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Revisiting rhinoscleroma microbiology: a case with concordant dual-specimen bacterial isolation

Drago L, Papanikolau N, Preti A, Mozzanica F, De La Motte LR, Pelosi G, Deflorio L

Frontiers in cellular and infection microbiology, 2026

Abstract

Background: Rhinoscleroma is a chronic granulomatous infection of the upper airway traditionally considered a monomicrobial disease caused by Klebsiella pneumoniae subsp. rhinoscleromatis. However, limited use of deep-tissue microbiological sampling may have contributed to underrecognition of additional bacterial isolates and microbial complexity.

Methods: We report a biopsy-confirmed case of nasal rhinoscleroma in a previously healthy adult. Histopathological evaluation and microbiological analysis were performed on deep intranasal tissue. Bacterial identification was conducted using VITEK 2 and MALDI-TOF mass spectrometry. Antimicrobial susceptibility testing was interpreted according to EUCAST 2025 criteria.

Results: Histology demonstrated characteristic Mikulicz cells. Microbiological analysis revealed K. pneumoniae (consistent with subsp. rhinoscleromatis) together with Morganella morganii from deep-tissue biopsy. Importantly, both organisms were also recovered from an independent nasal swab specimen, with concordant antimicrobial susceptibility profiles. M. morganii showed resistance to aminopenicillins and amoxicillin-clavulanate while remaining susceptible to piperacillin-tazobactam, consistent with its intrinsic AmpC β-lactamase profile. Microbiological findings prompted targeted modification of antimicrobial therapy, and targeted therapy with oral levofloxacin was initiated.

Conclusion: This case suggests possible microbial complexity in rhinoscleroma and…

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