Except for some legless and snake-like reptile species, lizards are quadrupedal squamates. The skin of lizards is different from that of mammals and contains classical skin layers, which can vary in morphology at different positions. They are covered by overlapping keratin scales, enabling them to live in the driest deserts on Earth (6,19). Scales have many important functions, such as playing vital roles in skin permeability and providing protection from abrasion, and therefore tend to be thicker dorsally than ventrally (2,8). The skin participates in maintaining homeostasis to protect against microbial invasion, physical trauma, and environmental damage.

Skin infections are common in lizards and can lead to fatal organ diseases and septicemia (3). Because of the regular ecdysis period, the infection of skin wounds can occur frequently because they have no scales within this period. Some common risk factors may lead to abscesses, including poor hygiene, immune suppression, and trauma (9). Subcutaneous abscesses are pus-filled sores often accompanied by inflammation, which is usually caused by bacterial infection. Other conditions that may appear as abscesses include parasitic infections, tumors, and hematomas. However, a number of species of bacteria, often more than one kind at a time, can be present in reptile abscesses (1,11,17). The present study was conducted to determine how to successfully manage subcutaneous wounds using various laboratory tests and observations of new scar-free repair tissue regeneration in lizard wound healing.

An 8-month old leopard gecko (Eublepharis macularius) with a large nodule was referred to our hospital. A physical examination revealed that the nodule had an unclear boundary from the top of the left eye to the front of the left ear opening. The nodule prevented the patient from opening his left eye. The wound was observed that hard, cheese-like, yellow pus filled the nodule. A pus swab sample of the wound was collected for laboratory tests for cytology and microbial culture. Cytology revealed inflammation consisting of heterophils and macrophages with phagocytized rod-shaped bacteria, indicating bacterial infection (Fig. 1). Ofloxacin (Ocuflox^® ophthalmic ointment, Samil, Seoul, Korea) was selected as the empirical topical antibiotic for the abscess.

Figure 1. Cytology shows pyogranulomatous inflammation with phagocytized rod-shaped bacteria, along with the bacteria in the background, indicating bacterial infection. Diff-Quik stain. ×1000.

The collected swab samples were inoculated in trypticase soy agar containing 5% sheep blood and incubated aerobically at 37°C for 24 h. Under microscopic examination, rod-shaped gram-negative bacteria were revealed via Gram staining (Fig. 2). The Kiryby-Bauer disk diffusion test on 24 antimicrobials (amikacin, gentamicin, enrofloxacin, ciprofloxacin, polymyxin B, streptomycin, amoxicillin/clavulanate, cefotaxime, cefazolin, cefepime, cefovecin, ampicillin/sulbactam, oxacillin, cefoxitin, vancomycin, rifampicin, quinupristin/dalfopristin, imipenem, erythromycin, and trimethoprim/sulfamethoxazole), chloramphenicol, clindamycin, tetracycline, and doxycycline) showed that the isolated bacteria were susceptible to amikacin, gentamicin, enrofloxacin, streptomycin ciprofloxacin, cefotaxime, cefepime, cefoxitin, and trimethroprim/sulfamethoxazole. Molecular identification of the isolated bacteria based on the sequence of the 16S ribosomal RNA gene by using 27F and 1492R primer showed that the identified sequence was 99.85% similar to Serratia surfactantfaciens (GenBank accession no. CP014948). Ofloxacin which was used as the empirical antibiotic, was maintained as the antibiotic for treatment.

Figure 2. Bacterial identification and antimicrobial susceptible test. (A) Morphology of inoculated bacteria in trypticase soy agar with 5% sheep blood. (B) Gram-negative bacteria. Gram staining. ×1000.

On the second visit, the boundaries of the abscess became clear, and a crust covered the surface of the abscess. We removed the crust, followed by the inner pus of the abscess. The inside of the abscess was then flushed several times with saline. By the 4th week, new tissue restoration without scar formation was observed. (Fig. 3).

Figure 3. Wound status and condition of patient. (A) Initial condition of wound with pus. (B) Wound status in which the boundary of the wound become clear after empirical antibiotic treatment. (C) New tissue restoration of wound after 1 week of pus removal and tissue debridement.

