Nitazoxanide (NTZ) is a nitrothiazole benzamide compound with a broad activity spectrum against parasites, Gram-positive and Gram-negative anaerobic bacteria, and viruses. In this study, hybrid linear ion trap/Orbitrap mass spectrometer providing a high mass resolution and accuracy was used to investigate the metabolism of NTZ in rats, pigs, and chickens. The results revealed that acetylation and glucuronidation were the main metabolic pathways in rats and pigs, whereas acetylation and sulfation were the major metabolic pathways in chickens, which indicated interspecies variations in drug metabolism and elimination. With the accurate mass data and the characteristic MS(n) product ions, we identified six metabolites in which tizoxanide and hydroxylated tizoxanide were phase I metabolites and tizoxanide glucuronide, tizoxanide glucose, tizoxanide sulfate and hydroxyl tizoxanide sulfate were phase II metabolites. Hydroxylated tizoxanide and tizoxanide glucose were identified for the first time. All the comprehensive data were provided to make out the metabolism of NTZ in rats, pigs and chickens more clearly.

[Objective]This experiment was conducted to study the excretion of roxarsone in poultry after being fed with roxarsone and its toxicity to the environment .[Method] Thirty yellow plumage meat chick-ens were fed with poultry feed containing roxarsone 50 mg/kg.The feeding trial lasted for 10 days.The excreta were collected at 12 to 240 h after administration and a 5 d withdrawl period .The total arsenic , As(Ⅲ) , As ( V ) in excreta were analyzed by microwave digestion-atomic fluorescence spectrometry ( AFS) method and the roxarsone was analyzed by HPLC .Photo degradation of roxarsone in poultry ex-creta was evaluated .[Result and conclusion]The excreted amount of roxarsone reached a steady-state concentration at 108 h after administration ( the range of roxarsone concentration was 31.62 -35.87 mg/kg; the range of total arsenic concentration was 16.75-21.48 mg/kg) .Roxarsone was undetectable in poultry excreta at 120 h after withdrawal, and the total arsenic was down to 3.89 mg/kg.The quantity of As(Ⅲ) and As (Ⅴ) slightly fluctuated and the peaks were 0.38 and 1.81 mg/kg correspondingly . There was a significant effect of light on the degradation of roxarsone .The results indicated that most of roxarsone was not absorbable and can quickly be eliminated with no change .The degradation rate of rox-arsone can increase the effect of photolysis .

用乙二胺四乙酸二钠溶液稀释猪血浆样品,用SEP-PAK-C18固相萃取小柱富集药物,再以含有离子对试剂的乙腈洗脱.以氮气吹干洗脱液,流动相复溶后测定药物的质量浓度.HPLC分析柱为BDS C18,流动相组成为V(乙腈)∶V(pH 3.2的0.005 mol/L辛烷磺酸钠溶液)=30∶70,紫外检测波长372 nm.猪血浆中三氮脒的质量浓度在0.01～40.0 μg/mL范围内可准确定量;血浆中三氮脒的质量浓度为0.05、0.5、10 μg/mL时,相对回收率≥89.09％,批间变异系数在0.81％～4.41％之间.猪血浆中三氮脒的定量限为5ng/mL,检测限为2 ng/mL.结果表明,本研究建立的HPLC方法操作简单、重复性和灵敏度好,定量范围宽,适用于检测猪血浆样品中三氮脒的质量浓度.

采用平衡振荡法,研究了不同利用类型的北方土和南方土对阿散酸和洛克沙胂2种有机胂添加剂的吸附行为.结果表明:有机质和总铁含量高的偏酸性南方土对2种有机胂的吸附强度远远大于有机质和总铁含量低的偏碱性北方土；北方土添加腐殖质后对阿散酸和洛克沙胂吸附量分别增加了3倍和10倍左右,南方土去除有机质后吸附量显著下降；南方树木园土和农场土对洛克沙胂和阿散酸的吸附更符合Langmuir吸附等温线,树木园土对阿散酸和洛克沙胂的饱和吸附量分别为1 111和1 250mg· kg-1,农场土对阿散酸和洛克沙胂的饱和吸附量分别为66和250 mg·kg-1,初始质量浓度对洛克沙胂的吸附量影响更大.

