To investigate the mechanisms of biofilm (BF) formation in Salmonella pullorum (SP), a strong BF-forming strain designated 1904D10 was selected. Differential proteomics based on tandem mass tag (TMT) labeling was performed to compare the whole bacterial proteome between planktonic and biofilm states. A total of 219 differentially expressed proteins were identified (96 up-regulated, 123 down-regulated in biofilm state). Key up-regulated proteins included those involved in the EnvZ/OmpR two-component system (TCS), LuxS/AI-2 quorum sensing (QS) system, and AcrAB-TolC efflux pump. An ompR deletion mutant was constructed using Red homologous recombination. Deletion of ompR significantly reduced biofilm formation and significantly increased susceptibility to all tested antibiotics. Electrophoretic mobility shift assay (EMSA) demonstrated that OmpR protein directly binds to the promoter region of soxR (a transcriptional activator of AcrAB-TolC), but not to soxS. Molecular docking predicted a potential interaction between the AI-2 QS signaling molecule and EnvZ protein (binding energy: −23.99 kJ/mol), with hydrogen bonds forming at five amino acid residues. This study provides evidence that OmpR directly binds to the soxR promoter and that AI-2 potentially interacts with EnvZ. These findings offer new mechanistic insights specific to Salmonella pullorum-biofilm (SP-BF) regulation and provide potential targets for biofilm control strategies.

Understanding the antimicrobial resistance (AMR) mechanism of Salmonella pullorum (SP), which is widespread among yellow chickens in China, is crucial for reducing significant economic losses in the industry. In this study, we explored the AMR mechanism by which the LuxS/AI-2-mediated quorum sensing (QS) system regulates the AcrAB-TolC efflux pump in the SP. The results showed that the luxS gene and the signaling molecule AI-2 had no effect on the growth of the SP strains. However, the luxS gene knockout strain (SP129∆luxS) was sensitive to antimicrobials (ampicillin, methoxypyrimidine, sulfaisoxazole, trimethoprim/sulfamethoxazole and nalidixic acid), whereas SP129 was resistant. The SP129 strain was resistant to antimicrobials which had previously been proved to be sensitive to the antimicrobials following incubation with AI-2. Moreover, the expression levels of the soxS, acrA, and acrB genes, as well as the SoxS protein were significantly increased by knocking out the luxS gene or by incubating with Al-2. Crucially, there was no interaction between the LuxS protein and the SoxS or SoxR proteins. However, these two proteins were found to be bound to AI-2 via hydrogen bonds. In summary, AMR in SP isolates was enhanced by AI-2 through the promotion of the the expression of the soxS gene and the SoxS protein, activating the efflux pump. Exploring the AMR mechanism of the SP strain provides important baseline information for controlling outbreaks of yellow chicken salmonellosis.

The study explored the biofilm (BF) formation capacity, BF-related gene profiles, and the trends in antimicrobial resistance (AMR) of Salmonella pullorum (SP) strains over several years. A total of 627 SP strains were isolated from 4,540 samples collected from chicken farms in Guangxi, China during 2018–2022. The BF-forming capacity of these isolates was assessed using crystal violet staining, and the presence of eight BF-related genes ( csgA, csgB, csgD, ompR, bapA, pfs, luxS , and rpoS ) in BF formation-positive strains was determined through Polymerase Chain Reaction (PCR) analysis. Antimicrobial susceptibility test was conducted to investigate the AMR of the isolates. Minimum Inhibitory Concentration (MIC) and Minimal Biofilm Eradication Concentration (MBEC) of nine SP-BF strains were determined using the broth microdilution method to assess the impact of BF formation on AMR. Additionally, the Optimal Biofilm Formation Conditions (OBFC) were investigated. The results indicated that 36.8% (231/627) of the strains exhibited a positive BF-formation capacity. Among these, 24.7% (57/231) were strong BF producers, 23.4% (54/231) were moderate BF producers, and 51.9% (120/231) were weak BF producers. Analysis of the eight BF-related genes in SP-BF strains revealed that over 90% of them were positive for all the genes. Antimicrobial susceptibility test conducted on the isolates showed that 100% (231/231) of them exhibited resistance to at least one antibiotic, with 98.3% (227/231) demonstrating multidrug resistance (MDR). Both MIC and MBEC measurements indicated varying degrees of increased AMR after BF formation of the bacteria. The optimal conditions for BF formation were observed at 37°C after 48 h of incubation, with an initial bacterial concentration of 1.2 × 10 6 CFU/mL. Notably, NaCl had a significant inhibitory effect on BF formation, while glucose and Trypticase Soy Broth (TSB) positively influenced BF formation. The results of the study emphasized the need for effective preventive and control strategies to address the challenges posed by the BF formation and MDR of SP in the field.

