Person-to-Person Bacterial and Viral Diseases — Airborne, Contact, and Sexually Transmitted Infections Explained | Chapter 31 from Brock Biology of Microorganisms

Which bacterial and viral diseases are spread directly between people, and how are they diagnosed, prevented, or treated? Chapter 31 of Brock Biology of Microorganisms surveys common airborne, direct-contact, and sexually transmitted infections, focusing on transmission routes, symptoms, pathogens, and public health strategies including vaccination and drug therapy.

Watch the full video summary below and subscribe to Last Minute Lecture for more textbook chapter breakdowns!

Airborne Bacterial Diseases

Several significant bacterial pathogens are transmitted via airborne droplets:

• Streptococcus pyogenes: Causes strep throat, which can progress to scarlet fever or rheumatic fever.
• Streptococcus pneumoniae: Common cause of pneumonia, especially in the elderly and immunocompromised.
• Corynebacterium diphtheriae: Agent of diphtheria; preventable by the DTaP vaccine.
• Bordetella pertussis: Whooping cough, also prevented by DTaP vaccination.
• Mycobacterium tuberculosis: Tuberculosis (TB); detected by skin test, chest X-ray, and sputum culture.
• Mycobacterium leprae: Leprosy, which primarily affects cooler regions of the body.
• Neisseria meningitidis: Causes meningitis and meningococcemia, diagnosed by culturing cerebrospinal fluid.

Airborne Viral Diseases

Viruses transmitted by respiratory droplets or close contact include:

• Measles (rubeola): Caused by a paramyxovirus; prevented by MMR vaccine.
• Rubella: Mild in children, but dangerous for pregnant women and fetuses.
• Mumps: Swelling of salivary glands; MMR vaccine is protective.
• Chickenpox (VZV): Can become latent and later reactivate as shingles.
• Common Cold: Usually caused by rhinoviruses and coronaviruses; managed symptomatically.
• Influenza: Multiple types (A, B, C), subject to antigenic drift and shift. Vaccines are updated annually, and antivirals like oseltamivir can reduce symptoms.

Direct-Contact Bacterial and Viral Diseases

Direct contact spreads several important pathogens:

• Staphylococcus aureus: Causes boils, impetigo, and toxic shock syndrome. Some strains are MRSA, resistant to many antibiotics.
• Helicobacter pylori: Linked to gastric ulcers, detected by gastric biopsy or urea breath test.
• Hepatitis Viruses:
  • HAV, HEV: Fecal–oral transmission.
  • HBV, HCV, HDV: Transmitted by blood or sex; HBV is vaccine-preventable.
• Ebola virus: Causes hemorrhagic fever via direct contact with body fluids.

Sexually Transmitted Infections (STIs)

STIs include both bacterial and viral diseases:

• Bacterial STIs:
  • Neisseria gonorrhoeae: Causes urethritis and pelvic inflammatory disease (PID).
  • Treponema pallidum: Syphilis; treatable with penicillin.
  • Chlamydia trachomatis: Causes nongonococcal urethritis (NGU), PID, and can lead to infertility.
• Viral STIs:
  • HSV-1 and HSV-2: Cause cold sores and genital herpes, respectively.
  • HPV: Causes genital warts and cervical cancer; vaccine is available and highly effective.
  • HIV: Destroys CD4 T cells leading to AIDS; managed with HAART (highly active antiretroviral therapy) combining RT inhibitors and protease inhibitors.

Glossary: Key Terms from Chapter 31

• Antigenic drift/shift: Minor or major changes in influenza virus antigens.
• Fusion inhibitor: Drug preventing virus entry into host cells.
• Pathogenicity island: Chromosomal region containing virulence genes.
• Viral load: Amount of virus present in the body.
• HAART: Combination therapy for HIV infection.
• Congenital infection: Infection transmitted from mother to fetus.

Conclusion: Person-to-Person Disease Transmission and Public Health

Chapter 31 highlights the diversity and significance of infectious diseases spread via air, direct contact, or sexual transmission. Understanding routes of transmission, effective diagnostic tools, vaccination strategies, and available therapies is crucial for controlling outbreaks and improving individual and public health.

For a full overview, watch the video above and subscribe to Last Minute Lecture for more textbook chapter summaries. Explore the full Brock Biology of Microorganisms playlist for all chapters!

If you found this breakdown helpful, be sure to subscribe to Last Minute Lecture for more chapter-by-chapter textbook summaries and academic study guides.

See the full Brock Biology of Microorganisms YouTube playlist here.