Microbial Growth Control Flashcards by Cal Schiller

The ___ may be vegetative cells, endospores, protozoan cysts, fungal hyphae, viruses, etc.; and each type poses different degrees of difficulty for dealing with them

contaminant, microbes present at a given place and time that are undesirable or unwanted

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infections that develop during the course of a hospital stay and not present at the time of admission. Limit such infections by adhering to good infection control practices

Nosocomial infection (Hospital Acquired Infection)

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Nosocomial infection produce a more ____ microbe

robust

AND patients are at a lowered immune state

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Examples of levels of control of contamination

Normal household conditions

General medical conditions

Strict transmission control conditions

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assume that patients are infectious and that blood and body fluids contain pathogens; use appropriate personal protective equipment (PPE), engineering controls, and work practice controls such as handwashing

Standard Precautions (Universal)

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agents having no known potential for infecting health people. Precautions include standard good laboratory technique. Applies to teaching laboratories in a high school or college beginning level general microbiology course

BSL 1

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agents most commonly encountered in clinical samples, including HIV and several more unusual pathogens (i.e. not highly transmissible by respiratory route). Safety procedures and precautions include standard good laboratory techniques plus PPE of lab coat and gloves (for certain procedures), limiting access to the laboratory, special training of personnel in handling pathogenic agents, and performing aerosol-generating procedures in a Biosafety Cabinet (BSC).

BSL 2

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agents include those that are more unusual or more highly transmissible such as Mycobacterium tuberculosis, Brucella spp., infrequently encountered viruses, mould stages of fungi (i.e. highly transmissible by respiratory route). Precautions include Level 2 precautions plus routine use of a BSC, wearing of a HEPA-filter mask, special laboratory design and engineering features that contain potentially dangerous material by control of air movement

BSL 3

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agents are certain highly infectious exotic microbes and toxins for which there is no vaccine or effective treatment and that require the maximum containment facilities and the highest levels of special protective equipment

BSL 4

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free of all microorganisms and their spores; i.e. microbes have been destroyed or removed

Sterile

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Terms like “partially sterile” or “somewhat sterile” are ___ ; an item is either sterile or it is not.

nonsense

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BSAT

Biological Select Agents & Toxins

Special security, storage, and transport for “Select Agent”

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use of physical procedures or chemical agents to destroy all microbial forms, including bacterial spores (kill or remove the microbes).

Sterilization

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use of physical procedures or chemical agents to destroy, inhibit, neutralize, or remove at least most (but not necessarily all) potentially infectious microorganisms on an object or surface.

Disinfect / Decontaminate

Very few viable remaining microbes, low risk of transmission

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Does not imply “sterility”.

Disinfect / Decontaminate

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agent or method (usually a chemical agent) used to carry out disinfection; normally used on inanimate objects (may burn or severely irritate skin or tissue). Agents have varying levels of effect (high, intermediate, low).

Disinfectant

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Sterility can still have _____ from microbes

remnants of DNA

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use of chemical agents on the skin or other living tissue to eliminate or inhibit microorganisms; no sporicidal action is implied.

Antisepsis

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chemicals destroy spores as well as vegetative cells

Sporicidal

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Suffix that indicates the chemical or process of inhibiting (prevent) growth or multiplication of bacteria, but not killing

-stat, -static

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process of applying mild heat to kill, or significantly reduce the numbers of, microbes which may spoil food or beverage.

Pasteurization

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easily altered, decomposed or destroyed by heat

thermolabile

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Not easily altered, decomposed, or destroyed by heat

thermostable

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suffix that indicates that the chemical or process is destructive to (kills) the microbe (e.g. bacteria, fungi, viruses), although it does not necessarily kill spores

-cide, -cidal

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Overall degree of microbial resistance to killing (general sequence from most resistant to least resistant):

(1) Bacterial endospores (2) Mycobacterium (TB) (3) Protozoan cysts Below are equalish: (4) Non-enveloped small viruses (5) Vegetative bacteria (6) Fungi (7) Enveloped viruses

