Stability of plasmid content in Salmonella wien in late phases of the epidemic history

Prevalence, genetic characteristics, and EcoRI cleavage analysis of plasmids identified in clinical strains of Salmonella wien isolated in recent years showed that the plasmid content in this serotype has remained uniform and stable over more than a decade and also late in the epidemic history. No correlation between decrease in S. wien isolations and naturally occurring systematic changes in the DNA of its most common FIme plasmid was structurally detectable.     

Dihydrofolate reductase in Pediococcus cerevisiae strains susceptible and resistant to amethopterin

A mutant strain of Pediococcus cerevisiae was obtained which had 1,000-fold greater resistance to amethopterin than the P. cerevisiae/PteGlu strain. The dihydrofolate reductase level of the mutant was about 60-fold higher than that of the parent. The mutant accumulated folate, though less efficiently than its parent.     

Susceptibility of Gardnerella vaginalis to cephradine

The activity of cephradine and the influence of pH on its activity against 70 Gardnerella vaginalis strains were determined. Serial dilutions of cephradine (0.062 to 256 micrograms/ml) were incorporated into Dunkelberg agar, inoculated with a Steers replicator, incubated in 5% CO2 for 48 h, and examined. The minimal inhibitory concentrations for 90% of the isolates were 16 and 8.0 micrograms/ml at pH 7.0 to 6.0 and 5.5, respectively.     

PICC相关性导管感染与堵塞的关系及易感菌分布

[目的]探讨经外周静脉置入中心静脉导管(PICC)相关性感染与堵塞的关系及感染细菌的菌株分布.[方法]选择2010年1月-2011年6月锦州市中心医院行PICC穿刺的210例病人,对导管样本进行培养,观察感染及堵塞的发生率,并明确易感菌株分布情况.[结果]PICC相关性导管感染与堵塞密切相关;导管易感菌株为革兰阳性菌,占65.6％,其中表皮葡萄球菌为31.2％.[结论]预防PICC相关性导管感染(尤其是表皮葡萄球菌感染)和导管堵塞是减少PICC相关并发症的有效措施.     

健康人携带的沙门菌中沙门菌基因组岛1的鉴定及特性分析

目的 检测健康人携带的沙门菌中沙门菌基因组岛（SGI1）的分布情况及特性,分析其与细菌耐药性的关系.方法 采用PCR方法对5株第一类整合子阳性的沙门菌检测SGI1,分别检测其左侧、右侧部分和其中间的部分基因,以及环状形式和切除状态,通过接合转移及自然转化检测其可移动性.结果 一株鼠伤寒沙门菌携带SGI1,位于thdF和int2之间,且其多重耐药区含aadA2,floR,tetG,blaPSE-1基因,存在环状形式及切除状态,且可通过自然转化方式转移至其他菌株.结论 SGI1可通过自然转化方式转移到其他菌株,介导多重耐药的传播.     

PICC相关性导管感染与堵塞的关系及易感菌分布

摘[目的]探讨经外周静脉置入中心静脉导管（PICC）相关性感染与堵塞的关系及感染细菌的菌株分布。[方法]选择2010年1月-2011年6月锦州市中心医院行PICC穿刺的210例病人,对导管样本进行培养,观察感染及堵塞的发生率,并明确易感菌株分布情况。[结果]PIcc相关性导管感染与堵塞密切相关;导管易感菌株为革兰阳性茵,占65．6％,其中表皮葡萄球菌为31．2％。[结论]预防PICC相关性导管感染（尤其是表皮葡萄球菌感染）和导管堵塞是减少PICC相关并发症的有效措施。     

Accumulation and transport of cadmium by tolerant and susceptible strains of Mycobacterium scrofulaceum.

