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PubMed1991

Saccharide-protein covalent conjugates: immunochemical characterization of Citrobacter 036 core oligosaccharide-tetanus toxoid conjugates.

Core oligosaccharides (complete and incomplete) isolated from Citrobacter 036 lipopolysaccharide were covalently conjugated with tetanus toxoid. Serological examination of the Citrobacter 036 core oligosaccharide-tetanus toxoid conjugates showed that they are strong immunogens. The monospecific anti-conjugate sera prepared by immunization of rabbits, were used to study the antigenic relations between lipopolysaccharide core regions of 8 strains of Citrobacter. Immunoelectrophoresis, immunoblotting and quantitative microprecipitation were performed in the experiments.

Animals↗
PubMed1996

Iron utilization studies in Citrobacter species.

Seventy-one strains of Citrobacter were screened for iron scavenging mechanisms by biologic and chemical assays. Essentially all citrobacteria (70/71) were found to elaborate enterobactin-like siderophores by both biologic and chemical assays, however only c. koseri (C. diversus) was found to produce aerobactin. The concentration of ethylenediamine di(o-hydroxyphenylacetic acid) (EDDA) required to inhibit the growth of individual Citrobacter strains by depleting free iron ranged from 250 micrograms/ml to 100 micrograms/ml. Iron utilization studies of selected citrobacter isolates indicated that hemin and hematin could reverse the effects of iron limitation on growth under iron-stressed conditions (1000 micrograms/ml of EDDA). Two C. koseri strains grown under iron-restricted conditions showed similar changes in their whole cell protein profiles including induction of high molecular mass proteins (72-83 kDa) which may play a role in iron acquisition under iron-stressed conditions. The collective results support an additional virulence-associated mechanism for C. koseri strains which may help explain the greater pathogenic potential this group has for causing serious extraintestinal disease in humans.

Bacterial Proteins↗
PubMed1999

Citrobacter freundii invades and replicates in human brain microvascular endothelial cells.

Neonatal bacterial meningitis remains a disease with unacceptable rates of morbidity and mortality despite the availability of effective antimicrobial therapy. Citrobacter spp. cause neonatal meningitis but are unique in their frequent association with brain abscess formation. The pathogenesis of Citrobacter spp. causing meningitis and brain abscess is not well characterized; however, as with other meningitis-causing bacteria (e.g., Escherichia coli K1 and group B streptococci), penetration of the blood-brain barrier must occur. In an effort to understand the pathogenesis of Citrobacter spp. causing meningitis, we have used the in vitro blood-brain barrier model of human brain microvascular endothelial cells (HBMEC) to study the interaction between C. freundii and HBMEC. In this study, we show that C. freundii is capable of invading and trancytosing HBMEC in vitro. Invasion of HBMEC by C. freundii was determined to be dependent on microfilaments, microtubules, endosome acidification, and de novo protein synthesis. Immunofluorescence microscopy studies revealed that microtubules aggregated after HBMEC came in contact with C. freundii; furthermore, the microtubule aggregation was time dependent and seen with C. freundii but not with noninvasive E. coli HB101 and meningitic E. coli K1. Also in contrast to other meningitis-causing bacteria, C. freundii is able to replicate within HBMEC. This is the first demonstration of a meningitis-causing bacterium capable of intracellular replication within BMEC. The important determinants of the pathogenesis of C. freundii causing meningitis and brain abscess may relate to invasion of and intracellular replication in HBMEC.

Actin Cytoskeleton↗
PubMed1981

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.

Antigens, Bacterial↗
PubMed1995

Ability of commercial identification systems to identify newly recognized species of Citrobacter.

The genus Citrobacter was recently determined to contain 11 genetically distinct species. In addition, the International Committee on Systematic Bacteriology no longer recognizes C. diversus and has, instead, validated the name C. koseri in its place. The 11 species are C. freundii, C. koseri, C. amalonaticus, C. farmeri, C. youngae, C. braakii, C. werkmanii, C. sedlakii, and three unnamed groups, genomospecies 9, 10, and 11. To determine the ease with which some identification systems could respond to these changes, we evaluated five systems for their potential ability to recognize current species in the genus Citrobacter. A simple dichotomous key using conventional biochemicals is presented that may be helpful to presumptively identify Citrobacter strains.

