Microbio Lab 23

What is the most effective way to prevent the spread of infections?

Proper hand washing

What are antiseptics?

Agents used to reduce microbes on living surfaces

How much can hand washing reduce diarrheal deaths?

Up to 50%

How long should you scrub your hands?

At least 20 seconds

Why is water alone not effective for cleaning hands?

It cannot destroy or inhibit microbial growth

Plain soap works primarily through what mechanism?

Mechanical removal of oils and microbes

What type of agent is benzalkonium chloride?

A quaternary ammonium compound (Quat)

Benzalkonium chloride is more effective against which type of bacteria?

Gram-positive

What does triclosan inhibit?

Fatty acid synthesis

Why is triclosan controversial?

Bacteria may develop resistance to it

How do plant extracts in natural soaps work?

They disrupt bacterial plasma membranes

What is the optimal alcohol concentration for sanitizers?

60–95%

Why is 100% alcohol NOT effective?

It requires water to denature proteins

What type of antiseptic is chlorhexidine?

Bisbiguanide

How does chlorhexidine kill bacteria?

It disrupts plasma membranes, causing cell leakage and lysis

What is a disinfectant?

A chemical that destroys most microbes (except spores) on inanimate surfaces

What is an antiseptic?

A chemical that destroys most microbes (except spores) on living tissues

What does “broad spectrum activity” mean?

Ability to kill many types of microorganisms

Why must a disinfectant be compatible with surfaces?

To avoid corrosion or staining (e.g., rusting metal)

What makes a disinfectant less effective in organic-rich environments?

Organic material like blood can interfere with activity

What two questions must be known before using a disinfectant?

Optimal concentration and optimal contact time

What standard test must a chemical pass to be a hospital disinfectant?

AOAC Use-Dilution Test

Why use non-porous objects in the Use-Dilution test?

They don’t absorb disinfectant and mimic real surfaces

What forms on the bead after drying in the Use-Dilution test?

A dried bacterial film

How long are beads exposed to disinfectant in the test?

10 minutes

What does NO growth in the tube indicate?

The disinfectant concentration was effective

What does growth in the tube indicate?

The disinfectant concentration was NOT effective

Name the three disinfectants tested in this exercise

Kill All, Wipe Out, Bug-Be-Gone

Name the three concentrations tested

0.1%, 0.05%, 0.01%

Which four organisms are used in this test?

E. coli, S. epidermidis, P. fluorescens, B. cereus