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PubMed2000

Citrobacter rodentium, the causative agent of transmissible murine colonic hyperplasia, exhibits clonality: synonymy of C. rodentium and mouse-pathogenic Escherichia coli.

Citrobacter rodentium (formerly Citrobacter freundii biotype 4280 and Citrobacter genomospecies 9) was described on the basis of biochemical characterization and DNA-DNA hybridization data and is the only Citrobacter species known to possess virulence factors homologous to those of the human pathogens enteropathogenic Escherichia coli and enterohemorrhagic E. coli. These virulence factors are encoded on the locus of enterocyte effacement (LEE), a pathogenicity island required for the characteristic attaching and effacing (AE) pathology seen in infection with these three pathogens. C. rodentium, which apparently infects only mice, provides a useful animal model for studying the molecular basis of AE pathology. No work has been done to assess differences in pathogenicity between C. rodentium isolates from diverse sources. Here, we report the examination of 15 C. rodentium isolates using a battery of genetic and biochemical approaches. No differences were observed between the isolates by repetitive-element sequence-based PCR analysis, biochemical analysis, and possession of LEE-specific virulence factors. These data suggest that members of the species are clonal. We further characterized an atypical E. coli strain from Japan called mouse-pathogenic E. coli (MPEC) that, in our hands, caused the same disease as C. rodentium. Applying the same battery of tests, we found that MPEC possesses LEE-encoded virulence factors and is indistinguishable from the previously characterized C. rodentium isolate DBS100. These results demonstrate that MPEC is a misclassified C. rodentium isolate and that members of this species are clonal and represent the only known attaching and effacing bacterial pathogen of mice.

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↗

PubMed1999

[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.

Citrobacter↗

PubMed1999

[Differentiation of Citrobacter strains using electrophoretic protein patterns].

The aim of this study was checking of the usefulness of electrophoretic protein patterns in differentiation of Citrobacter strains. For analysis of whole-cell proteins 181 Citrobacter strains were prepared. Electrophoresis was performed in Mini Protean Duall Slab Cell (Bio-Rad) apparatus. Electrophoresis was carried out in 10% polyacrylamide gel according to the SDS-PAGE method of Laemmli. Whole-cell proteins of all tested Citrobacter strains gave after electrophoresis 12 to 20 bands. Patterns consisting of 12 to 20 fragments ranging in size from 70,000 to 14,000 and smaller, were not distinguishable. There were no significant differences between electrophorograms of Citrobacter strains belonging to the different species, useful for species differentiation. Identical protein band patterns were observed in the case of selected strains e.g. strains C. sedlakii studied in this study, coming from an outbreak, having the some phenotype.

Bacterial Proteins↗

PubMed1988

The heterogeneity of lipopolysaccharides from Citrobacter 023 serotype.

Chemical studies on carbohydrate part of lipopolysaccharides isolated from Citrobacter 87/57 and Citrobacter 1556 strains (serotype 023) were carried out. Lipopolysaccharides (LPS) were hydrolyzed with 1% acetic acid and the carbohydrate material was fractionated on Sephadex G-50 and Bio-Gel P-4 columns. All fractions obtained were subjected to chemical analysis by colorimetric methods and by gas-liquid chromatography. It was found that O-specific polysaccharide from LPS 87/57 is composed of mannose and N-acetylgalactosamine in the molar ratio of 3:1. Both lipopolysaccharides contain unsubstituted core oligosaccharides (built of heptose, glucose and galactose in molar ratio of 3:3:1) as well as core oligosaccharides substituted with shorter (LPS 87/57 and LPS 1556) and longer (LPS 87/57) O-specific oligosaccharides. Strain 87/57 is of S (smooth) type and strain 1556 lacking O-specific polysaccharide is of SR (semi-rough) type. The data of Sephadex G-100 chromatography showed that O-antigen from Citrobacter 87/57 is heterogeneous; it contains polysaccharide chains of different length but the same composition. The heterogeneity of Citrobacter 023 lipopolysaccharides has been also detected by SDS-polyacrylamide gel electrophoresis.

Acetylgalactosamine↗

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↗

PubMed1994

[A case of severe pneumonia in an elderly man, caused by Citrobacter freundii suspected to have a low susceptibility to imipenem/cilastatin sodium].

