Concurrent infection of a Patas monkey (Erythrocebus patas) by Citrobacter freundii and Trichuris trichiura

Concurrent infection of Citrobacter freundii and Trichuris trichiura in a Patas monkey (Erythrocebus patas) is reported. A synergistic effect of both organisms contributing to host mortality in this case is suggested.     

Production of methionine γ- lyase in recombinant Citrobacter freundii bearing the hemoglobin gene

The production of antileukemic enzyme methionine γ-lyase (MGL) in distinctly related bacteria, Citrobacter freundii and in their recombinants expressing the Vitresocilla hemoglobin (VHb) has been studied. This study concerns the potential of Citrobacter freundii expressing the Vitreoscilla hemoglobin gene (vgb) for the methionine γ- liyase production. Methionine γ- liyase production by Citrobacter freundii and its vgb(-) and vgb(+) bearing recombinant strain was studied in shake-flasks under 200 rpm agitation, culture medium and 30 °C in a time-course manner. The vgb(+) and especially the carbon type had a dramatic effect on methionine γ- liyase production. The vgb(+) strain of C. freundii had about 2-fold and 3.1-fold higher levels of MGL than the host and vgb(-) strain, respectively.     

弗劳地枸橼酸杆菌的临床分布及耐药特性分析

目的了解弗劳地枸橼酸杆菌临床分离株的分布特点,探讨其耐药规律,为临床防治其感染提供帮助。方法常规方法进行菌株分离,VITEK-32型或VITEK-2全自动微生物分析仪进行菌株鉴定,K-B法进行药物敏感性试验,采用WHONET 5.5软件分析数据。结果 2007年6月至2009年12月从各种感染性标本中共分离到47株弗劳地枸橼酸杆菌,呼吸道标本占绝大多数,达51.1%(24/47),其次为脓液和尿液,分别为23.4%(11/47)和12.8%(6/47)。该菌种对氨苄西林和头孢唑啉的耐药性最严重,耐药率分别为92.6%和91.9%,其次是氨苄西林/舒巴坦、头孢西丁、头孢噻肟、左氧氟沙星及复方磺胺甲口恶唑,耐药率均45%,耐药率较低的有亚胺培南和阿米卡星,耐药率分别为8.3%和8.6%。结论弗劳地枸橼酸杆菌可引起患者多部位感染,下呼吸道是其主要感染部位,该菌种耐药性较严重,亚胺培南和阿米卡星对其有较强的抗菌活性。     

Dietary, bacterial, and host genetic interactions in the pathogenesis of transmissible murine colonic hyperplasia

Transmissible murine colonic hyperplasia, cuased by a variant of Citrobacter freundii (4280). was shown to be modified by diet and by host strain and species. Four different diets fed to mice inoculated with C frundii 4280 were found to have a significant but varying influence on the severity of hyperplasia. Diet also influenced the colonic crypt height of uninoculated, control mice. F344 rats, Syrian hamsters, and NIH Swiss [N:(S)], C57BL/6J, C3H/HeJ, and DBA/2J mice were inoculated with C freundii 4280. Marked strain differences were noted in the mice in mortality and severity of the colonic hyperplasia. The NIH Swiss mice had the greatest and the C57BL/6J mice had the least mucosal hyperplasia. The rats and hamsters did not develop disease or maintain infection after inoculation with the organism. Twenty isolates of Citrobacter from a range of biologic sources were inoculated into susceptible mice, but only mice inoculated with C freundii 4280 developed the disease.     

A note on novobiocin in XLD and HE agars: the optimum levels required in two commercial sources of media to improve isolation of salmonellas

Media containing novobiocin were tested for their selectivity for salmonelias. The optimum concentrations of novobiocin that gave the greatest percentage recovery without altering the colony morphology were 7 μg/ml in XLD Agar (Oxoid) and 40 μg/ml in HE Agar (Oxoid). At these concentrations some strains of Proteus mirabilis were suppressed and those that did survive did not produce hydrogen sulphide. The addition of novobiocin altered the colony morphology of Citrobacter freundii and Escherichia coli. Salmonella typhi was not used in this investigation and isolation of this pathogen on novobiocin supplemented media is questionable.     