______ are much more resistant to antimicrobial control methods than all other microbial forms.

Bacterial endospores

____ die more rapidly than spores.

Vegetative cells

Microbes are not killed instantly when exposed to lethal agents but become _____

dysfunctional and die over a period of time

_____ are more resistant than enveloped virures because phospholipids are easily dissolved by organic solvents -- rendering them without any attachment structures

Enveloped viruses

Factors affecting the effectiveness and choice of sterilization

1. Microbial population composition 2. Microbial death (time) 3. Population size 4. Concentration/Intensity of antimicrobial 5. Duration of exposure 6. Temperature and pH 7. Presence of protective or neutralizing matter 8. Physical nature of materials being treated;

Some agents are more effective at lower concentrations; e.g. ____

70% ethanol is more effective than 95% ethanol. However, usually, more concentrated means more effective

High temperatures can inactivate ____ or denature molecules

enzymes

Strong acid can directly kill microbes; ___ may enable chemical disinfectants to inactivate microbes faster

weak acid

_____ protects or inactivates chemical disinfectants. ____ can protect microorganisms from heating and chemical disinfectants.

Organic matter (both blanks)

At higher altitudes or extreme cold temperatures, sterilization can take ____

longer

Modes of Action of Microbial Control Methods

1. Damage to cell wall 2. Disrupt cytoplasmic membrane 3. Inhibit synthesis of proteins and nucleic acids 4. Alter function of proteins & nucleic acids

Cell Wall Damage Examples

Abx, lysozomes, detergents

Disrupt cytoplasmic memrane examples

(alter membrane integrity or selective permeability) detergents (surfactants), heat

Inhibit synthesis of proteins and nucleic acids (explain and examples)

Interference with gene translation, thus preventing protein synthesis (ex: abx, radiation, formaldehyde)

Alter function of proteins & nucleic acids (explain and examples)

Alter bonds that determine secondary and tertiary structure. Altered structure inactivates or denatures functions of enzymes and nucleic acids (heat, strong organic solvents, phenolics, metallic ions, antibiotics)

slows metabolism of microbes, but does not kill most microbes

Refrigeration

____ kills cells by disrupting cell membrane functions, denaturing proteins, and inactivating nucleic acids

Heat

Cell membranes become more fluid at____, causing them to lose their selective permeability.

elevated temperatures

Proteins (e.g. enzymes) and nucleic acids are inactivated by breaking their ____, which unfolds proteins and separates double-stranded nucleic acids

hydrogen bonds

Sterilization depends on

Temperature, duration of heating, and humidity

Moist heat is ___ effective

more | because the moisture possesses greater heat energy

____ doesn't kill bacterial endospores, which may survive hours of this method

Boiling

160-180 (320-356 F) Deg C for two hours

Dry heat

Disadvantages of heat oven

Liquids cannot exceed boiling point without excessive evaporation Organic compounds may denature

121 C for 15 minutes

steam heat (length may change based off microbial load size)

The high pressure in the autoclave counteracts ____ (i.e. boiling) so that heat-stable liquids can be heated to 121°C under 15 lb of pressure without boiling over. High pressure does not cause the killing

vaporization High pressure does not cause the killing

The burning of organic material destroys living cells; used for small metal or glass instruments in the laboratory and on medical wastes at the facility or installation level. High temperature (e.g. 1800F) reduces waste to ash within several seconds; industrial size processes up to 1000 kg/hour

Incineration

Nonspecifically alters cellular proteins and nucleic acids by penetrating deep into objects

Ionizing radiation -- Gamma Used to sterilize pharmaceuticals, medical/dental supplies, and items that cannot withstand the heat of steam sterilization or the effects of chemicals

(1) Alters nucleic acid | (2) Used to decontaminate packages, e.g. by Postal Service for mail, industry for medical items

Ionizing radiation – Electron Beam Radiation

(1) Nucleic acids mutations that prevent normal gene expression and DNA replication. (2) Optimum wave length -- 240 to 280 nm (Optimum 254 nm). (3) Low penetrating power - Must have direct contact with organism. (4) Requires lengthy exposure, e.g. 10 seconds to 30 minutes depending on distance from UV light source

