| Multi-resistant Organisms (MRO) |
|
Module 3: VICNISS online self guided surveillance education
To download this module and/or the associated multiple choice exercises as PDF files, click on Education Resources.
Module Menu
Overview
This module gives an overview of Multi-resistant Organisms (MROs) and MRO surveillance, including key prevention strategies.
Objectives
After you have completed this module you should be able to:
- Explain what a MRO is and why there is a need to conduct surveillance on MROs;
- Identify key MROs;
- Identify the main risk factors for acquiring a MRO;
- List the key preventative strategies for MROs; and
- Understand modes of transmission for key MROs.
Background
In Australia antimicrobial resistance is increasing in many pathogens and has occurred in both community and healthcare acquired infections.
Examples where this has occurred include Streptococcus pneumoniae, methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant
enterococci (VRE), and strains of Klebsiella and Escherichia coli with extended-spectrum beta lactamase resistance. Antibiotic use is one of the
pressures that increases resistance. Appropriate antibiotic use will delay the emergence of resistance.
MROs are costly in both financial and human terms. Issues linked with MROs include:
- Potential transmission throughout healthcare facilities;
- Serious infections;
- Vulnerability of already compromised patients to MROs;
- Increased infection-associated morbidity and mortality; and
- Increased costs of care as a result of prolonged hospital stay and the need for more expensive drugs.
MROs are a globally recognised problem in healthcare. This is reflected in the 2001, World Health Organisation’s development of a global
strategy for antibiotic resistance:
Defining MROs
A MRO can be defined as any organism that is resistant to a number of antimicrobial drugs, that is, the drug no longer kills the organism.
Organisms may develop resistance in a variety of ways. For example, they can mutate or acquire new genetic resistance material from other bacteria.
Often if a particular organism becomes resistant to a drug, it can pass on its resistance to other organisms. The more often a drug is used, the more
likely an organism is to develop a resistance to it.
Australia has a history of high antibiotic usage. This is a major concern as it is widely accepted that anti-microbial use is the main driving
factor in the emergence of MROs and may be due to:
- Overuse of anti-microbials;
- Misuse of anti-microbials (eg. prescribing for viruses, non-infected ulcers);
- Under use of anti-microbials (eg. incomplete treatment courses, lack of access, inadequate dosing); and
- Inappropriate prescribing (eg. prescribing of broad spectrum agents when narrow spectrum agents would be adequate).
The use of anti-microbial therapy outside of the healthcare field has also been found to have an impact on human health (eg. in food products).
Surveillance of MROs
Hospitals are a major focus for infections and the spread of highly resistant organisms due to the intensity of use of antimicrobials within
these facilities, the vulnerability of the patient population and the risk of cross transmission between staff and patients. Surveillance is one of
the key strategies to control the spread and emergence of MROs. Surveillance also provides a way of monitoring the effect of interventions.
Nationally collected surveillance data can be used to inform policy development, evaluate cost effectiveness of strategies and to benchmark
approaches to anti-microbial use. To date, there is no national surveillance system in Australia for collecting MRO data. In Victoria, hospital-acquired
MRO surveillance forms part of the VICNISS Type 2 surveillance program.
Two MROs, which have had a significant impact in the healthcare setting, are MRSA and VRE. Whilst they are
not generally more virulent than their antibiotic-sensitive counterparts, both have a high propensity to become endemic.
| WHAT IS MRSA? |
WHAT IS VRE? |
Background:
In Victoria, since the late 1970's MRSA strains have been identified as a major cause of hospital acquired infections and outbreaks.
It is estimated that MRSA accounts for approximately 30-50 percent of hospital acquired S. aureus strains isolated from normally
sterile sites.
|
Background:
VRE was first described Britain 1988 and soon after in USA and Europe. In Australia the first human clinical isolate of VRE was in
Victoria in 1994. VRE is a major nosocomial pathogen in USA (0.3% 1989 - 7.9% 1993).
|
Source:
Staphylococcus aureus is a Gram-positive bacterium commonly found on human skin and in the noses of healthy people. It can enter the body
causing infection. The infection may be minor or serious and sometimes fatal (blood or wound infections).
MRSA (methicillin or multi-resistant Staphylococcus aureus) is a strain of S. aureus that is resistant to a number of antimicrobial
drugs. These strains are responsible for many infections in hospitals. MRSA is resistant to all beta-lactam antibiotics such as
penicillins, (dicloxacillin, methicillin and flucloxacillin) and cephalosporins and may also be resistant to aminoglycosides,
erythromycin and quinolones.
|
Source:
Enterococci are bacteria normally found in the gastrointestinal tract but can also be found in the female urinary tract.
