Lecture 7 Flashcards
What is the reservoir of bacillus?
environment
What are the characteristics of bacillus?
gram+, rods can form chains, expression of many toxins = cause different diseases, aerobic (loves O2)
What colony morphology does bacillus form? What is important about this?
white fuzzy colonies = unique way to identify bacillus species on BAP plates
Where are the spores located in a bacillus that formed spore?
one side of the cell
What does “anthrax” mean and what does it refer to?
means “charcoal” referring to the black necrotic wound it causes
What kind of pathogen is B. anthracis?
human pathogen
What disease does B. anthracis cause?
anthrax
What disease does B. cereus cause?
food poisoning (mainly)
What kind of pathogen is B. subtilis?
human opportunistic pathogen, part of human microbiota on some individuals
What diseases does B. subtilis cause?
eye infection
What kind of pathogen is B. thuringiensis?
pathogen for insects
What does B. thuringiensis do to insects and what is beneficial about this to us?
produces exotoxins that target specific insect; this bacteria can be used as a bio-pesticide
What are the 3 forms of anthrax diseases due to B. anthracis?
cutaneous, inhalation, and GI
What is the most dangerous form of anthrax?
cutaneous
What is the most lethal form of anthrax?
inhalation
What is the cutaneous form of anthrax?
on the skin; happens when there is an opening in the skin (wound) and it gets infected by the pathogen
What is the inhalation form of anthrax?
(aka systemic anthrax) breathe in spores –> infect different parts of body
What is cutaneous anthrax characterized by?
pustule surrounded by edema
How can cutaneous anthrax be treated? Is this easily treatable?
easily treatable with antibiotics
How is one explanation as to why systemic anthrax is most lethal form of anthrax?
macrophage cannot digest endospore and when B. anthracis become vegetative = it will divide and multiply and spread to other parts of body
What is GI anthrax form of anthrax?
ingesting food (especially meat) with the B. anthracis spore
What is the infectious agent in anthrax that leads to the disease?
the endospore
How often does GI anthrax occur in developed countries?
very rarely
Which form of anthrax has a high mortality rate?
systemic (inhalation)
What is the infection of cutaneous anthrax?
necrotizing tissue due to a single exotoxin
What is the mode of infection with the systemic form of anthrax?
spore inhaled »_space; lung macrophage takes up spore »_space; spore germinates and divides »_space; bacteria enter bloodstream and cause septic shock
What type of infections does B. cereus cause?
most common = GI infections; also can cause eye infections; less common = respiratory infection
Why is anthrax considered a zoonotic disease?
if we come into contact with or consume an infected animal
What is the reservoir for anthrax?
environment (soil) and infected farm animals
What are the 4 virulence factors of B. anthracis?
toxins, capsule, ability to survive in macrophages, and plasmids
What are the 2 toxins B. anthracis produces and what do they cause/lead to?
edema toxin = skin infection (cutaneous anthrax) | lethal toxin = systemic anthrax
What is the virulence purpose of the capsule?
provides protection to bacteria against host immune system = causes it to not be immunogenic and why the host’s immune system cannot detect the pathogen easily
What are the 2 plasmids B. anthracis posses and what are their functions?
pX01 = genes encoding for the exotoxins of anthrax | pX02 = carries the genes for synthesis of capsule
What type of class of toxins do the exotoxins produced from B. anthracis belong to?
AB type | both toxins share the same B-subunit; A-subunit varies = bacteria switches between the two
How is B. anthracis able to produce 2 different types of exotoxins?
by minimizing the gene products that they need to produce
What is the B-subunit in the B. anthracis exotoxins considered to be? What is the benefit of this?
considered to be a protective antigen that can be used in vaccine development; the antigen is used to stimulate the immune system and provide protection from the pathogen and disease
Why is the anthrax vaccine inefficient?
lasts short period of time and has serious side effects
What is the mechanism of pathogenesis of the lethal toxin B. anthracis produces? What is the role of the A-subunit?
targets and kills macrophages where the A-subunit (lethal factor) acts as a protease
What are 2 ways anthrax can be diagnosed?
culture from infected tissues and PCR
What is the antibiotic that cutaneous anthrax is treated with?
