Citrobacter meningitis in adults

Genomic analysis of Citrobacter from Australian wastewater and silver gulls reveals novel sequence types carrying critically important antibiotic resistance genes

Antimicrobial resistance (AMR) is a major public health concern, and environmental bacteria have been recognized as important reservoirs of antimicrobial resistance genes (ARGs). Citrobacter, a common environmental bacterium and opportunistic pathogen in humans and other animals, has been largely understudied in terms of its diversity and AMR potential. Whole-genome (short-read) sequencing on a total of 77 Citrobacter isolates obtained from Australian silver gull (Chroicocephalus novaehollandiae) (n = 17) and influent wastewater samples (n = 60) was performed, revealing a diverse Citrobacter population, with seven different species and 33 sequence types, 17 of which were novel. From silver gull using non-selective media we isolated a broader range of species with little to no mobilised ARG carriage. Wastewater isolates (selected using Carbapenem- Resistant Enterobacterales (CRE) selective media) carried a heavy burden of ARGs (up to 21 ARGs, conferring resistance to nine classes of antibiotics), with several novel multidrug-resistant (MDR) lineages identified, including C. braakii ST1110, which carried ARGs conferring resistance to eight to nine classes of antibiotics, and C. freundii ST1105, which carried two carbapenemase genes, blaIMP-4 in class 1 integron structure, and blaKPC-2. Additionally, we identified an MDR C. portucalensis isolate carrying blaNDM-1, blaSHV-12, and mcr-9. We identified IncC, IncM2, and IncP6 plasmids as the likely vectors for many of the critically important mobilised ARGs. Phylogenetic analyses were performed to assess any epidemiological linkages between isolation sources, demonstrating low relatedness across sources beyond the ST level. However, these analyses did reveal some closer relationships between strains from disparate wastewater sources despite their collection some 13,000 km apart. These findings support the need for future surveillance of Citrobacter populations in wastewater and wildlife populations to monitor for potential opportunistic human pathogens.

Citrobacter freundii induces sepsis with new-onset status seizure in an adult: A case report and literature review

RATIONALE

Sepsis with brain abscess induced by Citrobacter freundii in adults has rarely been reported and is extremely pathogenic with a high mortality rate. Early diagnosis of the infection still remains challenging.

PATIENT CONCERNS

A 27-year-old woman was transferred to our emergency department for fever, status seizure and refractory hypotension. Administration of midazolam, propofol and sodium valproate could not attenuate the seizure except for the addition of vecuronium. The blood white blood cell count was 42.91 (109/L) with 80% neutrophils, and procalcitonin was 22.46ng/mL.

DIAGNOSES

Both deoxyribonucleic acid and ribonucleic acid of C freundii were detected in blood by metagenomic next-generation sequencing of pathogens,the diagnosis of septic shock and brain abscess caused by C freundii was highly suspected.

INTERVENTIONS

On day 1, antibiotics of cefoperazone sodium and sulbactam sodium 6g/day, immunoglobulin, and hydrocortisone were used with suspected septic shock. Continuous renal replacement therapy was used to eliminate excessive lactate, ammonia, myohemoglobin and creatinine. On day 2, a brain computed tomography scan revealed multiple patchy slightly low densities in the brain, antibiotics were adjusted to meropenem intravenously 3g/day.

OUTCOMES

On day 2, a brain computed tomography scan revealed multiple patchy slightly low densities in the brain, she died on day 3.

LESSONS

Clinicians should consider the possibility of brain abscess when evaluating a patient with new-onset dizziness, fever, seizure, or other neurologic symptoms or signs, especially for patients whose mental status changes. metagenomic next generation sequencing and resistance genes could be considered when cerebrospinal fluid or blood results are negative and clinical manifestations are highly suspected of infection or when the treatment time is limited.

Fatal Citrobacter farmeri meningitis in a patient with nasopharyngeal cancer

We describe the case of an adult male with nasopharyngeal carcinoma who had meningitis caused by Citrobacter farmeri. The isolate was confirmed as C. farmeri by two commercial identification systems and 16S rRNA gene analysis. The patient developed multiorgan failure and died despite antibiotic treatment with in vitro active agents (ceftriaxone and meropenem).

fliP influences Citrobacter koseri macrophage uptake, cytokine expression and brain abscess formation in the neonatal rat

