Case of the Month

November 2016

Joy Cleghorn – Infection Prevention and Control Risk Manager Life Healthcare, Chairperson for the Infection Control Association of Southern Africa.

Juno Thomas – Clinical Microbiologist and Infectious Diseases Specialist, Consultant to Life Healthcare.


The setting is a hospital with an extremely low incidence of Methicillin Resistant Staphylococcus aureus (MRSA). Notably, there had been no MRSA cases identified in the neonatal intensive care unit (NICU) for eight months. The NICU has six open bays and two private (isolation) rooms.

During the first two weeks of July, all bays and private rooms were occupied. MRSA was identified simultaneously in two patients, from endotracheal aspirate and blood samples respectively. Both neonates had been in the NICU since birth, and were hospitalised for over a week. In both cases, the isolates were deemed to signify invasive disease and warranted antibiotic therapy.

During subsequent investigation, all other patients and nursing staff were screened for MRSA colonisation. One staff member and one patient were noted to be MRSA-positive. The staff member reported chronic intermittent eczema and had a few healing skin lesions on her forearms. The patient had no clinical evidence of infection, and was judged to be colonised. No other likely common exposure/source of MRSA transmission was identified.

Question 1: Is screening of patients and healthcare workers indicated in this scenario?

Answer to Question 1

Yes: two MRSA cases identified at the same time in a unit that has had no cases in the previous six months represents a possible cluster or outbreak and requires immediate investigation and implementation of control measures. This includes screening for MRSA colonisation of all other patients in a high-risk unit/area.

During an outbreak of MRSA, healthcare workers may be involved in transmission of MRSA to patients in two ways:
  • As the primary source of MRSA, when the healthcare worker has active MRSA infection or persistent colonisation
  • As a vector (secondary source) of transmission, by having transient MRSA colonisation (acquired from direct contact with an infected/colonised patient, or direct contact with the MRSA-contaminated environment) and transmitting MRSA between patients
With regards screening of healthcare workers:
  • any healthcare worker that reports the presence of skin lesions should be referred for MRSA-colonisation screening and dermatological treatment of the underlying cause.
  • consider screening healthcare workers that are possibly epidemiologically-linked to the cases (e.g. when transmission continues on a unit despite active control measures, or when epidemiological aspects of an outbreak are unusual).

Question 2 - How should screening for MRSA colonisation be performed?

Answer to Q2

It is well proven that no single anatomic site sampling will detect all MRSA-colonised persons, and sampling anterior nares alone has a highly variable sensitivity (48%-93%). Sampling from ≥1 additional anatomic sites (throat and/or perineum in studies on adults) increases the sensitivity to >90%.

Screening patients

The following anatomic sites should be sampled:
  • Adults and children: nasal swab (high nasal swabbing of anterior nares), groin or perineum swab, and throat swab
  • Neonates: nasal swab (high nasal swabbing of anterior nares), throat swab, and umbilical swab
Multiple swabs may be used for the above areas, and pooled into a single culture in order to manage costs. When multiple sample site swabs are pooled into a single culture, it isn’t possible to determine precisely which site was positive; however, it is of little concern since the decolonisation regimen is standard and not determined by specific site-positivity.
All patients with active skin lesions and wounds must have separate samples/swabs collected from such sites.

Additionally, consider exit-site swabs for patients with the following devices:
  • Tracheostomy (exit site)
  • Colostomy (exit site)
  • Percutaneous Endoscopic Gastrostomy (PEG)
Screening healthcare workers

Care is needed to distinguish between transient carriage (i.e. nasal carriage which is lost within a day or so of removal from contact with MRSA-positive patients and carries little risk of onward transmission) and prolonged carriage (especially that associated with skin lesions and throat colonisation). This is usually best achieved by screening staff as they come on duty at the beginning of their shift and not as they leave at the end of their shift. In an outbreak setting: nurses, doctors, physiotherapists, other allied health professionals and non-clinical support staff (e.g. porters) should be considered for screening. The special difficulties and risks posed by agency staff should be considered. There is no evidence to suggest that anatomic screening sites should be different from those sampled in patients for MRSA-colonisation screening, and it is recommended to collect a nasal swab (high nasal swabbing of anterior nares), groin or perineum swab, and throat swab.

Question 3 - What is the recommended decolonisation therapy regimen for MRSA-colonised persons?

Answer to Q3

MRSA decolonisation therapy refers to the administration of antimicrobial or antiseptic agents for the purpose of eradicating or suppressing the carrier state.

1. The standard decolonisation regimen consists of nasal and skin decolonisation performed simultaneously, as follows:

  • Nasal decolonisation: applying mupirocin 2% in a paraffin-base to the inner surface of each nostril (anterior nares) two to three times daily for five days. Apply a pea-sized amount to the inner surface of each nostril; the patient should be able to taste mupirocin at the back of the throat after application. Intranasal mupirocin therapy is safe for use in neonates.
  • Skin decolonisation: the patient should bathe daily for five days with 4% chlorhexidine body wash/shampoo. The skin should be moistened and the antiseptic detergent should be applied thoroughly to all areas before rinsing in the bath or shower. Special attention should be paid to known carriage sites such as the axilla, groin and perineal area. The antiseptic should also be used for all other washing procedures and for bed bathing. Hair should be washed with an antiseptic detergent. There are concerns regarding the use of chlorhexidine-containing products in children less than 2 months old, since they are at risk of skin irritation and systemic absorption following topical exposure; such events may be more likely in preterm infants. Generally, use of such products in this age group is not recommended; however, clinicians should carefully weigh the potential benefit in preventing MRSA related-outcomes in children less than 2 months old versus the risks of chlorhexidine exposure on a case-by-case basis.

