Methicillin Resistant Staphylococcus Aureus
- Methicillin Resistant
infection that is
causing increasing concern and alarm is Methicillin Resistant
commonly referred to as MRSA. This most common setting for
MRSA infection is actually in a healthcare facility. This is
problem for those of us with
lymphedema as we ar so often hospitlized
Information for the Public
is Staphylococcus aureus (staph)?
aureus, often referred to simply as "staph," are
bacteria commonly carried on the skin or in the nose of healthy people.
Approximately 25% to 30% of the population is colonized (when
bacteria are present, but not causing an infection) in the
nose with staph bacteria. Sometimes, staph can cause an infection.
Staph bacteria are one of the most common causes of skin
infections in the United States. Most of these
skin infections are minor (such as pimples and boils)
and can be treated without antibiotics (also known as antimicrobials or
antibacterials). However, staph bacteria also can cause serious
infections (such as surgical wound infections,
bloodstream infections, and pneumonia).
is MRSA (methicillin-resistant Staphylococcus aureus)?
Some staph bacteria are
resistant to antibiotics.
MRSA is a type of staph that is resistant to antibiotics called
beta-lactams. Beta-lactam antibiotics include methicillin and other
more common antibiotics such as oxacillin,
penicillin and amoxicillin. While 25% to 30% of the
population is colonized with staph, approximately 1% is colonized with
gets staph or MRSA infections?
Staph infections, including
MRSA, occur most frequently among persons in hospitals and healthcare
facilities (such as nursing homes and dialysis centers) who have
immune systems. These healthcare-associated staph infections
include surgical wound infections, urinary tract infections,
bloodstream infections, and pneumonia.
is community-associated MRSA (CA-MRSA)?
Staph and MRSA can also cause
illness in persons outside of hospitals and healthcare facilities. MRSA
infections that are acquired by persons who have not
been recently (within the past year) hospitalized or had a medical
procedure (such as dialysis, surgery, catheters)
are know as CA-MRSA infections. Staph or MRSA infections in the
community are usually manifested as
skin infections, such as pimples and boils,
and occur in otherwise healthy people.
common are staph and MRSA infections?
Staph bacteria are one of the
most common causes of skin infection in the United States and are a
common cause of pneumonia, surgical wound infections, and
bloodstream infections. The majority of MRSA infections occur
among patients in hospitals or other healthcare settings; however, it
is becoming more common in the community setting. Data from a
prospective study in 2003, suggests that 12% of clinical MRSA
infections are community-associated, but this varies by geographic
region and population.
does a staph or MRSA infection look like?
Staph bacteria, including
MRSA, can cause skin infections that may look like a pimple or boil and
can be red, swollen, painful, or have pus or other drainage. More
serious infections may cause pneumonia, bloodstream infections, or
surgical wound infections.
certain people at increased risk for community-associated staph or MRSA
CDC has investigated clusters
of CA-MRSA skin infections among athletes, military recruits, children,
Pacific Islanders, Alaskan Natives, Native Americans, men who have sex
with men, and prisoners.
Factors that have been associated with the spread of MRSA skin
infections include: close skin-to-skin contact, openings in the skin
such as cuts or abrasions, contaminated items and surfaces, crowded
living conditions, and poor hygiene.
How can I
prevent staph or MRSA skin infections?
Practice good hygiene:
- Keep your hands clean by
washing thoroughly with soap and water or using an alcohol-based hand
- Keep cuts and scrapes clean
and covered with a bandage until healed.
- Avoid contact with other
people’s wounds or bandages.
- Avoid sharing personal
items such as towels or razors.
people who are positive for the human immune deficiency virus (HIV) at
increased risk for MRSA? Should they be taking special precautions?
People with weakened immune
systems, which include some patients with HIV infection, may be at risk
for more severe illness if they get infected with MRSA. People with HIV
should follow the same prevention measures as those without HIV to
prevent staph infections, including practice good hygiene, cover wounds
(e.g., cuts or abrasions) with clean dry bandages, avoid sharing
personal items such as towels and razors, and contact their doctor if
they think they have an infection.
I get a staph or MRSA infection at my health club?
In the outbreaks of MRSA, the
environment has not played a significant role in the transmission of
MRSA. MRSA is transmitted most frequently by direct skin-to-skin
contact. You can protect yourself from infections by practicing good
hygiene (e.g., keeping your hands clean by washing with soap and water
or using an alcohol-based hand rub and showering after working out);
covering any open skin area such as abrasions or cuts with a clean dry
bandage; avoiding sharing personal items such as towels or razors;
using a barrier (e.g., clothing or a towel) between your skin and
shared equipment; and wiping surfaces of equipment before and after use.
should I do if I think I have a staph or MRSA infection?
See your healthcare provider.
staph and MRSA infections treatable?
