Introduction
The genus Chromobacterium , consisting of seven recognized species, is a Gram-negative, rod-shaped bacterium, in which the most famous specie is Chromobacterium violaceum with red pigment (Papapanagiotou & Aligizakis, 1959). Chromobacterium is mainly distributed in tropical and subtropical regions, and it is frequently isolated in water sources and humid areas (Blackburn et al., 2019). Chromobacterium haemolyticum was considered as a separate species, lacking violet pigmentation but demonstrating strong hemolysis on sheep blood agar. (Han, Han, & Segal, 2008). C .haemolyticum has been isolated in a variety of water environments, such as rice roots, lakes, rivers, and sewage effluent (Kanamori et al., 2020; Priya, Sulaiman, How, Yin, & Chan, 2018; Zhou et al., 2016). There is evidence that C . haemolyticum is mainly transmitted through water sources, and some reports suggest thatC . haemolyticum can cause pneumonia and sepsis in humans, and the patients in these cases have a history of wound exposure or contact with water sources, indicating that Chromobacterium haemolyticum maybe an opportunistic pathogen (Miki & Okada, 2014; Takenaka et al., 2015). There have also reports that diarrhea case was related to C . haemolyticum , but C .haemolyticum causing diarrhea or even death in other animals has not been reported (Tanpowpong, Charoenmuang, & Apiwattanakul, 2014).
Piglets diarrhea is a very severe disease that is very harmful to the breeding industry. The intestinal immunity of piglets is not fully developed, and many pathogens are susceptible to piglets at this stage, causing acute diarrhea, vomiting, dehydration, and death (Osek & Truszczynski, 1992; Wang, Vlasova, Kenney, & Saif, 2019). Diarrhea in piglets can be devastating to pig farms if the main pathogen cannot be identified and treated accordingly. Some farms use mountain springs or river water as water sources, and incomplete disinfection of water sources often leads to infection of some bacterial diseases. C .haemolyticum is usually detected in water sources. Although it is pathogenic, it has received less attention. It is necessary to conduct in-depth research on the biological characteristics and genetic characteristics of the bacteria.
This study found that unexplained diarrhea occurred in many piglet farms in south China. After excluded some regular pathogens, a novel type ofChromobacterium haemolyticum was found in the water source and fecal samples of piglets with diarrhea. Challenge piglets with isolate GDHYZ30 can cause the same diarrhea symptoms similar to that of the field cases. And the diarrhea of piglets had been controlled after changing the drinking water source, indicating that the GDHYZ30 strain is the agents that cause diarrhea and death in piglets.