Bacterial CV Infections Flashcards
What are the body’s immune defenses that help prevent CV infections?
Innate Defenses
1. Phagocytic cells (macrophages, PMNs), especially in the spleen and liver -> remove potential pathogens from vascular system
Adaptive Defenses
1. Macrophages (APCs)
2. Neutrophils and Macrophages (phagocytosis)
3. Lymphoid Tissue (Bcells = Ab prduction, Tcells = Thelper and cytotoxicity)
Transient Bacteremia
Bacteria that are normal flora of mucous membranes and enter the sterile circulatory and lymphatic systems sometimes during procedures like dentals or minor GI sx. In healthy animal, these bacteria are cleared rapidly (within minutes) and thus sepsis does not occur.
If body is unable to clear, sepsis/septicemia can occur and lead to severe disease.
What are the predisposing or risk factors (stressors) that allow for transient bacteremia to occur regularly and cause CV infection?
1. Immunodeficiencies
- neonates (failure of passive transfer or during waning maternal immunity)
- adults (iatrogenic: chemotherapy, radiation therapy; loss of key organs like splenectomy, organ which plays huge role in filtering the blood; immunosuppressive doses of corticosteroids)
2. Iatrogenic Manipulations
- dental extractions, endoscopic procedures of GIT, ucaths, IVCs, oral, abd, other invasive-type surgeries
- nosocomial infections of ICU pts
3. Nidus of Infection
- abscesses, migrating FBs, penetrating wounds, burns, colitis, gingivitis, stomatitis, pyoderma, UTIs, arthritis
4. Primary Infections (mostly viral)
- viruses that infect the immune system or compromise another body system that increases the chances of pathogenic microorganisms infiltrating
Transiet bacterermia = when microbes that are normal inhabitants of mucous membranes enter bloodstream/circulatory system, usually as a result of one of the above events
How do bacteria enter the CV system?
- direct inoculation (insect bites, contaminated needles, blood transfusions)
- spread from initial site of infection (via vascular system or lymphatics draining that site)
Infectious Valvular Endocarditis
Conditions: a pre-existing injury or functional abnormality of a heart valve with established platelet and fibrin deposition.
Pathogenesis: Bacteremia occurs (transient or infectious) -> the bacteria are able to adhere to the valve via the platelet/fibrin deposition
Sequelae: = emboli, multi-organ infarction, sudden death
Myocarditis
- cause
- example bacteria in cattle
- inflammation of cardiac muscle due to systemic infection with foci of infection within the heart
- Histophilus somni: in cattle, starts in the lungs but later damages myocytes (as well as the brain)
Traumatic Reticulopericarditis (“Hardware Disease”)
- secondary to trauma, sometimes secondary to systemic infection involving other serosal surfaces (e.g., Glasser’s Dz.)
- traumatic reticulopericarditis in cattle: ingestion of nail or wire -> migrates through reticulum and diaphragm into pericardial sac -> heart cannot contract properly -> heart failure, exercise intolerance, tachycardia due to decreased CO
- bacteria from ingested material enter and establish infection in pericardial sac
- polymicrobial infections w/. Trueperella pyogenes and Fusobacterium necrophorum frequently involved
What are 2 ways microbes can cause blood vessel infections
- direct vascular endothelial injury
- immune-complex deposition and inflammation (type III hypersensitivity)
Type III hypersensitivity is a type of immune response in which antigen-antibody complexes accumulate in the tissues and cause inflammation and tissue damage
Omphalitis
inflammation of the umbilicus in neonates involving umbilical aa. and/or vv.
- farm animals and horses
-enteric, inhabitants of mucosal surfaces, environmental contamininants
Omphalophlebitis
inflammation of the umbilical vein and infection can extend into fetal circulation to involve the liver
Navel ill
when septicemia develops from umbilical infections.
Sepsis vs Septicemia
Sepsis = when the immune response to septicemia becomes dysregulated and causes life-threatening organ dysfunction
Septicemia = presence of bacteria and toxins in the blood
Septic Shock vs Sepsis
Sepsis = I.S. responds in overwhelming/improper manner to infection
Septic Shock = subset of sepsis where the underlying circulatory, cellular and metabolic abnormalities are so extreme that they greatly increase the chances of mortaility
What bacteria are the typical causative agent of septicemia?
Enteobacterales: gram negative rod-shaped, facultative anaerobic, non spore-forming bacteria
- release endotoxins that induce inflammation/overdrive of immune system
- Escherichia coli, Salmonella enterica, Yersinia pestis
How is suspected septicemia sampled?
- goal is to collect 1-2 samples from the blood BEFORE starting abx
- collect 3rd sample at trough antimicrobial concentrations / when fever spikes
- must be sterile sample!!
- blood samples are placed into special blood culture media at time of sampling (EDTA KILLS bacteria! never use EDTA tubes)
3 forms of anthrax disease observed in humans
What is Anaplasma marginale and its pathogenesis?
A tick-borne, reportable disease that affects CATTLE.
Vector = multiple tick species, including Dermacentor
tick bite -> bacteria enters bloodstream -> infects erythrocytes -> undergo phagocytosis by Mø in spleen (extravascular hemolysis) -> accel. RBC destruction -> hemolytic anemia
Target cell = erythrocytes
What does epicellular mean with feline hemotropic mycoplasmosis (Mycoplasma haemofelis)?
The bacteria attaches to/grows on the surface of RBCs (erythrocytes)
How does Bartonellosis henselae (Cat Scratch Dz) affect dogs and cats?
- chronic bacteremia in ≤ 2y/o cats; typically no clinical signs but major reservoir
- dogs: infectious endocarditis
