microbiology unit 3

What do germicidal methods do?

They kill microorganisms, commonly referred to as 'germs.'

What is the difference between bactericidal and bacteriostatic methods?

Bactericidal methods kill bacteria, while bacteriostatic methods only inhibit bacterial growth.

What is the function of fungicidal methods?

Fungicidal methods kill fungi, whereas fungistatic methods only inhibit fungal growth.

What do sporicidal agents do?

Sporicidal agents kill bacterial endospores.

What is the role of virucidal agents?

Virucidal agents inactivate viruses.

What is disinfection?

The destruction and/or removal of MOST microorganisms from inanimate surfaces, such as vegetative cells, but not endospores.

What is sterilization?

The process of destruction and complete removal of ALL viable microorganisms from inanimate surfaces, including bacterial endospores.

What chemical can be used as a sterilant at high concentrations?

Bleach

What is Lysol commonly used for?

As a household disinfectant that leaves commonly touched surfaces disinfected.

What is the key difference between disinfection and sterilization?

Disinfection removes most microorganisms, while sterilization removes all viable microorganisms.

What is the primary function of antiseptics?

Antiseptics destroy or remove most microorganisms from living tissues, preventing the entry of pathogens into wounds or sterile tissues.

What does sanitization refer to?

Sanitization refers to the reduction of the numbers of microorganisms to safe ('sanitary') levels.

Are sanitization methods always germicidal?

No, sanitization methods are not necessarily germicidal; they involve decontamination through scrubbing or filtration.

What does the mode of action of an agent refer to?

The mechanism by which it targets a microbe.

What type of agents destroy microbial cell structures?

Most physical and chemical agents, which are bactericidal.

What are three ways that bactericidal agents damage microbes?

They damage/denature proteins, break up cell membranes, and damage nucleic acids (e.g., DNA).

What is a bacteriostatic method?

A method that causes dehydration by removing water from cells.

Heat Methods

All methods that involve heat will denature proteins and are therefore bactericidal.

Dry Heat

Dry heat sterilizes.

Moist Heat

Moist heat includes hot water/pasteurization which disinfects.

Boiling Water

Boiling water disinfects.

Steam Heat Under Pressure

Steam heat under pressure sterilizes.

What effect do cold temperatures have on bacteria?

Cold temperatures are bacteriostatic, meaning they inhibit bacterial growth.

How are cold temperatures used in food preservation?

Cold temperatures are used to preserve foods and prevent spoilage.

What type of radiation causes irreversible damage to DNA?

Ionizing radiation (e.g. Gamma irradiation)

What is the primary use of ionizing radiation?

Sterilization, as it penetrates barriers such as glass and plastic.

What type of radiation is used to disinfect surfaces?

Nonionizing radiation (e.g. UV irradiation)

How does nonionizing radiation differ from ionizing radiation?

Nonionizing radiation disinfects but does not penetrate barriers.

What is a common application of nonionizing radiation?

To decrease microbial load on surfaces such as bench tops and food products.

radiation methods

Radiation methods damage DNA and are bactericidal

What do desiccation and freeze-drying methods do to cells?

They dehydrate cells.

What is a key characteristic of desiccation and freeze-drying methods?

They are bacteriostatic.

What are desiccation and freeze-drying methods used for?

Preservation of foods and long-term storage of lab cultures.

What is the primary function of filtration in decontamination?

The mechanical removal of microbes by forcing air or liquids through a filter.

When is filtration typically used?

For sanitization.

What pore size must a filter have to achieve sterilization through filtration?

Less than 0.2 micrometers (um).

Can filtration be used for sterilization?

Yes, if the pore size is small enough (less than 0.2 um).

What effect do halogens have on proteins?

Halogens cause protein damage and are bactericidal.

What is the active ingredient in bleach used for sterilization?

Sodium hypochlorite (NaClO)

How can bleach be used in high concentrations?

It can be used to sterilize.

What substances can be used to disinfect hot tubs and swimming pools?

Chlorine and Bromine tablets.

What is iodine used for when applied to skin?

Iodine can be used as an antiseptic.

What are the properties of aldehydes, chemical method?

Aldehydes damage proteins, are bactericidal, and can be used for sterilization.

What concentration of glutaraldehyde is used for sterilization?

4% glutaraldehyde sterilizes (sporocidal).

What is the toxicity level of 2% glutaraldehyde compared to 4%?

2% glutaraldehyde is less toxic and more likely to be used in hospital-grade sterilants.

What is the primary use of 4% glutaraldehyde despite its ability to sterilize?

4% glutaraldehyde is typically only used as an embalming agent due to its higher toxicity and carcinogenic nature.

What are the bactericidal properties of hydrogen peroxide and alcohols?

Both hydrogen peroxide and alcohols damage proteins and are bactericidal, used as antiseptics.

What concentrations of ethanol are used for disinfection and sterilization?

0.5 - 3% ethanol disinfects, while 60-90% ethanol disinfects but would not be used as an antiseptic.

What is the role of chlorhexidine in hospitals?

Chlorhexidine is used as a disinfectant and antiseptic, damaging cell membranes and being bactericidal.

What are phenolics and where are they commonly found?

Phenolics can be natural or commercially produced and are added to many household soaps, disinfectants, and antiseptic products.

What is the primary action of phenolics?

Phenolics are bactericidal and can cause damage to cell membranes and proteins.

What is a notable example of a phenolic compound?

