Bacterial Pathogens Overview

Bacterial Pathogens

• Staphylococcus aureus: Gram-positive, transmitted by skin contact or contaminated surfaces. Causes skin infections, food poisoning, and toxic shock syndrome. No vaccine available. Virulence factors include superantigens (overactivating the immune system) and protein A (immune evasion).

• Streptococcus pyogenes: Gram-positive, transmitted via respiratory droplets or skin contact. Causes strep throat, scarlet fever, and rheumatic fever. No vaccine. Its virulence factors include M protein (inhibiting the immune response) and streptolysins (destroying red and white blood cells).

• Clostridium tetani: Gram-positive, transmitted by contaminated wounds. Causes tetanus (lockjaw). A vaccine (tetanus vaccine) exists. The toxin, tetanospasmin, blocks nerve signals, causing muscle spasms.

• Escherichia coli (E. coli): Gram-negative, transmitted by contaminated food/water or fecal-oral route. Causes gastroenteritis, urinary tract infections, and hemolytic-uremic syndrome. No vaccine (although animal vaccines exist). Some strains have virulence factors like Shiga toxin (damages the intestinal lining) and adhesins (attach to the intestinal lining)

• Neisseria meningitidis: Gram-negative, transmitted through respiratory droplets. Can cause meningitis and bloodstream infections. Vaccination is possible. Its capsule evades the immune system, and endotoxin causes inflammation.

• Neisseria gonorrhoeae: Gram-negative, transmitted through sexual contact. Causes gonorrhea. No vaccine. Virulence factors include pili (for sticking to host cells) and antigenic variation (to evade immune detection).

• Treponema pallidum: Neither gram-positive nor gram-negative (spirochete). Transmitted through sexual contact, or congenitally. Causes syphilis. No vaccine available. Outer membrane proteins aid in host attachment, and immune evasion occurs due to limited surface antigens.

Viral Pathogens

• Hepatitis A: RNA genome, transmitted through the fecal-oral route (contaminated food/water). Causes acute hepatitis. A vaccine exists. It does not result in chronic infections.

• Hepatitis B: DNA genome, transmitted through blood, sexual contact, or perinatally. Causes chronic hepatitis and potentially liver cancer. A vaccine exists. It integrates into the host genome, leading to a potential lifelong infection.

• Hepatitis C: RNA genome, transmitted through blood exposure (e.g., needles, transfusions). Causes chronic hepatitis and liver cancer. No vaccine is available. Its high mutation rate complicates vaccine development.

• Influenza: Segmented RNA genome, transmitted through respiratory droplets. Causes the flu. Vaccination is available. Two key factors in its evolution are antigenic drift (small mutations) and antigenic shift (major genetic recombination, often causing pandemics).

• HIV: RNA retrovirus. Transmitted through blood, sexual contact, or perinatally. Causes AIDS (acquired immunodeficiency syndrome), weakening the immune system. No vaccine is available. Targets CD4+ T cells and integrates into host DNA, making eradication challenging.

• COVID-19 (SARS-CoV-2): RNA genome, transmitted through respiratory droplets and close contact. Causes COVID-19. A vaccine is available. The spike protein targets ACE2 receptors, and variants can exhibit immune escape.

Test your knowledge on common bacterial pathogens including Staphylococcus aureus, Streptococcus pyogenes, Clostridium tetani, and Escherichia coli. Learn about their transmission methods, diseases caused, and virulence factors. This quiz provides a comprehensive overview of these significant infectious agents.