An 80-year-old blind man with lepromatous leprosy suffered from right femoral neck and humeral neck fractures on July 9, 1993. Because of fever (38.6 degrees C), difficult expectoration and diffuse bilateral perihilar infiltrates with consolidation in the left lower lung field on his chest radiograph, severe pneumonia was diagnosed. With intravenous hyperalimentation, imipenem/cilastatin (IPM/CS), ceftazidime, minocycline, gentamicin (GM), and human immunoglobulin were administrated. On July 29, hip screw-plate fixation was done. Citrobacter freundii was isolated from the sputum and its susceptibility was IPM/CS+, GM3+. Multi-drug therapy with GM and other antibiotics improved the patients' condition, but Citrobacter freundii were still detected and 43 days of medication were needed. According to a report by the Ministry of Health and Welfare in 1992, the resistance rate of IPM/CS against Citrobacter freundii is only 0.7%, and IPM/CS is more effective than beta-Lactams. This is a very rare case of severe pneumonia in an elderly patient caused by Citrobacter freundii that was suspected to have low susceptibility to IPM/CS.

Aged↗

PubMed1997

[Identification of Citrobacter species and their occurrence in raw products and foods].

Fifty-nine strains of bacteria were tested in study that were isolated from raw materials and foods (raw milk, farm milking parlors, sausage meat, raw potatoes, cheese, frozen oven-ready foods, confectionery products, cold dishes), and they were included in the genus Citrobacter using a commercial diagnostic kit ENTEROtest 16 (Lachema a.s., Brno), numeric identification program TNW (Czech Collection of Microorganisms, Faculty of Science of Masaryk University at Brno) and identification key (O'Hara et al., 1995). The results of the ENTEROtest itself, including OXI and ONPtests, did not provide satisfactory discrimination of detected strains to the level of species since 64.4% were identified by the genus by TNW program or designated as intermediary strains. Correct species identification was obtained in 33.9% only (Tab. I). Five next conventional tests (dulcitol, alpha-methyl-glucoside, raffinose, melibiose, arginine dihydrolase) were used and their results successfully specified 94.9% tested strains to the species level (Tab. I). A dichotomic identification key (O'Hara et al., 1995) enabled to classify the strains on the basis of the results of ENTEROtest 16 and two conventional tests (dulcitol, melibiosis) relatively easily, and it can be recommended for routine identification of typical Citrobacters from foods. Only ten strains were classified in a wrong way (16.9%) due to false results in ENTEROtest (Tab. II). Tab. III shows the strains classified wrongly by both identifications systems. The tested set contained Citrobacter braakii in a majority of cases (30 strains), followed by C. freundii (17 strains), C. youngae (6 strains), 2 strains of genomospecies 10 and one strain of C. koseri, C. amalonaticus and C farmeri. Tab. IV shows the presence of Citrobacter species in the particular raw materials and foods. The most frequently present species in raw materials: C. braakii (26 strains, 68.4%), C. freundii (3 strains, 7.9%) and C. youngae (3 strains, 7.9%). Foods contained these three species only: C. freundii (14 strains, 66.7%), C. braakii (4 strains, 19.0%) and C. youngae (3 strains, 14.3%). The percentage of the three most frequently present species in raw materials is substantially different from their percentage in foods (Fig. 1). The higher percentage of C. freundii presence in foods can be ascribed to secondary contamination.

Bacteriological Techniques↗

PubMed2001

[Characterization and distribution of Citrobacter species in a university hospital].

OBJECTIVE: [corrected] a) To identify Citrobacter strains following the conventional biochemical reaction of Brenner and col; b) to evaluate the sensitivity and specificity of the O'Hara's method compared with Brenner's method, and c) to determine the rate and distribution of the strains in the clinical isolates. MATERIAL AND METHODS: One hundred and twenty two clinical isolates, characterized as Citrobacter spp. were collected between May of 1994 and August of 1997. Clinical isolates included inpatients and outpatients from Hospital de Clínicas. Strains were identified following the methods of Brenner and O'Hara. RESULTS: Methods of Brenner identified 111 of 122 strains: C. freundii 59 of 111; C. koseri 18 of 111; C. werkmanii 15 of 111; C. braakii 9 of 111; C. youngae 6 of 111 and C. amalonaticus 4 of 111. O'Hara's methods identified 104 of 111 strains (94%). C. freundii was recovered most frequently from urine and feces (p Fisher < 0.026 and 0.039 respectively), while C. koseri was isolated from urine principally (p Fisher < 0.0372). CONCLUSIONS: The genus Citrobacter is an important opportunistic pathogen that can be identified in clinical microbiology laboratories using O'Hara's method.

