Microbiota 1 + 2

What is the definition of 'microbiota'?

1. An assemblage of microorganisms present in a defined environment.

What is the 'human microbiota'?

The total microbial community that resides both on and within the human body.

What are the sources of the initial colonising microbiota for a newborn?

The initial colonists come from the mother's vaginal microbiota and/or the skin and surrounding environment.

Name three factors that influence the development of an individual's microbiota.

Environment, diet, and antibiotic exposure in infancy.

Where are the majority of the body's microbiota located?

The majority reside in the human large bowel (the gut).

What is 'colonisation resistance'?

It is the function of the microbiota that provides a barrier to potential pathogens.

What are two mechanisms by which the microbiota provides colonisation resistance?

By using up available space and nutrients, and by producing antimicrobials.

What can a disruption in the microbiota (dysbiosis) lead to?

Dysbiosis can lead to disease, for example, CDAD (Clostridioides difficile Associated Diarrhoea).

How does the gut microbiota influence behaviour in rodent models?

Modifying the gut microbiota can alter rodent behaviour; germ-free mice show reduced anxiety.

Which specific bacterium was cited as playing a role in intestinal angiogenesis?

Bacteroides thetaiotaomicron.

What is dysbiosis?

A perturbation or imbalance in the normal host microbiota.

What are three potential consequences of gut dysbiosis?

A bloom of potential pathogens, loss of commensal microbiota, and loss of bacterial diversity.

What is the primary cause of Antibiotic-Associated Diarrhoea (AAD)?

Dysbiosis of the gut microbiota, often following antibiotic consumption.

List three key microbiological features of Clostridioides difficile.

It is a Gram-positive, spore-forming, obligate anaerobe.

What are the two main risk factors for developing a C. difficile infection?

• Being over 65 years old

• consumption of broad-spectrum antibiotics.

What is the clinical progression of a severe C. difficile infection?

It can progress from diarrhoea to pseudomembranous colitis and then to toxic megacolon.

How does antibiotic use enable C. difficile to cause disease?

Antibiotics impair colonisation resistance by killing commensal gut microbiota.

What is the first-line antibiotic treatment for CDAD?

Oral Vancomycin (125mg, 4 times daily for 10 days).

What is Faecal Microbiota Transplantation (FMT)?

The transfer of a 'healthy' donor faecal sample to a recipient to restore a healthy microbial community.

What is the formal definition of a prebiotic?

A substrate that is selectively utilised by host microorganisms conferring a health benefit.

What is the clinical utility of Lactulose beyond being a prebiotic?

It is used as an osmotic laxative and to treat hepatic encephalopathy by reducing blood ammonia levels.

What is the formal definition of a probiotic?

Live organisms that, when ingested in sufficient amounts, have a beneficial effect on the overall health of the host.