Rare Pathogen in Diabetic Foot Gangrene: A Case of Wohlfahrtiimonas chitiniclastica Infection

Summary

A 76-year-old diabetic male with chronic foot ulcers and gangrene, complicated by maggot infestation, was diagnosed with Wohlfahrtiimonas chitiniclastica through metagenomic sequencing. Debridement, ertapenem therapy, and wound reconstruction achieved recovery, underscoring the importance of early detection and advanced diagnostics for rare pathogens in immunocompromised patients.

Abstract

Wohlfahrtiimonas chitiniclastica is a rare Gram-negative bacterium typically associated with wound infections, particularly in immunocompromised patients or individuals exposed to unsanitary conditions. Although clinical cases are infrequent, the infection can lead to severe complications such as bacteremia, septic shock, and even death if unrecognized or inadequately treated. We present the case of a 76-year-old diabetic male who developed chronic, non-healing foot ulcers complicated by gangrene and maggot infestation. Diagnostic challenges were addressed using metagenomic next-generation sequencing, which identified W. chitiniclastica alongside Proteus mirabilis and Corynebacterium striatum. Management included aggressive surgical debridement to remove necrotic tissue, local application of gentamicin-impregnated bone cement, systemic antibiotic therapy with ertapenem, and wound reconstruction using a dorsally based fascial flap. This combined approach resulted in significant clinical improvement, progressive wound healing, and marked reductions in infection markers. The case highlights the decisive role of advanced sequencing technologies in identifying rare pathogens within polymicrobial infections, where conventional methods such as MALDI-TOF mass spectrometry may fail. It also emphasizes the importance of integrating precision diagnostics with surgical intervention, targeted antimicrobial therapy, and rigorous postoperative care to achieve successful outcomes. By documenting this unusual presentation, we aim to expand clinical awareness of W. chitiniclastica infections and provide a practical framework for managing similarly complex diabetic foot infections.

Introduction

Wohlfahrtiimonas chitiniclastica is a Gram-negative, non-motile rod capable of colonizing various hosts under both aerobic and anaerobic conditions, with significant chitinase activity that plays an important role in the metamorphosis of parasitic flies^1,2. Female flies deposit eggs on mucosal surfaces and wounds, creating an infection nidus. The larvae feed on liquid bodily fluids, ingested food, or live and necrotic host tissues for a period of time³. Although infections are rare, the number of clinical reports is increasing, particularly in immunocompromised patients or thos....

Protocol

Written informed consent was obtained from the patient for the publication of clinical details and clinical images, per institutional guidelines. Patient identifiers were anonymized in all documentation.

1. Patient evaluation and initial assessment

1. A comprehensive medical history was obtained, focusing on diabetes mellitus duration, glycemic control (HbA1c levels), history of peripheral vascular disease, and prior interventions (e.g., pacemaker implantation). Chronic foot ulcer progression and maggot infestation were documented.
2. Physical examination assessed right foot swelling, necrotic tissue (third ....

Results

The 76-year-old diabetic male with chronic right foot gangrene and maggot infestation (Figure 1 and Figure 2) underwent comprehensive management, including radical debridement of necrotic tissue, removal of osteomyelitic foci, and wound reconstruction using a dorsally based fascial flap. Metagenomic next-generation sequencing (mNGS) of intraoperative specimens identified Wohlfahrtiimonas chitiniclastica as the primary pathogen, with 97.96% genome covera.......

Discussion

Wohlfahrtiimonas chitiniclastica is a rod-shaped, Gram-negative, nonfermenting bacterium that is oxidase- and catalase-positive. It was first discovered in the larvae of the parasitic fly Wohlfahrtia magnifica⁶. Female flies lay eggs on wounds and mucosal surfaces, generating an infection nidus. The larvae feed for a period of time on necrotic or viable host tissues, bodily fluids, or ingested food³. Several factors, including low socioeconomic status, adv.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Agilent 2100 HS DNA Kit	Agilent Technologies, Santa Clara, CA, USA	5067-4626 (DNA 1000) / 5067-4627 (DNA HS)*	Used for library quality control and fragment analysis
Agilent 2100 HS DNA, Qubit 3.0	Agilent Technologies, Santa Clara, CA, USA	G2939BA	Instrument for library QC, paired with HS DNA Kit
bioMérieux VITEK 2 system	bioMérieux, Marcy-l'Étoile, France	414532	Automated microbial identification and antimicrobial susceptibility testing
Illumina NextSeq 500	Illumina Inc., San Diego, CA, USAIllumina Inc.,	SY-415-1001	High-throughput sequencing platform
QIAamp UCP Pathogen DNA Kit	High-throughput sequencing platform	50214	Pathogen DNA extraction with host DNA depletion
Qubit 3.0 fluorometer	Thermo Fisher Scientific, Waltham, MA, USA	Q33216	DNA and RNA quantification
Siemens SOMATOM Definition AS 64-slice	Siemens Healthineers, Erlangen, Germany	N/A	Used for computed tomography angiography (CTA) imaging