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To disclose the antimicrobial susceptibility and wide adaptability of commonly occurring genotypes of Salmonella entericaserovar Typhimurium, the antimicrobial resistance and multilocus sequence typing (MLST) profiles of 196 SalmonellaTyphimurium isolates (136 from food-producing animals, 19 from environments, 15 from markets, and 26 from humans) in China between 2007 and 2019 were analyzed. Tests of susceptibility to 19 antimicrobial agents using the broth microdilution method showed that 84.7% of the isolates were resistant to at least one antimicrobial. Antimicrobial susceptibility analysis demonstrated that 66.8% of the isolates were multidrug-resistant (MDR) strains, with resistance to three or more antimicrobials. The highest antidrug resistance was to ampicillin, amoxicillin/clavulanic acid, and tetracycline. Three MLST types were detected, and sequence type (ST) 19 was the most common ST. However, ST34 was associated with a higher MDR rate and more complex MDR patterns, than ST19 and ST99, although the exact mechanism has not been reported. Our study highlights the variation of drug resistance and STs from different sources and the association between STs and drug resistance, providing useful information for epidemiological research and developing a public health strategy.

Salmonellosis occurs frequently worldwide, causing serious threats to public health. The abuse of antibiotics is increasing antibiotic resistance in bacteria, thereby making the prevention and control of Salmonellamore difficult. A phage can help control the spread of bacteria. In this study, the lytic phage S55, whose host bacterium is SalmonellaPullorum, was isolated from fecal samples obtained from poultry farms. This phage belongs to the Siphoviridaeand has a polyhedral head and a retraction-free tail. S55 lysed most cells of SalmonellaPullorum (58 of 60 strains, 96.67%) and SalmonellaEnteritidis (97 of 104 strains, 93.27%). One-step growth kinetics revealed that the latent period was 10 min, the burst period was 80 min, and the burst size was 40 PFU per cell. The optimal multiplicity of infection was 0.01, and the phage was able to survive at pH values of 4 to 11 and temperatures of 40 to 60°C for 60 min. Complete genome sequence analysis revealed that the S55 genome consists of 42,781 bp (50.28% GC content) and 58 open reading frames, including 25 frames with known or assumed functions without tRNA genes. S55 does not carry genes that encode virulence or resistance factors. At 4 and 25°C, S55 reduced the populations of SalmonellaPullorum and SalmonellaEnteritidis on chicken skin surfaces. S55 may be useful as a biological agent for the prevention and control of Salmonellainfections.

ABSTRACTCervical cancer is a leading cause of high mortality in women in developing countries and has a serious impact on women’s health. Human papilloma virus (HPV) prophylactic vaccines have been produced and may hold promise for reducing the incidence of cervical cancer. However, the limitations of current HPV vaccine strategies make the development of HPV therapeutic vaccines particularly important for the treatment of HPV related lesions. Our previous work has demonstrated that LM4Δhly::E7 was safe and effective in inducing antitumor effect by antigen-specific cellular immune responses and direct killing of tumor cell on a cervical cancer model. In this study, the codon usage effect of a novel Listeria-based cervical cancer vaccine LM4Δhly::E7-1, was evaluated for effects of codon-optimized E7 expression, cellular immune response and therapeutic efficacy in a tumor-bearing murine model. Our data demonstrated that up-regulated expression of E7 was strikingly elevated by codon usage optimization, and thus induced significantly higher Th1-biased immunity, lymphocyte proliferation, and strong specific CTL activity ex-vivo compared with LM4Δhly::E7-treated mice. Furthermore, LM4Δhly::E7-1 enhanced a remarkable therapeutic effect in establishing tumors. Taken together, our results suggest that codon usage optimization is an important consideration in constructing live bacterial-vectored vaccines and is required for promoting effective T cell responses.

An Escherichia colistrain isolated from the feces of swine at a pork slaughterhouse in Henan province China was found to possess two colistin-resistance genes, mcr-1and mcr-3, plus 16 additional resistance genes. Genes mcr-1.1and mcr-3.1were identified on IncHI2 and IncX1 type plasmids, respectively. Transconjugants (containing mcr-3, mcr-1&mcr-3) were obtained that were 64- and 512-fold higher than the minimum inhibitory concentration of colistin on the recipient bacteria (E. coliC600), respectively. The IncX1 plasmid containing mcr-3.1displayed a very specific structure compared with previous mcr-3. Variable and stable regions were similar across different plasmids, multiple insertion sequences and transposases.

Listeria monocytogenesis a deadly foodborne pathogen, and infections can result in meningoencephalitis and sepsis with mortality rates of up to 30%. In this study, we performed comparative whole-genome analysis of 30 clinical isolates sequenced together with 32 previously sequenced clinical and food isolates from China. The data indicate that L. monocytogenesisolates belonging to the clonal complexes (CC) −1, −8, −9, −87, −121, and −155 are present in human clinical cases. The majority of isolates are from CC-87, 9, and 8 and overlap with those CCs previously reported on the basis of multilocus sequence typing for isolates from Chinese food products. Detailed genome analysis of isolates, representative of CCs in clinical and food products, revealed strong similarities both in their core- and accessory genomes indicating that they are highly related. When compared to genome sequences of isolates of a given CC worldwide, clinical isolates of China were distinct and clustered in unified clades. Our data indicate that epidemic clones of L. monocytogenes(CC-87, 9, and 8) with unusually high occurrence of plasmids are unique to China and suggest that common populations of L. monocytogenesclones are present in both clinical and food products in China.