Yes. Most staph and MRSA
infections are treatable with antibiotics. If you are given an
antibiotic, take all of the doses, even if the infection is getting
better, unless your doctor tells you to stop taking it. Do not share
antibiotics with other people or save unfinished
antibiotics to use at another time.
However, many staph skin
infections may be treated by draining the abscess or boil and may not
require antibiotics. Drainage of skin boils or
abscesses should only be done by a healthcare provider.
If after visiting your
healthcare provider the infection is not getting better after a few
days, contact them again. If other people you know or live with get the
same infection tell them to go to their healthcare provider.
it possible that my staph or MRSA skin infection will come back after
it is cured?
Yes. It is possible to have a
staph or MRSA skin infection come back (recur) after it is cured. To
prevent this from happening, follow your healthcare provider’s
directions while you have the infection, and follow the prevention steps after
the infection is gone.
I have a staph, or MRSA skin infection, what can I do to prevent others
from getting infected?
You can prevent spreading
staph or MRSA skin infections to others by following these steps:
- Cover your
wound. Keep wounds that are draining or have pus covered
with clean, dry bandages. Follow your healthcare provider’s
instructions on proper care of the wound.
Pus from infected wounds can contain staph and MRSA, so
keeping the infection covered will help prevent the spread to others.
Bandages or tape can be discarded with the regular trash.
- Clean your
hands. You, your family, and others in close contact
should wash their hands frequently with soap and warm water or use an
alcohol-based hand sanitizer, especially after changing the bandage or
touching the infected wound.
- Do not share
personal items. Avoid sharing personal items such as
towels, washcloths, razors, clothing, or uniforms that may have had
contact with the infected wound or bandage. Wash sheets, towels, and
clothes that become soiled with water and laundry detergent. Drying
clothes in a hot dryer, rather than air-drying, also helps kill
bacteria in clothes.
- Talk to your
doctor. Tell any healthcare providers who treat you
that you have or had a staph or MRSA skin infection.
should I do if someone I know has a staph or MRSA infection?
If you know someone that has a
staph or MRSA infection you should follow the prevention steps.
are the criteria for distinguishing community-associated MRSA (CA-MRSA)
from healthcare-associated MRSA (HA-MRSA)?
Persons with MRSA infections
that meet all of the following criteria likely have CA-MRSA infections:
- Diagnosis of MRSA was made
in the outpatient setting or by a culture positive for MRSA within 48
hours after admission to the hospital.
- No medical history of MRSA
infection or colonization.
- No medical history in the
past year of:
- Admission to a nursing
home, skilled nursing facility, or hospice
- No permanent indwelling
catheters or medical devices that pass through the skin into the body.
is the main way that staph or MRSA is transmitted in the community?
The main mode of transmission
of staph and/or MRSA is via hands which may become contaminated by
contact with a) colonized or infected individuals, b) colonized or
infected body sites of other persons, or c) devices, items, or
environmental surfaces contaminated with body fluids containing staph
or MRSA. Other factors contributing to transmission include
skin-to-skin contact, crowded conditions, and poor hygiene.
is a MRSA infection diagnosed?
In general, a culture should
be obtained from the infection site and sent to the microbiology
laboratory. If S. aureus is isolated, the
organism should be tested as follows to determine which antibiotics
will be effective for treating the infection.
Skin Infection: Obtain
either a small
biopsy of skin or drainage from the infected site. A culture
of a skin lesion is especially useful in recurrent or persistent cases
skin infection, in cases of antibiotic failure, and in cases
that present with advanced or aggressive infections.
Obtain a sputum
culture (expectorated purulent sputum, respiratory lavage, or
blood cultures using aseptic techniques.
Infection: Obtain urine cultures using aseptic
are CA-MRSA infections treated?
Staph skin infections, such as
boils or abscesses, may be treated by incision and drainage, depending
on severity. Antibiotic treatment, if indicated, should be guided by
the susceptibility profile of the organism.
do CA-MRSA and HA-MRSA strains differ?
Recently recognized outbreaks
of MRSA in community settings have been associated with strains that
have some unique microbiologic and genetic properties compared with the
traditional hospital-based MRSA strains, suggesting some biologic
properties (e.g., virulence factors) may allow the community strains to
spread more easily or cause more skin disease. Additional studies are
underway to characterize and compare the biologic properties of HA-MRSA
and CA-MRSA strains.
There are at least three
aureus strains in the United States that can cause
CA-MRSA infections. CDC continues to work with state and local health
departments to gather organisms and epidemiologic data from known cases
to determine why certain groups of people get these infections.
MRSA infections a reportable disease?
MRSA is reportable in several
states. The decision to make a particular disease reportable to public
health authorities is made by each state, based on the needs of that
individual state. To find out if MRSA is reportable in your state, call
your state health department.
MRSA is the term used for
bacteria of the Staphylococcus
aureus group (S. aureus) that
are resistant to the usual
antibiotics used in the treatment of infections with such organisms.
