Predominant association of Raoultella bacteremia with diseases of the biliary tract

Acute cholecystitis secondary to Raoultella ornithinolytica infection, complicated by sepsis, gallbladder perforation, hepatic abscess and bacteraemia

Herein, a case of an immunocompromised patient in his early 70s is discussed who presented with clinical signs and symptoms compatible with sepsis from an intra-abdominal source and who was found to have blood cultures positive for the encapsulated Gram-negative pathogen Raoultella ornithinolytica, with the source of infection determined, via imaging, to be a case of acute cholecystitis complicated by gallbladder perforation, multiple pericholecystic and hepatic abscesses, and persistent bacteraemia. To our knowledge, this represents the first described case of cholecystitis and gallbladder perforation directly attributed to this species, and highlights both the pathogen's capacity to cause severe disease as well as the utility of a multidisciplinary approach to achieve optimal patient outcome.

Genomic insights into evolution of pathogenicity and resistance of multidrug-resistant Raoultella ornithinolytica WM1

Raoultella ornithinolytica is a poorly understood opportunistic pathogen, and the underlying mechanisms of its multidrug resistance and pathogenicity have not yet been comprehensively investigated. The multidrug-resistant (MDR) strain WM1 was isolated from the blood of a male patient in Tianjin, China, in 2018. Here, we describe the complete genome and provide a genomic analysis of R. ornithinolytica WM1. The isolate was resistant to all tested antimicrobials except amikacin, tobramycin, and tigecycline. Two plasmids, pWM1-1 (IncHI5) and pWM1-2 (IncR), carried multidrug-resistance regions. A large antimicrobial resistance island region resided on pWM1-1 and exhibited mosaic structures resulting from the acquisition of complex integrations of variable regions, including genes conferring resistance to multiple classes of antimicrobials. Moreover, WM1 possessed virulence-related elements that encode several virulence factors, including type I fimbriae, Escherichia coli common pilus, type II and VI secretion systems, yersiniabactin, enterobactin, and surface polysaccharide, indicating pathogenic potential. Furthermore, the core genome phylogeny and pan-genome analyses revealed extensive genetic diversity. Our analysis indicates the need for stringent infection control, antimicrobial stewardship, periodic resistance monitoring, and rational medication to address potential threats posed by MDR R. ornithinolytica strains.

A spotlight on Raoultella ornithinolytica: A newly emerging life-threatening zoonotic pathogen

The genus Raoultella contains Raoultella ornithinolytica (R. ornithinolytica), which was previously named as Klebsiella ornithinolytica. R. ornithinolytica is a Gram-negative bacillus that belongs to the family Enterobacteriaceae. This pathogen is normally present in aquaculture, and it has been isolated from fish, insects, and wild and domestic birds. Seafood and poultry products are incriminated as sources of R. ornithinolytica infection. Community-acquired human infection with R. ornithinolytica is common. This infection is commonly associated with sepsis, bacteremia, food poisoning, purities, and urinary and respiratory tracts' infections. Rapid acquired resistance of R. ornithinolytica strains is common, and it is related to the development of resistant genes. R. ornithinolytica is considered as a newly emerging life-threatening pathogen world-wide. Hence, it is very important to determine the role of animals and birds in the epidemiological situation of this pathogen as well as the detection of antibiotic resistance genes before treatment.

Emergence of Raoultella ornithinolytica isolated from chicken products in Alexandria, Egypt

Background and Aim:

Raoultella ornithinolytica is one of the emerging gram-negative bacteria, which associated with foodborne illness. Researches affirmed that distinguish between R. ornithinolytica and Klebsiella oxytoca are difficult, as they are phylogenetic related. The evolution of multidrug resistance of Raoultella strains gained more concern for recognition of the pathogen which supports in controlling the disease and minify its threat. This study sought to find a reliable tool for the identification of Raoultella ornithinolytica, isolated from chicken product samples, and assessed the resistance profile of R. ornithinolytica using antibiogram sensitivity tests.

Materials and Methods:

Forty samples of chicken products were collected between January and September 2019 from different markets in Alexandria Governorate, Egypt. The products included nuggets, strips, burgers, luncheon meats, pane, frankfurters, and minced chicken meat. The samples were transferred to the Reference Laboratory. The samples were subjected to isolation, biochemical reaction testing, phenotypic system analytical profile index (API) E20, and a detection of antimicrobial susceptibility test. Phenotypic identification was confirmed through matrix-assisted laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Results:

Thirty-three bacterial isolates (82.50%) out of 40 samples were isolated into pure cultures from the chicken samples. Three isolates (9.09%) were positive for R. ornithinolytica, while 30 isolates (90.91%) exhibited growth characters for different pathogens (Escherichia coli, Enterobacter aerogenes, Proteus vulgaris, R. ornithinolytica, and Klebsiella pneumoniae). The isolates of R. ornithinolytica were resistant to five types of antibiotics and sensitive to two types of antibiotics.

