Test 1 Flashcards
what is the function of pili?
Adhesion Virulence Conjugation Facilitate identification (diagnosis)
What common bacteria utilizes Pili as a function of virulence?
E. coli
Name 2 functions of the bacterial plasmid
virulence factors antibiotic resistance genes can be transferred between bacteria
define a pathogen
an organism that causes disease in a normal host
define pathogenicity
the ability of an organism to cause disease in a immunocompetent host
define virulence
relative measure of pathogenicity
what is defined as, the number of bacteria needed to cause an infection in 50% of exposed animals
Infectious dose 50
MLD?
minimum lethal dose
what is the difference between apparent and inapparent infection
apparent infection is an infection with overt Dz (example canine ehrichiosis) inapparent infection is an infection without the presence of overt Dz (example normal microbiota)
what are the 4 events of almost every infectious DZ
- Encounter 2. Entry 3. Multiplication and spread (infection) 4. Damage (pathogenesis)
define the “ingress” mode of entry for a pathogen
when a pathogen enters without crossing an epithelial barrier
give 2 examples of pathogen independent methods where by an organism can gain entry through epithelial penetration
insect transmission catheters blood transfusion infected needle
what is the inoculum size, and why is it important?
The amount of pathogen that you are exposed to. the inoculum size is a prime determinant in the outcome of exposure
what is the advantage for Staphylococcus Aureus to lyse RBCs
they lysis of RBCs will release hemoglobin, there by gaining access to Iron that the body is sequestering from the bacteria via transferrin
how is streptococcus equi distributed throughout the body?
through the lymphatic system
what is an endotoxin
constitutive part of the gram negative cell wall
is an endotoxin part of a gram -, gram + bacteria? or both?
only a Gram -
Do exotoxins come from a Gram -, or Gram + bacteria, or both?
Both
how does streptococcus pneumoniae evade phagocytic engulfment?
the production of a capsule protects the bacteria from the phagosomes
by what means does Rickettsia spp. escape phagocytosis?
the production of phospholipase that lyses the phagosome membrane
what is immunopathology? and what are some examples?
it is when the immune system it’s self causes damage immune complexes granuloma formationo
what are some examples of granuloma forming Dz’s
Rhodococcal pneumonia tuberculosis Johne’s Dz R. equi
What are the two cell types that cannot be identified using a gram stain?
Mycobacteria, and Mycoplasma
what is the exotoxin that streptococci produces that allows it to spread through tissues?
hyaluronidase
what is the toxin that is produced by staphylococci that aids in lysing the cell
hemolysins
diphtheria toxin stops the movement of ________ on host cellular mRNA
ribosomes
what is the main cause of “travelers diarrhea” ?
Enterotoxigenic E. coli
C. tetani is an obligate __________ found in soil and feces
anaerobe
Tetansopasmin toxin ascends to the spinal cord via……..
retrograde axonal transport
Tetanospasmin causes rigid muscle ____________
contraction
C. tetani secretes ___________ that causes cell death and necrosis
tetanolysin (hemolysin)
define opisthotonus
from the greek word opisthen meaning “behind”, and tonos meaning tenssion, is a severe state of hyperextension
what species are the most susceptible to tetanus toxin?
Horse > human > dog > cat > bird
what is a toxoid?
inactivated toxin that induces antitoxin
what is an antitoxin
production of a specific antibody to a specific toxin following natural infection
if you have an animal with an active Dz from a toxin, would you treat with a toxoid? or an antitoxin?
antitoxin
clostridium botulinum is a gram _____ _____, and is an obligate ______
positive rod anaerobe
T or F C. botulinum can cause Dz without entering the host
True, just the toxin is required within the host to cause Dz
what mediates the botulism Dz, the bacteria? or the bacterial exotoxin?
