Sepsis, meningitis and cerebral abscesses caused by Citrobacter koseri

A Novel Case of Citrobacter koseri Septic Arthritis in a Native Knee Joint

Citrobacter koseri is a rare cause of septic arthritis in a native knee joint. We present the first recorded case of C. koseri septic arthritis in the native knee from a hematogenous spread resulting from a gastrointestinal illness, along with a review of the literature. A search of PubMed, Embase, OVID, and Google Scholar was conducted. Fifteen cases of musculoskeletal infection were identified, and of these, only six cases involved a septic joint and one case involved a septic knee. None of the recorded adult cases presented hematogenously without prior trauma. All of the cases achieved resolution after either antibiotic treatment alone or in conjunction with surgical treatment. Citrobacter koseri is not a rare cause of infection in general. However, it is not a common cause of septic arthritis, and this may complicate the treatment course as it can be overlooked as a cause of infection. It is essential to obtain a thorough history and a broad differential diagnosis when evaluating septic arthritis as although it may be difficult to identify the infection, C. koseri septic arthritis can be effectively treated with surgery as well as newer generation beta-lactams and cephalosporin antibiotic therapy.

In silico discovery of druggable targets in Citrobacter koseri using echinoderm metabolites and molecular dynamics simulation

Citrobacter koseri causes infection in people who are immunocompromised. Without effective antibiotics, these infections can become severe and life-threatening, so effective drugs are essential to treat these infections. Utilizing subtractive genomics, 2699 ORFs were predicted and translated into amino acid sequences. Metabolic pathway analysis and subcellular localization helped define the roles of key bacterial proteins. Two druggable proteins, WP_012000829.1 and WP_275157394.1, were discovered as promising targets. Alpha Fold provided 3D structures, and a library of 1600 echinoderm metabolites was docked against these proteins, with Ampicillin, Levofloxacin, and Doxycycline as controls. Notably, CMNPD13085 and CMNPD15632 exhibited the highest binding affinities for WP_012000829.1 and WP_275157394.1, respectively. Molecular dynamics simulations and MM-GBSA binding free energy complemented docking results. However, acknowledging the reliance on computational validations, the study emphasizes the need for essential in-vitro research to transform these potential inhibitors into therapeutic drugs.

Revolutionizing and identifying novel drug targets in Citrobacter koseri via subtractive proteomics and development of a multi-epitope vaccine using reverse vaccinology and immuno-informatics

Citrobacter koseri is a gram-negative rod that has been linked to infections in people with significant comorbidities and immunocompromised immune systems. It is most commonly known to cause urinary tract infections. Thus, the development of an efficacious C. koseri vaccine is imperative, as the pathogen has acquired resistance to current antibiotics. Subtractive proteomics was employed during this research to identify potential antigenic proteins to design an effective vaccine against C. koseri. The pipeline identified two antigenic proteins as potential vaccine targets: DP-3-O-acyl-N-acetylglucosamine deacetylase and Arabinose 5-phosphate isomerase. B and T cell epitopes from the specific proteins were forecasted employing several immunoinformatic and bioinformatics resources. A vaccine was created using a combination of seven cytotoxic T cell lymphocytes (CTL), five helper T cell lymphocyte (HTL), and seven linear B cell lymphocyte (LBL) epitopes. An adjuvant (β-defensin) was added to the vaccine to enhance immunological responses. The created vaccine was stable for use in humans, highly antigenic, and non-allergenic. The vaccine's molecular and interactions binding affinity with the human immunological receptor TLR3 were studied using MMGBSA, molecular dynamics (MD) simulations, and molecular docking analyses. E. coli (strain-K12) plasmid vector pET-28a (+) was used to examine the ability of the vaccine to be expressed. The vaccine shows great promise in terms of developing protective immunity against diseases, based on the results of these computer experiments. However, in vitro and animal research are required to validate our findings.