Conclusion:

This study reported the first case of R. ornithinolytica found in chicken products in Egypt. Phenotypic system API 20E and MALDI-TOF MS were found to be reliable tools for confirming the diagnosis of R. ornithinolytica. As it provides rapid identification with high sensitivity and specificity for R. ornithinolytica, which often do not require a molecular procedure for confirmation.

Raoultella ornithinolytica Infection in the Pediatric Population: A Retrospective Study

Raoultella ornithinolytica is a pathogen causing an increasing number of pediatric infections. The objective of this study was to investigate the clinical characteristics of R. ornithinolytica infections in children. As a retrospective analysis, clinical features and drug susceptibility data of the five cases were analyzed and related literature was reviewed. A total of 14 cases (eight females, six males) were analyzed: nine cases were retrieved from PubMed, Web of Science, and three domestic databases; five cases occurred in our hospital. The primary diseases of the older children were mainly of neoplastic and immune origin, while cases of infants and young children were mostly complicated by congenital malformation. Fever was the main symptom, and neonatal infection was mainly manifested by dyspnea and hypoxemia, with multiple skin flushes, systemic erythema, and leukocytosis. Of the 14 cases, six were ventilator-assisted, five had indwelling urethral catheters, three had surgical treatment or chemotherapy, and one had multiple rounds of continuous renal replacement therapy (CRRT). Blood infection is the main route of R. ornithinolytica infection in children. Skin flushing and systemic erythema might be positive clues for newborn infection. Patients with multiple congenital abnormalities are susceptible to infection. Tumors, immune deficiency, and invasive operations increase the risk of infection. Blood culture was the main method of disease identification. Based on the drug susceptibility results, the preferred antibiotics are third generations of cephalosporins, carbapenems, quinolone, and aminoglycoside. Lastly, patients with sepsis mostly have poor prognosis.

Genomic analysis of a Raoultella ornithinolytica strain causing prosthetic joint infection in an immunocompetent patient

We sequenced the genome of Raoultella ornithinolytica strain Marseille-P1025 that caused a rare case of prosthetic joint infection in a 67-year-old immunocompetent male. The 6.7-Mb genome exhibited a genomic island (RoGI) that was unique among R. ornithinolytica strains. RoGI was likely acquired by lateral gene transfer from a member of the Pectobacterium genus and coded for a type IVa secretion system found in other pathogenic bacteria and that may have conferred strain Marseille-P1025 an increased virulence. Strain Marseille-P1025 was also able to infect, multiply within, and kill Acanthamoaeba castellanii amoebae.

Emerging role of Raoultella ornithinolytica in human infections: a series of cases and review of the literature

BACKGROUND

Raoultella ornithinolytica is known to inhabit aquatic environments. The clinical features and outcomes of human infections caused by R. ornithinolytica have been reported for only a limited number of cases.

METHODS

A retrospective study of cases of infection caused by R. ornithinolytica managed at four university hospital centres during the period before and after the introduction of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was performed. The aim was to describe the clinical and microbiological characteristics, treatments, and outcomes.

RESULTS

Among 187 R. ornithinolytica isolates identified for which clinical information was available, 71 were considered colonizers and 116 were pathogenic. A total of 112 cases of R. ornithinolytica infection were identified. Urinary tract infections, gastrointestinal infections, wound and skin infections, and bacteraemia were observed in 36%, 14%, 13%, and 5% of cases, respectively. Associated infections that have been poorly reported, such as respiratory infections, i.e. pneumonia and pleural effusion, were observed in 24% of cases. Additional diseases reported here for the first time included osteomyelitis, meningitis, cerebral abscess, mediastinitis, pericarditis, conjunctivitis, and otitis. The proportion of R. ornithinolytica isolates resistant to antibiotics was found to be relatively high: 4% of isolates were resistant to ceftriaxone, 6% to quinolones, and 13% to co-trimoxazole. The mortality rate related to infection was 5%.

