Microbial Control and Antimicrobial Medications

Flashcards covering the key concepts and details from the lecture notes on Microbial Control including but not limited to: methods of microbial control, heat sterilization, chemical methods, antibiotics and resistance.

Who was Joseph Lister?

A British physician who revolutionized surgery by introducing methods to prevent wound infections. He used carbolic acid (phenol) to prevent infections and sterilize instruments.

What did Joseph Lister apply to damaged tissues to prevent infections?

Carbolic acid (phenol)

Why were patients undergoing even minor surgeries at great risk until the late 19th century?

Physicians were unaware that their hands could transmit diseases from patient to patient and did not understand that airborne microbes could infect open wounds.

What factors complicate the selection of an effective antimicrobial procedure?

Type and number of microbes, environmental conditions, risk of infection, and composition of the item to be treated.

Which microbes are highly resistant to antimicrobial treatments?

Bacterial endospores, protozoan cysts and oocysts, Mycobacterium species, Pseudomonas species, and non-enveloped viruses.

What is decimal reduction time (D value)?

The time required to kill 90% of a microbial population under specific conditions.

How do dirt, grease, and body fluids affect antimicrobial procedures?

They interfere with heat penetration and the action of chemicals.

How does temperature and pH influence effectiveness of antimicrobial procedures?

Temperature and pH can influence effectiveness; for example, sodium hypochlorite is more effective at higher temperatures and low pH.

Why are some sterilization and disinfection methods inappropriate for certain items?

Heat can damage plastics and other materials. Moist heat and liquid chemical disinfectants cannot be used to treat moisture-sensitive material.

What is an autoclave and what are the standard conditions for sterilization?

An autoclave is used to sterilize using pressurized steam. Sterilization typically occurs at 121 degrees Celsius and 15 pounds per square inch for 15 minutes.

Explain the commercial canning process.

Uses industrial-sized autoclave called retort. Reduce 10^12 endospores to only 1 (a 12 D process). Critical because endospores could germinate in canned foods; cells grow in low-acid anaerobic conditions and produce botulinum toxin.

Describe dry heat sterilization and its applications.

Dry heat requires longer times and higher temperatures. Hot air ovens destroy cell components and denature proteins. Used for glass, powders, oils, and dry materials. Incineration burns cells to ashes and is used for medical waste.

How is filtration used to remove microbes from fluids?

Membrane filters or microfilters with small pore sizes (0.2 micrometers) are used to remove bacteria, often using a vacuum to move the fluid through the filter.

What are HEPA filters and where are they used?

High-efficiency particulate air (HEPA) filters remove nearly all microbes over 0.3 micrometers from the air. Used in specialized hospital rooms and biological safety cabinets.

How does ionizing radiation destroy microbes?

Ionizing radiation (gamma rays, X rays) directly destroys DNA and damages cytoplasmic membranes, also reacts with O2 to produce reactive oxygen species.

How does ultraviolet (UV) radiation kill microbes?

UV radiation damages DNA, used to destroy microbes in the air, water, and on surfaces, but has poor penetrating power and can be damaging to skin and eyes.

Do microwaves directly affect microorganisms?

No, microwaves do not directly affect microorganisms, but the heat they generate can be lethal. Microwave ovens heat food unevenly, so cells can survive.

How does boiling water treat drinking water?

Boiling for at least 5 minutes can be used to treat drinking water.

How is milk pasteurized?

Milk is pasteurized by heating it to 72 degrees Celsius for 15 seconds.

What items are commonly sterilized using pressurized steam (autoclaving)?

Microbiological media, laboratory glassware, surgical instruments, and other items that steam can penetrate are widely sterilized using autoclaving.

What is incineration used for?

Flaming of wire inoculating loops and destroying medical wastes and contaminated animal carcasses.

What is filtering of fluids used for?

Filtering of fluids is used for beer, wine, and to sterilize some heat-sensitive medications.

What is filtering of air used for?

Filtering of air is used in biological safety cabinets, specialized hospital rooms, and airplanes.

