Septicemia due to Arthrobacter species in a neutropenic patient with acute lymphoblastic leukemia

Recombinant mannan-binding lectin magnetic beads increase pathogen detection in immunocompromised patients

The microbiological diagnosis of infection for hematological malignancy patients receiving chemotherapy or allogeneic hematopoietic stem cell transplantation (allo-HSCT) patients relies primarily on standard microbial culture, especially blood culture, which has many shortcomings, such as having low positive rates, being time-consuming and having a limited pathogenic spectrum. In this prospective observational self-controlled test accuracy study, blood, cerebrospinal fluid (CSF), and bronchoalveolar lavage fluid (BALF) samples were collected from chemotherapy or allo-HSCT patients with clinical symptoms of infections who were hospitalized at Peking University First Hospital. Possible pathogens were detected by the method based on recombinant mannan-binding lectin (MBL) magnetic bead enrichment (M1 method) and simultaneously by a standard method. The analytical sensitivity of M1 method was close to that of standard culture method. Besides, the turn-around time of M1-method was significantly shorter than that of standard culture method. Moreover, the M1 method also added diagnostic value through the detection of some clinically relevant microbes missed by the standard method. M1 method could significantly increase the detection efficiency of pathogens (including bacteria and fungi) in immunocompromised patients. KEY POINTS: • The detection results of M1-method had a high coincidence rate with that of standard method • M1 method detected many pathogens which had not been found by standard clinic method.

Infection or Contamination with Rothia, Kocuria, Arthrobacter and Pseudoglutamicibacter-a Retrospective Observational Study of Non-Micrococcus Micrococcaceae in the Clinic

Rothia, Kocuria, Arthrobacter, and Pseudoglutamicibacter are bacterial species within the family Micrococcaeae. Knowledge of human infections due to these bacteria is limited. This study aimed to examine features of infections caused by non-Micrococcus Micrococcaeae (NMM). Findings of NMM from blood cultures and other sterile cultures from 2012 to 2021 were identified from the records of the Department of Clinical Microbiology in Region Skåne, Lund, Sweden. Medical records were retrospectively reviewed. True infection was defined as having signs of infection, no other more likely pathogen, and no other focal infection, together with two positive blood cultures or one positive blood culture and an intravascular device. A total of 197 patients with findings of NMM in blood cultures were included. Among adult patients with bacteremia, 29 patients (22%) were considered to have a true infection. Adults with true infection were significantly more likely to have malignancy (69%), leukopenia (62%), and treatment with chemotherapeutics (66%) compared to patients with contaminated samples (24%, 3%, and 8%, respectively) (P < 0.001). A total of 31 patients had findings of NMM in other sterile cultures, and infections were considered true in joints (n = 4), a pacemaker (n = 1), and peritoneal dialysis fluid (n = 1). Infections due to NMM occur but are rare. Growth of NMM in blood cultures should be suspected to be a true infection mainly in immunocompromised patients.

Arthrobacter woluwensis Bacteremia: A Clinical and Genomic Report

Arthrobacter woluwensis is a Gram-positive, aerobic Actinobacteria that is widely distributed in the environment worldwide. Little is known about A. woluwensis infection and it is commonly mis-identified by culturing with commercial kits. To date, only six cases of bacteremia caused by A. woluwensis have been reported in the literature. Herein, we report a case of Arthrobacter woluwensis bacteremia in an immunocompromised host. In this case report, the results of antimicrobial susceptibility testing showed that this clinical isolate of A. woluwensis is sensitive to vancomycin, teicoplanin, but resistant to penicillin, cephalosporin and ciprofloxacin. Additionally, whole genome sequencing analysis identified common subunits of the urease system.

A case of infective endocarditis caused by Arthrobacter woluwensis

Corynebacteria are rare causative agents of infective endocarditis. This is a reported case of a destructive aorto-mitral infective endocarditis caused by Arthrobacter woluwensis. Microbial identification was achieved by 16S rRNA polymerase chain reaction on valve tissue samples. Outcome was favorable after surgical valve replacement and 4-week antibiotic treatment.

Identities of Arthrobacter spp. and Arthrobacter-like bacteria encountered in human clinical specimens

After the initial description of Arthrobacter spp. isolated from clinical specimens in the mid-1990s, very few further reports on Arthrobacter spp. have appeared in the clinical microbiology literature. The aim of the present study was to elucidate the distribution of Arthrobacter spp. and Arthrobacter-like bacteria encountered in clinical specimens by studying 50 consecutively isolated or received strains of large-colony-forming, whiteish-grayish, non-cheese-like-smelling, nonfermentative gram-positive rods by applying phenotypic methods as well as 16S rRNA gene sequencing. We observed a very heterogenous distribution, with the 50 strains belonging to 20 different taxa and each of 13 strains as a single representative of its particular taxon. Thirty-eight strains represented true Arthrobacter strains, 7 strains belonged to the genus Brevibacterium, 2 were Microbacterium species, and each of 3 single strains was a member of the rarely encountered genera Pseudoclavibacter, Leucobacter, and Brachybacterium, respectively. A. cumminsii (n = 14) and A. oxydans (n = 11) were the most frequently found species. The present report describes the first three A. aurescens strains isolated from human clinical specimens. Comprehensive antimicrobial susceptibility data are given for the 38 Arthrobacter isolates.

