Molecular epidemiology of methicillin-resistant Staphylococcus aureus in patients and their surrounding environment

Abstract

Background

Methicillin resistant Staphylococcus aureus (MRSA) is endemic in healthcare settings in many countries of the world. Patients who have acquired MRSA serve as a source of transmission by contamination of their surrounding environments. Numerous studies illustrate that many different inanimate surfaces in hospitals can become a reservoir for MRSA.

Objectives

The objective of this study is to examine the presence of MRSA on environmental surfaces and its relationship between patients’ acquisition of MRSA by studying their molecular characteristics.

Methodology

The near-patient surfaces of 30 MRSA positive patients, 30 control patients and the ward environments were sampled from June 2011 to September 2011. The swabs were enriched and cultured for the presence of MRSA. The MRSA isolates obtained from environmental samples and from the clinical samples of the patients were then characterized by Spa typing.

Results

The MRSA found in case patients and control patients’ environmental surfaces was 97% (29/30) and 40% (12/30) respectively. Environmental surfaces that were highly contaminated by MRSA positive patients were bed sheets (70%), followed by pillows (55%), patient bed frames (52%) and patient lockers (52%). On the environmental surfaces other than the near-patient areas, ambulatory chair armrests had the highest amount of MRSA (21%), followed by fax machines which accounted for 14%. Among the 216 MRSA isolates (30 clinical isolates and 151 environmental isolates), eight spa types were found and the most predominant spa type was t1081 (63.3%) followed by t032 (17.6%) and t037 (7.4%). 27 patients were found to have the MRSA isolates with same spa type in the clinical samples and their surrounding environments. The agreement between the MRSA isolated from the clinical sample of patients and their surrounding environment was 93.1%.

Conclusion

Identical isolates were recovered from the patient and their environment (93.1%) which suggests possible environmental contamination of the ward cubicles, possibly contributing to endemic MRSA. More effective and rigorous use of current approaches to cleaning and decontamination is required and consideration of newer technologies to eradicate MRSA.