某高校学生肠道菌群初步调查

目的 探讨在校大学生肠道菌群的分布,为预防肠道致病菌导致的感染提供科学依据。方法 取新鲜粪便标本,接种于肠道选择平板,筛选正常菌群、肠道致病菌和机会致病菌,以K-B法确定其药物敏感性。结果 大学生肠道菌群以克雷伯杆菌、费劳地枸椽酸杆菌、阴沟肠杆菌及白色念珠菌较多见,男性多见于女性,差异有显著性（P＜0.05）。经常校外就餐者肠道致病菌和条件致病菌检出率较高,与偶有校外就餐者相比,差异有显著性（P＜0.01）。结论 安徽理工大学医学院大学生肠道菌群以费劳地枸椽酸杆菌、阴沟肠杆菌、克雷伯杆菌及白色念珠菌较多见,并就餐方式密切相关。克雷伯杆菌耐药谱较广,应引起足够重视。     

一株弗劳地枸橼酸杆菌中检出新ampC基因

目的探讨1株耐亚胺培南弗劳地枸橼酸杆菌的耐药机制。方法采用浓度梯度法（Etest）检测对抗菌药物的最低抑菌浓度（MIC）。通过金属酶初筛试验（协同法）检测金属酶;改良Hoged试验检测碳青霉烯酶;头孢西丁三维试验检测AmpC酶;聚合酶链反应（PCR）检测耐药基因;DNA测序决定基因型;接合试验检测耐药基因的转移性。结果弗劳地枸橼酸杆菌临床分离株NC118对亚胺培南的MIC为〉16μg/ml,金属酶初筛试验阴性,Hoged表型确证试验碳青霉烯酶阳性,AmpC酶阳性,PCR扩增及测序显示含有blaKPC-2、blaAmpC基因,该菌株所产AmpC酶基因与CMY-45型AmpC酶（GenBank：ACU00152.1）比较有5个氨基酸发生了改变,该blaCMY-2-like基因为一个新型的AmpC酶基因。结论在弗劳地枸橼酸杆菌中发现一种新的ampC基因（blaCMY-49）。     

Adenovirus pneumonia in guineapigs: an experimental reproduction of the disease

The recently described virus-induced pneumonia in guineapigs (Naumann et al., 1981) was experimentally reproducible in newborn animals, though not in preadult animals. Baby hamsters and newborn rats were also not susceptible to infection. 10 of 11 infected newborn guineapigs developed pathological changes identical with those found in spontaneous cases. The incubation period was from 5 to 10 days. The agent could not be cultivated in vitro, and therefore no applicable serological tests could be established. The morphology of the virus, its intranuclear location, the course of the disease and the histopathological and ultrastructural changes strongly suggest that the virus is an adenovirus specific for guineapigs. The virus did not cross-react with human or fowl adenoviruses. It was ether resistant and non-oncogenic in baby rats and hamsters. During a 5-year period we registered a total of 51 spontaneous death cases diagnosed as adenovirus pneumonia in our experimental guineapigs, 4 from own breeding colony.     

A gene encoding L-methionine gamma-lyase is present in Enterobacteriaceae family genomes: identification and characterization of Citrobacter freundii L-methionine gamma-lyase

Citrobacter freundii cells produce L-methionine gamma-lyase when grown on a medium containing L-methionine. The nucleotide sequence of the hybrid plasmid with a C. freundii EcoRI insert of about 3.0 kbp contained two open reading frames, consisting of 1,194 nucleotides and 1,296 nucleotides, respectively. The first one (denoted megL) encoded L-methionine gamma-lyase. The enzyme was overexpressed in Escherichia coli and purified. The second frame encoded a protein belonging to the family of permeases. Regions of high sequence identity with the 3'-terminal part of the C. freundii megL gene located in the same regions of Salmonella enterica serovar Typhimurium, Shigella flexneri, E. coli, and Citrobacter rodentium genomes were found.     

患病大鲵中弗氏柠檬酸杆菌的分离与鉴定

【目的】确定导致大鲵(Andrias davidianus)细菌性感染死亡的病原。【方法】从大鲵肝脏中分离细菌,通过Biolog微生物自动鉴定系统及分子生物学方法对纯培养的细菌进行鉴定,再用大鲵和鲫鱼分别进行人工感染试验,以确定分离菌的致病性,同时对分离到的病原菌进行药物敏感试验。【结果】从患病大鲵肝脏中分离到一株致病菌JZ01,经人工感染健康大鲵,可复制与自然发病相同的症状,且从人工感染病鲵体内再次分离到相同的病原菌。该致病菌对健康鲫鱼也有致病性。经Biolog微生物自动鉴定系统的鉴定,以及进一步的16S rDNA基因序列和系统发育分析都表明,此致病菌为弗氏柠檬酸杆菌。药物敏感性试验表明,该菌株对氨曲南、头孢三嗪、先锋噻肟等9种药物高度敏感。【结论】弗氏柠檬酸杆菌是大鲵的一种致病菌。本文在国内外首次报道了该菌对大鲵具有致病性。     

Genetic regulation of variable Vi antigen expression in a strain of Citrobacter freundii.