the exotoxin
toxicoinfectious botulism is a rare form where th bacteria multiply in the _____________ then produce the toxin which is absorbed __________
intestinal tract systemically
shaker foal syndrome is caused by toxidoinfectious botulism, where the bacteria replicate within the __________, this is also known as___________
intestinal tract floppy baby syndrome
how does tetanus toxin and botulism toxin differ in the site of action
tetanus acts on the CNS botulism acts on the peripheral nerve endings
botulism causes __________ whereas tetanus causes _________
flaccidity rigidity
why is the big limitation on the antitoxin for botulism?
it can only inactivate toxins that have not been bound, has 0 effect on bound toxin
what is the risk of using antibiotics when facing Botulism Dz
you can destroy the normal flora in the intestional tract, allowing room for colonization of C. botulinum
T or F Toxoids can protect cross species
FALSE
T or F an endotoxin is an important component of all gram + bacteria
False, it is Gram -
define immunogenic
the ability to create an immune response
what component of the endotoxin does the body most commonly produce an antigen against?
the O antigen
why is the O antigen of an endotoxin so effective?
it will physically inhibit the ability of macrophages and neutrophils to phagocytose the bacteria
what role do bile acids play in microbiota endotoxin within the intestinal tract?
they will detoxify the endotoxins before they can be absorbed
what are some common Dz in animals that are due to endotoxins
coliform mastitis diarrhea pneumonia pleuritis
T or F Endotoxins are responsible for very little damage to the cell and surrounding tissue
True most of the damage stems from inflammatory mediators
endotoxins in low concentrations will activate _______ by the __________ pathway
compliment alternative
what is the result of endotoxins in ↑ concentrations?
endotoxic (hypovolemic) shock
what is the pathogenesis of hypovolemic shock in ↑ concentrations of endotoxins
Prostaglandin release leads to vasodilation → leukotrienes and cytokines lead to increased vascular permeability → stimulation of coagulation resulting in DIC
define endotoxemia
presence of endotoxin in the blood
define bacteremia
presence of viable bacteria in the blood
what is the difference between endotoxemia, bacteremia, and septicemia
endotoxemia = presence of endotoxin in the blood, but no viable bacteria bacteremia = presence of viable bacteria in the blood septicemia = bacteremia associated with clinical signs
What pathogen causes disease in animals
ETEC E.Coli
T or F ETEC causes damage to enterocytes and hemorrhage
False ETEC does not cause cell damage, hemorrhage, inflammation, or foul smelling feces.
What Type of Diarrhea does ETEC cause?
Hypersecretory
Where does ETEC attach in the intestine?
Small Bowl on the apical surface of the enterocytes
T or F ETEC does not secrete enterotoxins
False ETEC secretes a Heat Labile and a Heat Stable enterotoxin
What are 3 non-diarrheal E.Coli syndromes?
Cattle: coliform mastitis Chicken: Omphalitis (bac T infection of yolk sac Dog: UTI
Salmonella will be gram positive or gram negative when stained?
Negative
Define Facultative Anaerobe
It uses either oxidative phosphorylation or fermentation (Growth with or without oxygen)
What are the two most common pathogens for food borne illness?
S.Typhimurium S.Enteritidis
T Or F Salmonella is part of the normal GI Microbiota
False
What is the most common source of contamination for Salmonella?
FECES, POop! 💩
What host factors help prevent infection and disease of Salmonella?
- Reduction of viable challenge bacteria due to innate defenses 2. Inhibition of binding to target intestinal epithelial cells due to competition and anti microbial production by NORMAL flora
What are 3 factors that PROMOTE successful Salmonella infection?
- Virulence of Serotype 2. High Challenge Dose 3. Host Susceptibility
What is the Multiplication and Spread step for Salmonella?
Salmonella INVADES the intestinal epithelium -next they traverse the epithelial cell -finally they invade the lamina propria and progress to the messenger in lymph nodes and the bloodstream in lamina propria salmonella multiply and stimulate extensive migration of neutrophils and phagocytes into lamina propria. INFLAMMATION Macrophages eat bacteria Salmonella survives in the macrophage (lysosomal resistant, facultative intercellular pathogen)
T or F To diagnosis chronic salmonella infection one only needs a Single fecal culture to be diagnosed.