OBJECTIVESTo characterize a representative self-transmissible multidrug resistance plasmid pHN7A8 isolated from an Escherichia coli from a dog in China, classified as F33:A-:B- by replicon sequence typing and carrying the bla(TEM-1b), bla(CTX-M-65), fosA3 and rmtB genes conferring resistance to penicillins, cephalosporins, fosfomycin and aminoglycosides, respectively.METHODSpHN7A8 was sequenced using a whole-genome shotgun approach and the sequence analysed by comparison with reference plasmids.RESULTSpHN7A8 is a circular molecule of 76 878 bp. bla(CTX-M-65), fosA3 and rmtB are found in known contexts, interspersed with different mobile elements including ISEcp1, IS1, Tn2, IS1294, IS903 and four copies of IS26. This multiresistance region has only a single nucleotide difference from that of pXZ, an F2:A-:B- plasmid isolated from poultry in China. The pHN7A8 backbone carries genes encoding addiction and partitioning systems that promote plasmid maintenance and has a similar organization to pXZ, as well as IncFII plasmids such as R100, pC15-1a/pEK516 and pHK23, isolated in Japan, Canada/the UK and China, respectively, but with varying levels of identity, suggesting recombination.CONCLUSIONSpHN7A8 is a chimera that may have resulted from the acquisition, by recombination in the plasmid backbone, of the multiresistance region found in pXZ. This region appears to have evolved from the resistance determinant R100 through the stepwise integration of multiple antimicrobial resistance determinants from different sources by the actions of mobile elements and recombination. The successful dissemination of this multidrug resistance plasmid presents further challenges for the prevention and treatment of Enterobacteriaceae infections.

<正>兽医不仅承担保护动物健康的职责,在公共卫生和食品安全领域也起到了不可替代的作用。细菌耐药性已成为全球关注的热点问题,畜禽养殖业广泛使用抗菌药物造成了耐药性的快速发展,不仅影响动物的健康,还给食品安全、人类健康和公共卫生带来严重危害。因此,克服细菌耐药问题已成为当前养殖业中不可忽视的问题。为满足现代社会和科学发展的需要,兽医本科教育应与时俱进,建议在其基础课程中纳入细菌耐药性教育的有关内容,使学生全面了解和掌握畜禽细菌耐药性的危害和合理使用抗生素、遏制抗生素耐药性产生的重要性,增强学生抵御细菌耐药性产生的意识和能力,以培养能适应现代社会需要、具有创新精神和综合能力的合格兽医人才。

The purpose of this study was to investigate the carriage rate and antimicrobial resistance of Staphylococcus pseudintermedius(SP) isolated from pets in Guangdong province.S.pseudintermedius were isolated from samples collected from skin,ear,nasal cavity and other parts of pets.The antimicrobial susceptibility test was carried out by agar dilution method and disk diffusion method.PCR was carried out to detect mecA gene.A total of 144(16.0%) S.pseudintermedius strains were obtained from the 898 samples collected from pets.The detection rates of skin,ear and nasal cavity were 20%(64/319),17.8%(64/359) and 7.5%(3/40),respectively.The antimicrobial susceptibility test results and mecA detection result showed that 89(61.8%) were methicillin-resistant S.pseudintermedius(MRSP).Resistance rates of the 144 S.pseudintermedius to ampicillin,erythromycin,azithromycin,clindamycin and tetracycline were over 80%.Resistance rates to amikacin and rifampicin was under 8%.All of the 144 S.pseudintermedius were susceptible to vancomycin,linezolid,quinupristin/dalfopristin and teicoplanin.Most(more than 69%) MRSP resisted to erythromycin,clindamycin,tylosin,azithromycin,trimethoprim-sulfamethoxazole,tetracycline,ciprofloxacin,and enrofloxacin.In conclusion,the high level antimicrobial resistance and high detection rate of MRSP was observed among the S.pseudintermedius isolates from companion animals.More attention should be addressed to the serious bacterial resistance in companion animals.