Cadmium accumulation and transport were studied in two strains of Mycobacterium scrofulaceum differing in their susceptibility to Cd2+ toxicity. A 10-fold excess of either Zn2+ or Mn2+ partially antagonized inhibition of growth by Cd2+. 109Cd2+ uptake by both the tolerant and susceptible strains was temperature dependent and inhibited by a 10-fold excess of either Zn2+ or Mn2+. There were no significant differences in either the kinetics of 109Cd2+ uptake or the retention of accumulated 109Cd2+ by the tolerant and susceptible strains. Both tolerant and susceptible strains removed most of the cadmium from the culture medium, but significantly more was removed by cells of the tolerant strain. Most of the accumulated Cd2+ in the tolerant strain was in the particulate fraction, rather than in the soluble fraction. Intracellular accumulated Cd2+ was primarily in the soluble fraction of the susceptible strain. Increased Cd2+ in culture medium resulted in decreased Mn2+ and Zn2+ in cells of the susceptible strain but did not reduce the Mn2+ and Zn2+ content of cells of the tolerant strain.     

Susceptibility of pneumococci to 14 beta-lactam agents: comparison of strains resistant, intermediate-resistant, and susceptible to penicillin.

To measure the susceptibility of penicillin-resistant pneumococci to newer beta-lactam agents, we evaluated 54 selected strains recovered from patients with bacteremia or meningitis. Three groups of pneumococci were tested: penicillin-susceptible strains, strains with intermediate penicillin resistance, and penicillin-resistant strains. Minimal inhibitory concentrations of benzyl penicillin, oxacillin, cephalothin, cefamandole, cefoxitin, moxalactam (LY127935), cefotaxime (HR756), piperacillin, pirbenicillin, N-formimidoyl thienamycin (MK0787), cefoperazone (T1551), mezlocillin, azlocillin, and mecillinam were determined. For all groups of pneumococci tested, cefotaxime, and particularly thienamycin, had the greatest activity. Piperacillin, mezlocillin, and azlocillin had activity similar to that of benzyl penicillin. Cefoperazone had less activity than penicillin against strains with penicillin minimal inhibitory concentrations of less than 1 microgram/ml but greater activity than penicillin against strains with greater resistance. Oxacillin, cephalothin, cefamandole, and pirbenicillin all had less activity for each group of pneumococci tested; moxalactam, cefoxitin, and mecillinam had the least activity. The relative differences in susceptibility to penicillin of each group of pneumococci tested were similar for each of the beta-lactam agents tested. The clinical effectiveness of cefotaxime and thienamycin for therapy of disease due to penicillin-resistant pneumococci needs further evaluation, and of particular interest will be the levels of these drugs which can be achieved in cerebrospinal fluid.     

72株沙门菌血清型分布及药敏试验结果分析

目的：了解广东东莞地区沙门菌血清型分布,腹泻患者沙门菌检出数量及药敏试验结果,为该省今后的疾病防控,药物治疗提供参考依据。方法收集东莞市人民医院2013年4—12月门诊及住院患者腹泻粪便标本1150份,用改良亚硒酸盐磺绿增菌肉汤和沙门菌显色平皿分离检测沙门菌;药敏试验采用法国生物梅里埃ATB微生物鉴定和药敏分析系统及其配套药敏试条。结果共检出沙门菌72株,检出率为6．3％,分出21个血清型,以鼠伤寒沙门菌检出数量最多,22株（30．5％）,肠炎沙门菌16株（22．2％）。年龄分布1周岁以下42株（58．3％）,3-10岁12株（16．7％）,20岁以上18株（25．0％）。药敏试验结果耐药率较高的药物有哌拉西林（50．0％）,替卡西林（48．6％）。结论本地区腹泻患者检出沙门菌属以鼠伤寒沙门菌检出率最高,肠炎沙门菌次之,年龄1周岁以下较多。临床医师应加强对腹泻患者沙门菌属监测,尤以婴幼儿为重点,早期发现早期治疗以减少并发症发生。     

Risk factors for isolation of strains susceptible only to polymyxin among patients with Pseudomonas aeruginosa bacteremia

We conducted a case-control study to identify risk factors associated with the isolation of Pseudomonas aeruginosa strains susceptible only to polymyxin from blood by comparing data between 16 patients with blood isolates that were susceptible only to polymyxins and 40 patients with blood isolates that were susceptible to carbapenems. The multivariable analysis showed that exposure to carbapenems was associated with the development of P. aeruginosa bacteremia susceptible only to polymyxin (odds ratio, 9.0; 95% confidence interval, 2.4 to 34.3; P = 0.001).     