What is ionizing radiation used for?

Sterilizing heat-sensitive materials including medical equipment, disposable surgical supplies, and drugs such as penicillin. Also used to destroy microbes in spices, herbs, and approved types of produce and meats.

What is ultraviolet radiation used for?

Destroying microbes in the air and drinking water, and to disinfect surfaces.

What is high pressure used for?

Used to extend the shelf life of certain food products such as guacamole.

What are alcohols used for in microbial control?

Commonly used as antiseptic and disinfectant; non-toxic, inexpensive, no residue, kills vegetative bacteria and fungi. Denatures essential proteins, damages membranes.

What are some limitations of using alcohol as an antimicrobial?

Evaporates quickly, limiting contact time. Can damage rubber, some plastics, and others on inanimate objects.

What are biguanides used for in microbial control?

Extensively used as antiseptics, relatively low toxicity, Stays on skin, mucous.

What is Ethylene oxide used for?

Gaseous sterilant for heat- or moisture-sensitive items. Penetrates fabrics, equipment, implantable devices.

What are the limitations of using Ethylene oxide?

Explosive, toxic, potentially carcinogenic. Must be eliminated by heated forced air for 8 to 12 hours

How does Chlorine control microbes?

It Destroys all microorganisms and viruses and is used as disinfectant, but caustic to skin and mucous membranes

How does Idodine control microbes?

Kills vegetative cells, unreliable on endospores. Used as tincture (in alcohol)Used as iodophore (iodine complexed with a solubilizing agent, such as a surfactant or providone)

How do Phenolic Compounds (Phenolics) control microbes?

Destroy cytoplasmic membranes, denature proteins, kill most vegetative bacteria, remain effective in presence of detergents and organic contaminants and Leave antimicrobial residue.

How Quaternary Ammonium Compounds (Quats) control microbes?

Low toxicity, disinfection of food preparation surfaces, reduces surface tension of liquids, react with membrane and destroys vegetative bacteria and enveloped viruses

How do weak organic acids prevent microbial growth?

Prevent or slow microbial growth and extend shelf life. Affect cell membrane function and Control molds and bacteria in foods

How does Nitrate and nitrite preserve food?

Inhibit endospore germination and vegetative cell growth stopping the growth of Clostridium botulinum

How does refrigeration preserve perishable products?

Inhibits growth of pathogens and spoilage organisms by slowing or stopping enzyme reactions

How does freezing preserve perishable products?

Preserves by stopping all microbial growth

How do salting, adding sugar, or drying food, preserve products?

Addition of salt, sugar increases environmental solutes drawing water out of cells, dehydrating them.

How does Lyophilization (freeze drying) foods, preserve products?

Drying stops microbial growth but does not reliably kill.

Define chemotherapy in the context of microbial control.

The use of a chemical to treat disease

How does selective toxicity apply to chemotherapeutics?

It must target something SPECIFIC to the thing it wants to damage so the pathogen is harmed, but the patient remains unharmed.

How is therapeutic index calculated?

Calculated as the lowest dose toxic to patient divided by dose used for therapy lowest dose toxic to patient divided by dose used for therapy

Define antimicrobial drugs.

Interfere with the growth of microbes within a host

Define antibiotic

A substance produced by a microbe that, in small amounts, inhibits another microbe

Define Bacteriostatic chemicals

Inhibit bacterial growth and Patient's defenses must eliminate pathogen

Define Bactericidal chemicals

Kill bacteria

What are broad-spectrum antimicrobials and what are their advantages and disadvantages?

Affect a wide range are Important for treating acute life-threatening diseases but Disrupt microbiome that helps keep out other pathogens

What are narrow-spectrum antimicrobials and what are their advantages and disadvantages?

affect limited range Require identification and susceptibility of pathogen and are Less disruptive to microbiome

Describe Intrinsic (innate) resistance

For example, Mycoplasma lack cell wall, resistant to penicillin that interferes with peptidoglycan synthesis Outer membrane of Gram-negatives blocks many medications

What are the mechanisms of action of antimicrobial drugs?

