Download Bacteria and Viruses

BACTERIA AND
VIRUSES
What a bunch of jerks
■ Compare how bacteria (e.g., Salmonella, Streptococcus, and Escherichia coli) and
viruses (e.g., common cold, influenza, and herpes) differ in how they are
transmitted, their impact on the human body, and how each is treated
Bacteria:
■ We are covered in bacteria on a daily basis
■ Humans have approximately 10, 000, 000, 000, 000 (10 trillion) cells
■ We are colonized by about 100, 000, 000, 000, 000 (100 trillion) bacteria
■ Beneficial bacteria live:
– On our skin
– In our intestinal tract
Commensal bacteria
■ Bacteria that live within us and on us without doing us harm are called commensal
bacteria
■ On the skin commensal bacteria are beneficial because:
– They prevent potentially harmful bacteria from growing due to competition
■
Called competitive inhibition
■ In the digestive tract:
– Competitive inhibition
– Provide nutrients and vitamins to the host from partially digested materials
When things go wrong!!!
■ Commensal bacteria can be harmful when they get past the largest organ the body
has
– What is the largest organ we have? (google it if you missed the lecture, its part
of the integumentary system)
■ This also occurs in the digestive tract when otherwise harmless bacteria are able to
get past the mucous membranes
Our natural defenses
■ Skin
– bacteria can’t typically penetrate the layers of skin unless there is a cut
– Dry environment, bacteria don’t live well in dry environments
– Shedding of skin cells constantly
■ Mucous membranes
– Lysozyme –digests cell walls of bacteria
– Antibodies secreted
– Sloughing of cells constantly
– Cilia (remember the lungs)
Natural defenses continued
■ Stomach
– Very acidic, hard to grow
– Helicobacter pilori can grow in the stomach and cause stomach ulcers, but
may also be beneficial to us
■ Small intestine
– Quickly flowing contents prevents colonization
■ Large instestine
– Competitive inhibition
Probiotics and prebiotics
■ Probiotics
■ Healthy bacteria are digested to help prevent harmful bacteria from growing in the
digestive tract
– Have to continually take them
– Can be taken as a pill, also advertised in many yogurts
■ Prebiotics
– Gives the nutrients beneficial bacteria require so they can dominate
How bacteria cause disease
(Pathogenesis)
■ First we are exposed to the bacteria
– This may be our normal commensal bacteria or new bacteria
– Enters our body by ingestion, inhalation, sexual transmission (Nisseria
gonorrhoeae), direct contact (wash your hands), bug bites (lyme disease via ticks)
■ Colonization follows
– Bateria finds a suitable environment and starts to grow
■ Growth and spread
– Bacteria may spread through the blood stream
■ Bacteria can be extracellular or intracellular
– Extracellular – lives outside host cells (Most bacteria)
– Intracellular – lives inside a host cell (Chalmydia pneumoniae, Yersinia pestis)
How they get us sick
■ Toxins
– Many bacteria produce toxins which can have specific effects
– Bacterial toxins can be extremely deadly (remember botulinum toxin?)
– The bacteria does not have to be present to cause illness as toxins can
contaminate food
■ Immune responses can actually make us feel worse, and in some cases can be
more deadly than the infection itself
– Sepsis
■
Overactive immune response causes inflammation throughout the body
– Can lead to death
Treating bacterial infections
■ Antibiotics are the main way of fighting off bacterial infections
– Some bacteria have tolerance to all known antibiotics and cannot be treated
■
Due to over-use of antibiotics
– Antibiotics work in a number of ways they can:
■
Kill bacteria
–
■
Typically by targeting parts of bacterial cells which are not present in humans
Slow bacterial growth allowing the immune system to kill bacteria
■ Take your full dose of antibiotics…. Or else!
Viruses
Viruses
■ Viruses are not alive
– DNA or RNA inside a particle which is able to invade specific types of cells
■ Viruses unlike bacteria do not normally live within us
– They must be transmitted directly to infect
■ Transmission can be through
– Particles in the air – the almighty sneeze (influenza)
■
–
–
–
http://www.discovery.com/tv-shows/mythbusters/videos/slow-motion-sneezes/
Direct contact –touching things with your hand then to the mouth through food
Sexual intercourse (STI’s)
Bug bites (mosquitos carrying west nile virus)
Viruses
■
Must invade a host cell to function
– Use a lock and key mechanism to enter cells.
– This limits the types of cells they can successfully invade
■
Upon invading cells they take over the cell
– Viruses can:
■
■
■
Rapidly reproduce, then cause the cell to explode releasing many new viral particles (Most viruses)
– (lytic cycle)
Reside dormant inside host cells until conditions are ideal (herpes zoster virus)
– Can sometimes lead to cancer
– (lysogenic cycle)
Continually release viral particles from a living cell without killing the cell directly (HIV, SARS)
Shingles (from the chicken pox virus)
■ The result of varicellazoster virus exiting the
lysogenic stage and
entering the lytic stage.
