Case 4: Antimicrobial resistance and infection control

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    The 600-bed tertiary adult care hospital where you work has had 46 patients with Methicillin Resistant Staphylococcus aureus (MRSA) in the past two months. Cases have occurred on the General Surgical Floor and this is a significant increase from the previous two months. You have implemented appropriate procedures and the situation appears to be under control. However, now you are asked to deal with issues regarding transfer of patients within your own institution, to long-term care facilities and to other acute care facilities. In particular, the long-term care institutions are reluctant to accept patients because of concerns regarding increased work-load and spread of “infection” to other residents.
    Case Four Questions:
    1. What are the specific mechanisms of resistance in MRSA, vancomycin resistant enterococcus (VRE) and carbapenem resistance in Gram Negative Bacilli?

Mechanism of resistance in MRSA
Resistance to methacillin in S. aureus is due to an alternate penicillin binding protein being produced called PBP2a (Lautenbach, P.198). This alternative penicillin binding protein has a low affinity for beta-lactam antibiotics. As a result the bacteria continues to be able to generate stable peptidogycan structures (that forms it’s cell wall) in the presence of formerly inhibitory concentrations of beta-lactam antibiotics (Lautenbach, P.198).

The gene that encodes for this resistance is located on the staphlococcus chromosome cassette mec, SCCmec. Transfer of the SCCmec gene from strain to strain has been rare and worldwide spread has been greatly due to clonal expansion of a few strains.
There are community acquired strains – SCCmec type IV
Multidrug resistant strains – CA-MRSA USA 300

Mechanism of resistance of Vancomycin resistant enterococcus (VRE)

Resistance to vancomycin in Enterococccus strains is for the most part due to acquiring either vanA or vanB genes (Lautenbach, P.199). These genes hold the DNA blueprint for the creation of the enzyme used to produce the precursors of peptidoglycan which then have reduced binding affinity for glycopeptides resulting in a weakened bacterial cell structure (Lautenbach, P.199). Resistance genes are carried on easily transferrable plasmids shared between strains.

Mechanism in Carbapenem resistance in Gram Negative Bacilli is the ”
carbapenemase genes, located on transferable plasmids” (picnet CPO toolkit, p.4)
These mechanisms of resistance cause outer-membrane protein deficiencies, result in carbapemase production and impact the efflux pumps (Lautenbach, P.211).

As to specific mechanisms of this resistance, in P. aeruginosa, imipenem resistance results when the OprD outer membrane protein that was accessible to carbapenems is lost. With P. aeruginosa, some efflux mechanisms reduce susceptibility to meropenem and doripenem (Lautenbach, P.212).

Carbapenem resistance in K. pneumonia is due to production of KPC, broad spectrum beta-lactamases which confer resistance to beta-lactams, beta-lactam-beta-lactamase inhibitor combinations and carbapenems. The enzyme that encodes this resistance is located on an easily transmissible plasmid (Lautenbach, P.213).
2. What procedures would you have implemented immediately to control this outbreak?

  • All infected patients would be placed on contact isolation (glove and gown) until until lab results return with no detectable MRSA colonization (PICNET, 2013, p. 17).
  • ensure staff and patients are compliant with hand hygiene (Lautenbach, p. 200)
  • ensure proper disinfection protocols are being followed for equipment and environment
  • staff education about MRSA
  • Implement an MRSA monitoring program (Lautenbach, p. 200)
  • continue to monitor MRSA case reporting and infection rates
  • conduct active surveillance testing for MRSA colonization among patients on the general surgery floor
  • provide decolonization therapy to MRSA colonized patients in conjunction with active surveillance testing program (Lautenbach, p. 200)

3. How will you address the long-term care institutions concerns and what evidence do you have to support your suggestions/recommendations?

For patients being transferred from hospital to a long term care facility, the sending unit will provide ARO status in their transfer report to the receiving facility. The facility can then take steps to ensure proper infection control measures are in place if needed and that further treatment can be continued if needed. “Admission should not be denied or delayed by a RCF on the basis of colonization or infection with an ARO. If a resident is known to be colonized with an ARO, it should be included in their health history and documentation, as this information may guide antibiotic or other treatment choices and is required should they require admission to acute care” (picnet ARO toolkit, p. 13).

