What are Bacterial Diseases of the Cardiovascular and Lymphatic Systems

• The infectious diseases of the cardiovascular system infect the blood, blood vessels, and heart.
• In many cases, the infections remain in these areas, but in others, the infections are spread to secondary organs.
• The diseases of the lymphatic system affect the lymph, lymph vessels, lymph nodes, and lymphoid organs, such as the spleen, tonsils, and thymus.

1.1. Septicemia:
• Septicemia is a general expression for microbial infection of the blood and blood vessels.
• This condition also known as blood poisoning is characterized by multiplication of bacteria in the blood.
• The condition occurs if the defenses of the blood and lymphatic systems fail and the microorganisms  proliferate in the blood without control.
• Clinically, septicemia is characterized by fever and a decrease in blood pressure.

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The decrease in blood pressure can result in ischemia (decreased blood supply) and shock.
• Another symptom is the appearance of lymphangitis, inflamed lymph vessels shown as red streaks under    the skin, running along the arm or leg from the infection’s site.
• The organisms most frequently associated with septicemia are gram-negative rods, although a few gram–positive bacteria and fungi are also implicated. 

•Among the causative gram-negative rods are Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Enterobacter aerogenes, Serratia marcescens and Bacteroides species.
•These bacteria enter the blood from a focus of infection in the body.
•The cell walls of many gram-negative bacteria contain endotoxins that are released upon the lysis of the cell.

•It is the endotoxin that actually causes the symptoms.
• The endotoxin damages blood vessels causing the low blood pressure and subsequent shock.
•In some cases, antibiotics aggravate the condition by causing the lysis of large numbers of bacteria, which in turn release damaging endotoxins.
•Many of these gram-negative rods are of nosocomial origin, and were introduced into the bloodstream by medical procedures that bypass the normal barriers between the environment and the blood.

2. Puerperal Sepsis.

Puerperal sepsis or puerperal fever or childbirth fever is a nosocomial infection that frequently leads to septicemia. •This begins as an infection of the uterus as a result of childbirth or abortion. •The most frequent cause of puerperal sepsis is the Gram-positive streptococcus named Streptococcus pyogenes. •This beta-hemolytic streptococcus causes severe fever, malaise, and dropping blood pressure.

Puerperal sepsis progresses from an infection of the uterus to an infection of the abdominal cavity (peritonitis), and in many cases to septicemia.
•Shock may accompany the infection, and antibiotic therapy with penicillins and erythromycin are effective against S. pyogenes.


3. Bacterial Endocarditis.

• The wall of the heart consists of three layers.
• The outer layer, called pericardium, which is a sac that encloses the heart

•The middle layer, called myocardium, which is the thickest layer and consists of cardiac muscle tissue.
• The inner layer, called endocardium, which is a lining of epithelium that lines the heart muscle and also covers the heart valves.
• An inflammation of the endocardium is called endocarditis.
• It also involves infection of the heart valves.
• This is usually an immune system problem caused by antigen-antibody reactions taking place at the heart valves.
• Heart valve replacement is sometimes required.

•Known types of bacterial endocarditis are:-
(i)Sub-acute bacterial endocarditis &
(ii)Acute bacterial endocarditis
(i) Sub-acute bacterial endocarditis is due to Streptococcus pyogenes and is accompanied by fever, anaemia, weakness, and heart murmur.
• The condition probably arises from a focus of infection elsewhere in the body, such as the teeth or tonsils.
• Microorganisms released by tooth extractions or tonsillectomies enter the blood and find their way to the heart.

(ii) Acute bacterial endocarditis is generally due to infection by Staphylococcus aureus or Streptococcus pneumoniae and is accompanied by rapid destruction of the heart valves.
• These organisms find their way from the initial site of infection to normal or abnormal heart valves; the rapid destruction of the heart valves is frequently fatal in days or weeks.
• Strains of Staphylococcus that produce penicillinase are sensitive to methicillin or oxacillin.
• S.pneumoniae responds well to penicillin.

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Streptococcus can also cause pericarditis, inflammation of the sac around the heart (pericardium).
• Laboratory diagnosis is based on isolation and identification of the bacteria from blood.
• Penicillin is the most commonly used drug in treatment.
• It is well to use it prophylactically in susceptible persons, such as those suffering from rheumatic fever or undergoing tooth extractions or tonsillectomies.
• Erythromycin is also effective in many cases.

4. Rheumatic Fever.
•Rheumatic fever is an immune reaction taking place in the heart tissues and is usually stimulated by antigens derived from Streptococcus pyogenes.
•Inflammation of the heart tissues which damages the valves is often accompanied by inflammation and arthritis of the joints, a condition called rheumatoid arthritis. other symptoms include fever and malaise.
• The disease is usually precipitated by a streptococcal sore throat.
•Although rheumatic fever does no permanent damage to the joints, there can be permanent heart damage. 5. Tularemia.
•Tularemia is due to a Gram-negative rod, facultatively anaerobic, pleomorphic bacterium called Francisella tularensis.
•The bacteria enter the body by contact, inhalation, ingestion of contaminated rabbit meat, and the bite of ticks and other arthropods.
•Patients experience a blood disorder accompanied by fever, malaise, and numerous nonspecific symptoms.
•Antibiotics such as gentamicin are used in therapy

6. Plague. 

•Plague is caused by the Gram-negative rod Yersinia pestis.
•This organism is similar to the agent of tularemia and is transmitted by its rodent reservoir, the rat flea.
•The organism enters the lymphatic system and causes swelling of the lymph nodes called buboes.
•This stage is called bubonic plague.
•When the bacteria enter the blood, the condition is referred to as septicemic plague, and when the bacteria enter the lungs, the disease is called pneumonic plague.

•Transmission by airborne droplets is possible at this time.
•Aggressive antibiotic therapy is necessary to prevent death.

 

7. Brucellosis. 

•Brucellosis is also known as undulant fever because it is characterized by alternating periods of high fever and relief.
•Like the bacterium that causes tularemia, the bacteria causing brucellosis favour intracellular growth, move through the lymphatic system, and travel to organs via the bloodstream.
•The bacterial agents causing brucellosis belong to the genus Brucella, Gram-negative, aerobic rods.