How viruses get us sick
■ Lots of different ways
– Immune system must kill infected cells
■
This can cause adverse affects
– Viruses directly kill cells releasing toxic compounds
– Some viruses kill immune system cells (HIV) resulting in immunocompromised
individuals (can’t fight other infections)
Treating viral infections
■ Nothing much can be done to kill viruses with drugs
– There are some drugs which help slow growth of HIV and a few other viruses
– If someone suspects they have received the rabies virus they can be
immunized after infection
■ Rest and plenty of fluid is your best bet
■ VIRUSES ARE NEVER TREATED WITH ANTIBIOTICS
Our immune system
■ Because viruses are intracellular:
– Our cells must recognize infected cells and destroy them
– Antibodies can also be used to neutralize viral particles
■ Bacteria are not always intracellular so:
– Macrophages can directly attack them
■
This can be aided by a molecule called complement
■
Antibodies can also bind to bacteria to signal that macrophages should attack them
■
https://www.youtube.com/watch?v=JnlULOjUhSQ
Prevention - Immunization
■ Two types of immunization
– Passive – antibodies are administered to fight an existing infection/toxin
– Active - vaccines
■ Active vaccines come in many forms but work because of memory cells
– Vaccines create an immune response which will allow your immune system to
quickly recognize and fight future infections
Vaccines
■ Many types:
– Inactivated (dead) bacteria or virus
– Attenuated – not as deadly as the original
■
■
–
May be passed through other animals so they are less deadly to us
Or genetically engineered to remove parts that make them harmful to us
Viral like particles (everything a virus has except its DNA and RNA)
■ Vaccines have wiped smallpox virus off the face of the earth (yay)
■ Vaccines have almost completely eradicated polio virus.
– (WHO is hoping to eliminate polio in the next 2 years)
Bacterial vaccines
■ DTaP
– Diphtheria, tetanus and pertussis (whooping cough)
■ Pneumococccal
■ Meningococcal
Viral vaccines
■ Hepatitis B
■ Rotavirus
■ Poliovirus
■ Influenza (yearly)
■ MMR
– Measles, Mumps, Rubella (german measles)
■ Varicella (chickenpox and shingles)
■ Hepatitis A
■ HPV (human papilloma virus)
I read it on the internet, it must be true
■ The best lies have an element of truth in them.
– No notes required for the rest of this lecture
1 in 912 people died
• They actually provided a link to Mercks study but failed to
mention:
• The study was over the course of 6 years (if I remember right)
• 9 from motor vehicle accident
• 8 from drug overdose or suicide
• 4 from gunshots
• 13 people who received the vaccine and 4 who received
placebos died of possibly relevant medical conditions
• The overall mortality rate does appear to be higher than US
averages for the ages involved in the study.
Vaers data confirms Gardasil is bad
■ Vaers is a database where anyone can report adverse effects after vaccination (no
proof of vaccination needed)
■ Over 40,000 events have been reported after Gardasil vaccination
– 130 deaths
■
Out of the well more than 40 million doses (2009 data is all I could find)
– Over 15,000 of these events are considered serious
– A quick look found that there have been 61 reported pregnancies after
vaccination
■
Surprisingly the pregnancies were not found to be due to the vaccination.
– 290 induced abortion related events were also reported.
Other interesting facts in this article
■ Gardasil isn’t curing already existing infections
– It’s not meant to!
■ A fairly recent study showed an increase in HPV infections in people over 19 years of
age
– A study of prevalence between 2003-2006 was compared to prevalence
between 2007-2010 and only the 14-19 year old age group showed a
decrease.
■ People who are already suffering from a chronic illness or are pregnant are at
greater risk of adverse affects if they get the vaccine
– Merck and the CDC agree
Conclusions?
■ Social media is a great way to spread “news” about anything because people don’t
bother to read anything but the headline
– This problem is only going to grow
■ Vaers data can be skewed easily
– Not every incidence is reported
■
Not every incidence is relevant
– Publicity can add to this
■ The vaccine isn’t for everyone, like all vaccines there is some risk associated
– The risk doesn’t appear to be any higher than with other vaccines, the real
question is what the long-term benefit of the vaccine is going to be
Assignment
■ HS20-HB2 Investigate various pathologies and ailments and their effects on cells,
tissues, organs, and systems of a healthy human.
■ HS20-DT1 Evaluate the tools and procedures used to diagnose and monitor medical
conditions
■ HS20-DT2 Recognize the importance of interpreting diagnostic findings to support
treatment options.
Assignment:
■
Research any virus or bacteria that is capable of causing a throat infection.
– Influenza A or B
– Rhinovirus
– Coronavirus
– Parainfluenza virus
– Respiratory syncytial virus (RSV)
– diphtheria
– Bordetella pertussis
– Streptococcus pyogenes
■
How is this infection transmitted (how does someone get this type of infection).
■
What symptoms does this infection cause
■
**** how can doctors diagnose respiratory system infections (what tools and methods might they
use), why is it important to get a correct diagnosis (look at group A streptococcus)
■
***How is this infection treated – if you want to include alternative therapies you may
■
***How can these infections be prevented.
■ https://www.youtube.com/watch?v=k1j8bh8_O_Q spread the snot around
■ https://www.youtube.com/watch?v=3vw0hIs2LEg where to sneeze