ABSTRACT The presence and characterization of plasmid-mediated fosfomycin resistance determinants among Escherichia coli isolates collected from pets in China between 2006 and 2010 were investigated. Twenty-nine isolates (9.0%) were positive for fosA3 , and all of them were CTX-M producers. The fosA3 genes were flanked by IS 26 and were localized on F2:A−:B− plasmids or on very similar F33:A−:B− plasmids carrying both bla CTX-M-65 and rmtB . These findings indicate that the fosA3 gene may be coselected by antimicrobials other than fosfomycin.

The antimicrobial susceptibility of 103 Riemerella anatipestifer isolates obtained from ducks during 2008 and 2010 in Southern China, to 23 antimicrobial agents was investigated using the agar dilution method. The MIC(50) and MIC(90) values of streptomycin, kanamycin, gentamicin, apramycin, amikacin, neomycin, nalidixic acid and sulfadimidine were high (32-≥ 128 μg/ml) among the 103 R. anatipestifer isolates. However, relatively low MIC(90) values (8 μg/ml) of ampicillin and florfenicol were observed among these isolates. The presence of resistance genes and integrons was determined using PCR. The genes bla(TEM-1), aph(3')-VII, aadA1, aadA2, aac(3')-IV, aac(3')-IIc, aac(6')-Ib, cat2, cmlA, floR, tet(A), tet(B), tet(C), sul1, and sul2 were detected in 1, 2, 24, 35, 11, 4, 67, 16, 26, 10, 6, 1, 9, 36 and 2 isolates, respectively. Twenty isolates contained one or two class 1 integrons carrying aadA2 or aac(6')-II-catB3-aadA1 gene cassette(s). Mutation analysis of the quinolone resistance-determining regions (QRDRs) of 43 R. anatipestifer isolates with nalidixic acid MICs ≥ 32 μg/ml, showed that the most prevalent mutations in gyrA were those resulting in the amino acid exchanges Ser83-Ile (n=37), followed by Asp87-His (n=7) and Ser83-Arg (n=5). Point mutations in parC (Arg120-Glu) were observed in 5 isolates with a ciprofloxacin MIC of >16 μg/ml. No plasmid-mediated quinolone resistance gene was detected. PFGE analysis showed that the clonal spread of multi-drug resistant R. anatipestifer isolates occurred in the same farm or between different farms. Our results reported, for the first time, the mechanism of quinolone resistance in R. anatipestifer.

ABSTRACT In this study, we focused on evaluating the occurrence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in fecal samples of healthy ducks and environmental samples from a duck farm in South China. Duck cloacal swabs and pond water samples were cultivated on MacConkey agar plates supplemented with ceftiofur. Individual colonies were examined for ESBL production. Bacteria identified as E. coli were screened for the presence of ESBL and plasmid-borne AmpC genes. The genetic relatedness, plasmid replicon type, and genetic background were determined. Of 245 samples analyzed, 123 had E. coli isolates with ceftiofur MICs higher than 8 μg/ml (116 [50.4%] from 230 duck samples and 7 [46.7%] from 15 water samples). bla CTX-M , bla SHV-12 , bla CMY-2 , and bla DHA-1 were identified in 108, 5, 9, and 1 isolates, respectively. The most common bla CTX-M genes were bla CTX-M-27 ( n = 34), bla CTX-M-55 ( n = 27), bla CTX-M-24e ( n = 22), and bla CTX-M-105 ( n = 20), followed by bla CTX-M-14a , bla CTX-M-14b , bla CTX-M-24a , and bla CTX-M-24b . Although most of the CTX-M producers had distinct pulsotypes, clonal transmission between duck and water isolates was observed. bla CTX-M genes were carried by transferable IncN, IncF, and untypeable plasmids. The novel CTX-M gene bla CTX-M-105 was flanked by two hypothetical protein sequences, partial IS Ecp1 upstream and truncated IS 903D , iroN , orf1 , and a Tn 1721 -like element downstream. It is suggested that the horizontal transfer of bla CTX-M genes mediated by mobile elements and the clonal spread of CTX-M-producing E. coli isolates contributed to the dissemination of bla CTX-M in the duck farm. Our findings highlight the importance of ducks for the dissemination of transferable antibiotic resistance genes into the environment.

