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Running head: METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
(MRSA)
Methicillin-Resistant Staphylococcus Aureus (MSRA)
Name
Date
1
METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
(MRSA)
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TABLE OF CONTENTS
Content
Page no
Introduction
3-4
History
4-5
Transmission
5-7
Predisposing factors
7-9
Causes
10-11
Symptoms
11-14
Diagnosis
15-16
Prevention and control
16-19
Treatment and cure
19-20
Recent research on MRSA
References
20
21-22
METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
(MRSA)
Introduction
The (MRSA) Methicillin-Resistant Staphylococcus aureus is a microorganism
specifically a bacterium; which is responsible for several departures from the body’s
physiological function. The bacterium is also referred to as (ORSA) Oxacillin-Resistant
Staphylococcus aureus (Carferkey, 1992). Any strain of bacteria Staphylococcus aureus that has
through the process of resistance and natural selection developed is known as MRSA.
According to Zimmerli, the strains are resistant to Penicillins such as Dicloxacillin,
Oxacillin, Methicillin and Nafcillin; the bacteria are also resistant to cephalosporin antibiotics.
Staphylococcus aureus that is not resistant to these antibiotic drugs is referred to as (MSSA)
Methicillin-Sensitive Staphylococcus aureus.
The resistance of such strains of bacteria does not render them to be highly infectious
than the rest of the strains of Staphylococcus aureus; which are not resistant to drugs (Mendez,
2013). The resistance only makes the Methicillin-Resistant Staphylococcus aureus infections
more cumbersome to treat; they with standard antibiotics and thus more perilous.
The infections are very common in populated areas such as prisons, maternity, and other
health care institutions where people have weak body immunity than in unpopulated areas and
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therefore the risk of nosocomial diseases is higher; this is because most of the MRSAs cause
infections on the skin. The infections caused by MRSA vary in intensity from mild skin infection
such as a boil or a sore to severe infections in the skin, surgical wounds, lungs, urinary tract
infection, and or infection in the blood stream (Carferkey, 1992). The infections can also be
acquired from livestock.
MRSA image
For healthy people, the bacteria may reside in the nose and on their skin, without causing
an infection. They are though the most common causes of nosocomial diseases; infections
acquired from the hospital or health care institutions (Rohde, 2011). The beddings and the rings
around staircases are the primary carriers of these bacteria in the hospitals; whenever patients
come into contact with the bacteria by holding the ring on the stairs or sleep on or under sheets
or blankets that carry the MRSA, they get infected.
History
According to Mendez, the bacterium was discovered in the 1880s when Staphylococcus
aureus infections were very common; they caused skin conditions that were either painful or soft.
These included scalded skin syndrome, impetigo, and boils. Other dangerous conditions resulting
from the bacteria Staphylococcus aureus include bacteria in the blood stream of an individual,
METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
(MRSA)
pneumonia and food poisoning caused by Staphylococcus aureus bacteria found in improperly
cooked food or poorly stored food. The diseases were very common during this era.
Increased conditions caused by Staphylococcus aureus led to discovery and invention of
antibiotic drugs in the 1940s, which included penicillin. Overuse and misuse of the antibiotics
helped bacteria to evolve naturally becoming resistant to the antibiotics (Mendez, 2013). The
Staphylococcus aureus changed, and penicillin was unable to treat the infections it caused,
leading to the introduction of methicillin that aimed at countering the increased cases of
penicillin-resistance by S.aureus.
The drug was efficient and very standard in the treatment of infections caused by the
Staphylococcus aureus till 1961 when a scientist from Britain came across the first strain of
Staphylococcus aureus a bacterium that was not treatable with Methicillin; this marked the birth
of Methicillin-Resistant Staphylococcus aureus. In the U.S, the first case was reported in 1968;
new strains of staphylococcus aureus have developed subsequently and are resistant to
methicillin and antibiotics that are closely related to methicillin (Carferkey, 1992).
Transmission
The infections by these Staphylococcus aureus can be transmitted through several ways:
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 Nosocomial diseases
The methicillin-resistant Staphylococcus can infect individuals in healthcare institutions
or the hospitals. Health Care-MRSAs are the most common; it can be patient-patient, patientvisitor, or patient-provider (Rohde, 2011). The healthcare providers are at a higher risk of
contracting the infections especially if they do not necessarily wash their hands; after attending
to a patient and before attending to the next patient.
