Objective: To determine the serotypes and drug resistance profiles of Shiga toxin-producing Escherichia coli (STEC) in animal stools from the Weishan area in Shandong Province, China. To provide the basis for further study. Methods: Five hundred animal stool samples (from pigs, cattle, sheep, dogs and birds) were collected from the Weishan area and STEC strains were isolated from these samples. Strains were serotyped by a serum agglutination test, and their drug resistance profiles were determined through antimicrobial sensitivity experiments. In this study, PCR was used to detect tetracycline resistance genes (tetA, tetB, tetC, tetD) and beta-lactam resistance genes (blaSHV-1, blaCTX-M, blaTEM). Results: Sixteen strains of STEC were isolated from animal stool samples. Thirteen strains were isolated from pig stool samples, two from bovine stool samples and one from a sheep stool sample. Two of the strains were identified as E. coli O157:H7, and other 14 strains were non-O157 STEC of different serotypes. Antimicrobial sensitivity experiments showed that 15 of the strains were multidrug resistant. The rates of resistance were as follows: nalidixic acid (12/16 strains), sulfisoxazole (11/16), trimethoprim and sulphame-thoxazole (11/16), doxycycline (9/16), azithromycin (9/16), tetracycline (9/16), chloramphenicol (8/16) and streptomycin (8/16). Therefore, nalidixic acid showed the highest rate of resistance among the strains, followed by trimethoprim and sulphame-thoxazole, and sulfisoxazole. Resistance to cefepime or imipenem was not detected. In total, three types of drug resistance genes (tetA, tetB and tetC) were detected among the 16 strains. Conclusion The results showed that STEC strains isolated from animals in the Weishan area were of a range of serotypes. The 16 strains of STEC isolated from animal stools in this area were resistant to a number of antibiotics, with many strains displaying multidrug resistance.

Objective: To understand the infection status, characteristics and drug resistance of non-O157 Shiga toxin-producing E. coli (STEC) in animal feces in Shandong Province. Methods: From 2015 to 2016, convient sampling method was used to collect 1 022 fresh feces of animals in Weishan county and Laizhou city, and 24 non-O157 STEC were isolated. The serotypes of non-O157 STEC strains were confirmed through serum agglutination test. The susceptibility was explored through the antimicrobial sensitivity experiments. ESBLs activity was confirmed by double-disc diffusion. PCR method was used to detect the resistance genes. PFGE typing was operated to assess the relatedness and variability of the strains. The multi-locus sequence typing (MLST) was adopted to get the allelic profile and ST sequence of strains. Analysis was made on the evolutionary relationship between different ST groups was made through CLC Sequence Viewer and Counting Express. Results: A total of 24 non-O157 STEC were isolated from animal feces. 23 strains were from pig feces, and 1 strain was from cow feces, and the serotypes were more dispersed. All of the 24 strains carried stx2 genes. The highest resistance rate was sulfamethoxazole(22 strains), the mount of cotrimoxazole and nalidixic acid was 18 strains, chloramphenicol was 13 strains, tetracycline was 19, and there was a phenomenon of multiple drug resistance. The drug resistance spectrum was sulfamethoxazole tetracycline-compound novammin-naphthidine-chloramphenicol. All strains were sensitive to cefepime and imipenem. The ESBLs confirmatory test showed that 4 strains of non O157 STEC produced beta lactamase. PCR detected 7 resistance genes, and 4 tetracycline resistance genes (Tet A, Tet B, tetC and tetD) were detected. The beta lactamase resistance genes (blaSHV-1, bla CTX-M, bla TEM) were all negative. 24 strains were divided into 15 PFGE types, and their clustering results were more dispersed and no dominant PFGE type. There were 11 kinds of MLST types, most of them are ST540 and ST5133 types, each of which was 4 strains, and clustered into 1 MLST genomes. Conclusion The serotypes of non-O157 STEC in animal feces O157 STEC were dispersed, and the resistant rate to common antibiotic was high. MLST typing results presents obvious polymorphism. Surveillance and manage ment of these strains should be strengthened.

Drugs targeting immune checkpoint are used for cancer treatment, but resistance to single drug may occur. Combination therapy blocking multiple checkpoints simultaneously can improve clinical outcome. Therefore, we designed a recombinant protein rPC to block multiple targets, which consists of extracellular domains of programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4). The coding sequence was inserted into expression vector and stably transfected into HEK293 cells. The culture supernatant was collected and rPC was affinity-purified. Real-time quantitative PCR was used to evaluate the expression levels of ligands for PD-1 and CTLA-4 in several human cancer cell lines. The binding of rPC with cancer cells was examined by immunofluorescence cell staining, the influence of rPC on cancer cell growth was assayed by CCK-8. The results showed that rPC could be expressed and secreted by stably transfected HEK293 cells, the purified rPC could bind to lung cancer NCI-H226 cells which have high levels of ligands for PD-1 and CTLA-4, no direct impact on cancer cell growth could be observed by rPC treatment. The recombinant protein rPC can be functionally assayed further for developing novel immunotherapeutic drugs for cancer.
Animals ; CTLA-4 Antigen ; genetics ; Cell Proliferation ; HEK293 Cells ; Humans ; Lung Neoplasms ; metabolism ; Programmed Cell Death 1 Receptor ; genetics ; Protein Binding ; Protein Domains ; genetics ; Recombinant Fusion Proteins ; genetics ; isolation & purification ; metabolism