The impact of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae of food animal origins on human health has caught considerable attention worldwide. Intestinal Escherichia coli obtained from healthy food animals (pigs, cattle and poultry) in China were tested for the presence of ESBL genes. CTX-M-producing isolates were further characterised by pulsed-field gel electrophoresis (PFGE), phylogenetic grouping, genetic environment analysis, conjugation and plasmid replicon typing. A total of 127 of the 896 E. coli isolates showed reduced susceptibility to cefotaxime (minimal inhibitory concentration≥2 μg/mL). bla(CTX-M) genes were detected in 111 of the 127 isolates. The most common CTX-M types were CTX-M-14 (n=40), CTX-M-55 (n=29) and CTX-M-65 (n=22), followed by CTX-M-27, -15, -98, -24, -3, -102 and -104. CMY-2 was detected in two isolates. High clonal diversity was found amongst CTX-M-producing isolates. Insertion sequence ISEcp1 was observed 42 bp upstream of the start codon of all CTX-M-9 group genes, whereas the spacer region between the right inverted repeats and CTX-M-1 group genes varied from 45 bp to 127 bp. Most bla(CTX-M) genes were transferable by conjugation. IncFII, IncI1, IncFIB, IncN and IncA/C replicons were detected in 28, 21, 7, 5 and 1 of the 70 transconjugants carrying bla(CTX-M), respectively. This study demonstrates that commensal E. coli from healthy food animals can be important reservoirs of bla(CTX-M) genes and may contribute to the dissemination and transfer of these β-lactamase genes throughout China.

The variable region genes of heavy chain（VH） and light chain（VL） of anti-difloxacin monoclonal antibody（McAb） were amplified by RT-PCR from total RNA extracted from X1 hybridoma cell.PCR products were cloned into pUC18 vector and sequenced by Sanger＇s dideoxymediated chain-termination method.The results showed that VH gene consisted of 363bp encoding 121 amino acid residues;VL gene consisted of 348bp encoding 116 amine acid residues,which contain four FRs and three CDRs,respectively.Compared with mouse Ig database,the VH and VL regions are in accord with the characterization of DNA sequence present in the mouse Ig region.The successful clone of VH and VL genes of X1 McAb made it a solid foundation to the construction of engineering antibody against difloxacin.