Certain strains of the genus Citrobacter exhibit a variable expression of the Vi surface antigen that appears to involve a special mechanism for regulation of gene expression. Two nonlinked chromosomal loci, viaA and viaB, are known to determine nonvariable Vi antigen expression in strains of Salmonella. To confirm the presence of analogous loci in Citrobacter and to ascertain whether either of them is involved in variable Vi antigen expression in this organism, donor strains were constructed from Citrobacter freundii WR7004 and used to transfer their Vi antigen-determining genes to ViaA- and ViaB- Salmonella typhi recipient strains. Vi antigen expression in C. freundii was found to be controlled by loci analogous to the Salmonella via genes. S. typhi recipients of the C. freundii viaA+ genes were restored to the full, continuous expression of the Vi antigen normally seen in S. typhi. Thus, the C. freundii viaA genes appeared to play no role in the variable expression of the Vi antigen. In contrast, S. typhi recipients of the C. freundii viaB+ genes exhibited the rapid, reversible alternation between full Vi antigen expression and markedly reduced Vi antigen expression that was seen to occur in the C. freundii parent. The C. freundii viaB locus was thus identified as the one whose genes are regulated so as to produce variable Vi antigen expression. Genes determining another C. freundii surface antigen, the synthesis of which is not affected by the mechanism regulating Vi expression, were coinherited with the C. freundii viaB+ genes. An invertible, insertion sequence element located within the C. freundii viaB locus is proposed to account for the regulation of variable Vi antigen expression.     

Taxonomy of Citrobacter rods found in human specimens

The aim of this study was the identification of 181 Citrobacter strains on the basis of the recently proposed taxonomic changes of Brenner. All strains were isolated from diarrhoeic patients; 124 strains were originally sent for identification to Laboratory of Enterobacteriaceae DB NIH, 57 strains was isolated in Czech Republic. Citrobacter isolates were initially identified as C. koseri (3 strains), C. amalonaticus (1 strain) or as members of the C. freundii complex (177 strains). Additionally some biochemical tests were performed. The ability to grow in medium containing KCN, lysine decarboxylase production, lactose fermentation and PYR test were examined. Strains belonging to the C. freundii complex were identified to the species level by biochemical methods on the basis of the results of Brenner, who found some tests to be useful in separating Citrobacter species. These test included citrate and acetate utilization, arginine dihydrolase and ornithine decarboxylase activities, motility, urease production, esculin hydrolysis, and acid production from sucrose, dulcitol, melibiose, raffinose and salicin. On the basis of the criteria described above, 96.6% of the strains tested could be assigned to one of the recently named species of C. freundii complex. Using biochemical tests suggested by Brenner we were able to identify Citrobacter strains members of newly recognised species. A five-test system is proposed to identify the most frequently encountered species currently residing in the C. freundii complex.     

Cefamandole resistance transfer in bacterial strains from two newborn units

Transfer of Cefamandole resistance was demonstrated from strains of Citrobacter freundii as well as from individual strains of Enterobacter cloacae, Acinetobacter anitratus and Klebsiella pneumoniae isolated from patients in two newborn units. In Citrobacter freundii, Cefamandole resistance was transferred always with Cephalotin resistance as well as with a TEM-like beta lactamase (conferring resistance to Ampicillin, Carbenicillin and Azlocillin). Citrobacter freundii strains from Hospital I were completely susceptible to gentamicin, while strains of other species, resistant to Cefamandole plus Cephalotin, were resistant to Gentamicin as well, and transferred this resistance, too. In one Enterobacter cloacae strain from Hospital I, Cefamandole resistance could be separated from resistance to Cephalotin, but only in clones selected with gentamicin and not with any of the cephalosporins. Acinetobacter anitratus strain was also resistant to Cefotaxime, but did not transfer this resistance. It might be concluded that special nosocomial bacteria may carry plasmids conferring a transferable type of resistance to Cefamandole together with resistance to classical cephalosporines. Second cycle of transfers, i.e. between two variants of E. coli K-12 strains confirmed the contransferability of Cefamandole and Cephalotin resistance.     

