Chapter 7: Microbial Growth and Decontamination Flashcards
Microbial Growth
is cell division that produces new (daughter) cells and increase the total cell population
In healthcare settings, biofilms are a major concern because…
they are difficult to treat and can contribute to persistent infections
Binary Fission
occurs in most prokarotes; onvolves dividing a single cell into two cells; asexual; before dividing chromosomes replicate; parent cell begins to pinch off; partition (septum) in the center becomes complete; creates two genetically identical daughter cells
Budding
asexual reproduction; original cell eleongates then decelops a small outgrowth on one side; chromosome is duplicated and placed in the bud; separation from the mother cell occurs; performed by certain fungi and some bacteria (hyphomicrobium)
Spore Formation
performed by some fungi and bacteria; can be sexual or asexual in fungi; ALWAYS asexual in bacteria; Formation Varies- streptomyces form spores that hang off of long hypahe extensions
Generation Time
time it takes for a cell to divide; times vary; can range from 15 mins to 24 hours; depends on species and conditions; avaible nutrients impacts time; many common bacteria is less than an hour (E. coli) and some have slow (Mycobacterium tuberculosis 15-20hrs)
Binary fission leads to what type of growth?
exponential
Closed Pure Batch Cultures
means that nothing goes in and nothing goes out; the nutrients and cells that are put in are what stay in there; wastes are not removed; allows growth phases to be observed
Lag Phase
phase 1; delay that occurs while cells adjust to their new environment
Log Phase
phase 2; period of rapid exponential growth
Stationary Phase
phase 3; nutrients are depleted (but not gone) and waste accumulates; population growth rate levels off; basically growth rate is equal to death rate
Death Phase
phase 4; critical point of waste buildup and decreasing nutrients; cells begin to die; exponential death rate; **small number of the cells survive by adapting to the waste and by feeding off dead cells
Chemostat
open system; fresh growth medium is added; waste and excess cells are removed; constantly keeps them in log phase; common in industry
Temperature
low- decreases enzymatic rxns; increased- speeds up rxns and can increase growth rate; high-denature proteins and kills cell
Barophiles
can withstand the high pressure envirnoment of the deep sea
Psychrophiles
thrive between -20 and 10 degree C
Psychotrophs
grow at about 0-30 C; associated with foodborne illness
Mesophiles
grow best around 10-50 C; associated with most pathogens
Thermophiles
grow around 40-75 C; associated with compost piles and hot springs
Extreme Thermophiles
grow around 65-120 C (sterilization is 121)
Acidophiles
grow at pH 1 to pH 5; live in areas such as sulfur hot springs and volcanic vents; oftain maintain a fairly neutral cytoplasmic pH; proton pumps export excess protons from the cytoplasm to raise pH
Neutralophiles
grow best in a pH range of 5-8; make up the majority of microorganisms (human pH is about 7)
Alkaliphiles
grow in pH range of 9-11; associated with soda lakes
Halophiles
thrive in high salt environments; tolerate up to 35%; associated with the dead sea and the Great Salt Lake of Utah; normal cells would undergo plasmolysis but halophiles keep high concentrations of organic material and ions in their cytoplasm (to balance the graidents)
Faculative Halophiles
tolerate higher salt but may not grow well; ex) staphylococcus aureaus
Oxygen Levels
many microbes on this planet live either without oxygen or minimal; oxygens levels are low beneath the soil or within silt deposits in lakes and oceans; most pathogens thrive in low oxygne environemnt within the host
Reactive Oxygen Species
what some oxygen is converted into; such as superoxide ions and hydrogen peroxide; ROS can rapidly damage proteins and DNA; many microbes have evolved ways to detoxify ROS
Many Aerobe microbes rely on antioxidants to detoxify ROS…
antioxidants are compounds and enzymes; ex) superoxide dismutase converts reactive superoxide ions to hydrogen peroxide , catalse converts hydrogen peroxide to water and oxygen
Obligate Aerobes
absolute dependence on o2 for cellular processes
Microaerophiels
use only small amounts of o2; live in low o2 settings
Facultative Anaerobes
grow with and without o2; swtich between using o2 and fermentation
Anaerobes
do not use o2 in their metabolic processes
Aerotolerant Anaerobes
tolerate o2 but do not use it in their metabolic processes; have ways to deactivate ROS
Obligate Anaerobes
do not use o2 in their metabolism; can not eliminate ROS; tend to die in aerobic environments
What is 90% of a cells dry weight?