Traditionally MRSA stood for methicillin resistance but the term
refers to a multi-drug resistant group. Such bacteria often have
many antibiotics traditionally used against S.aureus.
This resistance to methicillin
is due to the presence of
the mec gene in the bacteria. This alters the site
at which methicillin
binds to kill the organism. Hence, methicillin is not able to
to the bacteria.
Infections caused by MRSA are
the same as other
staphylococcal infections because the organism itself is not any more
(or infectious) than usual type S.aureus.
Like other S.aureus,
MRSA can colonise the skin and
body of an individual without causing sickness, and in this way it can
on to other individuals unknowingly. Problems arise in the treatment of
infections with MRSA because antibiotic choice is very limited.
is MRSA found?
MRSA is found worldwide,
predominantly in hospitals and
institutions such as nursing homes. Much less commonly, MRSA is found
general community. There are three main reservoirs (and hence sources
and infection) for MRSA in hospital and institutions: staff, patients
inanimate objects such as beds, linen and utensils. By far the most
reservoir is patients who may be colonised with MRSA without evidence
infection. The usual sites of colonisation with MRSA are the nostrils,
groin, axilla, and wounds.
Most health professionals who
are colonised with MRSA do
not develop infection and many spontaneously clear the organism without
treatment. Once colonisation has been present for more than three
becomes much more difficult to clear.
Patients, however, have a
30-60% risk of infection
following colonisation. This is probably due to factors related to the
for which they are hospitalised, which impair their ability to clear or
colonisation with the organism.
Most MRSA infections occur in
wounds (e.g. surgical
wounds), skin (e.g. intravenous access sites), or in the bloodstream.
from these infections is not significantly different from those seen
type S.aureus infections.
and Management of
In hospitals, patients who
have been transferred from
another hospital or institution may have swabs taken on admission to
MRSA colonisation or infection. The swabs are taken from the nostrils,
groins, genital region and any areas of broken skin (e.g. surgical
New or transferring hospital
staff are also screened. The
results of swabs take a few days to be reported.
If an inpatient is found to
have MRSA colonisation or
- He or she should be
isolated from unnecessary contact with staff and other patients in a
single room, or share a room with other patients who have MRSA.
- Linen and clothing should
be carefully sterilised.
- Barrier precautions should
be taken by staff and visitors (gloves and gowns).
In order to limit spread of
MRSA throughout a ward or
hospital, such precautions should be strictly enforced until repeat
the patient are negative for MRSA. This may take some weeks. Staff
found to be
colonised with MRSA should be removed from patient contact.
Eradication treatment consists
- Topical application of an
antibiotic ointment such as mupirocin or fucidin to the nostrils, 2-3
times per day for 3-5 days.
- Antibacterial soaps.
The antibiotic of choice for
an infected impatient is
vancomycin given intravenously. Oral clindamycin
may be used in minor soft tissue infections in outpatients. These
are no better than flucloxacillin in the treatment of usual type S.aureus
but are much more effective in MRSA infections.
Less effective alternatives
In life-threatening infections
such as infective
endocarditis multiple antibiotics are often prescribed simultaneously
vancomycin plus an aminoglycoside plus rifampicin).
about MRSA in the
There is growing concern about
MRSA infections. They
appear to be increasing in frequency and displaying resistance to a
Of particular concern are the
VISA strains of MRSA (vancomycin
intermediate susceptibility S.aureus). These are
beginning to develop
resistance to vancomycin, which is currently the most effective
against MRSA. This new resistance has arisen because another species of
bacteria, called enterococci, relatively commonly express vancomycin
In the laboratory enterococci are capable of transferring the gene for
vancomycin resistance over to S.aureus.
New antibiotics such as
linezolid and synercid look
promising for treatment of infections not responding to vancomycin.
antibiotics are under development.
RESISTANT STAPHYLOCOCCUS AUREUS (MRSA)
does antibiotic resistance mean?
Germs called bacteria may cause infections. Antibiotics are drugs used
infections caused by bacteria. Sometimes these drugs will no longer
germs. This is called antibiotic drug resistance.
What is Staphylococcus aureus?
Staphylococcus aureus, or Staph aureus
for short, is a germ
(bacteria) usually found on a person's skin and mucous membranes. It
infections on broken skin or wounds. Methicillin is a type of
antibiotic used to
treat infections caused by Staph aureus. If Staph
resistant to Methicillin it is called MRSA. This means that the
infection may be
more difficult to treat. If someone has a MRSA infection there are
antibiotics that can be used.
What is infection vs.
An infection means that germs are in or on the body and make you sick
results in signs and symptoms such as fever, pus from a wound, a high
blood cell count]], or pneumonia. Germs can also be in the body, but
not make you
sick. This is called colonization. People who are colonized will have
or symptoms. They feel fine. MRSA can cause infection or colonization.