[目的]克隆黄喉拟水龟(Mauremys mutica)Cathelicidin基因(MmCath)并分析其组织表达特征,为深入研究MmCath基因在黄喉拟水龟先天免疫中的潜在作用提供理论依据.[方法]运用RACE克隆黄喉拟水龟MmCath基因cDNA序列,利用生物信息学软件进行序列特征分析,并通过实时荧光定量PCR检测MmCath基因在黄喉拟水龟不同组织中的表达特征及细菌攻毒后的表达情况.[结果]MmCath基因cDNA序列全长777 bp,包括63 bp的5'非编码区、483 bp的开放阅读框(ORF)和231 bp的3'非编码区.MmCath基因编码160个氨基酸残基,包括N端的信号肽区,含有4个保守半胱氨酸(Cys)残基的Cathelin肽区和C端的成熟肽区,符合Cathelicidins蛋白家族典型特征.MmCath前体蛋白相对分子质量为17.74 kD,理论等电点(pI)为5.27,其二级结构中α-螺旋占31.25%,无规则卷曲占20.63%,β-折叠占48.12%.黄喉拟水龟MmCath前体蛋白氨基酸序列与西部锦龟(Chrysemys picta bellii)Cathelicidin氨基酸序列的相似性最高,达80.63%,亲缘关系最近.MmCath基因在黄喉拟水龟的表达具有组织差异性,以脾脏和肝脏中的相对表达量较高,在表皮、心脏、肾脏、肺脏、脑、肠道和肌肉等组织中的相对表达量较低;嗜水气单胞菌(Aeromonas hy-drophila)攻毒后MmCath基因表达上调,在攻毒后第3和第6h其相对表达量极显著高于攻毒前(0 h)的相对表达量(P<0.01,下同),之后有所下降,在攻毒后第36h再极显著上升,随后下降.[结论]从黄喉拟水龟中克隆的MmCath基因属于Cathelicidins基因家族,参与了黄喉拟水龟抗病原感染过程,可为有效控制黄喉拟水龟细菌性疾病提供新思路.

台湾泥鳅是稻鱼综合种养中常见的养鱼品种.为确定真菌杀虫剂金龟子绿僵菌CQMa421对台湾泥鳅的安全浓度,本研究进行金龟子绿僵菌CQMa421对台湾泥鳅的急性毒性试验.结果表明,金龟子绿僵菌CQMa421对台湾泥鳅的24 h半致死浓度(LC50)为93.79 mg/L,48、72 h和96 h的半致死浓度均为86.24 mg/L,金龟子绿僵菌CQMa421对台湾泥鳅的毒性可评价为低毒;安全浓度为21.87 mg/L,该安全浓度远高于金龟子绿僵菌CQMa421在水稻上施用的有效杀虫用量.本研究结果初步确定金龟子绿僵菌CQMa421在稻鳅综合种养中可以作为水稻生产的杀虫剂安全使用.

Salmonella is capable of harming human and animal health, and its multidrug resistance (MDR) has always been a public health problem. In addition, antibiotic-free or antibiotic-reduced policies have been implemented in poultry production. Therefore, the search for antibiotic alternatives is more urgent than ever before. The aim of this study was to assess the antibacterial activity of star anise-cinnamon essential oil (SCEO) in vitro and its prophylactic effect against the infections of Salmonella pullorum, Salmonella give, and Salmonella kentucky in vivo. The results demonstrated that SCEO is effective against Salmonella pullorum, Salmonella give, and Salmonella kentucky in vitro. Supplementation with SCEO could significantly decrease the infections of Salmonella pullorum and Salmonella give, whereas it could slightly but not significantly decrease the infection of Salmonella kentucky, while also significantly alleviating the body weight (BW) loss caused by the infections of Salmonella pullorum, Salmonella give, and Salmonella kentucky in Yellow chickens. The SCEO had the best prophylactic effect against the infection of Salmonella give in Yellow chickens, followed by the infection of Salmonella pullorum and the infection of Salmonella kentucky. The SCEO, used as an antibiotic alternative, could be an effective prevention strategy against the infections of Salmonella pullorum, Salmonella give, and Salmonella kentucky in Yellow chickens.