Cipro = quinolone
Can we treat systemic anthrax with antibiotics? Why or why not?
No because the mortality rate is very high
What does “heat-labile” mean?
inactivated or altered molecule at hot temperatures
What are the two types of enterotoxins B. cereus can produce?
heat-stable and heat labile
What enzymes mediate tissue destruction during infection with B. cereus?
cytotoxic enzymes such as phospholipase C and cereolysin
What are the 4 types of people that are at risk of infection of B. cereus
those that ingest contaminated food, have penetrating injuries, receive intravenous injections, immunocompromised patients
What are the 2 forms of GI infections due to B. cereus?
emetic and diarrheal
Which form of GI infection due to B. cereus is caused by a heat-labile enterotoxin?
emetic form (vomiting)
Which form of GI infection due to B. cereus is caused by a heat-stable enterotoxin?
diarrheal form
What dictates which form of GI infection due to B. cereus that someone will get?
depends on which kind of food gets infected
What kind of food would the contamination lead to an emetic form of GI infection due to B. cereus?
rice
What kind of food would the contamination lead to a diarrheal form of GI infection due to B. cereus?
meat and vegetables
What are the characteristics of Clostridia?
anaerobic (NO O2), gram+ rods, produce endospores, produce many different toxins, unable to reduce sulfate to sulfite
Where are clostridia species usually found?
environments or intestines of animals
Compare the size of clostridia to e. coli
clostridia is larger than e. coli
What are the 4 common species of clostridia that will we be learning about?
C. difficile, C. perfringens, C. botulinum, C. tetani
What is the reservoir for C. difficile?
human colon
What is significant of C. difficile?
difficult to treat with antibiotics; it is one of the 3 superbugs
What diseases does C. difficile cause?
intestinal disorders
What can be a cause of infection due to C. difficile
use of antibiotics
What is the reservoir for C. perfringens?
soil and intestines of animals
What diseases does C. perfringens cause?
food poisoning and wound infections
What is the reservoir for C. botulinum?
soil and meat
What disease does C. botulinum cause?
botulism
What is the reservoir for C. tetani?
soil and intestines of humans and animals
What disease do C. tetani cause?
tetanus
What are the 3 reasons why clostridia are able to cause many different diseases?
1) spores allow them to survive in difficult/extreme environments | 2) rapid growth in a nutrient-rich O2-deprived environment means no sharing of nutrients | 3) can produce many different types of toxins (ie: enterotoxin and neurotoxins)
What does PMC stand for and which bacterium causes it?
pseudomembranous colitis due to C. difficile
What is pseudomembranous colitis and what causes it?
inflammatory disease of colon caused by antibiotics
How does taking antibiotics cause PMC?
kills other microbes present in the GI microbiota and takes over area
What percentage of normal individuals have C. difficile as part of their microbiota?
less than 5%
What induces C. difficile to grow and produce exotoxins? Which specific “inducers” mediate this?
antibiotics especially ampicillin and clindamycin
What immediately happens once C. difficile produces its exotoxins?
causes diarrhea »_space; ulceration of colon »_space; death if not treated
What are the exotoxins that C. difficile produce?
exotoxins A and B
What is the mode of transmission of C. difficile?
via spores
What are the 3 virulence factors of C. difficile?
exotoxins A and B and some adhesins
How do we diagnose/detect C. difficile in an infected individual?
run ELISA assay on a fecal sample to detect toxin A
Which antibiotics kill C. difficile?
vancomycin and metronidazole
What are some treatment methods to treat C. difficile infections?
stop taking antibiotics causing problem, early diagnosis, take probiotics
What are 3 prevention methods against PMC?
good hygiene, stop using antibiotics that cause PMC, early diagnosis
What are the characteristics of C. perfringens?
large rods (size depends on nutrient availability and species); non-motile, spores-rarely, hemolytic
What disease does C. perfringens most commonly cause?
food poisoning
What are the 3 common bacteria that cause food poisoning (in order)?