【Objective】 To analyze the plasmid-mediated 16SrRNA methylase genes and their horizontal transferable mode of Enterobacter cloacae GZL42B which was isolated from pig farm.【Method】 Polymerase chain reaction(PCR) and sequencing were applied to detect and identify the 16SrRNA methylase resistant gene.Conjugation experiments were used to study the horizontal transferable mode of 16SrRNA methylase in E.cloacae by using the E.coli Rif+488(rifampin-resistant) as the recipient.MICs were evaluated by using the micro-dilution method.Comparison of the neighboring sequences of rmtB between E.cloacae GZL42B and Escherichia coli GZL42B which isolated from the same rectal swab of one pig and the prevalence of 16SrRNA methylases genes in 172 E.coli were investigated by PCR and sequencing.【Result】 The fragment of rmtB was amplified succeessfully.The restriction fragments were corresponded with the expectant,and the rmtB was confirmed by using sequencing.The accession number of the rmtB sequence submitted to GenBank was EF017943.Transconjugant was obtained successfully by using the E.coli Rif+488 as the recipient.The MICs of the parental E.cloacae GZL42B and its transconjugant to kanamycin,amikacin,tobramycin,sisomicin,netilmicin and gentamycin were ≥256 μg·mL-1.The right-hand end of transposon Tn3 and the orf1 which was part of groEL/intI1 on genomic island SG1 of Salmonella enterica serovar Typhimurium were located on the upstream and downstream of rmtB in Escherichia coli GZL42H,respectively.But they were not amplified in E.cloacae GZL42B.Tweenty-five and one of all 172 isolates(15% and 0.6%) were rmtB and armA positive,respectively.【Conclusion】 It was the first report that the 16SrRNA methylase rmtB emergenced in E.cloacae from pig farm.High resistance to 4,6-deoxystreptamine was mediated by rmtB and can be transferred to E.coli Rif+488.The rmtB can be transferred between different species of bacteria.The genetic basis for dissemination of rmtB was different between E.coli GZL42H and E.cloacae GZL42B.And the rmtB was highly prevalent in animal E.coli.

The current developing status and trend of the disinfectants were summarized overall in the paper.The properties,application and prospects of a series of representative disinfectants products both from home and abroad were analyzed.The direction and tendency of research and development of the disinfectants in the future were generalized.The disinfectants appeared to be going in the specialization and diversifying direction.

This study investigated the prevalence of 16S rRNA methylase genes in 267 Enterobacteriaceae isolates collected from pets. The rmtB gene was detected in 69 isolates, most of which were clonally unrelated. The coexistence of the rmtB gene with the bla(CTX-M-9) group genes and/or qepA within the same IncFII replicons was commonly detected. The two dominant types of IncF plasmids, F2:A-:B-, carrying rmtB-qepA, and F33:A-:B-, carrying the rmtB-bla(CTX-M-9) group genes (and especially bla(CTX-M-65)), shared restriction patterns within each incompatibility group.

Objectives: To investigate the prevalence and characterization of 16S rRNA methylase-producing bacteria in a pig farm and its environment in East China.Methods: Enterobacteriaceae isolates and metagenomic DNA from 102 pig faecal samples from a pig farm and 97 soil samples taken in or around the farm were screened for the presence of 16S rRNA methylase genes. The clonal relationships of 16S rRNA methylase-positive isolates, plasmid content and other associated resistance genes were also characterized.Results: Fifty-six rmtB-positive Enterobacteriaceae isolates, including 54 Escherichia coli, 1 Morganella morganii and 1 Proteus mirabilis, were recovered from 55 pig faecal samples. Nineteen rmtB-positive bacteria, including 13 E. coli, 2 M. morganii, 2 Leclercia adecarboxylata, 1 Enterobacter aerogenes and 1 Enterobacter cloacae, were recovered from 16 soil samples. Among the 75 rmtB-positive isolates, 31 and 25 also carried the qepA and bla(CTX-M) genes, respectively. The qepA gene co-localized with rmtB on the F2:A-:B1 plasmids and the bla(CTX-M-65) gene co-localized with rmtB on the F33:A-:B-plasmids. The rmtB gene was also found to be associated with the IncN plasmids. Clonal transmission of rmtB-positive E. coli isolates was observed between different pig groups and soil samples.Conclusions: Both horizontal gene transfer and clonal spread could be responsible for the dissemination of the rmtB gene in the pig farm and its environment. To our knowledge, this study is the first report of rmtB-positive bacteria from farmland soils and indicates that these antibiotic-resistant bacteria and/or resistance genes could be acquired by humans through the food chain.