Salmonella is one of the major pathogenic bacteria causing foodborne diseases. The rapid detection of Salmonella in food is of great significance to food safety. In this study, the loop-mediated isothermal amplification (LAMP) method was developed, and primers were designed targeting the invA gene of Salmonella. Standard samples of recombinant invA-plasmid and 100 retail meat samples were tested by LAMP and compared with the results tested by conventional PCR and the routine Chinese National Food Safety Standard-Microbiological Examination of Food-Examination of Salmonella, respectively. The results showed that Salmonella strains of eight different serotypes were amplified successfully by the developed LAMP assay, and it was 1,000-fold more sensitive than conventional PCR, with the analytical sensitivity of 8 3 102 copies per mu L of the standard sample of invAplasmid. The results were visualized directly by adding calcein and MnCl2 in the LAMP reaction tube, and the positively amplified products turned green after an incubation of 2 min. In parallel detection, the positive rate of Salmonella by the LAMP assay was highly correlated with the routine Chinese national standard method. The results of the study demonstrated that the developed LAMP assay is a simple, rapid, strongly specific, highly sensitive, and visual detection method for Salmonella.

为探索引起广西某蛋鸡场的鸡只在产蛋前出现关节肿胀、跛行、不愿走动、卧地不起等症状的病因,本试验对该发病鸡群进行病原的分离鉴定、16S rRNA基因序列分析、分离株药物敏感性试验,对滑液囊支原体阳性样品进行vlhA基因序列测定、系统进化树分析.结果显示,病变主要发生在跗关节,可见关节腔内有黄色干酪样物及脓液;从病变关节处分离到葡萄球菌,经鉴定其为金黄色葡萄球菌;滑液囊支原体检测为阳性,其与参考株的vlhA基因核苷酸相似性为94％～98％,与疫苗株CP21129遗传距离远,不属于同一个分支.结果表明该鸡群发病原因为滑液囊支原体和葡萄球菌混合感染引起.

为了探讨三种细菌混合灭活疫苗对黄颡鱼的免疫保护作用,在防病上提供理论依据,将分离自患病黄颡鱼的温和气单胞菌、恶臭假单胞菌和类志贺邻单胞菌3种细菌浓度均调至约5×108 CFU/mL,按1:1:1的比例混合均匀成混合细菌悬液,然后制成福尔马林混合灭活疫苗,对黄颡鱼(体重约14.1g±1.2g)进行免疫保护试验,分别在免疫注射后7d、14d和28d进行3种细菌混合活菌的人工感染试验,以检测混合灭活疫苗的保护率.试验结果,使用0.5％福尔马林在25℃条件下灭活菌液24h可达到完全灭活要求,在人工感染后的第1d～3d为各试验组和对照组黄颡鱼的死亡高峰期,在免疫注射的7d、14d和28d后,混合灭活疫苗的免疫保护率依次为64.2％、92.4％和89.0％.表明本试验的3种细菌混合灭活疫苗对黄颡鱼具有一定的保护作用,在免疫注射14d后保护率达到最高.