carbon, hydrogen, nongaseous oxygen, and nitrogen; other important elematents are sulfur, phosphorus, potassium, sodium, calcium, magnesium and chlorine and carious metal ions
Essential Nutrients
required to build new cells; found in the organic and inorganic compounds of a microbes environment
Macronutrients
needed in large amounts; such as carbon
Micronutrients
needed in very small amounts such as iron
Heterotrophs
require an external source of organic carbon (sugars, lipids, proteins)
Autotrophs
do not require ane xternal source of organic carbon; use carbon fixation to convert inorganic carbon into organic carbon
Growth Factors
necessary substances that a cell can not make on its own; cell must import them from their environment; they can not build their own
Fastidious Organisms
are organisms that need multiple growth factors; amino acids, vitamins, nitrogenous bases etc must be supplied in the growth media
Phototrophs
organisms that use light energy
Chemotrophs
are organisms that break down chemical compounds for energy
Photoautotroph
energy source of sunlight; inorganic carbon source (Co2); ex is cyanobacteria found in fresh water environments
Photoheterotrophs
energy source of sunglight;; organic carbon source; ex is heliobacillus mobilis foud in rice paddy fields
Chemoautotroph
energy source of nutrient breakdown; inorganic carbon source (usually co2); ex) thiobacillus dentirificans found in soil, mud and freshwater and marine sediments
Chemoheterotrophs
nutrient breakdown energy source; organic carbon source; ex is E. coli a common inhabitant of mammalian inestines
LIquid Media
ideal for growing large abtches of microbes
Solid Media
useful for isolating colonies and observing specific culture characteristics
Semisolid Media
useful for motility testing
Broth Media
made by dding various nutrients to purified water; poured into flasks or tubes and sterilized
Solid and Semisolid Media in Petri Plates
made by adding a powdered polysaccharide called agar to liquid media (add no nutrients); semi solid media contain less agar than solid media; medium is heat sterilized; while hot, the medium is poured into petri dishes; allowed to cool and solidy
Slants
cool at an angle
Deeps
cool upright
Defined Media
aka syntheitc media; chemically defined or precisely known composition; each organic and inorganic component is completely known and quatified; useful for growing autotrophs and some heterotrophs
Complex Media
aka enriched media; contains a mixture of organic and inorganic nutrients that are not fully defined; contain more complex ingredients (blood, milk proteins, extracts); precise quantity of every viteamen and nutrient si unknown; used to grow fastidious organisms with complex growth requirements
Differential Media
media formulated to visually distinguish one microbe from anotehr; common example is blood agar; a microbe is not singled out
Beta Hemolyitc
break down RBC
Alpha Hemolytic
partial break down of RBC
Gamma Hemolytic
do not lyse RBC
Selective Media
single out bacteria that have specific properties; ingredients foster the growth of certain bacteria and suppress the growht of others; ex mannitol slat agar (MSA)
Mannitol Salt Agar
selective due to its high salt content; differentiates organisms based on their ability to ferment a sugar called mannitol; it does this by the added pH indicator which detects the acids from fermentation
Anaerobic Media
molecular o2 removed from media in a number of ways; such as thioglycate is added to media which is a reducing agent and converts o2 to water
Anaerobic Jar
sample is added to chamber; packer of oxygen reating chemicals is opened inside it creating oxygen free conditions
Anaerobic Chamber
large anaerobic box; gloves are inserted into the chamber to allow handling of organisms; samples are placed in a side compartment; nitrogen and/or co2 are piped into the chamber to displace all oxygen
Streak Plate Technique
most commonly used technique to isolate bacteria; method dilutes a culture on a agar plate; individual cells are thinly separated from one another over the mediums surface; as cells divide their population increases to form a mound of cells called a colony
Direct Methods
these methods involve counting individual cells or colonies (plate counts);
Cell Counts
enumerates the number of cells in a small portion of the sample; can be done using automated or manual procedures