Non-ionizing radiation -- Ultraviolet

membrane of cellulose acetate & cellulose nitrate has complex system of pores that trap microbes by pore size and chemical affinity to the matrix

Membrane micropore filters

(1) Pore size of 0.22 micron is usually effective in removing all bacteria (i.e. sterilization) (2) Moderately effective on viruses, mycoplasma, chlamydia, and rickettsia (3) Used for sterilization of thermolabile liquids

Membrane micropore filters

______ filters consist of randomly oriented glass and polymer fibers that effectively remove 99.97% of particles 0.3um and larger

High-Efficiency Particulate Air (HEPA) filtration

Removal of particles is accomplished by adherence of particles to the fibers rather than by sieve in common paper filters in ___

HEPA filters

Types of HEPA for respiratory protection

Mask: N95, not routine surgical or painters mask PAPR: Powered Air Purifying Respirator – includes HEPA filter, blower, hood

contained work area designed to prevent exposure to infectious aerosols and to protect materials and specimens from environmental contamination. Airflow carries particulate matter away from the user and into an area of filtration, and it prevents the outflow of infectious agents. (NOT same as chemical fume hood)

Biological safety cabinet

microbicidal and sporocidal, although some may do so slowly; effectiveness approaches sterilization. Some may be sterilants under appropriate conditions

High-level disinfectants

(Effectiveness varies within category) – [Most commonly employed products] - effective against vegetative forms of bacteria and may be effective against fungi and viruses (microbicidal -- tuberculocidal, fungicidal, virucidal), but few products will be sporocidal.

Intermediate-level disinfectants

chemical disinfectant agent & method that may be safely used on skin & tissue

Antiseptic

usually (but not always) bactericidal; not sporocidal or tuberculocidal, often not fungicidal or virucidal

Low-level disinfectants

Moderately effective as a disinfectant in infection control by mechanical removal of microbes through frequent handwashing

Soap

the antibiotic will affect only the target organism (microbe) without harming the host (patient)

Selective toxicity

a chemical substance of natural, semisynthetic, or synthetic origin that inhibits or kills microorganisms and which can be used to treat or control infection.

Antibiotic / Antimicrobic agent

Mild toxicity or side effects are considered acceptable or common:

NVD

Inhibitors of cell wall synthesis

a. Beta-lactam antibiotics b. Vancomycin c. Bacitracind d. Isoniazid (INH

The antibiotic activity of these compounds depends on the integrity of the beta-lactam ring (O=C-N). By altering the nature of the side chains (R), differences in antimicrobic properties can be obtained.

Beta-lactam antibiotics (use this mechanism of action)

Beta-lactam antibiotics ex.

Penicillins (e.g. Pen G, ampicillin, methicillin, carbenicillin, piperacillin) Cephalosporins (e.g. cephalothin, cefoxitin, ceftazadime)

inhibits peptidoglycan synthesis by inhibiting the formation of crosslinks between the polymers of the bacterial cell wall

Beta lactams (Peptidoglycan synthesis consists of about 30 enzymatic steps to synthesize long polysaccharide chains of N-acetyl-glucosamine (NAG) & N-acetyl-muramic acid (NAM); and to cross link them by short peptides)

are cell-membrane enzymes (proteins) responsible for synthesizing peptidoglycan

Penicillin binding proteins (PBP)

Beta-lactam antibiotics act by binding to ______

PBPs, resulting in: - inhibition of peptidoG synthesis - degradation of cell wall (autolytic enzymes) - weakened cell wall can't preserve osmotic pressure = cell death + phagocytosis

Major characteristics of Beta-lactams

a) works poorly against existing peptidoG, so more effective GROWING bacteria b) most effective against Gram Pos c) Low toxicity d) Generally bactericidal e) Bacterial groups/generations of Abx have different spectra/resistance