What are the risk factors for
Patients who have been in a hospital for a long time, sick with a long
illness, are on dialysis, or those who use IV drugs are at risk of
How do I know if I have MRSA?
Your doctor may order a test sample from your wound, blood, urine,
sputum to be sent to the lab. This test is called a culture. If there
is MRSA in
the sample, the culture is positive. This means you have MRSA in your
What will this mean for my
All patients who have a positive culture for MRSA are placed in
Isolation is used to keep from spreading MRSA to other patients. There
will be a
cart outside the room to hold supplies. A card will be placed on the
alert everyone to what precautions are needed to enter your room.
will wear gowns and gloves to care for you and will sometimes wear a
Visitors should report to the nurses station for directions on what to
enter your room. All of these steps are to keep germs from spreading to
Am I Contagious?
Contact with the infected/colonized part of the body is usually what
MRSA. You can distribute it to anything you touch if you do not clean
hands. Hands may be washed with soap and water for ten seconds or
an alcohol-based cleanser.
In some cases MRSA will go away for a time, but then it may come back.
reason, Hospital Epidemiology & Infection Control (HEIC) does
routinely discontinuing isolation.
What will happen when I go home?
At home, in most cases, you only need to use good handwashing. Healthy
members, who do not have large open wounds, skin diseases, or have diabetes,
not likely to get MRSA. Based on your discharge needs, instructions
given by the nursing staff.
will happen if I'm back in
the hospital or come to the clinic?
The Johns Hopkins Hospital wants to prevent the spread of MRSA. If you
into the hospital, you will be placed in isolation again. Cultures may
to see if MRSA is still present. When you go to the doctor's office or
hospital clinic appointments, you should tell the doctors and nurses
have MRSA, so they can take steps to avoid spreading it to others.
Will I ever get rid of MRSA?
Over time your normal skin organisms may take the place of MRSA. You
longer be isolated when cultures are negative for MRSA.
can I get more information about
- Talk to your doctor or
- Call The Johns Hopkins
Hospital: Hospital Epidemiology/ Infection Control Department, (410)
- Contact JHH at http://www.hopkins-heic.org
- Look at the Centers for
Disease Control and Prevention (CDC) website http://www.cdc.gov
Developed by The
Johns Hopkins Hospital:
Hospital Epidemiology and Infection Control Department.
Infections Involving Methicillin-Resistant Staphylococcus
G. Bartlett, MD
Choosing Appropriate Therapy
mainstay antibiotic for treatment of infections caused by MRSA has been
vancomycin, a drug that was approved by the US Food
and Drug administration (FDA) in 1956 but not used extensively until
the last 20 years. The escalating use of
vancomycin is attributed to the increase in nosocomial
infections caused by MRSA from 2% in 1974 to more than 50% in
2000.[1,21] Vancomycin is used mainly to treat
patients with infections caused by MRSA, patients with infections
caused by gram-positive bacteria in whom beta-lactam antibiotics are
contraindicated, and patients with device- and catheter-associated
Vancomycin has established
efficacy and is currently recommended for endocarditic prophylaxis in
penicillin-allergic patients undergoing invasive genitourinary or
gastrointestinal procedures likely to result in transient bacteremia.
However, there are major concerns with the use of this drug. First,
rapid infusion with vancomycin is associated with histamine release
syndrome (red man syndrome), which usually can be corrected by slow
infusion. However, 3% to 4% of patients appear to have true
hypersensitivity reactions expressed as a maculopapular rash, and a
small percentage have reversible marrow suppression.[21,23]
Second, vancomycin is not available in an oral formulation for
treatment of systemic infection, so patients are exposed to the risks
and expenses of intravenous therapy. Third, some clinicians question
the potency of vancomycin in selected settings because of slow clinical
responses, clinical failures, and high rates of relapse.[24-28]
Finally, many clinicians are concerned about the clinical significance
of reduced susceptibility with VISA strains and the threat of
vancomycin-resistant S aureus (VRSA).[17,18,29-31]
Although the clinical significance of VISA is unclear,[16,29-31]
the emergence of this organism alarmed those concerned about
possibility of a vancomycin resistant strain. This became a reality in
2002, when the Centers for Disease Control and Prevention (CDC)
published reports of 2 patients with infections caused by VRSA.[17,32]
In both cases, the isolates contained the vanA gene
of vancomycin resistance, presumably by transfer from
vancomycin-resistant enterococci (VRE) at a co-infected site.
In April 2004, the CDC
reported on the third documented clinical isolate of VRSA, which was
obtained from a long-term care facility resident in New York.
On March 17, 2003, the isolate yielded S aureus,
and laboratory tests indicated that it was resistant to vancomycin.
