Microbiology Finals (Part 1 of 3)

Destruction or removal of all forms of microbial life including endospores but
with the possible exception of prions.

Sufficient heat treatment to kill endospores of Clostridium
botulinum in canned food.

Destruction of vegetative (non-endospore-forming) pathogens.

Destruction of vegetative pathogens on living tissue.

Chemical applied

Removal of microbes from a limited area, such as the skin around an injection
site.

Treatment intended to lower microbial counts on eating
and drinking utensils to safe public health levels.kills fungi

Names of treatments that cause the outright death of microbes have the suffix

kills microorganisms (usually with certain exceptions,
such as endospores)

kills fungi

inactivates viruses

treatments only inhibit the growth and multiplication of bacteria

from the Greek for decay or putrid, indicates bacterial contamination

means that an object or area is free of pathogens

are important in surgery to minimize contamination from the
instruments, operating personnel, and the patient.

Actions of Microbial Control Agents

Several factors influence the effectiveness
of antimicrobial treatments

The more microbes there are to begin with, the
longer it takes to eliminate the entire population

The presence of organic matter often inhibits the
action of chemical antimicrobials.

Chemical antimicrobials often require extended exposure
to affect more- resistant microbes or endospores

The concluding section of this chapter discusses
how microbial characteristics affect the choice of chemical and physical
control methods

Physical Methods
of Microbial Control

were probably among the earliest techniques.

➢ preserved canned goods represent one of the
most common methods of food preservation
➢ is also usually used to sterilize laboratory media
and glassware and hospital instruments
➢ kill microorganisms by denaturing their enzymes;

is the lowest temperature at
which all the microorganisms in a particular liquid
suspension

the minimal length of time
for all bacteria in a particular
liquid culture to be killed at a given temperature

kills microorganisms primarily by coagulating proteins (denaturation),
which is caused by breakage of the hydrogen bonds that hold the proteins in their
three-dimensional structure.

kills vegetative forms of
bacterial pathogens, almost all viruses, and fungi and their spores with in about 1O
minutes, usually much faster

preferred method of sterilization

Large industrial autoclaves

used mild heating, which was sufficient to kill the
organisms that caused the particular spoilage problem
without seriously damaging the taste of the product.
• Principle: eliminate pathogenic microbes, lower
bacterial number

72°C, 15 seconds

sterilization, no need
for refrigeration

kills by oxidation effect

Simplest methods of dry heat sterilization is

effective way to sterilize and dispose of contaminated
paper cups, bags, and dressings

placed in oven 170 C 2 hours

is the passage of a liquid or gas through
a screen like material with pores small enough to
retain microorganism

• Absence of water
• Microorganisms cannot grow or reproduce
but can remain viable for years

EXAMPLE OF DESSICATION

The use of high concentrations of salts and
sugars to preserve food

has various effects on cells, depending on its wavelength,
intensity, and duration.

TWO TYPES OF RADIATION

wavelength shorter than that of non-ionizing
radiation, less than about 1 nm. Carries much more energy
Ex. gamma rays, X rays, or high –energy electron beams

has a wavelength longer than that
of ionizing radiation, usually greater than about 1 nm
Ex: UV lights

Types of Disinfectants

contain a molecule of
phenol that has been chemically altered to reduce its irritating
qualities or increase its antibacterial activity in combination with a
soap or detergent

was the first to use phenol (carbolic acid) to control surgical
infections in the operating room

• injuring lipid-containing plasma membranes, which results in
leakage of cellular contents.
• Mycobacteria are susceptible

One of the most frequently used phenolics is derived
from

not sporicidal but have some activity against
enveloped viruses

Example of Biguanides, which is frequently used for microbial control on
skin and mucous membranes

iodine and chlorine

➢ is one of the oldest and most effective antiseptics. It is
active against all kinds of bacteria, many endospores, various
fungi, and some viruses.
➢impairs protein synthesis and alters cell membranes,
apparently by forming complexes with amino acids and
unsaturated fatty acids.

➢ as a gas or in combination with other chemicals,
is another widely used disinfectant

that forms when
chlorine is added to water →strong oxidizing agent that prevents much of the cellular
enzyme system from functioning.

is used as a household disinfectant and bleach (Cl

effectively kill bacteria and fungi but not endospores and nonenveloped
viruses

can be biocidal or antiseptic

Example of heavy metals

small amount of heavy metal
that exerts its antimicrobial activity

is used as an antiseptic in a 1% silver nitrate
solution

decrease surface tension among
molecules of a liquid.

Example of surfactants

Soap breaks the oily film into tiny
droplets, a process called

most widely used surface-active agents

Quaternary ammonium compounds are strongly
bactericidal against

Popular quats: