Control of Microorganisms: Antimicrobial Agents & Physical/Chemical Methods

Comprehensive practice flashcards covering vocabulary terms, mechanisms of action, target spectrums, side effects, and physical/chemical control methods from lecture notes on antimicrobial agents and microbial control.

Selective Toxicity

The ability of an antimicrobial drug to harm or kill a pathogen without causing harm to the host organism.

Toxic Dose

The concentration of an antimicrobial agent that causes harm or damage to the host.

Therapeutic Dose

The concentration of an antimicrobial agent required to effectively eliminate pathogens in the host.

Chemotherapeutic Index

The ratio used to formulate drug safety, defined as $\text{Chemotherapeutic index} = \frac{\text{Toxic dose}}{\text{Therapeutic dose}}$.

Broad-Spectrum Drugs

Antimicrobial agents that are effective against a wide range of taxonomic groups of microorganisms.

Narrow-Spectrum Drugs

Antimicrobial agents that affect only a few specific pathogens.

Sulfonamides

Synthetic antimicrobial agents that competitively inhibit folic acid synthesis in bacteria by outcompeting essential folic acid components for binding sites in bacterial enzymes.

Isoniazid

A synthetic antibacterial agent that interferes with cell wall synthesis specifically in species of Mycobacterium, such as tubercle bacilli.

Penicillins

A class of beta-lactam antibiotics containing a beta-lactam ring that interfere with cell wall synthesis in rapidly growing bacteria, causing the cells to burst.

Beta-Lactamases (Penicillinases)

Bacterial enzymes that hydrolyze the beta-lactam ring of antibiotics such as penicillin, rendering the drug inactive and conferring resistance.

Cephalosporins

Beta-lactam antibiotics used as alternatives in cases of penicillin resistance by pathogens or penicillin allergy in patients.

Carbapenems

Beta-lactam antibiotics highly resistant to beta-lactamase enzymes, prescribed as a last resort in combination with other agents to prevent premature renal degradation.

Monobactams

Beta-lactam antibiotics, such as aztreonam, that are effective exclusively against aerobic Gram-negative bacteria like Neisseria and Pseudomonas.

Vancomycin

A glycopeptide antibiotic that inhibits bacterial cell wall synthesis in Gram-positive bacteria; used as a drug of last resort for MRSA despite potential ear and kidney damage.

Bacitracin

A polypeptide antibiotic produced by Bacillus species that interferes with the dephosphorylation of bactoprenol (C55-isoprenyl pyrophosphate) to block cell wall precursor transport; restricted to topical use due to kidney toxicity.

Polymyxins

Polypeptide antibiotics (such as Polymyxin B and Polymyxin E / Colistin) produced by Bacillus polymyxa that increase cell membrane permeability of Gram-negative rods; restricted to topical use due to kidney damage.

Daptomycin

A bactericidal antibiotic active exclusively against Gram-positive bacteria (including MRSA and GRE) by disrupting the bacterial cell membrane.

Aminoglycosides

Antibiotics (such as streptomycin, gentamicin, and neomycin) that attach to the 30S ribosomal subunit, causing mRNA misreading and blocking translation.

Tetracyclines

Broad-spectrum antibiotics with a benzene ring formation that target the 30S ribosomal subunit to block tRNA attachment; side effects include tooth staining and stunted bone growth.

Macrolides

Antibiotics (such as erythromycin, azithromycin, and clarithromycin) that bind to the 50S ribosomal subunit and inhibit polypeptide chain elongation.

Chloramphenicol

A broad-spectrum antibiotic binding to the 50S subunit reserved for severe infections (such as typhoid fever and meningitis) due to serious side effects including aplastic anemia and Gray syndrome.

Lincosamides

Antibiotics (such as clindamycin) that block tRNA binding to the 50S subunit; destruction of normal flora can allow Clostridium difficile to flourish and cause pseudomembranous colitis.

Oxazolidinones

Synthetic antibiotics (such as linezolid) that interfere with protein synthesis chain initiation on the 50S subunit; used as toxic last-resort agents against Gram-positive bacteria.

Rifampin

An antibiotic that inhibits RNA synthesis by binding to bacterial RNA polymerase; effective against tuberculosis, leprosy, and meningitis, but can cause liver damage.

Quinolones (Fluoroquinolones)

Synthetic antimicrobial agents (such as ciprofloxacin and levofloxacin) that block bacterial DNA replication and DNA synthesis.