According to Cafferkey, inpatients admitted to the hospital and outpatients visiting the
hospital obtain these infections from the beddings and other hospital facilities; such as toilets and
rings on the hospital pavements. A person comes into skin contact with surfaces where a patient
with MRSA infection had previously contaminated, and he or she also gets infected with the
MRSA.
Patients in the burn section are even at a higher risk and require a lot of care to prevent
them from contracting these resistant bacteria; they are very vulnerable due to the wounds on
their bodies (Zimmerli, 2009).
 Community-based transmission
Crowded environs such as prisons, military camps or barracks, and children’s home are
areas where the chances of infections by MRSA are high. Cases of such infections were first
reported in America and are still witnessed currently. There are high chances that people in
theses environs do not observe hygiene and thus, risk of contracting the infections are very high
(Mendez, 2013).
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Due to crowding, the bacteria spread very quickly causing infections to the inhabitants of
the area. The bacteria are known to reside in the nose or on the skin; the moment an individual is
wounded, they will be infected and pass the Staphylococcus aureus to most of their inmates,
families and or colleagues.
This form of transmission also involves athletes and students who contract the MRSAs
from lockers, desks, and doors; they obtain the bacteria immediately they come to contact with
infected surfaces on the cabinets, door knobs, and desks (Carferkey, 1992).
 Livestock transmission
Livestock also transmits a type of MRSA, which is most often asymptomatic in animals
producing food i.e. meat and milk products. The strain though does not affect animals is
dangerous to human beings. The Staphylococcus aureus bacteria are transmitted to humans when
they eat insufficiently cooked meat, milk and dairy products that are not pasteurized, and or
improperly boiled or unfrozen milk or meat. In this case, the livestock is the intermediate host
while human beings are the definitive host (Rohde, 2011).
Predisposing Factors
Several factors expose individuals to the Methicillin-Resistant Staphylococcus aureus:
1.
Age factor
The elderly and infant children are at a higher risk of contracting infections caused by
MRSA; this is because of their developing immunity (for infant children), and the depressed
immunity resulting from reduced body activities due to age (for elderly or the aged). The poor
protection from diseases in the two age groups (infant and the old) renders the individuals more
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susceptible to Methicillin-Resistant Staphylococcus aureus bacterial infections. Middle-aged and
mature youths have stronger immunity than the aged and the infant, and they are at a relatively
lower risk of contracting the diseases (Mendez, 2013).
2.
Underlying diseases
An individual with diseases like HIV, anemia, hypertension, TB, and other underlying
diseases will contract MRSA infections easily compared to a healthy person when the two are
exposed to these infections. The exposure is due to lowered immunity by the underlying
diseases; individuals with HIV are weak in immunity, and they are prone to most infections.
Any departure (physiological) of the body from its normal functioning will interfere with
an individual’s immunity; the Methicillin-Resistant Staphylococcus aureus will, therefore, have
fewer difficulties causing an infection, because the body does not fight back effectively. Diseases
will, therefore, render the body cells very susceptible to infection by MRSA (Carferkey, 1992).
3.
Skin break or wounds
People with wounds such as surgical or traumatic wounds, intravenous lines on hospital
patients, body piercing, burns, tattoos, or ulcers on the skin are at risk of contracting MRSA
infections. Simply because most of these infections are skin infections; they enter the body
through abrasions or openings on the human skin, causing either mild or severe conditions
(Rohde, 2011).
The MRSA can reside on the skin or in the nose of an individual harmlessly; without
causing any infection (Etinger, 2009). The moment they penetrate through the skin into the body,
which in most cases will only happen through a wound; they cause infections in different parts of
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the body. These include the bloodstream, the urinary tract, and or the skin itself; where a patient
has sores, boils and other more severe forms of skin infections.
4.
Medication
Individuals under medication, especially use of antibiotics are at a greater risk of having
Methicillin-Resistant Staphylococcus aureus. General use of antibiotics whether proper use,
misuse or underuse may expose one to resistant strains of bacteria (Mendez, 2013). Bacteria that
survive the attack by antibiotics tend to evolve or mutate forming resistant strains of the bacteria.
Staphylococcus aureus that survives medication of beta-lactam antibiotics will lead to
Methicillin-Resistant Staphylococcus aureus infections.
5.
