Control of Microbial Growth Lecture Flashcards
reducing or eliminating microbial
population.
microbial control
range from complete eradication of
microorganisms to the mere inhibition of
their growth, and the goal of the
treatment will influence the control
method chosen.
microbial control
only reduces the microorganisms
boiling
- the complete removal of all life forms from a given surface by
any method. Absolute
sterilization
- Treatment of an object or surface to make it safe to handle
and free from disease transmission
decontamination
reduction in the number of pathogenic microorganisms to the
point where they no longer pose a threat of disease. s
disinfection
- Less lethal process than sterilization.
disinfection
a chemical agent used in inanimate objects.
disinfectant
- a chemical agent used in human tissue to
prevent infection.
antiseptic
used on skin
antiseptic
- removal of microbes from limited area
degerming
- kills microbes
biocide/germicide
- only inhibits growth, not killing
bacterostasis
freezing is an example of what kind of microbial control
bacteriostasis
Reduce the number of pathogens to an acceptable levels for
public health
sanitation
refers to microbial contamination.
sepsis
is the absence of significant contamination.
asepsis
Removal of pathogens from living tissue
antisepsis
techniques prevent microbial contamination of
wounds.
aseptic surgery
effectiveness of antimicrobial treatment depends on (6)
Number of microbes and microbial characteristics
§ Presence of organic load such as pus, blood,
sputum and others.
§ Time of exposure
§ Type of materials to be decontaminated.
§ Method of microbial control appropriate to the
material.
§ Capacity of the facility
material with antimicrobial properties
copper
material that is resistant to corrosion
stainless steel
most resistant to least resistant
prions
endospores of bacteria
mycobacteria
cyst of protozoa
vegetative protozo
gram - bacteria
fungi including most fungal forms
virus without envelopes
gram + bacteria
virus with lipid envelopes
when to decontaminate?
§ Before and after using equipment and work surfaces.
§ Before disposing infectious materials such as gauze, wound
dressing, syringes, disposable lab materials used in
microbiology lab.
§ Before re-using re-usable materials.
common modes of action of methods of control (3)
Damage to plasma
membrane of pathogen
(bacteria, fungi,
protozoa)
Denaturation of cellular
proteins of the pathogen
Damage to DNA of the
pathogen
physical methods of control
temperature
radiation
filtration
reduction of water activity
temp of >500C, Vaporizes organic material on nonflammable
surfaces but may destroy many substances in
the process
incineration
temp of 100 C, Thirty minutes of boiling kills vegetative forms of
bacteria but may not kill bacterial endospores.
There are also toxins that are not inactivated at
100C.
Boiling
100 C, Three 30-minute intervals of boiling, followed by
periods of cooling kills bacterial endospores.
intermittent boilding
121 C for 15 minutes at 15 p.s.i
Kills all forms of life including bacterial endospores.
The substance being sterilized must be
maintained at the effective temperature for the
entire time
autoclave and pressure cooker
160 C for 2 hours/150 C for 150
minutes.
Used for materials that must remain dry. Good for
glassware, metal, but not most plastic or
rubber items.
dry heat (hot air oven)
170 C for 1 hour
Same as above. Note that increasing the
temperature by 10 C shortens the sterilizing
time by 50 %.
Dry heat (hot air oven)
63-66 C for 30 minutes
Kills most vegetative bacterial cells, including
pathogens such as streptococci, staphylococci
and Mycobacterium tuberculosis.
pasteurization (batch method)
72 C for 15 seconds
Effect on bacterial cells is similar to batch method.
For milk, this method has fewer undesirable
effects on quality or taste
pasteurization (flash methods)
Most dependable for decontamination
autoclave
the autoclave is filled with steam to a pressure of ____ resulting in a temperature of ___
15-17 psi
121 C
hazards of autoclaving for sterilization
Explosive breakage of glass vessels during opening
and unloading.
§ Burns
§ Destruction of materials due to pressure and/or heat.
