Mumbai, Nov 28 (IANS) Megastar Amitabh Bachchan has thanked Prime Minister Narendra Modi for acknowledging his contribution to 'Swachh Bharat Abhiyan' (Clean India Mission). Modi on Sunday shared an audio file on Twitter, where he is heard reciting a poem by Amitabh. "A special message from Amitabh Bachchan on Swachh Bharat," Modi tweeted. The 74-year-old actor re-tweeted to thank Modi. "My most gracious and respectful thanks to the honourable Prime Minister Mananiya Shri Narendra Modi-ji, for acknowledging my small contribution," Big B tweeted.