| Provi dencia spp.is a member of the Enterobacter iaceae family.In the ear ly days,people thought that P rovidencia was only a component of the normal f lor a of human and animal intestines.Only certain str ains could cause opportunistic inf ections under certain conditions,so they wer e ignor ed in testing and were often ignored.In recent years,with the continuous emergence of new case reports,the host range of P rovidencia inf ections has been continuous ly expanded,the disease causing disease has also shown divers ity,and the understanding of bacter ia of this genus has also undergone great changes.At present,P rovidencia has been descr ibed as an important pathogen that causes diarrhea and travel diarrhea in children in developing countr ies.It is als o an important pathogen that causes iatrogenic infections.It has attracted clinic al attention.Its host source,pathogenic mechanis m,P lasmid pr of ile and the transf er of drug res istance have become hot issues in the study of this bacter ia.Although Providencia heimbachae（P.heimbachae）has been isolated from humans,penguins,and cow fetuses,there is little information about the pathogenic ity and biological character istics of P.heimbachae.Dur ing the routine test f or diarrhea in weaned piglets,we found 8 str ains of P rovidencia,and selected two str ains of P.heimbachae 99101 and P.hei mbachae 92102 that were not co-infected were s elected for system biology char acter ization,whole genome sequencing,and virulence gene mining.Provi dencia spp.,a member of the Enterobact eriaceae family,was previous ly thought to be just a part of the normal f lor a of the human and animal intestines,and only cer tain strains could cause opportunistic infections under certain conditions,thus being ignor ed in testing.As new cases are reported,the host r ange of P rovidencia infection continues to expand and the pathogenic factors also show divers ity,the understanding of the genus bacter ia has changed greatly.Currently,Provi dencia has been descr ibed as an impor tant pathogen of childhood and travel diarrhoea in developing countr ies.In addition,it is also an important pathogen caus ing iatrogenic inf ection,and has attr acted c linic al attention.The host source,pathogenic mechanism,plasmid pr of ile and dr ug res istance transfer of P rovidencia have become research hotspots and P rovidencia heimbachae（P.hei mbachae）has been isolated from humans,penguins,and cow fetus es.However,little information is available on its pathogenic ity and biologic al pr operties.Ther efore,we s elected 2 of the 8 newly discovered P rovidencia strains,P.heimbacha 99101 and P.heimbacha 92102,which were not co-inf ected,for system biology char acter ization,whole genome sequenc ing and virulence gene mining.The main results are as follows:（1）P.heimbachae 99101（access ion number:CP 028384.1）and P.heimbachae 92102（accession number:MT974580）were pos itive for utilization of Malonate,no gas production from glucose,and non-f ermentation of D-mannitol,D-Galactose and L-Rhamnose show differ ent characteristics of biochemical reactions.（2）Both P.heimbachae 99101 and P.heimbachae 92102 can form biof ilms and have the ability to adhere and invade IPEC-J2 cells.（3）P.heimbachae 99101 and P.heimbachae 92102 ar e res istant to 21 out of 41 antibiotics in the drug susceptibility test.（4）P.heimbachae is highly pathogenic to mic e.All mice inoculated with 1.0×108 CF U of P.hei mbachae 99101 died;mic e were inoculated with 1.0×1010 CF U of P.heimbachae 92102 died.The r esults showed that the 120 h-LD50 of mic e injected intraper itoneally w it h P.heimbachae99101 was 2.3714×108 CF U,and the 120 h-LD50 of mice injected intr aper itoneally with P.heimbachae 92102 was 2.3714×109 CFU.（5）P.heimbachae 99101 can caus e severe diarrhea,poster ior paralys is and other symptoms in piglets,proving that it is a new pathogen causing weaning diarrhea in piglets.（6）It was confir med that P.heimbachae 99101 and P.heimbachae 92102 can grow at low temperature（4°C）.T he cold enr ic hment tr eatment of the s ample can increase the detection r ate of Provi dencia,s uggesting that the bacter ia may have public health s ignif icance and may be a new risk factor for refrigerated food safety.（7）P.heimbachae whole genome sequenc ing（de novo）was completed for the f irst P.hei mbacha 99101,with a total length of 4262828bp and a s ize of 231957 bp,is a circular chromosome and contains a circular plasmid.（8）In the genome-wide sequence analys is,a total of 286 virulence f actors,164 r es istance genes,17 f imbr iae chaperonin oper ons,47 genes involved in the coding of f lagell in,12 cell membr ane-related vir ulences and 18 common antigens of the Enterobacteria were predicted.In addition,there are typical T3SS and T6SS in P.heimbachae 99101.（9）Through gene mining and animal exper iments,it is pr eliminar ily deter mined that th e virulence f actor of P rovidencia caus ing poster ior par alys is in animals is the capsule,but the mechanism of action needs to be further study.Over all,the biologic al char acter istics of P.heimbachae were systematically studied in this study,and conf irming that P.heimbachae 99101 is a new pathogen caus ing diarr hea in piglets.Isolates of P.heimbachae wer e found to be able to gr ow at low temper atur es conditions,and the whole genome of P.heimbachae（de novo）was obtained for the f irst time.Mor eover,P.hei mbachae 99101 capsule was proved to cause poster ior par alys is in animals.Our f indings suggest that more attention should be paid to the monitor ing of drug r es istanc e of P.heimbachae and the diagnos is of poster ior paralys is caused by it,and it provid es a new dir ection for food supervision. |
