Cardiovascular & Lymphatic Bacterial
Infections
Microbiology-2420
Instructor: Mark Pulse
Cardiovascular & Lymphatic Bacterial
Infections
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Overview of material covered:
– Bacterial Cardiovascular Infectious Diseases
• Acute & subacute bacterial endocarditis
• Gram-negative septicemia
– Bacterial Lymphatic Infectious Diseases
• Tularemia
• Brucellosis
• Plague
Cardiovascular & Lymphatic Bacterial
Infections
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Endocarditis is an infectious disease commonly associated with
structures of the heart
These infections are usually associated with the valves or the
epithelial lining (endocardium) of the chambers
Depending on the causative agent, endocarditis infections can be
classified as acute or subacute
– Acute endocarditis is predominantly caused by
Staphylococcus aureus or Streptococcus pneumoniae
– The onset of acute endocarditis is rapid & the causative
agents can infect normal or abnormal heart valves
– After infection of a heart valve, the agent produces toxins that
damage the valve & generate abscesses in cardiac muscle
– Heart failure is eminent if left untreated
Cardiovascular & Lymphatic Bacterial
Infections
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Endocarditis (cont’d)
– Subacute endocarditis is normally caused by less virulent bacteria
that include Staphylococcus epidermidis & oral streptococci
(Streptococcus mutans)
– Infections are associated with damaged or deformed heart valves
(rheumatic fever), & the onset of the disease usually occurs within
weeks of the initial infection
– These organisms gain CV access through the skin or oral cavity
– Micro-clots associate with a damaged heart valve, & they (clots) trap
circulating organisms
– Trapped organisms multiply at the site & form biofilms
– Clots are periodically shed into circulation (septic emboli), & heart
structures become progressively damaged due to the infection
Cardiovascular & Lymphatic Bacterial
Infections
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Gram-negative septicemia is an infectious disease associated with the
circulatory system (blood)
– The causative agents include enterobacteria (E. coli), aerobes (P.
aeruginosa), & anaerobes (Bacteroides species)
– Infectious agents gain access into the blood due to trauma, localized
infections, and/or a dampened immune response
– The endotoxin (outer cell wall/membrane) associated with the
infecting organism generates a hyper-response by circulating
macrophages (produce stimulatory hormones)
– Other leukocytes are activated & release damaging enzymes
– Endotoxin induces spontaneous clot formation in the CV system
– All of this (hormones, damaging enzymes, clots) produces CV
hypotension (low BP) & decreased blood flow to vital organs
– Endotoxic shock results from decreased blood flow & often is fatal
within infected individuals
Cardiovascular & Lymphatic
Bacterial Infections
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Tularemia is an infectious disease associated with lymphatic system
structures (nodes)
– Francisella tularensis (bacterium) has been identified as the causative
agent, & this organism is normally associated with wild animals
(rabbits)
– F. tularensis enters the host through a break in the skin or by
inhalation, & lymph nodes become infected
– This bacterium is capable of surviving & multiplying within inactive
macrophages, which can carry the organism to other organs (lungs)
Brucellosis is an infectious disease that is systemically disseminated
through the lymphatic & CV systems
– Brucella melitensis (bacterium) has been identified as the causative
agent, & this organism is commonly associated with domestic animals
(dogs)
– This organism enters the host through breaks in the skin or mucosal
membranes
– B. melitensis infects lymph nodes & other organs (heart) after
dissemination
Cardiovascular & Lymphatic
Bacterial Infections
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The plague (‘black death’) is an infectious disease that is associated with
the lymphatic (bubonic) & respiratory (pneumonic) systems
In 14th Century Europe, a plague epidemic resulted in over 25 million
deaths (40 million population)
– Yersinia pestis (bacterium) has been identified as the causative agent,
& it can spread through flea bites or by aerosols from individuals with
lung infections
– Once in the system, the bacterium enters into the lymph nodes & are
taken up (phagocytosis) by macrophages
– As Y. pestis multiplies inside of a macrophage, it expresses an
antiphagocytic capsule
– The cell lyses open, releasing encapsulated bacteria throughout the
lymphatic system
– Lymph nodes become tender & eventually visually necrotic
– Infection is spread from the necrotic lymph nodes into the blood,
resulting in endotoxic shock & intravascular clotting
– Y. pestis spreads to the lungs, resulting in pneumonic plague & the
transmission of highly virulent bacteria to other individuals
– Pneumonic form 100% fatal if left untreated
Bubonic Plague