When exposed to antibiotics, drug resistant strains may survive and multiply resulting in overgrowth of drug resistant enterococci in
the bowel.
Vancomycin-resistant enterococci (VRE) are highly resistant Gram-positive bacterium. VRE are defined as either Enterococcus
faecium or Enterococcus faecalis that are resistant to vancomycin.
VRE is intrinsically resistant to a number of antibiotics and in the laboratory setting it has been demonstrated that it is
able to transfer its genetic material to other Gram + organisms such as MRSA. There is some concern about what might happen if
this does occur frequently in clinical settings leading to severe life threatening infections becoming unresponsive to available
antibiotics. There are very few effective therapeutic agents to treat MRSA infection that acquires resistance to vancomycin (VISA).
Transfer of VRE resistance to MRSA has recently been described in the clinical setting.
Types of VRE
There are 2 types of gene acquired resistance that is found in E. faecium and E. faecalis - VanA, VanB:
- VanA - high level resistance to vancomycin and teicoplanin
- VanB - moderate to high level resistance to vancomycin
|
Reservoir:
Colonised or infected patients are the major reservoir of MRSA in the healthcare setting. MRSA has been isolated from environmental
surfaces including floors, sinks and work areas, tourniquets used to aid blood drawing, and blood pressure cuffs.
Routine cleaning reduces the bacterial load and the risk of transmission. Only a few outbreak investigations have implicated the environment
in transmission of MRSA.
Colonisation:
Colonisation occurs when the staphylococcus bacteria are present on or in the body without causing illness. Approximately 25 to 30% of the
population has staphylococcal nasal colonisation. Colonisation may also occur in the axillae, perineum, wounds, gastrostomy and tracheostomy
sites and, in the urinary and respiratory tracts. One of the most common sites of MRSA colonisation in patients, health care employees, and
other carers, is the nose (anterior nares). While health care employees, and other carers, may become intermittently colonised with MRSA
(as they may with susceptible staphylococcus aureus), they rarely develop infections.
Colonisation may be transient or persistent and can last for years. Infection occurs when the staphylococcus bacteria cause
disease in the person.
|
Reservoir:
Enterococci may contaminate hands, wounds and the environment. Patients can be colonised or infected with VRE. Patients who are rectally
colonised with VRE are the major reservoir of VRE in the healthcare setting.
VRE has been isolated from contaminated surfaces and equipment (fomites) and in high-risk patient populations such as ICU, renal units,
transplant units and medical oncology and haematology units.
Colonisation:
Enterococci are part of the normal flora of the gastrointestinal tract and most infections with enterococci are attributable to the patient’s own flora. Detection of rectal colonisation is usually by a rectal swab. In Victoria the majority of VRE isolates have been
from colonised patients and of the VanB type.
A patient who is known to have VRE colonisation may be asymptomatic. Detection may be via a clinical specimen only. As a result of contact
screening further isolates may be detected by rectal swab.
Rectal colonisation generally precedes infection.
|
Pathogenicity:
MRSA is neither more infectious nor more virulent than methicillin susceptible staphylococcus aureus; it is just more difficult to
treat.
|
Pathogenicity:
VRE is a relatively benign pathogen that is neither more infectious nor more virulent than antimicrobial sensitive enterococci.
VRE is normally not overtly pathogenic but in patients with invasive devices, especially Intravascular devices, may cause disease.
|
Risk Factors:
Several factors have been identified as increasing the risk of MRSA colonisation and infection such as patients who have:
- multiple hospital admissions
- multiple invasive procedures
- a lengthy hospital stay
- multiple or broad spectrum antibiotics
- severe underlying disease
- insulin-dependent diabetes,
- dermatologic conditions
MRSA colonisation/infection also tends to affect those who are very old or very young. Young children tend to have higher colonisation
rates, probably because of their frequent contact with respiratory secretions.
Infections caused by MRSA in long-term care facilities (LTCFs) are uncommon.
|
Risk factors:
Some patients are at increased risk of VRE infection or colonisation such as those who:
- are in ICU or dialysis units
- are immunocompromised
- have a device insitu such as drains, catheters or implantables
- have a lengthy hospital stay
- have multiple or broad spectrum antibiotic use, especially vancomycin and third generation cephalosporins such as ceftriaxone
Treatment with vancomycin is a major risk factor for VRE acquisition.
There is believed to be a link between antibiotics used in animal husbandry (farming) and the emerging resistance or resistant
organisms in the community. Community acquisition of VRE may be contributed to by avoparcin use in animals. Most European Union (EU)
countries have virtually eradicated the use of antibiotics used as growth promoters in all animal livestock.
