Enterococcus thailandicus in urine

Dear Editor,

With great interest, we read the article about identification of E. thailandicus in an abdominal infection in a patient [1]. This first isolation expands knowledge of the clinical pathogenic potential of rarely identified Enterococcus species. We are now able to contribute a second clinical isolation, obtained from a urine sample. To the best of our knowledge, this may represent the first documented further characterized isolation from a clinical urine sample associated with a possible infection.

Enterococci are a bacterial genus of gram-positive cocci found in the gastrointestinal tract of a broad range of animals and humans, predominantly as part of the intestinal microbiota. The number of assigned members has increased to 70 species, with E. faecalis and E. faecium being the most relevant enterococci from clinical isolates. Most of the others are rarely found in clinical specimens, due to their low prevalence and difficulties in identification. Thus, antibiotic susceptibility and pathogenic potential as well as their role in human diseases are often not clearly defined.

E. thailandicus (senior synonymous name E. sanguinicola or CDC PNS-E2 [2]) may be an illustrative example. After the first identification in 2008 in fermented sausages from Thailand [3], E. thailandicus was subsequently found in other animals [4]. Due to its bacteriocin-like activity against gram-negative species the bacterium could exhibit features of probiotics. Only sporadic detections in human feces have been reported [5]. So far, the only published clinical isolate clearly associated with human disease was reported by Mbouche et al. [1]. It is possible that other previous identifications have remained unpublished due to limited clinical relevance or other reasons.

With increased identification by automated systems such as MALDI-TOF, the number of clinical detections may rise. More detailed information on disease course and antibiotic susceptibility may be valuable for management of infectious diseases.

The patient here had undergone prostatectomy and excision of a bladder diverticulum. A urine sample was taken as routine postoperative follow-up approximately one week following surgery, and E. thailandicus was subsequently identified. After 18 hours of incubation small, whitish, slimy colonies (Fig. 1) were observed and identified as E. thailandicus by MALDI-TOF. Identification was confirmed in three independent measurements (Bruker Daltonics, IVD-Extension/1/134IVD/2023/12299, LogScore values 1.79, 2.07 and 2.09, E. faecium was among lower ranked hits). At the time of the urine sampling, he did not complain of any pain; two urine analyses, taken postoperatively, showed leukocyturia and erythrocyturia. No immunosuppression or other underlying conditions were identified. He had recovered and was discharged from the hospital before the microbiological analysis of the urine sample was completed. The patient was advised to present in case of clinical symptoms. Follow-up was arranged but it did not show any findings.

Fig. 1.

A Colony morphology on Columbia blood agar B Gram staining.

Antimicrobial testing demonstrated susceptibility to ampicillin, amoxicillin, levofloxacin, tigecycline, teicoplanin and linezolid (interpretation according to EUCAST breakpoints). Vancomycin susceptibility was confirmed by the Etest method (bioMérieux, Marcy l'Étoile, France) with an MIC of 0.38 mg/L. Moreover, the isolate showed wild-type phenotype with low-level resistance to gentamicin. These results compare with other reported susceptibility results in animals and human isolates.

The patient had not traveled abroad recently. He reported regular contact with a dog, a cat and 15 chickens in his leisure time. Unfortunately, testing the animals was not possible. It seems plausible that infrequent Enterococcus species, if present in the intestinal microbiome, may translocate into the urogenital tract in certain clinical situations and cause infection. Pre-existing conditions such as a diverticulum may facilitate bacterial colonization in the bladder. However, although our results and the mild clinical course should be interpreted with caution, they may suggest a rather low pathogenic potential.

Furthermore, isolation and characterization of E. thailandicus isolates should be undertaken. Understanding the pathogenic potential of rare, opportunistic pathogens is still incomplete. Alongside the collection of clinical findings and antimicrobial susceptibility results, low-threshold publishing or registry entries are needed to provide microbiological guidance for the clinical management of these rare microorganisms.

Declaration of potential conflicts of interest

SS did not receive any payments or hold relationships as conflict of interest within the submitted work. Outside the submitted work he declares Honoraria/Allowance from searchlight Pharma, Meet the experts-Academy, Boehringer Ingelheim, Deutscher Verein für Versicherungswissenschaft e.V., DFG (call for establishment of international cooperation). All other authors declare no financial or non-financial interests within the last three years which pose a potential conflict of interests regarding the submitted work.

CRediT authorship contribution statement

Schlabe Stefan: Writing – original draft, Visualization, Investigation, Data curation, Conceptualization. Galina Asseva: Writing – review & editing, Supervision, Methodology, Formal analysis, Data curation. Ursula Brands-Jordan: Writing – review & editing, Supervision, Methodology, Formal analysis, Data curation. Evgenii Sedov: Writing – review & editing, Investigation, Data curation. Jens Küster: Writing – review & editing, Supervision, Investigation, Data curation. Patrick Chhatwal: Writing – review & editing, Validation, Supervision, Methodology, Investigation, Formal analysis, Conceptualization.

Funding

No funding was received for this work.

Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:SS declares Honoraria/Allowance outside the submitted work from searchlight Pharma, Meet the experts-Academy, Boehringer Ingelheim, Deutscher Verein für Versicherungswissenschaft e.V., DFG (call for establishment of international cooperation).