Citrobacter koseri causes neonatal meningitis frequently complicated with multiple brain abscesses. During C. koseri central nervous system infection in the neonatal rat model, previous studies have documented many bacteria-filled macrophages within the neonatal rat brain and abscesses. Previous studies have also shown that C. koseri is taken up by, survives phagolysosomal fusion and replicates in macrophages in vitro and in vivo. In this study, in order to elucidate genetic and cellular factors contributing to C. koseri persistence, a combinatory technique of differential fluorescence induction and transposon mutagenesis was employed to isolate C. koseri genes induced while inside macrophages. Several banks of mutants were subjected to a series of enrichments to select for gfp : : transposon fusion into genes that are turned off in vitro but expressed when intracellular within macrophages. Further screening identified several mutants attenuated in their recovery from macrophages compared with the wild-type. A mutation within an Escherichia coli fliP homologue caused significant attenuation in uptake and hypervirulence in vivo, resulting in death within 24 h. Furthermore, analysis of the immunoregulatory interleukin (IL)-10/IL-12 cytokine response during infection suggested that C. koseri fliP expression may alter this response. A better understanding of the bacteria-macrophage interaction at the molecular level and its contribution to brain abscess formation will assist in developing preventative and therapeutic strategies.

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.

Citrobacter koseri brain abscess in the neonatal rat: survival and replication within human and rat macrophages

A unique feature of Citrobacter koseri is the extremely high propensity to initiate brain abscesses during neonatal meningitis. Previous clinical reports and studies on infant rats have documented many Citrobacter-filled macrophages within the ventricles and brain abscesses. It has been hypothesized that intracellular survival and replication within macrophages may be a mechanism by which C. koseri subverts the host response and elicits chronic infection, resulting in brain abscess formation. In this study, we showed that C. koseri causes meningitis and brain abscesses in the neonatal rat model, and we utilized histology and magnetic resonance imaging technology to visualize brain abscess formation. Histology and electron microscopy (EM) revealed that macrophages (and not fibroblasts, astrocytes, oligodendrocytes, or neurons) were the primary target for long-term C. koseri infection. To better understand C. koseri pathogenesis, we have characterized the interactions of C. koseri with human macrophages. We found that C. koseri survives and replicates within macrophages in vitro and that uptake of C. koseri increases in the presence of human pooled serum in a dose-dependent manner. EM studies lend support to the hypothesis that C. koseri uses morphologically different methods of uptake to enter macrophages. FcgammaRI blocking experiments show that this receptor primarily facilitates the entry of opsonized C. koseri into macrophages. Further, confocal fluorescence microscopy demonstrates that C. koseri survives phagolysosomal fusion and that more than 90% of intracellular C. koseri organisms are colocalized within phagolysosomes. The ability of C. koseri to survive phagolysosome fusion and replicate within macrophages may contribute to the establishment of chronic central nervous system infection including brain abscesses.

Citrobacter koseri (diversus) meningitis in an otherwise healthy adolescent

Citrobacter infection is commonly reported in neonates and immunocompromised patients. Citrobacter koseri (diversus) is an important cause of neonatal meningitis and brain abscess formation. It adults, however, Citrobacter infection with central nervous system involvement is rare, and is usually associated with an underlying disorder. This report describes a 12-y-old previously healthy girl with Citrobacter koseri meningitis. Intravenous treatment with ceftriaxone for 10 d led to complete recovery. Head computed tomography and brainstem-evoked response audiometry were normal. On follow-up, the patient was completely healthy. Previously reported cases of C. koseri meningitis in the adult population were associated with underlying predisposing factors. In this case a normal, healthy adolescent was treated with intravenous ceftriaxone without any of the known neurological complications observed in the neonatal cases.

Citrobacter freundii and fatal neutropenic enterocolitis following adjuvant chemotherapy for breast cancer

Neutropenic enterocolitis is increasingly being recognized as a life-threatening complication of chemotherapy, mainly for haematological and lymphoproliferative malignancies. It is under-recognized clinically, with the diagnosis often being made on post-mortem examination. Although active medical management is generally preferred, surgical intervention may be indicated. We report a case of fatal neutropenic enterocolitis, secondary to Citrobacter freundii, following adjuvant chemotherapy for breast cancer. We also review the literature, examining the aetiology, diagnosis and management of this often fatal entity.

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.

Klebsiella oxytoca meningitis: frequent association with neurosurgical procedures

Klebsiella oxytoca meningitis is a rare condition. Nine patients were diagnosed between 1981 and 1993 at our institution. These accounted for 2.3% of 393 patients with blood and/or cerebrospinal fluid culture-proven bacterial meningitis. K. oxytoca was noted in both community-acquired meningitis and nosocomial meningitis. Eight of the nine cases were patients who had undergone neurosurgical procedures. Four were mixed bacterial meningitis. All K. oxytoca isolates were susceptible to third-generation cephalosporins and all but one to chloramphenicol. Antibiotic therapy was successful in eight patients but failed in one.