Salmonella is a major foodborne pathogen that causes a broad range of infection in humans and animals. This research was undertaken to investigate the antimicrobial resistance, virulence genes and genotyping of the extended-spectrum beta-lactamase (ESBL)-producing Salmonella London (S. London) isolates originating from human patients, retail meats and chickens in southern China. The high antimicrobial resistance rates to trimethoprim/sulfamethoxazole (100%), methoxypyrimidine (100%), sulfaisoxazole (100%), ampicillin (73.68%) and amoxicillin (63.16%) were observed among a total of 19 S. London isolates, and the particular concern is that all isolates exhibited multidrug resistance (MDR). The ESBL-positive phenotype, which is resistant to antibiotics such as ampicillin, ceftazidime and cefotaxime, was observed in the isolates (15/19). These strains harbor the emerging ESBL-coding genes blaSHV, blaTEM-1, blaCTX-M and blaOXA, and co-harbor the virulence genes stn, invA, sseL and virK. In addition, the predominant genotypic virulence profile was characterized by the presence of stn, fimA, virK, invA, sseL, mgtC, siiE and sopB genes in the strains. The profiles of enterobacterial repetitive intergenic consensus (ERIC)-PCR revealed that S. London isolates with genetic diversity were widely disseminated. This study highlights the potential threat to public health posed by the foodborne transmission of the multidrug-resistant S. London isolates from diverse sources.

Background: Ammonia is one of the most common toxicological environment factors affecting shrimp health. Although ammonia tolerance in shrimp is closely related to successful industrial production, few genetic studies of this trait are available. Results: In this study, we constructed a high-density genetic map of the Pacific white shrimp ( Litopenaeus vannamei ) using specific length amplified fragment sequencing (SLAF-seq). The constructed genetic map contained 17,338 polymorphic markers spanning 44 linkage groups, with a total distance of 6,360.12 centimorgans (cM) and an average distance of 0.37 cM. Using this genetic map, we identified a quantitative trait locus (QTL) that explained 7.41–8.46% of the phenotypic variance in L. vannamei survival time under acute ammonia stress. We then sequenced the transcriptomes of the most ammonia-tolerant and the most ammonia-sensitive individuals from each of four genetically distinct L. vannamei families. We found that 7546 genes were differentially expressed between the ammonia-tolerant and ammonia-sensitive individuals. Using QTL analysis and the transcriptomes, we identified one candidate gene (annotated as an ATP synthase g subunit) associated with ammonia tolerance. Conclusions: In this study, we constructed a high-density genetic map of L. vannamei and identified a QTL for ammonia tolerance. By combining QTL and transcriptome analyses, we identified a candidate gene associated with ammonia tolerance. Our work provides the basis for future genetic studies focused on molecular marker-assisted selective breeding.

Nitrite is a major environmental toxin in aquaculture systems that disrupts multiple physiological functions in aquatic animals. Although nitrite tolerance in shrimp is closely related to successful industrial production, few genetic studies of this trait are available. In this study, we constructed a high-density genetic map of Litopenaeus vannamei with 17,242 single nucleotide polymorphism markers spanning 6,828.06 centimorgans (cM), with an average distance of 0.4 cM between adjacent markers on 44 linkage groups (LGs). Using this genetic map, we identified two markers associated with nitrite tolerance. We then sequenced the transcriptomes of the most nitrite-tolerant and nitrite-sensitive individuals from each of four genetically distinct L. vannamei families (LV-I–4). We found 2,002, 1,983, 1,954, and 1,867 differentially expressed genes in families LV-1, LV-2, LV-3, and LV-4, respectively. By integrating QTL and transcriptomics analyses, we identified a candidate gene associated with nitrite tolerance. This gene was annotated as solute carrier family 26 member 6 (SLC26A6). RNA interference (RNAi) analysis demonstrated that SLC26A6 was critical for nitrite tolerance in L. vannamei. The present study increases our understanding of the molecular mechanisms underlying nitrite tolerance in shrimp and provides a basis for molecular-marker-assisted shrimp breeding.

