Unusual Causes of Skin and Soft Tissue Infections: A Case Series

Abstract

Background: Skin and soft tissue infections (SSTIs) constitute a major infectious syndrome. SSTIs can arise from invasion of organisms through skin due to breach in the anatomical barrier or from the hematogeneous route, secondary to any systemic infections. The common causative micro-organisms are Staphylococcus aureus and Group A, Beta-hemolytic Streptococci (Streptococcus pyogenes). Many SSTIs respond predictably to the empiric treatment, whereas some of them pose a diagnostic as well as therapeutic dilemma, especially in immunocompromised patients or patients giving history of trauma, insect bite, marine contact etc. These cases simulate routine cellulitis clinically, but fail to respond. These SSTIs are usually caused by unusual pathogens like atypical bacteria, mycobacteria or fungi.

Aim and Objectives: We describe four cases of SSTIs due to rare etiologies encountered at a tertiary care hospital, aiming to illustrate clinical presentation, diagnostic strategies and management, thereby enhancing clinical awareness.

Methods: Study Design: Case series. Study Setting: Department of Surgery, Department of Microbiology, R.K. Damani Medical College, Dr. Hedgewar Rugnalaya, Chhatrapati Sambhajinagar, Maharashtra. Study Population: The cases were selected from the Microbiology laboratory database after identification. Study Duration: January 2024 to June 2025. Sample Size: 4

Results: Case 1, 82-year-old male farmer from rural Maharashtra with a one-week history of insidious, progressive right-sided scrotal swelling and pain diagnosed as pyocoele led to a left orchidectomy. Intraoperatively, a testicular abscess was noted. Bacterial Culture on Sheep Blood and MacConkey agar, identified via Vitek 2, confirmed Brucella melitensis. Case 2, 21-year-old female presented with high-grade fever, chills, and a painful perianal swelling that prevented sitting. The abscess was surgically drained; the cavity extended to the perivaginal region. Smears revealed gram-positive budding yeast cells identified as Candida guilliermondii, susceptible to Fluconazole. Case 3, a 61-year-old male with a 9-year history of diabetes presented with diffuse erythema, edema, and tenderness of the left leg. Debridement was performed, and empiric Cefoperazone-Sulbactam was started. Ziehl-Neelsen staining of pus aspirates revealed acid-fast filamentous branching bacilli. Cultures on Blood agar and Lowenstein-Jensen medium confirmed Nocardia species. Case 4, a 26-year-old male presented with fever and a painful swelling on the right thigh following a suspected insect bite. Multiple debridements were required. Systemic workups ruled out diabetes or immunosuppression. KOH mount revealed broad, aseptate, ribbon-like hyphae with wide-angle branching, characteristic of Mucorales.

Conclusions: This case series highlights four distinct instances of soft tissue infections—ranging from scrotal abscesses to lower limb cellulitis—caused by atypical pathogens including Brucella melitensis, Candida guilliermondii, Nocardia species, and Mucorales. These cases underscore the necessity of diligent microbiological investigation, especially when empiric antibiotic therapy fails or clinical presentations are insidious.