Further testing revealed that the isolate contained both the mecA
and vanA genes; however, the CDC states that the
isolate appears unrelated epidemiologically to the 2 previously
identified VRSA isolates. Although the New York isolate contained the vanA
gene, the vancomycin MIC of the isolate appeared low when initially
tested by an automated method. Vancomycin resistance was revealed using
the broth microdilution reference method, a nonautomated testing
technique. The CDC concluded that additional VRSA infections might have
occurred but were undetected by laboratories using automated methods
and recommends that potential VRSA isolates should be saved for
confirmatory testing using nonautomated methods such as broth
microdilution, agar dilution, or agar-gradient diffusion. The patient
remains in a long-term care facility, and the New York State Department
of Health continues to investigate this case
In the past 5 years, the FDA
has approved 3 alternatives to vancomycin for treatment of infections
caused by MRSA: quinupristin-dalfopristin, linezolid, and daptomycin.
These agents have good in vitro activity against MRSA and most other
clinically important gram-positive bacterial pathogens. A general
comparison of these drugs is summarized in Table 3. In addition,
important advantages and disadvantages of these drugs include the
is the first agent in the streptogramin class. It is indicated for the
treatment of patients with serious or life-threatening infections
associated with vancomycin-resistant Enterococcus faecium
bacteremia and complicated skin and skin structure infections caused by
S aureus and S pyogenes.
Investigators conducted a randomized, open-label, controlled clinical
trial comparing quinupristin-dalfopristin 7.5 mg/kg q12h IV (n=221)
with cefazolin 1g q8h IV (n=222) in the treatment of complicated skin
and skin structure infections caused by suspected or confirmed MRSA.
One hundred thirteen patients (51%) and 120 patients (54%) in the
quinupristin-dalfopristin and cefazolin groups, respectively, were
found to be clinically evaluable. Of these patients, the success rate
was 66% in the quinupristin-dalfopristin group and 64% in the cefazolin
group. In another trial, quinupristin-dalfopristin 7.5 mg/kg q12h IV
(n=229) was compared with oxacillin 2 g q6h IV (n=221). Of the 105
patients (46%) in the quinupristin-dalfopristin arm and the 106
patients (48%) in the cefazolin arm who were found to be clinically
evaluable, the success rate was 50% for those taking
quinupristin-dalfopristin and 52% for those on cefazolin therapy. The
drug has a curious sensitivity profile, with activity against
vancomycin-resistant E faecium but not against Enterococcus
faecalis. Quinupristin-dalfopristin has been associated with
venous irritation, which can be avoided if the drug is infused through
a central line, and also with high rates of injection site reactions
and often debilitating myalgias.
is the first drug in the oxazolidinone class and is available in both
oral and parenteral formulations. The oral formulation is nearly 100%
bioavailable and is thus interchangeable with the parenteral
formulation. Linezolid is indicated in the
treatment of vancomycin-resistant E faecium
infections, nosocomial pneumonia caused by S aureus
(methicillin-susceptible and -resistant strains) of Streptococcus
pneumoniae (penicillin-resistant strains), complicated skin
and skin structure infections including diabetic foot infections
without concomitant osteomyelitis caused by S aureus, S
pyogenes, and S agalactiae, and community-acquired pneumonia
caused by S pneumoniae or S aureus.
In a randomized, multicenter, double-blind, double-dummy trial, 400
patients received linezolid 600 mg IV q12h followed by 600 mg PO q12h,
and 419 patients received oxacillin 2g IV q6h followed by dicloxacillin
500 mg PO q6h. Two hundred forty-five (61%) patients in the linezolid
arm and 242 patients (58%) in the oxacillin-dicloxacillin arm were
clinically evaluable. Cure rates were 90% in the linezolid group and
85% in the oxacillin-dicloxacillin group. The most common adverse
events are nausea, vomiting, diarrhea, and headache, and cases of
linezolid resistance have been reported.
is the most recent addition and represents a new class of antibiotics.
Clinical trials showed good results in skin and soft tissue infections.
Adult patients with clinically documented complicated skin and skin
structure infections were enrolled in 2 randomized, multinational,
multicenter, investigator-blinded studies. One study was conducted
primarily in the United States and South Africa, and the other was
conducted at non-US sites only. A total of 534 patients received
daptomycin 4 mg/kg IV q24h and 558 patients received the comparator
drug, which consisted of either vancomycin 1 g q12h or a semisynthetic
penicillin (ie, nafcillin, oxacillin, cloxacillin, flucloxacillin; 4-12
g IV per day). In the first study, clinical success rates in the
clinically evaluable population were 76% (158/208) in the daptomycin
group and 77% (158/206) in the comparator group. In the second study,
clinical success rates in the clinically evaluable population were 89%
(214/238) in patients taking daptomycin and 91% (226/250) in those
treated with comparator drugs. However, the failure rate of daptomycin
was excessive in a controlled trial for community-acquired pneumonia.
This observation is thought to be attributable to relatively poor
penetration into epithelial lining fluid in the lung. Some authorities
conclude that daptomycin may have a therapeutic niche with endocarditis
caused by MRSA or VRE because of results in an animal model.