Manual Cell Counting
requires a microscope and a specialized counting chamber that has a volumetric grid etched on it
Flow Cytometer
direct method; uses a laser light to detect cells passing through a narrow channel; cells are fluorescently labeled before counting; ability to differentiate one cell type from another by using different colored labesl
Viable Plate Count
direct method; allows for direct enumeration of bacteria using agar plates; samples are serially diluted; applied to agar using either spread plate method or pour plate method; after an incubation period, colonies are visible and can be counted; taking the dilution factor the number of living cells are calculated; numerical data for plate counts is usually represented as CFU per millilitere (or gram); reflectts thaat sometimes a clump of cells give rise to a colon
Indirect Methods
rely on secondary reflections of overall population size
Turbidity
fast and easy was to indirectly measure cells numbers; more cells = cloudier (more turbid); spectrophotometer measures either transmission or absorbance (optical density)
Other Indirect Methods
assessing total dry weight; detecting levels of metabolic activity in a sample
Physical Analysis
involves staining and microscopy to observe morphologial features
Biochemical Analysis
involves a collection of media that assess metabolic properties
Genetic Methods
also help to quickly identify microbes; probes polymerase chain reaction (PCR), DNA fingerprinting, electrophresis seapration methods
Decontamination
removes or reduces microbial population to render an object safe for handling
Sterilization
eliminates all bacteria, viruses and endospores; required for drugs, objects used for medicla procedures and for lab media and glass ware
Disinfection
reduces microbial numbers; use for cosmetic, foods, surface, and exteral medical equipment
Refrigeration/ Freezing
slow the growth of microbes; slows food spoilage, in the lab used to preserve specimen isolates and increase the shelf life of media; refrigeration preserves clinical samples
Heat
most microbes are sensitive to heat; heat cna be used to acheive sterilization or decontamination
Decimal Reduction Time
DRT or D value; time in minutes it takes to kill 90% of a given microbial population at a set temperature; associated with disinfection
Thermal Death Time
shortest period of time at a certain temperature needed to kill all microbes in a sample
Thermal Death Point
minimum temperature needed to kill all microbes in a sample with 10 minutes
Autoclave
a machine that applies steam heat along with pressure to sterilize; used for microbiological media and assorted medical or lab equipment; most substances are sterile with 20 mins; pressure of 15 lbs per spuare inch and steam heat at 121 C
Boiling
reduces microbial numbers; “boil water adivsory” given when drinking water is contaminated; boilinh water for 5 mins eleminates most pathogenic bacteria, protozoans, and viruses; endospores can withstand hours of boiling therefore it is not an efficeint sterilization method
Pasteurization
used to eliminate pathogens; application of moderate heat (below the liquids boiling point); eliminates pathogens and reduces harmless micrbobes that cause milk spoilage
Dr Heat
incineration or hot air ovens can also be used for steriliztion or disinfection; common examples of dry heat sterilization- heating an inoculating loop; ininerating waste; placing an object at 170 C for 2 hrs in a dry heat oven
Radiation
some physical decontamination methods involve radiation or high energy waves; can sere as a disinfectant or steilization tool depending on the protocol; radiation is either ionizing or nonionizing
Ionizing Radiation
gamma ray and x rays; generate reactive ions that kill microbes and inactivate viruses; damage nucleic acids
Ionizing Radiation Passes through Packaging
useful in food and pharmaceutical industries; sterilizes medical supplies that cant be autoclaved
Nonionizing Radiation
ultraviolet (UV) rays; causes thymine dimers; alter strucutre of DNA leading to mutation; uses UV light boxes in air handling systems, sanitize drinking water and swimming pools, disinfect surfaces in operating rooms, disinfect biosafety cabinet surfaces
Filtration
large volumes of liquid or air can be passed through microbe capturing filters; filter pore sizes can even be made small enough to remove viruses; high efficiency particulate air (HEPA) filters remove microbes and allergens from the air
