Microbiology

Microbiology Study Guide

5.5 Blood Diseases Bacterial Diseases Plague The gram-negative bacterium rod Yersinia pestis causes plague. The disease is transmitted through rat fleas. The main symptom of the disease is inflammation of the lymph nodes, known as buboes. This is the initial stage of the disease wherein the organism enters and interferes with the lymphatic system of the human body, known as the bubonic stage. Thereafter, the organism travels to the bloodstream and this phase is known as septicemic plague. The next stage is the pneumonic plague and is when the bacteria enter the lungs. At the last stage, it is possible that airborne droplets are transmitted. The disease is capable of causing death and aggressive antibiotic treatment is required in order to save the life of the infected individual. Tularemia The gram-negative bacteria from the species Francisella tularensis are responsible for causing the tularemia. The disease is transmitted by physical contact, respiratory inhalation, consumption of infected rabbit meat, and bites from ticks and other arthropods. Major symptoms of the disease include fever, disorders in the blood, and malaise. Treatment is possible through antibiotic drug therapy, including the use of gentamicin. Rocky Mountain Spotted Fever The submicroscopic bacteria Rickettsia rickettsii is responsible for causing Rocky Mountain spotted fever. The disease is transmitted by the ticks of Dermacentor. Symptoms include a skin rash on the appendages, followed by the trunk area. High fever and headache also occur. Treatment of Rocky Mountain spotted fever is possible with an antibiotic course of tetracycline. Typhus Fever This disease is caused by the bacterium Rickettsia prowazekii . The disease is transmitted by the locus belonging to the genus Pediculus. Symptoms of the disease include the formation of a skin rash on the trunk, followed by the appendages, and a high fever. The mortality rate of typhus fever is very high. Treatment of this disease is possible by taking a proper antibiotic course of tetracycline, which prevents the disease from becoming epidemic by eliminating the lice. When the disease spreads in rodents, it is known as endemic typhus or murine typhus. This is a milder form of epidemic typhus with a lower death rate. It is caused by the species of Rickettsia typhi and is transmitted by the rat flea. Other Rickettsial Diseases It is possible that various rickettsial diseases infect humans. For instance, rickettsialpox is one of the rickettsial diseases that is caused by the species Rickettsia akari . Rickettsialpox is transmitted by mites. Major symptoms include rashes on the skin, similar to chickenpox. Another rickettsial disease affecting human beings is tsutsugamushi, which is caused by mites. The disease mostly affects individuals residing in Pacific regions. Major symptoms include rashes on the skin and fever. Trench fever is another rickettsial disease that is caused by the bacterium Rochalimaea Quintana . This

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