Citrobacter↗
PubMed1984

Characterization of anti-Citrobacter 036 specific polysaccharide monoclonal antibodies.

Monoclonal mouse antibodies specific for the 0 antigen of Citrobacter 036, a homopolymer of beta (1----2)-linked 4-deoxy-D-arabinohexose, were generated by the hybridoma technique. Balb/c mice were immunized with killed whole-cell vaccine and initial selection of active clones was based on enzyme-linked immunosorbent assay (ELISA) employing purified lipopolysaccharide (LPS). Concentrated culture supernatants from selected hybrid cultures were used to identify 10 0-antigen specific monoclonal antibodies using the multiple criteria of immunoprecipitation of 0 chains and LPS, inhibition by acid hydrolyzed 0 chains in the screening ELISA, and antibody class analysis. Four monoclonal antibodies were chosen for further study using dose-dependent 0-chain inhibition of ELISA and passive hemagglutination, passive hemolysis, and bacterial agglutination titres. When screened with Citrobacter serotypes known to contain the sugar 4-deoxy-D-arabinose, passive hemagglutination tests showed that the two monoclonal antibodies examined possessed titres which could be correlated with the reported 4-deoxy-D-arabinohexose content of the respective LPS's. This sugar is an antigenically important unit of several Citrobacter serotypes as defined by these well-characterized monoclonal antibodies.

Animals↗
PubMed1977

Endocarditis due to Citrobacter diversus developing resistance to cephalothin.

A 43-year-old man was admitted with acute bacterial endocarditis. Citrobacter diversus susceptible to cephalothin was isolated from blood cultures. Citrobacter diversus was later isolated from the aortic valve cusps at surgery, but this isolate was resistant to cephalothin. Laboratory testing showed that the Citrobacter diversus recovered from blood cultures was capable of producing mutants highly resistant to cephalothin.

Adult↗
PubMed1979

[Metabolism of dicarboxylic amino acids and their amides in bacteria of the genus Citrobacter].

In 58 Citrobacter strains the pathways of the utilization of dicarbonic amino acids and their amides were studied. These organisms were found to be incapable of decarboxylating glutaminic and asparaginic acids, as well as their amides. All the strains could actively desamidizate asparagine. Not all of these strains showed glutaminase activity. Aspartate-aminotransferase occurred twice as often as alanine-aminotransferase, the level of activity being approximately the same. The Citrobacter strains desamidizated asparaginic acid with great constancy, but only in 1/3 of them this reaction occurred via an aspartase route. The desamidization of asparaginic acid in Citrobacter seemed to proceed in different ways. The desamidization of glutaminic acid was observed only in a part of the strains, and the reaction proceeded less actively.

Amides↗
PubMedDate not supplied

[Report on Citrobacter strains having antigenic relationship with "E. coli", and their characteristics (author's transl)].

During a research done on the diffusion of enteropathogenic E. coli in a children's community, 24 strains of Citrobacter have been isolated. By agglutination and agar-gel diffusion techniques, they looked to have some somatic antigens in common with those serogroups of enteropathogenic E. coli. The results were as follows: 14 strains were correlated with the serogroup O111; 9 strains with the serogroup O125 and 1 strain with the serogroup O55. The isolation of these strains has been made at the same period when we have found out the E. coli of homologous serogroups, even if they didn't belong to the same subjects. The colicine typing and sensibility to antibiotics tests made both on Citrobacter strains and on E. coli ones of homologous serogroups haven't pointed out other characteristics of identity. Furthermore, antigenic relationships between the 24 strains of Citrobacter and different serogroups of Salmonella have been demonstrated, that is: the strains containing the somatic antigen O111 were correlated with the serogroup O35; the strains having the somatic antigen O125, with the serogroup O6, 14, 24 and the strain containing the somatic antigen O55, with the serogroup O50. The presence of these strains in normal subjects only, gives a further witness that their role in enteric infections remains to be demonstrated.

