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PubMed1978

[Flagellar antigens of E. coli serologically interrlelated to H40, 41 and H41, 42, 43 flagellar antigens of Citrobacter. New H-antigeny E. coli i Citrobacter].

The authors confirmed the reference of the test strains H13 (P6c) and H22 (A231a) of the international collection of E. coli to Citrobacter; their antigenic formula was established. As shown, strains P6c possessed a variety of the H-antigen which was not described in Citrobacter earlier, designated as H41a, 97. Three types of flagellar antigens characterized by the presence of an interrelationship with the partial factor H41 of the flagellar Citrobacter antigens were revealed in E. coli; the partial composition of H-antigenic components common for E. coli and Citrobacter was studied. Two of three new varieties of the E. coli H-antigen revealed was characterized by a cross correlation and a relation to the standard H19 E. coli antigen. The strain with the third variety of the H-antigen was capable of forming the H-antigenic mutants which acquired the antigenic component identical to the standard H16 E. coli antigen. E. coli strain is recommended for the replacement of the strain P6c in the International collection of E. coli.

Agglutinins↗

PubMed1975

Citrobacter koseri. I. An extended antigenic scheme for Citrobacter koser (syn. C. diversus, Levinea malonatica).

The names Citrobacter koseri, Levinea malonatica and Citrobacter diversus are synonymous. As a result of the study of representative strains of these organisms an antigenic scheme comprising seven O antigens has been proposed. The examination of a further 165 strains from clinical sources suggests that an additional seven antigens should be included in the scheme. The serological and biochemical reactions of the test strains for all 14 O antigens are described.

Agglutination Tests↗

PubMed1978

Citrobacter O-antigens: structure of the O-antigenic polysaccharide from Citrobacter sp. 396.

The structure of the O-specific polysaccharide moiety of the lipopolysaccharide from Citrobacter 396 was elucidated by composition, methylation, and periodate oxidation studies. The repeating unit consists of four 2-linked mannoses and one 3-linked N-acetylglucosamine. One of the mannose units is substituted at C3 with alpha-glucose, and one is substituted at C3 with alpha-(2-O-acetyl)-abequose. All the mannosyl linkages appear to have the beta-configuration; the N-acetylglucosaminyl linkage has the alpha-configuration. In bacterial agglutination and passive hemagglutination in some Salmonella antisera, Citrobacter 396 as well as its O-antigenic lipopolysaccharide expressed the serological factors 5 and 6. In corroboration of our structural studies, this showed the presence of alpha-(2-O-acetyl)-abequosyl-1,3-mannose (factor 5) and alpha-glucosyl-1,3-mannose (factor 6).

Antigens, Bacterial↗

PubMed1975

Citrobacter koseri. II. Serological and biochemical examination of Citrobacter koseri strains from clinical specimens.

165 strains of Citrobacter koseri isolated from clinical specimens were studied and their biochemical reactions determined. They were examined serologically by means of a scheme consisting of 14 O antigens. The sources of the clinical specimens were tabulated and the epidemiological information was summarized. The clinical significance of these findings is discussed.

Antigens, Bacterial↗

PubMed1978

Clinical significance of citrobacter isolates.

Little is know about the clinical significance of isolating Citrobacter in the clinical laboratory. During a one-year period, 116 Citrobacter isolates were obtained from 77 patients with 83 suspected infectious episodes. The majority of the suspected infectious episodes involved the urinary tract (45%) or respiratory tract (41%). Citrobacter diversus was associated with 42% of the episodes, Citrobacter freundii with 29%, and Citrobacter species with 29%. In 42% of the suspected infectious episodes, the presence of Citrobacter was considered clinically significant; in the others, the significance of the Citrobacter isolates was indeterminate or considered to be commensal. Two thirds of the significant infections were hospital-acquired. Most patients (73%) from whom Citrobacter was cultured had underlying diseases or factors predisposing to infection. These data suggest that Citrobacter is a cause of significant opportunistic nosocomial infection in the hospital.

