Pyogranulomatous dermatitis with Enterococcus faecalis in a spotted seal (Phoca larga)

Abstract

Background: Cutaneous infections are important diseases in captive and free-ranging pinnipeds and are associated with various causative agents. Some special agents, such as fungi, morbillivirus and mycobacteria, can cause cutaneous specific granulomatous inflammation.

Objectives: To identity the cause of chronic dermatitis in a spotted seal in an aquarium.

Methods: Herein, we analyze the clinical history and cutaneous samples of the spotted seal through differential diagnosis (histopathology, microorganism culture, special histochemical staining methods, PCR), and antibiotic susceptibility test.

Results: This is a rare pyogranulomatous dermatitis case caused by E. faecalis in a captive adult male spotted seal (Phoca largha) in an aquarium.

Conclusions: We provide a meaningful approach to the diagnosis and treatment of bacterial dermatitis in pinnipeds.

Keywords: dermatitis, Enterococcus faecalis; pyogranulomatous; spotted seal.

FIGURE 1

Gross morphology of the infectious skin. (a) The size of fusion cutaneous lesion is approximately 25 × 20 cm in diameter. (b) Multiple cream‐like suppurative zones varying in size are distributed in the middle area of the dermis (arrow)

FIGURE 2

Histopathological changes in cutaneous lesions. (a) The structure of the epidermis and the papillary layer is clear and intact. The primary lesion is mainly located in the deep reticular layer of the dermis and its boundary is not clear. Some lymphocyte foci are distributed in the deeper dermis (arrow). E: the epidermis layer; L: the lesions in dermis. (b) The lesion is constructed of numerous oval masses of epithelioid cells. Dead neutrophils are in the centre of these masses, and the epithelioid cells phagocytised the neutrophils and cocci (The magnified image at the upper right corner). (c) Numerous lymphocytes, plasma cells, capillaries and a few multinucleated giant cells (M) are observed around the masses of epithelioid cells. (d) Liquefaction necrosis (purulency) is located in the margins of the lesions (S). Captured by 3DHISTECH PANNORAMIC 250 Flash III DX and SlideViewer Ver 2.5

FIGURE 3

Histochemical staining of skin lesions. (a) Numerous mast cells are located in suppurative foci. TB stain. (b) Fibre proliferated mildly in infected foci. L: infected foci; Ds: the fibrous tissue of the dermis. Mallory trichrome stain. (c) No fungal hyphae are observed in the infected area. PAS stain. (d) There is no fluorescent signal of acid‐fast bacteria in the infected area. Acid‐fast (fluorescence) stain. a, b and c are captured by Olympus CX43 microscope and EPview Ver 1.2. d is captured by Olympus BX53 fluorescence microscope and cellSens standard Ver 3.1

FIGURE 4

Bacteria isolated from infected skin samples. Bacteria are Gram‐positive cocci that arrange in chains or clumps. The magnification is in the upper right corner. A single Gram‐positive coccus (arrowhead). Gram stain. Captured by Olympus CX43 microscope and EPview Ver 1.2

FIGURE 5

Alignment and phylogenetic tree based on the 16S rRNA gene sequences. (a) Alignment analysis. The 16S rRNA gene in this study shares a high identity (from 99.5% to 99.7%) with that of other E. faecalis strains but shares an 83.6% identity with the Streptococcus pyogenes strain (NR028598.1). (b) Phylogenetic tree. The Streptococcus pyogenes 16S rRNA sequence is used as an outgroup. The phylogenetic tree shows that the bacterial isolate is related to 10 other isolates of E. faecalis in GenBank; *the E. faecalis isolate in the case. The phylogenetic tree is constructed with MEGA‐7 software