Minimum Inhibitory Concentration (MIC)

The lowest concentration of an antibiotic that prevents visible growth of a microorganism in a tube dilution or Etest assay.

Kirby-Bauer Method

A disk diffusion antibiotic susceptibility test that measures the zone of inhibition around paper disks placed on confluent bacterial growth.

Antibiogram

A clinical summary report of local bacterial susceptibility rates used to guide empiric antibiotic selection and monitor resistance trends.

Aminoquinolines

Antimalarial drugs (such as quinine, chloroquine, and mefloquine) that accumulate in parasitized red blood cells and prevent Plasmodium species from digesting hemoglobin.

Artemisinin

An antimalarial drug derived from the Artemisin shrub that destroys Plasmodium parasites by releasing free radicals inside red blood cells.

Praziquantel

An antihelminthic drug that alters membrane permeability, inducing contraction and paralysis in flukes (trematodes) and tapeworms (cestodes).

Mebendazole

An antihelminthic agent that inhibits glucose uptake and ATP synthesis in intestinal worms such as nematodes and cestodes.

Avermectins

Antihelminthic drugs (such as ivermectin) that affect the nervous system of parasites to cause paralysis; used against a wide range of roundworms.

Sterilization

The treatment of an object or material to ensure complete destruction or removal of all living microbes, spores, and viruses.

Microbicidals (Germicidals)

Physical or chemical agents that specifically target and kill microorganisms.

Sanitization

The process of reducing the numbers of pathogenic microorganisms or discouraging their growth on inanimate surfaces to safe public health levels.

Microbiostatics

Agents (including disinfectants and antiseptics) that discourage or inhibit the growth and multiplication of microbes without necessarily killing them.

Thermal Death Point (TDP)

The minimum temperature at which a given microbial species dies within a specified time period.

Thermal Death Time (TDT)

The length of time required to kill a specific microbial species at a given temperature.

Incineration

An extreme form of dry heat control that uses direct flame to burn contaminated objects and microbial life to ash.

Autoclaving

A moist heat sterilization procedure that uses pressurized steam at $15\,psi$ ($103\,kPa$) and $121^\circ\text{C}$ for $15\text{--}30\,\text{minutes}$ to kill vegetative cells and endospores.

Holding Method (LTLT Pasteurization)

Low-Temperature Long-Time pasteurization where milk is heated to $63^\circ\text{C}$ ($145^\circ\text{F}$) for $30\,\text{minutes}$ and rapidly cooled.

Flash Pasteurization (HTST Pasteurization)

High-Temperature Short-Time pasteurization where milk is heated to $72^\circ\text{C}$ ($161^\circ\text{F}$) for $15\,\text{seconds}$ and quickly cooled.

Ultra-High-Temperature (UHT) Sterilization

A thermal process where milk is heated to $135\text{--}150^\circ\text{C}$ ($275\text{--}302^\circ\text{F}$) for $1\text{--}4\,\text{seconds}$ to produce a sterile, shelf-stable product.

Lyophilization

A food preservation method (freeze-drying) where items are frozen with liquid nitrogen and then subjected to a vacuum pump to draw off water.

Desiccation

The removal of water or moisture necessary for microbial metabolism and survival, used as a preservation method.

HEPA Filter

High-efficiency particulate air filter designed to trap airborne microorganisms above a specific size threshold.

Antiseptics

Chemical agents formulated to destroy or inhibit pathogenic microorganisms directly on living tissue.

Disinfectants

Chemical agents used on inanimate objects or surfaces to reduce or eliminate pathogenic microbes.

Degerming

The mechanical removal of organisms from an object or skin surface, such as washing with soap or scrubbing before an injection.

Phenol Coefficient (PC)

A numerical value comparing the disinfecting potency of a chemical agent to that of phenol under identical standardized conditions; a value above 1 indicates greater efficacy than phenol.

Quaternary Ammonium Compounds (Quats)

Cationic detergents containing a nitrogen core that react with cell membranes, causing cytoplasm leakage and destroying certain bacteria and viruses.

Ethylene Oxide

A carcinogenic and explosive sterilizing gas used on heat-sensitive plastics and equipment as the chemical counterpart to autoclaves.

Chlorine Dioxide

A nontoxic, noncarcinogenic sterilizing gas used for decontaminating buildings and materials, such as mail exposed to anthrax spores in 2001.