The most common adverse events include gastrointestinal disorders,
general disorders (ie, injection site reactions, fever), and nervous
continue to debate the relevance of choosing a bactericidal over a
bacteriostatic agent for the treatment of infections. The first
publication dealing with the distinction of antimicrobial agents as
bactericidal or bacteriostatic is credited to Shah and colleagues
in the 1970s, and the implication is that bactericidal agents kill
microbes, whereas bacteriostatic agents simply inhibit growth. The
thesis is attractive for clinical use, based on the intuitive
conclusion that bactericidal activity is preferred. Nevertheless,
despite nearly 30 years of debate, no consensus exists regarding the
clinical utility of this distinction.
Bacteriostatic agents include
macrolides, tetracyclines, sulfonamides, clindamycin, linezolid, and
chloramphenicol. An antimicrobial agent is considered bacteriostatic
when the minimal bactericidal concentration (MBC)/MIC ratio is greater
than or equal to 16 for the pathogen isolated. When the MBC/MIC ratio
is less than or equal to 4, the agent is considered bactericidal. The
National Clinical Committee for Laboratory Standards (NCCLS) further
suggests that an agent is bactericidal when it causes greater than a
3-log (99.9%) reduction in colony-forming units (CFU)/mL after 18 to 24
hours of incubation in liquid media. To
insure an accurate estimation of approximately 99.9% killing, the
inoculum used to perform MBC analysis must be at least 5x105
CFU/mL in a volume of 0.01 mL.
Bactericidal agents include
beta-lactams, aminoglycosides, vancomycin, fluoroquinolones,
daptomycin, and metronidazole. The traditional definition of
bactericidal activity is based on in vitro activity showing the usual
99.9% (3-log) inhibition of growth. The typical method to testing this
in the laboratory has been the standard broth microdilution
susceptibility test to determine the MIC and MBC. After incubation for
18 to 24 hours, the wells that fail to show macroscopic growth are
subcultured to determine the MBC, which is usually identical to or
within 1 or 2 doubling dilutions of the MIC; if the MBC exceeds the MIC
by 32-fold or more, the microbe is defined as tolerant. The literature
on the clinical relevance of tolerant strains of S aureus
is extensive, but the data are difficult to interpret because of
variations in methods and definitions.[42,43]
Time-kill curve studies are
another method of determining the rate at which antibiotics kill
bacteria. These studies measure microbial killing as a function of time
and concentration and result in a definition of 4 different classes of
microbe-drug interaction. One concern,
however, is the feasibility of routine laboratory use of time-kill
curve studies because of the complexity of the testing, lack of
consensus regarding interpretation, and expense. Possible exceptions to
this concern are the use of the time-kill curve to study drug
interactions and to evaluate the synergy of penicillins and
aminoglycosides in the treatment of endocarditis caused by enterococci.
The serum bactericidal test (SBT), or the Schlichter test, which is a
modification of the broth dilution method, has been used for more than
40 years to determine bactericidal activity.
A potential advantage of this method is that serum from the infection
site, such as joint or cerebrospinal fluid, can be used to measure
bactericidal activity; however, this test rarely is used because of the
technical difficulties in standardizing and interpreting the test
aureus Disease in Three Communities
Scott K. Fridkin, M.D.,
Jeffrey C. Hageman, M.H.S.,
Melissa Morrison, M.P.H., Laurie Thomson Sanza, R.N., Kathryn
M.P.H., John A. Jernigan, M.D., Kathleen Harriman, Ph.D., Lee H.
Ruth Lynfield, M.D., Monica M. Farley, M.D., for the Active Bacterial
Surveillance Program of the Emerging Infections Program Network
aureus (MRSA) infection has emerged
in patients who do not have
the established risk factors. The national
burden and clinical effect
of this novel presentation of MRSA disease are
We evaluated MRSA infections in patients identified from
population-based surveillance in Baltimore and Atlanta and
hospital-laboratory–based sentinel surveillance of
12 hospitals in
Minnesota. Information was obtained by interviewing patients
reviewing their medical records. Infections were
community-acquired MRSA disease if no established risk
From 2001 through 2002, 1647 cases of community-acquired MRSA
infection were reported, representing between 8 and 20 percent
MRSA isolates. The annual disease incidence varied according
(25.7 cases per 100,000 population in Atlanta vs.
18.0 per 100,000 in
Baltimore) and was significantly higher among
persons less than two
years old than among those who were two years
of age or older
(relative risk, 1.51; 95 percent confidence interval,
1.19 to 1.92)
and among blacks than among whites in Atlanta
risk, 2.74; 95 percent confidence interval,
2.44 to 3.07). Six
percent of cases were invasive, and 77 percent
involved skin and soft
tissue. The infecting strain of MRSA was often
(73 percent) resistant
to prescribed antimicrobial agents. Among
patients with skin or
soft-tissue infections, therapy to which the
infecting strain was
resistant did not appear to be associated with
patient-reported outcomes. Overall, 23 percent
of patients were
hospitalized for the MRSA infection.
