Four mice: 3-month-old, female MyD88-/- mus musculus B6/JMyD88N11F4 (Mus musculus)The mice are in a full-service room, group housed, on a ventilated rack. Four mice were found with torticollis. The mice were bright, alert, responsive and in good body condition. The laboratory requested a necropsy with culture and sensitivity of the tympanic bullae. Rule outs for head tilt in mice include otitis media/interna, central nervous system disease, and necrotizing arteritis of undetermined cause.

The laboratory has had a number of mice with head tilts in the past and is interested in determining the cause in order to treat or prevent further outbreaks of disease. This is an immune-compromised line that currently is not on antibiotic prophylaxis.

Gross Description:  

Mice 1 3: Head tilt to the left
Mouse 4: Head tilt to the right
Mice 1 4: White opaque material within the tympanic bullae
Mice 1, 2, 4: Swollen right forepaw (up to 0.6 CM in maximum dimension)
Mouse 3: Not foot lesions

Histopathologic Description:

The forepaw is markedly expanded by numerous coalescing botryoid pyogranulomas centered on 100-200 um colonies of Gram-positive cocci, surrounded by brightly eosinophilic amorphous material (Splendore-Hoeppli) (Figs. 4-1 and 4-2). These pyogranulomas contain a central core of abundant necrotic debris admixed with numerous neutrophils, surrounded by layers of epithelioid macrophages, fewer lymphocytes and plasma cells, and finally, outer layers of fibroblasts and collagen. In the adjacent tissue there is marked thinning and loss of bone of the distal phalanges. In addition, there is edema with macrophages, lymphocytes, and plasma cells within the subcutaneous tissue.

Morphologic Diagnosis:  

Cellulitis, pyogranulomatous and necrotizing, focally extensive, subacute, severe with Splendore-Hoeppli material and large colonies of cocci

Mice 1 4: Nasal pharynx culture
Mice 1 3: Tympanic bulla culture
Mice 1, 2, 4: Forepaw cultured

Lab Results:  

Microbiology Results
1FootMD717948S. aureusR S SSRS
2FootMD717949S. aureusR S SSRS
4FootMD717950S. aureusR S SSRS
P. mirabilisS S SRSS
4FootMD717951S. aureusRRS SSRS
1-4NPXMD717952P. mirabilisProteus mirabilis predominate in all the specimens from the Middle Ear, and 3 of 4 of the Nasal wash had it.
1-3Typanic Bulae

Complete Antibiotic Culture and Sensitivity Profile: S = Susceptible; R = Resistant
AntimicrobialStaph. aureusProteus mirabilis
Amox/Clav AMLSS
Trimethroprim, SulfamethoxazoleSS



Contributor Comment:  

Myeloid differentiation factor 88 (MyD88) knockout mice have been shown to be deficient in the production of an innate immune response.(7,8,12) Neutrophil function is compromised due to the deletion of MyD88 from the signaling pathway of toll-like receptors (TLR). The immune response has also been shown to be delayed due to failure of proinflammatory cytokines and induction of NF-kB and MAP-kinase pathways.(1,2,12) Impairment of macrophage function, especially in the production of IL-6 and TNF-a, has been shown in response to LPS, peptidoglycan, and lipopeptides.(7,14) The model has also been shown deficient in the response to exogenous IL-1 as the production of TNF-a and IL-6 is muted.(13) The failure of a normal macrophage response also resulted in a decreased B cell response. Although the initial response to LPS in diminished, the overall deleterious effects to the animal are increased as sepsis results in hyperinflammation.(12) The decreased immune response of MyD88 knockout mice has been described in a variety of tissues, including brain (7), skin (10), and generalized infections.(12)

Reported causative agents of botryomycosis include Staphylococcus aureus, S. hominus, S. xylosus, Pseudomonas aeruginosa, Proteus spp., Escherichia coli, Nocardia asteroides and Streptococcus intermedius, with a variety of other aerobic and anaerobic bacterial agents implicated.(3,9,11,14,15) Immunosuppression has been suggested as a factor in increased prevalence of botryomycosis.(11,16) As described above, the MyD88 knockout mouse is deficient in the innate immune response.

Splendore-Hoeppli staining refers to the deeply eosinophilic material that surrounds the -�-�grains of bacterial colonies contained centrally. The eosinophilic material is described as having a coronal appearance, which engulfs whitish purulent material associated with the colonies(3,14,15). Necrotic tissue has also been reported to be present.(3) While Splendore-Hoeppli bodies are predominately reported to be associated with botryomycosis, numerous reports of this phenomenon in the presence of parasitic (3) or fungal infections (4,15,16) are in the literature. The eosinophilic staining component of this histologic finding has been linked to cellular debris and antigen-antibody complexes.(3,11,15) This staining pattern has been referred to as Splendore-Hoeppli bodies, material, and phenomenon.

