DDT 14 - A review of disease causing bacteria Flashcards
give examples of gram positive bacteria
Clostridium botulinum Clostridium tetani Bacillus anthracis Staphylococcus aureus Streptococcus pyogenes
Clostridium botulinum
- botulism due to food containing neurotoxin; lethal dose 1-2µg; causes respiratory paralysis, morbidity 65%.
Clostridium tetani
anaerobic, endospores; tetanus or lockjaw due to neurotoxin; convulsive contractions in voluntary muscles; morbidity 50%
Bacillus anthracis
anthrax; septicaemic infection in farm animals but transmissible to humans; Prevention - slaughter and burning.
Staphylococcus aureus
Commonly found on skin and typically will not cause any health issues. However some strains can be highly pathogenic. Emergence of antibiotic-resistant S. aureus now a major health concern worldwide (MRSA)
Streptococcus pyogenes
Common cause of sore throat (strep-throat) but can also cause severe infections including meningitis, pneumonia and necrotizing fasciitis
how does bacillus anthracis reproduce?
Forms spores which can survive harsh conditions for decades. Become re-activated when they enter a host organism
how does bacillus anthracis enter the human body?
Most cases are via the skin but can also occur by inhalation or ingestion of spores. Inhalation is the most dangerous route of infection (up to 90% mortality)
where is clostridium botulinum bacteria most commonly found
in food that has been improperly stored in cans - low O environment
what does clostridium botulinum cause?
severe food poisoning
leading to paralysis
prodcues botulinum toxin - most potent neurotoxin known
how is clostridium botulinum used in medicine?
to treat diseases involving muscle spasms as well as cosmetic surgery (Botox injections)
name examples gram negative bacteria
bacilli - vibrio cholerae, legionella pneumophila, e. coli, salmonella
vibrio cholerae description and how is it transmitted?
Flagellated bacteria – highly motile. Spread through drinking contaminated water
how does vibrio cholerae become toxic to body
Bacteria colonise the intestine and produce cholera toxin – increases secretion of water into the intestine leading to severe diarrhea and dehydration
how is vibrio cholerae treated?
Development of oral rehydration therapy has significantly reduced mortality - millions of lives saved every year
where is legionella pneumophila found
Bacteria most commonly found in water contained within air conditioning systems, showers and water tanks.
how is legionella pneumophila spread?
Spread when water is aerosolized leading to inhalation of bacteria
symptoms of legionella pneumophila
fever headache chills nausea diarrhoea
What can some strains of e.coli cause
cause severe food poisoning, gasteroenteritis, diarrhea and urinary tract infection
e.coli. can be serious for
children and elderly
how is salmonella enterica is spread?
spreads via improperly stored or cooked food especially meat, eggs and dairy.
what does salmonella cause?
Common form of food poisoning, leads to diarrhea, fever, vomiting, and abdominal cramps
salmonella typhi is related to salmonella enterica
typhi is subset of enterica
how is salmonella typhi spread
Spread by contaminated food or water, most common in developing regions with poor sanitation.
what does salmonella typhi cause
Causes typhoid fever - skin rash, fever, weakness, abdominal pain and vomiting.
how is salmonella typhi mortality rate reduced?
Vaccination, sanitation and antibiotics have reduced mortality rate from 20% to less than 1%
what are symptoms of salmonella typhi
abdomnial pain
vomtting
muscle weakness
mycoplasma
simple cell
smaller than bacteria
no cell wall
cause respiratory infection - pneumonia and urinary tract infection
Rickettsiae is what type of parasite and what are the usual hosts
Obligate intracellular parasites of arthropods and mammals, must be grown on living cells
how is rickettsiae transmitted
Usually spread to humans through arthropod vectors, including ticks, fleas and lice.
what does rickettsiae cause
the vector for humans and its morbidity?
causes classical typhus fever, the vector is the human louse; presents as an acute fever with 10-20% morbidity
how is rickettsiae treated or prevented?
Can be treated with antibiotics and prevented using insecticides to decontaminate living spaces and clothes during outbreaks, killing the lice that spread the disease
Rickettsia rickettsi - causes Rocky Mountain spotted fever
Leads to tash and fever
Spread by tick bites
Severe cases can lead to partial paralysis of the lower extremities or gangrene requiring amputation
what kind of parasite is chlamyudia trachomatis
Gram negative, obligate intracellular parasitic bacteria
chlamydia strange symptoms
Can remain symptomless for long periods of time (approx. 50% of cases).
what does chlamydia also cause
Can also infect the eyes – commonly passed from mother to child during birth. Can also be spread by flies, by direct contact or by contamination of personal items such as towels
Trachoma
repeated infections of the conjunctiva leads to scarring which causes the eyelashes to turn inwards. This causes the eyelashes to scrape against the eyeball every time the patient blinks, leading to scarring and eventual loss of vision
first antibiotics used to treat bacteria
1907 Paul Ehrlich synthesized an organic arsenic compound, arsphenamine, first effective treatment for syphilis
Alexander Flemming’s contribution to science
1929 Alexander Fleming discovers action of products of fungus Penicillium notatum
who and what treated streptococcal infection
1935 Domagk treats a streptococcal infection with the dye ‘prontosil
what lead to discovery of sulphonamides
due to breakdown in the body and release of sulphanilamide which led to development of the sulphonamides (range of modified versions of the drug with different properties)
when and who first purified penicillin
1940 Chain and Florey
4 mechanisms of action of antibodies
Inhibition of cell wall synthesis
Inhibition of cell membrane function
Inhibition of protein synthesis
Inhibition of nucleic acid synthesis
2 types of antibodies
bacteriostatic
bactericidal
bacteria that inhibit cell wall synthesis
Does not kill the pathogen directly but results in cell lysis due to internal osmotic pressure
e.g., Penicillins, Vancomycin
bacteria that inhibit cell membrane function
Uses differences between the cell membranes of Prokaryotic and Eukaryotic cells
eg., Polymyxins, Nystatin;
bacteria that inhibit protein synthesis
Use the differences between Prokaryotic and Eukaryotic ribosomes
e.g. Chloramphenicol, Tetracyclines;
bacteria that inhibit nucleic acid synthesis
Inhibit various aspects of DNA and RNA synthesis, for example by binding to the enzyme RNA polymerase
eg. Rifampin, Sulphonamides.
dangers of indiscriminate use of antibodies
hypersensitivity -> rash/fever
disrupt natural flora in body - no competing bacteria to stop pathogenic bacteria - eradicates part of our immune system
mask serious illness - when it is still present - no receiving right treatment
drug toxicity - allergic reaction
bacteria can develop drug resistance