Community-associated MRSA infections are now a common
and serious problem. These infections usually involve the
among children, and hospitalization is common.
Division of Bacterial and Mycotic Diseases (S.K.F.)
and Division of Healthcare Quality Promotion (J.C.H., M.M., J.A.J.),
Center for Infectious Diseases, Centers for Disease Control and
Atlanta; Emory University School of Medicine and the Veterans Affairs
Center, Atlanta (M.M., J.A.J., M.M.F.); Johns Hopkins University
School of Public Health, Baltimore (L.T.S., L.H.H.); and the Minnesota
Department of Health, Minneapolis (K.C.-S., K.H., R.L.).
reprint requests to Dr. Fridkin at the CDC, NCID,
DBMD, MDB, MS C-09, 1600 Clifton Rd., NE, Atlanta, GA 30333, or at email@example.com.
Community-Associated MRSA —
Resistance and Virulence Converge
Laypeople and health care
professionals alike recognize Staphylococcus
aureus as an important cause of disease and
understand that antibiotic-resistant
strains pose a threat to the community. Before
the availability of
antibiotics, invasive staphylococcal disease
was often fatal, and the
introduction of penicillin in the 1940s
survival. Although penicillinase-producing strains
methicillin and other penicillinase-stable -lactam
agents filled the breach. However, methicillin-resistant strains
aureus (MRSA), which are resistant to the entire class
agents, were identified almost immediately and
are now found in
hospitals worldwide. Despite the growing prevalence
of MRSA in
hospitals, these strains . . .
Vancomycin-intermediate Staphylococcus aureus selected
during vancomycin therapy of experimental endocarditis are not detected
by culture-based diagnostic procedures and persist after treatment
Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.
ObjectivesLaboratory detection of vancomycin-intermediate Staphylococcus aureus (VISA)
and their heterogeneous VISA (hVISA) precursors is difficult. Thus, it
is possible that vancomycin failures against supposedly
vancomycin-susceptible S.aureus are
due to undiagnosed VISA or hVISA. We tested this hypothesis in
experimental endocarditis.MethodsRats with aortic valve infection due
to the vancomycin-susceptible (MIC 2 mg/L), methicillin-resistant S. aureus M1V2
were treated for 2 days with doses of vancomycin that mimicked the
pharmacokinetics seen in humans following intravenous administration of
1 g of the drug every 12 h. Half of the treated animals were killed 8 h
after treatment arrest and half 3 days thereafter. Population analyses
were done directly on vegetation homogenates or after one subculture in
drug-free medium to mimic standard diagnostic
procedures.ResultsVancomycin cured 14 of 26 animals (54%; P < 0.05
versus controls) after 2 days of treatment. When vegetation homogenates
were plated directly on vancomycin-containing plates, 6 of 13 rats
killed 8 h after treatment arrest had positive cultures, 1 of which
harboured hVISA. Likewise, 6 of 13 rats killed 3 days thereafter had
positive valve cultures, 5 of which harboured hVISA. However, one
subculture of vegetations in drug-free broth was enough to revert all
the hVISA phenotypes to the susceptible pattern of the parent. Thus,
vancomycin selected for hVISA during therapy of experimental
endocarditis due to vancomycin-susceptible S. aureus.
These hVISA were associated with vancomycin failure. The hVISA
phenotype persisted in vivo, even after vancomycin arrest, but was
missed in vitro after a single passage of the vegetation homogenate on
drug-free medium.ConclusionshVISA might escape detection in clinical
samples if they are subcultured before susceptibility tests.
Culture-based detection of methicillin-resistant Staphylococcus aureus by a network of European laboratories: an external quality assessment study.
, Lee A
, Derde L
, Kazma M
, Lammens C
, Ieven M
, Bonten M
, Carmeli Y
, Harbarth S
, Brun-Buisson C
, Goossens H
, Malhotra-Kumar S
; on behalf of the MOSAR WP2 Study Team
Department of Medical Microbiology, Vaccine & Infectious Disease Institute, Universiteit Antwerpen, Antwerp, Belgium.
hospital laboratories from Europe and Israel participated in an
external quality assessment (EQA) of the culture-based detection of methicillin-resistant Staphylococcus aureus (MRSA). Participants also reported the MRSA prevalence in clinical cultures and patient screening specimens, as well as the MRSA screening practices employed at their hospitals. An EQA panel of 18 samples consisting of two MRSA harbouring SCCmec IV and I, and one strain each of methicillin-resistantcoagulase-negative S. epidermidis, methicillin-sensitive S. aureus and
Escherichia coli as pure strains or in mixtures at 10(7)-1 cfu
absolute loads was analysed by the 23 participants. Seventeen (74%)
participants identified 17 or more samples correctly. Of these, 15
(88%) utilised a chromogenic medium alone (ChromID, bioMérieux; BBL
CHROMagar, BD Diagnostics; MRSA Select, Bio-Rad Laboratories) or combined with a conventional medium and up to three confirmatory tests. Proportions of MRSA among S. aureus isolated from clinical cultures varied widely, even among hospitals within countries, ranging from 11-20% to 61-70%. MRSA carriage rates were less variable (0-20%) between countries. Almost all participants (n = 22, 96%) screened patients for MRSA carriage
during 2009-2010, of which 15 (68%) screened intensive care unit (ICU)
patients alone or combined with other targeted high-risk groups, and 10
(45%) combined nasal screening with another body site.
