Granulomatous lobular mastitis (GLM) is a rare benign breast inflammatory disease that affects women of childbearing age. Corynebacterium species, especially Corynebacterium kroppenstedtii, was reported as the pathogen of GLM. A recent study showed that the C. kroppenstedtii complex is composed of C. kroppenstedtii and two novel species, C. parakroppenstedtii and C. pseudokroppenstedtii. The study presents seven C. kroppenstedtii-like strains isolated from GLM patients. However, they turned out to be six strains of C. parakroppenstedtii and one strain of C. pseudokroppenstedtii according to 16sRNA sequencing. In order to conduct a phylogenetic study, we further sequenced the fusA and rpoB genes, which were frequently employed in studies of Corynebacterium species. Novel Mass Spectral Peaks (MSPs) for C. parakroppenstedtii were created with Bruker MALDI-TOF MS. Then, the identification power of the MSPs was tested by C. parakroppenstedtii strains and remotely related Corynebacterum spp. The antibiotic sensitivity tests were performed according to the CLSI M45 guidelines. All of the strains were not resistant to β-lactams, vancomycin or linezolid. However, applying erythromycin and clindamycin could be fruitless. Phenotypic identification using a Vitek2 ANC ID card proved all of the C. parakroppenstedtii strains were identified as Actinomycete naeslundii. The test of Ala-Phe-Pro arylamidase and urease could be employed as the characteristics to distinguish C. pseudokroppenstedtii from C. parakroppenstedtii. Here, we present the identification, antibiotic sensitivity tests (ASTs) and epidemiological investigation of two novel C. kroppenstedtii-like species with the purpose of improving the understanding of C. kroppenstedtii-like species and related diseases.

Purpose: The adenoid microbiota plays a key role in adenoid hypertrophy (AH). This study explored the molecular epidemiology and antimicrobial resistance of Haemophilus. Influenzae (H. influenzae) strains in pediatric AH patients. Methods: Retrospective analysis of pediatric AH patients undergoing endoscopic adenoidectomy. Adenoid tissue samples were cultured to screen for pathogens. H. influenzae strains were identified by 16S rRNA sequencing and serotyped via q-PCR. Multilocus sequence typing (MLST) and ftsI gene analysis were conducted using PubMLST. β-lactamase genes (bla_TEM-1, bla_ROB-1) were detected by PCR, and antibiotic susceptibility testing (AST) was performed using the Etest method. For imipenem-resistant strains, the acrRAB efflux pump gene cluster and ompP2 porin gene were sequenced and compared with those of the wild-type strain Rd KW20. Results: Over 8 months, 56 non-duplicate H. influenzae strains were isolated from 386 patients. The detection rate was highest in children under 5 years (30.5%) compared to those aged 5–10 years (13.4%) and 10–15 years (8.7%). Of 49 sub-cultured strains, all were non-typeable H. influenzae (NTHi). MLST identified 22 sequence types (STs) and 13 clonal complexes (CCs), with CC11 (26.5%), CC3 (14.3%), and CC107 (14.3%) being predominant. Common STs included ST103 (22.4%), ST57 (10.2%), and ST107 (10.2%). Most strains belonged to the ftsI group III-like+ (57.1%). β-lactamase positivity was 98.0% (48/49), with bla_TEM-1 (95.9%) and bla_ROB-1 (18.4%) detected. AST showed low susceptibility to ampicillin (10.2%), amoxicillin–clavulanate (34.7%), azithromycin (12.2%), and trimethoprim–sulfamethoxazole (14.3%). Among the β-lactamase-positive strains, 44/48 were β-lactamase-positive ampicillin-resistant (BLPAR); none were β-lactamase-negative ampicillin-resistant (BLNAR). Imipenem susceptibility was 91.8% (45/49). No carbapenemases were found in the imipenem-resistant strains, but mutations in acrRAB (88.12–94.94% identity) and ompP2 (77.10–82.94% identity) were observed. Conclusions: BLPAR NTHi strains of CC11 are major epidemic strains in pediatric AH. Imipenem resistance in H. influenzae likely results from porin mutations rather than carbapenemase activity. Enhanced surveillance of H. influenzae’s role in AH and its resistance patterns is warranted.

Correction on: Qin J-H, Lyu Q-M, Zhao X-Y, Liu L and Xiao N (2026) Whole-genome characterization of seven multidrug-resistant Neisseria gonorrhoeae isolates from a single tertiary center in Beijing. Front. Microbiol. 17:1882940. doi: 10.3389/fmicb.2026.1882940There was an error in the placement of Figure 1 The original version of this article has been updated..