Molecular identification of environmental bacteria in indoor air in the domestic home: description of a new species of Exiguobacterium

The quality of indoor air in terms of its bioaerosol composition with microorganisms is important due to its potential aetiological role in development of conditions such as Sick Building Syndrome. Hence, laboratory identification of bacteriological components in any bioaerosol from buildings may help elucidate the role of such organisms in disease states, particularly allergy-related conditions. A molecular method was developed employing universal or "broad-range" eubacterial PCR to help identify environmental culturable bacteria from domestic household air. In a "proof of concept" experiment, 16S rDNA PCR was performed on a collection of bacterial isolates originating from indoor air in the domestic home. 16S rDNA PCR was performed using a set of universal primers to successfully generate an amplicon of approximately 1400 bp, which was sequenced to obtain each isolate's identity. Sequence analysis was able to identify 12/13 of the isolates, whereby the majority were Gram-positive (12/13). Nine different genera were identified from the 13 isolates examined, of which, 12/13 were Gram-positive, with the exception being Moraxella osloensis, which was Gram-negative, as well as a novel species of Exiguobacterium. The closest phylogenetic neighbour of the wildtype isolate to a named species within this genus was E. aestuarii (1364/1384 bases; 98.4% homology), followed by E. marinum (97.5%) and with E. acetylicum being the most distantly related of all the described species. On account of this divergence within the 16S rDNA gene operon of the unknown Exiguobacterium isolate, we believe this isolate to represent a novel species of Exiguobacterium, which we have tentatively named Exiguobacterium belfastensis. Although from this study, these organisms are usually unlikely to be clinically significant to healthy individuals with a competent immune system, we recommend that molecular identification methods are used, if considered necessary, as an adjunct to first line phenotypic identification schemes, where a definitive identification is required. When the use of molecular identification methods is justified, employment of partial 16S rDNA PCR and sequencing provides a valuable and reliable method of identification of environmental bacteria in the home. This study demonstrates the usefulness of such methods and a full and comprehensive study is now required to examine the diversity of bacteria in indoor air in the home, with particular emphasis on the risk of such environmental organisms to immunosurpressed patients, such as those with haematological malignancies and who are neutropenic.

Arthrobacter woluwensisSubacute Infective Endocarditis: Case Report and Review of the Literature

We report a case of endocarditis due to Arthrobacter woluwensis and review the published reports of Arthrobacter species isolated from human clinical samples. A 39-year-old injection drug user presented with fever and a new heart murmur. A. woluwensis was isolated from blood cultures, and a diagnosis of subacute infective endocarditis of the native mitral valve was made. The patient was successfully treated with a 6-week course of intravenous teicoplanin. From our review of the literature, we were able to retrieve data on 41 cases of Arthrobacter species isolated from human clinical samples. However, Arthrobacter species was documented as a cause of human disease on only 5 other occasions (2 cases of bacteremia, 1 case of postoperative endophthalmitis, 1 case of a Whipple disease-like syndrome, and 1 case of phlebitis). Because of the difficulty of identifying Arthrobacter strains by conventional biochemical assays, it is likely that infections with these coryneform bacteria are underreported.

Characteristics of Arthrobacter cumminsii, the most frequently encountered Arthrobacter species in human clinical specimens

During a 2-year period, 10 strains of Arthrobacter cumminsii were isolated in or received by a Swiss routine clinical bacteriology laboratory, and 5 further isolates were referred to a Swedish bacteriology reference center over a 5-year period, making A. cumminsii the most frequently encountered Arthrobacter species in these two laboratories. The present report outlines the clinical features of the 15 A. cumminsii strains and presents an extended biochemical characterization of this microorganism. A. cumminsii exhibits a unique cellular fatty acid pattern with the consistent presence of C14:0i and C14:0 fatty acids as well as relatively large amounts of C16:0i and C16:0 fatty acids usually not seen in other Arthrobacter spp. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was found to be a useful tool for confirmation of the identification of A. cumminsii. The MICs of 39 antimicrobial agents were determined, and it was demonstrated that aminoglycosides and quinolones had only weak activities against A. cumminsii strains, in contrast to their activities against most other coryneform bacteria. As a result of the extended characterization of A. cumminsii, an emended description of this species is presented. Due to the lack of A. cumminsii in established identification systems, it is most likely that this species is underdiagnosed in many routine clinical bacteriology laboratories.