- [PubMed - as supplied by publisher]
Methicillin Resistant Staphylococcus Aureus Infections
of Soft Issues of the Oral Cavity, Face and Neck in Patients
Hospitalized at the Cranio-maxillofacial Surgery Department. Apr 2011
Optimal dose of vancomycin for treating methicillin-resistant Staphylococcus aureus pneumonia in critically ill patients. Nov 2011
MRSA peritonitis secondary to perforation of sigmoid diverticulitis. Nov 2011http://www.ncbi.nlm.nih.gov/pubmed/22164818
The Epidemiology of Methicillin-Resistant Staphylococcus aureus (MRSA) in Germany. Nov 2011
A Report on The First Case of Vancomycin-Intermediate Staphylococcus aureus(VISA) in Hawai'i. Nov 2011
Staphylococcus aureus (MRSA) in nursing homes for older people. Dec 2011
Changing epidemiology of methicillin-resistant Staphylococcus aureus in the Veterans Affairs Healthcare System, 2002-2009. Dec 2011
PubMed MRSA Abstracts and Articles
Staphylococcus aureus (MRSA) infection
Staphylococcus aureus (MRSA) in rehabilitation and
chronic-care-facilities: what is the best strategy?
MRSA in Healthcare Settings
of Mulitdrug-Resistant Organisms in Healthcare Settings
departments should have had a
letter giving the following advice about MRSA coding.
has been a great deal of interest
in the incidence of MRSA in hospitals, but codes at present do not
MRSA from other types of staphylococcal infection. It has been decided
Scotland that we will use a 5th digit to
staphylococcal infections are MRSA or not, and when MRSA was
affected will be:
– Staphylococcal infection,
– Staphylococcus aureus as the
cause of diseases classified to other chapters
- Septicaemia due to
- Staphylococcal meningitis
- Sepsis of newborn due to
– Carrier of other specified
bacterial diseases (includes MRSA carrier and MRSA positive)
of these codes will be allocated 5th
digits as follows:
MRSA identified before admission to
MRSA identified after admission to
MRSA not known when identified
known whether MRSA
that the time identified refers to
the episode, so the 5th digit could change
between episodes in the
same hospital stay.
if MRSA infection has been
identified and coded, it is not necessary to add a code for MRSA
carrier or MRSA
9 Diagnostic Code
Infection with microorganisms resistant to penicillins
staphylococcus aureus (MRSA)
Lymphedema People Medical
Blogs and Pages:
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Staphylococcus Aureus - MRSA
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The time has come for families, parents, caregivers to have a support
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lymphedema. Sharing information on coping, diagnosis, treatment and
Sponsored by Lymphedema People.
No matter how you spell it, this is another very little understood and
frustrating conditions out there. This will be a support group for
suffering with lipedema/lipodema. A place for information, sharing
exploring treatment options and coping.
Come join, be a part of the family!
you are a man with lymphedema; a
man with a loved one with lymphedema who you are trying to help and
come join us and discover what it is to be the master instead of the
Support group for parents, patients, children who suffer from all forms
lymphangiectasia. This condition is caused by dilation of the
lymphatics. It can
affect the intestinal tract, lungs and other critical body areas.
Disorders Support Group @ Yahoo Groups===========================
While we have a number of support groups for lymphedema... there is
there for other lymphatic disorders. Because we have one of the most
comprehensive information sites on all lymphatic disorders, I thought
it is time that one be offered.
Information and support for rare and unusual disorders affecting the
system. Includes lymphangiomas, lymphatic malformations,
hennekam's syndrome, distichiasis, Figueroa
syndrome, ptosis syndrome, plus many more. Extensive database of
available through sister site Lymphedema People.
People New Wiki Pages
you seen our new “Wiki”
pages yet? Listed
below are just a
sample of the more than 140 pages now listed in our Wiki section. We
working on hundred more. Come
take a stroll!
are not for Lymphedema
People Online Support
and Pain Management
Lymphatic Drainage (MLD) and Complex Decongestive Therapy (CDT)
Associated with Lymphedema
to Treat a Lymphedema Wound
Infections Associated with
para-aortic lymph node dissection (EPLND)
Needle Biopsy - Fine Needle Aspiration
Page Updated: Dec. 15, 2011