Heliobacter pylori--can cause ulcers, gastritis in humans
BJ Marshall -> ate Heliobacter pylori
zoonotic--infection that comes from animals

hypertonic environment--s. aureus grows in
concentration of dissolved salts is higher outside the cell than inside so water will go outside the cell and stops it from growing
skin is hypertonic enivronment

obligate aerobes--myobacterium tuberculosis
obligate anaerobes--clostridium tetani
faculative anaerobes (will use oxygen if it is present)--escherichia coli 0157

1) Chemically defined
2) Complex media
3) Selective media

seaweed
trypticase soy agar/ broth
gushers -> solidifying agent is agar
gelatin -- (made from animal collagen) beef & pork by-products

media in which the exact chemical composition is known

trypticase soy agar, blood agar, chocolate agar
contains addititves such as serum, milk, sheep blood, meat by products, varies from batch to batch because they're not all the same
most common type in microbiology labs and hospitals

mannitol salt
staph aureus grows really well in MSA

1) Physical agents--heat and radiation
2) Chemical agents--gases and liquids
3) Mechanical removal methods--filtration of air and liquids

process that destroys or removes all forms of microbial life (including spores and viruses)

Moist heat
Dry heat
Boiling
Gas
Ionizing radiation
Non-ionizing radiation

method most commonly used
121 C, steam under 15 lbs. pressure, 15 minutes- kills all cell types (however does not kill prions)
use autoclave (machine)
more effective and used more often

160 C (320 F) for 2 hours

EPA recommends 3 min to kill most vegetative forms--but hepatitis virus survive longer and spores survive even longer
bacteria spore are more resistant to heat than vegetative forms of bacteria and fungi

ethylene oxide + chlorine dioxide--4-18 hours treatment
vaporized hydrogen peroxide -> most comonly used in hospitals

gamma rays--high-penetrating-is used for sterilization
used for plastic
can be used for food & food storage

does not penetrate well
ex: microwave
UV- kills well-surface microbes & if air-germicidal, lamps reduce bacteria in air, poor penetration of UV = disadvantage

physical process or a chemical agent to destroy vegetative pathogens but not necessarily bacterial endospores--normally used on inanimate (non-living) objects

cleansing technique that mechanically removes microorganisms

reduces the number of microbes on human skin--a form of decontamination but on living tissue

is usually reserved to when one is referring to the application of antimicrobial compounds to living tissue

is usually reserved to when one is referring to the application of antimicrobial compounds to non-living (inanimate) objects

1) halogens
2) phenols
3) alcohols
4) heavy metals
5) aldehydes
6) oxidizing agents
7) quaternary ammonia compounds

iodine--antiseptics (only applied to living tissue)
chlorine--disinfectants
both most important in health care
tincture of iodine--betadine--povidone iodine, gets very sticky (commonly used in hospitals)
chlorine bleach--most common disinfectant, used in households
bleach bath can lessen symptom of chronic eczema 1/4 or 1/2 cup
1 teaspoon of bleach to a gallon of drinking water

lysol-disinfectant, most common phenol type disinfectant
hexachlorophene-antiseptic (phisohex) other skin washes

etOH-ethyl alcohol (consumed by humans)
100 proof = 50% EtOH
200 proof = 100% absolute (100% alcohol)
70% optimum conc. for antibacterial activity but 30-35% can also kill bacteria -> western movies, pour alcohol in the wound
isopropyl--rubbing alcohol (about 70%) -> rub on skin before a shot, not safe to drink
methanol -> non-drinking alcohol, used in anti-freeze

1) ethyl alcohol
2) isopropyl alcohol
3) methanol

gold, silver (could be used for severe burns), copper--piping is better (better for water distribution), mercury, merthiolate, mercurochrome, copper, sulfate, zinc, chloride

soaps & detergents
are emulsification agents--surfactants

formaldehyde a gas (also can be gassed into water)
formalin (formaldehyde gas in water +MeOH) -> preservative -> inhibits the growth of bacteria & embalming agent
glutaraldehyde -> used to soak dental instruments overnight
both can be used to achieve cold sterilization