Triclosan, which was once found in many commercial 'antibacterial' products.

What are quaternary ammonium compounds (Quats or QACs)?

A class of amphipathic detergents/surfactants used as bactericidal ingredients in household disinfectants.

How do quaternary ammonium compounds work?

They lodge into and disrupt cell membranes due to their amphipathic nature.

What are some examples of quaternary ammonium compounds?

Benzalkonium chloride and Roccal.

How can heavy metals affect bacteria?

Heavy metals can be bacteriostatic or bactericidal depending on concentration and can denature proteins.

List some examples of heavy metals that can be toxic or bactericidal.

Iron (Fe), Copper (Cu), Zinc (Zn), Nickel (Ni), Aluminum (Al), Lead (Pb), Silver (Ag), Mercury (Hg), Chromium (Cr), Arsenic (As).

What is thimerosal and its use?

Thimerosal is an antiseptic agent and vaccine preservative, though it is not used in modern flu shots.

What role do weak acids and bases play in disinfection?

Weak acids and bases, such as vinegar (acetic acid) and ammonia, can be bactericidal and used as low-cost disinfectants.

How do high concentrations of sugars and salts preserve food?

They create high osmolarity, driving water out of cells by osmosis, dehydrating them and preventing their growth.

What is the purpose of soap products in sanitization?

Soap products are used for sanitization and decontamination by mechanically scrubbing to remove microbes.

Are regular soaps considered antiseptic products?

Regular soaps usually lack 'antibacterial' ingredients and are not antiseptic, but they effectively decrease the number of microbes on skin when used properly.

What is the significance of bacterial resistance to phenolics?

Bacterial resistance to phenolics is widespread, making them less effective over time.

What evidence exists regarding antibacterial soaps compared to regular soaps?

There is little evidence that antibacterial soaps are more effective than regular soaps.

What is the effect of high concentrations of heavy metals?

High concentrations of heavy metals are toxic and can be bactericidal.

Antimicrobials

Medications (naturally or artificially produced) that inhibit or kill microbes.

Antibiotics

Naturally produced antimicrobials.

Broad spectrum antimicrobials

Antimicrobials that affect a wide range of microbes.

Narrow spectrum antimicrobials

Antimicrobials that affect a more limited range of microbes.

What is a key characteristic of an ideal antimicrobial regarding specificity?

It has high specificity and a narrow spectrum, targeting the pathogen while leaving normal biota unharmed.

What are the desired side effects of an ideal antimicrobial?

It should have few side effects, being low in toxicity for the host and non-allergenic.

What is important about the stability of an ideal antimicrobial in the host?

It should be able to localize and maintain stability within the host.

What is the significance of shelf life in an ideal antimicrobial?

An ideal antimicrobial should have a long shelf life.

Why is cost-effectiveness important for an ideal antimicrobial?

It should be cost-effective to ensure accessibility and widespread use.

What is a critical aspect of pathogen resistance in relation to an ideal antimicrobial?

There should be no resistance among pathogens to the ideal antimicrobial.

Penicillin

A group of antibiotics derived from Penicillium fungi that target bacterial cell wall synthesis.

Ampicillin

A derivative of penicillin that is effective against a wider range of bacteria.

Methicillin

A penicillin derivative that is resistant to certain beta-lactamase enzymes.

Amoxicillin

A widely used penicillin antibiotic that is effective against various bacterial infections.

Cephalosporins

A class of antibiotics that are structurally and functionally similar to penicillins and target bacterial cell wall synthesis.

Carbapenems

A class of highly effective antibiotics that are resistant to many beta-lactamases.

Bacitracin

An antibiotic that targets bacterial cell wall synthesis, commonly found in Neosporin.

Vancomycin

An antibiotic used to treat serious infections caused by Gram-positive bacteria, targeting cell wall synthesis.

Resistance

The ability of bacteria to withstand the effects of antibiotics, often due to beta-lactamase enzymes.

Who first discovered penicillin?

Alexander Fleming

Aminoglycosides

Primarily made by soil bacteria (e.g. Streptomyces). Example: Streptomycin, neomycin, tobramycin.

Tetracycline

An antimicrobial that targets protein synthesis in bacteria.

Macrolides

Includes Erythromycin, Clindamycin, and Azithromycin (Name brand: Z-Pak).

Erythromycin

A type of macrolide that targets protein synthesis in bacteria.

Azithromycin

A macrolide known by the name brand Z-Pak, which targets protein synthesis in bacteria.

What do fluoroquinolones target in bacteria?

Fluoroquinolones target DNA gyrase, inhibiting DNA replication and transcription.

Name two examples of fluoroquinolones.

Ciprofloxacin (Cipro) and Levofloxacin.

What does Rifampin target in bacteria?

Rifampin targets RNA polymerase, inhibiting transcription.

What condition are both fluoroquinolones and Rifampin effective at treating?

Tuberculosis.

What was the drug of choice taken by White House staff as a precaution after the 2001 anthrax letters?

Ciprofloxacin (Cipro).

What is the primary action of sulfonamides (sulfa drugs)?

They block folic acid synthesis in bacteria.

What type of infections is Metronidazole used to treat?

Bacterial GI tract infections and many protozoan infections under anaerobic conditions.

What is the function of antifungals like Fluconazole?

They inhibit fungi.

How do antivirals work?

They can slow or inhibit the replication of viruses in our cells.

What is Paxlovid used for?

It inhibits viral replication and is used to treat COVID-19.