Microbiology Staining Techniques

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Questions and Answers

What is the primary purpose of performing a blood culture?

To assess throat infections

To identify stool pathogens

To detect cases of meningitis

To rule out bacteremia or sepsis (correct)

What is the main advantage of Gram staining?

It identifies acid-fast bacilli exclusively

It highlights all bacteria in a sample

It detects fungi in specimens

It differentiates between gram positive and gram negative organisms (correct)

Before staining a specimen, what is the first step that must be taken?

Perform a urine culture

Make a bacterial smear (correct)

Inoculate agar plates

Prepare a throat swab

Which type of specimen processing is specifically performed to detect Mycobacterium?

Sputum processing Signup and view all the answers

Which family of pathogens is specifically monitored during stool processing?

Enterobacteriaceae Signup and view all the answers

Which of the following organisms cannot be classified as Gram positive based on the given content?

Mycoplasma Signup and view all the answers

What distinguishes Acid Fast organisms from Non-Acid-Fast organisms?

Mycolic acid in the cell wall Signup and view all the answers

Which of the following is NOT classified as an Acid Fast organism?

Chlamydia Signup and view all the answers

Which of the following organisms would likely appear as Gram negative based on the information provided?

Spirilla Signup and view all the answers

Which type of organisms may substitute for Malachite Green during staining?

Bacillus Signup and view all the answers

Which of the following is classified as a solid medium?

SIM Signup and view all the answers

What is the purpose of transport media?

To maintain viability during specimen transport Signup and view all the answers

Which medium is specifically designed for biochemical testing?

Lysine Iron Agar (LIA) Signup and view all the answers

Which of the following is considered a general purpose medium?

TSB Signup and view all the answers

What type of agar is used for susceptibility testing?

Mueller-Hinton Agar Signup and view all the answers

Which type of media is characterized by a liquefiable solidifying agent?

EMB Signup and view all the answers

Which medium allows for the detection of motility in bacteria?

SIM Signup and view all the answers

What characteristic defines semi-solid media?

Contains 0.5-1% agar Signup and view all the answers

What primary virulence factor is associated with Neisseria gonorrhoeae?

Pili Signup and view all the answers

Which of the following describes the appearance of Bacillus anthracis colonies?

Disjointed bamboo fishing rod appearance Signup and view all the answers

Which test is positive for Neisseria meningitidis and indicates its capsule presence?

Neufeld Quellung Test Signup and view all the answers

What condition can be caused by Neisseria gonorrhoeae in newborns?

Ophthalmia neonatorum Signup and view all the answers

Which of the following swabs is NOT recommended for collecting samples for Neisseria gonorrhoeae?

Cotton Swab Signup and view all the answers

What characteristic differentiates Bacillus anthracis from other Bacillus species?

Non-motile Signup and view all the answers

Which of the following is a natural habitat for Neisseria meningitidis?

Oro and nasopharynx Signup and view all the answers

What type of hemolysis is produced by the genus Bacillus on Blood Agar Plates (BAP)?

Gamma hemolysis Signup and view all the answers

Which of the following treatments is used to prevent Ophthalmia neonatorum?

Crede’s prophylaxis Signup and view all the answers

Which of the following is NOT a characteristic of Bacillus anthracis colonies?

Rapidly motile Signup and view all the answers

What is the characteristic appearance of colonies on Tinsdale medium when culturing C. diphtheriae?

Black colonies with brown halo Signup and view all the answers

Which guinea pig model is protected against diphtheria toxin?

Guinea Pig A Signup and view all the answers

What primary infection site is associated with diphtheria?

Epithelial cells of the tonsils Signup and view all the answers

In which test is the presence of diphtheria toxin detected to determine immunization status?

SHICK'S TEST Signup and view all the answers

What is the primary virulence factor responsible for the symptoms associated with C. diphtheriae?

Diphtheria toxin Signup and view all the answers

Which isolation medium is primarily used for the selective growth of C. diphtheriae?

CTBA (cystine tellurite blood agar) Signup and view all the answers

What is the result of injecting a non-protected guinea pig with diphtheria toxin?

Death of the guinea pig Signup and view all the answers

What is the incubation temperature and duration for culturing C. diphtheriae on selective media?

