Lab 19

Name two chemical agents that are reliable for sterilization.

1. Alcohol 2. Soap and detergents

State five mechanisms by which microorganisms may resist antimicrobial chemotherapeutic agents.

1. Producing enzymes which inactivate the antibiotic 2. Altering the target site in the bacterium to reduce or block binding of the antibiotic 3. Altering the membranes and transport systems to prevent the entry of the antibiotic 4. Developing an alternate metabolic pathway to by-pass the metabolic step being blocked by the antimicrobial agent 5. Increasing the production of a certain bacterial enzyme

List five factors that may influence the antimicrobial action of disinfectants, antiseptics, and sanitizers.

1. The concentration of the chemical agent. 2. Temperature 3. kinds of microorganisms 4. number of microorganisms 5. nature of the material bearing the microorganisms

Describe two modes of action of disinfectants, antiseptics, and sanitizers, i.e., how they harm the microorganisms

1. damage semipermeable cytoplasmic membrane causing leakage of cellular materials 2. denature microbial enzymes and other proteins blocking metabolism

A chemical agent that is reliable for sterilization is:

2% glutaraldehyde

What is the mode of action for streptomycin, neomycin, tobramycin, tetracycline, doxycycline, erythromycin, azithromycin, clarithromycin, oxazolidinones, streptogramins.?

Alters prokaryotic ribosomes blocking translation

A test is one done under the actual conditions of normal use is called:

An in vivo test

State why chemical agents are usually unreliable for sterilization

Because disinfectants and antiseptics often work slowly

broad-spectrum antibiotic

Drugs that are effective against a variety of both Gram-positive and Gram-negative bacteria

narrow-spectrum antibiotic

Drugs that are effective against just Gram-positive bacteria, just Gram negative bacteria, or only a few species are

Name four bacteria that commonly possess these plasmids.

Escherichia coli Salmonella Shigella Pseudomonas

Describe four different major modes of action of antimicrobial chemotherapeutic chemicals

Inhibit peptidoglycan synthesis Inhibit normal synthesis of the acid-fast cell wall Alter the cytoplasmic membrane Inhibit protein synthesis Interfere with DNA synthesis

What is the mode of action for floroquinolones, sulfonamides and trimethoprim, and metronidazole?

Inhibits DNA replication

What is the mode of action for penicillin G, methicillin, ampicillin, cephalosporins, carbapenems, monobactems, carbacephem, glycopeptides, and bacitracin?

Inhibits peptidoglycan synthesis causing osmotic lysis

Which is NOT a mode of action for disinfectants, antiseptics, and sanitizers?

Inhibits peptidoglycan synthesis causing osmotic lysis.

Compare the transient and resident flora in terms of ease of removal.

It is routine practice to wash the hands prior to and after examining a patient and to do a complete regimented surgical scrub prior to going into the operating room

List four genera of microorganisms that produce useful antibiotics

Penicillins Cephalosporium Bacillus Streptomyces

Define transient flora and resident flora and

Resident flora are the normal flora of the skin Transient flora are the microorganisms you pick up from what you have been handling

susceptible

Using Table 2 in your lab book, is this Staphylococcus resistant, susceptible, or intermediate to OX1?

An agent used to disinfect inanimate objects or surfaces but is generally to toxic to use on human tissues is called:

a disinfectant

An agent that may not eliminate microbes, but reduces microbial numbers to a safe level is called:

a sanitizer

antiseptic

an agent that kills or inhibits growth of microbes but is safe to use on human tissue

sanitizer

an agent that reduces, but may not eliminate, microbial numbers to a safe level.

disinfectant

an agent used to disinfect inanimate objects or surfaces but is generally to toxic to use on human tissues

An agent that kills or inhibits growth of microbes but is safe to use on human tissue:

an antiseptic

Substances produced as metabolic products of one microorganism which inhibit or kill other microorganisms are called

antibiotics

antimicrobial chemotherapeutic chemical

chemicals synthesized in the laboratory which can be used therapeutically on microorganisms

Briefly describe R-plasmids

genes coding for multiple antibiotic resistance

Discuss the meaning of selective toxicity in terms of antimicrobial chemotherapy

he agent used must inhibit or kill the microorganism in question without seriously harming the host

State why the results of an in vitro test to evaluate chemical agents may not necessarily apply to in vivo situations.

in vitro test is one done under artificial, controlled laboratory conditions

State what is meant by MIC

minimum inhibitory concentration

Antibiotics that are effective against just gram-positive bacteria, just gram negative bacteria, or only a few species are termed:

narrow spectrum

____________________ means that the agent used must inhibit or kill the microorganism in question without seriously harming the host

selective toxicity

Antibiotics that inhibit microbial growth long enough for the body's own defenses to remove the organisms are said to be:

static in action

antibiotic

substances produced as metabolic products of one microorganism which inhibit or kill other microorganisms

State why antimicrobial susceptibility testing is often essential in choosing the proper chemotherapeutic agent to use in treating an infection

to determine which antimicrobial chemotherapeutic agents will most likely be effective on a particular strain of microorganism

The microorganisms you pick up from what you have been handling is called:

transient flora.