Key Pathogenic Bacteria and Tests

Infectious Diseases

Pathogenic Bacteria and Associated Diseases

Compare and contrast the morphological characteristics of various pathogenic bacteria given below and explore their role in human diseases.

• Bacillus anthracis: Anthrax
• Clostridium botulinum: Botulism
• Clostridium tetani: Tetanus
• Corynebacterium diphtheriae: Diphtheria
• Haemophilus influenzae: Influenza (flu); Bacterial Meningitis
• Mycobacterium tuberculosis: TB (Tuberculosis)
• Neisseria gonorrhoeae: Gonorrhea
• Salmonella Typhi: Typhoid Fever
• Shigella Dysenteriae: Dysentery
• Staphylococcus aureus: Boils and Pimples
• Streptococcus pneumoniae: Pneumonia
• Streptococcus pyogenes: Strep Throat; Scarlet Fever; Rheumatic Fever

Microbiology Concepts and Tests

Hemolytic Activity

Describe how hemolytic activity is classified. What type of agar is hemolytic activity observed on?

• Hemolytic activity is observed on Blood Agar.
• Classification:
  • Beta-hemolysis: Total lysis of red blood cells.
  • Alpha-hemolysis: Partial lysis of red blood cells.
  • Gamma-hemolysis: No lysis of red blood cells.

Streptococcus Differentiation

Why is it important to distinguish Streptococcus pneumoniae from other streptococci?

• To understand the kind of disease it causes.
• Streptococci are divided into three different groups based on hemolytic activity: alpha, beta, and gamma hemolytic.

Why is it important to distinguish Streptococcus pyogenes from other streptococci?

• To determine if someone has strep throat.
• This also helps to differentiate it from normal flora in some individuals.

Rheumatic Fever Diagnosis

What test should be done to diagnose rheumatic fever?

• A blood test for evidence of a recent or repeated Streptococcus infection (e.g., ASO titer).

Blood Agar Medium

Explain the purpose of blood in blood agar medium? Is blood used in Blood Agar?

• Yes, blood is incorporated into the medium.
• Purpose:
  • Provides enrichment for the growth of fastidious pathogens.
  • Cultivates Streptococcus species.
  • Demonstrates hemolytic properties of bacteria.

Streptococci Virulence Factors

Give the virulence factors for streptococci.

Plasmodium Species Identification

• Identify Plasmodium species stages (Merozoite, Trophozoite, Schizont).
• Specifically identify the signet ring stage inside red blood cells (early trophozoite).