Lab Report: General Microbiology And Immunology

General Microbiology and Immunology

PM204

Rickettsia

Name: Khaled Sayed Khalil

ID: 141199

Lab Group: B

Characteristics:

1- They are naturally obligate intracellular parasites

2- They have the common feature of being spread by arthropod vectors (lice, fleas, mites and ticks)

3- They are rod-shaped or coccoid in nature

4- They range in size from 0.3 to 0.5 micrometer

5- They are mostly gram negative

6- They have bacterial cell wall

7- They have no flagella

8- They can reproduce only within animal cells via binary fission

9- They occur in single form, in pairs or as strands

10- Mostly found in the cytoplasm of the host cell

Methods of Culturing:

1- Tissue Culture:

The best and most consistent results were obtained with filtered

The same innoculum was used as in the tissue culture series. The innoculated eggs were incubated at 35 degree and transfers made every 5 to 9 days. The tissue material is then drained and pooled, then titration tests are taken.

Examples of rickettsial diseases & methods of diagnosis:

1) Rickettsia of the Spotted Fever and Typhus groups:

The rickettsial diseases are arranged in many categories from which are the spotted fever and typhus fever groups.

Clinical symptoms:

a) Rocky Mountain Spotted Fever:

It is considered to be among the most severe of human infectious diseases, with a mortality rate of 20 to 25% unless it is treated with a suitable antibiotic. Naturally, the rickettsia is maintained by the transmission of infected female ticks to infected ova which afterwards hatch into infected larval offspring. When the ticks feed on small mammals with rickettsia in their blood, a low rate of acquisition of rickettsia occurs by uninfected ticks. This effect leads to the destruction of lines of infected

The clinical signs and manifestations (e.g., fever, headache, nausea, and muscle aches) resemble many other diseases during the early stages when antibiotic treatment has more effect. A history of exposure to the appropriate vector tick, louse, flea, or mite is helpful but we cannot base our work upon it. Observation of a rash, which usually appears on or after day 3 of illness, should suggest the possibility of a rickettsial infection but, of course, may occur in many other diseases also. Knowledge of the geographic epidemiology of rickettsioses is useful, but is inconclusive for the individual patient. Except for epidemic louse-borne typhus, rickettsial diseases strike mostly as isolated single cases in any particular neighborhood. As a result, clinico-epidemiologic diagnosis is ultimately a matter of suspicion, empirical treatment, and later laboratory confirmation of the specific