Daofeng Qu

To evaluate the bacterial antibiotic resistance and the antibiotic resistance gene transmission characteristics in the monoculture and chicken-perch co-culture models of freshwater perch, we collected the sediment, water, fish, and chicken manure samples and isolated and identified 243 strains. Through the antimicrobial susceptibility test with the K-B method, PCR detection of antibiotic resistance genes and integrons, and conjugation and transfer experiments under antibiotic pressure, we systematically compared the antibiotic resistance characteristics and antibiotic resistance gene transmission mechanisms in the two models. The results showed that the resistance rates of the isolates to 11 antibiotics in the co-culture model were significantly higher than those in the monoculture model, and the antibiotic resistance of chicken manure was the most serious among all the samples. Moreover, the proportion of multi-drug resistant strains in the co-culture model was higher. Seventeen and 11 antibiotic resistance genes were detected in the co-culture and monoculture models, respectively. The detection rates of 11 antibiotic resistance genes in the co-culture model were significantly higher than those in the monoculture model. Integron analysis indicated that the detection rates of the three types of integrons in the co-culture model were all higher than those in the monoculture model. The co-occurrence network analysis revealed a co-occurrence relationship with quinolone and sulfonamide resistance genes. The conjugation transfer experiment confirmed that the transfer frequency of sul1 of the isolates in the co-culture model was higher than that in the monoculture model, and the sub-inhibitory concentration of sulfamethazine could increase the conjugation transfer frequency. To sum up, the chicken-perch co-culture has exacerbated the enrichment and spread of antibiotic resistance genes. It is suggested that special attention should be paid to the supervision of the co-culture model to reduce the risk of antibiotic resistance spread.

The combination of Lactobacillus reuteri and FOSs has shown a good synergistic effect on the regulation of fecal bacteria. Some bacteria are closely related to the production of SCFAs and gases, which may potentially affect physiological functions.

Multidrug-resistant (MDR) Enterobacteriaceae critically threaten duck farming and public health. The phenotypes, genotypes, and associated mobile genetic elements (MGEs) of MDR Enterobacteriaceae isolated from six duck farms in Zhejiang province, China, were investigated. A total of 215 isolates were identified as Escherichia coli (64.65%), Klebsiella pneumoniae (12.09%), Proteus mirabilis (10.23%), Salmonella (8.84%), and Enterobacter cloacae (4.19%). Meanwhile, all isolates were resistant to at least two antibiotics. Most isolates carried tet(A) (85.12%), bla_TEM (78.60%) and sul1 (67.44%) resistance genes. Gene co-occurrence analysis showed that the resistance genes were associated with IS26 and integrons. A conjugative IncFII plasmid pSDM004 containing all the above MGEs was detected in Proteus mirabilis isolate SDM004. This isolate was resistant to 18 antibiotics and carried the bla_NDM-5 gene. MGEs, especially plasmids, are the primary antibiotic resistance gene (ARG) transmission route in duck farms. These findings provide a theoretical basis for the rational use of antibiotics in farms which are substantial for evaluating public health and food safety.

Salmonella can cause severe foodborne diseases. This study investigated the prevalence of Salmonella spp. in fresh foods in Hangzhou market and their harborage of antibiotic resistance and virulence genes, antibiotic susceptibility, and pathogenicity. A total of 500 samples (pork, n = 140; chicken, n = 128; vegetable, n = 232) were collected over a one-year period. Salmonella was found in 4.2% (21) of samples with the detection rate in pork, chicken and vegetables as 4.3% (6), 6.3% (8), and 3% (7), respectively. One Salmonella strain was recovered from each positive sample. The isolates were identified as six serotypes, of which S. Enteritidis (n = 7) and S. Typhimurium (n = 6) were the most predominant serotypes. The majority of isolates showed resistance to tetracycline (85.7%) and/or ciprofloxacin (71.4%). Tetracycline resistance genes showed the highest prevalence (90.5%). The occurrence of resistance genes for β-lactams (bla_TEM-1, 66.7%; and bla_SHV, 9.5%) and aminoglycosides (aadA1, 47.6%; Aac(3)-Ia, 19%) was higher than sulfonamides (sul1, 42.9%) and quinolones (parC, 38.1%). The virulence gene fimA was detected in 57.1% of isolates. Gene co-occurrence analysis implied that resistance genes were associated with virulence genes. Furthermore, selected S. Typhimurium isolates (n = 4) carrying different resistance and virulence genes up-regulated the secretions of cytokines IL-6 and IL-8 by Caco-2 cells in different degrees, suggesting that virulence genes may play a role in inflammatory transcription. In in vivo virulence test, microbiological counts in mouse feces and tissues showed that all included S. Typhimurium were able to infect mice, with one strain showing significantly higher virulence than others. In conclusion, this study indicates Salmonella contamination in fresh foods in Hangzhou market poses a risk to public health and it should be closely monitored to prevent and control foodborne diseases.