Adult↗

PubMed2025

Global emergence and transmission dynamics of carbapenemase-producing Citrobacter freundii sequence type 22 high-risk international clone: a retrospective, genomic, epidemiological study.

BACKGROUND: Carbapenemase-producing Citrobacter (CPC) species have recently been recognised as emerging pathogens associated with nosocomial infections in humans. The increased rate of Citrobacter freundii infections is a public health concern and there is a paucity of genomic data regarding its global transmission dynamics. We aimed to characterise the genetic features of CPC species, and their associated carbapenemase-encoding plasmids, obtained from hospitalised patients in China and from publicly available global data, with a particular focus on high-risk clones. METHODS: This was a retrospective, genomic epidemiological study of CPC species obtained from a tertiary hospital in Zhejiang Province, China, from March 5, 2013, to March 5, 2023. We used antimicrobial susceptibility testing, short-read and long-read whole-genome sequencing, phylogenomic analysis, and plasmid structure analysis. A global dataset of complete plasmid sequences encoding blaKPC, blaNDM, and blaIMP was constructed from the National Center for Biotechnology Information (NCBI) RefSeq database to provide insights into their diversity and distribution. All carbapenemase-producing Citrobacter freundii genomes from the NCBI GenBank database were incorporated in the comparative genomic analyses. Bayesian phylogeographical analysis and growth rate assays were carried out to characterise the high-risk C freundii sequence type (ST) 22 clone. FINDINGS: 1724 Citrobacter species isolates were collected from diverse clinical specimens, with 48 identified as CPC species. Citrobacter koseri (22 [46%] of 48) and C freundii (20 [42%]) were the predominant CPC species. Comparative analysis found C freundii carried significantly higher median numbers of plasmid replicons (5·0 [IQR 3·3-6·0] vs 2·0 [2·0-3·0]; p<0·0001) and acquired antimicrobial resistance genes (12·0 [7·3-15·8] vs 3·0 [3·0-5·3]; p<0·0001) than did C koseri. Molecular characterisation identified Inc-type plasmids, In823::Kl.pn.I3/In1589-like/In837-like integrons, Tn6296/Tn125/Tn5060 transposons, and insertion sequences (eg, IS26, IS3000, IS5, ISAba125, ISCR1), collectively facilitating the dissemination of carbapenemase genes. Global analysis of 3126 carbapenemase-encoding plasmids found epidemic plasmids with broad host ranges and global diversity. Phylogenetic investigation of predominant carbapenemase-encoding plasmids showed their persistence across geographical regions, temporal spans, and Enterobacterales species, exhibiting high genetic similarity to our clinical plasmids. A phylogenetic tree of 726 global carbapenemase-producing C freundii genomes showed that ST22 (227 [31·3%]) represents the predominant multidrug-resistant clone across community, health-care, and environmental niches. Transmission across continents contributes to the global predominance of the ST22 clone, which carries a high load of resistance genes (median 15·0 [IQR 11·0-17·0] vs 12·0 [3·0-16·0]; p<0·0001) and enhanced plasmid maintenance capacity (median replicons 5·0 [IQR 4·0-7·0] vs 4·0 [3·0-6·0]; p<0·0001) relative to non-ST22 clones. INTERPRETATION: Our study provides evidence to suggest that Citrobacter species are emerging carriers of carbapenem-resistance genes. These findings provide insight into the population structure of CPC species and highlight C freundii ST22 as a prominent high-risk international clone. FUNDING: National Natural Science Foundation of China, National Health Commission Scientific Research Fund-Zhejiang Provincial Major Health Science and Technology Plan Project, Zhejiang Province Natural Science Foundation Project, Outstanding Youth Foundation of Jiangsu Province of China, the Priority Academic Program Development of Jiangsu Higher Education Institutions, and Postgraduate Research and Practice Innovation Program of Jiangsu Province.

Citrobacter freundii↗

PubMed1977

Antimicrobial susceptibility patterns (antibiograms) as an aid in differentiating Citrobacter species.

