1、Bacillus anthracis,Amanda Russell Anna Bossert,Taxonomy,Kingdom: Bacteria Phylum: Firmicutes Class: Bacilli Order: Bacillales Family: Bacillaceae Genus: Bacillus Species: anthracis,Basic Facts,Zoonotic Disease: usually carried by animals, can be transmitted to human hosts under natural conditions Ro
2、d-shaped monomorphic Endospore-forming, remain viable in soil and animal products for decades Gram-positive Aerobic respiration Exotoxin producing Grows best at 24-40C Incubation period: 1 to 15 days Three forms: inhaltion, gastrointestinal, cutaneous,Virulence Factors,Encoded on two plasmids One en
3、codes for the synthesis of a polyglutamyl capsule (inhibits phagocytosis by macrophages) Other bears genes encoding for the synthesis of exotoxins Exotoxins: three proteins Protective antigen Edema Factor: adenylate cyclase activity, increases cAMP, leads to cytoplasm loss after forming an edema Let
4、hal Factor: interferes with transcription factor in genome (NfkB) which regulates immunity genes. Once these are no longer transcribed, immune response of macrophages will fade.,General Mode of Infection,B. anthracis spores enter the body (lungs, skin lesion, gastrointestinal) and germinate, giving
5、rise to the vegetative formThe bacterium begins to produce capsules containing exotoxins, which will help evade the hosts immune systemThe PA portion will bind to receptors on the membrane of macrophages, when seven complexes are combined they form a ring. This ring will pierce through the membrane
6、and the macrophage will shuttle in the complex as an endosome,General Mode of Infection cont.,The PA molecules will form a pore that pierces the endosome membrane, releasing the EF and LF into the cytoplasm of the macrophage EF and LF essentially kill the macrophage, and release the contents of the
7、macrophage to the outside. The endosome enzymes that were released will degrade surrounding tissues, resulting in the common symptoms of anthrax.,Cutaneous Anthrax,B. anthracis comes into contact with a skin lesion, or cut. The spores germinate, producing bacteria, which produce exotoxins to evade t
8、he macrophages Infection is manifested in a painless ulcer with a necrotic (dead) center Transmission: coming in contact with infected animals or their products through a skin lesion,Symptoms of cutaneous anthrax,Boil-like skin lesion forming a painless ulcer Swelling of the lymph glands Fever Heada
9、che,Inhalation Anthrax,The spores are inhaled and lodge in the alveolar spaces Alveolar macrophages engulf the spores. Spores germinate within macrophages after failed phagocytosis Bacteria proceed to lymph nodes and spread into bloodstream, where they begin to release the exotoxins Transmission: in
10、haling the spores of B. anthracis,Symptoms of Inhalation Anthrax,Initial symptoms: sore throat, mild fever, muscle aches Severe difficulty breathing Septic shock Development of meningitis Respiratory failure resulting in death,Gastrointestinal Anthrax,Spores are consumed after eating undercooked mea
11、t Spores can evade stomach acid due to their capsule Once in the digestive tract, they begin to germinate and produce bacteria, which release exotoxins After the macrophages have been lysed, the endosome enzymes begin degrading intestinal walls, allowing the bacteria to spread directly into the bloo
12、dstream Transmission: Digesting undercooked meat containing spores,Symptoms of Gastrointestinal anthrax,Serious gastrointestinal difficulty Nausea Fever Abdominal pain Vomiting of blood Severe bloody diarrhea Acute inflammation of intestinal tract Loss of appetite,Diagnosis,A diagnosis can be made b
13、y taking a smear of a skin lesion (if cutaneous anthrax) and gram-staining the sample. Blood tests that show encapsulated, broad, gram-positive bacilli Cultures: large, flat, nonhemolytic colonies, non-motile, will test positive for catalse, positive for capsule production Confirmatory Diagnosis: Se
14、rological tests for toxins at reference laboratories,Transmission,Bacillus anthracis is transmitted mainly through the contact of infected animals or their products, and humans, resulting in cutaneous anthrax It cannot be spread from human to human. 2001: Anthrax was sent in the form of a powder in
15、letters, when the recipient of the letter opened them and inhaled the spores, they became infected. 5 out of 22 died. Biological Warfare Debate,Prevalence,In the past, anthrax was found all over the world. Now, this bacterium is found mainly in underdeveloped countries lacking the means of disease c
16、ontrol; such as the Middle East, Africa, Australia, southern and eastern Europe, South and Central America, Asia It is not common in the United States, although small outbreaks periodically occur in agricultural areas on animals. The last outbreak resulted in the death of 5 out of 22 people in 2001.
17、 1987: 20 out of 22 had died 2,000 20,000 human outbreaks annually,Susceptibility,All warm-blooded animals are susceptible to anthrax, especially herbivores Other domesticated animals such as horses and mules may also contract the disease.,Treatment,Cutaneous / gastrointestinal Antibiotic therapy fo
18、r 7 14 days Inhalation Antibiotic therapy for 30 days if used alone If vaccine is available, antibiotics can be discontinued after 3 doses of vaccine,Vaccine,Anthrax Vaccine Adsorbed (AVA) 6-dose series at 0,2,4 weeks and 6,12,18 months Annual booster injections to maintain immunity Who receives vac
19、cine? Animals, mainly cattle People with high occupational risk Military, people close to an outbreak,Prevention,Decontamination Wash down with anti-microbe effective soap Boil articles that came in contact with infected hosts Chlorine Burning articles Early detection USPS installed BioDetection Sys
20、tem Antibiotics Penicillin Doxycycline,Current Research,New research has found that extracellular metalloproteases may play a role in the survival of the bacterium Aid in degradation of the LL-37 peptide. Other bacillus species showed no resistance to this peptide,Current Research cont.,Anti-protect
21、ive antigen antibody has been shown to suppress the vegetative form of B. anthracis before it sporulates.,Current Research cont.,Research has also shown a new technique in identifying anthrax spores before a new outbreak occurs. Microwave-Accelerated Metal-Enhanced Fluorescence (MAMEF) (Metal-enhanc
22、ed flulow power microwave heating) is used to accelerate DNA hybridization The DNA of the B. anthracis spores was detected almost immediately.,References,http:/www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17955147&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_
23、ResultsPanel.Pubmed_RVDocSum Microbiology Lecture Textbook http:/www.cdc.gov/ http:/www.nlm.nih.gov/medlineplus/anthrax.html http:/pathport.vbi.vt.edu/pathinfo/pathogens/Bacillus-anthracis.html http:/www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=191218&lvl=1 http:/www.ncbi.nlm.nih.gov/sites/entrez http:/www.bt.cdc.gov/agent/anthrax/lab-testing/#references,
