Cardiovascular & Lymphatic Bacterial Infections Microbiology-2420 Instructor: Mark Pulse Cardiovascular & Lymphatic Bacterial Infections • 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 • • • 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 • 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 • 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 • • 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 • • 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
