Microorganisms and Human Relations Quiz

Host-Pathogen Interactions

• When an individual encounters a microorganism, it can cause:
  • Colonization (temporary or permanent)
  • Infection

Colonization vs. Infection

• Colonization: Host does not react against the microorganism
• Infection: Microbe causes damage to the host and initiates various pathological processes

Absolute Pathogen vs. Opportunistic Pathogen

• Absolute Pathogen: Microorganisms that indicate infection when present in the host or isolated from a clinical sample
  • Examples: Neisseria gonorrhoeae, Francisella tularensis, Plasmodium sp.
• Opportunistic Pathogen: Microorganisms that do not harm the host as long as they stay in their normal area, but can cause damage when they move to sterile body parts
  • Examples: S.aureus, E.coli, C.albicans

Normal Flora

• Placed in various parts of the human body, without damaging the host, even providing some benefits
• Basic principle: It doesn't exceed from the body region where it is
• Factors affecting the difference of normal flora:
  • Age
  • Diet
  • Health condition
  • Hormonal status
  • Personal hygiene

Permanent Flora

• A flora in/on a body side that does not change with age and regenerates in the same amount and in the same place even if it is eliminated by various effects
• They do not cause disease unless they move from their side to another side, the balance between them is not disturbed, or the immune system is adequate

Benefits of Permanent Flora

• Inhibits the placement of pathogen species by bacterial interference
• Skin's normal flora members produce unsaturated oil acids
• Intestine bacteria secrete bacteriocin such as colicin and inhibit pathogens
• Competes with pathogenic bacteria for access to nutrients and to attach to receptors in host tissues
• Stimulates the immune system to attack pathogens
• Permanent members of intestines secrete Vit.K and take a role in nutrient absorption

Harms of Permanent Flora

• Can cause infective endocarditis in people with deforming heart valves and artificial heart valves
• Can cause infection in the lower respiratory tract by aspiration of oral secretion
• Can increase and cause infections in the stomach and vagina
• Can cause urinary tract infection (especially in women)

Normal Flora of the Skin

• Many microorganisms contact with the skin surface
• Gram (+) - Coagulase negative staphylococcus (CNS), S.aureus, Corynebacterium, and Propionibacterium species
• Clostridium perfringens is isolated from the skin of approximately 20% of healthy adults
• Candida and Malassezia are also found on the skin surface of moist areas
• Streptococci can colonize temporarily
• Acinetobacter baumannii from Gram (-) bacilli can be found in the skin flora

Normal Flora of the Respiratory Tract

• Mouth, Oropharynx, and Nasopharynx:
  • Consists of 10-100 anaerobic bacteria for each aerobic bacteria
  • The most common anaerobic bacteria are Peptostreptococcus
  • The most common aerobic bacteria are Streptococcus, Haemophilus, and Neisseria species
• Lower Airway:
  • The larynx, trachea, bronchioles, and lower airways are usually sterile
  • Temporary colonization is associated with upper respiratory secretions
  • Virulent bacteria that can cause Acute Lower Respiratory Infection

Normal Flora of the Eye

• CNS colonize the surface of the eye
• Diseases are typically associated with: S.pneumoniae, S.aureus, H.influenzae, N.gonorrhoeae, and Chlamydia trachomatis

Normal Flora of the Gastrointestinal Tract

• The stomach is at an acidic pH due to hydrochloric acid
• Few species are present in its normal flora
• Lactic acid bacteria: Lactobacillus and Streptococcus
• Acid-tolerant bacteria: Helicobacter pylori (gastritis and ulcerative disease)

Test your knowledge on the interactions between microorganisms and the human body, focusing on colonization, infection, and host-pathogen interactions. This quiz is prepared by Dr. Özge Yilmazli, PhD from the Medical Microbiology Department.