Hospital environment
According to Estinger, both individuals working in the hospital and those visiting the
inpatients are at risk of contracting Methicillin-Resistant Staphylococcus aureus; most of the
MRSA are nosocomial diseases. People should take precaution such as washing their hands and
avoiding direct contact with patients’ wounds. They should also avoid contact with objects that
may be contaminated with the bacteria such as the pavement rings in the hospital.
Patients admitted to hospitals for a long time are at a greater risk of contracting the
methicillin-Resistant Staphylococcus aureus, their weak immunity and exposure to an
environment with the causatives of these infections increases their risk of contracting the
diseases (Rohde, 2011).
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Causes of MRSA infections
a.
Overuse or misuse of antibiotic drugs
Patients who have recently overused or misused antibiotics; taking under-dose, overdose
or late dosage may render Methicillin-Sensitive Staphylococcus aureus bacteria to turn resistant;
meaning that bacteria whose infection could have been treated using beta-lactam antibiotics,
becomes resistant to these antibiotics causing MRSA. The patient then transmits the bacteria to
other individuals through the several transmission methods discussed (Carferkey, 1992).
b.
Insufficiently cooked or unfrozen food
Certain forms of MRSA referred to as Livestock-associated MRSA are transmitted by
eating meat from livestock i.e. pigs, cattle and or poultry, which is not sufficiently cooked.
Drinking unpasteurized milk and dairy products such as cheese obtained from animals with the
resistant Staphylococcus aureus bacteria (Kolendi, 2010). The MRSA are asymptomatic in
livestock but very dangerous to human; they are cumbersome to treat. These forms of infection
can be prevented by sufficiently cooking meat, boiling milk, freezing and or taking pasteurized
dairy products.
c.
Naturally occurring (Garden variety) Methicillin-Resistant Staphylococcus aureus
A third of the world’s population has these bacteria in their noses or on their skin. The
condition of having the Staphylococcus aureus bacteria on the skin or in the nose, which does not
cause an infection, is referred to as being colonized by the bacteria. The condition turns fatal and
peril when the bacteria enter the body through a wound on the skin; causing a departure from the
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body’s physiological functioning; either on the skin, bloodstream or in the urinary tract (Mendez,
2013).
d.
Transmission from infected persons
Individuals can contract infections caused by Methicillin-Resistant Staphylococcus
aureus from suffering patients through contact with their wounds; the bacteria then enters the
body of these people causing infections (Kolendi, 2010). Physicians attending to MRSA patients
in the hospital may also contract the diseases if they come into contact with the wounds or
droplets from the patient’s body; therefore, people handing or visiting these patients should wear
protective gears to avoid contracting the disease.
Signs and symptoms of MRSA
The signs and symptoms of MRSA depend on the affected body part; different parts of
the body might have a varying range of symptoms. The infections also vary in intensity causing
different symptoms at various stages of the MRSA infection.

On skin and soft tissue
On the upper layer of the skin, the methicillin-resistant Staphylococcus aureus may show
the following symptoms during its early stages of infection:
a)
Boils
When an individual is infected with Methicillin-Resistant Staphylococcus aureus,
furuncles can develop on his or her skin. The boils form at any place on the skin but are most
likely to develop at infection site; they affect the hair follicle resulting in an infection full of pus
on the follicle. These in most cases develop on areas where hair, sweat and friction combine; the
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conflict leads to wearing of the skin surface resulting in an opening that allows entry of the
resistant staphylococcus bacteria (Mendez, 2013).
According to Espinosa, the boils may grow big in size and become more painful; this is
due to the accumulation of pus which over time bursts out and drains away leaving no scar.
Several boils may crowd together forming a dome shaped infection, which in most cases will
occur at the back of the thighs or the neck.
b)
Abscesses
Abscess refers to an infection (pus collection) under the skin which results from the death
of tissues as the white blood cells attack the resistant Staphylococcus aureus bacteria. A hole,
which fills with pus (a mixture of leucocytes, dead tissues, and bacteria) forms; it is seen as a
swelling under the skin (Carferkey, 1992).
METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
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c)
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Rash
A rash refers to areas that are red, irritated and inflamed on the skin surface.
d)
Impetigo
Impetigo, a very contagious skin infection; very common on the neck, hands and face of
infants and young children, caused by Staphylococcus aureus and for this case the MRSA.
Other symptoms which are also associated with the skin but the deeper layer of the skin
include:
• Sty
Sty refers to a bump, which develops on or in the lid of the eye due to blockage of the
glands (Kolendi, 2010). There is swelling, watering of the eye, light sensitivity and pain or
discomfort when the eye blinks.
