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

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.

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.

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.

This case suggests possible microbial complexity in rhinoscleroma and highlights the value of deep-tissue and concordant multi-sample microbiological evaluation. Recognition of co-isolated organisms may have implications for antimicrobial selection and stewardship, although their pathogenic contribution requires further investigation.