Inhibition of cell wall synthesis, inhibition of protein synthesis, inhibition of nucleic acid replication and transcription, Injury to plasma membrane, Inhibition of synthesis of essential metabolites

How does chloramphenicol inhibit protein synthesis?

Binds to 50S portion and inhibits formation of peptide bond

How does Tetracyclines inhibit protein synthesis?

Interfere with attachment of tRNA to mRNA-ribosome complex

How does Streptomycin inhibit protein synthesis?

Changes shape of 30S portion, causing code on mRNA to be read incorrectly

What are the 3 inhibitors of cell wall synthesis?

ß-lactam antibiotics, glycopeptide antibiotics, and bacitracin

How do the ß-lactam antibiotics, inhibit cell wall synthesis?

Competitively inhibit enzymes that help form cross-links between adjacent glycan chains.

How do the Glycopeptide antibiotics, inhibit cell wall synthesis?

Bind to the amino acid side chain of NAM molecules, blocking formation of cross-links between adjacent glycan chains.

How do the Bacitracin, inhibit cell wall synthesis?

Interferes with the transport of peptidoglycan precursors across the cytoplasmic membrane.

How do Penicilin-binding proteins (PBPs) disrupt cell wall synthesis?

Catalyze formation of peptide bridges between adjacent glycan strands; only effective against actively growing cells

How does penicillin function?

Prevents the cross-linking of peptidoglycan by binding to penicillin binding proteins (PBPs) and interferes with the final stages of cell wall synthesis predominantly of gram-positive bacteria

What are the names of the natural penicillins?

Penicillin G and Penicillin V

What are the cephalosporins?

Mechanism of action similar to that as penicillin and Structure makes resistant to some ß-lactamases

What does Bacitracin do?

Interferes with the synthesis of linear strands of peptidoglycans.Effective against a variety of gram positive and a few gram negative bacteria

What does Vancomycin do?

Important "last line" against antibiotic-resistant S. aureus (MRSA)and Prevents the cross-linking of peptioglycan

What does Isoniazid(INH) do?

Disrupts fatty acid synthesis FAS and is a First-line medication for tuberculosis and Inhibits mycolic acid synthesis

What is Chloramphenicol and what does it do?

Broad spectrum bacteriostatic that targets large subunit blocks papeptide synthesis and Binds 50S subunit; inhibits peptide bond formation

What are Aminoglycosides?

Streptomycin, neomycin, gentamycin that cause insertion of the wrong amino acid

What does Tetracyclines do?

Broad spectrum blocks codon read from being by Interferes with tRNA attachment

What do Macrolides do?

Erythromycin/Clarithromycin - Binds 50S; prevents translocation and prevents peptide bond formation

What are Polymyxin B does?

Binds to membranes of Gram-negative bacteria and Causes the leakage of cellular molecules and inhibition of cellular respiration

Polymyxin B is used with what?

Combined with bacitracin and neomycin in over-the-counter preparation

What is Rifamycin and what does it do?

Inhibits RNA synthesis has High affinity for prokaryotic RNA polymerases that is Particularly effective against mycobacteria and Tuberculosis

How does sulfa drugs work?

Inhibit different steps in synthesis and are Structurally similar to PABA, so enzyme binds chemical (Example of competitive inhibition)

What Antifungal target

Fungal cytoplasmic membrane,Cell wall synthesis, Cell division Nucleic acid synthesis, and Protein synthesis

Describe How antifungal chemicals target ergosterol

Azoles inhibit ergosterol synthesis, membrane leaks and Polyenes produced by Streptomyces, bind to ergosterol, cause membrane to leak

How does Conventional disc diffusion method determine Antibiotic Resistance

Kirby-Bauer disc diffusion test routinely used to determine susceptibility of bacterial strain to antibiotics

What are the 4 mechanism of Antibiotic Resistance

Blocking entry,Inactivating enzymes,Alteration of target molecule,Efflux of antibiotic