Bacteremia↗

PubMed1994

Heterogeneity at the beta-lactamase structural gene ampC amongst Citrobacter spp. assessed by polymerase chain reaction analysis: potential for typing at a molecular level.

Considerable biochemical diversity and polynucleotide sequence variation have been reported amongst strains of Citrobacter spp. However, sequence heterogeneity has not been investigated at gene loci of clinical relevance. In this study, sequence heterogeneity in the beta-lactamase structural gene, ampC, amongst 91 clinical isolates of Citrobacter spp. that showed resistance to various third-generation cephalosporins was investigated. Variation was examined by high-stringency polymerase chain reactions (PCR) with primers homologous to the known ampC sequences of C. freundii strains OS60 and I113, and C. diversus NF85. If an isolate contained an ampC gene homologous to one of these three characterised ampC genes, a single PCR band of a predictable size was generated with the appropriate primer set; 50 (60%) of isolates gave a PCR product of the expected size with the OS60 primer set and nine (10%) gave a product with the I113 primer set. All these 59 isolates were identified as C. freundii by API-20E strips. Six isolates (7%) gave a product with the C. diversus NF85 primer set but only four of these were identified as C. diversus in API-20E tests; the other two isolates were identified as C. freundii. Of the 91 isolates, 28 (31%), were identified as either C. freundii or C. diversus, but gave no PCR product with any primer set tested. Five of these showed no homology to any of the reference strain ampC PCR products in hybridisation tests. Nevertheless, all showed beta-lactamase activity. Overall, this method allowed the identification of novel ampC gene loci, which may serve as a basis for the identification of Citrobacter spp. rapidly at a molecular level.

Base Sequence↗

PubMed2005

Vertically acquired neonatal citrobacter brain abscess - case report and review of the literature.

Vertically acquired citrobacter meningitis in the neonate is very rare and carries a very high mortality and morbidity. Overall, approximately 30% of neonates with Citrobacter meningitis die and 50% sustain some damage to the CNS. The authors describe a case of a newborn with Citrobacter koseri meningitis with multiple brain abscesses, with a successful outcome following multiple burr-hole aspirations and prolonged antibiotic therapy. An aggressive surgical approach combined with intravenous antibiotics (including imipenems, to which the organism is very sensitive) for a minimum of 4 weeks appears to improve the outcome of infection with this virulent organism.

Anti-Bacterial Agents↗

PubMed2003

Structural and serological studies on a new 4-deoxy-d-arabino-hexose-containing O-specific polysaccharide from the lipopolysaccharide of Citrobacter braakii PCM 1531 (serogroup O6).

The O-specific polysaccharide of Citrobacter braakii PCM 1531 (serogroup O6) was isolated by mild acid hydrolysis of the lipopolysaccharide (LPS) and found to contain d-fucose, l-rhamnose, 4-deoxy-d-arabino-hexose and O-acetyl groups in molar ratios 2 : 1 : 1 : 1. On the basis of methylation analysis and 1H and 13C NMR spectroscopy data, the structure of the branched tetrasaccharide repeating unit of the O-specific polysaccharide was established. Using various serological assays, it was demonstrated that the LPS of strain PCM 1531 is not related serologically to other known 4-deoxy-d-arabino-hexose-containing LPS from Citrobacter PCM 1487 (serogroup O5) or C. youngae PCM 1488 (serogroup O36). Two other strains of Citrobacter, PCM 1504 and PCM 1505, which, together with strain PCM 1531, have been classified in serogroup O6, were shown to be serologically distinct from strain PCM 1531 and should be reclassified into another serogroup.

Animals↗

PubMed1998

Osteomyelitis and septic arthritis due to Citrobacter freundii and Haemophilus influenzae type b.

This report describes dual infection with Citrobacter freundii and Haemophilus influenzae type b causing septic arthritis and osteomyelitis of the elbow in a previously healthy 5-year-old boy. The patient was treated successfully with intravenous fosfomycin for 4 weeks. Infections with Citrobacter beyond the neonatal period are rare in paediatric patients. When Citrobacter spp. is isolated, coinfection with other bacterial pathogens should be considered.

Arthritis, Infectious↗

PubMed2003

Citrobacter bacteremia in a tertiary care hospital.

