Bacillus
Gram positive, aerobic/ facultative anaerobes, spore forming rod.
They are present in soil, dust, air, water and frequently isolated as contaminated in bacteriological culture media.
The causative Agent of Anthrax is the most important pathogen of group is bacillus Anthracis.
Bacillus Anthracis
Morphology
Gram positive, non acid fast, non motile, non capsule, blunt ended bacilli in single or in pairs chain.
Bacilli have centrally located oval endospores.
Rectangular, bamboo- stick appearance.
Spores can survive in soil for very long period of time.
Size; 1-1.5 X 3-10 micrometre in size.
Characteristics
Non motile, non capsulated, long chain Medusa head colony.
It lives in soil at mesophilic temperature.
Bacilli are strictly aerobes that grow at optimum temperature 37degree celcius, PH; 7.5-8 on enrich media as;
Nutrient agar
Blood agar; when specimen cultured after 24hrs.
Bacilli produce non hemolytic.
ASColi test (serological test); test positive if person infected.
Sources and mode of Infection
Major sources;
Handling infected animal
Contaminated animal products
Inhaling Anthrax spores from contaminated bone meal fertilizer.
Contaminated hides
Transmitted by;
Infection
Ingestion of spores
Through infected animal's skin
Pathogenesis
Anthrax is primarily a disease of animals like cattle and sheep.
Infected animals discharge large number of bacilli from mouth, nose and rectum.
Animals are Infected by ingestion of spores present in soil.
Anthrax presents in three forms;
1. Cutaneous anthrax
2. Pulmonary anthrax
3. Intestinal Anthrax
1. Cutaneous anthrax
Common in farmers, who handle animals.
Shaving brushes with infected animal hairs.
Cause edema, lesion filled with serum.
Occurs septicemia cause meningitis.
2. Pulmonary anthrax
Common in workers in wool factories.
Hemorrhagic meningitis may occur.
3. Intestinal Anthrax
Who eat improperly cooked meat.
Carcasses of infected or dying animal of Anthrax.
Affect throat, stomach, intestine.
Laboratory diagnosis
Specimen collection
Lesion, sputum, blood
Microscopic examination and morphology
Gram positive
Culture characteristics and staining
Nutrients agar; colonies show Medusa head appearance.
Direct immunofluorescence
Reliable in identification of bacillus
ASColi test
Used in making rapid diagnosis, if test is positive.
Prevention
Animal known to have died of bacillus Anthracis must buried in such a way that soil is not contaminated.
Treatment
Tetracycline, Ciprofloxacin and Erythromycin are effective in cutaneous form of anthrax.
In case of pulmonary anthrax, multidrug therapy is recommended.
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