VRE occurs in LTCF’s in Victoria with up to 3% of residents colonised at any one time. However, local and overseas studies
indicate that infections caused by VRE and transmission of VRE, are uncommon in these settings.
|
Transmission:
MRSA is most often transmitted by direct or indirect contact with a person who has a discharging wound, a clinical infection of the
respiratory or urinary tract, or is colonised with the organism.
Hands of healthcare personnel appear to be the most likely mode of transmission of MRSA between patients and staff. Studies have
demonstrated that MRSA can be present on the hands of personnel after performing such activities as wound debridement, dressing changes,
tracheal suctioning and catheter care.
|
Transmission:
VRE may be acquired via two ways. Transmission via direct contact with the patient or, when the patient is rectally colonised with
enterococci that acquire resistance through selected antibiotic administration.
VRE can be transmitted on ‘fingers and fomites’. Direct contact may occur through contaminated hands of staff and other
contacts or by contact with contaminated inanimate objects such as blood pressure cuffs, tympanic thermometers and bench tops. VRE may
survive for several days in the environment.
In reported hospital outbreaks patient-to-patient transmission is common hence the need for strict Contact Precautions. VRE is not
airborne.
|
Surveillance:
Why do surveillance?
Many studies have demonstrated that implementation of surveillance cultures to identify colonised patients and use of Contact
Precautions for care of colonised patients to prevent contamination of healthcare workers have resulted in significant reductions in
the rates of both colonisation and infection of patients with MRSA.
Society for Healthcare Epidemiology Association (SHEA) guidelines recommend active surveillance cultures and Contact Precautions to
control the spread of significant antibiotic resistant organisms. SHEA also recommends periodic (eg. weekly) surveillance cultures for
patients remaining in hospital at high risk for carriage of MRSA.
Routine surveillance cultures have not been widely accepted in Australian hospital settings and would require considerable additional
resources to implement. Targeted surveillance has been introduced in some high-risk areas such as ICU with apparent benefit.
|
Surveillance:
Why do surveillance?
As asymptomatic carriage of VRE is common surveillance may be undertaken to try and determine the extent of VRE transmission during an
epidemic. Surveillance may also be recommended in the event that a patient has been in contact with VRE. A rectal swab is required to
detect carriage of VRE. Patients have the right to refuse VRE screening.
When VRE screening has been undertaken in an outbreak setting patient transfers to other beds within the hospital should be minimised
until a result is obtained. If transfer is necessary, it is a good idea to ensure that the receiving unit are aware that screening
results are pending.
NB. Before any screening program can commence the clear purpose of the screening program should be identified, endorsed and undertaken
in consultation with the infection control team. The impact of screening programs on laboratory resources should be considered.
|
Infection Control Measures
Infection Control measures aim to eliminate the source/reservoir of infection and to end the chain of transmission’ and can be targeted toward detection, prevention of transmission and control including one or all of the following interventions:
Standard Precautions
Standard Precautions should be practiced for every contact with every patient at all times to reduce the risk of transmission of microorganisms
from both recognised and unrecognised sources of infection within health services. Standard Precautions are recommended for the treatment and care
of all patients at all times regardless of their infectious status and includes the following measures:
- Good hygiene practices, particularly washing and drying hands before and after patient contact;
- The use of personal protective apparel such as gloves, gowns, plastic aprons, masks, eye shields or goggles;
- Appropriate handling and disposal of sharps and other contaminated or infectious waste;
- Use of aseptic techniques;
- Appropriate reprocessing of reusable equipment and instruments; and
- Environmental controls such as cleaning and spills.
Standard Precautions recognise that any body fluid may contain contagious microorganisms. Standard Precautions should be used when contact
with any of the following is anticipated:
- Blood.
- All other body fluids, secretions and excretions (excluding sweat), regardless of whether they contain visible blood.
- Non-intact skin.
- Mucous membranes.
Additional (Transmission Based) Precautions
Transmission-based precautions are work practices, which reduce the risk of the transmission of microorganisms within healthcare settings.
Additional precautions are used for patients known, or suspected, to be infected with epidemiologically important pathogens, spread by
airborne or droplet transmission or by direct or
indirect contact with skin or contaminated surfaces.
Contact precautions are work practices, which reduce the risk of
the transmission of organisms from contaminated environmental surfaces, or by direct or indirect contact with a patient during routine care.
The routine use of gloves, gowns, plastic aprons, stringent hand-washing techniques and the appropriate decontamination of patient care equipment
will reduce the risk of transmission of microorganisms. The decision to implement Contact Precautions in addition to Standard Precautions should
be based on the risk of transmission of the microorganism from the colonised or infected patient to others. Factors to consider include the site
and severity of infection the patient’s mental status, personal hygiene, the ability to contain wound drainage, and whether the patient who
is colonised in the respiratory tract has a cough, a tracheostomy or whether the patient has a desquamating skin disorder.