HEPA Filters
made of randomly arranged fibers that remove 99.7% of airborne substances; pores are 0.3 micrometer or larger; does not sterilize air
Process of Liquid Filtration
large volumes are pulled trhough the filter using a vacuum mechanism; smaller volues are pushed through syringes with filters attached to the end
Microbiocidal
germicides that kill microbes
Microbiostatic
germicides that only inhibit microbial growth
Disinfectants
used to treat inanimate objects
Antiseptics
applied to living tissue
Low Level Agents
destroy bacteria (but not TB), fungi, and some viruses but not endospores
Intermediate Level Agents
destroy all bacteria (including TB), fungi and viruses, but not endospores
High Level Agents
destroy all microbes and endospores
Critical Equipment
comes into contact with sterile body sites or the vascular system; must be sterilized
Semicritical Equipment
comes in contact with mucous membranes or non intact skin; should be free of bacteria, fungi, and vrisues with low numbers of endospores
Noncritical Equipment
contact pateints intact skin; require less stringent disinfection
Alcohols
intermediate level disinfectants; denature proteins and attack lipid membranes; ex) ethanol and isopropanol; optimal concentration is 60-90%; used to disinfect small equipment (thermometers, scissors, stethoscopes)
Aldehydes
high or intermediate level disinfectatns based on concentration; reacting with proteins and nucleic acid; ex) formaldehyde and glutaralhyde; used to sterilize. surgical instruments, endoscopes, dialyzers anestheria and respiratory equipement
Phenols
intermediate level germicides; destroy bacterial cells walls and interact with proteins; ex) used in lysol; used in personal hygiene items (soap, mouthwash) as well as clinical
Halogens
oxidize cell components; ex) chlorine and iodine compounds; chlroine bleach most widely used; used on medical equipement and floors and added to drinking water
Perooxygens
highlevel germicides at high concentrations; can be used as antiseptics and disinfectants; strong oxidizing properties; ex) hydorgen peroxide, peracetic acid
Ethylene Oxide
sterilant; damages proteins and nucleic acids; colorless gas; used for temperauter sensitive materials and equipement susceptible to moisture; applied to implant devices contain electronic parts or plastic components
Detergents
cleaning agent; amphipathic molecules; remove water soluble and water insoluble substances; some detergents damage the lipid envelope of certain viruses and the lipid membrane of certain bacterial cells
Anionic Detergents
have a negative charge and include soaps
Cationic Detergents
have a positive charge and include quaternary ammonium compounds (QACs); have bactericidal activity and are sporostatic
Facts Considered to select an Appropriate Germicide
item uses; germicide reactivity; germicide concentration and treatment times; types of infectious agents being controlled; presence of organic and inorganic matter; impact of germicicde residues on equipemnt use; germicide toxicity
Mycobacterium Control
mycobacterium species cause tuberculosis and leprosy; contain cell walls rich in waxy mycolic acids; spreads by airborne droplets; control measures target reducing airborne particlaes from infected individuals
Endospore COntrol
endospores are dormant structures; can revery to growing (vegetative) cells once favorable growth conditions are restored; endosproes survive drying, radiation, boiling, chemicals and heat treatments; most effective way to ensure elemination of endosproes is by autoclaving; other methods include hydrogen peroxide vapor at high heat or sporicides
Viral Control
virsues can be resistant to some measures; lipids in the viral envelope are sensitive to heat, drying and detergents; naked viruses are usually inactivated by chlorine based agents
Protozoan Control
different stages of a protozoan life cycle can resist certain control methods; ariety of treatments are used (filtration, carbon doxide, UV, and ozone treatments)
Prion Control
infectious proteins; withstand autocalving and chemical sterilization; surgical devices are reused after autoclaving or chemical sterilization; prions are eliminated through a combination of chemical treatments and increased temp and pressure during autoclaving