H2O2 hydrogen peroxide, benzoyl peroxide -> used for acne

antiseptics & disinfectants
if you work in health care--two infectious agents most concerned about--hepatitis & myobacteria tuberculosis
don't assume things with disinfectants

a metabolite produced by one microorganism that inhibits a specific metabolic pathway in another microorganism

1) Selectively toxic to microbe but nontoxic to host cells
2) Microbicidal rather than microbistatic -> inhibit the growth and many antibiotics we use do this
3) Relatively soluble and not excreted prematurely (too soluble)
4) Does not lead to development of antibiotic resistance
5) Does not cause allergies

the smallest concentration of drugs needed to give a desirable effect

1) Cell wall synthesis
2) Nucleic acid synthesis
3) Protein synthesis
4) Inhibition of metabolism (folic acid synthesis)
5) Inhibition of cytoplasmic membrane function/structure

1) inability of drug to diffuse into that body compartment--brain, joints (attach to blood vessels), skin especially difficult to treat
2) resistant microbes -> thick capsule
3) mixed infection--caused by more than one pathogen
4) growing in a biofilm (many layers of bacteria and antibiotic cannot penetrate to all the bacteria cells)

more difficult to satisfactorily treat because they're more similar to human cells

much more similar to our cells (in structure and metabolism) and much more difficult to selectively inhibit
tend to be somewhat toxic to us

Metronidazole (flagyl)
Trichomonas vaginalis

used to treat Giradia lamblia (intestinal protozoan parasite)

most common STD in United States

much more difficult to selectively treat as well -> lack of unique enzymes

generally more effective against Gram + bacteria
penicillins--ampicillin, methicillin, bacitracin, amoxicillin, vancomycin (genetically modified)
all have beta lactam ring

cleave (break) beta lactam ring

Streptomycin--attach to ribosome and change shape
Tetracycline--inhibit attachment of tRNA to mRNA
Erythromycin--attach to bacteria ribosome

Nalidaxic acid--inhibit unwinding of DNA by blocking DNA gyrase which occurs only in bacteria
Rifampin--inhibit RNA polymerase

Sulfonamides

Polymyxin B

magainins known as the polypeptide antibiotics
frogs and salamanders--treat bacterial infections--frog in bucket of milk

antimicrobial compounds, stomach super acidic

bacteria doesn't respond to antibiotic -> need to do testing

done the same way throughout hospitals
bacteria -> pure culture for sensitivity test

use antibiotic testing the most
turkey for thanksgiving -> been on antibiotics whole life

greater zone -> more sensitive to antibiotic

Synergism
Antagonistic effect

when the therapeutic effect of two drugs taken simultaneously is greater than the sum of their individual effects
can assign a number to how well a drug works
ex. penicillin + streptomycin (works well together)

when the therapeutic effect of two drugs taken simultaneously is less than the sum of their individual effects
ex. penicillin + tetracycline (cause antibiotics not to function as well)

produce enzymes to destroy antibiotic or inhibit entry of antibiotic & maybe thick capsule to prevent entry--other means as well such as pump antibiotic out of the cell--can sometimes overcome by giving massive amounts of antibiotics

give a large initial dose of antibiotic (because some may be resistant before even antibiotic therapy)
give a large amount to quickly reduce the number of bacteria to manageable levels so that our bodies can quickly clear before resistant forms emerge

yes

Gram + & Gram - -> reduce normal flora--yeast infections etc. (c diff)

only directed at Gram + or Gram -

we need good immune system
immunocompromised, elderly, newborns, cancer patients -> harder to get over diseases

mouth turns white -> thrush -> caused by yeast (eukaryotic cell)
disruption of normal flora

dehydrated