Contact transmission precautions can be divided into 2 groups direct-contact transmission and indirect-contact.
Direct Contact Transmission: involves direct body surface-to-surface contact and physical transfer of microorganisms
from an infected or colonised person to a susceptible host. This may occur between patient and carer during patient care that involves direct
personal contact, or between any two persons (patients, carers, others) in the health care setting.
Indirect Contact transmission: involves the contamination of an inanimate object (such as instruments or dressings)
by an infected or colonised person. The contaminated item or environment may then transmit the organism to a susceptible host via contact.
Droplet Precautions
Droplet precautions are work practices, which reduce the risk of droplet transmission of microorganisms. Droplets are generated from the source
person primarily during coughing, sneezing and talking and during procedures such as respiratory tract suctioning and bronchoscopy. Transmission
occurs when an infected or colonised person generates droplets containing microorganisms which are propelled a short distance (less than two metres)
through the air and deposited on the conjunctivae, nasal mucosa or mouth of a host.
Airborne Precautions
Airborne precautions are work practices, which reduce the risk of airborne transmission of microorganisms. Airborne transmission occurs by
dissemination of airborne droplet nuclei or small particle residue (5mm or smaller in size) of evaporated droplets containing microorganisms
that remain suspended in the air for long periods of time or dust particles containing the infectious agent. Microorganisms carried in this
manner can be disperse widely by air currents and may be inhaled by a susceptible host within the same room or over a longer distance from
the source patient, depending on environmental factors. Therefore, special air handling and ventilation systems within healthcare institutions
are required to prevent airborne transmission of infections such as Mycobacterium tuberculosis.
| What you can do to prevent transmission of MRSA |
What you can do to prevent transmission of VRE |
- Standard Precautions alone may be adequate for the patient who has nose or skin colonisation with MRSA, good hygiene, is continent
and is mentally alert.
- Contact Precautions are indicated for certain patients with MRSA in addition to Standard Precautions for example when the
patient has:
- infection/colonisation of an indwelling catheter
- heavily colonised wounds
- colonised/infected respiratory tract and copious sputum production or tracheostomy insitu
- a desquamating skin disorder
- Contact precautions may also be employed where a cluster of hospital-acquired MRSA infections is detected.
Source measures:
If the source of the MRSA cannot be contained, for example, excessive wound discharge, copious sputum production, tracheostomy,
incontinence or poor hygiene of patients who are colonised or infected with MRSA should be placed in a single-bed room. When a
single-bed room is not available, the patient may be placed in a room with other patient(s) who have the same micro-organism
(cohorting).
If a single-bed room is unavailable and cohorting is not possible, then the patient may be placed in a room with another patient.
The best room-mate for a patient with MRSA is a patient who:
- has intact skin·
- has no invasive devices (for example, nasogastric tubes, tracheostomy or tracheal tube, intravenous lines, urinary catheters)·
- is not significantly immunocompromised (for example, by neutropenia, corticosteroids or chemotherapy)·
- is not a preoperative patient
|
- Designate equipment for this patient/group of patients only eg. Blood pressure cuffs or ensure that shared patient care equipment
is appropriately disinfected before use on another patient.
- Additional precautions for VRE: A single room may be required or several patients with the same type of VRE may be cohorted.
Because VRE may contaminate hands, wounds and the environment, implementation of Standard Precautions is not sufficient.
Source measures:
- One to one nursing may also be indicated when a patient has:
- faecal incontinence/diarrhoea
- is on antibiotic therapy
- a poor level of hygiene
- a clinical infection with VRE eg. VRE bacteraemia
- Encourage good handwashing for patients as well as staff.
- Early identification of cases.
- Transmission based precautions.
- Restriction of patient bed movement, ie. transferring from one hospital bed to next.
- Environmental controls.
- Screen contacts of VRE positive patients where necessary.
|
Test your Knowledge - Exercise 1
Clicking the above link will take you to the Education Resources page where you can download a PDF version of the Exercises Questions and Answers
Test your Knowledge - Exercise 2
Clicking the above link will take you to the Education Resources page where you can download a PDF version of the Exercises Questions and Answers
Further Information
References
- Chambers HF. The Changing Epidemiology of Staphylococcus aureus. Emerg Infect Dis 7(2), 2001. © 2001 Centers for Disease Control and Prevention (CDC)
- CDC fact sheet: www.cdc.gov/ncidod/dhqp/ar_mrsa_ca_public.html
- Muto CA, Jernigan JA, Ostrowsky BE, Richet HM, Jarvis WR, Boyce JM, Farr BM. SHEA Guideline for preventing nosocomial transmission of multidrug resistant strains of Staphylococcus aureus and Enterococcus. ICHE 2003;24:362-386.