• Cellulitis
The symptom can be observed on any part of the body, but most often affect the legs. The
area turns red, swells, experience high temperature, and becomes very painful. The pain and
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swelling are due to dying tissues as the cells of the blood (leukocytes) fight the MethicillinResistant Staphylococcus aureus bacteria (Mendez, 2013).
During late stages or when the MRSA bacteria infect internal body organs, it may cause
other more perilous conditions in the body; the following symptoms may be experienced or
observed.
 Rise in temperature
 A general feeling of unwell
 Confusion
 Pain in the muscles
 Giddiness
 Swelling, and tenderness in the affected part of the body
 Chills-a sudden penetrating sense of cold
More severe conditions caused on or in internal organs may include lung infection
(pneumonia), infection of the valves of the heart (endocarditis), and septic bursitis. Others
include infection of the tube that passes urine (UTI), bone infection (osteomyelitis), joint
infection (septic arthritis), and blood poisoning which would cause septic shock. The pressure of
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the blood dropping to perilously low level is also a complication that may be caused by MRSA
(Kolendi, 2010).
Diagnosis of MRSA infections
Individuals who suspect that they have diseases that are related to MRSA bacteria should
immediately visit and seek the help of a physician. The physician may choose to use any of the
following methods or may even combine several to determine whether an individual is suffering
from MRSA infections (Mendez, 2013).
i)
Physical examination
The doctor before conducting any tests in the laboratory will examine the skin of an
individual, to check for any changes, which may have resulted from infection by the MRSA
bacteria.
ii)
Patients history
The physician requires a patient to report chances of previous bacterial infections, and
treatment administered, or any exposure to MRSA bacteria such as contact with a wounded
person suffering from MRSA infections (Espinoza, 2008). The history helps the doctor to weigh
chances of infections by Methicillin-Resistant Staphylococcus aureus; this helps him or her
narrow down to the possible cause of the disease; the physician therefore knows what to test in
the laboratory.
iii)
Culturing of biopsy material or body fluid sample
Blood, urine, a sample from the skin, pus sample, or tissue sample is cultured to check for
Staphylococcus aureus. The sample is placed on a growth media, and if Staphylococcus aureus is
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isolated, the bacteria are exposed to antibiotics (Carferkey, 1992). Bacteria whose growth is not
inhibited by the antibiotics (methicillin) are referred to as MRSA. The patient whose test sample
had been cultured is, in this case, termed MRSA infected; the doctor thus administers treatment
to this patient.
In case the bacteria are inhibited by the action of the antibiotic (methicillin), the doctor
proceeds to test for other diseases that would have the same symptoms; because the patient has
no MRSA. The bacteria, in this case, are said to be MSSA Methicillin-Sensitive Staphylococcus
aureus (Etinger, 2009).
Prevention and control of MRSA
1.
Screening of patients
According to Estinger, most of the MRSA infections are obtained in the hospital; the
cases of infection can be reduced through screening of patients before admission. The screening
will reduce the chances of Methicillin-resistant Staphylococcus aureus in the nursing rooms or
wards; the infected patients should be treated before they contaminate the wards where other
patients will get the bacteria.
2.
Use of protective gears for people working in areas with Staphylococcus aureus
Employees working in hospitals, prisons, and other healthcare institutions should use
masks when entering the areas with people isolated due to MRSA. The individuals should also
use gloves and avoid contact with body fluids of infected patients or persons (Espinoza, 2008).
The Methicillin-Resistant Staphylococcus aureus is transmitted through contact with fluid or
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droplets from infected individuals; contact with their wounds, pus and urine on open skin or cuts
will contract the MRSA bacteria.
3.
Covering wounds, cuts, burns, or abrasions on the skin
According to Weinstein, the MRSA bacteria have been known to reside on the skin of
human body harmlessly but the moment there is a wound or an opening on the skin, the bacteria
enter the body causing an infection. Covering of wounds reduce the MRSA infections, as they
will in most cases require an injury to enter the human body.
4.
Observing proper hygiene
As the transmission of these diseases relies on contact, wash the hands after a long day of
interaction with people, visiting the hospital, visiting the toilet and using other resources such as
escalators and elevators. Most people will hold the resources with contaminated hands, and other
people will keep contracting the MRSA bacteria from there (Mendez, 2013). Washing hands
with soap, which is a disinfectant, kills the staphylococcus bacteria reducing chances of
infection.