Screening should be done following this outbreak and prior to transfer for high risk patients or those who had close contact with an ARO patient and were potentially exposed to MRSA on the general surgery floor (picnet ARO toolkit, p. 14).

The receiving care facility would perform a transmission risk assessment
“Patients at increased risk of disseminating MRSA include:
individuals with colonized tracheostomy and uncontrolled respiratory secretions

individuals with respiratory infections

individuals with wound or stoma drainage that is not contained by a dressing or appliance

individuals with desquamating skin conditions (e.g. psoriasis, burn patients)

individuals who are cognitively impaired (unable to comply with instructions)

individuals who have poor hygiene and are non-compliant with instructions. ” (picnet ARO toolkit, p. 15).

The facility would use the transmission risk assessment to determine what precautions are necessary as they await the return of MRSA swab results.

For admission to long term care of MRSA colonized patients contact precautions should be implemented and this will help prevent transmission to other patients in the facility(picnet ARO toolkit, p. 16).

The following precautions should be followed:

“gloves upon entering the room or patients bed space for any contact with patient or their environment

gowns when providing care to patient or if skin or clothing may come in to contact with their environment

if possible, dedicate any equipment (e.g. blood pressure cuff, stethoscope) to that patient; otherwise, clean and disinfect with a hospital-grade disinfectant prior to using with another patient.

Gloves and gowns must be removed and hands cleaned upon leaving the room or patient’s bed space.

Routine practices recommend the use of a mask when caring for individuals who have a febrile

respiratory illness. As well, a small number of studies support the use of a fluid-resistant mask when

caring for a patient who has respiratory symptoms or a tracheostomy, and has MRSA identified in their sputum ” (picnet ARO toolkit, p. 17).
4. Your facility has decided that a hand hygiene program could be effective in decreasing MSRA. Briefly list and discuss key elements of a hand hygiene program.

Key elements of a hand hygiene program:

  1. System change: make it possible, easy and convenient – sinks and products such as alcohol based hand rub in reach
  2. Hand hygiene education: Knowledge of hand hygiene guidelines, transmissible diseases spread by lack of hand hygiene etc
  3. Promote/faciliate hand washing and skin care for healthcare worker’s hands
  4. Routine observation and feedback: Audits of hand hygiene practices and performance feedback
  5. Reminders in the workplace: posters at sinks, outside clinic rooms etc
  6. Improve institutional safety climate: involvement from individual and institutional levels, ensure adequate staffing, institutional rewards, empower patients to ask/remind staff and involve them to perform good hand hygiene themselves
  7. Combine several of the above factors(WHO, 2009, p96).

5. Currently there is controversy regarding whether infection prevention should primarily employ a “vertical” versus a “horizontal” approach to ARO management or a combination of both. Please state what your position is and why.

We are currently using a combination of both vertical and horizontal approaches to ARO management after noting the examples of both in the table in the Goldmann et al article

Vertical approaches reduce risk of infections due to specific pathogens:

  • Active surveillance testing to identify asymptomatic carriers
  • Contact precautions for patients colonized or infected with specific organisms
  • Decolonization of patients colonized or infected with specific organisms

Horizontal approaches reduce risk of a broad range of infections and are not pathogen specific:

  • Standard precautions (eg, hand hygiene)
  • Universal use of gloves or gloves and gowns
  • Universal decolonization (eg, chlorhexidine gluconate bathing)
  • Antimicrobial stewardship
  • Environmental cleaning and disinfection” (Goldmann et al, p798).

“applying other evidence-based, horizontal strategies such as universal decolonization in settings where benefits are likely to outweigh risks and costs; and …using AST and other vertical approaches selectively when epidemiologically important pathogens are newly emerging and rare to a given institution or region or to control out- breaks of specific pathogens.”(Goldmann et al, p798).


1. Lautenbach, E., Woeltje, K., and Malani, P. 2010. Practical HealthcareEpidemiology, 3rd ed.

2. World Health Organization. WHO guidelines on hand hygiene in health care. Geneva; 2009.

3. Goldmann, Donald A., Perl, Trish M., Septimus, Edward., Weinstein, Robert A., and Yokoe, Deborah S. (2014). Infection Control and Hospital Epidemiology.


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