Microbiology microbial growth quiz

Joseph Lister

Created Listerine; impressed with Pasteur’s work; applied carbolic acid (phenol) into damaged tissues to prevent infection

Sterilization

The process of killing or eliminating all pathogens in or on a material; free of microbes, endoscopes, and viruses

Disinfection

Eliminated most pathogens

Biocide/ Germicide

Kills microbes

Bacteriostasis

Inhibiting, not killing, microbes (temporary)

Pseudomonas species

Resistant to and can actually grow in some disinfectants

Mycobacterium species

Can cause tuberculosis and leprosy

Clostridium

Spore formers

Action of soap

Mechanical removal of organisms

Nosocomial infections

Acquired from hospitals settings; patients are more susceptible to infection

Pasteurization

Brief heating to reduce number of spoilage organisms; destroys pathogens

Commercial canning process

Destroys the endospores of Clostridium botulinum

Moist heat

Irreversibly denatures proteins in microbes; bactericidal; breaks H bonds; changes shapes of enzymes

Boiling

Kills vegetative bacteria, fungi, and viruses; does not sterilize because endospores can survive

Ultra- high temperature

Shelf-stable boxed juice and milk; known as “ultra-pasteurization”

Pressurized steam

Sterilization typically at 121 oC. for 15 minutes at 15 psi (longer for larger volumes)

Prions

Destroyed at 132° for 1 hour (resistant to heat)

Autoclave indicators

Tape and biological indicators

Tape

Contains heat- sensitive indicators turns black at high temp

Biological indicators

Heat-resistant endospores of Geobacillus stearothermophilus

Geobacillus stearothermophilus (biological indicators’

Heat resistant + make endospores + autoclave

Dry heat

Not as effective as moist heat

Incineration

Type of dry heat sterilization- oxidize cell components to ashes, denature proteins

Flaming

Laboratory inoculation loop incinerates organism

Hot air ovens

Used to destroy medical waste and animal carcasses

Membrane filters

Determines if water is safe for drinking; some materials cannot withstand heat treatment; filtration retains bacteria (filtration of fluids)

Depth filters

Thick porous filtration material (like cellulose)

HEPA

High-efficiency particulate air filter used for air

Radiation

Shorter wave length= higher frequency

Ionizing radiation

Shorter wave; damages cytoplasmic membranes of G (-ve): Pseudomonas; high energy gamma-rays

Ultraviolet radiation

Destroys microbes directly; damages DNA (Thymine dimer)

Alcohols

Not reliable against endospores, some non-enveloped viruses

Why is pure less effective than aqueous solution?

Because 100% solution is too thick, and 70% is think enough to slip through

Silver

Used as an antiseptic (creams and bandages); excessive use can lead to environmental pollution

Silver nitrate

Eye drops given at birth to prevent Neisseria gonorrhoeae infections

Preservatives

Mercury, tin, and copper

Quaternary ammonium compounds

Cationic detergents (+); disinfection of food/ preparation of surfaces; attracted to negative charge of microbial cell surface

Pseudomonas

Resists quats; can grow in solutions

Freezing

Preserves by stopping all microbial growth; not sterilization!

Reducing available water → slow growth

Adding salt and sugar; lyophilization (freeze drying)

Paul Ehrlich

Synthesized arsenic compounds to treat syphilis, caused by spirochete Treponema; 606th compound effective in lab animals

Arsphenamine

Aka Salvarsan- the first antibacterial chemotherapeutic agent

Chemotherapeutics

Chemicals used to treat disease; antimicrobials

Alexander Fleming

Discovered penicillin G- first antibiotic made by the fungus (mold) Penicillium that inhibited Staphylococcus aureus

Streptomyces griseus

Created streptomycin

Antimicrobials

Derived from microorganisms

Characteristics of antimicrobial medications

1. Have selective toxicity

2. Don’t trigger allergic reactions

3. Soluble in body fluids

4. Does not induce drug resistance quickly

5. Dysbiosis

6. Broad spectrum

7. Antimicrobial action

Therapeutic index

Toxicity of given drug; we want HIGH

High therapeutic index

Less toxic to patient/ dose used for therapy

Normal microbiota

Competitive exclusion of pathogens

Dysbiosis

Imbalance of the microbiome; doesn’t suppress normal flora (E. Coli gets killed by the antibiotic) Clostridium difficile causes diarrhea

Broad spectrum

Emergency only; drawback- inhibition of normal human microbiota

Bacteriostatic

Inhibits bacterial growth; patients immune systems eliminate the stalled bacterial cells

Antagonistic drugs

Drugs that interfere with each other * you would not prescribe Penicillin and a bacteriostatic drug because bs drug stops growth and penicillin is effective with growing bacteria

Synergistic drugs

One medication enhances the other

Additive drugs

Medications do not interfere with each other

Antibiotic

Substance produced by microbes

Beta- Lactam ring

Penicillin, Ceohalosporin, Vancomyosin, and Bacitracin; inhibit cell wall synthesis

Beta-Lactam limitations

Gram + and only effective against actively growing cells

Penicillin resistance

Some bacteria synthesize Beta-Lactamase, which breaks critical Beta-lactam ring and inactivates beta-lactam antibiotics

Bacitracin

Common in non-prescription first-aid ointments; toxicity limits

Inhibit protein synthesis

Aminoglycosides, tetracyclines, macrolides; distinguish between prokaryotic and eukaryotic

Aminoglycosides

Irreversibly bind to 30S ribosomal subunit, which causes it to become bactericidal

Chloramphenicol

Binds to 50S ribosomal subunit; prevents peptide binds from forming and blocking proteins synthesis

Fluoroquinolones

Targets DNA synthesis by inhibiting topoisomerases; enzymes that maintain supercoiling of DNA and DNA gyrase breaks; bactericidal

Rifamycins

Block prokaryotic RNA polymerase; block inhibition of transcription; effective against members of genus Mycobacterium

Sulfonamides

Structurally similar to PABA; competitive inhibition of folic acid biosynthesis

Folate pathway

Useful target for antibiotics because bacteria synthesize folate while human cells do not

Trimethoprim

Combines with sulfonamide and has synergistic effect

Daptomycin

Inserts into cytoplasmic membrane; cannot penetrate outer cell membrane

Polymyxin B

Binds to membranes of Gram - and destabilizes the plasma membrane

Isoniazid

Inhibits my colic acid synthesis

Minimum inhibitory concentrations

Lowest concentration that prevents growth in vitro

Minimum bactericidal concentrations

Kills 99.9% of cells in vitro; determined form plate count from MIC

Kirby-Bauer disc diffusion test

Routinely used to determine sensitivity/ susceptibility of bacterial strain to antibiotics; drug characteristic must be taken into account

E test

Modification of disc diffusion test, uses strip with gradient antibiotic

Limitations of antibiotics; innate/ intrinsic resistance

Only effective against bacteria;

Multidrug-resistant M. Tuberculosis

Resist first line antibiotics; isoniazid and rifampin

Antiviral medications

Difficult to target because they use the host cell machinery to replicate

Antifungal chemicals

Target Ergersterol; polyenes, azoles, allylamines