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Ventilation grilles as a potential source of methicillin-resistant Staphylococcus aureus causing an outbreak in an
1Department of Microbiology, Leeds General Infirmary, UK.
Abstract:
The spread of methicillin-resistant Staphylococcus aureus (MRSA) in a hospital is thought to be mainly by direct contact. Environmental sources such as exhaust ducting systems have been increasingly recognized as a source for MRSA outbreaks in intensive therapy units. We describe an outbreak of MRSA related to ventilation grilles in an orthopaedic ward. Six patients and one nurse were involved in an outbreak with EMRSA-15 during March 1996. The index case was transferred from a large university hospital in Leeds. One of the patients had shared the same bay with the index case. The rest of the patients were in another bay of the same ward and had no direct contact with the index patient. An environmental source was suspected and the ventilation grilles in boys 1 and 2 were found to be harbouring EMRSA-15. The ventilation system at that time was working on an intermittent cycle from 4 p.m.-8 a.m. Daily shut-down of the system temporarily created a negative pressure, sucking air in from the ward environment into the ventilation system and probably contaminating the outlet grilles. It is likely that contaminated air was blown back into the ward when the ventilation system was started. The system was thoroughly cleaned, appropriate infection control measures were instituted and the ventilation system was put back on a continuous running cycle and the outbreak terminated. Six months after the outbreak no isolates of EMRSA-15 had been made on the ward.
Insights
Environmental contamination of ventilation grilles spread methicillin-resistant Staphylococcus aureus (MRSA) in a hospital outbreak. Cleaning the system and continuous operation stopped the MRSA transmission.
Area of Science:
- Infectious Diseases
- Hospital Epidemiology
- Environmental Microbiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) transmission in hospitals is primarily attributed to direct contact.
- Environmental reservoirs, including ventilation systems, are increasingly implicated in MRSA outbreaks, particularly in intensive care units.
- The role of ventilation systems in hospital-acquired infections requires further investigation.
Purpose of the Study:
- To investigate an outbreak of EMRSA-15 in an orthopaedic ward.
- To identify the source of MRSA transmission within the hospital environment.
- To evaluate the effectiveness of infection control measures targeting the ventilation system.
Main Methods:
- Case identification and epidemiological investigation of an EMRSA-15 outbreak involving six patients and one nurse.
- Environmental sampling of ventilation grilles to detect EMRSA-15.
- Analysis of the hospital ventilation system's operational cycle and its potential role in pathogen dissemination.
Main Results:
- EMRSA-15 was detected in the ventilation grilles of the affected orthopaedic ward.
- The intermittent operation of the ventilation system, creating negative pressure, likely led to the contamination of grilles.
- Subsequent cleaning of the ventilation system and continuous operation halted the outbreak, with no EMRSA-15 isolates found six months later.
Conclusions:
- Ventilation systems can serve as a significant environmental source for MRSA transmission in hospital settings.
- Thorough cleaning and modification of ventilation system operation are crucial for controlling MRSA outbreaks.
- Environmental hygiene and system maintenance are vital components of hospital infection control strategies.