We report Wohlfahrtiimonas chitiniclastica bacteremia in a 75-year-old man in Japan who had squamous cell carcinoma on his shoulder. In September 2016, an unidentified patient was found unconscious on the ground by a passerby and admitted to the emergency department of the National Center for Global Health and Medicine (Tokyo, Japan). He had a necrotic lesion on his left shoulder with maggots. Blood analysis showed leukocytosis (26.61 × 10⁹ cells/L [reference range 3.30–8.60 × 10⁹ cells /L]), thrombocytosis (626 × 10⁹/L [reference range 158–348 × 10⁹/L]), anemia (hemoglobin, 9.6 g/dL [reference range 13.7–6.8 g/dL]), and elevated C-reactive protein (87.9 mg/L [reference range 0.00–1.40 mg/L]). Albumin was 2.4 g/dL (reference range 4.1–5.1 g/dL) and calcium was 12.6 mg/dL (reference range 8.8–10.1 mg/dL). He was diagnosed with disturbance of consciousness caused by hypercalcemia and was hospitalized.

After saline infusion and intravenous cefazolin (3 g/d) were initiated, the patient’s condition improved. A blood culture taken at the time of admission grew Peptoniphilus harei. A swab culture of the ulcer site grew Proteus mirabilis, Morganella morganii, and Kerstersia gyiorum. A biopsy was performed on day 3, and the patient was diagnosed with squamous cell carcinoma. Enhanced computed tomography scanning revealed an ulcer and ring-enhancing lesion on his left shoulder (which was suspected of being a tumor or abscess) and multiple enlarged lymph nodes and 10-mm pulmonary nodules in the right lung.

On day 20, the patient had fever and disturbance of consciousness; therefore, he was transferred to the Infectious Disease department of the hospital. Intravenous therapy with vancomycin (1.5 g/d), cefepime (3 g/d), and metronidazole (1,500 mg/d) was initiated, and the patient’s fever and consciousness improved. Two cultures of blood taken on day 20 grew P. mirabilis, M. morganii, Streptococcus anginosus, Streptococcus agalactiae, Bacteroides fragilis, and gram-negative rods. After we obtained the culture results, vancomycin was stopped in accordance with the susceptibility test results. We identified the gram-negative rods as W. chitiniclastica by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (Bruker Daltonics, Billerica, MA, USA), which showed scores of 2.239. We further confirmed the isolate to be W. chitiniclastica by using 16S rRNA sequencing; the isolate was 99.08% identical to strain S5 (GenBank accession no. AM397063). We assessed the isolate’s antimicrobial susceptibility profile (Table). The patient improved and was later discharged to another hospital.

W. chitiniclastica is a gram-negative, short, facultative anaerobic, straight-rod gammaproteobacterium that was first isolated from the parasitic fly Wohlfahrtia magnifica (1). This fly has not been reported in Japan. However, W. chitiniclastica has also been isolated from the Chrysomya megacephala fly, and this species has been reported in Japan (2), and from from the Musca domestica housefly, which is widely distributed all over the world (3). Campisi et al. reported that the Lucilia sericata fly might be a vector for W. chitiniclastica (4); this fly is common and widely distributed throughout Japan, and a case of cutaneous myiasis on skin cancer was reported (5). Unfortunately, we could not collect maggots from this patient because they were rapidly discarded at the emergency department.

Worldwide, few human cases of W. chitiniclastica infection have been documented. W. chitiniclastica has been described as a zoonotic pathogen (6) and reported from Hungary, Egypt, Niger, Germany, India, France, China, Argentina, Estonia, the United Kingdom, and the United States (4,7,8). Rebaudet et al. (9) described the first human case of bacteremia attributable to W. chitiniclastica, which occurred in a 60-year-old homeless woman from southeastern France who had a history of alcoholism. Other human cases of W. chitiniclastica bacteremia were reported from Argentina (10) and the United Kingdom (4). Recently, a bacteremia case in a 72-year-old man was reported from Hawaii, USA (1).

Risk factors for W. chitiniclastica infection are poor personal hygiene, alcoholism, peripheral vascular disease, and chronic open wound (8). The patient we describe had a chronic wound because of squamous cell carcinoma, and the associated maggots were thought to be the transmission route. At admission, blood and swab cultures grew polymicrobial isolates without W. chitiniclastica, as confirmed by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. However, a blood culture on day 20 was positive for W. chitiniclastica. The patient probably was infected with W. chitiniclastica during hospitalization. Cases of W. chitiniclastica infection (with or without bacteremia) were reported as parts of polymicrobial infections (1,4,7,8). W. chitiniclastica might have first infected this patient’s ring-enhancing lesion as part of a polymicrobial infection. Because W. chitiniclastica was undetected in blood and swab cultures at admission, the organism might have entered the bloodstream during hospitalization.

This patient improved after intravenous therapy with cefepime and metronidazole. Previously reported W. chitiniclastica bacteremia cases were treated with combination antimicrobial therapies, including cefuroxime plus metronidazole plus clarithromycin (4), ceftazidime plus amikacin (10), piperacillin/tazobactam plus clindamycin plus vancomycin (1), ceftriaxone monotherapy (9), and meropenem monotherapy (1). Two of the 5 cases were fatal (1,10).

Clinicians should be attentive to the possibility of W. chitiniclastica infection in patients who have chronic wounds with maggots and poor hygiene. Clinical suspicion is warranted even if blood and swab cultures are initially negative for W. chitiniclastica.

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