The hydrogen sulfide-negative Citrobacter group represents a taxonomic problem. Various investigators have proposed such designations as Padlewskia, Levinea, atypical Enterobacter cloacae, H2S-negative variants of Citrobacter, Citrobacter koseri and Citrobacter diversus. This problem has been investigated with emphasis on antibiograms as a means of discrimination. Clinical isolates fitting the designation Citrobacter were studied and, using the criteria of Ewing and Davis, separated into two groups: C. diversus (40 strains) or C. freundii (25 strains). Susceptibilities to ampicillin, carbenicillin, cefazolin, cephaloridine and cephalothin were determined by the agar-dilution method. C. diversus strains were resistant to 8 mug/ml ampicillin (97.5%) and 32 mug/ml carbenicillin (87.5%), and were susceptible to 8 mug/ml cephalosporins (greater than or equal to 90%). C. freundii strains were moderately susceptible to 8 mug/ml ampicillin (25%) and susceptible to 8 mug/ml carbenicillin (92%), and were resistant to 8 mug/ml cephalosporin (greater than or equal 92%). Using these data one can separate C. diversus from C. freundii with 90% accuracy.

Ampicillin↗

PubMed1977

Distinctive electrophoretic patterns of Esterases from Levinea malonatica, Levinea amalonatica and Citrobacter.

Esterases of 42 strains of Levinea malonatica, Levinea amalonatica and Citrobacter were analysed by horizontal slab electrophoresis in polyacrylamide-agarosegel using several synthetic substrates. On the basis of esterase zymograms a distinctive pattern was established for each of the three species. Levinea malonatica was characterized by two major bands: one hydrolysing acetate esters but not butyrate esters; and the other hydrolysing alpha-naphthyl acetate and reacting weakly with alpha-naphthyl butyrate and beta-naphthyl acetate. Levinea amalonatica showed one prominent band that hydrolysed alpha-naphthyl esters and reacter weakly with beta-naphthyl esters. Citrobacter strains showed one major band that hydrolysed alpha-naphthyl esters and appeared slightly more towards beta-naphthyl esters than that of L. amalonatica. Considerable variations in electrophoretic mobility were observed among Citrobacter strains. Levinea amalonatica was less variable. In addition, one minor anodal band reacting with beta-naphthyl acetate was observed in both L. malonatica and Citrobacter. The relative molecular sizes of the major esterase bands were determined by disc electrophoresis with gels of different acrylamide concentrations. The molecular size of the major band of Citrobacter appeared to be smaller than that of the corresponding esterase band of L. amalonatica.

Citrobacter↗

PubMed1975

[Frequency of detecting bacteria of the genera Citrobacter and Hafnia in different contingents of examined adults].

A study of the incidence of bacteria of the Citrobacter and Hafnia genus in adults permitted to establish a greater occurrence of the mentioned microbes in the patients with various acute intestinal diseases in comparison with the healthy ones. Bacteria of the Citrobacter and Hafnia genus were revealed in the patients with acute intestinal diseases of obscure etiology, which often were diagnosed as gastroenteritis, enteritis, etc. Bacteria of the Citrobacter and Hafnia genus were revealed in the dysentery patients. Results of studies carried out among various healthy groups of the population indicated no significant differences in respect to the carrier state of the Citrobacter and Hafnia bacteria both within each of the groups of the persons examined and between them. Further studies directed to the investigation of the etiological role of bacteria of the Citrobacter and Hafnia genus in the pathology of enteric disturbances are necessary.

Acute Disease↗

PubMed1978

The characteristic and clinical importance of bacteria of the genus Citrobacter isolated from patients with acute intestinal infections on the territory of Volgograd.

A total of 309 Citrobacter strains isolated from patients with acute intestinal infections of obscure aetiology and from healthy subjects were investigated. Species specificity of the bacterial cultures was determined by biochemical tests recommended by the International Enterobacteriaceae Subcommittee. Citrobacter strains were titrated serologically in the reaction of agglutination on glass with a living culture and adsorbed 0-antisera. Eighteen serological 0 groups were identified; 0 groups 3, 9, 23, 1 and 8 were found most frequently. Citrobacter was isolated more frequently from patients with acute intestinal infections than from healthy subjects. Seasonal circulation of Citrobacter strains in spring and summer was established. The number of culture findings of Citrobacter in the patients increased against the background of reduction in the number of cases of bacteriologically confirmed dysentery.