Citrobacter enshiensis sp. nov., isolated from seleniferous soil

Two Gram-stain-negative, facultative anaerobic, rod-shaped bacterial strains, S171T and S2-9, were isolated from seleniferous soil in China. Comprehensive phylogenetic analyses based on 16S rRNA genes, multilocus sequences and whole genome sequences indicated that the two strains belonged to the genus Citrobacter. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of strains S171T and S2-9 with the closest relative Citrobacter koseri NCTC 10786T were 83.6-83.7% and 27.7-27.8 %, respectively, which were below the species cutoff values. The ANI and dDDH values between the two strains were 97.9% and 84.8 %, respectively. The biochemical characteristics revealed that selenite tolerance, H2S and indole production, arginine dihydrolase, ornithine decarboxylase, as well as acid production from carbon sources such as d-sorbitol and arbutin are distinctive features of the two strains. Based on these results, strain S171T and strain S2-9 represent a novel species of the genus Citrobacter, for which the name Citrobacter enshiensis sp. nov. is proposed, with strain S171T (=GDMCC 1.3637T=JCM 35851T) as the type strain. The genome size of strain S171T was 4.92 Mb with a G+C content of 52.6 mol%. The genome size of strain S2-9 was 4.89 Mb with a G+C content of 52.6 mol%.

A brief insight into Citrobacter species - a growing threat to public health

Citrobacter spp. are Gram-negative, non-spore forming, rod-shaped, facultative anaerobic bacteria from the Enterobacteriaceae family often found in soil, sewage, sludge, water, food, and the intestinal tracts of animals and humans. Several members of Citrobacter spp. especially C. freundii, C. koseri, C. braakii are frequently detected in newborn illnesses, urinary tract infections, and patients with severe underlying conditions, including hypertension, diabetes, cancer, and respiratory infections, or those who are immunocompromised. Strains of Citrobacter spp. can spread vertically or horizontally from carriers or other hospital sources and thus cause nosocomial infections in hospital settings. A total of 19 Citrobacter genomospecies have been recognized based on genomics. It has been noted that the Citrobacter genus acquired antimicrobial resistance and virulence, including invasion, colonization, biofilm formation, and toxin production. The recent emergence and spread of antimicrobial resistance to β-lactams, carbapenems, fluoroquinolones, aminoglycosides, and colistin in Citrobacter spp. through chromosomal and plasmid-mediated resistance limits the empiric treatment options. Therefore, combination therapy involving costly and potentially hazardous antibiotics poses significant challenges in treating Citrobacter infections. Here we summarized the nomenclature of Citrobacter spp., clinical manifestations, epidemiology, pathogenesis, antibiotic resistance mechanisms, and treatments from various clinical samples. This review will expand our knowledge of the genomics and epidemiology of Citrobacter spp., enabling improved control of infections and the spread of these organisms.

Citrobacter koseri related abortion and fetal septicemia in cattle

A 31-month-old Holstein dairy cow aborted at 224 days of gestation with ejection of cheese-like lochia. Citrobacter koseri, which commonly exists in the normal flora of human and animal digestive tracts, was isolated from aborted fetal tissues (liver, spleen, kidney, heart, lung, cerebrum, and skeletal muscle) and fetal membranes. Histopathological examination revealed suppurative fibrinous meningoencephalitis of the cerebrum, cerebellum, and brainstem; suppurative bronchopneumonia; suppurative chorioamnionitis; and fibrous splenic serositis. Numerous gram-negative bacilli were detected in the cytoplasm of macrophages and/or neutrophils in these lesions. Bacteriological investigation and immunohistochemical staining identified the bacilli as C. koseri. This is the first report of cattle abortion caused by C. koseri infection in dairy cattle.