Physical and genetic mapping of the Salmonella dublin virulence plasmid pSDL2. Relationship to plasmids from other Salmonella strains.

Plasmids of approximately 80 kb in size are found in nearly all clinical isolates of Salmonella dublin and are believed to be essential for virulence. We have shown previously that the 80-kb plasmid pSDL2 is required for the S. dublin Lane strain to establish a lethal systemic infection in BALB/c mice after oral or intraperitoneal inoculation. We now present a physical and genetic characterization of pSDL2. We have established a complete restriction endonuclease cleavage map of pSDL2 for five enzymes: Xba I, Bam HI, Xho I, Sal I, and Hind III. The region specifying autonomous replication has been localized to a 10.5-kb region of the Sal I A fragment by subcloning on the vector pBR322. Using transposon insertion mutagenesis with Tn5-oriT, a region encoding the virulence phenotype has been mapped within a 6.4-kb portion of the Sal I B fragment. Deletions generated by partial Eco RI restriction digestion demonstrate that at least 50 kb of the plasmid DNA are not required for replication or virulence functions, confirming the map location of these phenotypes. Plasmids of different sizes and restriction patterns were found in mouse virulent strains of S. dublin Vi+, S. enteritidis, and S. choleraesuis. By Southern hybridization, these putative virulence plasmids share a common 4-kb Eco RI fragment with the virulence region of pSDL2, and the plasmids from S. dublin Vi+ and S. enteritidis were shown to express mouse virulence comparable to pSDL2.     

Sulbactam efficacy in experimental models caused by susceptible and intermediate Acinetobacter baumannii strains

Sulbactam and imipenem were compared in an experimental pneumonia model in immunocompetent mice, using a susceptible strain of Acinetobacter baumannii, and in an experimental endocarditis model in rabbits, using an intermediately susceptible strain. In the former, sulbactam was as efficacious as imipenem in terms of survival, sterility of lungs and in the bacterial clearance from lungs and blood, provided that the t > MIC for sulbactam (1.84 h) was similar to that for imipenem (2.01 h). In the endocarditis model, imipenem (t > MIC, 2.12 h) was more efficacious than sulbactam (t > MIC, 1.17 h) in bacterial clearance from vegetations. These results show the efficacy of sulbactam in infections caused by susceptible strains of A. baumannii, with an MIC up to 4 mg/L, provided that doses reach a t > MIC similar to that of imipenem. The activity of sulbactam was time dependent.     

388株甲型副伤寒沙门菌对常用抗菌药物的敏感性

目的测定临床分离甲型副伤寒沙门菌对21种常用抗菌药物的敏感性，为治疗该菌感染提供依据。方法自病人血液、骨髓穿刺液中分离出甲型副伤寒沙门菌388株，采用ATB全自动鉴定及药敏测试仪测定此菌的体外药物敏感性。结果测定该菌对21种常用抗菌药物敏感率，氯霉素、氧氟沙星、亚胺培南和美罗培南为100％；敏感率在90％以上者为哌拉西林、替卡西林、替卡西林一克拉维酸、氨曲南、头孢噻肟、头孢哌酮、头孢吡肟、头孢西丁、庆大霉素、奈替米星、妥布霉素和环丙沙星等。结论甲型副伤寒沙门菌体外药敏试验对常用的半合成青霉素，头霉素类，碳青霉烯类，氨基糖苷类，第三、四代头孢菌素和氟喹诺酮类等药物均敏感。     

Decreased binding of antibiotics to lipopolysaccharides from polymyxin-resistant strains of Escherichia coli and Salmonella typhimurium.