False, you need multiple fecal samples because carriers may shed the virus only intermittently
What type(s) of diarrhea does salmonella cause?
Malabsorption: Causes direct cellular damage and inflammation, thus meaning that there is a decrease in nutrient absorption, and cell death and HEMORRHAGE Exudative: inflammatory response leads to leakage Hypersecretion: Inflammatory mediators :prostaglandins and bradykinins) activate adenylate Cyclase which leads to secretion
What are some differences between ETEC and Salmonella??
Define gastroenteritis
a syndrome characterized by GI symptoms including nausea, vomiting, diarrhea, and abdominal discomfort
Define diarrhea
abnormal fecal discharge characterized by frequent and or fluid stool
Define dysentery
an inflammatory disorder of GI tract often accompanied with blood and pus in feces
Define enterocolitis
Inflammation involving the mucosa of both small and large intestines
E. coli is a ___________ anaerobe which means…….
facultative, and can grow with or without the presence of oxygen
E. coli is an ______cellular bacteria
extracellular
what are the 4 primary pathotypes of E. coli?
enterotoxigenic E. coli (ETEC) enteropathogenic E. coli (EPEC) enterohemorrhagic E. coli (EHEC) enteroinvasive E.coli (EIEC)
define a pathotype
a group of strains of a single species that cause a common Dz using a common set of virulence factors
define a serogroup
an antigenically distinct variety of serotype, based only on O (LPS) antigens
define serotype
an antigenically distinct varient within a bacterial species
T or F you are able to pridict pathogenicity based on the O, H, and K antigens on a given bacterial pathogen
False they are used to separate the bacteria into groups
T or F ETEC is a part of the normal microbiota of most animals
True it is ubiquitous in the farm environment and is shed in feces.
What receptor is required for ETEC to bind on epithelial cells?
CHO containing receptors
This pathotype of E. coli is most common in neonates (less then 3 days old)
ETEC
Why is ETEC only able to produce Dz the first few days of life
the intestinal receptors required for adhesion are only present in young animals
ETEC cause a ____________ diarrhea.
hypersecretory
what is the pathogenesis by which ETEC causes hypersecretory diarrhea
inhibits absorption of Na+ and Cl- in the villi, and ↑ secretion of Cl- in the crypts → hypersecretion
T or F ETEC cause severe damage to bound epithelium
False there is no direct damage to the epithelium to which it is bound
what is the gold standard test for diagnosis of ETEC
Multiplex PCR looking specifically for virulence factors
how does EPEC differ then ETEC with respects to mucosal damage?
EPEC adheres to small bowel enterocytes and destroys the normal microvillar architecture. Cytoskeletal derangements are accompanied by an inflammatory response and diarrhea
Shigells dysentery and which E. coli pathotype share a similar toxin?
EHEC (enterohemorrhagic E. coli)
which pathotype of E. Coli affects 4-12 week old piglets, and has an extremely high mortality
VTEC, verotoxin producing E. coli Mortality can be as high as 90%
what is the distinguishing feature of EHEC?
the production of Shiga Toxin
Salmonella is a _________ anaerobe, and is a ___________ _______cellular bacteria
Facultative anaerobe Facultative intracellular
what is the most important subspecies of salmonella among veterinary medicine
Salmonella enterica
what are the most common food borne salmonellosis in the US
S. typhimurium S. enteritidis
what is meant when stated that Salmonella is an obligate pathogen
it is not part of any animal’s normal microbiota.
what is the primary route of salmonella infection?
ingestion of contaminated feed or water
by what mechanism does salmonella survive phagocytosis
Salmonella is a facultative intracellular pathogen, so it can survive both inside and outside of a cell, it has an innate ability to resist lysosomal enzymes
once systemic Salmonella will spread through the lymphatic system, in what cells, and where are the most common places for it to travel to
Persists in macrophages and will be found in the spleen, liver, and lymph nodes
how would the diarrhea for salmonellosis be characterized
Malabsorption, exudation, and hypersecretion
define leutolysis, and what Dz is it a common consequence of fetal infection?
degradation of the corpus leuteum at the end of the luteal phase of estrous caused by fetal infection of salmonells
A calf is presented to you at 4 days old with severe dehydration, acute diarrhea, and Afebrile. What is the most likely pathogen
E. coli
in this Dz, the pathogen will adhere to the mucosal cells, but does not cause any damage. It does however cause severe secretory diarrhea through an exotoxin that blocks the absorption of Na+ and Cl-.
