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Other members of the normal microbiota can also cause opportunistic infections under certain conditions. This often occurs when microbes that reside harmlessly in one body location end up in a different body system, where they cause disease. For example, E. coli normally found in the large intestine can cause a urinary tract infection if it enters the bladder. This is the leading cause of urinary tract infections among women.

Members of the normal microbiota may also cause disease when a shift in the environment of the body leads to overgrowth of a particular microorganism. For example, the yeast Candida is part of the normal microbiota of the skin, mouth, intestine, and vagina, but its population is kept in check by other organisms of the microbiota. If an individual is taking antibacterial medications, however, bacteria that would normally inhibit the growth of Candida can be killed off, leading to a sudden growth in the population of Candida , which is not affected by antibacterial medications because it is a fungus. An overgrowth of Candida can manifest as oral thrush (growth on mouth, throat, and tongue), a vaginal yeast infection , or cutaneous candidiasis . Other scenarios can also provide opportunities for Candida infections. Untreated diabetes can result in a high concentration of glucose in the saliva, which provides an optimal environment for the growth of Candida, resulting in thrush. Immunodeficiencies such as those seen in patients with HIV, AIDS, and cancer also lead to higher incidence of thrush. Vaginal yeast infections can result from decreases in estrogen levels during the menstruation or menopause. The amount of glycogen available to lactobacilli in the vagina is controlled by levels of estrogen; when estrogen levels are low, lactobacilli produce less lactic acid. The resultant increase in vaginal pH allows overgrowth of Candida in the vagina.

  • Explain the difference between a primary pathogen and an opportunistic pathogen.
  • Describe some conditions under which an opportunistic infection can occur.

Stages of pathogenesis

To cause disease, a pathogen must successfully achieve four steps or stages of pathogenesis : exposure (contact), adhesion (colonization), invasion, and infection. The pathogen must be able to gain entry to the host, travel to the location where it can establish an infection, evade or overcome the host’s immune response, and cause damage (i.e., disease) to the host. In many cases, the cycle is completed when the pathogen exits the host and is transmitted to a new host.

Exposure

An encounter with a potential pathogen is known as exposure or contact . The food we eat and the objects we handle are all ways that we can come into contact with potential pathogens. Yet, not all contacts result in infection and disease. For a pathogen to cause disease, it needs to be able to gain access into host tissue. An anatomic site through which pathogens can pass into host tissue is called a portal of entry . These are locations where the host cells are in direct contact with the external environment. Major portals of entry are identified in [link] and include the skin, mucous membranes, and parenteral routes.

Questions & Answers

What is microbiology
Victoria Reply
please what is the topic today.
Anafure Reply
I hope u are doing good
Anafure
Yes ooo u
Daniel
Victoria
Victoria
Yes
Victoria
what is immunoglobulin specifications
hop Reply
what if she is having stomach pain ND also running temprature
Samuel Reply
i wante to study medicine in university so how i should prepare my self
Lissa Reply
yea I also want to study pls hw Will I prepare myself
Shifau
first you have to prepare yourself in biology physics and chemistry
Mushahid
microorganism functions
NUHU Reply
what are the functions of microoganism
Victoria
Maintains the functions of body parts e.g Normal floras of the vagina
Nantongo
definition of cell
Shifau
how does the helicobacteri pylori affect the stomach walls?
Erick Reply
hi
Allan
Hlo
SUMIT
hi
Umar
hi
Umar
when the stomach is been affected with helicobacteria what are the preventive measure to be considered to ensure specific outcome?
Umar
yeah
Ayan
proper alimentation( feed properly),avoid eating lot of pepper but the main point is nutrition if you feed well the bacteria won't cause digestion of the stomach wall and thus you will be fine
Nanjoh
what is microbiology
vijay Reply
microbiology is the scientific study of microorganisms .microorganisms are those organisms that are too small to see with the naked eye ex-bacteria fungi
Yashkin
a branch of biological science concerned with organisms that can not be observed with a naked eye
Mooya
what are the types of granulocytes and explain
lord
polymorpho nuclear leukocyte, known as granulocyte are divide into three,1-polymorpho eosinophil 2-polymorpho basophil 3-polymorpho neutrophil
Musa
microbiology is scientific study of microorganism which can nt be seen by naked eye,for example bacteria,viruses, protozoa ad fungi.
Emma
microbiology is the scientific study of microorganisms
Atia
good
Samuel
microbiology is the study of micro organisms by the use of microscope to know how they react and respire to it environments
Daniel
microbiology is a branch of science which studies microbe
Ivy
microbiology is the study of microoganism
paul
microbiology is the study of tiny organisms which are difficult to be seen by naked eyes
hop
I want to know more about sample collection on the field
Ama Reply
blood collection and urinarysis
Lizzy
2143
Lizzy
yes
Lizzy
In the periodic table the number on the upper left hand side is what
Aurelia Reply
Hydrogen
Tob
am not talking about the elements
Aurelia
Is it the atomic number or the mass number
Aurelia
hologen
Usman
differences between acid fast and non acid fast bacilli
ANTHONY Reply
acid fast have cell wall that holds to carbol fuschin stain while non acid fast doesn't have. it readily releases out the primary stain the carbol fuschin.
LAFIA
where do I post a question that isn't related to that topic
eklectc
hi everyone
kennedy
hello
Olivia
for sure, this question is not related to the topic.
LAFIA
can someone explain the process of glycolysis and the electron transport chain? I'm so freakin lost. it loses carbons, gains hydroxyls, gains, loses Hydrogens....ugh it's like a foreign language to me! or direct me to a youTube video or something that will make this seem easier to concept?
eklectc
it's a loaded question, sorry!
eklectc
why is DNA a genetic material
Mcbeth Reply
DNA is genetic material because it contains chromosome contains the traits which includes characters and behavioral characteristics
chima
why is it difficulty to classfy protista
Tanaka
Good
Eddy
what is infection prevention
Muhammed Reply
good hygiene
Dhaqan
way of preventing disease causing germs
henry
maintenance of sterilization
Pooja
h
Faustina
describe the components of the epidemiology triangle
Muhammed Reply
Hai
Nantongo
hii
Md
where from you
Md
i am Indian
Md
you
Md
Hello friend
effiong
How are you people doing
effiong
أ‌) Host factor ب) pathogen ج) environment
Widad
Hello
Kofi
Hi
Widad
hey hi
kalai
The epidemiologic triangle is made up of three parts: agent, host and environment
Princess
please can a microbiologist will work at hospital
Usman
yes but some state whose have deficiency of medical laboratories practictioners
jamilu
yes, as a lab scientists
kehinde
pls what are the layers of the skin
Jenny
Epidermis and Dermis
Nantongo
EPIDERMIS is the outer layer of the skin and it made up of three layers. Cornified, Granular and Malpighian layer. DERMIS is composed mainly of connection tissues, sweat glands, sebaceous glands, sensory nerves endings and fat cells.
MASA
The epidemiologic triangle is made up of three parts: agent, host and environment.
Kamaluddeen
what are the fluids used in biochemistry Lab used to diagnose diseases
Jb Reply

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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