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Eubacterium yurii subspecies margaretiae is resistant to nonopsonic phagocytic ingestion
E Kerosuo1, M Haapasalo, K Lounatmaa
1Department of Cariology, University of Helsinki, Finland.
Abstract:
We have previously shown that strains of Eubacterium yurii are hydrophobic, as compared with human polymorphonuclear leukocytes (PMNs), possibly because of a crystalline surface layer (S-layer) covering the cell envelope of this potential endo-perio pathogen. The aim of the present study was to investigate the phagocytic ingestion by PMNs of the three E. yurii subspecies, with special attention to bacterial surface structures and hydrophobicity. Type strains of subspp. margaretiae, yurii, and schtitka, together with three clinical isolates from necrotic root canals, were studied. All strains were hydrophobic when tested by a two-phase partition method. E. yurii subspp. margaretiae strains ATCC43715T, ES4C, and ES14B-8E were resistant to PMN ingestion in the absence of opsonins, whereas strains of the two other subspecies were readily ingested. The presence of a resistant strain (subsp. margaretiae ATCC43715T) did not inhibit the ingestion of a sensitive strain (subsp. schtitka ATCC43716T). Ingestion of E. yurii subsp. margaretiae strains required opsonization by normal human serum or specific antibodies. Electron microscopy revealed an S-layer in all strains and fimbria-like structures in the subspp. margaretiae and yurii strains. The antiserum prepared against the S-protein of E. yurii subsp. margaretiae ATCC43715T showed only slight cross-reactivity with other E. yurii strains and indicated the presence of strain-specific rather than species- or subspecies-specific antigens in the S-protein of E. yurii subsp. margaretiae ATCC43715T. The results suggest that the mere presence of the S-layer or fimbria-like structures cannot explain the susceptibility to ingestion by the PMNs.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Eubacterium yurii subspecies margaretiae resists phagocytosis by human immune cells (PMNs) due to surface structures, unlike other subspecies. Opsonization is required for PMN ingestion of E. yurii subsp. margaretiae.
Area of Science:
- Microbiology
- Immunology
- Oral Pathogen Research
Background:
- Eubacterium yurii strains exhibit hydrophobicity, potentially due to a surface layer (S-layer).
- This bacterium is implicated as an endodontic and periodontal pathogen.
- Previous studies indicated hydrophobicity in E. yurii strains.
Purpose of the Study:
- To investigate the phagocytic ingestion of three E. yurii subspecies by human polymorphonuclear leukocytes (PMNs).
- To correlate bacterial surface structures and hydrophobicity with PMN ingestion.
- To understand the role of S-layer and fimbriae in E. yurii-PMN interactions.
Main Methods:
- Tested hydrophobicity of E. yurii strains using a two-phase partition method.
- Assessed PMN ingestion of E. yurii strains with and without opsonization (human serum, specific antibodies).
- Utilized electron microscopy to visualize bacterial surface structures (S-layer, fimbriae).
- Performed antiserum cross-reactivity tests against S-protein.
Main Results:
- All E. yurii strains tested were hydrophobic.
- E. yurii subsp. margaretiae strains resisted PMN ingestion without opsonins, while other subspecies were readily ingested.
- Ingestion of E. yurii subsp. margaretiae required opsonization.
- Electron microscopy confirmed S-layer in all strains and fimbriae in subsp. margaretiae and subsp. yurii.
- Antiserum showed strain-specific S-protein antigens, with limited cross-reactivity.
Conclusions:
- The S-layer and fimbria-like structures alone do not fully explain the differential susceptibility of E. yurii strains to PMN ingestion.
- Opsonization is crucial for the phagocytosis of E. yurii subsp. margaretiae by PMNs.
- Strain-specific surface antigens may play a role in E. yurii-host immune cell interactions.