BACILLUS type of organism with very serious effect

This notes explains more on the Bacillus and their pathogenesis and how affect human immunity

1. 1 SPORE-FORMING GRAM-POSITIVE BACILLI Mzelifa Ikangala School of Medicine and Dentistry Department of Microbiology and Parasitology

2. 2 Spore forming bacilli Bacillus Clostridium

3. 3 Bacillus 34 species B anthracis is the pathogenic specie B cereus can cause food poisoning B subtilis cause opportunistic infections

4. 4 B. anthracis

5. 5 Physiology and structure Large Gram positive rods Arranged as single or paired bacilli in clinical specimens Seen as serpentine chains and clumps in culture Spores readily observed in 2 – 3 days old culture but not seen in clinical specimens Spores are located in the centre of the bacilli Spores survive in the environment for a very long time

6. 6 Antigenic structure Capsular antigen Polysaccharide cell wall somatic antigen Anthrax toxin which has got three heat labile antigen components Protective antigen Lethal factor Oedema factor Alone none of these factors are lethal

7. 7 Pathogenesis Zoonotic disease affecting mainly sheep, cattle and horses Man affected through injured skin or mucous membranes Inhalation & ingestion rare in humans Spores are phagocytosed by macrophages and transported from the site of infection to regional lymph nodes, where the spores germinate and vegetative bacteria multiply

8. Pathogenesis cont… Spread of vegetative form is via the lymphatic system to the blood stream Micro-organisms multiply freely in the blood and tissues Virulence of B anthracis due to capsular antigen which is antiphagocytic Toxin production is very important 8

9. 9 Clinical syndromes Cutaneous anthrax Development of painless papule at the site of inoculation Progresses to vesicles and then to necrotic ulcer Massive oedema develops and mortality is about 20%

10. 10 Clinical syndromes Inhalation anthrax Progress to pulmonary involvement leading to respiratory failures Mortality is high (95%) as the disease mimics viral infection

11. 11 Clinical syndromes Gastrointestinal anthrax Very rare in humans Mesenteric adenopathy, haemorrhage, and ascites production Mortality is high

12. 12 Diagnostic laboratory tests Specimens fluid or pus from local lesions, blood, sputum Stained smears Gram positive rods Culture on blood agar – non-haemolytic rapidly growing adherent grey colonies Serology precipitin or haemagglutinating antibodies

13. 13 Treatment Early treatment Penicillin, tetracycline, chloramphenicol, erythromycin

14. 14 Prevention Attenuated bacilli Spore suspension Protective antigens from culture filtrates

15. 15 Control Vaccination of animals and people in endemic areas Proper disposal of animals that die of anthrax

16. 16 B cereus

17. 17 Transmission Ingestion - food poisoning Contaminated soil

18. 18 Pathogenesis Present in virtually all environmental sites Food poisoning mediated by one of two toxins Heat – stable enterotoxin causes vomiting Heat – labile enterotoxin causing diarrhoea. It stimulates the adenyl cyclase – cyclic AMP system in intestinal epithelial cells. Panophthalmitis – destruction of the eye within 48 hours and mediated by the three toxins Necrotic toxins – an enterotoxin Cereolysin – a potent haemolysin Phospholipase C – a lecithinase

19. 19 Clinical syndromes Vomiting – contaminated rice In initial cooking the vegetative bacilli are killed but the heat resistant spores survive They germinate releasing the heat stable enterotoxin Incubation is 1 – 6 hours leading to nausea, vomiting, and abdominal cramps Disease duration is about 24 hours

20. 20 Clinical syndromes Diarrhoea – consumption of contaminated meat or vegetables Incubation period is longer Produces heat-labile toxin then diarrhoea, nausea and abdominal cramps Disease lasts for a day

21. 21 Treatment Symptomatic as the duration is short