Animal Diseases: Lecture 2 Study Material from Rutgers University

Types of symbiotic relationships

- Commensal

- Mutualistic

- Parasitic

- Pathogenic

Where do infections begin in animals?

At sites in the animal's mucous membranes

most microorganisms are _________

benign

normal microbial flora

Microorganisms usually found associated with human body tissue

When are humans and animals colonized by microorganisms?

at birth

T/F: Skin is a dry, acid environment that supports the growth of most microorganisms

False; does NOT support the growth

The oral cavity is a complex, __________ __________ ___________

heterogeneous microbial habitat

Saliva contains what?

Antimicrobial enzymes

The tooth consists of a ________________ surrounding _____________________

mineral matrix (enamel); living tissue (dentin and pulp)

Accumulation of microflora of oral cavity steps

1. Bacteria colonize tooth surfaces

2. Extensive growth of oral microorganisms (streptococci) causes thick bacterial layer (dental plaque)

3. Plaque continues to develop --> anaerobic bacterial species begin to grow

4. Microorganisms produce high concentrations of acid = decalcification of tooth enamel (dental caries)

What bacteria are common agents in denal carries?

lactic acid bacteria Strep sobrinus and strep mutans

Microbial habitats for mammals

mamalian gut, rumen and ruminant animals

Plant fibers composed of __________

insoluble polysaccs --> cellulose most abundant component

foregut fermentation

fermentation chamber precedes the small intestine

hindgut fermentation

uses cecum and/or large intestine

Ruminants

foregut fermenters

Ruminants posses what special digestive organ?

rumen

____________________________ digested with the help of microbes in the rumen

Cellulose and other plant polysaccharides

Rumen microbes synthesize what for their animal host?

aa and vitamins

Rumen microbes can serve as what to their host when directly ingested?

source of protein

T/F: Aerobic bacteria dominate in the rumen

FALSE; anaerobic dominate in rumen

What causes changes in the rumen flora?

abrupt changes in an animal's diet

What is a potential cause from abrupt changes in an animal's diet?

Acidosis (rumen acidification)

What is also abundant in the rumen?

Anaerobic protists and fungi

All sites on a human that contain microorganisms are part of ____________________

microbiome

Humans are ____________ and ____________

monogastric and omnivorous

Microbes in human gut affect _________ , ___________ and predisposition to _______________

early development, health; disease

Colonization of gut for humans begins when?

at birth

T/F: There is high variability in gut communities between different individuals

True

Intestinal microorganisms carry out a variety of what that produce what?

essential metabolic rxns; various compounds

The type and amount of compounds produced in the GI tract is influenced by what?

by the composition of the intestinal flora and diet

What compounds are produced from intestinal microorganisms?

Vitamins, gas, organic acids, odor, and enzymes

What organisms colonize the upper respiratory tract?

staphylococci, streptococci, diphtheroid, bacilli, and gram (-) cocci

T/F: Lower respiratory tract has microflora in healthy individuals

False; respiratory tract lacks microflora

T/F: The bladder is typically sterile in both males and females

True

What can cause potential pathogens in the urethra to multiply and become pathogenic?

altered conditions such as change in pH

Vagina of the adult female is __________ ___________ and contains significant amounts of ______________

weakly acidic; glycogen

What organism resides in the vagina?

Lactobacillus acidophilus

What does lactobacillus ferment and produce in the vagina?

ferments glycogen and produces lactic acid

What does lactic acid do for the vagina?

maintain a local acidic environment

Pahtogens

microbial parasites

Pathogenicity

ability of a parasite to inflict damage on the host

Virulence

measure of pahtogenicity

Opportunistic pathogen

causes disease only in the absence of normal host resistance

Host defenses

1. Barriers

2. Innate Immunity

3. Adaptive immunity

How is infection contained in innate immunity?

phagocytic cells

What response triggers adaptive immunity?

innate response

When a host is compromised what does this mean for resistance mechanisms?

one or more resistance mechanisms are inactive

Probability of infection is ______________ when a host is compromised

increased

Innate resistance

natural host resistance

tissue specificity

physical and chemical barriers

What are the different routes of transmission?

1. respiratory system (airborne)

2. digestive system (food/waterborne)

3. placenta (vertical)

4. urethra (contact)

5. vagina (contact)

6. skin (contact/vector)

What is a vector?

Disease that results from an infection transmitted to humans and other animals by blood-feeding anthropods

What is a reservoir?

A place where microorganisms survive, multiply, and await transfer to a susceptible host

Virulence

the relative ability of a pathogen to cause disease

How can virulence be estimated?

from experimental studies of the LD50

LD50

the amount of an agent that kills 50% of the animals in a test group

Attenuation

decrease or loss of virulence

toxicity

organism causes disease by means of a toxin that inhibits host cell function or kills host cells

T/F: Toxins can travel to sites within host not inhabited by pathogen

true

Invasiveness

ability of a pathogen to grow in host tissue at densities that inhibit host function

Invasiveness can cause ...

damage w/o producing a toxin

How do pathogens enhance pathogenicity?

using ac combo of toxins, invasiveness, and other virulence factors

quorum sensing

The ability of bacteria to sense the presence of other bacteria via secreted chemical signals.

Steps of pathogenesis

1. exposure

2. adherence

3. invasion

4. colonization and growth

5. toxicity/invasiveness

6. tissue damage/disease

pathogen invasion begins where?

at the site of adherence

Pathogen may spread throughout the host via what systems?

circulatory/lymphatic systems

Damage is done by pathoge after?

pathogen gains access to host tissues and multiplies

How do bacteria and viruses initiate infection?

By adhering to epithelial cells through macromolecular interactions

How can bacterial adherence be facilitated?

1. Extracellular macromolecules not covalently attached to bacterial cell surface

2. Fimbriae and pili

4 ways pathogens adhere to animal tissues

1. glycocalyx (slime)

2. viral glycoprotein

3. fimbriae

4. adhesive disc

Pathogen produce enzymes that ...

- enhance virulence that breaks down/alters host tissue

- protect pathogen by interfering w/ normal host defense mechanisms

Why is availability of nutrients important for pathogen?

it affects their growth

T/F: Pathogen grow locally at site of invasion or may spread throughout body

true