A method employing the oil of vitriol and phenol testing neutral sugars to detect the level of glucose in mature oocyst of Eimeria tenella was established.The level of glucose in mature oocyst of 9 different stains in E.tenella(including sensitive stain and drug-resistant stains)were detected.The results were as follows,the level of glucose in mature oocyst of sensitive strain was low;the level of glucose in mature oocyst of the drug-resistant strains was high(P<0.01,showed significant correlation).Thus,the stains of E.tenella with different drug sensitivity were related with the level of glucose in mature oocyst.The level of glucose in mature oocyst could be used as one of the indicators to anticoccidial drug sensitivity of E.tenella.

文章对抗微生物药在环境中的残留现状,在环境中的迁移、蓄积、降解及其对动物、植物、微生物的影响等研究进展进行了概述,在此基础上对今后研究重点进行了展望。针对抗微生物药的合理应用提出了如下基本原则:①严格掌握适应症和抗菌谱选用抗菌药;②掌握药物动力学特征,制定合理的给药方案;③避免耐药性的产生;④防止药物的不良反应和药物残留;⑤抗菌药的联合应用。

ABSTRACT OqxAB has recently been identified as one of the mechanisms of plasmid-mediated quinolone resistance (PMQR). Compared to what is observed for other PMQR determinants, there is a paucity of data with regard to the prevalence and epidemiology of OqxAB and its contribution to resistance to different antimicrobials. In this study, the prevalence and dissemination of oqxAB and other PMQR genes in Escherichia coli isolates from animals, farmworkers, and the environment in 2002 in China were investigated. Of the 172 E. coli isolates, 39.0% carried oqxA , while only 4.1%, 2.9%, and 0.6% carried qnr (1 qnrB6 isolate, 5 qnrS1 isolates, and 1 qnrD isolate), qepA , and aac(6′)-Ib- cr , respectively. Among the 33 isolates from farmworkers, 10 (30.3%) were positive for oqxA . oqxAB was associated with IS 26 and was carried on the 43- to 115-kb IncF transferable plasmid. Transconjugants carrying oqxAB showed 4- to 16-fold increases in the MICs of quinolones, 16- to 64-fold increases in the MICs of quinoxalines, 8- to 32-fold increases in the MICs of chloramphenicol and trimethoprim-sulfamethoxazole, and 4- to 8-fold increases in the MICs of florfenicol compared to the levels for the recipient. The pulsed-field gel electrophoresis (PFGE) analysis showed that the high levels of prevalence and dissemination of oqxA B in E. coli in animal farms were primarily due to the transmission of plasmids carrying oqxAB , although clonal transmission between human and swine E. coli isolates was observed. It is concluded that oqxAB was widespread in animal farms in China, which may be due to the overuse of quinoxalines in animals. This study warrants the prudent use of quinoxalines in food animals.

To study the transfer mode of rmtB in Enterobacteria isolates from pig farms.Pulse field gel electrophoresis(PFGE) were carried out to study the genotyping of 48 rmtB-positive E.coli isolates from A and B pig farms.Conjugation experiments was carried out to study the horizontal transfer mode of rmtB genes by filter mating method.Broth microdilution method was applied to test susceptibility of rmtB-positive isolates and their transconjugants to antimicrobial agents.Among 48 rmtB-positive E.coli isolates,45 strains were successfully typed by PFGE.Total of 28 different PFGE profiles were obtained,and 12 different PFGE profiles were obtained in 20 isolats from A pig farm,16 different PFGE profiles were acquired in 25 isolats from B pig farm.All the rmtB genes located in 46 rmtB-positive isolates were easily transferred to recipients of E.coli C600 and E.coli 488 Rifr.Conjugative transfer frequencies varied from 4.6×10-13 to 3.0×10-6 cells per recipient cell.And all 46 transconjugants showed extraordinarily high-level resistance to 4,6-substituted deoxystreptamine(MICs512 μg/mL).It concluded that the rmtB gene was located on a conjugative plasmid in E.coli.Both horizontal gene transfer and clonal expansion were responsible for the dissemination of rmtB gene and horizontal gene transfer was predominant in E.coli isolates from two pig farms.