Microorganisms and Human Relations Quiz

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30 Questions

Which of the following best describes the difference between colonization and infection?

Colonization refers to the presence of microorganisms in the host without evoking a response, while infection involves damage to the host and initiation of pathological processes.

Which of the following microorganisms is considered an absolute pathogen?

Neisseria gonorrhoeae

What is the primary characteristic of opportunistic pathogens?

They can cause damage only when they pass to sterile body parts.

Which of the following statements about the normal flora is true?

Permanent flora can cause disease if they move from their original site or if the immune system is compromised

Which of the following is a benefit of permanent flora?

Secreting bacteriocins to inhibit pathogens

What is the significance of the statement 'The larynx, trachea, bronchioles, and lower airways are usually sterile' in relation to the normal flora?

It explains why temporary colonization is associated with upper respiratory secretions

Which of the following bacteria is the anaerobic most common in the large intestine?

Bacteroides fragilis

Which bacteria makes up less than 1% of the intestinal population in the large bowel?

E. coli

In which region of the body is the gram of feces estimated to contain more than 10^11 bacteria?

Large intestine

Which of the following bacteria is commonly found in asymptomatic carriers in the small intestine?


Which of the following best describes the role of permanent flora in inhibiting pathogens?

Competing with pathogens for nutrients and receptors

What is the potential risk of using broad-spectrum antibiotics excessively?

Permanent flora bacteria overgrowing and becoming resistant

In what scenario can members of the normal flora potentially cause infective endocarditis?

When the flora changes place and invades sterile sites

Which bacteria is the most common anaerobic pathogen in intraabdominal diseases?

Bacteroides fragilis

In which region of the body can N. gonorrhoeae and C. trachomatis cause cervicitis?


Which bacteria do not dominate the urethra and can be colonized by harmful bacteria such as Enterococcus and Candida?


Which microorganism is the most common reason for vaginitis?


In the context of host-pathogen interactions, what is the primary difference between colonization and infection?

In colonization, the microbe remains in the host without causing harm, whereas infection involves damage to the host and pathological processes.

Which of the following best describes an opportunistic pathogen?

Microorganisms that have the potential to cause damage when they pass to sterile body parts, especially in individuals with immune system deficiency.

What characterizes an absolute pathogen in the context of host-pathogen interactions?

They are only considered pathogens when they cause damage to the host.

What is the most common aerobic bacteria in intra-abdominal diseases according to the text?

E. coli

Which bacteria are found in little amounts in asymptomatic carriers in the small intestine?

Salmonella and Campylobacter species

Which bacteria can cause cervicitis when colonized in the cervix?

Neisseria gonorrhoeae

Which bacteria are considered dominant but rarely a cause of diseases in the large bowel?


During which time period are newborn babies colonized with lactobacillus in the vagina?

First 6 weeks

Antacid drugs can change the normal flora of the gastrointestinal system.


E. coli makes up more than 1% of the intestinal population in the large bowel.


Neisseria gonorrhoeae is the most common reason for cervicitis in the cervix.


The most common bacteria found in asymptomatic carriers in the small intestine are Salmonella and Campylobacter species.


The gram of feces is estimated to contain less than 10^11 bacteria.


Study Notes

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.

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