The lesions in the forepaw were subsequently determined to be secondary to toe-clip for identification. The colony was subsequently placed on Baytril and there were no further lesions.

JPC Diagnosis:  

Digits, foreleg: Cellulitis, pyogranulomatous and necrotizing, subacute, focally extensive, severe with osteolysis, Splendore-Hoeppli material and large colonies of cocci.

Conference Comment:  

Botryomycosis, a disease of the skin and subcutis, is caused by nonfilamentous bacteria that form grossly visible colonies that look like granules or spicules within a chronically affected lesion. This condition generally affects the skin, but it can extend into deeper tissues if left untreated. Rule outs for these lesions include actinomycotic and eumycotic mycetomas. Infections generally start after trauma to the skin or wound contamination.(6)

Botryomycosis usually manifests as a firm nodule that is ulcerated with a draining tract. The discharge often contains the previously described granules or spicules, thus suggesting botryomycosis. Histologically, this is a striking lesion with a marked pyogranulomatous response centered on bacterial colonies often encircled by Splendore-Hoeppli material. These lesions can be walled off by abundant fibrous connective tissue and can coalesce to form chains of granulomas within the subcutis and surrounding tissues.(6)


1. Akira S and Takeda K: Toll-like receptor signaling. Nature Reviews 4:499-511, 2004
2. Akira S: Toll-like receptors: lessons from knockout mice. Biochem Soc Trans 28:Part 5, 2000
3. Armed Forces Institute of Pathology: Wednesday Slide Conference, Conference 13, Case 1, AFIP #2812387, Conference Comments, 2006
4. Bersoff-Matcha Sj, Roper CC, Liapis H, and Little JR: Primary Pulmonary Botryomycosis: Case Report and Review. Clin Infec Dis 26:620624, 1998
5. EL van den Berk G, Noorduyn LA, van Ketel RJ, van Leeuwen J, Bemelman WA, and Prins JM: A fatal pseudo-tumour: disseminated basidiobolomycosis. BMC Infectious Diseases 6:140, 2006
6. Ginn PE, Mansell JEKL, Rakich PM: Skin and appendages. In: Jubb, Kennedy and Palmers Pathology of Domestic Animals, ed. Maxie MG, 5th ed., pp. 691. Elsevier, Philadelphia, Pennsylvania, 2007
7. Goldstein DR, Tesar BM, Akira S, and Lakkis FG: Critical role of the Toll-like receptor signal adaptor protein MyD88 in acute allograft rejection. J Clin Invest 111(10): 1571-1578, 2003
8. Kielian T, Phulwani NK, Esen N, Syed MM, Haney AC, McCastlain K, and Johnson J: MyD88- dependent signals are essential for the host immune response in experimental brain abscess. J Immunol 178:45284537, 2007
9. Machado CR, Schubach AO, Concei+�-�+�-�o-Silva F, Quintella LP, Louren+�-�o MCS, Carregal E, and do Valle ACF: Images in Clinical Dermatology. Dermatology 211:303-304, 2005
10. Rodig SJ and Dorfman DM: Splendore-Hoeppli phenomenon. Arch Pathol Lab Med 125:1515-1516, 2001
11. Schlossberg D, Pandey M, and Reddy R: The Splendore-Hoeppli phenomenon in hepatic botryomycosis. J Clin Pathol 51:399-400, 1998
12. Sugawara I, Yamada H, Mizuno S, Takeda K, and Akira S: Mycobacterial infection in MyD88- deficient mice. Microbiol Immunol 47(11):841-847, 2003
13. Tohno M, Skimazu T, Aso H, Kawai Y, Saito T, and Kitazawa H. Molecular Cloning and Functional Characterization of Porcine MyD88 Essential for TLR Signaling. Cell Mol Immunol 4(5):369-376, 2007
14. Weighardt H, Kaiser-Moore S, Vabulas RM, Kirschning CJ, Wagner H, and Holzmann B: Cutting edge: Myeloid differentiation factor 88 deficiency improves resistance against sepsis caused by polymicrobial infection. J Immnunol 169:28232827, 2002
15. Zaharopoulos P: Fine-needle aspiration cytologic diagnosis of lymphocutaneous sporotrichosis: A aase report. Diag Cytopathol 20(2):74-77, 1998
16. Zavasky D, Samowitz W, Loftus T, Segal H, and Carroll K: Gastrointestinal zygomycotic infection caused by basidiobolus ranarum: Case report and review. Clin Infec Dis 28(6):1244-8, 1999

Click the slide to view.

4-1. Forepaw, mouse.

4-2. Forepaw, mouse. 

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