Module 7 - Microbial Growth Control Flashcards
Biocide
all antimicrobial agents that can be used to control microbes
- unable to produce offspring
- process by which all living cells, spores, and acellular entities are destroyed or removed
sterilization
killing, inhibition, or removal of microorganisms that may cause disease.
disinfection
are agents, usually chemical, used to carry out disinfection and normally used only on inanimate objects
disinfectant
the microbial population is reduced to levels that are considered safe by public health standards.
sanitization
it is the prevention of infection or sepsis.
antisepsis
are chemical agents applied to tissue to prevent infection by killing or inhibiting pathogen growth
antiseptics
kill or inhibit the growth of microorganisms within host tissue
chemotheraphy
a suffix that means kills or inhibit the growth of microorganisms
-cide
a suffix that means do not kill but prevent growth
-static
A microbial cell is often defined as dead if __________that would normally support its growth.
if it does not grow when inoculated into culture medium
types of mechanical agents
depth filters and membrane filters for air and liquids
consist of fibrous or granular materials
depth filters
porous membranes, a little over 0.1 mm thick, made of cellulose acetate, cellulose nitrate, polycarbonate, polyvinylidene fluoride, or other synthetic material
membrane filters
two common examples of air filters
n95 mask and HEPA filters
masks exclude 95% of particles that are larger than 0.3 μm
n95 mask
(a type of depth filter made from fiberglass) remove 99.97% of particles 0.3 μm or larger by both physical retention and electrostatic interactions.
HEPA
two types of physical control method
heat and radiation
must be carried out at temperatures above 100°C, and this requires the use of saturated steam under pressure
moist heat
does not sterilize, but it does kill pathogens and drastically slows spoilage by reducing the level of nonpathogenic spoilage microorganisms.
pasteurization
- Intermittent sterilization
- uses steam (30–60 minutes) to destroy vegetative bacteria
tyndallization
- Less effective than moist heat
- slow and not suitable for heat-sensitive materials such as plastic and rubber items.
dry heat
required temperature for moist heat
121 degrees in celsius
required temperature for dry heat
160 degrees in celsius
-thymine dimerization of DNA, preventing replication and transcription
UV radiation
excellent sterilizing agent that penetrates deep into objects.
ionizing radiation
Chemicals can be employed for ________
sterilization, disinfection, antisepsis
- first widely used antiseptic and disinfectant
- denature proteins and disrupt cell membranes
- tuberculocidal, effective in the presence of organic material, and remain active on surfaces long after application.
phenolics
- most widely used disinfectants, antiseptics, and sanitizers
- e bactericidal and fungicidal but not sporicidal
alcohols
The two most popular alcohol germicides
ethanol and isopropanol
- used as a skin antiseptic
- They are used in hospitals for cleansing preoperative skin and in hospitals and laboratories for disinfecting. Some popular brands are Wescodyne for skin and laboratory disinfection, and Betadine for wounds.
iodine
usual disinfectant for municipal water supplies and swimming pools
chlorine
Two important eukaryotic pathogens are not killed by chlorine
Cryptosporidium and Giardia (both are microbes of diarrhea)
- are organic cleansing agents that are amphipathic, having both polar hydrophilic and nonpolar hydrophobic components.
- Their antimicrobial activity is the result of their ability to disrupt microbial membranes; they may also denature proteins.
detergents
highly reactive molecules that inactivate nucleic acids and proteins
aldehydes
Ethylene oxide is both____
microbicidal and sporicidal
Potency of a disinfectant is compared to that of phenol
Useful for screening but may be misleading
phenol coefficiency test
Developed concept of selective toxicity
Identified dyes that effectively treated African sleeping sickness
Paul Ehrlich
identified arsenic compounds that effectively treated syphilis
Sahachiro Hato
Discovered sulfonamines and sulfa drugs
Gerhard Domagk, and Jacques and Therese Trefouel
First discovered by Ernest Duchesne (1896), but discovery lost
Accidentally discovered by Alexander Fleming (1928)
• observed penicillin activity on contaminated plate
• did not think could be developed further
Effectiveness demonstrated by Florey, Chain, and Heatley (1939)
penicillin
an antibiotic active against tuberculosis,
streptomycin
ability of drug to kill or inhibit pathogen while damaging host as little as possible
selective toxicity
drug level required for clinical treatment
therapeutic dose
drug level at which drug becomes too toxic
toxic dose
ratio of toxic dose to therapeutic dose
therapeutic index
Undesirable effects of drugs on host cells
side effects
Attack only a few different pathogen
narrow-spectrum drugs
Attack many different pathogens
broad spectrum drugs
Lowest concentration of drug that inhibits growth of pathogens
minimal inhibitory concentration
Lowest concentration of drug that kills pathogen
minimal lethal concentration
Determining the level of Antimicrobial Activity
- Dilution susceptibility tests for MIC
- Disk diffusion tests – Kirby Bauer
- The E-test MIC and diffusion
Antibacterial Drugs
works as:
- Inhibitors of cell wall synthesis
- Protein synthesis inhibitors
- Metabolic antagonists
- Nucleic acid synthesis inhibition
topical and oral
disrupt membrane permeability and inhibit sterol synthesis
disrupts mitotic spindle; may inhibit protein and DNA synthesis
superficial mycoses (fungal infections of the skin, hair, and nail)
Difficult to control and can be fatal: Three (3) common drugs • Amphotericin B - binds sterols in membranes • 5-flucytosine – disrupts RNA function • Fluconazole - low side effects, used prophylactically
systemic mycoses (fungal infections affecting internal organs
Amantidine
Used to prevent influenza infections
Blocks penetration and uncoating of influenza virus
Adenine arabinoside (vidarabine)
Inhibits herpes virus enzymes involved in DNA and RNA synthesis and function
Tamiflu
Anti-influenza agent
A neuraminidase inhibitor
Not a cure for influenza, but has been shown to shorten course of illness
Acyclovir
Inhibits herpes virus DNA polymerase
Valacyclovir
Prodrug form of acyclovir
Ganciclovir
Anti-herpesvirus drugs
foscarnet
Inhibits herpes virus DNA polymerase
Anti-HIV drugs work as:
Reverse transcriptase (RT) inhibitors
Protease inhibitors
Fusion inhibitors
Evaluation of Antimicrobial Agent Effectiveness
- Department of Environment and Natural Resources (DENR)
- Food and Drug Administration
- Department of Agriculture
- Department of Health
Overcoming Drug Resistance
- Give drug in appropriate concentrations to destroy susceptible
- Give two or more drugs at same time
- Use drugs only when necessary
- Possible future solutions
• continued development of new drugs
• use of bacteriophages to treat bacterial disease