Chewing ability has a strong effect on food digestion. However, little is known about the relationship between the food mastication degree and the subsequent gastric emptying. This study was to explore the effects of individual chewing ability (strong and weak) on the in vivo oral processing characteristics and in vitro dynamic gastrointestinal starch hydrolysis of three types of rice (japonica rice, indica rice and waxy rice). Results showed that the swallowable bolus in the weak chewing group had larger holes and a looser microstructure with more small rice particles, while the strong chewing ones obtained a bolus with higher saliva content (up to 28%) and starch hydrolysis degree (up to 13.55%). Moreover, the gastric retention and starch hydrolysis of the strong chewing ability group were higher in the artificial gastric dynamic system (AGDS). The indica rice particles with the higher degree of fragmentation contacted enzymes easier and hydrolyzed quicker, thus emptying through the stomach faster (81.76%). However, the oral chewing properties of rice mainly influenced the starch digestion in the stomach and the initial stage of the small intestine (∼5 min). This study suggested that the chewing ability and rice variety can influence the bolus properties, which in turn affected the gastric emptying and the degree of starch hydrolysis during digestion.

Introduction: This research aimed to investigate the antibiotic resistance of Enterococcus faecalis from swine farms in Zhejiang Province and the prevalence and transmission mechanism of oxazolidone resistance gene optrA.Method: A total of 226 Enterococcus faecalis were isolated and their resistance to 14 antibiotics was detected by broth microdilution. The resistance genes were detected by PCR.Results: The antibiotic resistance rate of 226 isolates to nearly 57% (8/14) of commonly used antibiotics was higher than 50%. The resistance rate of tiamulin was highest (98.23%), that of tilmicosin, erythromycin, tetracycline and florfenicol was higher than 80%, and that of oxazolidone antibiotic linezolid was 38.49%. The overall antibiotics resistance in Hangzhou, Quzhou and Jinhua was more serious than that in the coastal cities of Ningbo and Wenzhou. The result of PCR showed that optrA was the main oxazolidinone and phenicols resistance gene, with a detection rate of 71.68%, and optrA often coexisted with fexA in the isolates. Through multi-locus sequence typing, conjugation transfer, and replicon typing experiments, it was found that the horizontal transmission mediated by RepA_N plasmid was the main mechanism of optrA resistance gene transmission in E. faecalis from Zhejiang Province. Two conjugative multi-resistance plasmids carrying optrA, RepA_N plasmid pHZ318-optrA from Hangzhou and Rep3 plasmid from Ningbo, were sequenced and analyzed. pHZ318-optrA contain two multidrug resistance regions (MDR), which contributed to the MDR profile of the strains. optrA and fexA resistance genes coexisted in IS1216E-fexA-optrA-ferr-erm(A)-IS1216E complex transposon, and there was a partial sequence of Tn554 transposon downstream. However, pNB304-optrA only contain optrA, fexA and an insertion sequence ISVlu1. The presence of mobile genetic elements at the boundaries can possibly facilitate transfer among Enterococcus through inter-replicon gene transfer.Discussion: This study can provide theoretical basis for ensuring the quality and safety of food of animal origin, and provide scientific guidance for slowing down the development of multi-antibiotic resistant Enterococcus.