Anti-Bacterial Agents↗
PubMed1986

[Isolation and properties of Citrobacter bacteriophages].

Four phages differing in their antigenic properties, thermosensitivity and spectrum of action have been obtained from Citrobacter lysogenic cultures. To prepare the suspension of Citrobacter phages, phagolysates may be treated with chloroform 1:10 for 30 minutes. The isolated phages have proved to be highly specific. The possibility of distinguishing Citrobacter cultures by means of the phages under study has been shown.

Animals↗
PubMed1976

[Live enteric typhoid vaccine consisting of a Vi-negative double-dependent mutant of S. typhi and a Vi-positive strain of Citrobacter].

The authors present experimental data on the study of the living enteral vaccine against the typhoid infection from the Vi-negative strain of salmonella with a double-dependence by streptomycin and purine, and from the Vi-positive strain -- citrobacter 5396/38. The method of immunoelectrophoretic analysis showed an indenticity of the O- and H-antigens of the doubledependent mutant with the O- and H-antigens of the typhoid strains of bacteria (Ty2-4446 and 5501). A sufficiently marked immunological reaction was revealed in the tests of antibody formation and in the study of the preventive activity of the sera of the immunized rabbits. The efficacy of the enteral immunization with the associated vaccine consisting of a doubledependent mutant of typhoid bacilli and the citrobacter strain in the doses tested (a 6-fold immunization) was demonstrated in experiments on albino mice. Association in one preparation of the cultures under study did not lead to any changes in the immunogenic properties of these strains. The cells of the mutant strain administered per os gave a positive culture (from the mouse organism) only in the course of the first 24 hours, in difference from the citrobacter strain which gave a positive culture in the course of 14 days.

Animals↗
PubMed1983

[Comparison of antibacterial potencies of oral and parenteral antibiotic preparations against Escherichia coli, Klebsiella, Citrobacter, and Proteus isolated from urinary tract infections (3: 1981) 1. Susceptibility distribution].

In vitro activities of antibacterial agents against E. coli, Klebsiella, Citrobacter and Proteus which were isolated from patients with urinary tract infections at 8 hospitals in Japan, were investigated by dilution broth method using MIC 2000 (Dynatec) during July to October in 1981. The summarized results are as follows: Among oral antibacterial agents, MPC and PPA have showed potent antibacterial activities against E. coli and Klebsiella. In vitro activities of oral antibacterial agents against Proteus and Citrobacter showed not so potent. Among the first and second generation's parenteral antibacterial agents, CTM has showed potent antibacterial activities against E. coli and Klebsiella. Among the third generation's parenteral antibacterial agents, CMX, CTX and CZX have showed potent antibacterial activities against E. coli, Klebsiella, Proteus and Citrobacter.

Anti-Bacterial Agents↗
PubMed1984

Survey of resistance to metals and volatilization activity of Hg-resistant R plasmids in Citrobacter isolated from clinical lesions in Japan.

Clinical isolates of Citrobacter (277 strains) were studied for the resistance to four metals and four drugs. The distribution patterns of their susceptibility to Hg, Cd and As clearly revealed two peaks, but only a single peak of resistance to Pb. The frequencies of resistance to Hg, Cd, As, SM, TC, CP and KM were 31.8, 94.2, 57.8, 51.3, 44.8, 35.7 and 28.9%, respectively. And we selected 88 mercury resistant strains, and they were tested for their ability to transfer the resistance to the mercury and drug sensitive recipients of E. coli K12-ML1410-Nx and E. coli JE17-Rif. Among 88 strains of Hg resistant Citrobacter, 80 R plasmids with Hg resistance could be demonstrated. It should be noted that transferable R plasmids with Hg resistance were demonstrated in 91% of the Hg-resistant isolates. Furthermore, we tested the volatilization of mercury by strains containing these mercury resistance plasmids, by using radioactive 203Hg2+. All of these isolates of Citrobacter have volatilization activity of Hg2+. Also, all of these volatilization activity is inducible.

