The first report of Ignatzschineria indica, Ignatzschineria ureiclastica and Wohlfahrtiimonas chitiniclastica Bacteremia in two patients with fly larvae-infested wounds in Scandinavia

Highlights

• •First Scandinavian sepsis cases from Ignatzschineria indica, Ignatzschineria ureiclastica, Wohlfahrtiimonas chitiniclastica.
• •Calliphora and Lucilia blowflies are vectors for I. indica, I. ureiclastica, W. chitiniclastica.
• •W. magnifica spreads W. chitiniclastica in warmer climates, but not in Scandinavia.
• •MALDI-TOF and genome sequencing confirmed I. indica, I. ureiclastica, W. chitiniclastica.
• •Targeted antibiotics led to recovery from I. indica, I. ureiclastica, and W. chitiniclastica sepsis.

Abstract

We present the first Scandinavian cases of bacteremia caused by Ignatzschineria indica, I. ureiclastica, and Wohlfahrtiimonas chitiniclastica. Two patients with fly larvae-infested wounds were admitted to a Danish hospital in the summer of 2024. The first patient, a 62-year-old male with alcohol overuse and septic shock, had W. chitiniclastica and I. ureiclastica bacteremia, managed with piperacillin/tazobactam and ciprofloxacin. The second, a 67-year-old diabetic male with peripheral vascular disease, had I. indica bacteremia requiring below-knee amputation and targeted antibiotics. Both isolates were identified via MALDI-TOF mass spectrometry and whole-genome sequencing, with antibiotic “susceptibility testing” guiding therapy. Despite severe presentations, both patients survived. These cases highlight the emergence of these pathogens in Northern Europe and reinforce the importance of advanced diagnostics and personalized treatment strategies in myiasis-associated sepsis.

Graphical abstract

Introduction

Ignatzschineria species and Wohlfahrtiimonas chitiniclastica are gut bacteria that in Denmark are known to originate from the larvae of flies in the family Calliphoridae (blowflies, e.g., Calliphora and Lucilia spp.). These bacteria have also been detected in various environmental sources and foods, e.g., in frozen chicken meat and in chicken meat samples obtained from retail markets [1]. Human infections are rare, mostly in patients with chronic wounds, poor hygiene, or comorbidities. Symptoms vary from asymptomatic local infections to severe systemic disease, including bacteremia and osteomyelitis [2]. Increasing reports of these pathogens globally, particularly in association with wound myiasis but also in patients without myiasis, underscore the need for clinical awareness and accurate identification [3].

Case reports

Patient 1

A 62-year-old man admitted in August 2024 was found unresponsive at home with widespread fly larvae-infested wounds. He lived in unsanitary conditions, had a history of alcohol overuse, no known comorbidities, and was likely unconscious for 24-48 hours before discovery. On admission to Zealand University Hospital, Nykøbing F, examination revealed extensive cellulitis and larval infestation of his lower extremities. Prehospital vitals confirmed septic shock (systolic blood pressure 75-95 mmHg, pulse >150, respiratory rate 21-49, SpO₂ 75-97%). Initial labs: C-reactive protein (CRP) 220 mg/l (ref <5), white blood cell count (WBC) 29.5 × 10⁹/l (ref 3.5-8.8), lactate 3.7 mmol/l, and rhabdomyolysis (creatin kinase 1100 U/l). Blood cultures grew gram-negative rods in one aerobic bottle (day 2), and W. chitiniclastica was identified by MALDI-TOF the same day. The next day, Ignatzschineria ureiclastica was identified from an anaerobic bottle. Two wound swabs grew Staphylococcus aureus. The patient received IV piperacillin/tazobactam (4 g every 8 hours), continued based on clinical response and susceptibility. Due to worsening, ciprofloxacin (500 mg every 12 hours) was added on day 5. Antibiotics were given for 11 days; no further surgery was required.

Patient 2

A 67-year-old man with type II diabetes, peripheral vascular disease, recurrent pressure ulcers, a left below-the-knee amputation, and a recent right metatarsal amputation was admitted to Zealand University Hospital, Nykøbing, in September 2024 for an infected wound on his amputated right foot. He lived in a poorly ventilated environment with irregular wound care and reported seeing a fly larva fall from the wound. On arrival, labs showed CRP 210 mg/l (ref <5) and WBC 174.7 × 10⁹/l (ref 3.5-8.8). Blood cultures grew gram-negative rods in one aerobic bottle on day 2, and Ignatzschineria indica was identified by MALDI-TOF on day 3. Wound swab grew S. aureus. Empirical treatment with benzylpenicillin and cloxacillin was started on days 1-2, changed to piperacillin and cloxacillin on days 2-4 after finding gram-negative rods, and then switched to ciprofloxacin for 6 days based on antibiotic susceptibility testing. Due to infection and initial refusal of further amputation, a wound revision was performed on day 2, followed by a right, below-the-knee amputation on day 10.

Both patients responded well to antibiotic therapy, with resolution of symptoms and gradual wound healing. They were discharged to rehabilitation units for outpatient follow-up at 3 weeks, where both were recovering satisfactorily.