A selected yeast fraction (SYF) was tested for the purpose of preventing pullorum disease and fowl typhoid in breeder chickens. In a challenge-protection experiment, commercial Three-Yellow breeder chicks were initially divided into groups A, B (challenged, treated), C (challenged, untreated), and D (unchallenged, untreated). The group A diet was supplemented with SYF and group B was supplemented with Acidipure via drinking water. At 7 D, birds of groups A, B, and C were divided into 2 equal subgroups (A1-A2, B1-B2, and C1-C2). Subgroups A1, B1, and C1 were challenged with Salmonella pullorum (SP), while subgroups A2, B2, and C2 were challenged with Salmonella gallinarum (SG). Clinical signs and mortality were recorded daily. At intervals, antibodies against SP and SG were detected by a plate agglutinate test (PAT). At 42 D, all birds were weighed and necropsied, lesions were recorded and challenge pathogens were isolated. Results showed that SP and SG isolation positive rates of groups A1-A2 were significantly lower (P < 0.05) than those of B1-B2 and C1-C2, respectively. The average body weight (BW) of groups A1-A2 was significantly higher (P < 0.05) than that of B1-B2 and C1-C2, respectively. In the field trial, chicks were randomly divided into 3 groups. Group 1 birds were fed a diet supplemented with SYF, group 2 diet was supplemented with Acidipure via drinking water, and group 3 was fed the same but un-supplemented diet as the control group. Antibodies against SP and SG were detected by PAT at 120 D. The antibodies positive rate of group 1 was significantly lower (P < 0.05) than those of groups 2 and 3, while no significant difference (P > 0.05) was found between groups 2 and 3. The results demonstrated that SYF supplementation could significantly decrease SP and SG infection rates, improve the BW of birds challenged with SP and SG, and was more effective than Acidipure via drinking water.

采用PCR技术检测分离自广西钦州、北海和防城港3市凡纳滨对虾样品中的67株副溶血弧菌(Vib-rio parahaemolyticus)3种毒力基因 tdh、trh和tlh的携带情况,并将 tlh基因进行原核表达,SDS -PAGE和Western blotting鉴定分析.结果显示,67株副溶血弧菌均未扩增出 tdh和 trh基因,而 tlh基因检出率为100 .0%,所检副溶血弧菌的毒力基因型为 tdh- trh- tlh+.成功构建了原核表达质粒pET -28a-tlh ,将其转化至大肠杆菌BL21 (DE3)感受态细胞后,经IPTG诱导表达,SDS -PAGE电泳检测得到大小约为53 kDa的产物,与预测值相符.经Western blotting鉴定,该重组表达产物能与抗6× His标签的单克隆抗体发生特异性反应.

Salmonella, one of the most important foodborne pathogens, can be the cause of bacterial food-borne illness and is commonly associated with the consumption of retail meat. Multidrug-resistant Salmonella isolates with high adaptability, have been responsible for many foodborne disease outbreaks. Here we present an investigation on the contamination and the antimicrobial resistance of Salmonella in retail meat obtained from supermarkets and from open markets in Guangxi, China. From the years 2009 to 2016, a total of 604 Salmonella isolates were recovered from a total of 3340 meat samples including 797 beef, 911 pork, 942 chicken and 690 duck, representing 18.08% of the samples tested. Pork was the most contaminated meat. Salmonella was detected in 322 samples from supermarkets and the positive rate of 21.03% was higher than that of 15.70% in 284 samples from open markets (P<0.05). The prevalence of Salmonella in retail meat in the summer and fall months: June (2015, 40.63%), October (2012, 34.6%; 2016, 43.75%) was higher than in other seasons of the year. One hundred and twenty-seven serotypes were identified among the 604 Salmonella enterica isolates, and S. Derby (28.48%), S. Agona (9.77%), S. London (4.97%) and S. Enteritidis (4.47%) were the most common serotypes. Tests of susceptibility to 21 antimicrobial agents showed that 87.58% of the isolates were resistant to at least one antimicrobial, and 57.79% exhibited multidrug resistance (MDR), as they were resistant to at least three antimicrobials. The presence of most of the antimicrobial-resistant genes tested was consistent with the resistant phenotypes found. Among all the antimicrobial resistant genes (ARGs) examined in this study, blaTEM-1, aadA1, cmlA, tetA, sul1 and sul2 were the most prevalent resistant genes in the multidrug resistant isolates. Our findings show that there was a trend that the Salmonella contamination in retail meat had increased and isolates showed an MDR phenotype and that the MDR had become more and more serious. Twenty-one isolates of S. Agona were randomly analyzed by using the enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) and six different types were found, indicating the existence of cross-contamination in the food market. The results indicate that the hazard analysis of the critical control points (HACCP) system for the whole food chain of retail meat should be further analyzed and improved.