From January 1998 to December 2001, 176 cases of Citrobacter bacteremia occurred of which repeat isolation was possible in 48 cases. Of 48 isolates, 79.1% were C. diversus and 20.9% C. freundii. Citrobacter bacteremia was polymicrobial in 46.1% cases, and maximum number of cases (54.1%) occurred in the age group less than 10 years. Portal of entry was unknown (42.3%), respiratory tract (20.9%), gastrointestinal tract (15.3%) and urinary tract 15.3%. C. freundii isolates were relatively more resistant than C. diversus against 10 tested antimicrobial agents, while 79.1% isolates were multiresistant. Sensitivity based on MIC was highest for ceftizoxime, ciprofloxacin and cefotaxime. Overall mortality of Citrobacter bacteremia was seen in 56% of cases. Therefore greater caution is required in selection of antibiotic therapy in order to avoid selection of strains and treatment failure.

Adolescent↗

PubMed2005

Peritumoral Citrobacter koseri abscess associated with parasagittal meningioma.

OBJECTIVE AND IMPORTANCE: This is the second report of a Citrobacter-associated brain abscess in an adult and the first report of its association with an intradural tumor. Excluding those associated with trauma, neurosurgical procedures, and proximity to the skull base, only seven other cases of abscesses associated with intracranial tumors have been published. Five of seven tumor-associated abscesses with a microbiological diagnosis involved gram-negative bacteria, a finding that may indicate a predilection of these microorganisms for intracranial tumors. CLINICAL PRESENTATION: A 78-year-old female patient presented with a 6-month history of confusion and personality changes. Her medical history included paroxysmal atrial fibrillation and a 10-day course of high-dose dexamethasone but no other predisposing conditions for sepsis. She was afebrile, had no focal neurological deficits, and had no systemic abnormalities on examination. Computed tomographic imaging revealed a noncalcified, homogeneously enhancing, 3-cm-diameter, extra-axial tumor associated with the right anterior falx cerebri. The tumor did not extend to the skull base. INTERVENTION: At craniotomy, 10 to 20 ml of thick pus was found around the posteroinferior surface of the tumor. On extended culture, this material demonstrated Citrobacter koseri growth, which was effectively treated with ceftriaxone followed by meropenem and one repeated abscess aspiration. No systemic source of the infection was found. CONCLUSION: The characteristic endothelial invasiveness of Citrobacter and related gram-negative bacteria may predispose to the formation of abscesses in association with intracranial tumors.

Aged↗

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↗

PubMed2000

Citrobacter diversus endocarditis.

Citrobacter species are motile Gram-negative bacilli that cause disease in humans, such as urinary tract infection, pneumonia, superficial and deep wound infections, gastroenteritis, meningitis, bacteremia, and rarely endocarditis. In those cases of endocarditis, intravenous drug use has been associated with Citrobacter species. Gram-negative organisms are present in less than 10% of cases of endocarditis in intravenous drug users. We present a case of tricuspid valve endocarditis in an intravenous drug user caused by Citrobacter diversus alone.

Citrobacter↗

PubMed2004

Pneumocephalus in neonatal meningitis: diffuse, necrotizing meningo-encephalitis in Citrobacter meningitis presenting with pneumatosis oculi and pneumocephalus.

UNLABELLED: OBJECTIVE/PATIENT: Gas-containing encephalitis is rarely associated with neonatal meningitis. We report a case of a 19-day-old baby who presented with a rapid onset of septic shock complicated by progressively increasing gas accumulation within the brain and anterior chamber of the eye. We describe the evolution of the clinical picture and the management. INTERVENTIONS: Ventilatory support, fluid resuscitation, and continuous venovenous hemofiltration were provided in view of multiple system failure. Despite effective antibiotic therapy and supportive management, the patient died with worsening accumulation of gas within the brain, resulting in brainstem death. RESULTS: Computed tomographic images were characteristic of diffuse necrotizing meningo-encephalitis. Postmortem examination showed friable brain tissue with venous infarction and extensive gas accumulation. Citrobacter koseri was identified from the blood and cerebrospinal fluid cultures. CONCLUSION: This case re-emphasises the importance of C. koseri as both a community-acquired and nosocomial neonatal pathogen. Radiologic evidence suggestive of diffuse necrotizing meningo-encephalitis in combination with pneumocephalus and pneumatosis oculi in Citrobacter infections has never been described before. Diagnostic imaging with computed tomographic scanning of the brain and initiation of broad-spectrum antibiotics with good penetration into cerebrospinal fluid are indicated as soon as infection with Citrobacter species is suspected clinically, with appearance of pneumatosis oculi as a rare, late finding.

Citrobacter koseri↗