Beta lactam resistance can occur due to:

i. Development of changes to PORES thus preventing entrance of antibiotic ii. Prevention of BINDING of antibiotic to PBP due to modified PBP structure iii. HYDROLYSIS of antibiotic by beta-lactamases (penicillinase, cephalosporinase)

binds onto the cross-link peptide, so that the link cannot be completed and peptidoglycan polymer cannot elongate

Vancomycin

Blocks phospholipid carrier that helps carry subunits of peptidoglycan across membrane to cell wall

Bacitracin

inhibits formation of mycolic acid in cell walls of mycobacterium (tuberculosis organism)

Isoniazid

Beta lactamase

(from a plasmid gene) - hydrolysis of beta lactam ring | fairly common

inhibits accurate translation of mRNA or polypeptide chain formation at the bacterial ribosome (principle for what broad category of ABx)

Inhibitors of protein synthesis

inhibits the polypeptide elongation steps in translation by binding to 50S ribosome subunit and blocking PEPTIDE BOND formation

Chloramphenicol, clindamycin

binds to 50S subunit; prevents TRANSLOCATION

Macrolides (e.g., erythromycin)

inhibit translation by binding to 30S ribosomal protein causing MISREADING of mRNA and incomplete synthesis of protein molecules

Aminoglycosides (e.g. gentamycin, tobramycin)

Broad-spectrum, although predominately used against various systemic gram-negative infections

aminoglycosides

Resistance most commonly results from enzymatic modification of the antibiotic

Aminoglycosides

inhibits translation into polypeptides (proteins) by blocking binding of tRNA to the 30S ribosome-mRNA complex

Tetracyclines

Resistance most commonly results from active efflux of the antibiotic out of the cell or the production of proteins that protect the 30S ribosome

Tetracycline

disrupts functional integrity of cytoplasmic membrane, allowing nucleotides and proteins to escape (detergent-like)

``` Polymyxins Amphotericin B (a polyene) ```

active against gram-negatives, but nephrotoxicity limits them to external use

Polymyxins

Antifungal; binds with ergosterol in fungal membranes; somewhat toxic

Amphotericin B (a polyene) | not an ABX!

What type of Abx might act on an essential enzyme such as DNA gyrase?

An inhibitor of nucleic acid synthesis

Inhibitors of nucleic acid synthesis examples

Quinolones Rifampin Metronidazole Nucleoside analogues (antiviral antimicrobics) Flucytosine, 5-fluorocytosine (5FC)

inhibit bacterial DNA gyrase (the enzyme that controls DNA coiling -- if DNA is not tightly coiled, it will not fit into the bacterial cell)

Quinolones (e.g. nalidixic acid) and Fluoroquinolones (e.g., ciprofloxacin)

inhibits transcription by binding to RNA polymerase and inhibiting initiation of mRNA synthesis

Rifampin

causes breakage of microbial DNA (bacterial and parasitic DNA)

Metronidazole

Inhibit DNA or RNA synthesis by altering their composition using nucleic acid analogues (structurally similar chemicals which inactivate the DNA or RNA)

Nucleoside analogues -- antiviral antimicrobics E.g., acyclovir, ribavirin, zidovudine

incorporates into fungal RNA and interferes with DNA and protein synthesis

Flucytosine, 5-fluorocytosine (5FC)

Inhibitors of bacterial metabolism (antimetabolite) Classes/Examples

Sulfonamides (sulfamethoxazole) Trimethoprim Azoles (fluconazole) -- antifungal

Similar enoguh to human metabolism so somewhat limited

Inhibitors of bacterial metabolism (antimetabolite)

inhibits folic acid synthesis by competing for precursor molecules

Sulfonamides (similar to Trimethoprim)

competitively interferes with folic acid production by inhibiting a metabolic enzyme

Trimethoprim (similar to Sulfonamide)

These two in combination are better when they act on the folic acid mechanism together

Trimethoprim | Sulfonamide

inhibits synthesis of ergosterol, a key structural molecule of fungal cell membranes

Azoles (fluconazole) -- antifungal

Antivirals

See page 17 for graphic

Microbial Growth Control Flashcards

(106 cards)