[目的]明确β-防御素在黄沙鳖先天免疫中的潜在作用,为开展黄沙鳖绿色病害防治及促进其养殖业健康发展打下基础.[方法]运用RACE克隆黄沙鳖β-防御素基因(Hs-BD1)cDNA序列,采用SignalP-5.0、PredictProtein、PSIPRED、Robetta和Clustal X等在线软件进行生物信息学分析,并通过实时荧光定量PCR检测Hs-BD1基因在黄沙鳖不同组织中的表达特征及细菌感染前后的表达变化.[结果]Hs-BD1基因cDNA序列全长493 bp,包括72 bp的5'非编码区(5'-UTR)、201 bp的开放阅读框(ORF)及220 bp的3'非编码区(3'-UTR).Hs-BD1基因编码66个氨基酸残基,包括22个氨基酸残基组成的信号肽区、3个氨基酸残基组成的前肽区和41个氨基酸组成的成熟肽区.其中,成熟肽区具有6个保守的半胱氨酸残基(31Cys、58Cys、38Cys、52Cys、42Cys和59Cys)及位于C1和C2间的甘氨酸残基(Gly),即Hs-BD1基因属于β-防御素家族.Hs-BD1氨基酸序列与中华鳖β-防御素16的相似性最高(93.9％),基于β-防御素序列相似性构建的系统发育进化树也显示黄沙鳖与中华鳖和西部锦龟聚为一支,其亲缘关系相对较近.6个保守的半胱氨酸残基分别以C1-C5、C2-C4和C3-C6的连接方式形成3个二硫键;Hs-BD1成熟蛋白三级结构是由α-螺旋、β-折叠和无规则卷曲组成.Hs-BD1基因在黄沙鳖肝脏、脾脏、肺脏和肾脏中的相对表达量较高,在心脏、肠道、肌肉、脑组织和表皮中的相对表达量均较低;以温和气单胞菌攻毒后,Hs-BD1基因在黄沙鳖脾脏中的相对表达量呈上升—下降—上升—下降的变化趋势,在攻毒后第3和36 h共出现2个表达峰值,对应的相对表达量分别是攻毒前(0 h)的20.8和10.6倍,差异均极显著(P<0.01).[结论]Hs-BD1基因在黄沙鳖的多个组织中均有表达,尤其在肝脏、脾脏、肺脏和肾脏中的相对表达量较高,且可被温和气单胞菌感染诱导表达,说明Hs-BD1基因在黄沙鳖抵抗病原感染的过程中发挥调控作用.

[目的]检测广西凡纳滨对虾源副溶血弧菌的耐药性和整合子—基因盒携带情况,为凡纳滨对虾副溶血弧菌病的防控及该菌耐药分子机制研究提供基础数据.[方法]呆用K-B纸片扩散法测定副溶血弧菌对16种抗菌药物的敏感性;采用PCR检测Ⅰ、Ⅱ和Ⅲ型整合子及Ⅰ型整合子可变区基因盒的携带情况,并分析菌株整合子—基因盒携带情况与耐药性的相关性.[结果]104株广西凡纳滨对虾源副溶血弧菌对16种抗菌药物表现出不同程度的敏感性,其中,对氟苯尼考(FFC)的敏感性最高,敏感率达82.7％;对磺胺间甲氧嘧啶(SMM)、磺胺二甲嘧啶(SM2)和复方磺胺嘧啶(SD)的耐药性较强,耐药率达93.3％～100.0％.在2013-2018年,广西凡纳滨对虾源副溶血弧菌共有20种耐药谱,其中优势耐药谱为SD/SM2/SMM/SMD/SXT/RAD.PCR扩增结果表明,Ⅰ型整合酶int1基因检出率为64.4％,sul1和qacEΔ1基因检出率分别为25.0％和27.9％.int1、sul1和qacEA1基因均为阳性的菌株检出率为22.1％.在int1、sul1和qacEΔ1基因均为阳性的菌株中,有6株检出携带基因盒,基因盒种类包括blaCTX-M-2-aadA1和bla VIM-60-aadA1-aacA.所有菌株均未检出Ⅱ和Ⅲ型整合酶基因.int1和qacEΔ1基因在广西北海市、钦州市和防城港市分离菌株中的检出率差异显著(P＜0.05,下同).int1阳性菌株对甲砜霉素(TAP)的耐药率显著大于int1阴性菌株,但其余抗菌药物的耐药表型与int1基因无显著相关性(P＞0.05,下同);头孢拉定(RAD)的耐药表型与blaCTX-M-2和bla VIM-60基因、新霉素(NEO)的耐药表型与aadA1和aacA基因、磺胺类的耐药表型与sul1基因均无显著相关性.[结论]广西凡纳滨对虾源副溶血弧菌对氟苯尼考的敏感性最高,可考虑将该抗菌药物作为广西凡纳滨对虾副溶血弧菌病防治的备选药物.副溶血弧菌对大部分抗菌药物的耐药表型与int1基因间未检测到显著相关性、基因盒与相应抗菌药物的耐药表型间相关性也不显著,但Ⅰ型整合子的流行增加了广西凡纳滨对虾源副溶血弧菌产生多重耐药的可能性,因此应加强对弧菌整合子—基因盒的监控.

