Pseudoglutamicibacter cumminsii (Formerly Arthrobacter cumminsii)

Ecology and relationship to the human microbiota

The organism belongs to an environmentally associated group, commonly linked to soil. However, its repeated recovery from human urogenital samples has prompted the hypothesis that it can also inhabit human skin or mucosal sites, particularly the genitourinary tract.

The 2025 study supports a colonising or opportunistic role, but cannot establish the organism’s normal carriage prevalence [Carlos J Téllez-Castillo 2025]

Microbiological characteristics

It is an aerobic, catalase-positive, Gram-positive coryneform organism

Despite its former placement in Arthrobacter, a typical rod–coccus growth cycle was not observed on sheep blood agar in that study. It also lacked the characteristic cheese-like odour associated with some Brevibacterium species.

MALDI-TOF MS has been used to identify the organism in recent case reports and the 2025 outpatient series. Both Bruker and bioMérieux platforms appear in the retrieved clinical literature.

[Funke 1998]

Clinical disease

Funke and colleagues described isolates from:

• Urinary tract infection.
• Vaginal and cervical specimens.
• Infected amniotic fluid.
• Chronic otorrhoea and external otitis.
• Deep soft-tissue infection and a leg wound.
• Calcaneal osteomyelitis.
• Blood cultures, including a patient described as having urosepsis.

The stronger observations included pure urine cultures with approximately to greater than CFU/mL and a pure deep-tissue culture associated with a leucocyte response. Other isolates were recovered with organisms such as Enterobacteriaceae, enterococci, Staphylococcus aureus or Corynebacterium striatum.

Téllez-Castillo and colleagues examined 116 isolates from outpatient specimens in Germany collected between January 2021 and February 2023.

UTI

Urinary recovery is the most consistent association. In 1998, three patients had pure cultures at 10⁴ to >10⁵ CFU/mL; another urinary culture contained enterococci and Enterobacteriaceae. The authors considered selected UTIs plausible but judged overall pathogenicity low. Clinical outcome evidence was limited.

The 2022 report involved a 34-year-old woman with persistent urinary symptoms after two fosfomycin doses. Pure growth exceeded 100,000 CFU/mL. MALDI score was 1.65, but identification was supported by 16S sequencing (MZ293797). The authors reported improvement after doxycycline (!) 100 mg for seven days, without a follow-up specimen.

The 2023 report involved a 17-year-old with myasthenia gravis receiving corticosteroids 10 mg/day. Urinary frequency was the only specific urinary symptom described; pure growth exceeded 100,000 CFU/mL. The authors used ceftriaxone 2 g/day for seven days. A MALDI score of 1.65 without reported sequencing, absent detailed MIC methodology and limited outcome information weaken species-specific inference. The report’s broad statements about which drugs are “allowed” in myasthenia gravis are not reproduced as clinical guidance.

Some case reports

• UTI - A case report of urinary tract infection from Pseudoglutamicibacter cumminsii in an immunosuppressed patient - PMC
• Osteomyelitis - Pseudoglutamicibacter cumminsii in polymicrobial osteomyelitis of the tibia in a female patient – a case report - PMC
• Blood culture - Isolation and whole genomic analysis of mesophilic bacterium Pseudoglutamicibacter cumminsii in epithelial mesothelioma - PMC

Pathogen or coloniser?

The overall evidence favours an organism that commonly appears as a coloniser or incidental co-isolate but can plausibly contribute to selected infections. Assess clinically and allocate greater importance if repeatedly isolated or isolated from a sterile site. Highest association has been seen with UTI.

Antimicrobial susceptibility

• Beta-lactam: Across the available studies, many isolates have low β-lactam MICs. β-lactamase activity was not detected in either the 1998 or 2025 tested collections.
• Fluoroquinolone activity is inconsistent. The 1998 authors favoured a possible intrinsic explanation because elevated quinolone and aminoglycoside MICs were widespread in their collection. The 2025 authors instead proposed acquired quinolone target mutations.
• original series found poor aminoglycoside activity.
• Macrolide, clindamycin and tetracycline susceptibility cannot be assumed. Some tetracycline resistance was already present in the original series. The 2024 bone isolate was reported resistant to erythromycin, clindamycin, ciprofloxacin and moxifloxacin
• Low rifampicin MICs (as standard rifampicin monotherapy if not recommended)

The table below reproduces selected reported MIC₉₀ values.