E. coli
this pathogen is know for producing bloody, foul, fibrin containing feces, depression, and fever. It typically affects neonates that are two weeks or older.
Salmonella
this pathogen is know for causing dehydration, mucoid feces, chronic diarrhea, and weight loss. This typically will not effect animals less then 6 days old because of the incubation period. It causes malabsorption, villus atrophy, and may have hypersecretory diarrhea.
Cryptospordia
What is the only obligate helminth transmitted pathogenic bacteria?
Salmon poisoning Disease (SPD)
caused by Neorickettsia Helminthoeca
What is the vector and the host(s) for neorickettsia helminthoeca?
Vector: trematode (fluke)
Hosts: Snails (inhabit fresh and brackish waters), Fish (salmonid fish?), Mammals
T or F
Neorickettsia Helminthoeca usually causes a systemic infection
True, it usually enters the blood and spread to other tissues such as lymph nodes, spleen, tonsils, thymus, liver, lungs, brain
Which pathogen is the only obligate helminth transmitted pathogenic bacteria?
Neorickettsia helminthoeca
Salmon Poisoning Disease
How does a dog get infected with N. Helminthoeca?
By ingesting the raw fish that is infected with the fluke, which then attaches to small intestinal mucosa of dog, and inoculates N. Helminthoeca
N. Helminthoeca infects what inside its dead end host?
It initially infects intestinal epithelium and then sets up shop in monocytes/macrophages in intestinal lymphoid tissue.
What damage is seen with neorickettsia Helmintheoca?
Cell Destruction: Lysis of mononuclear phagocytes, lymphadomegaly, splenomegaly, hepatitis, enterities (replication in peyer’s patches)
(also causes thrombocytopenia, lymphopenia)
What are clinical signs of neorickettsia helminthoeca?
Fever, anorexia, weight loss, weakness depression, vomiting, diarrhea, and DEATH
What type of diarrhea is seen with Neorickettsia Helminthoeca?
Yellowish and in small quantity, later in severe cases may become hemorrhagic
How do you diagnosis neorickettsia helminthoeca?
Geographical area (pacific northwest)
History of accesss to raw fish
Clinical signs (non specific: fever, anorexia, weight loss, yellow–Red bloody diarrhea)
Hematologic findings in serum (non specific: thrombocytopenia, lymphopenia, elevated ALP (liver), eosinophilia (parasite infection))
Fecal float: see eggs 5-7 days after infection
Cytology: Intracytoplasmic rickettsial bodies in monocyes/macrophages
How do you treat neorickettsia helminthoeca?
Give oral antibiotics: TETRACYLINES
Praziquantel: kills flukes
Supportive treatment
What is the name of the organism that causes Potomac Fever in horses?
Neorickettsia Risticii
What is the vector for neorickettsia risticii (potomac horse fever)?
N. Risticii infects a trematode (wormy) which then infects pleurocerid snalels and acuatic insects (caddis flies)
T or F
Neorickettsia Risticii (Potomac Horse Fever) can be spread between horses
FALSE:
Infectious, but not contagious :)
Where does Neorickettsia Risticii infect the host?
It infects monocytes and intestinal epithelial cells
Can become systemic
Cell entry: endocytosis into host vacuole
Cell Stages: MORULA-like inclusions seen in infected monocytes and intestinal epithelial cells
What are the clinical signs for neorickettsia Risticii?