For materials that can be damaged by moist
heat or are impenetrable to moist heat.
dry heat sterilization
denatures proteins- autoclave: Steam under pressure
what kind of heat
moist heat
kills by oxidation
dry heat sterilization
reduces spoilage organisms and pathogens
pasteurization
refrigeration temperature
0-7
stops all microbial growth.
low temperature
deep freezing
Not damaging to most microorganisms
and, when brought up to suitable
temperatures, the microbes will begin
growing again.
low temperature
Microorganisms preserved in liquid
nitrogen is in what temp
-196
Destroys microorganisms with
high-energy electromagnetic
waves such as gamma rays, Xrays, UV light or electron
beams.
radiation
At high levels, ____ rays and
___ rays can denature proteins.
gamma
xrays
At lower doses, gamma rays
and X-rays collide with various
molecules (often water),
producing highly reactive
species, such as ____ and
___ radicals.
hydroxyl
hydride
uses shorter wavelengths i.e.
gamma rays, X-rays, or electron beams
ionizing radiation
Principal effect is ionization of water forming hydroxyl radicals
ionizing radiation
- UV-C irradiation at wavelength 280 to 100 nm.
non ionizing radiation
UV Radiation with longest to shortest nm
UVA
UVB
UVC
UV that causes premature aging, wrinkling of skin, implicated in skin cancer
UVA
UV that causes skin cancer, cataracts, sunburn
UVB
UV that is extremely dangerous, blocked by the ozone layer
UVC
source of radiation
cathode ray tubes
use of radiation
Sterilization and decontamination in medical supplies and
food industries.
- Food preservation
– kill by heat; not antimicrobial
what electromagnetic wave
microwaves
remove of microbes from heat-sensitive
compounds such as antibiotics and vitamins.
filtration
Physically removes microbes by employing
membranes whose pores are too small to allow
their passage.
filtration
Does not effectively remove viruses from
solution
filtration
example of filtration method control
filter sterilization
§ Uses the principle of filtration
facemasks
§ Blocks release of virus-filled droplets when you cough or sneeze.
facemasks
facemasks for COVID-19
N95 respirator mask
surgical masks
filters out 95% of the smallest particles in air
(size of 0.1 to 0.3 um)
n95 respirator masks
shield large droplets from sick person
surgical masks
used in
modern microbiology
laboratories.
membrane filter
made from polymers of
cellulose acetate, cellulose
nitrate, polycarbonate,
polyester, polypropylene or
polysulfone.
membrane filter
size of membrane filters
§ 0.01µm, 0.22µm, 0.45µm
size of high efficiency particulate air filter
0.3 um
what BSL is required for processing COVID-19 related samples
BSL-3
laboratory in DLSUD is what biosafety level
BSL-2
BSL level not known to consistently cause disease in healthy adult humans and of minimal potential hazards to laboratory personnel and environment
Ex. S. cerevisiae, E.coli, non-infectious bacteria
BSL-1
BSL level that has moderate potential hazard to personnel and the environment. Includes bacteria that cause mild disease to humans, and are difficult to contract via aerosol in a lab setting
BSL-2
BSL level where microbes can either be indigenous or exotic, and they can cause serious or potentially lethal disease through respiratory transmission
BSL-3
BSL level that is dangerous, exotic, and posing a high risk of aerosol-transmitted infections, infections caused by these microbes are frequently fatal and without treatment or vaccines
BSL-4
BSL level that work on open bench, lab coat and gloves recommended, and decontamination procedures are in place
BSL-1
BSL level that is used to work with biological agents or materials with moderate risk to the people and environment
aerosol-generating procedures are performed in a biosafety cabinet
lab coat and gloves is required
biosafety manual with lab-sepcific procedures/training and restricted access
BSL-2
BSL level that has lab designed to contain airborne hazard (double door entry, negative airflow to surrounding areas, no recirculation of air)
respiratory protections usually required
BSL-3
HEPA meaning
high efficiency particulate air filter
Water can be removed from foods by
heating
evaporation
freeze-drying
addition of salt or sugar
methods directly remove water from the sample
heating
evaporation
freeze-drying
chemical methods used to control microorganisms
antibiotics
antimicrobial agents
factors to consider in using chemical control agents
product specifications
surface topography
contact time
temperature/pH
is the most commonly used alcohol for control of microorganisms
ethanol
alcohol concentration Between _____ are effective against vegetative cells
50-90%
alcohol concentration that is used for
practical purposes
70%
alcohol concentration Above ___% is effective in killing viruses.