Campylobacter jejuni; Salmonella; C. perfringens
What kind of disease is food poisoning due to C. perfringens considered to be?
self-limiting disease
What does self-limiting disease mean?
disease goes away in short time because immune system is able to resolve the infection
How many cases/year does food poisoning occur due to C. perfringens?
250,000
What are some symptoms of food poisoning due to C. perfringens?
watery diarrhea with no fever
What is the most common contaminated food that causes food poisoning due to C. perfringens?
meat, poultry, fish
What causes diarrhea and cramps from food poisoning due to C. perfringens?
enterotoxins
What diagnostic test is used for food poisoning due to C. perfringens?
ELISA detects presence of enterotoxin in fecal sample
What another disease can C. perfringens cause? What can it lead to?
soft-tissue infections due to wounds »_space; can lead to gangrene
What toxin does C. perfringens produce to cause gangrene?
alpha toxin = causes gas gangrene
What is the treatment for wound infections due to C. perfringens?
antibiotics, antitoxin, and exposing wound to oxygen
What is an antitoxin?
antibody that targets and neutralizes the toxin
How would exposing the wound infected from C. perfringens to oxygen treat the infection?
C. perfringens is anaerobic = cannot live in presence of O2
What are some characteristics of C. botulinum?
large rods, does not form chains, can produce spores
What is botulism?
severe food poisoning by a toxin
What is the botulinum toxin?
a neurotoxin
How many types of botulinum toxin are there?
8 types depending on source of infection
Which botulinum toxins are commonly present in human cases?
A, B and sometimes E
What is the LD50 of the botulinum toxin?
0.4 kg
What is the result of botulism if not treated promptly?
paralysis in 2 days
What are the 4 types of botulism?
“classic”/foodborne | infant botulism | wound botulism | inhalation botulism
What is the “classic” or foodborne botulism?
consuming infected food = infects GI system
What are the symptoms of classic botulism?
blurred vision fixed dilated pupils, dry mouth, constipation, abdominal pain, no fever
How can classic botulism be prevented?
proper food preparation, no honey for infants
What is wound botulism?
opening on skin leads to infection in skin area
What is inhalation botulism?
due to bioweapon (inhale spores) = very rease
What is infant botulism?
due to consumption of honey (may have contained spores)
Which type of botulism is more common in the US?
infant botulism
What can cause death in classic botulism?
respiratory paralysis due to botulinum toxin
What are 3 types of treatment for classic botulism?
antitoxin, antibiotics, ventilatory support
For the antitoxin treatment of classic botulism, how will an antibody against the toxin be produced?
inject toxin into large animal (ie horses) and extract serum
Is there a vaccine available to treat botulism?
no
What are the characteristics of C. tetani?
large rods, motile, anaerobic, extremely toxic to oxygen toxicity
What causes tetanus? What type of life-event is usually associated with this disease?
traumatic wounds where C. tetani spores will invade and germinate = release toxin and get into bloodstream
What is the mortality rate of tetanus?
30-50%
What is the tetanus toxin? What does it cause?
neurotoxin causes paralysis
How do we diagnose for tetanus?
clinical symptoms
What treatments are available to treat tetanus?
antitoxin
How can one prevent tetanus?
vaccine (tetanus toxoid, part of DPT vaccine)
How many cases of tetanus are in the US?
low, less than 40 cases/year
What are the early signs of tetanus infection?
drooling, back spasms, irritability, sweat
How many doses does one need of the DPT vaccine and how often is the booster dose?
5 doses (as a child) and booster dose every 10 years
