Lecture 2: Normal Microbiota - Microbial Symbioses with Humans

How many body cells are in an adult human?

30 trillion

How many bacterial cells are in an adult human?

40 trillion

How does the microbiome help humans?

• Help maintain good health

• Can prevent growth of pathogenic microbes

• May help train the immune system to discriminate threats

Microbiome

Functional collection of different microbes in a particular environmental system

When do humans acquire normal microbiota?

Before birth

How long can normal microbiota colonize the body?

Indefinitely

What are the future benefits of knowing the human microbiome?

• Development of bio markers for predicting predisposition to disease

• Designing targeted therapies

• Personalized drug therapies and probiotics

What are the top three microbial populations on the skin?

1. Propionibacterium

2. Staphylococcus

3. Corynebacterium

What are the top three microbial populations on the saliva?

1. Streptococcus

2. Pasteurellsceae

3. Prevotella

What are the top three microbial populations on the urogenital tract?

1. Lactobacillus (more prevalent in females due to acidic conditions in the genitals)

2. Prevotella

3. Garderella

What are the top three microbial populations on the gastrointestinal tract?

1. Bacteroidetes

2. Firmicutes

3. Lentisphaerae

How can microbe colonization occur?

If body sites provide nutrients and the right environment

Transient microbiota

May colonize the body fleetingly; derived from the environment but does no cause disease

Opportunistic microbiota

Present in the body but awaiting the right opportunity

Symbiosis

Relationship between organism where at least one organism is dependent on the other

Commensalism

One organism benefits and the other is unaffected

Mutualism

Both organisms benefit

Parasitism

One organism benefits and the other is harmed

How many resident bacteria are there per square centimeter of skin?

1 million

How many skin microorganisms cover the average adult?

10 billion

What are the three microenvironments of the skin?

• Dry skin

• Moist skin

• Sebaceous (oily) skin

Where are most microbes trapped in the upper respiratory tract?

The mucus of the nasal and oral passages

How are microbes expelled in the respiratory tract?

Nasal secretions or swallowed and killed in the stomach

What illness is caused by pathogenic microbes reaching the lungs?

Pneumonia

What are the three dominate microbiota in the nose?

1. Staphylococcus aureus

2. Staphylococcus epidermidis

3. Streptococcus pneumonia

What are the three dominate normal microbiota in the nasopharynx?

1. Streptococcus pneumonia

2. Staphylococcus epidermidis

3. Staphylococcus aureus

What are the three dominate bacteria in the oral cavity and airways?

• Firmicutes

• Bacteriodetes

• Proteobacteria

What acid resistant microbacteria is able to survive in the stomach?

Heliobacter pylori

What dominate microbacteria reside in the small intestine?

• Lactobacilli

• Diptheroids

Are the bacteria that reside in the small intestine gram positive or gram negative?

Gram negative

Which body organ has the largest microbial population in the body?

Large intestine

What percentage of bacteria are anaerobic gram negative in the colon?

96-99%

What two dominate microbacteria reside in the large intestine?

• Fusobacterium spp

• Bifidobacterium

/What bacteria do breastfed infants have more of?

Commensal bacteria

Which two microbes can cause potential pathogens in the urethra and create urinary tract infections?

• E. coli

• P. mirabilis

Which organism is a resident microbe in the vagina and produces lactic acid after fermenting glycogen?

Lactobacillus acidophilus

Clostridium difficile

Spore forming and associated with antibiotic use as they are generally antibiotic resistant

Probiotics

Live organisms that confer a health benefit to the host (EX: Bifidobacterium and Lactobacillus)

Prebiotics

Typically carbohydrates that are indigestible by human hosts but provide nutrition for fermentative gut bacteria