60%
§ Used as sanitizer/antiseptic on skin at 40%
alcohol
alcohol is used as a sanitizer/antiseptic on skin at ____%
40%
Used as sanitizer/antiseptic on skin at 40%, disinfectant to clinical instruments,
thermometers and surgical instruments.
alcohol
alcohol solubilizes ___ bilayer of cell walls and membrane and create pores.
lipid
alcohol § ____ dproteins in the cytoplasm
denature
alcohol § ____ cells at very high concentration.
dehydrates
found in wax (lignin)
phenol and phenolic compounds
Has wide spectrum of antimicrobial action.
§ Kills vegetative cells by concentrated aqueous solution, bacterial
spores are resistant.
phenol and phenolic compounds
___ aqueous solution of phenol is used as disinfectant
2-4%
derivatives of phenol and phenolic compounds
cresol
chloroxylenol
chlorohexidane
hexaclorophene
phenol compound in lysol
cresol
phenol compound used as antiseptic
chloroxylenol
phenol compound as an active ingeredient of Dettol
chloroxylenol
phenolic compound used in antiseptics
chlorohexidane
phenolic compound used in soap
hexachlorophrene
mode of action of phenol and phenolic compounds
___of cell, ____of cell proteins, ___of
enzymes and ___of materials.
disruption
precipitation
ianctivation
leakage
– used in aqueous solution, tincture of iodine and
iodophore (more used).
iodine
Effective against all kinds of bacteria; possess sporicidal activity
halogen compounds
§ Fungicidal and to some extent virucidal.
halogen compounds
§ Widely used as antisepsis of skin, mucus membrane and wound.
halogen compound
Used also as disinfection of air, water and sanitation of food
utensils.
halogen compound
mode of action of halogen compounds
§ ___agents in cellular materials.
§ Halogenation of proteins resulting in ___.
oxidizing
inactivation
– in form of hypochlorite and chloramine as disinfectan
chlorine
solid chlorine disinfectant
calcium hypochlorite
liquid chlorine disinfectant
sodium hypochlorite
Aqueous solution of sodium hypochlorite at 5-25% is called
house hold bleach
is more stable than hypochlorites
chloramine
is common water disinfectant
chlorine
chlorine ratio for either in clinical and lab setting
1:10
chlorine ratio in general cleaning and household.
1:100
what chlorine is sanitizer for cooking utensils
Calcium hypochlorite
is used in bathing water
what chlorine compound
1% bleach
chlorine percentage is used in swimming pool and household purposes.
5-12%
is chlorine used as antiseptic?
no
mode of action of chlorine
§ When active form is added in water, free chlorine releases
____ ____(HClO)
hypochlorous acid
decompose to release nascent oxygen which is
a powerful oxidizing agent in cellular components.
hypocholorous acid
Hypochlorous acid decompose to release ___ ____which is
a powerful oxidizing agent in cellular components
nascent oxygen
Hypochlorous acid decompose to release nascent oxygen which is
a powerful ___agent in cellular components.
oxidizing
agent that will take electrons from DNA or enzymes
oxiziding acid
§ Most ___ metals have antimicrobial action.
heavy
heavy metals with antimicrobial action
mercury
silver
copper
mode of action of heavy metals
§ Combines with cellular ____ and ____ and inactivates them.
proteins
enzymes
heavy metal mode of action
High concentration also ____ and ___cellular proteins
and kills microbes.
coagulates
precipitates
§ Commonly used metal compounds in antiseptics
HgCl HgCl2
§ Commonly used metal compound that is bacteriostatic and bacterocidal
AgNO3
found in eyedrops used in newborn to prevent ophthalmia neonatorum
silver nitrate
§ Commonly used metal compounds used against algae and mold in pools
copper sulfate
is a bacterial or viral eye infection that can occur in newborns during the first month of life:
ophtalmia neonatorum
Formaldehyde and glutaraldehyde are examples. Both are microbicidal and
sporicidal.
aldehydes
- Stable in higher concentration and higher temp. i.e at room temp.,
formaldehyde
in room temp, aldehyde forms
para-formaldehyde
Can be gaseous or in formalin (40% solution of formaldehyde)
formaldehyde
40% solution of formaldehyde
formalin
are used for disinfectiona and sterilization of closed
room such as operation theater
vapour or formalin
r is used as disinfectant of woolen blanket, wools and
footwares of fungal infected persons.
formladehyde vapor
is used in preservation of biological specimen
formalin
Used in 2% solution
§ Effective against bacteria, fungi, spores and viruses.