This case demonstrates that treatment according to the appropriate diagnostic procedures for locally occurring gecko abscesses can result in rapid and scar-free healing. In particular, when an abscess develops and invades the surrounding tissues, clearing the boundaries of the abscess through rapid antibiotic treatment shows that the subcutaneous abscess aggregates in the form of a lump, making it easier to physically remove.

Abscesses in reptiles are caused by the accumulation of trapped white blood cells. This trapping is called encapsulation because white blood cells are contained in the capsule of the tissue. This encapsulation of white blood cell material typically causes firm swelling or the formation of masses. Reptiles do not have enzymes that can break down or turn white blood cell material into liquid pus as in mammals (3).

Cytologically, a mass in the skin can be formed due to neoplasia, inflammation, or both. Inflammation can be classified as infectious or non-infectious. To differentiate the etiology of wounds, cytology can also be applied to swab samples from lesions in lizards (11). Generally, in mammals, neutrophils massively infiltrate the wound during the first 24 h post-injury (14) and are attracted by degradation products from pathogens and by the numerous inflammatory cytokines produced by activated platelets and endothelial cells. Macrophages massively infiltrate the wound after the first 24 h post-injury and exacerbate intense phagocytic activity during this stage (16). Heterophils, a type of granulocyte equivalent to mammalian neutrophils, are recruited to the wound site to participate in the phagocytosis of tissue debris and defense of various microbes in reptiles. Immunostaining revealed that these heterophils inhibit rather than trigger inflammation (7). In this case, we noted pyogranulomatous inflammation consisting of heterophils and macrophages phagocytizing rod-shaped bacteria, suggesting a chronic stage of bacterial infection. Bacterial culture and antibiotic susceptibility testing indicated that S. surfactantfaciens, a member of the Enterobacteriaceae group, was the causative agent of the lesion, indicating that the infection can originate from poor hygiene in the cage. Due to fluoroquinolone susceptibility, the lizard lesion infection was well-treated 3 consecutive week with ofloxacin.

The basic methods for wound management include primary closure, secondary intention, wound healing, and delayed primary closure methods. The first step in subcutaneous wound treatment is to irrigate the injured tissue. The next step in wound management is to reduce the natural tension placed on the wound via the sharp dissection of the devitalized tissue. Aggressive debridement is the key to facilitating epithelium regeneration. Flushing and wound cleaning are then performed. Surgical removal and wound closure methods vary among veterinarians (18). Many wounds, especially those that may be contaminated, are best managed with second-intention wound healing (20); the basic nature of this healing is wound contraction from natural epithelial migration, which can take days to weeks (11). In this case report, we managed the wound using a drainage pressure method without surgical closure, and wound healing was clearly noted after 1 week of necrotic tissue removal and aggressive debridement.

Wound healing is a dynamic morphogenetic event, which includes the activation of multiple intracellular and extracellular processes. It yields two possible outcomes: (6) the wound site is repaired with fibrotic scar tissue, or (19) the wound site undergoes scar-free healing and the original tissue is restored. Scar-free wound healing, as commonly demonstrated by urodeles, restores new tissue structure and, in most instances, occurs in reptiles (4). Unlike scar formation, scar-free healing involves more a rapid closure of the wound epithelium and a delay in blood vessel development and collagen deposition within the wound bed (5,10,12). Instead of replacing damaged tissue with a fibrous infill, the lizard undergoes a tissue-specific program to restore tissue architecture and function since blood vessels exist in multiple layers in the dermic skin layer. Adequate blood supply formation for wound healing can be achieved. In addition, regeneration in lizards is often paired with structural adaptations that minimize tissue damage and facilitate recovery. Although the entire epidermis and up to 90% of the dermis are initially sloughed off, the site of mutilation is completely restored over time. A similar mode of skin shedding (60% of the total dorsal body surface area) and subsequent regeneration have been documented in spiny mice (Acomys spp.) (15). Others, such as the green iguana (Lguana iguana), cannot heal scar-free (13), indicating that scar-free cutaneous repair is not a universal trait in lizards. Wound reparative phenomena are complex, varied, and influenced by numerous features. Our case showed complete scar-free wound healing and new tissue regeneration in a lizard. This may be due to the optimal antibiotic treatment and wound management methods combined with acute diagnostic laboratory tests.

This subject was supported by a National Institute of Wildlife Disease Control and Prevention as “Specialized Graduate School Support Project for Wildlife Diseases Specialists”.

The authors have no conflicting interests.