Multiple rare organisms causing ventriculoperitoneal shunt infection and brain abscess

Ventriculoperitoneal shunts (VPS) are inserted to treat issues with CSF flow dynamics, such as obstructions causing CSF build up which raises the intracranial pressure. A major complication of this procedure is VPS infections. Vast majority of VPS infections are monomicrobial and may occur in the first two years of insertion due to contiguous or hematogenous spread. Here, we report a rare case of polymicrobial VPS infection with 5 pathogens. One of these organisms (Citrobacter werkmanii) has been reported as a cause of meningitis for the first time in this report. The other organism (Enterococcus casseliflavus) has been reported as a cause only one other time. Hence, we recommend considering these newly emerging organisms when dealing with meningitis.

Genotypic Detection of qnrA and qnrC Genes in Citrobacter koseri Isolated from Patients with Urinary Tract Infection

The urinary tract infection (UTI) is a prevalent infection that affects people of all ages. Bacterial agents are the most common causes of UTIs. Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, and other staphylococcal species, Citrobacter freundii and Citrobacter koseri (C. koseri) account for a smaller number of infections. These pathogens are transported into the urinary tract from the colonic biotope into dysbacteriosis. Urine samples were randomly collected from 249 outpatients who were suspected of having UTIs. After genital cleaning, 10 mL of urine specimens were collected in a sterilized bowel. Then, the specimens were centrifuged at 2,000 rpm for 5 min and the residue was aerobically incubated with the broth infusion of brain flasks at 37°C for 24 h and then applied with a sterile ring onto blood agar plates and MacConkey agar (OxoidTM). Out of 249 urine samples, the results proved that there were 176 (70.7%) and 51(20.5%) gram-negative and gram-positive bacteria isolates, respectively. However, the results demonstrated that there were 22 (8.8%) urine samples with no growth. In addition, the results showed that eight various antimicrobials are used to treat C. koseri. In the current study, C. koseri was treated with eight different antimicrobial agents. The antimicrobial resistance rate for 7 isolates against Cefotaxime, Ceftriaxone, Ciprofloxacin, and Levofloxacin was high for 6 (85.71%) isolates. The results indicated that 6 and 5 isolates had 85.71% and 71.42% antimicrobial resistance against Ceftazidime and Levofloxacin, respectively. Whereas Gentamicin showed a moderate rate of resistance (4 isolates, 57.14%), and Amikacin resistance was found in 5 isolates, accounting for 28.57%. The bacterial isolates had a high susceptibility rate to Imipenem. The qnrA gene was found in 6 (85.71%) isolates. However, the recorded data demonstrated that there is no isolate carrying the qnrC gene. Among all pathogenic bacteria, C. koseri was the lowest causative agent of UTI in this study and was highly resistant to most antimicrobials except Imipenem, which was a good antibiotic with 100% sensitivity.

Antimicrobial Resistance and Molecular Characterization of Citrobacter spp. Causing Extraintestinal Infections

Objectives

This prospective study was carried out to investigate molecular characteristics and antimicrobial susceptibility patterns of Citrobacter spp. from extraintestinal infections.

Methods

Forty-six clinical Citrobacter spp. isolates were isolated from hospital patients with extraintestinal infections and analyzed by multilocus sequence typing (MLST) using seven housekeeping genes. Antimicrobial susceptibility testing was performed by disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. Adhesion and cytotoxicity to HEp-2 cells were assessed.

Results

The 46 clinical Citrobacter spp. isolates were typed into 38 sequence types (STs), 9 of which belonged to four clonal complexes (CCs). None of the isolates shared the same ST or CCs with isolates from other countries or from other parts of China. Over half of the isolates were multidrug-resistant (MDR), with 17/26 C. freundii, 5/6 C. braakii, and 3/14 C. koseri isolates being MDR. Moreover, four isolates were carbapenem resistant with resistance to imipenem or meropenem. Among eight quinolone resistant C. freundii, all had a mutation in codon 59 (Thr59Ile) in quinolone resistance determining region of the gyrA gene. Only a small proportion of the isolates were found to be highly cytotoxic and adhesive with no correlation to sample sources.

Conclusions

There was a diverse range of Citrobacter isolates causing extraintestinal infections and a high prevalence of MDR.