Anti-Bacterial Agents↗
PubMed1984

Immunochemical characterization of lipopolysaccharides of Citrobacter chemotypes CC-G and CC-H.

Lipopolysaccharides of Citrobacter serotypes 04, 027 and 036 indicate strong cross-reactivity in passive hemagglutination and their O-specific chains are homopolymers of (beta 1----2)--linked 4-deoxy-D-arabinohexose. Citrobacter serotype 023 cannot be placed in chemotype CC-H, since its O-specific polysaccharide does not contain 4-deoxy-hexose. The possibility exists that 4-deoxy-D-arabinohexosyl side chains of 023-specific-polysaccharide disappeared as a result of a mutation of the parent strain. Although Citrobacter strain PCM 1487 contains 4-deoxy-D-arabinohexose and belongs to the chemotype CC-G, it cannot be included to the serotypes 04, 027 or 036. Instead, it represents a new serotype, with O-specific polysaccharide composed of 4-deoxy-D-arabinohexose, N-acetylglucosamine and N-acetylgalactosamine.

Carbohydrates↗
PubMed1974

Biochemical and antibiotic susceptibility studies of H2S-negative Citrobacter.

Ninety-four strains of H(2)S-negative Citrobacter were biochemically characterized and their antibiograms were determined. The antibiograms demonstrated not only a difference from Enterobacter cloacae but also a difference within the Citrobacter group between the indole-negative and indole-positive strains. These differences were statistically significant and emphasize the importance of the indole reaction as an aid to speciation of the H(2)S-negative Citrobacter.

Anti-Bacterial Agents↗
PubMed2000

Serological cross-reaction between the lipopolysaccharide O-polysaccharaide antigens of Escherichia coli O157:H7 and strains of Citrobcter freundii and Citrobacter sedlakii.

A strain of Citrobacter sedlakii showing serological cross-reaction with Escherichia coli O157 antisera was demonstrated to produce a lipopolysaccharide O-antigen having an identical structure with that of the E. coli O157 O-antigen. A strain of Citrobacter freunndii showing similar cross-reaction with E. coli O157 specific monoclonal antibody was shown to produce a lipopolysaccharide O-antigen composed of a trisaccharide repeating unit having the structure [ 2)-alpha-D Rhap-(1-3)-beta-D-Rhap-(1-4)-beta-D-Glcp-(1-]. This O-antigen differs from that of the E. coli O157 O-antigen and also lacks a component 2-substituted 4-amino-4,6-dideoxy-alpha-D-mannopyranosyl residue implicated as the common epitope in the lipopolysaccharide O-antigens of previously investigated bacterial species showing serological cross-reactivity with E. coli O157 antisera. The C freundii O-antigen presents an interesting example of structural mimicry within a bacterial polysaccharide antigen.

Agglutination Tests↗
PubMed1980

Neonatal intracranial abscess: two cases caused by Citrobacter and a literature review.

Intracranial abscesses are uncommon in the newborn. Observation of 2 infants and a review of the literature reveal that the offending organism was a Citrobacter in 12 of the 16 documented cases. In the Neonatal Meningitis Cooperative Study this organism was responsible for meningitis in only 4%. However, an analysis of all published cases of neonatal Citrobacter meningitis reveals a 42% incidence of intracranial abscess. Accordingly, early identification by computerized tomography is important in facilitating prompt surgical therapy.

Brain Abscess↗
PubMedDate not supplied

Bifocal cervical spondylodiscitis due to Citrobacter diversus.

Spondylodiscitis due to Citrobacter diversus is rare. An unusual case of bifocal cervical spondylodiscitis following transurethral prostatectomy is reported. C. diversus was detected by urinary cultures and locally by intervertebral disc puncture. Satisfactory recovery occurred after treatment with imipenem and amikacin, and then imipenem alone. Citrobacter infections are still rare in adults but are increasing in immunocompromised patients and sometimes occur in healthy subjects following surgery.

Aged↗