Molecular Analysis of Staphylococcus aureus Infections in Trinidad and Tobago

Aims: Previous studies regarding Staphylococcus aureus in Trinidad and Tobago have so far been conducted mainly on methicillin resistant S. aureus (MRSA) isolates. Few reports are available regarding S. aureus infections in the country. This study was therefore designed to determine the unique molecular epidemiology and characteristics of S. aureus infections both in the community and hospitals in the country.

Materials and Methods: During a 10 month period, 385 persons who had infections caused by S. aureus were reviewed. Standardized questionnaires were utilized to obtain demographic data of the infected individuals from three major tertiary hospitals; and 309 S. aureus isolates recovered from these individuals were analysed using conventional and molecular microbiological methods including DNA microarray and multi locus sequence typing (MLST).

Results: Skin and soft tissue infections (SSTI) were the most prevalent type of S. aureus infections, followed by blood stream, urogenital tract and respiratory tract infections. Results also revealed that surgical, paediatric and medical wards experienced most of the S. aureus infections in a hospital setting or environment. The most prevalent S. aureus clonal complex (CC) associated with infections was CC8, which were methicillin sensitive and also positive for the Panton-Valentine leukocidin (pvl) genes - (CC8-MSSA-PVL+). Generally, the pvl genes rate among the isolates was observed to be 47% while MRSA now stands at 13.6%. The most prevalent MRSA strains were ST239-MRSA III and ST8-MRSA IV (USA300).

Conclusions: There is a high diversity of S. aureus clonal complexes infections in the country and the pvlgenes which were considered rare are now highly prevalent. Methicillin resistance though slightly higher than previously reported does not represent a significant increase. We propose that surveillance efforts should continue to be directed to monitor S. aureus infections in hospitals in the country so as to detect and eliminate any possibility of its outbreak early in the country as currently practiced in other countries.