Act 5 and 6 Flashcards
Staphylococcus aureus
Gram’s reaction: gram-positive
Shape: cocci-shaped
Arrangement: clustered
Special structure: thick
peptidoglycan layer
One disease caused: Bacterial
folliculitis
Bacillus subtilis
Gram’s reaction: Gram-positive
Shape: Rod-shaped
Arrangement: Single rods,
chains, and clumps
Special structure: It is
composed of peptidoglycan
One disease caused:
Pneumonia
Vibrio cholerae
Gram’s reaction: Gram-negative
Shape: Curved or comma-
shaped
Arrangement: Vibrio
Special structure: Single polar
flagellum
One disease caused: Cholera
Spirillum volutans
Gram’s reaction: Gram-negative
Shape: Spiral shaped
Arrangement: Polar,
Peritrichous
Special structure: It has neither
a distinct nucleus with a
membrane nor other specialized organelles.
One disease caused:
Dysentery
Borrelia burgdorferi
Gram’s reaction: Gram-negative
Shape: Long, Corkscrew shape
Arrangement: Helical shaped
spirochete
Special structure: High number
of plasmids
One disease caused: Lyme
disease
Corynebacterium diphtheriae
Gram’s reaction: Gram-positive
Shape: Rod-shaped
Arrangement: Pleomorphic,
club-shaped, single cells, in
pairs
Special structure: slender, non-
spore-forming rods
One disease caused: Diphtheria
Streptococcus pneumoniae
Gram’s reaction: Gram-positive
Shape: cocci shaped / lancet
shaped
Arrangement: diplococci
Special structure: it is
composed of peptidoglycan
and a covalently attached
wall teichoic acid.
One disease caused:
pneumonia in
immunocompromised
individuals and the elderly.
Clostridium botulinum
Gram’s reaction: Gram-positive
Shape: rod shaped
Arrangement: single, pairs, or
chains.
Special structure: it forms
vegetative endospores and
produces a protein with
characteristic neurotoxicity.
One disease caused: Botulism
Salmonella typhi
Gram’s reaction: Gram negative
Shape: Rod shaped
Arrangement: arranged in
single or in pairs
Special structure: it has
lipopolysaccharide chain on
its outer membrane, and as
well as, peritrichous flagella
that make it motile.
One disease caused: typhoid
fever
Neisseria gonorrhoeae
Gram’s reaction: Gram negative
Shape: Kidney/Coffee-bean
Arrangement: Diplococcal
Special structure: Possesses pili
on their surface
One disease caused:
Gonorrhea is a sexually
transmitted disease (STD)
caused by infection with the
Neisseria gonorrhoeae
bacterium. N. gonorrhoeae
infects the mucous
membranes of the
reproductive tract, including
the cervix, uterus, and
fallopian tubes in women,
and the urethra in women
and men.
GRAM STAINING METHOD:
- Place the prepared bacterial smear on a staining rack. Apply the following staining
solutions in order: - Flood the slide with crystal violet solution for 1-2 minutes.
- Drain or remove the stain by gently rinsing with water. Be careful not to allow a force of water to touch the smear or it will be washed off.
- Cover the smear with Gram’s iodine solution and allow to set for one minute. Gently rinse with water.
- Decolorize with drops of 95% alcohol or acetone until most of the stain comes off from the smear. Do not overdo this step.
- Gently rinse with water then counter-stain with safranin solution for 30 seconds to one minute.
- Finally, rinse gently with tap water and air-dry or blot-dry between filter papers.
- Examine the stained smear first under the oil immersion objective. Be able to differentiate the gram-positive bacteria from the gram-negative bacteria.
POTASSIUM HYDROXIDE (KOH) MOUNT:
- Using cotton soaked in 70% alcohol, sterilize the affected skin area and let dry for a few seconds. (Aside from the skin, you may also obtain fungal specimens from other
sources) - With a clean glass slide, scrape the skin (nail or hair) gently.
- Suspend the fragments of skin scales, nails or hair in a drop of 10% KOH placed on a slide.
- Add the cover slip over the drop and let sit at room temperature for about half an hour. The mount may be gently heated on the flame of the Bunsen burner to accelerate
the clearing process. Do not boil. - Examine under the microscope for fungal hyphae or spores.
PREPARATION OF BACTERIAL SMEAR:
- Place a droplet of water into a clean glass slide. Transfer a small amount of growth or bacterial colony from the plate culture to the slide and emulsify.
- Spread the material in a circular manner. Allow the smear to dry then heat fix by passing the slide through the Bunsen flame 2 or 3 times.
Why should young culture be used for Gram-stain rather than old culture
Young cultures possess an intact cell wall composition, whereas old cultures contain breaks in their cells, causing a gram variable outcome. Hence, the former must be utilized for gram staining to stipulate an accurate and effective test result.
Why is it necessary to decolorize only for a few seconds?
It is necessary to decolorize only for a few seconds because if the decolorizer stays longer, it may remove all stains for both gram-negative and gram-positive bacteria’s. This may result in inaccurate or inappropriate observations in differentiating the gram-negative and gram-positive bacteria’s.
