Short communicationTracing contamination of Methicillin-resistant Staphylococcus aureus (MRSA) into seafood marketing chain by staphylococcal protein A typing

•MRSA is not a resident flora of fish, its presence is due to post-harvest contamination.•Molecular source tracking revealed ice and water were the probable source for contamination.•Local spread of MRSA between fish landing centre and retail fish market was identified.•Spa typing is proposed as a molecular source tracing tool for contamination and spread in seafood marketing chain.

Methicillin resistant Staphylococcus aureus (MRSA) is not a resident flora of fish. Its presence is endorsed to post-harvest contamination viz., handlers, handling equipment and environment. Earlier investigation revealed the presence of MRSA in seafood sold in retail fish markets in Kerala, India. Further studies were conducted to understand and identify the source of contamination into seafood sold in the retail markets by a pilot study. Seventeen samples which includes seafood and fishery environment samples from a landing centre and a retail fish market were collected to identify the source of contamination of MRSA. The whole experiment was repeated with same sampling plan for validation of the procedure, a week later from the same landing centre to the point of sale at fish market. MRSA was isolated from 35.2% to 23.5% of samples during first and second visits respectively. spa typing of the MRSA isolates revealed that MRSA from the landing centre (t311 and t15669) were carried to the retail fish market. Ice and water were the probable source for contamination during handling at the landing centre. This is first study to trace the source of contamination of MRSA in seafood and fishery environment. It is imperative that spa typing can be implemented for studying the local spread of MRSA clones at specific geographical locations only after establishing its diversity. To better understand the complexity of local spread of MRSA and reproducibility of this experiment, studies has to be conducted in other landing centre and retail markets.