CONCLUSIONS

R. ornithinolytica is an underreported, emerging hospital-acquired infection and is particularly associated with invasive procedures. R. ornithinolytica should never be considered simply a saprophytic bacterium that occasionally contaminates bronchial lavage or other deep respiratory samples or surgical sites. Physicians should be aware of the high rates of antimicrobial resistance of R. ornithinolytica isolates so that immediate broad-spectrum antibiotic treatment can be established before accurate microbiological results are obtained.

Comparison of different methods for identification of species of the genus Raoultella: report of 11 cases of Raoultella causing bacteraemia and literature review

The genus Raoultella was excised from Klebsiella in 2001, but difficulties in its identification may have led to an underestimation of its incidence and uncertainty on its pathogenic role. Recently, clinical reports involving Raoultella have increased, probably through the introduction of mass-spectrometry in clinical microbiology laboratories and the development of accurate molecular techniques. We performed a retrospective analysis using our blood culture collection (2011-14) to identify Raoultella isolates that could have been erroneously reported as Klebsiella. PCR and gene sequencing of highly specific chromosomal class A β-lactamase genes was established as the reference method, and compared with 16S rRNA and rpoβ sequencing, as well as matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS), MicroScan Walkaway system and API20E biochemical identification. MALDI-TOF and rpoβ correctly identified all Raoultella isolates, whereas 16S rRNA provided inconclusive results, and MicroScan and API20E failed to detect this genus. The analysis of the clinical characteristics of all Raoultella bacteraemia cases reported in the literature supports the role of Raoultella as an opportunistic pathogen that causes biliary tract infections in elderly patients who suffer from some kind of malignancy or have undergone an invasive procedure. Two salient conclusions are that Raoultella shows tropism for the biliary tract and so its identification could help clinicians to suspect underlying biliary tract disease when bacteraemia occurs. Concomitantly, as most phenotypic identification systems are not optimized for the identification of Raoultella, the use of MALDI-TOF or additional phenotypic tests is recommended for the reliable identification of this genus.

Infections on the rise: Raoultella spp., clinical and microbiological findings from a retrospective study, 2010-2014

We performed a retrospective analysis of clinical and laboratory data over 5 years in a tertiary centre to assess clinical and microbiological characteristics of patients with Raoultella spp. infection. Raoultella spp. were deemed responsible for clinical infections in 57 patients (R. planticola, n = 32 and R. ornithinolytica, n = 25). The most prevalent diagnoses for R. planticola were cystitis (50%; n = 16) followed by bacteraemia and pneumonia (9.4%; n = 3); for R. ornithinolytica, cystitis (36%; n = 9) followed by pneumonia (24%; n = 6). Immunodeficiency was present in 18 patients (56.3%) with R. planticola and in 16 patients (64%) with R. ornithinolytica infection. Of these, 55.6% and 37.5% had diabetes and 27.8% and 18.% were solid organ transplant recipients, respectively. All isolates were sensitive to third-generation cephalosporins, fluoroquinolones and aminoglycosides. Mortality of infections with R. planticola (n = 5; 15.6%) was higher than for R. ornithinolytica (n = 2; 8.0%), but the difference was not statistically significant.

Clinical characteristics of Raoultella ornithinolytica bacteremia

PURPOSE

Raoultella ornithinolytica is not well known as a clinical pathogen. We performed a retrospective review of R. ornithinolytica bacteremia to investigate its clinical features, antimicrobial susceptibility, and overall patient outcomes.

METHODS

R. ornithinolytica bacteremia cases were collected from an electronic database of all cases of bacteremia over a 10-year period. Medical records were retrospectively reviewed. Demographic data, clinical information, the presence of underlying comorbidities, the results of antimicrobial susceptibility testing, and the antimicrobial regimen administered were investigated.

RESULTS

R. ornithinolytica was isolated from blood culture specimens in 16 cases. The majority of these patients had an underlying malignant condition of advanced stage (15 patients, 94 %). Seven of these patients had a solid tumor with lesions or metastases that extended to the bile duct or biliary tract. Neutropenic fever following hematologic stem cell transplantation was found in three cases. No resistance to piperacillin/tazobactam or imipenem was found. Four cases showed resistance to cefoxitin, while one of these cases showed resistance to multiple cephalosporins. In overall outcomes, seven patients (44 %) did not recover from the infection and subsequently expired.

CONCLUSIONS

R. ornithinolytica bacteremia occurs mainly in patients with underlying malignancies. The overall outcome was not favorable, despite favorable antimicrobial susceptibility test results. The findings of this study contradict those of other studies that demonstrated that infection from Raoultella species have good prognoses.