Citrobacter koseri stimulates dendritic cells to induce IL-33 expression via abundant ATP production

Introduction. Food allergies (FAs) occur due to intestinal immune dysfunction elicited by dysbiotic conditions. It was previously determined by us that Citrobacter species propagate in the faeces of mice with FAs and worsen allergic symptoms by inducing the allergenic cytokine IL-33. Dendritic cells can play important roles in regulation of FA responses.Hypothesis. Citrobacter species propagating in intestines of mice worsen allergic symptoms by stimulating dendritic cells to induce IL-33 expression.Aim. The aim of the present study was to analyse whether C. koseri stimulates dendritic cells to induce IL-33 expression.Methodology. IL-33 expression was evaluated in a DC2.4 mouse dendritic cell line stimulated by live or heat-inactivated C. koseri JCM1658, ATP, LPS extracted from C. koseri JCM1658 or other enterobacteria by real-time PCR. The ATP concentration and number of live bacteria in the culture supernatant were measured simultaneously.Results. Live C. koseri JCM1658 induced higher levels of IL-33 expression than other enterobacteria tested, but such a response was not elicited by heat-inactivated C. koseri JCM1658. LPS extracted from C. koseri JCM1658 did not induce IL-33 expression and suppressed live C. koseri JCM1658-induced IL-33 expression via the activation of Toll-like receptor 4 signalling. Furthermore, ATP produced by C. koseri JCM1658 stimulated dendritic cells to induce IL-33 expression by stimulating the P2X₇ receptor, and LPS attenuated extracellular ATP-induced IL-33 expression. C. koseri JCM1658 was observed to proliferate more vigorously and produce more ATP than other enterobacteria.Conclusion. C. koseri acts as an allergenic bacterium through ATP production, stimulating dendritic cells to induce IL-33 expression, while LPS released from inactivated C. koseri JCM1658 attenuates this allergenicity.

Description of Citrobacter cronae sp. nov., isolated from human rectal swabs and stool samples

Nine independent Gram-negative bacterial strains were isolated from rectal swabs or stool samples of immunocompromised patients from two different wards of a university hospital. All isolates were phylogenetically analysed based on their 16S rRNA gene sequence, housekeeping gene recN, multilocus sequence analysis of concatenated partial fusA, leuS, pyrG and rpoB sequences, and by whole genome sequencing data. The analysed strains of the new species cluster together and form a separate branch with Citrobacter werkmanii NBRC105721T as the most closely related species. An average nucleotide identity value of 95.9-96% and computation of digital DNA-DNA hybridization values separate the new species from all other type strains of the genus Citrobacter. Biochemical characteristics further delimit the isolates from closely related Citrobacter type strains. As a result of the described data, a new Citrobacter species is introduced, for which the name Citrobacter cronae sp. nov. is proposed. The type strain is Tue2-1T with a G+C DNA content of 52.2 mol%.

Multiple Brain Abscesses Caused by Citrobacter Koseri in a Preterm Neonate - Case Report

Background

Brain abscesses are very rarely diagnosed in neonates, but if present, they are associated with a high risk of severe complications and mortality. In neonates, brain abscesses can be detected on transfontanelle ultrasonography, in which they appear as hyperechogenic lesions surrounded by a hypoechogenic border.

Case Report

We present a female neonate, born in the 28^th week of gestation, with birth weight of 950 grams, who was born in an ambulance by spontaneous vaginal vertex delivery. No signs of infection were present until the 35^th day of hospitalization, when a sudden and serious deterioration in the patient’s condition was observed due to late-onset sepsis. Cranial US, performed on the 40^th day of life, revealed hyperechogenic lesions with a hypoechogenic halo in the right frontal lobe, which could correspond to brain abscesses. These lesions were caused by Citrobacter koseri septicaemia, identified by transfontanelle ultrasonography, and confirmed on magnetic resonance imaging. The patient recovered and was discharged on the 91th day of life (39 PCA) with a recommendation of permanent neurological surveillance.