These collections used different methods and selection criteria; their differences are not a demonstrated trend over time. In 1998, the Merlin microdilution method used H medium; in 2025, MICRONAUT testing also used H medium.

In R11, piperacillin–tazobactam MIC₉₀ is 0.0625 mg/L in the prose and 0.625 mg/L in the table; it is excluded here.

Genomics, putative virulence and cancer claims

Xu et al. reported blood isolate XJ001/PC1 in a 36-year-old man with epithelial mesothelioma. The assembled genome was 2,179,930 bp, GC content 61.23%, with 1,922 predicted genes; BioProject PRJNA1090324 was provided.

Reference (what was checked)

1. [R1] LPSN. Arthrobacter cumminsii: synonymy, correct name, nomenclatural dates and type strain. Record inspected 9 November 2026.
2. [R2] Funke G, Hutson RA, Bernard KA, et al. Isolation of Arthrobacter spp. from clinical specimens and description of Arthrobacter cumminsii sp. nov. and Arthrobacter woluwensis sp. nov. J Clin Microbiol. 1996;34:2356–2363. doi:10.1128/jcm.34.10.2356-2363.1996.
3. [R3] Funke G, Pagano-Niederer M, Sjödén B, Falsen E. Characteristics of Arthrobacter cumminsii, the most frequently encountered Arthrobacter species in human clinical specimens. J Clin Microbiol. 1998;36:1539–1543. doi:10.1128/jcm.36.6.1539-1543.1998.
4. [R4] Mages IS, Frodl R, Bernard KA, Funke G. Identities of Arthrobacter spp. and Arthrobacter-like bacteria encountered in human clinical specimens. J Clin Microbiol. 2008;46:2980–2986. doi:10.1128/JCM.00658-08.
5. [R5] Chaves Blanco L, Gómez-Camarasa C, Illescas López M, et al. Unusual isolation of Pseudoglutamicibacter cumminsii in urine culture. Rev Esp Quimioter. 2022;35:95–96. Online 29 November 2021. doi:10.37201/req/088.2021.
6. [R6] Puca E, Koci M, Puca E, Como N. A case report of urinary tract infection from Pseudoglutamicibacter cumminsii in an immunosuppressed patient. New Microbes New Infect. 2023;53:101133. doi:10.1016/j.nmni.2023.101133.
7. [R7] Odeberg G, Bläckberg A, Sunnerhagen T. Infection or contamination with Rothia, Kocuria, Arthrobacter and Pseudoglutamicibacter—a retrospective observational study of non-Micrococcus Micrococcaceae in the clinic. J Clin Microbiol. 2023;61:e01484-22. doi:10.1128/jcm.01484-22.
8. [R8] Ioannou P, Maraki S, Velivasakis E, Kofteridis DP. Pseudoglutamicibacter cumminsii in polymicrobial osteomyelitis of the tibia in a female patient—a case report. Germs. 2024;14:95–100. doi:10.18683/germs.2024.1421.
9. [R9] Fukushima S, Fujimori T, Hagiya H. Mimicker of Gram-positive Staphylococci. Int J Infect Dis. 2024;146:107145. doi:10.1016/j.ijid.2024.107145.
10. [R10] Xu N, Wu K, La T, Cao B. Isolation and whole genomic analysis of mesophilic bacterium Pseudoglutamicibacter cumminsii in epithelial mesothelioma. Heliyon. 2024;10:e35617. doi:10.1016/j.heliyon.2024.e35617.
11. [R11] Téllez-Castillo CJ, Müller L, Rekendt AK, Pra-Mio L, Scharmann C. Pseudoglutamicibacter cumminsii in outpatient samples: analysis of isolates and antimicrobial susceptibility. Rev Esp Quimioter. 2025;38:412–419. doi:10.37201/req/060.2025.
12. [R12] EUCAST. Clinical breakpoint tables: current landing page listing version 16.1, valid 24 June–31 December 2026.
13. [R13] EUCAST. When there are no breakpoints? Current page, guidance dated 10 July 2026.
14. [R14] EUCAST. When there are no breakpoints! News explanation, 9 November 2024.
15. [R15] UKHSA. AMRHAI bacterial identification request form; specialist and reference microbiology services.
16. [R16] UKHSA. Bacteriology Reference Department user manual, July 2026. BIDS service description.
17. [R17] EUCAST. Revised EUCAST guidance document on “When there are no breakpoints”. 10 July 2026.