PATHOLOGY - GROWTH, SURVIVAL, AND DEATH OF MICROORGANISMS

one or more nutrients in the medium become exhausted or toxic metabolic products accumulate and inhibit growth

one or more nutrients in the medium become exhausted or toxic metabolic products accumulate and inhibit growth

The exponential phase continues until one of two things happens:

aldehydes

used for low-temperature disinfection and sterilization of instruments, endoscopes, and surgical tools

peroxygens

Hydrogen peroxide (H2O2) has broad-spectrum activity against viruses, bacteria, yeasts, and bacterial spores.

fungicidal, sporicidal, virucidal

The terms ___, ___, and ___ refer to the property whereby biocides are able to kill fungi, spores, and viruses, respectively.

bacteriostatic

a specific term referring to the property by which a biocide is able to inhibit bacterial multiplication; upon removal of the agent, multiplication resumes.

antiseptic

an agent that destroys or inhibits the growth of microorganisms in or on living tissue or biologic fluids

cell concentration

the number of viable cells per unit volume of culture

long lag in growth

When cells are moved to a new environment, they might not be able to grow there because they are genetically different. This can cause a _____ before they start to grow, as a small number of cells with the right genes need time to multiply enough to show any significant increase in their numbers

stationary phase

growth ceases completely due to the exhaustion of nutrients or the accumulation of toxic products.

death phase

after a period in the stationary phase, cell viability starts to decrease at a defined rate, varying with the organism and culture conditions.

Viable But Not Culturable (VBNC) cells

this bacterial culture phenomenon is thought to be the result of a genetic response triggered in starving, stationary phase cells.

growth in biofilms

begin with a single bacterium nucleating on a surface followed by binary fission and ultimately to the formation of an intimate community of progeny bacteria

promotes increased metabolic diversity

quorum sensors

these are like the ears of the bacteria. They detect the small molecules released by other bacteria, and when they sense that enough of these molecules are around (meaning a lot of bacteria are nearby), they tell the individual bacteria to turn on specific genes. It's like a colony-wide communication system that helps bacteria coordinate their actions at the right time.

bacterial death

the irreversible loss of the ability to reproduce (grow and divide)

heat

the simplest means of sterilizing materials, provided the material itself is resistant to heat damage

100 C, 2-3 minutes

____ temp will kill all but spore forms of eubacteria within _____

121 C, 15 minutes

____ (temperature) for ____ (minutes) is used to kill spores

260

radiation that has a wavelength of about _____ nm causes thymine dimers resulting in the inability of bacterial DNA to be replicated

bisphenols

widely used in antiseptic soaps and hand rinses

heavy metal derivatives

Silver (Ag+) sulfadiazine, a combination of two antibacterial agents, Ag+ and sulfadiazine, has a broad spectrum of activity

water-repelling (hydrophobic) group and water-attracting (hydrophilic) group

Quaternary Ammonium Compounds

have two regions in their molecular structures, name both:

disinfection

a process that eliminates many or all pathogenic microorganisms, except bacterial spores, from an object or an environment

pasteurization

process of applying heat, usually to milk or cheese, for a specified period for the purpose of killing or retarding the development of pathogenic bacteria

biocide

a chemical or physical agent, usually broad spectrum, that inactivates microorganisms

bactericidal

a specific term referring to the property by which a biocide is able to kill bacteria

septic

characterized by the presence of pathogenic microbes in living tissues or associated fluids

growth in continuous culture

involves a continuous inflow of fresh

nutrients and removal of waste products, maintaining a steady-state environment for microbial growth.

growth

the orderly increase in the sum of all the components of an organism

cell multiplication

a consequence of binary fission that leads to an increase in the number of single bacteria making up a population, referred to as a culture

biomass concentration

dry weight of cells per unit volume of culture

growth rate

it is measured in grams of biomass per hour

growth in batch culture

involves inoculating a fixed volume of liquid medium with microbial cells from a previously saturated culture

exponential phase

phase in which the cells are in a steady state and grow

exponential phase

new cell material is being synthesized at a constant rate, but the new material is itself catalytic, and the mass increases in an exponential manner

glycocalyx

surrounds the bacterial community for environment protection and to keep them intact

quorum sensing

a colony telecommunication system. They release small molecules, like homoserine lactones, into their environment. When these molecules reach a certain concentration, it signals to the bacteria that there are enough of them nearby to work together

alcohols

effectively remove water from biological systems; act as "liquid desiccants"

biguanides

Chlorhexidine is widely used in hand washing and oral products and as a disinfectant and preservative. These compounds are bactericidal but not sporicidal.

organic acids

used as preservatives in the pharmaceutical and food industries

halogens

The most important types of chlorine-releasing agents are sodium hypochlorite, chlorine dioxide, and sodium dichloroisocyanurate, which are oxidizing agents that destroy the cellular activity of proteins releasing agents

phenols

Phenol and many phenolic compounds have antiseptic, disinfectant, or preservative properties. In general, these are not sporicidal

vapor-phase sterilants

heat-sensitive medical devices and surgical supplies can be effectively sterilized by vapor-phase systems using ethylene oxide, formaldehyde, hydrogen peroxide, or peracetic acid

sterilization

a process that destroys or eliminates all forms of microbial life from an object or environment. This includes highly resistant bacterial spores

sanitization

the process whereby pathogenic organisms are reduced to safe levels on inanimate objects, thereby reducing the likelihood of cross-infection

cleaning

removal of visible soil (eg, organic and inorganic material) from objects and surfaces and normally is accomplished manually or mechanically using water with detergents or enzymatic products

fungistatic, sporostatic

The terms ____ and ____ refer to biocides that inhibit the growth of fungi and spores, respectively

aseptic

free of, or using methods to keep free of, microorganisms

preservative

a substance added to food products or to an organic solution to prevent chemical change or bacterial action

antibiotic

a substance that interferes with a particular step of cellular metabolism; may be either bactericidal or bacteriostatic

heat, radiation, chemical

what are the three ways of sterilization

lag phase

a period during which cells, depleted of metabolites and enzymes as the result of the unfavorable conditions that existed at the end of their previous culture history, adapt to their new environment