microbio exam 3 megaset

sepsis

bacterial contamination

asepsis

absence of significant bacterial contamination (of surgical instruments etc.)

degerming

mechanical removal of microbes from a limited area

commercial sterilization

killing Clostridium Botulinum endospores from food, without altering the quality of the food - not true sterilization

sterilization

killing of ALL living cells, spores, viruses

disinfection

removal of pathogens from inanimate surfaces

antisepsis

removal of pathogenic organisms from living tissues

sanitization

reducing microbes to safe levels

D-value (Decimal Reduction Time)

time required to kill 90% of cells

Thermal Death Point (TDP)

lowest temp. in which all cells in a liquid are killed in 10 mins

Thermal Death time (TDT)

The minimal time for all bacteria in a liquid culture to be killed at a particular temperature

Filtration through a filter of what size removes bacteria, endospores, yeasts, mold spires, algae, and protozoa…

0.2 µm

viruses require a pore size of…

20 nm = 0.001 µm

Non-ionizing radiation

useful for surface sterilization

Non-ionizing radiation example

UV light, does not penetrate liquids or solids well

Ionizing radiation

damages the cellular structure of organism so good for sterilization

high level disinfectants (can kill bacterial cells, mycobacteria, spores, and basically everything):

Ethylene oxide, glutaraldehyde, and formaldehyde

intermediate level disinfectants (cannot kill endospores):

Phenolics and Halogens

Low level disinfectants (cannot kill mycobacteria and endospores):

alcohols

penicillin only targets…

gram-positive bacteria

Synergistic

drugs have greater effectiveness when used together

Antagonistic

drugs interfere with each other and decrease effectiveness

Streptomyces

produces over 50% of antibiotics

MIC (minimum inhibitory concentration)

the lowest concentration of an antibiotic that prevents visible growth of a microorganism.

MBC (Minimum bactericidal concentration)

the lowest concentration of an antibiotic that kills a specific bacterium.

chemotheraputic index

toxic dose/theraputic dose

higher the chemotheraputic index…

the safer the drug

DNA Replication Inhibitors

Quinolones

Cell membrane Integrity

Polymyxin (only for gram negative bacteria because they have inner and outer membranes)

Protein Synthesis Inhibitors

Chloramphenicol (binds to 50S subunit and prevents peptide bond formation)

What do Macrolides do?

bind to 50S subunits and block peptide bond elongation

What do Tetracyclines do?

bind to 30s subunit and block peptide bond elongation?

What do Sulfonamides do?

Affect Intermediary Metabolism, and block folic acid formation

Which antibiotics effect the cell wall? (stops cell wall crosslinking, leading to cell lysis)

Penicillin, Vancomycin, Cephalosporins

Beta-lactam antibiotics

are a class of antibiotics that inhibit cell wall synthesis by interfering with the enzymes involved in crosslinking peptidoglycan layers.

Vancomycin should be..

a last resort

most Antibiotics aren’t effective for mycoplasma because…

they have no cell wall

what is the most popular antibiotic resistance mechanism?

altering the target in ribosomes

Antifungal Agent: Polyenes

Disrupts membrane integrity

**Antifungal Agent: Azoles (imidazoles, triazoles)

Interferes with ergosterol synthesis

**Antifungal Agent: Allylamines (terbinafine, lamisil)

Interferes with ergosterol synthesis

Antifungal Agents: Echinocandins (caspofungin)

Blocks fungal cell wall synthesis

Antifungal Agents: Griseofulvin

Blocks cell division

Antifungal Agents: Flucytosine

Inhibits DNA synthesis

Which body site does Staphylococcus (coagulase-neg.)

infect?

the nose

Which body site does Staphylococcus (coagulase-neg.) and

Staphylococcus aureus infect?

the skin

Which body site does Lactobacillus spp. infect?

vagina

Which body site does Viridans streptococci infect? 

Oropharynx

Which body site does Bacteroides spp. infect?

Large Intestine

What is the most common strict anaerobic gram-negative rod?

Bacteroides spp.

Sterile body sites include…

blood, cerebrospinal fluid, internal organs (brain heart, liver, kidneys), bone and bone marrow, lymph nodes, joint fluid

broad tropism

type of tropism that can cause systemic infection, and spreads through the body

narrow tropism

higher mortality rate and only infects certain tissues

amorphous/complex viruses

no symmetrical form with a flexible core wall

examples of amorphous/complex viruses

vaccinia virus

vaccinia virus…

known as the cowpox virus, and eventually led to the smallpox vaccination

lytic infection

bacteriophage enters and results in lysis

lysogeny

phage DNA intergrates into the host genome to form a prophage, that replicates

Baltimore Model

classification of viral genomes based on whether they’re DNA, RNA and ds or ss

Viral Genomes: Group 1

ds-DNA

Which viral group replicates in host cell nucleus?

ds-DNA and ss-DNA

Group 1 example

Herpes Simplex virus

Why is Poxvirus special?

It is the only dsDNA example that does not replicate in the host cell’s nucleus

Viral Genomes: Group 2

ss-DNA