Methods

Blood cultures (two aerobic, one anaerobic bottle) were performed using the Bact/Alert system. Cultures were grown on 5% blood agar, and isolates were identified using MALDI-TOF mass spectrometry (Bruker). MALDI-TOF was performed on a 3-hour culture and subsequently on an overnight culture. Antibiotic susceptibility testing followed EUCAST guidelines; however, no breakpoints exist for either Wohlfartiimonas or Ignatzschineria spp. Zones are reported in the Table 1. Whole-genome sequencing (WGS) was performed on the GridION platform (Oxford Nanopore Technologies) for confirmation of the identification and genome-based resistance gene profiling (Table 1). DNA extraction used PowerBead tubes (Qiagen), purification with AMPure XP beads (Beckman Coulter), and quantification by Qubit dsDNA Broad Range assay (Thermo Fisher Scientific). Libraries were prepared with the SQK-RBK114.24 kit. The fly species in Patient 1 was identified by Professor Thomas Pape of The Natural History Museum, Copenhagen, using photos from prehospital staff. The larvae belonged to Calliphora or Lucilia, both common blow flies whose larvae are known to carry Ignatzschineria and Wohlfahrtiimonas [1,4]. It was believed to be Lucilia, as a few Lucilia flies were seen in one of the photos.

Table 1.

Phenotypic resistance and resistance genes detected in the 3 isolates from patients 1 and 2.

Antibiotic	Isolate 1		Isolate 2		Isolate 3
	Patient no. 1		Patient no. 1		Patient no. 2
	Wohlfahrtiimonas chitiniclastica		Ignatzschineria ureiclastica		Ignatzschineria indica
	Eucast zone, mm	Wgs resistance gene detected	Eucast zone, mm	Wgs resistance gene detected	Eucast zone, mm	Wgs resistance gene detected
Ampicillin	19	-	28	-	30	-
Piperacillin/tazobactam	34	-	26	-	15	-
Gentamicin	20	APH(6)-Id, APH(3′)-Ib, APH(3′)-1a, AAC(6)-Ib4	24	-	17	APH(6)-Id, APH(3′)-Ib, AadA14
Ciprofloxacin	34	-	34	-	29	-
Cefpodoxim	33	-	31	-	22	-
Amoxicillin/clavulanic acid	28	-	29	-	30	-
Mecillinam	24	-	18	-	16	-
Meropenem	41	OXA-1	34	-	30	-
Ceftazidim	30	-	6	-	15	-
Tobramycin	13	APH(6)-Id, APH(3)-Ib, AAC(6)-Ib4	nd	-	12	APH(6)-Id, APH(3)-Ib, AadA14
Sulfamethoxazole/trimetoprim	nd	Sul2, dfrA1	nd	-	10	Sul2, Dfrl
Tetracycline	nd	Tet(H), msrE	nd	-	nd	Tet(H)
Macrolide	nd	mphE	nd	-	nd	-
Lincosamide	nd	-	nd	-	nd	lnuG

nd: not determined; Wgs: whole genome sequencing.

Discussion

This is the first report of bacteremia caused by Ignatzschineria species and W. chitiniclastica in Scandinavia. Both patients had significant risk factors, including chronic wounds, poor hygiene, and comorbidities, consistent with previously reported cases [5,6].

W. chitiniclastica and Ignatzschineria spp. are emerging pathogens in wound myiasis, particularly in patients with compromised skin integrity [1,6]. Infections can range from localized wound infections to severe sepsis and, in rare cases, endocarditis or osteomyelitis [7,8]. Previously, these bacteria were thought to be transmitted mainly by the flesh fly Wohlfahrtia magnifica, which is a species that does not occur in Scandinavia. However, W. chitiniclastica and Ignatzschineria spp. are also gut bacteria of blowflies of the genera Calliphora (blue bottle flies) and Lucilia (green bottle flies), which can cause myiasis in temperate regions. Cases of myiasis with W. chitiniclastica have been reported in Estonia, as well as the United Kingdom, France, Spain, Hungary, Turkey, Egypt, Iran, Korea, the United States of America, and South America [5,6,[9], [10], [11], [12]]. For species of Ignatzschineria, human cases have been documented in Slovenia, Canada, France, and other European countries [2,[10], [11], [12], [13]]

In both cases, prompt identification of the pathogens allowed for targeted antibiotics and surgical management. Advanced diagnostic tools, such as MALDI-TOF MS and WGS, are essential for accurate identification of these organisms [6]. Both W. chitiniclastica and Ignatzschineria spp. generally show broad susceptibility to antibiotics, with varying resistance patterns, necessitating susceptibility testing to guide therapy [6,8,14]). Ignatzschineria spp. demonstrate susceptibility to aminoglycosides (amikacin, gentamicin), fluoroquinolones (ciprofloxacin), and β-lactams, but carbapenem resistance has been reported in specific cases [7,8,14]. W. chitiniclastica have previously been treated with β-lactams (e.g., ceftazidime, ceftriaxone), fluoroquinolones (levofloxacin), or trimethoprim/sulfamethoxazole, though intrinsic resistance to fosfomycin and emerging resistance to aminoglycosides is noted in some strains [2]. In our isolates, we found an OXA-1 gene, a class D β-lactamse gene, in the W. chitiniclastica, which is unusual, but phenotypic testing showed a large zone for meropenem. The Ignatzschineria indica had a small zone for piperacillin/tazobactam, indicating resistance, which is why therapy was changed to ciprofloxacin.

Both patients responded well to treatment. These cases highlight the need to include these rare bacteria in sepsis differentials for patients with myiasis or chronically infested wounds. Further research is needed to better understand the epidemiology, pathogenesis, and optimal treatment strategies for these rare infections.

Conclusion

We present the first Scandinavian cases of bacteremia caused by Ignatzschineria species and W. chitiniclastica linked to fly larvae-infested wounds. These cases emphasize the importance of considering these emerging pathogens in myiasis-associated sepsis and the need for accurate diagnostics and targeted antibiotic therapy.

Declaration of competing interest

The authors have no competing interests to declare.