A major outbreak of methicillin-resistant Staphylococcus aureus caused by a new phage-type (EMRSA-16)

Area of Science:

• Infectious Diseases
• Microbiology
• Epidemiology

Background:

• An epidemic of methicillin-resistant Staphylococcus aureus (MRSA) caused by a novel phage-type, EMRSA-16, occurred in East Northamptonshire hospitals between April 1991 and December 1992.
• The outbreak affected 400 patients, resulting in colonization or infection, and caused seven deaths, with chest infections being significantly associated with the EMRSA-16 strain.

Purpose of the Study:

• To describe the epidemiology and control of a novel MRSA outbreak (EMRSA-16) in a hospital setting.
• To evaluate the effectiveness of the 'search and destroy' strategy in containing the MRSA outbreak.

Main Methods:

• Implementation of a 'search and destroy' strategy including extensive screening of staff and patients, isolation of colonized/infected individuals, and treatment to eradicate carriage.
• Characterization of the outbreak strain (EMRSA-16) using phage-typing, antibiogram, and pulse field electrophoresis.
• Monitoring of MRSA spread within the hospitals and to neighboring regions.

Main Results:

• The EMRSA-16 strain spread to all but two wards despite initial control measures, highlighting challenges in containment.
• A high rate of throat colonization (51%) was observed, which was initially underestimated and contributed to delayed containment.
• The outbreak was eventually contained through isolation wards, eradication of carriage in patients and staff, and discharge screening.

Conclusions:

• Failure to promptly recognize the significance of throat colonization hindered early outbreak control.
• A comprehensive strategy involving isolation, eradication of carriage, and discharge screening was crucial for containing the EMRSA-16 outbreak.
• EMRSA-16 demonstrated significant epidemic potential, spreading regionally and possessing distinct microbiological characteristics.