BACTERIOLOGY

-Unicellular

-Prokaryotic

-Smallest free-living organism

-Some are spore-forming and are considered the hardiest microorganism

Characteristics of Bacteria

Cell wall, cell membrane, nucleoid, plasmid, capsule, flagella, pili, fimbriae

Structural components of bacteria

Cell wall

Used to identify bacteria; superficial layer above the cell memebrane

Cell membrane

Plasma membrane; permeable barrier; regulates movement

Nucleoid

Bacterial chromosome; single circular piece of DNA

Plasmid

Extra-chromosomal DNA

Capsule

Protective layer superficial to the cell wall

Flagella

Used for locomotion

Pili

Used for attachment and genetic exchange

Fimbriae

Non flagellar; for attachment to surfaces; shorter and more numerous than pili

Cocci, bacilli, spirochete, spirilla

Classification according to General Morphology

Cocci

Circular

Bacilli

Cylindrical/rod shaped

Spirochete

Spiral; more flexible

Spirilla

More rigid than spirochete

Pleomorphic

Means it has no definite shape

Lophotrichous(3), Polar(1), Peritrichous(×)

Flagella types

1. Gram-positive

2. Gram-negative

3. Acid-fast

4. Cell wall deficient

Classification of Bacteria According to cell wall structure

Peptidoglycan

Murane

Gram-positive bacteria

Thick peptidoglycan layer

Gram-negative bacteria

Thinner peptidoglycan layer; has second layer of LPS

Acid-Fast bacteria

Thinner peptidoglycan layer; has mycolic acid

Penicillin

Destroys the bacteria's peptidoglycan layer(murane)

Mycolic acid

A waxy layer of glucolipids, fatty acids

1. Endotoxin

2. Exotoxin

3. Invasiveness

4. Genetic recombination

5. Antibiotic resistance

Important factors that aid in virulence

Endotoxin

Cell wall component that acts as a toxin; only gram-negative can produce

Exotixins

Are toxic substances secreted by the bacterial cells; produced by gram-negative and positive

Invasiveness

Some bacteria are able to enter deep tissue by disrupting cell membrane and tissue matrix

Genetic recombination

Hardest to fight; bacteria are able to accomplish horizontal exchange of genes. This way, virulence genes can be transferred between different species

Antibiotic resistance

Natural consequence of drug exposure and results from overuse of antimicrobial agents.

1. Gram staining

2. Acid-Fast staining

3. KOH mount

4. Culture

5. Susceptibility test

Common Laboratory procedures in bacteriology

Gram staining

A microscopic exam that divides bacteria into four major groups.

1. Gram-positive cocci

2. Gram-negative cocci

3. Gram-positive bacilli

4. Gram-negative bacilli

4 major groups of bacteria in gram staining

Blue/Purple/violet

Color of gram-positive

Red/pink

Color of gram-negative

1. Crystal violet - primary stain used

2. Gram's iodine - works a s a mordant; gram+

3. Acetone alcohol - decoloriz8ng/removes primary stain

4. Safranin- counterstain; gram—

Enumerate and define Gram staining procedures

Acid fast staining

A microscopic exam used to detetct acid-fast bacteria such as Mycobacterium tuberculosis

Mycobacterium Tuberculosis

An acid-fast bacteria

Carbolfuchsin

Staining solution to identify acid-fast bacteria

Acid alcohol

Stains red (acid-fast staining)

Methylene blue

Stains non acid-fast cells

Culture

Specimens are inoculated into artificial(agar) media and incubated to allow the growth of bacteria.

The bacteria are identified through biochemical test

Susceptibility tests

Bacteria are tested against antibiotics to determine which antibiotic is most effective for therapy