11/12 Microbe-Human Interactions Flashcards

Microbiota (Microbiome/Flora)

The collection of microorganisms (including fungi, bacteria, archaea, protozoa, and viruses) that exist on and in the human body, typically outnumbering human cells, existing in equilibrium with the host (showing a mutualistic relationship).

Dysbiosis

A disturbance in the balanced coexistence of the human microbiota, which can lead to infections and diseases such as obesity, allergies, and diabetes.

Sterile Body Sites

Areas of the body that should typically be free of microorganisms, such as the heart, circulatory system, liver, kidneys, bladder, lungs, brain, spinal cord, muscles, bones, ovaries/testes, glands (pancreas, salivary), sinuses, middle and inner ear, and internal eye.

Resident Microbiota 

Stable members of the human microbiota are consistently present in the body over a long period. These microbes inhabit parts of the body that are in contact with the outside environment.

Transient Microbiota

Microbes that occupy the body for a short period of time.

Factors Influencing Microbiota

Elements such as diet, hormones, and medical therapies (particularly antibiotics) that can cause fluctuations and disruptions in resident microbiota.

Superinfections

Secondary infections that may occur when normal flora are disrupted, often due to antibiotic use, leading to the overgrowth of opportunistic pathogens.

Competitive Exclusion

A mechanism by which existing resident microorganisms prevent foreign microorganisms from establishing/overgrowth by competing for attachment sites and essential nutrients.

Endogenous Infections

Infections that occur when normal flora accesses normally sterile sites within the body, such as through a laceration (a deep cut).

Eli Metchnikoff

Acknowledged as the father of immunology, he advanced the idea that not all bacteria are harmful and emphasized the beneficial properties of normal flora, suggesting dietary manipulation of gut flora.

Probiotics

Live microorganisms that, when consumed, provide established health benefits (brings the beneficial gut flora organisms back into a healthy state especially if the gut flora has been disturbed) by reestablishing beneficial gut flora, often found in fermented foods like yogurt or kimchi.

Prebiotics

Special types of food ingredients, often fibers, that our bodies cannot digest. They travel through our digestive system to the lower gut, where they act as food for beneficial microorganisms, helping these 'good' bacteria to grow and thrive (e.g., fructooligosaccharides) —stimulate the growth of beneficial microbes.

Initial Microbial Colonization

The process by which newborns acquire microbiota from the mother and environment shortly after birth, typically within 8-12 hours, with composition influenced by feeding type.

Colon (Microbial Diversity)

The body site with the highest diversity of bacteria, estimated to contain up to 10^{11} bacteria per gram of feces.

Host Defense Mechanisms (Microbiota)

Various systems like physical barriers (epithelial cells, mucus layers), gastric acid, digestive enzymes, and peristalsis that maintain microbial balance and prevent translocation.

Mutualistic Relationship (Microbiota)

A symbiotic interaction where both the human host benefits (e.g., from essential vitamins B1, B12 produced by gut bacteria) and the bacteria benefit (habitat, nutrients).

Sterile Lower Respiratory Tract

The lower respiratory tract, which should normally remain free of microorganisms.

Sterile Kidneys and Urine

Kidneys and urine, which should normally be sterile, with urine flow acting as a natural flushing mechanism.

Sites that harbor normal resident microbes

Include various body regions such as the skin and its contiguous mucous membranes, upper respiratory tract (oral cavity, pharynx, nasal, mucosa), Gastrointestinal tract (mouth, colon, rectum, anus), outer opening of urethra, external genitalia, vagina, external ear and canal, and external eye (lids, lashes, follicles). These sites provide a habitat for beneficial microorganisms that contribute to health.

Sterile fluids within an organ or tissue

Blood, urine in kidneys, ureters, bladder, cerebrospinal fluid, saliva prior to entering the oral cavity, semen prior to entering the urethra.

Sites containing well-established microbiota

Are areas of the body that support diverse and stable populations of microorganisms, contributing to host health and homeostasis. Such as, the skin (includes bacteria and fungi), GI tract & Oral cavity (includes bacteria, fungi, and protozoa). Large intestine and rectum (includes bacteria, fungi, and protozoa), upper respiratory tract, genital tract (includes, bacteria and fungi), urinary tract (includes bacteria), eye (includes bacteria), ear (includes bacteria and fungi). These sites play crucial roles in digestion, immunity, and protecting against pathogens.

Colonizers of the Human Skin: Transients

Cling to the surface but don’t grow there; influenced by hygiene.

They attach to the skin temporarily and don’t establish a permanent colony or multiply on the skin surface they are easily removed by hygiene like washing your hands.

Colonizers of the Human Skin: Residents

Stable members of the human microbiota and predictable (similar types of resident organisms (bacteria & yeast), less influenced by hygiene (they stay there even when you wash your hands), primarily bacteria and yeasts.

Infection

A condition in which pathogenic microbes penetrate host defenses, enter tissues, and multiply.

Pathogen

Any microorganism that can cause disease in a host.

Infectious disease

An infection that causes damage or disruption to tissues and organs.

Major factors in development of infection

Includes virulence factor, portals of entry, exogenous agents, endogenous agents, infectious dose (ID). Severity of the disease depends on the virulence of the pathogen and host health status.

Virulence factor

Characteristic or structure that contributes to the ability of a microbe to cause disease.

Portals of entry

Characteristic route a microbe follows to enter the tissues of the body.

Exogenous agents

Microbes that originate outside the host and can cause infection.

Endogenous agents 

Already exist on or in the body (normal Flora)

Infectious Dose (ID)

Minimum number of microbes required for infection to proceed.

True pathogens

Microorganisms capable of causing disease even in healthy people with normal immune systems.

Opportunistic pathogens

Cause disease when the host’s defenses are compromised or when they grow in part of the body that is not natural to them. These pathogens typically do not cause disease in healthy individuals.