Microbiology Unit 2 Study Guide

Sterilant

process that destroys 100% of microbes on non-living surfaces

Disinfectants

physical or chemical agent used to kill microbes on non-living surfaces

Antiseptic

used on living tissue to reduce risk of infection

or sepsis

Cidal

Static

agents that stop the growth of microbes (bacteriostatic)

Filtration

mechanical removal of microbes or endospores from gas or liquid (sterilize).

Radiation

sterilization without heat or chemicals, killing all microorganisms

Pore size of 0.22-0.45 μm

removes bacterial cells

Pore size of 0.025-0.22 μm

removes viruses

Ionizing Radiation

penetrate surfaces, sterilization without heat or chemicals (X rays, Gamma rays & high energy electron
beams, <1nm), affects virtually all microbes

Non-Ionizing Radiation

primarily disinfection of surfaces and air, low penetration, affects virtually all microbes

Ultraviolet Radiation

Form of non-ionizing energy with short wavelength(~10-400nm)

Dry Heat (oven sterilization)

hot air oven, sterilization, desiccates (dries) cytoplasm

-2 hours at 170 Celsius degrees

Ultrasonic Vibration (Sonication)

High frequency sound waves (20-40kHz), Shock waves are conducted through living cells, structures or liquids

Autoclaving

Deep penetration of materials with small water molecules

Pasteurization

heat method used to treat liquids (milk & juice)

Identify temperature & time required for the following moist heat methods.

Explain how filtration is used to remove microbes from air and water. (Be sure to include relevant units of measure such as pore size).

Mechanical removal of microbes or endospores from gas or
liquid (sterilize)
-Used to sterilize heat sensitive liquids
-HEPA filters and HEPA vacuums, surgical masks
-Based on pore size
- Pore size of 0.22- 0.45 m: removes bacterial cells
-Pore size of 0.025 – 0.22 m: removes viruses

Sterilant

completely kills microbes 100%, including acid

fast bacteria and bacterial endospores

Disinfectant

reduces the number of microbes on working

surfaces <100%. Includes low, intermediate and some high level

Antiseptics

reduces the number of microbes on our skin
<100%

Sanitizers

physically removes microbes through cleaning
<100%

Halogens, Alcohols, Phenolics, Quaternary Ammonium Compounds site(s) of action

Site of action: membranes and proteins

Biguanides-Chlorhexidine, Detergents and Soap site(s) of action

Site of action: membranes

Peroxygens site(s) of action

Site of action: membranes, DNA and proteins

Aldehyde, Metals: silver, mercury, copper & zinc site(s) of action

Site of action: proteins

Phenolics, bisphenols (triclosan)
Quats
Chlorhexidine
Halogens
Alcohols
Peroxygens

are sites of action for the following: cytoplasmic membrane

Ethylene oxide
Peroxygens

are sites of action for the following: DNA

Alcohols
Aldehydes
Halogens
Metals (silver, mercury, copper, zinc)
Peroxygens
Phenolics
Quats
Ethylene oxide

are sites of action for the following: proteins

Residual chemical

chemical effective for a length of time after it’s applied

Non-Residual chemical

vaporizes

Complete this table.

Antibacterial targets

target: cell wall, cell membrane, nucleic acid, metabolism or protein synthesis

Antifungal targets

target: cell membrane, nucleic acid, cell division

Antiviral targets

target: attachment, entry, uncoating, replication, assembly, or release

Antibacterial toxicity

Low Toxicity

Antifungal toxicity

Moderate Toxicity

Antiviral toxicity

High Toxicity

broad spectrum

are effective against many types of microbes and tend to have higher toxicity to the host.

narrow spectrum

are effective against a limited group of microbes and typically exhibit lower toxicity to the host.

natural drugs

products secreted by bacteria & fungi (used to kill the competition).

semi-synthetic drugs

isolated from natural sources, but then chemically modified in a laboratory to make the drugs more effective, longer lasting, easier to administer, and less toxic to the patient.

selective toxicity

Drug must kill pathogen, but not harm the host.

Diffusion (Kirby-Bauer) sensitivity test

Used to determine whether an antibiotic is effective against a particular microbe.

Minimum Inhibitory Concentration (MIC)

Used to determine lowest concentration (dose) of drug able to kill microbe.

Bacteria that make antibiotics

Bacillus (bacitracin), Streptomyces

6 factors to consider when selecting an ideal antimicrobial agent to treat a patient.

1. Be readily available

2. Inexpensive

3. Chemically stable

4. Easily administered

5. Nonallergenic

6. Selectively toxic

Antibiotics that Block Cell Wall Synthesis

Penicillins (end in –cillin): Produced by green mold; Penicillium (kills off competing bacteria.

Semi-synthetic penicillins (Ampicillin & amoxicillin): Made in lab by attaching synthetic group to beta-lactam ring

Narrow spectrum antibiotic: Effective treatment for streptococcal infections

Others: bacitracin (topical), cephalosporin, cephalothin & vancomycin

Antibiotics that Inhibit Protein Synthesis

Aminoglycosides (many end in –mycin or -micin); Produced by Streptomyces (Mold-like soil bacteria)

Broad spectrum: Effective against Gram + staph & Gram - bacteria

Tetracyclines: Produced by Streptomyces (Mold-like soil bacteria); Broad spectrum: Gram -, Rickettsia, Chlamydia, Protozoa, fungi

Chloramphenicol: Produced by Streptomyces; Broad spectrum: Gram negative, Rickettsia, Chlamydia, Fungi

Antibiotics that Inhibit Nucleic Acids

Synthetic antibiotics = Not produced by living organisms; made in the

lab; Broad spectrum: Active against Gram + and Gram – bacteria; Fungi and viruses

Site of action: Interferes with DNA replication and reverse

transcription of RNA; Quinolones (Ciprofloxacin): inhibits DNA synthesis; Rifampin: inhibits RNA transcription

Antibiotics that Disrupt Cellular Membranes

Broad spectrum: target bacterial & fungal cell walls

Antifungals: Fluconazole, Polyenes & Amphotericin B

Antibacterial: Gramicidin & Polymyxin (topical drugs)

Polymyxin B targets Gram negative bacteria!

Antibiotics that Block Metabolism (Folic Acid)

Synthetic antibiotics = Not produced by living organisms;

made in the lab; Broad spectrum: Active against Gram + and some Gram - bacteria

Examples: Sulfonamides; Sulfa drugs: developed in mid 1930s; over 150 have been synthesized. Often used to treat UTI’s

3 Mechanisms of Resistance to Antimicrobial Drugs

1. Production of an enzyme: Bacterial enzymes; Metabolizing drugs, detoxification

2. Alteration of the target of the drug

3. Efflux pumps: Active transportation (pumping the drug out)

Penicillin Resistance

Penicillin resistance gene is on a plasmid (transferred by conjugation or transformation)

Gene codes for a protein enzyme called penicillinase (beta-lactamase enzyme)

Penicillinase breaks beta-lactam ring & destroys penicillin molecule.

3 causes for the proliferation (increase) of drug resistant microbes.

1. Long term or chronic use

2. Subtherapeutic use

-lower than effective dosing dose

3. Superinfection

-One type of microbe replaces another