Non specifc: Fever, anorexia, depression (inflammatory response)
Specifc: infection of intestinal epithelium (typhocolitis) leading to SEVERE: colic, ileus, diarrhea, laminitis
Abortion is also possible
T or F
Horses can become persistently infected by Neorickettsia Risticii AKA Potomac horse fever.
FALSE: Persistent infections are not recognized with this disease
What diagnostic tests can you use to detect neorickettsia risticii?
Serology: IFA test (paired serum is confimatory)
paired serum since no persistence and they must be collected 3-5 days apart
may be confounded by vaccination
PCR: specific and sensitive
blood or tissues
How do you treat neorickettsia risticii?
Tetracyclines
Supportive care: toxemia, dehydration
What are the Clincial syndromes associated with Salmonella?
- Hemorrhagic Enterocolitis: characterized by inflammation in the lamina propria and submucosa
- Diarrhea: mild–severe, fould smelling, watery, fibrin, mucous, blood and mucosal shreds (due to inflammation and exudate)
- Dehydration
- vomiting
- fever
intestinal damage can lead to chronic weight loss: infection can result in fusion of regenerating villi during healing, leading to malabsorption
- Septicemia
* this produces numberous clinical signs due to endotoxemia: DIC, infected mucous membranes, tachycardia, dry gangrene, pneumonia, meningitis, arthritis - Abortion
- Infection of fetus, causes relase of PGF2alpha causing luteolysis
*
T or F
Antibodies made in response to one serotype of salmonella will be cross protective to another serotype
FALSE: Antibodies are primarily directed towards o antigen side chain
What type of immune response is important in controlling salmonella infection?
Cell-mediated immunity
macrophage activation mediates immune response
How does salmonella cause carriers by persistent infection?
It escapes as an intracellular organism and is protected from ABs, antimicrobials, and complement
Why can antibiotic treatment casue reactivation of a disease and shedding?
Because they alter the normal microflora
What are the best ways to diagnosis salmonella?
Cytology: feces may contai neutrophils, erythrocytes
Isolation of salmonella is the gold standard
- fecal samples (repeated 4-5 times)
- Rectal biopsy and culture: ay provide better sensitivity
- blood culture: useful in case of septicemia
- dead animals: necropsy: intesting, spleen, liver, gall bladder, lymph node
What species has the greatest zoonotic potential for salmonella?
DOGS and HORSES
(infants and the elderly are especially prone to infection)
What is one conern with the use of antibiotics in the treatment of salmonella?
Antibiotic RESISTANCE
Camplyobacter jejuni when gram stained will reveal what?
that it is gram negative slender, curved, motile ROD
Which species are carriers of Campylobacter Jejuni?
Inapparent carriers: dogs, cats
apparent: Poultry (normal flora) WASH your raw chicken before cooking
Disease severity in campylobacter jejuni is dependent upon what?
Inoculum size
Immune status: lack of previous exposure and development of protective AB
Concurrent infection: salmonella, parvovirus, coronavirus, etc. play a synergistic role in casuing disease.
Enbironmetal, physiologic, and surgical stress exacerate the disease
What are two known ways that campylobacter jejuni causes disease?
Adhesions: probide attachement to and invasion of mucosal epithelial cells (jejunum, ileum, colon)
Prodces Cytotoxins: Cytolethal distending toxin
Destroys villi and induces inflammation
Invades epithelium
What are the clinical signs for campylobacter jejuni?
- most commmonly there are no clinical signs
- can produce hemorrhagic gastroenteritis
- most common in stressed animals less than 6 months old (wide spread diarrhea ranging from mild to watery to bloody)
- presents similar to salmonella
- can produce bacteremia
- may see fever
What is the best way to diagnosis campylobacter jejuni?
Fecal Culture is the gold standard.
Direct microscopic examination of feces usingwet mount (careful when interpreting results as other bacteria may look similar)
How do you treat campylobacter jejuni?
FLUID THERAPY!!
antibiotics : efficacy not known in dogs and cats
severe cases may warrant antibitotic therapy: may reduce human exposure through reduced shedding
Antibiotic resistance is common
