CULTIVATION AND IDENTIFICATION OF BACTERIA Doç.Dr.Hrisi BAHAR Istanbul University Cerrahpasa...
-
Upload
damian-gaines -
Category
Documents
-
view
214 -
download
0
Transcript of CULTIVATION AND IDENTIFICATION OF BACTERIA Doç.Dr.Hrisi BAHAR Istanbul University Cerrahpasa...
CULTIVATION AND CULTIVATION AND IDENTIFICATION OFIDENTIFICATION OF
BACTERIABACTERIA
Doç.Dr.Hrisi BAHARDoç.Dr.Hrisi BAHARIstanbul UniversityIstanbul University
Cerrahpasa Medical Faculty Cerrahpasa Medical Faculty
WHAT IS CULTIVATION OF BACTERIAWHAT IS CULTIVATION OF BACTERIA
► The survival of microorganisms in the laboratory, as well as in nature, depends on their ability to grow under certain chemical and physical conditions
► Cultivation of bacteria is to obtain a bacterial growth under certain chemical and physical conditions .
BACTERIAL GROWTH
► An increase in population number of a bacteria by reproduction
► Not an increase in cell size
► Most bacteria reproduce by Binary Fission
◌ ◌ The cell doubles in size ◌ Replicate the chromosome ◌ Forms a septum in the center ◌ Synthesizes a cell wall at the septum ◌ Daughter cells separate
PURPOSE OF CULTURING BACTERIA
◌ ◌ Isolation of bacteriaIsolation of bacteria◌◌ Understand properties of bacteriaUnderstand properties of bacteria◌◌ To create antigen for laboratory useTo create antigen for laboratory use◌◌ To test for antibiotics sensitivityTo test for antibiotics sensitivity◌◌ Estimate viable countsEstimate viable counts◌◌ Maintain stock culturesMaintain stock cultures◌◌ Typing with bacteriophages and bacteriocins Typing with bacteriophages and bacteriocins
susceptibilitysusceptibility
A CULTURE MEDIAA CULTURE MEDIA
A culture culture mediamedia is a combination of nutrients used to growth organisms outside of their natural environment.
Culture media are employed in the
► Isolation and maintenance of pure cultures of bacteria
► Identification of bacteria according to their biochemical and physiological properties.
Why we need culture media ?► Every organism must find in its environment
all of the substances required for energy generation and cellular biosynthesis.
► The chemicals and elements of this environment that are utilized for bacterial growth are referred to as nutrientsnutrients or nutritional requirementsnutritional requirements.
► In the laboratory, bacteria are grown in culture mediaculture media which are designed to provide all the essential nutrients in solution for bacterial growth.
Definitions Definitions
●● Pure CulturePure Culture : a single “strain” of microbe grown in media.●● StrainStrain: A microbial culture which is the
descendent of a single cell originally isolated from the environment.
●● Aseptic technique:Method of hendling material without contamination from the environment.
Classification of Culture Media According their productionAccording their production
► Synthetic mediaSynthetic media► Semi- Synthetic mediaSemi- Synthetic media► Non - Synthetic mediaNon - Synthetic media
According their usageAccording their usage
◌◌ MINIMAL MEDIUMMINIMAL MEDIUM
◌◌ ALL-PURPOSE MEDIUMALL-PURPOSE MEDIUM
◌◌ SELECTIVE MEDIUMSELECTIVE MEDIUM
◌◌ DIFFERENTIAL MEDIUMDIFFERENTIAL MEDIUM
A MINIMAL MEDIUMA MINIMAL MEDIUM
●● A minimal medium is one which supplies only the minimal nutritional requirements of a particular organism .
●● These media vary in composition according to the minimal nutritional requirements of the particular species under study
AN ALL- PURPOSE MEDIUM ●● This medium is rich in a wide variety of
nutrients (including many growth factors) and will, therefore, support the growth of a wide range of bacteria
◌◌ Chocolate AgarChocolate Agar
◌◌ Nutrient Agar Nutrient Agar
◌◌ Brain Heart Infusion AgarBrain Heart Infusion Agar
◌◌ Blood Agar Blood Agar
A SELECTIVE MEDIUM
●● This media supports the growth of desired organisms while inhibiting the growth of many or most of the unwanted ones
◌◌ MacConkey Agar.
