CARDIOVASCULAR, LYMPHATIC AND SYSTEMIC DISEASES

CHAPTER 23

Copyright © 2012 John Wiley & Sons, Inc. All rights reserved.

Enteropathogenic E.coli produces a toxin similar to that of Vibriio Cholera

A. TrueB. False

True

False

50%50%

Researchers have found that around the world, 160 people die each day from canine rabies. An estimated 59,000 people are thought to die every year as a result of this preventable disease“ This ground-breaking study is an essential step towards improved control and eventual elimination of rabies," reports Prof. Louis Nel, Executive Director of the Global Alliance for Rabies Control (GARC). "An understanding of the actual burden helps us determine and advocate for the resources needed to tackle this fatal disease." . Rabies is a difficult disease to track and underreporting is believed to be commonplace. As rabies is close to 100% fatal, a large number of rabies victims never report to health facilities and are never diagnosed. In regions where regions where malaria is prevalent, misdiagnosis is also frequent is prevalent, misdiagnosis is also frequent. Rabies is a fatal viral disease that is usually acquired when humans are bitten by infected animals, most typically domestic dogs. Through the prompt administration of a fast-acting shot to bite victims, the disease is entirely preventable, yet in populations with limited access to health care, the disease is prevalent. The researchers found the greatest risk of canine rabies was in the world's poorest countries. Sub-Saharan Africa is home to the highest death rates while India reports the highest number of human fatalities - approximately 20,800 deaths per year, over 35% of the global rabies burden. Mass vaccination of dogs comprised a very small proportion of the economic burden of rabies - less than 1.5%. The researchers report that outside of North America and Europe, a large investment in dog vaccination has only been sustained in the Americas, leading to a small rabies burden in this region.

Maple syrup helps antibiotics defeat bacteria Inappropriate and overuse of antibiotics has led to the emergence of drug-resistant strains and superbugs - a major public health problem that is in urgent need of solutions. Now, a team of researchers at McGill University in Montreal, Canada, suggests one solution may lie in the sap of trees that are abundant in North America. Writing in the journal Applied and Environmental Microbiology, Nathalie Tufenkji, a chemical engineering professor, and colleagues describe how they found concentrated maple syrup extract makes disease-causing bacteria more susceptible to antibiotics. Maple syrup contains phenolic compounds, which are of considerable interest due to their antiseptic and antioxidant properties. Phenolic compounds play an important role in the growth and development of plants by helping to defend against pathogens. Phenolic-rich extract made infection-causing bacteria susceptible to antibiotics They bought the maple syrup at local markets in Montreal and kept it in the freezer until the start of each experiment where they removed a sample and put it through a series of steps to produce the phenolic-rich extract.They then tested the extract on a number of infection-causing bacteria such as Escherichia coli and Proteus mirabilis - a common cause of urinary tract infection. The maple syrup extract and antibiotic combination was particularly effective at destroying biofilms - resistant communities that inhabit surfaces and are particularly hard to shift with antibiotics. Dental plaque is an example of a biofilm. One effect that the extract has on bacteria is to make their cell membranes more porous. This makes it easier for the antibiotics to enter the microbial cells.The maple syrup extract also shuts down the "efflux pumps" that the bacteria use to push any antibiotic that makes it through the membrane out of the cell.And a third way that the extract weakens the bacteria is by reducing expression of genes linked to antibiotic resistance and virulence.

Normal microflora of the cardiovascular system- The cardiovascular system does not have any normal resident

microflora. Bacteremia- bacteria in the blood, septicemia-multiplying

bacteria and their products in the blood.

Bacterial septicemias and related diseases-Before antibiotics, septicemia was often fatal; even with antibiotics they are still not easily treated.

Septicemia (often referred to as sepsis): the proliferation of bacteria and the release of bacterial products in the blood. Symptoms include: 1. fever 2. hypotension (a decrease in blood pressure) 3. Shock (which is caused by the decreased blood pressure)

The bacteria most often associated with septicemia are gram negative rods, e.g., Escherichia coli, Pseudomonas aeruginosa and Bacteriodies sp.

It is the endotoxin of these organisms that is released when the bacterium is lysed that causes the problems. The endotoxin damages the blood vessels causing vascular leakage and resulting in low blood pressure and shock.

Rheumatic fever (autoimmune disease). Caused by Streptococcus pyogenes and leads to a rheumatic condition and often to destruction of the heart valves. This disease is considered as an autoimmune disease and most often evolves from a "strept" throat.