5.
Sanitization of surfaces in hospitals
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Most surfaces in the hospital environment are likely to be contaminated with
Staphylococcus aureus bacteria. The bacteria can be found in the human skin including the
hands, and anytime a person holds the ring around the pavement, door knobs, presses a button on
the lift or holds the handle on the escalator, he or she contaminate that surface (Weinstein, 2002).
The laboratory is another place where the Staphylococcus may be found due to the patient
samples brought in containing these bacteria. Sanitization of these surfaces by use of
disinfectants reduces the MRSA infections.
6.
Proper cooking of meat and milk from livestock
Fully cooking meat will reduce infections by MRSA that are associated with the animal.
Sufficiently cooking meat, adequate pasteurization of milk and dairy products, and efficient
freezing of meat at -10 degrees to kill staphylococcus aureus bacteria present in the meat
(Mendez, 2013); are practices that can save people from MRSA.
7.
Treatment and isolation of infected persons
As the infections are easily transmitted in a community, infected people should be treated
to avoid infecting other people in the society. Infected individuals should be isolated from the
rest of the community till they have recovered from these infections; if allowed to interact with
other members of the community, they may end up infecting them with the MRSA (Weinstein,
2002).
8.
Creating public awareness
Creating awareness will reduce the deaths and complications resulting from MRSA
infections; most people observe symptoms of the MRSA infections, but because the infections
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are very mild especially in their early stages, they ignore till they experience severe
complications (Carferkey, 1992). Awareness will, therefore, help people to seek diagnosis early
enough and get treated; the infections are treatable especially in their early stages.
9.
Controlling the use of antibiotics and other medications
Use of antibiotics whether proper or misuse may result in certain bacteria developing
resistance to antibiotics. Once the bacteria survive an attack by an antibiotic, they develop
resistance to that type of bacteria.
Treatment of MRSA infections
Methicillin-Resistant Staphylococcus aureus infections treatment is generally by use of
antibiotics. The bacteria are beta-lactam antibiotics resistant (traditional antibiotics), and they
require more advanced antibiotics to treat.
The hospital-acquired or nosocomial Methicillin-Resistant Staphylococcus aureus
bacteria are resistant to a very wide range of antibiotics and only susceptible to an antibiotic
known as Vancomycin (Mendez, 2013). Other antibiotics that can treat the nosocomial MRSA
are linezolid, which are newer antibiotics of the class Oxazolidinones, and an antibiotic known as
Daptomycin. The drugs recommended for pneumonia caused by MRSA include linezolid,
clindamycin, and Vancomycin.
MRSA associated with community is treated using several antibiotics as it is also
resistant to a variety of antibiotics. These types of MRSA have an antimicrobial susceptibility of
a greater spectrum; they can be treated using Tetracyclines, clindamycin, and sulfa drugs, but
Vancomycin is the antibiotic that is currently believed to fight or cure MRSA infections
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(Weinstein, 2002). Newer Daptomycin, and Oxazolidinones such as linezolid, are also useful in
the treatment of these diseases.
Recent research
Researchers led by Kim Lewis, who is a professor of biology at the University and a
director of an antimicrobial center, realized that the resistant strains of Staphylococcus aureus
were evading the action of drugs, by entering a dormant state Mendez, 2013). Which drugs
cannot work on as they kill bacteria by targeting active functions of the cell, the antibiotics are
rendered useless by the inactive bacteria.
According to Rohde, the group deduced that use of a drug that awakens the bacteria
(ADEP antibiotic), together with other traditional antibiotics will kill the MRSA. Bacteria that
develop resistance towards the ADEP are very susceptible to beta-lactam antibiotics, and this is
an important discovery especially now that the utility of antibiotics is diminishing.
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Reference
Cafferkey, M. T. (1992). Methicillin-resistant Staphylococcus aureus: Clinical management and
laboratory aspects. New York: M. Dekker.
Ettinger, S. J., & Feldman, E. C. (2009). Textbook of Veterinary Internal Medicine. London:
Elsevier Health Sciences.
Espinoza, C., Ostrosky, L., Brown, E. L., Slomka, J., & University of Texas Health Science
Center at Houston. (2008). Prevalence and risk factors of methicillin-resistant
Staphylococcus aureus in critically-ill hospitalized patients in a tertiary care center in
Houston, Texas: An active surveillance pilot project. (Masters Abstracts International,
47-1.)