Listeria monocytogenesis a facultative, intracellular foodborne pathogen that causes listeriosis and is prevalent worldwide. However, our knowledge of this bacterium and the listeriosis it causes is still extremely limited until now. Therefore, this retrospective study of patients in mainland China over 10 years (2008–2017) was performed to better understand the demographic trends and clinical features of listeriosis in China. Both electronic and manual retrieval systems were used to collect the relevant literature on listeriosis in mainland China. A total of 759 cases were reported from 22 provinces. Among the clinical cases, septicemia was the most common presentation (49%), followed by central nervous system infection (25%). The overall case fatality rate was 18%, with a higher rate among neonatal patients (73%). In recent years, listeriosis has been reported annually and even peaked in 2014. The median age of nonperinatal cases was 36 years (range, 0–102), with a predominance of male cases (52%). Sporadic cases were frequent from March to May. Efforts to prevent and control the spread of listeriosis are required through further research and collaborative efforts to improve the capacities of clinical diagnosis and treatment.

Currently, there is no effective detection method for chicken interferon-γ (ChIFN-γ), therefore it is of great significance to develop a new, accurate and sensitive method for the rapid detection of ChIFN-γ to solve the problems which are directly impeding the in-depth research of immune regulatory factors and poultry immune responses, and which are preventing the analysis and evaluation of the immunity of poultry in diseases or after vaccination. This paper is the first report of a novel label-free electrochemical impedimetric immunosensor for the sensitive detection of ChIFN-γ, based on a 3E3monoclonal antibody against chicken interferon-γ (denoted as 3E3McAb) immobilized on a glassy carbon electrode modified with polythionine and gold nanoparticle self-assembled layers. The surface modification steps were characterized by scanning electron microscopy and electrochemical impedance spectroscopy (EIS). Detection was performed by measuring the relative change in impedance before and after the 3E3McAb–ChIFN-γ reaction by EIS. Under the optimized conditions, the relative change in impedance was proportional to the logarithmic value of ChIFN-γ concentrations in the range of 0.10 to 1.0 × 103ng mL−1(r= 0.9946) with a detection limit of 0.10 ng mL−1. Compared to the traditional method of enzyme-linked immunosorbent assay, the proposed method performed a low-cost, sensitive, quantitative detection of ChIFN-γ in real samples with satisfactory results, indicating that the developed immunoassay could be a promising alternative approach for the detection of ChIFN-γ.

SalmonellaEnteritidis (SE) are important zoonotic pathogens, and can be easily transferred to humans by contaminated animal products. Epidemic surveys of SE are necessary in current modern large-scale chicken farms. In this study, Salmonellastrains were isolated from possibly infected samples collected at 3 independent farms, and their serotype, drug resistances, virulence genes, and genetic similarity were analyzed by molecular genetic analysis technologies including multilocus sequence typing (MLST), clustered regularly interspaced short palindromic repeats (CRISPR), pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing (WGS). A total of 346 Salmonellastrains were isolated from 3,598 samples (9.61%); 329 isolates were identified as SE (95.09%) and 308 isolates were multidrug resistant (93.62%). Virulotyping based on 6 virulence genes showed high similarity in SE isolates of each farm, with the exception of 2 isolates. All SE isolates were found to be the same ST11 type by MLST, and 22 strains of 150 SE isolates selected at random were found to belong to 1 cluster by PFGE and the same SET1 type by CRISPR. WGS results further revealed that these isolates belonged to the same clonal cluster, with high genetic similarity of 99.80 to 100.00%. All these results indicated that these SE isolates were overwhelmingly dominant and demonstrated high genetic similarity, which revealed that the same SE clone might be transmitted in these farms.

Pullorum is a chicken-specific systemic disease caused by Salmonella entericaserovar Gallinarum biovar Pullorum (S. Pullorum). This study was carried out to provide basic data for understanding the trends of S.Pullorum. A total of 652 S.Pullorum isolates collected in China during 1962–2019 were examined. Overall, 525 (80.5%) isolates were resistant to at least one antibiotic; 280 (42.9%) isolates resisted 3 or more classes of antibiotics and showed an increasing trend until 2015 and then decreased significantly. The most common multidrug-resistant pattern was ampicillin–tetracycline–nalidixic acid (13.6%). After 2008, 6 classes of antibiotic-resistant strains began to appear, and they have been prevalent ever since. In 2014, a strain resistant to 7 antibiotics (ampicillin–cefazolin–streptomycin–tetracycline–sulphonamides–nalidixic acid–nitrofurantoin) was isolated. The highest antimicrobial resistance was observed for nalidixic acid (71.9%), and the lowest was found for cefotaxime, meropenem, amikacin, gentamicin, fosfomycin, and polymyxin (0%). Our findings monitored the prevalence of the resistance of S.Pullorum during the past half-century in China. Continued surveillance of antimicrobial resistance and the rational use of antimicrobials is necessary and important to control the rapid increase in antimicrobial resistance in S. Pullorum.