◌◌ Salmonella,shigella Salmonella,shigella
mediummedium
A DIFFERENTIAL MEDIUM ●● This medium is one which allows two or more
different types of organisms to grow. It allows identification of bacteria based on
specific properties.
●● It contains dyes and/or other components upon which different organisms act in various ways to produce a variety of end products or effects, often detected by variations in color.
◌◌ Glucose Fermentation Broth ◌◌ Three sugar iron agarThree sugar iron agar
Basic requirements of culture mediaBasic requirements of culture media ► NutrientsNutrients
- Energy source - Carbon source - Nitrogen source
► Mineral saltsMineral salts – Sulphate, phosphates, chlorides & carbonates of K, Mg & Ca.
► A suitable pHA suitable pH – 7.2 – 7.4► Accessory growth factorsAccessory growth factors
- Tryptophan for Salmonella typhi - X & V factors for H. influenzae
According to physical properties, media can be classified as three types:
1. solid medium ( 1.5~ 2.5% of agar) agar plate
2. semi-solid medium (0.3~ 0.5% of agar)
3. liquid medium
1 2 31
Agar – AgarAgar – Agar
► Solid medium is made by adding aagargar
► Agar is obtained from Sea weeds of New Zealand
► Agar contain long chain of polysaccharides, Inorganic salts and protein like substances
► Melts at 980c and solidify at 420c
Liquid Medium
► Difficult to identify all types of organisms
► Suitable for isolation of bacteria from Blood culturing or bacteria existing in small number.
IIDENTIFICATION OF BACTERIADENTIFICATION OF BACTERIA► The identification process started by isolating pure
colony by Quadrant streaking method on an appropriate culture media for the type of bacteria being targeted to be isolated.
This means:This means:
► To get suitable culture media that will allow the growth of certain species and inhibit others or
► To follow the standard and proper culturing method that enables us to isolate a pure colony.
27
Identification of bacteriaIdentification of bacteria
●● Once we have got a pure colony the next step is to identify the bacterial species.
30
Identification of bacteriaIdentification of bacteria
We start to accumulate information about the organism like:
► Morphological characteristics
► Culture characteristics and
► Physiological ( biochemical) characteristics
Bacterial Identification procedures
I- Microscopic proceduresII- Macroscopic procedures
• I- Microscopic proceduresI- Microscopic procedures ► Examination of unstained preparations (wet (wet mountmount examination examination )) for bacterial motility. ► Staining a preparation (Gram,E.ZN,GIEMSA)
Gram staining will determine:a- Bacterial Gram reactionb-Bacterial morphologyc- Bacterial strain arrangement
Bacterial Identification procedures
• II- Macroscopic proceduresII- Macroscopic procedures
1- Gram reaction confirmation test1- Gram reaction confirmation test
• On a clean slide one or two colonies are mixed with two or three drops of 4% sodium hydroxide solution:
• Gram negative bacteria will produce a mucoid line when strengthen while gram positive will not produce it.
34
Identification of bacteriaIdentification of bacteria
2- Culture appearance2- Culture appearance : :
a- The appearance of bacterial colonies
b- The effect of colony on culture media are often characteristic of the bacterial species.
36
Identification of bacteriaIdentification of bacteria
• a- The appearance of the colonies is described using conventional terms and may include:
– Shape of the colony
– Size of the colony
– Elevation of the colony
– Surface of the colony
– Color of the colony
– Opacity of the colony
– Consistency of the colony
Identification of bacteriaIdentification of bacteria
Identification need also to differentiate species following their aspects like:
1-Requirement of oxygen 2-The need of co2 3-Capacity to form pigments 4-Power of hemolysis