Kolendi, C. L. (2010). Methicillin-resistant Staphylococcus aureus (MRSA): Etiology, at-risk
populations and treatment. Hauppauge] N.Y: Nova Science Publishers.
Méndez-Vilas, A., & International Conference on Antimicrobial Research. (2013).Worldwide
research efforts in the fighting against microbial pathogens: From basic research to
technological developments. S. l.: Formatex.
Rohde, R. E. (2011). Methicillin resistant Staphylococcus aureus (MRSA): Knowledge, learning,
and adaptation : I guess everything changes when it happens to you : their stories.
Saarbrücken: LAP Lambert Academic Publishing.
Weinstein, R. A., & Bonten, M. J. M. (2002). Infection Control in the ICU Environment. Boston,
MA: Springer US.
METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
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Zimmerli, M. (2009). Methicillin-resistant staphylococcus aureus (MRSA) among dental
patients: A problem for infection control in dentistry?. S.l.: s.n.
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Multiple choice questions
1. What does an immunochromatographic assay do?
Uses mouse monoclonal IgG Ab's to Influenza A and/or B nucleoproteins to form
a complex w/Influenza A and/or B viral antigens
2. What are 6 infections that Staphylococcal bacteria can cause? (doesn't have to
be MRSA--any staph)
1. Toxic shock syndrome
2. Respiratory infection
3.Osteomyelitis
4. Food poisoning
5. Endocarditis
6. Skin infections (abscess, furuncle, carbuncle, impetigo, wounds)
3. 3 things that specifically MRSA causes
1.Skin infection
2. Sepsis
3. Necrotizing pneumonia
4. What is a folliculitis?
Pyogenic infection in the hair follicle
Called a stye if in the base of the eyelid
5. What is a furuncle?
Extension of folliculitis
Large, painful, underlying dead and necrotic tissue (abscess)
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METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
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6. What are carbuncles?
Multiple interconnected boils that extend into deeper tissues
Fever and chills point to systemic spread
7. 3 types of damage Staph aureus can cause
Infection
Intoxication
Infection and Intoxication
8. Why is Levofloxacin used to treat MRSA?
It inhbits DNA gyrase (involved in DNA replication)
9. Why are ceftriaxone, penicillin, and methicillin used to treat MRSA?
They inhibit cell wall synthesis in the Staph Aureus
10. Why is Trimethoprim used to treat MRSA?
It prevents folic acid synthesis
11. Why are Clarithromycin and Erythromycin used to treat MRSA? What type of
antibiotics are they?
Macrolides
They inhibit protein synthesis, specifically the 50S ribosomal subunit
12. What type of bacteria are Staphylococci? How are they arranged?
Gram-positive coci
Arranged as grape-like clusters
13. What 2 metabolic characteristics do Staphylococci have?
Facultative anaerobes
Catalase positive
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METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
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What two things comprise the mecA complex?
mecA gene and regulatory elements
14. What are ccr genes and what do they do?
They are site specific recombinases
They can catalyze precise excision and site and orientation specific integration of SCCmec
elements
15. Where are the different places that Staph aureus can cause disease?
In every organ system
(skin, bone, food poisoning, pneumonia, meningitis, sepsis)
16. Why does Staph aureus cause so many diseases?
Because it has a variety of virulence factors
17. Why are different strands of Staph aureus different in causing disease?
Not all virulence genes are present or expressed the same in every strain
18. The type of disease caused by Staph aureus depends on what 3 things?
Location in the body
Environment in the host
Virulence factors expressed by the strain
19. What are 6 examples of virulence factors that may play a role in the
pathogenesis of staphylococcal infections?
Protein A
Fibronectin-binding protein
Cytolytic exotoxins
Enzymes
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METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
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Slime production
Superantigen exotoxins
20. What two things does the capsule/slime do to help S. aureus in its pathogenesis?
Prevents phagocytosis
Promotes adherence to cells and prosthetic devices
21. What two things does Protein A do to help S. aureus in its pathogenesis?
Binds Fc terminus of IgG
Prevents opsonization and Complement activation (classical)
22. What does the Fibronectin binding protein (teichoic acid) do to help S. aureus in
its pathogenesis?
Promotes binding to mucosal cells and tissue matrices
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