Resolution of high-molecular-weight components in lipopolysaccharides of Escherichia coli, Morganella morganii, Citrobacter freundii and Citrobacter diversus strains with sodium dodecyl sulfate polyacrylamide gels

The use of 0.5% sodium dodecyl sulfate in polyacrylamide separation gels allowed the resolution in several bands of high-molecular-mass components in smooth lipopolysaccharide of bacterial outer membrane from Escherichia coli, Morganella morganii, Citrobacter freundii and Citrobacter diversus. With or without 0.1% SDS, however, such a result was not possible.     

Citrobacter freundii septicemia in a stranded newborn Cuvier's beaked whale (Ziphius cavirostris)

Citrobacter freundii, a gram-negative enterobacterium, may cause fatal septicemia in humans and animals. Its potential pathogenic role in cetaceans (bottlenose dolphins and beluga whales) has been hypothesized. Here we describe fatal C. freundii septicemia in a stranded newborn Cuvier's beaked whale (Ziphius cavirostris).     

Identification of the active site of Citrobacter freundii beta-lactamase using dansyl-penicillin

The active site sequence of a beta-lactamase encoded by chromosomal gene(s) in Citrobacter freundii GN346 was determined using dansyl-penicillin as a fluorescent probe. The tryptic digest of the labelled enzyme gave a fluorescent peptide containing 22 amino acids. The sequence of this peptide was identical to the consensus sequence of class C beta-lactamases, Gly-Ser-X-Ser-Lys. The residue labelled was the serine adjacent to the glycine. The active site sequence corresponded to positions 46-67 of the entire sequence of the Citrobacter freundii beta-lactamase determined on the basis of the DNA sequence of the structural gene [(1986) Eur. J. Biochem. 156, 441-445]. The labelled serine corresponded to Ser-64.     

Protective properties of Vi-antigen preparations as dependent on their adhesin content

Adhesins contained in the preparation of Vi-antigen have been found to enhance its immunogenic and protective properties. In the preparations of Vi-antigen obtained from Salmonella typhi and Citrobacter freundii the presence of two antigenic determinants has been revealed. One of them is associated with the Vi-receptor and the other determinant, with adhesin. Both determinants take part in the protection of mice from Salmonella infection.     

Evaluation of Rambach agar for the differentiation of Salmonella species from other Enterobacteriaceae

Rambach agar (Merck) was evaluated for its reliability as a selective diagnostic medium for the differentiation of Salmonella species from other Enterobacteriaceae. Twenty-five Salmonella strains were cultured on each of three agar media, Rambach (RAM), xylose lysine desoxycholate (XLD) and bismuth sulphite (BSA). Typical, easily interpreted reactions and colony morphologies were achieved for 23 strains on RAM and BSA and 17 on XLD. Of 135 other Enterobacteriaceae cultured on RAM, 134 gave characteristics which differentiated them from Salmonella . One strain which looked like Salmonella was identified as Citrobacter freundii . Rambach agar has potential as a supplementary agar in testing foods for Salmonella , but as with other selective diagnostic agars, it has limitations.     

Characterization of the Citrobacter freundii phoE gene and development of C. freundii-specific oligonucleotides

The phoE gene of Citrobacter freundii, encoding a pore-forming outer membrane protein, was cloned and its nucleotide sequence was determined. The homologies in terms of identical amino acids between the C. freundii PhoE protein and those of Escherichia coli, E. cloacae and Klebsiella pneumoniae were 90%, 86% and 84%, respectively. Two synthetic oligonucleotides, corresponding to hypervariable, cell surface-exposed regions of the protein, were tested for their specificity in polymerase chain reactions. They were specific for the species C. freundii, i.e., no reaction was detected with 35 non-C. freundii strains tested, including 17 Salmonella, two C. amalonaticus and three C. diversus strains, whereas all five C. freundii strains tested were correctly recognized.     

Cloning of a haemolysin from Citrobacter freundii and its expression in phylogenetically related bacteria

Abstract The determinants for a haemolysin from an extraintestinal isolate of Citrobacter freundii have been cloned and expressed in both Escherichia coli K12 and phylogenetically related bacteria. Compared with E. coli , where the haemolytic determinants are encoded in 7.5 kb, the hemolysin determinants of C. freundii are located on a 2.5-kb Hin dIII fragment in the recombinant plasmid PJP71. Chicken embryo tests indicate that this haemolysin does contribute to the pathogenicity of C. freundii .