A 75-year-old man with chronic periodontitis, hyperuricemia, and benign prostatic hyperplasia with a 4-week history of pain in his left thigh was admitted to the hospital. Six days prior to admission, he had fallen on the street and was admitted to a different hospital. He had a left femoral diaphyseal fracture, for which direct traction was performed. However, chest computed tomography (CT) showed a nodular shadow in the left upper lobe, and he was transferred to our cancer center because of possible bone metastasis of lung cancer. He had no smoking history or any other lung disease.
On examination, he appeared to be slightly ill. His body temperature was 36.8 °C, heart rate was regular at 91 bpm, blood pressure was 113/82 mmHg, respiratory rate was 20 bpm, and oxygen saturation was 96% in room air. Intraoral examination revealed poor oral hygiene and an impacted upper left third molar, indicating an 11 mm periodontal pocket, with plaque and bleeding. The patient’s left thigh was inflamed; however, his physical examination was otherwise unremarkable. Laboratory investigations revealed a white blood cell count of 13,040 cells/µL (normal: 3300–8600 cells/µL), neutrophil count of 12,062 cells/µL, eosinophil count of 652 cells/µL, hemoglobin level of 11.4 g/dL (normal: 13.7–16.8 g/dL), mean corpuscular volume of 89.9 fL (normal: 83.6–98.2 fL), hemoglobin A1c of 5.7% (normal: 4.9–6.0 g/dL), elevated serum levels of C-reactive protein at 26.7 mg/dL (normal: < 0.30 mg/dL), and alkaline phosphatase level of 308 U/L (normal 115–359 U/L). Human immunodeficiency virus (HIV)-1 and HIV-2 antibody tests came out negative. Analysis of the tumor markers showed 1.8 ng/mL carcinoembryonic antigen (normal: <5.0 ng/mL), 0.6 ng/mL squamous cell carcinoma (normal: < 1.5 ng/mL), 1.0 ng/mL cytokeratin fraction (normal: < 3.5 ng/mL), and 65.9 pg/mL progastrin-releasing peptide (normal: < 81.0 pg/mL). Chest radiography showed no abnormal findings, but chest CT showed a nodular shadow with pleural indentation in the left upper lobe (Fig. 1a). An X-ray (Fig. 1b) and CT (Fig. 1c) of the lower extremities showed a fracture of the left femur with heterogeneous osteolytic changes of the bone cortex. Panoramic images of the teeth showed a third molar on the left maxilla, with a slightly defined radiolucent area around the crown (Fig. 1d). Periradicular radiolucency of the left lateral incisor and canine of the maxilla and of the right first molar and left incisors of the mandible was observed.
On the second day of admission (day 2), surgery was performed after a single dose of cefazolin (1 g) was administered as a perioperative prophylactic antimicrobial therapy. A substantial amount of abscess, hematoma, and necrotic tissue was detected within the vastus lateralis muscle and at the fracture site. Based on these findings, a pathological fracture due to osteomyelitis was strongly suspected. The left femur was debrided and irrigated, and left femoral intramedullary nail fixation was performed. The abscess revealed the presence of numerous white blood cells, gram-negative rods, and gram-positive cocci (Fig. 2a). A bone biopsy showed inflammation but no signs of malignancy.
Postoperatively, two sets of blood cultures were obtained in BACT/ALERT FA/FN PLUS culture bottles of the BacT/ALERT 3D system (Sysmex bioMérieux, Tokyo, Japan). After collecting the blood cultures, 3 g of sulbactam-ampicillin (SBT/ABPC) was administered every 6 h. The abscesses were cultured on a Sheep Blood Agar plate (Nissui Pharmaceuticals Co., Ltd., Tokyo), a chocolate agar EX II plate (Nissui Pharmaceutical Co., Ltd.), a MacConkey II agar plate (Becton Dickinson Co., Ltd., Tokyo), a Brucella HK (RS) agar plate (Kyokuto Pharmaceutical Co., Tokyo, Japan), a CHROMagar MRSA plate (Kanto Chemical Co, Inc., Tokyo, Japan), and a CHROMagar Candida plate (Becton Dickinson, Co, Inc., Tokyo, Japan). After 24 h of anaerobic incubation of the abscess specimens at 35 °C, small colonies of gram-positive cocci were observed on Brucella HK agar, and at 48 h, two types of small colonies of gram-negative rods were formed on the Brucella HK agar medium. The cultures in abscess specimens were identified as Parvimonas micra and Fusobacterium nucleatum using VITEK2 ver. 9.02 with VITEK 2 ANC ID card (SYSMEX bioMérieux Co., Ltd., Tokyo, Japan) with 97% and 99% probability, respectively. Because another form of gram-negative rod colony from the abscess specimen was not identified by VITEK2, it was evaluated using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) using the Vitek MS ver. 4.7.1 (bioMérieux, Tokyo, Japan), which demonstrated Campylobacter rectus with a 99.9% confidence value. The cultures of abscess specimen were negative for mycobacteria. For blood cultures at 95 h and 22 min of incubation, two FN bottles in the system showed a positive signal for bacterial growth, demonstrating gram-negative rods and gram-positive cocci (Fig. 2b). The positive bottles were subcultured on Sheep Blood Agar plate, MacConkey II agar plate, and Brucella HK (RS) agar plate. After 24 h of anaerobic incubation at 35 °C, small colonies of gram-positive cocci were observed on Brucella HK agar plate, and at 48 h, small gram-negative rods (Fig. 3) were formed on Brucella HK agar medium. Using the blood cultures, P. micra was identified by VITEK2 with 99% probability, and C. rectus was identified using Vitek MS ver. 4.7.1, with a 99.9% confidence value.
16 S ribosomal RNA (16 S rRNA) sequencing was performed on strains identified as C. rectus from abscesses. Based on a Basic Local Alignment Search Tool (BLAST) search of the sequence on the 16 S rRNA gene of the isolated strain, the homology with the standard strain C. rectus canine oral taxon 010 clone OB004 (GenBank Accession No.: JN713167.1) was 99.02% (1610/1626 bp). Blood cultures and abscesses of C. rectus and F. nucleatum were poorly developed, making it difficult to perform antimicrobial susceptibility testing. According to the methodology recommended by the Clinical and Laboratory Standards Institute (CLSI), document M100-S25 (2015) minimal inhibitory concentration (MIC) breakpoints for the Bacteroides fragilis group, the MIC of antimicrobial agents determined by broth microdilution for P. micra isolates from blood cultures and abscess specimens were as follows: penicillin G, ≤ 0.06 mg/L; ampicillin, ≤ 0.13 mg/L; clindamycin, 0.25 mg/L; cefmetazole, ≤ 16.0 mg/L; and meropenem, ≤ 0.25 mg/L. Sputum culture showed the presence of only alpha-hemolytic streptococci, Neisseria spp., and Haemophilus spp. Three series of sputum samples for mycobacterium were negative. Transthoracic echocardiography showed no obvious vegetation. The final diagnosis was pathological fracture and hematogenous osteomyelitis due to P. micra, F. nucleatum, and C. rectus caused by periodontitis.
Postoperatively, the patient was provided dental care and chronic periodontitis examination by a dentist. The pain in his left thigh gradually reduced, and he was able to walk with a cane. SBT/ABPC was administered for 27 days and subsequently changed to oral amoxicillin clavulanic acid (1500 mg/day) on day 29. The patient was discharged on day 33. Because of the residual intramedullary nail, antimicrobial agents were prescribed for long-term suppressive therapy. The left lung nodule was suspected to be a primary lung cancer, and we plan to investigate it at our hospital.