After washing, use clean towels, sheets and clothing.

2. Throat carriage treatment in select cases

Treatment of throat carriage should only be considered in exceptional circumstances, e.g. when there is evidence that there is transmission from a throat carrier in a continuing outbreak or when the patient carrying MRSA in the throat has experienced episodes of invasive infection. Advice on choice of treatment and duration should be sought from a microbiologist or infectious diseases specialist.

Question 4 - What infection prevention and control practices should be instituted with regards managing the NICU patients with MRSA?

Answer to Q4

1. Isolation of MRSA-infected or MRSA-colonised patients
  • Place patients in a single/private/isolation room when available.
  • Cohorting of MRSA patients is acceptable when a single/private/isolation room is not available.
2. Contact precautions
  • Don gown and gloves on entry into the patient’s room/cohort area, and remove gown and gloves before exiting the room/cohort area.
3. Dedicated noncritical patient care items
Dedicate noncritical patient care items (e.g. blood pressure cuffs, stethoscopes) to a single patient known to be colonised/infected with MRSA. When equipment must be shared among patients, clean and disinfect the equipment between patients.

4. Cleaning and disinfection
  • Develop written protocols for daily and terminal cleaning and disinfection of patient rooms. Protocols should address the type of equipment or surface, persons responsible for performing the tasks, frequency, disinfectant product appropriate to the device or surface and required contact time to achieve effective disinfection.
  • Pay close attention to cleaning and disinfection of high-touch surfaces in patient care areas (e.g. bed rails, trolleys/carts, doorknobs, and tap handles).
  • Disinfect portable, reusable healthcare equipment after each use.
5. Educate patients’ visitors about MRSA: provide information about MRSA and contact precautions

6. Decolonisation therapy should be given. In this particular scenario where all MRSA-infected/colonised patients are neonates, intranasal mupirocin is indicated; however, given the concerns regarding the use of chlorhexidine-containing products in this age group, the clinician concerned must carefully weigh the potential benefit in preventing adverse MRSA related-outcomes versus the risks on a case-by-case basis.

Question 5 - How do you determine whether a healthcare worker is the source of MRSA transmission in an outbreak?

Answer to Q5
A critical component of MRSA outbreak investigation is being able to differentiate sporadic from epidemic (‘outbreak’) cases. Determining whether MRSA isolates are closely genetically-related (clonal) is important; if the isolates are clonal, they could have originated from the same source (therefore an outbreak), whilst if they aren’t it most likely reflects independent transmission events (therefore unrelated, sporadic cases and not an outbreak). Testing MRSA isolates for genetic relatedness (called genotyping) is not routinely or commonly done in South Africa, but certain reference laboratories in South Africa are able to do this.

In order to determine that a healthcare worker is the likely source of MRSA transmission in an outbreak setting, the healthcare worker’s MRSA isolate/s and all other MRSA isolates from colonised/infected patients must undergo genotyping, and the genotyping results must be interpreted by an expert together with the available epidemiological investigation findings.

Question 6 - What is the management of healthcare workers colonised with MRSA?

Answer to Q6

There are no controlled studies that examine the specific impact of isolated interventions on interrupting MRSA transmission from colonised healthcare workers to patients; therefore, there are unfortunately no evidence-based recommendations for the management of MRSA-colonised healthcare workers who have been associated with ongoing MRSA transmission to patients.

Interventions that may be considered include the following:
  1. Evaluate the MRSA-colonised healthcare worker’s infection prevention practices for opportunities for education and improvement.
  2. Ensure appropriate investigation for and treatment of active MRSA infection. In particular, skin infections and sinusitis have been associated with persistent MRSA colonisation in healthcare workers.
  3. Decolonisation therapy for healthcare workers with persistent MRSA colonisation – in particular those with skin lesions and throat carriage
  4. Work restrictions have been used as a part of outbreak management in some (but not all) scenarios where MRSA-colonised healthcare workers have been associated with transmission of MRSA to patients.
  5. Work restrictions include approaches such as leave, restriction from patient care activities, and temporary reassignment to low-risk tasks or units.
  6. Healthcare workers colonised with MRSA who work in a high-risk unit/area (e.g. ICU, NICU) generally represent a greater potential risk to patients than healthcare workers working in, for example, an outpatient department. Therefore, work restrictions may be more important for MRSA-colonised healthcare workers in high-risk unit/areas (e.g. NICU, ICU).
  7. Staff members with colonised/infected hand lesions should be off work while receiving antimicrobial and decolonisation therapy.
  8. It is recommended that a minimum of three screens at weekly intervals (while not receiving antimicrobial therapy) should be performed before a previously positive staff member can be considered to be clear of MRSA.

Infants in the NICU are at increased risk for infection and colonisation with MRSA, often resulting in poor outcomes and long-term sequelae. MRSA in the NICU may be acquired from colonised parents, healthcare workers, and other neonates. A substantial proportion of colonised patients will subsequently develop an MRSA infection (e.g. pneumonia, skin/soft tissue infection, primary bloodstream infection). Risk factors for MRSA colonisation include severe underlying illness or comorbid conditions, prolonged hospital stay, exposure to broad-spectrum antimicrobials, presence of invasive devices (such as central venous catheters), and frequent contact with healthcare workers. MRSA cases in the NICU need urgent assessment, rapid investigation, and timeous implementation of infection prevention and control measures in order to prevent outbreaks in this high-risk setting.


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