The interactions of polycationic antibiotics with lipopolysaccharide (LPS) isolated from parental and polymyxin-resistant strains of Salmonella typhimurium and Escherichia coli were measured by using a cationic spin probe. Electron spin resonance spectra indicated that increasing concentrations of cations competitively displaced probe from LPS aggregates. Polymyxin B and other cations displaced less probe from LPS of polymyxin-resistant strains than from LPS of the parental strains, whereas the same amount or more probe was displaced from isolates of the mutants by the structurally similar antibiotic, EM 49 (octapeptin). In general, the differential affinities of these antibiotics for LPS correlated with their antibiotic activity in vivo, suggesting that resistance results from a decrease in antibiotic permeability across the outer membrane due to alterations in the LPS which affect antibiotic binding. The alterations in the structure of LPS from the polymyxin-resistant mutants of E. coli were characterized using 31P nuclear magnetic resonance spectroscopy. The results suggested that esterification of the core-lipid A phosphates is responsible for increased resistance to polymyxin B and that this alteration is different from that previously proposed for the S. typhimurium strains. In both cases, however, resistance was the result of modifications that result in a less acidic lipid A.     

Plasmid-mediated resistance to trimethoprim-sulfamethoxazole in Salmonella krefeld strains isolated in the United States

Two types of transmissible plasmids which encode resistance to trimethoprim-sulfamethoxazole were found among five animal isolates of Salmonella krefeld. This is the first report of plasmid-mediated resistance to trimethoprim-sulfamethoxazole in Salmonella strains isolated in the United States.     

Isolation of Salmonella enterica serovar Agona strains and their similarities to strains derived from a clone caused a serovar shift in broilers

Salmonella enterica serovar Agona strains isolated from human cases were compared to strains that were derived from a clone caused a serovar shift in broilers. Pulsed field gel electrophoresis (PFGE) analysis with XbaI or BlnI digestion showed that three of seven strains from human case strains and most of the 81 strains from broilers were clustered in single complex in a minimum spanning tree (MST) reconstructed from the PFGE data. All the strains from human cases and 22 randomly selected strains from broilers were also analyzed by whole genome sequencing (WGS). Analysis of single nucleotide polymorphism (SNP) in the S. Agona core genes showed that four strains from human cases and all the strains from broilers were clustered in a maximum likelihood phylogenetic tree (ML tree) and an MST. These results indicated that the strains derived from the clone caused the serovar shift had already spread to humans. PFGE analysis with XbaI showed that four strains from broilers did not cluster with the other strains in an MST, though all those strains clustered in an ML tree and an MST reconstructed from SNP data. Moreover, three strains from broilers did not cluster in an MST reconstructed from PFGE with BlnI digestion, though those strains clustered in an ML tree and an MST reconstructed from SNP data. Therefore, it was suggested that S. Agona strains derived from a particular clone could not be traced by PFGE analysis but can be investigated by WGS analysis.     

Molecular characterisation of Salmonella strains by an oligonucleotide multiprobe microarray

A DNA microarray has been developed for the simultaneous characterisation and typing of Salmonella enterica subsp. enterica isolates. One-hundred and nine 35-40 mer oligonucleotides probes detect flagellar and somatic antigen encoding genes (serogroup or serotype specific), important virulence genes located within or outside the pathogenicity islands, phage-associated genes and antibiotic resistance determinants. The probes were printed on glass slides and whole genomic Cy5-labelled Salmonella DNA was hybridised to the substrate. A set of 19 different Salmonella strains and one Escherichia coli strain has been selected as positive and negative controls for each probe. The validity of the results is confirmed by gene-specific PCRs or phenotypic methods (serotyping, MIC determination for various antimicrobial agents). Of 2071 data points generated, an agreement of 97.4% has been obtained between microarray and PCR/phenotypic results. Twenty-six data points (1.3%) were classified as uncertain and, similarly, 1.3% showed a discordant result. The microarray described here is a new tool to study the epidemiology of Salmonella strains on the genotypic level and might become a powerful method in risk assessment studies.