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Salmonella enterica can lead to intestinal diarrhea, and the emergence and spread of cephalosporin-resistant Salmonella have brought great challenges to clinical treatment. Therefore, this study investigated the prevalence and transmission of bla CTX-M genes among S. Typhimurium from diarrhoeal outpatients in Guangdong, China, from 2010 to 2017. A total of 221 bla CTX-M-positive isolates were recovered from 1,263 S. Typhimurium isolates from the facal samples of diarrhoea patients in 45 general hospitals from 11 cities. The most popular CTX-M gene was bla CTX-M-55 (39.6%, 72/182) in the CTX-M-1 group, followed by bla CTX-M-14 (22.5%, 41/182) and bla CTX-M-65 (19.2%, 35/182) in the CTX-M-9 group. The isolates that carried bla CTX-M-9G had significantly higher resistance rates to multiple antibacterials compared with bla CTX-M-1G (p < 0.01). Meanwhile, PFGE analysis not only showed the clonal transmission of bla CTX-M-55/14/65-positve isolates of diarrhoeal outpatients' origins from different hospitals in Guangdong province, but also the characteristic of bla CTX-M-55/14/65-positve isolates' bacterial persistence. Multilocus sequence typing (MLST) analysis indicated that these S. Typhimurium isolates possessed ST34 and ST19. Furthermore, genomic Beast phylogenomic analysis provided the evidence of a close relationship of bla CTX-M-positive S. Typhimurium isolates between the outpatients and pork. Most bla CTX-M-55/14/65 genes were transmitted by non-typeable or IncI1/IncFII/IncHI2 plasmids with the size of ranging from ~80 to ~280 kb. Moreover, whole-genome sequencing (WGS) analysis further revealed that bla CTX-M-55/14/65 coexisted with other 25 types of ARGs, of which 11 ARGs were highly prevalent with the detection rates >50%, and it first reported the emergence of bla TEM-141 in S. Typhimurium. This study underscores the importance of surveillance for bla CTX-M-positive microbes in diarrhea patients. [ABSTRACT FROM AUTHOR]

We determined the prevalence and transmission characteristics of mcr-1 -positive Escherichia coli (MCRPEC) isolates from migratory birds Anser indicus in Guangdong, China. We identified 22 MCRPEC from 303 A. indicus fecal samples (7.3%) in Guangzhou, Zhaoqing, and Futian. The mcr-1 gene coexisted with 24 other types of antibiotic resistance genes (ARG), and 11 ARGs were highly prevalent at levels >50%. The MCRPEC displayed a diversity of sequence types (ST), and 19 distinct STs were identified with ST10, ST1146, and ST1147 as the most prevalent. In addition, these MCRPEC from birds were closely related phylogenetically to those from other sources in China. Whole-genome sequencing analysis demonstrated that mcr -1 was located on IncX4 (n =9, 40.9%), IncI2 (n =5, 22.7%) and IncP (n =1, 4.5%) plasmids and the latter shared an identical plasmid backbone with other sources. These results highlight the significance of migratory birds in the transmission of antibiotic resistance and provide powerful evidence that migratory birds are potential transmitters of antibiotic resistance. [ABSTRACT FROM AUTHOR]

Senecavirus A (SVA), formerly known as Seneca Valley virus (SVV), causes vesicular symptoms in adult pigs and acute death of neonatal piglets. This pathogen has emerged in major swine producing countries around the world and caused significant economic losses to the pig industry. Thus, it is necessary to develop strategies to prevent and control SVA infection. Herein, an SVA strain (named GD-ZYY02-2018) was isolated from a pig herd with vesicular symptoms in Guangdong province of China in 2018. The present study aimed to carry out the phylogenetic analysis of the GD-ZYY02-2018 strain, determine its pathogenicity in finishing pigs, and assess the protective efficacy of the inactivated GD-ZYY02-2018 strain against virus challenge. The results of phylogenetic analysis showed that the SVA GD-ZYY02-2018 strain belonged to the USA-like strains and had a close genetic relationship with recent Chinese SVA strains. Animal challenge experiment showed that 100-day-old pigs inoculated intranasally with SVA GD-ZYY02-2018 strain developed vesicular lesion, low fever, viremia, and virus shedding in feces. The immunization challenge experiment showed that pigs vaccinated with inactivated GD-ZYY02-2018 strain could produce a high titer of anti-SVA neutralizing antibody and no vesicular lesion, fever, viremia, and virus shedding in feces was observed in vaccinated pigs after challenge with GD-ZYY02-2018 strain, indicating that inactivated GD-ZYY02-2018 could protect finishing pigs against the challenge of homologous virus. In conclusion, preliminary results indicated that inactivated GD-ZYY02-2018 could be used as a candidate vaccine for in-depth research and might be conducive to the prevention and control of SVA infection. [ABSTRACT FROM AUTHOR]