8. Normal Flora

What are sterile sites in the body?

Sites that should have no microorganisms under normal conditions, including blood, CSF, lower respiratory tract, inner/middle ear, upper urinary tract/bladder, and synovial fluid.

What Staphylococcus species is normal flora on the skin of dogs?

Staphylococcus pseudintermedius.

What Staphylococcus species is normal flora on the skin of cats and large animals?

Staphylococcus aureus.

What is the "brick and mortar" skin barrier?

A protective barrier where lipid "mortar" (ceramides) between skin cells prevents entry of bacteria and viruses and keeps skin hydrated.

What bacteria and yeast are normally present in low numbers in the ears of small animals?

Gram-positive cocci (Staphylococcus, Streptococcus) and Malassezia yeast.

What Gram-negative rod is a common ear pathogen that is NOT normally found in dogs' ears?

Pseudomonas aeruginosa.

What are four factors that can lead to bacterial overgrowth in the ears?

Poor ventilation (increased moisture), ear canal conformation, hair/obstructions, skin barrier disruptions (allergies), or immunocompromise.

What does dark brown waxy debris in the ear typically suggest?

Yeast or Gram-positive bacterial overgrowth.

What does pale tan/yellow debris in the ear typically suggest?

Gram-negative bacteria such as Proteus or Pseudomonas.

What does "coffee ground" appearance in the ear suggest?

Ear mites.

What Gram-negative bacteria is a normal inhabitant of the oral cavity in cats?

Pasteurella multocida.

What is the difference between aerobic, anaerobic, and facultative anaerobic bacteria?

Aerobic require oxygen; anaerobic cannot survive in oxygen; facultative anaerobes can survive in both oxygen and oxygen-free environments.

Name the five main bacterial phyla normally found in the GI tract of dogs and cats.

Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, and Actinobacteria.

Why are bacterial counts low in the stomach?

Due to the acidic environment.

What are bacteriophages?

Viruses that infect and replicate within bacteria.

What are three benefits of the normal GI microbiome?

Protection from invading pathogens, stimulation of the immune response, and production of nutrients (SCFAs) for colonocytes.

What are short-chain fatty acids (SCFAs) and what is their function?

They are produced by anaerobic bacteria in the colon and provide energy for colonocytes (cells lining the colon).

What is intestinal dysbiosis?

Disruption of the normal GI microbiome, which can involve overgrowth of normal flora, invasion of pathogens, or toxin production.

What are prebiotics?

Substances that "feed" healthy GI tract bacteria (e.g., fructooligosaccharides, psyllium) to promote their growth.

What are probiotics?

Ingestion of live beneficial bacteria to help restore or alter the microbiome.

What three things should a quality probiotic product list?

1) Type of bacteria (genus and species), 2) Number of CFU/g (colony-forming units per gram), and 3) Peer-reviewed studies performed on the product.

What is a synbiotic?

A product that contains both prebiotics and probiotics.

What is fecal microbiota transplantation (FMT)?

A procedure where donor feces is administered via enema or endoscopy to share positive microflora and restore balance.

What is rumen transfaunation?

Transferring the "cud" (rumen contents) from a healthy cow to another cow to share beneficial microbiomes.

What are the three ways intestinal dysbiosis can occur?

Overgrowth of microorganisms normally present, invasion of pathogenic bacteria/viruses/fungi, or abnormal bacteria producing exotoxins.

What is the "last resort" for returning to normal flora?

Antibiotics (after nutrition, prebiotics, probiotics, and fecal transplantation have been considered).

What type of bacteria is Clostridium perfringens in dogs?

A bacterium that can produce enterotoxins and contribute to intestinal dysbiosis.

Why is it important to use sterile technique when sampling sterile sites?

To ensure no contamination occurs that might affect the accuracy of culture results.

What is the role of anaerobic bacteria in the colon?

They ingest undigested food and sloughing cells, and produce SCFAs that provide energy for colonocytes.