Bacterial Endocarditis. Usually caused by alpha‑hemolytic streptococci and is characterized by fever, anemia, general weakness, and heart murmur.

Infection of the heart often occurs from a primary infection (e.g., gums) elsewhere in the body. An acute type of bacterial endocarditis is caused by Staphylococcus aureus or Streptococcus pneumoniae. In this disease the infection spreads from a primary site to the heart valves which often leads to their destruction and is frequently fatal.

Systemic Diseases

Bacterial systemic diseases

Anthrax

Plague

Brucellosis (Undulant Fever).

Lyme Disease

Bacillus anthracis

Yersinia pestis

Brucella abortus, Brucella suis and Brucella melitensis

Borrelia burgdorferi.

Anthrax. Causes by Bacillus anthracis which is a aerobic gram positive spore forming rod.

Of human anthrax cases, 90 percent are cutaneous, 5 percent are respiratory (wool-sorters disease) and 5 percent are intestinal. Death is caused by production of a lethal toxin.

A vaccine is available and should be given to workers with occupational exposure to anthrax. Animal immunization is an important means of prevention.

Bacterial Systemic – Anthrax

• Bacillus anthracis

• Cutaneous

• Respiratory

• Intestinal

• Virulence factors

© 2012 John Wiley & Sons, Inc. All rights reserved.

Plague. The disease is caused by a gram‑negative rods called Yersinia pestis.

Normally a disease of rats, plague is transmitted from rat to rat by the rat flea and when rats are not available to humans.

Mortality rate for untreated plague is 50‑75%. If the disease progresses to the lungs it is called pneumonic plague with a mortality rate in untreated cases of almost 100%(even with antibiotics and modern treatment).

The term black death stems from the fact that the infected tissues hemorrhage and turn the skin black.

Brucellosis (Undulant Fever). Caused by Brucella abortus, Brucella suis and Brucella melitensis. Small gram negative rods which often grow inside macrophages.

The disease is chronic and can last for years. When death occurs it is usually from endocarditis.

Pasteurization of dairy products and immunization of animal herds are the best measures to prevent the disease. Problems with Bison herds- Bison carry Brucella but are not overtly harmed by it.

Lyme Disease. Borrelia burgdorferi.Disease that is showing a striking increase and is spreading throughout the USA; has become an important infectious

bacterial disease because of the potential complications and the number of cases. In fact it is likely the most common tick‑borne

disease in this country; may be spread by ticks attached to migratory birds.

Symptomology Rash at bite site. It is a red area that clears in

the center as it expands to a final diameter of about 15 cm. Seen in about 75% of the cases.

Fig. 23.13 Lyme disease

Typical bull’s-eye rash of Lyme disease

Rickettsial and related systemic diseases- Rickettsias are small gram-negative coccobacilli and are microscopic obligate intracellular parasites.

The organisms invade and damage the cells of blood vessel linings (endothelial cells) and cause the linings to leak. This leakage causes skin lesions and especially petechiae, pinpoint-size hemorrhages most common in skin folds. It also causes necrosis in organs such as brain and heart. Although each disease produces a particlar kind of skin rash, all rickettsial diseases cause fever, headache, extreme weakness, and liver and spleen enlargement.

Infectious mononucleosis- Epstein‑Barr (EB) virus. The disease which affects primarily the lymph nodes is characterized by enlarged and tender nodes, enlarged spleen, fever, sore throat, headache, nausea and general weakness.

The virus enters via oral secretions, multiplies in lymphatic tissue, and infects white blood cells. The virus first infects epithelial cells and eventually B cells. It establishes a persistent infection in which viruses are shed for months to years.

Infectious mononucleosis causes a proliferation of atypical lymphocytes which in the early stages is may be confused with leukemia. Diagnosis is usually made

with a serological test for heterophil antibody. These antibodies are not specific for EB virus but cause the nonspecific agglutination of sheep red blood cells and develop to a very high titer in response to the disease.

The proliferation of EBV-infected lymphocytes is limited by cytotoxic T cells and cells that make humoral antibodies and complement. If these defenses fail to limit lymphocyte proliferation, uncontrolled B cell proliferation can lead to B cell cancer or Burkitt’s Lymphoma.

Most patients have a sore throat during the first week. The spleen is enlarged, and cells in lymphoid tissues in the oropharynx multiply. The tonsils are coated with a gray exudate, and the soft palate may be covered with petechiae.