microbiology

sample origin

sample origin

live animal, dead animal, animal environment

specimen collection

• from actual site of infection

• as early as possible

urine

• max conservation : 8h

• stored in sterile syringe, tube

pasteurization

food preservation, under 100° C, eliminate pathogens but not spores

sterilization

• heat

  • dry : flame, 160-180° C, denature pathogens

  • moist : cooking in water, steam sterilization ( 15-30min, 120°C)

• Filtration

• Irradation

• Chemical agent

• Must not contains microorganism able to multiply

Disinfection

• with chemical agents

  • for material non infectious to human and animal

Lyophilization

freeze drying

frozen -- water removed -- vacuum

Cultivation

method of multiplying microorganism in artificial medium providing optimum environment

culture media

specific mixtures of nutrients that support growth of microorganism

culture

microorganism cultivated in lab

non- fastidious bacteria

able to grow in petri dish

fastidious bacteria

require sepcial additional nutrient

unculturable bacteria

don’t grow in lab

liquid media

bacteria growth seen by turbidity

solid media

broth with agar as solidifier

semisolid media

broth with agar -- for motility

nutrient broth

for most culture media

peptone media

for sugar media

nutrient agar

nutrient broth plus agar

blood agar

nutrient agar plus blood (5-10%)

red opaque medium

chocolate agar

blood agar then raised at 100°C to rupture red cells

brown opaque medium

for isolation of fastidious organism

selective media

contain inhibit substance to inhibit growth of unwanted bacteria ( ex: antibiotics)

MacConkey Agar

Indicator media

To distinguish one microorganism from another

ex : blood agar

how : by colour changes ( depends on interaction of bacteria with medium )

MacConkey agar

it contains bile salt, lactose and neutral red ( bcm hot pink on low ph, bcs lactose fermenting colonies produce acid), inhibit gram + B growth

XLD agar

for isolation of Gram - bacterias

giemsa stain

differential staining, basic dyes, for intracellular microbes, parasites, viruses and when blood smear

--- dont differentiate gram + and -

acid fast organism

resist to decoloration by acids thanks to waxy sibstances in cell wall --- Gram +

Zhiel- neelsen stain -- acid fast stain

special bacteria stain for acid-fast organism n b

types of microscope

light microscope -- with a lens, uses low-power, high- power and oil immersion objectives

electron microscope -- with electrons and a magnetic field ( uses SEM for 3D view)

resolwing power

ability to distinguish images of 2 close objects as separate

the greater the better

Bright field microscopy

direct light source, specimen appears color of stain

size of mircoo units

micro meter or nanometer

dark field

uses special condenser

specimen appears lighted in dark background ²

Fluorescence

immunofluorescence

phase contrast microscopy

varying degrees of darkness

show cell structures without using dyes

electron microscopy

show viruses and minute structure

stain with heavy metals

wet mounts

examination of lives cells ( for motility and morphology)

used for : rapid pre ID or characterize microo grown in culture

uses high- dry objective of the light microscope

uses saline, dry fast

hanging drop mount

for motility

brownian motion : random motion of particles in a medium

uses cavity slide, vaseline and paraffin

fixed mount slides

thin film of material that will be fixed by heat ( over bunsen burner) or by chemicals ( methanol) -- will kill the microorganism -- stain with dyes

negative staining

obesrvation of microorganism capsule

dark backgroung with carbon particles ( cannot go in capsule)

giemsa stain dyes

basic -- methylene blue

acid-- azure and eosin

-- do not differentiate gram positive and gram negative