§ Used to sterilize urological specimen and respiratory therapy
instruments.
glutaraldehyde
gaseous agents include
ethylene oxide
b-propiolacetone
formaldehyde
- Gaseous above 10.8C
- Have high antimicrobial activity and kill endospores.
- Used in sterilization of heat sensitive materials such as spices, oils, plastics
etc.
ethylene oxide
- Used with CO2 to form Freon.
ethylene oxide
ethylene oxide is * Used with CO2 to form ___.
freon
Gas above 15.5 C
* Less penetration power than ethylene but more active in killing
microorganisms.
b-propiolacetone
Carcinogenic, hence, less used.
b-propiolactone
- Primarily used in cleaning but has antimicrobial prop.
surfactants
surfactants means
surface-active agents
three types of surfactants
cationic
anionic
non-ionic
has more significant germicidal than the two other surfactants
cationic
cationic and is germicidal to gram pos
quaternary ammonium
Also used as disinfectants, sanitizers and antiseptics. i.e. to
floors
surfactants
surfactants Kills microorganisms by denaturing ___and interfere with
___.
proteins
glycolysis
surfactants damages ___ and ___
cell wall
cell membrane
Degerming
i.e. breaks oily
droplets by
emulsification
soap
Sanitizing (neg
charged
surfactants
reacting with cell
membranes
acid-anionic detergents
Bactericidal,
Denature
proteins, disrupt
plasma
membrane (more
active against g+
quaternary ammonium compounds
cationic detergents
§ Produces hydroxyl free radicals
§ Effective at 6% to 25% solution
§ Used as antiseptics
hydrogen peroxide
hydrogen peroxide ___ solution is used for vaporous treatment
30%
These are secondary
metabolites of some
microorganisms which inhibits
growth of microorganisms
antibiotics
Inhibits cell wall peptidoglycan
synthesis
penicillin
- Inhibits cell membrane
biosynthesis:
polymyxin
Inhibits protein synthesis:
chloramphenicol
chloramphenicol
- Reacts with nucleic acids
rifampin
- Inhibits folic acid synthesis:
sulfonamide
antibiotic that affect cell wall synthesis
beta lactams
penicillin
cephalosporin
carbapenems
monobactams
vancomycin
bacitracin
antibiotics that affect cell membrane
polymyxin
antibiotics that affect 30s subunit
tetracycline
aminoglycosides
antibiotics that affect 50s subunit
macrolides
clindamycin
linezolid
chloramphenicol
streptogramins
Denatures proteins and
solubilizes lipids
Antiseptic used on skin
ethanol, isopropanol
Denature proteins and
disrupt cell membranes
Antiseptics at low
concentrations;
phenolic compounds
Inactivates proteins
Antiseptic used on skin
tincture of iodine
Forms hypochlorous acid
(HClO), a strong oxidizing
agent
Disinfect drinking water; general
disinfectant
chlorine gas
Precipitates proteins General antiseptic and formally
used in the eyes of newborns.
Erythromycin drops (an
antibiotic) are now used
silver nitrate
Inactivates proteins by
reacting with sulfide groups
Disinfectant, although
occasionally used as an
antiseptic on skin
mercuric chloride
Reacts with NH2, SH and
COOH groups
Disinfectant, kills endospores
(sterilant)
formaldehyde
Alkylating agent Disinfectant used to sterilize
heat-sensitive objects such as
rubber and plastics
ethylene oxide gas
Disrupts cell membranes At higher concentrations and
with some compounds is a
disinfectant
detergents