Acute Disease↗

PubMed1976

Serotyping of strains belonging to the Citrobacter-Levinea group isolated from diagnostic material.

A proposal is presented for the serotyping of Citrobacter-Levinea strains: 9 serotypes for Citrobacter diversus (Levinea malonatica) and 13 serotypes for H2S-negative, indole-positive variants of Citrobacter freundii (Levinea amalonatica), which showed a considerable antigenic diversity. By means of both kinds of antiserum types 80 per cent of the strains (L. malonatica 100 per cent, L. amalonatica 72 per cent) from a series of 106 strains isolated from different diagnostic material were serologically classified. According to results presented in this paper, a direct relationship between biotype and serotype was found among the strains of biotype b for Levinea amalonatica and c for L. malonatica, which were agglutinated by the antisera prepared from biotypes b and c, respectively, only. Serotyping will evidently greatly contribute to a more perfect identification, especially of those strains that are, for various reasons, classified among so called intermediates. The importance of the Citrobacter freundii and C. diversus species in the clinical material is emphasized with a view to their increasing occurrence. Taxonomic and nomenclature questions with regard to Citrobacter-Levinea are discussed in detail.

Animals↗

PubMed1975

Massive empyema due to Citrobacter diversus.

Citrobacter diversus is a gram-negative rod member of the Enterobacteriacease family. A patient is described from whom this organism was isolated twice in pure culture from empyema fluid. Our isolates of Citrobacter diversus were resistant to ampicillin and carbenicillin and sensitive to cephalothin. Citrobacter diversus should be distinguished from Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae. This organism joins Streptococcus pyogenes, bacteroids species, anaerobic streptococci and Escherichia coli as a cause of slight pneumonia with extensive empyema.

Citrobacter↗

PubMed1978

[Resistance to antibiotics of conditionally pathogenic enterobacteria of the genera, Citrobacter and Hafnia].

Antibiotic sensitivity of 363 strains of Citrobacter and 124 strains of Hafnia isolated from patients with acute intestine infections and healthy persons was studied. It was found that 44.6 per cent of the Citrobacter isolates and 36.3 per cent of the Hafnia isolates were resistant to one or more antibiotics. Different sensitivity of the bacteria of these 2 genera of the conditionally pathogenic enterobacteria to definite antibiotics was shown. The resistant strains of Citrobacter to negramon, monomycin, levomycetin, polymyxin, streptomycin and tetracycline amounted to 3, 6.1, 24, 14.3, 24.8 and 25.9 per cent, respectively. Among the Hafnia isolates the resistant strains to negramone, levomycetin, polymyxin and tetracyline amounted to 0.8, 8.9, 29.8 and 25 per cent, respectively. All the tested strains of Hafnia were sensitive to monomycin and streptomycin. Comparison of the culture antibiotic sensitivity with respect to the resistance spectra revealed 24 and 5 types of resistance in the cultures of Citrobacter and Hafnia, respectively.

Anti-Bacterial Agents↗

PubMedDate not supplied

Citrobacter diversus at Grace Hospital, Detroit, Michigan.

Over a six-month period from December 1973 to June 1974, isolations of Citrobacter diversus were obtained from nine patients at Grace Hospital. Our initial experience was with a patient who developed pneumonitis and a massive fatal empyema due to this organism. Seven of the nine patients were 50 years of age. Three patients had an underlying malignancy. Four patients experienced significant clinical infections. Isolations in three patients were considered to be commensal, and two isolations were of indeterminate significance. Our Citrobacter diversus isolates, which can be confused with Escherichia coli, were uniformly resistant to ampicillin and carbenicillin and sensitive to the cephalosporins, tetracyclines, and gentamicin. These results agree with previous reports. Citrobacter diversus appears to be capable of causing serious clinical disease. Patients most at risk are elderly compromised hosts and infections are usually hospital acquired.

Adult↗

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↗

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↗