为了查明大口鲶体表溃烂的病因及指导养殖户用药,以常规方法从患体表溃烂病的南方大口鲶的肝脏和心脏中分离到4株优势菌株DKN01、DKN02、DKN03和DKN04,人工感染试验表明,4株分离菌株均为引起南方大口鲶体表溃烂病的病原菌.API 20NE生化鉴定结果,均为温和气单胞菌(Aeromonas sobria),4株病原菌对多粘菌素B、特治星、磺胺二甲嘧啶和盐酸沙拉沙星4种药物均敏感,对青霉素、氨苄青霉素、复方新诺明、新生霉素、氟苯尼考、磺胺-6-甲氧嘧啶(钠)和磺胺对甲氧嘧啶7种药物耐药.药敏结果可作为该养殖户治疗该病的用药参考.

用常规方法从患红底板病黄沙鳖的心脏和肝脏中分离到2株β溶血的革兰氏阴性短杆菌,回归感染试验证明均为致病菌,经API 20NE生化鉴定,2株病原菌分别为嗜水气单胞菌和温和气单胞菌.按K-B纸片扩散法进行28种药物的药敏试验结果,选用对2株病原菌都高度敏感的药物恩诺沙星,配合三黄散、芪参散和肝胆利康散等中草药进行拌料投喂,结合生石灰进行水体消毒等综合措施进行治疗,效果良好.

Duck spleen necrosis disease (DSND) is an emerging infectious disease that causes significant economic loss in the duck industry. In 2018, a duck reovirus (named DRV/GX-Y7) and Salmonella Indiana were both isolated from the spleens and livers of diseased ducks with DSND in China. The DRV/GX-Y7 strain could propagate in the Vero, LMH, DF-1 and DEF cells with obvious cytopathic effects. The genome of DRV/GX-Y7 was 23,418 bp in length, contained 10 dsRNA segments, ranging from 3959 nt (L1) to 1191 nt (S4). The phylogenetic analysis showed that the DRV/GX-Y7 strain was in the same branch with the new waterfowl-origin reovirus cluster, but was obviously far distant from the clusters of other previous waterfowl-origin reoviruses Muscovy duck reovirus (MDRV) and goose-origin reovirus (GRV), broiler/layer-origin reovirus (ARV) and turkey-origin reovirus (TRV). The RDP and SimPlot program analysis revealed that there were two potential genetic reassortment events in the M2 and S1 segments of the genome. In order to have a clear insight into the pathogenic mechanism of DRV/GX-Y7 and S. Indiana in clinical DSND, an infection experiment was further conducted by challenging commercial ducklings with the two isolates individually and with both. The results showed that DRV/GX-Y7 produced severe hemorrhagic and/or necrotic lesions in the immune organs (thymus, spleen, and bursae) of experimentally infected ducklings. And, that the co-infection of DRV/GX-Y7 and S. Indiana could greatly enhance the pathogenesis by increasing the morbidity and mortality in ducklings whose clinical symptoms and lesions were similar to the natural clinical DSND cases. In summary, the results suggested that the pathogen causing duck spleen necrosis was an emerging unique genetic reassortment strain of duck Orthoreovirus that was significantly different from any previously reported waterfowl-derived Orthoreovirus and the co-infection with the Salmonella isolate could increase the severity of the disease.