Conclusions

Ultrasonography of the central nervous system can reveal inflammatory changes and developing brain abscesses. In neonates, magnetic resonance imaging should be performed as the method of choice for confirming brain abscesses.

Strongyloides Hyperinfection Syndrome causing fatal meningitis and septicemia by Citrobacter koseri

Citrobacter koseri is a gram-negative bacillius that belongs to the Enterobacteriaceae family. It is an uncommon pathogen that typically causes meningitis and brain abscesses in children, however central nervous system (CNS) infections are rarely found in adults. We present a case of C. koseri meningitis in an immunocompetent adult secondary to intestinal micro-perforation caused by Strongyloides A 76-year-old man admitted for asthma exacerbation developed septic shock. A lumbar puncture revealed bacterial meningitis. Blood and CSF cultures grew Citrobacter koseri with identical susceptibilities, suggesting infection by one strain. Despite broad-spectrum antibiotics, the patient expired of multi-organ failure. Autopsy identified diffuse alveolar hemorrhage as the immedi ate cause of death with a heavy burden of Strongyloides stercoralis in his gastrointestinal system, lungs, and meninges. Citrobacter koseri is a gram-negative bacillus of the Enterobacteriaceae family. It is an uncommon pathogen that typically causes meningitis and brain abscesses in children. Infections in adults occur in immunocompromised hosts or instances where an insult creates a port of entry. This is the first documented case of C.koseri sepsis in an immunocompetent host associated with Strongyloides Hyperinfection Syndrome (SHS), where massive parasitic intestinal invasion reaches pulmonary circulation and perforates the alveolar membrane. This case highlights that presence of rare enterobacterial infections should prompt consideration of differentials including SHS.

Musculoskeletal infections associated with Citrobacter koseri

Introduction Citrobacter koseri is a well known cause of central nervous system infections in the paediatric setting. Musculoskeletal infections caused by C koseri are rare, with only 14 previously reported cases. We present the first recorded case of C koseri induced septic arthritis of the knee along with a review of the literature. Methods A search of the PubMed, Embase(®) and Google Scholar™ databases was undertaken. Only complete or near complete cases were reviewed. Findings Fourteen musculoskeletal infections were identified. Of these, five were associated with an operative procedure and five involved a septic joint. Surgical treatment was required in the majority of cases and cure was achieved in all cases following prolonged antibiotic use. Conclusions C koseri associated musculoskeletal infections may complicate primary orthopaedic procedures. The organism can present aggressively and can be difficult to identify microbiologically. It is sensitive to newer generation beta-lactams, cephalosporin-based antibiotics and timely surgery.

Endogenous endophthalmitis caused by Citrobacter koseri originating from a renal abscess

We present a rare case of endogenous endophthalmitis caused by Citrobacter koseri. A 69-year-old woman with a history of poorly controlled diabetes and a protracted urinary tract infection (UTI) presented with a painful swollen left eye. There was no history of eye surgery or trauma. Imaging revealed an abscess in the right kidney. Although endophthalmitis is very rare in healthy patient, it is more common in the immunocompromised. In this patient, several multiple system illnesses including poorly controlled diabetes appear to have worked synergistically to make endophthalmitis a realistic complication of an otherwise isolated and remote source of infection, in this case pyelonephritis. Endophthalmitis, in the absence of an obvious exogenous cause, should be investigated thoroughly to exclude metastatic microbial spread. In addition, chronic features of UTI in a patient with poorly controlled diabetes or who is otherwise immunosuppressed warrant the exclusion of an underlying renal abscess.

Neonatal Citrobacter koseri Meningitis: Report of Four Cases

Citrobacter koseri is a rare cause of neonatal meningitis with predisposal for brain abscesses, and therefore responsible for high mortality and serious neurologic sequelae in this age group. We present the evolution and outcome of four cases of C. koseri meningitis. One of them developed brain abscesses and another one died. The cases show the bacteria's propensity for serious brain damage, despite early and adequate treatment, and the high risk of long-term neurologic complications in survivors, which imposes a close follow-up.