37 °C for 24 - 48 hours Signup and view all the answers

Study Notes

Gram Staining

Differentiates between Gram-positive and Gram-negative bacteria
Primary stain is Crystal Violet
Gram-positive bacteria retain the violet dye, appearing purple
Gram-negative bacteria do not retain the violet dye, appear pink after a counterstain (e.g., Safranin)

Acid-Fast Bacilli (AFB) Staining

Distinguishes acid-fast bacilli from non-acid-fast bacilli
Acid-fast bacilli contain mycolic acid in their cell walls, making them difficult to decolorize
Used to identify bacteria like Mycobacterium tuberculosis

Purposes of Testing Specimen

Blood culture: Detects bacteremia or sepsis
CSF processing: Detects meningitis
Sputum processing: Detects Mycobacterium
Stool processing: To detect gastrointestinal pathogens, especially from the Enterobacteriaceae family
Urine culture: Detects urinary tract infections
Throat swabs: Detects pharyngitis caused by Streptococcus pyogenes
Nasopharyngeal swabs: Detects Bordetella, Haemophilus influenzae, and carriers of Neisseria

Gram Staining: Positive and Negative Organisms

Gram-positive:
- Clostridium
- Bacillus
- Erysipelothrix
- Lactobacillus
- Listeria
Gram-negative:
- Rickettsia
- Chlamydia
- Mycoplasma
- Ureaplasma
- Spirochetes

Types of Media

Liquid Media (broth):
- Tryptic Soy Broth (TSB)
- Peptone Water
- Brain Heart Infusion (BHI)
Semi-solid Media:
- SIM (Sulfur, Indole, Motility) medium
Solid Media (agar):
- EMB (Eosin Methylene Blue)
- MSA (Mannitol Salt Agar)
- Rice medium
- HBT (Hektoen Enteric Agar)
Liquefiable solid media:
- EMB, MSA
Non-liquefiable solid media:
- Simon Citrate
- Lysine Iron Agar (LIA)
- Urea agar
Transport Media:
- JEMBEC
- Cary Blair (Vibrio spp.)
- Transgrow (Neisseria)
- Amies
Biochemical test media:
- Simon Citrate
- Lysine Iron Agar (LIA)
- Urea agar
Media for Susceptibility Test:
- Mueller-Hinton Agar (MHA)
Motility test medium:
- SIM (Sulfur, Indole, Motility)

Neisseria, a Genus of Bacteria

Neisseria gonorrhoeae:
- Causes gonorrhea
- Primary virulence factor: pili
- Ferments glucose
Neisseria meningitidis:
- Causes meningitis
- Primary virulence factor: capsule
- Neufeld Quellung test positive
- Ferments glucose and maltose
- Can be normal flora

Moraxella Catarrhalis

Normal flora
Causative agent of otitis media (ear infections)

Corynebacterium Diphtheriae

Produces diphtheria toxin
Causes diphtheria
Characteristic symptom: Pseudomembrane formation
Can be differentiated from other Bacillus species by its non-motile and gamma hemolytic characteristics

Bacillus Anthracis

Forms "disjointed bamboo fishing rod appearance" with square ends
Colonies have a tenacious, sticky consistency
Lifted colonies stand like beaten egg white
Colonies may have swirling projections, appearing like a Medusa head or lion head
Shows a string of pearls pattern
Colonies have a comet tail appearance
Colonies have a cut-glass or frosted glass appearance
Forms inverted fir tree/pine tree appearance in gelatin media

Diagnostic Methods

Loeffler’s serum and PAI’s coagulated egg:
- Stimulate granule formation and pleomorphism
**CTBA (cystine tellurite blood agar): **
- Primary isolation media
- Selective media
Tinsdale medium:
- Black colonies with a brown halo
Guinea Pig A (Protected) – Inject Anti-diphtheria toxin:
- Used to determine if an animal is immune/susceptible to diphtheria
Guinea Pig B (Unprotected) – No anti-toxin:
- Used to determine if an animal is immune/susceptible to diphtheria
Shick’s Test:
- Immunity/susceptibility test for diphtheria
- Detects risk of diphtheria
VERO cell cytotoxicity assay: - Gold standard for diphtheria toxin production

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Description

Test your knowledge on key microbiology staining techniques, including Gram staining and Acid-Fast Bacilli (AFB) staining. This quiz covers the differentiation of bacteria types and various specimen testing purposes crucial for identifying infections. Perfect for students in microbiology courses!