Pig as a reservoir of CRISPR type TST4 <i>Salmonella enterica</i> serovar Typhimurium monophasic variant during 2009–2017 in China

CRISPR-based typing was performed to subtype isolates of <i>S.</i> Typhimurium and its monophasic variant <i>Salmonella</i> 4,[5],12:i:- from humans and animals between 2009 and 2017 in China. CRISPR typing classified all isolates into two lineages and four sub-lineages. All isolates from Lineage II and Lineage IB-1 were <i>Salmonella</i> Typhimurium. All of <i>Salmonella</i> 4,[5],12:i: – isolates were distributed in Lineage IA and Lineage IB-2, which all belonged to ST34 by MLST typing. Only Lineage IB-2 contained ST34 isolates from both <i>Salmonella</i> Typhimurium and <i>Salmonella</i> 4,[5],12:i:-. Among the isolates of ST34, TST4 was identified as the most common CRISPR type representing 86.5% of <i>Salmonella</i> 4,[5],12:i:- and 14.5 % of <i>Salmonella</i> Typhimurium mainly from pigs and humans. This study demonstrated that TST4-ST34 isolates were predominant in <i>Salmonella</i> 4,[5],12:i:-, and pig was the main reservoir for <i>Salmonella</i> 4,[5],12:i:- in China, which might have the potential to transmit to humans by pig production.