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Jun Hirai,1,2 Nobuaki Mori,1,2 Daisuke Sakanashi,2 Yuichi Shibata,2 Nobuhiro Asai,1,2 Mao Hagihara,3 Hiroshige Mikamo1,2 1Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Nagakute, Aichi, Japan; 2Department of Infection Control and Prevention, Aichi Medical University Hospital, Nagakute, Aichi, Japan; 3Department of Molecular Epidemiology and Biomedical Sciences, Aichi Medical University, Nagakute, Aichi, JapanCorrespondence: Jun Hirai, Department of Clinical Infectious Diseases, Aichi Medical University Hospital, 1-1, Yazako-karimata, Nagakute, Aichi, 480-1195, Japan, Tel +81-561-62-3311, Fax +81-561-76-2673, Email hiraichimed@gmail.comAbstract: Stenotrophomonas maltophilia (S. maltophilia) is increasingly recognized as a pathogen responsible for nosocomial infections, particularly in immunocompromised patients. The most common types of S. maltophilia infections are pneumonia and catheter-related bloodstream infection, and clinical cases of intra-abdominal abscesses due to S. maltophilia are rare. We present a rare case of intra-abdominal abscess and bacteremia as a surgical site infection (SSI) caused by S. maltophilia in a patient following total gastrectomy. We also reviewed previous literature to elucidate the clinical characteristics of intra-abdominal abscess due to S. maltophilia. The patient, a 75-year-old man with diabetes and polymyositis (treated with prednisolone), developed a fever 17 days after undergoing a total gastrectomy for gastric cancer. Abdominal computed tomography revealed a hypodense solid mass at the esophagojejunostomy site, which appeared to be an intra-abdominal abscess. The culture of both blood and drained abscess pus confirmed only S. maltophilia. Treatment with intravenous trimethoprim-sulfamethoxazole and abscess drainage led to complete resolution. The patient recovered and was discharged and did not experience a recurrence. We reviewed the English literature and found only two additional case reports of intra-abdominal abscesses caused by S. maltophilia. As in our case, the intra-abdominal abscess occurred after abdominal surgery and the source was suspected to be deep SSI. This case highlights the importance of considering S. maltophilia as a potential pathogen in patients with atypical post-surgical abdominal infections. Physicians should be aware that S. maltophilia has the potential to cause intra-abdominal abscesses secondary to SSI, in addition to Enterobacteriaceae, a major causative pathogen of SSI. Further studies are required to elucidate the etiology, epidemiology, and risk factors for SSI caused by S. maltophilia.Keywords: Stenotrophomonas maltophilia, abdominal abscess, surgical site infection

Jun Sada,1 Jun Hirai,2,3 Koki Ota,1 Shingo Numoto,1 Hitoshi Honma,1 Nobuaki Mori,2,3 Daisuke Sakanashi,3 Hiroshige Mikamo,2,3 Akihisa Okumura1 1Department of Pediatrics, Aichi Medical University Hospital, Nagakute, Aichi, Japan; 2Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Nagakute, Aichi, Japan; 3Department of Infection Control and Prevention, Aichi Medical University Hospital, Nagakute, Aichi, JapanCorrespondence: Jun Sada, Department of Pediatrics, Aichi Medical University Hospital, 1-1, Yazako-karimata, Nagakute, Aichi, 480-1195, Japan, Tel +81-561-62-3311, Fax +81-561-76-2673, Email sada.jun.043@mail.aichi-med-u.ac.jpAbstract: Kalamiella piersonii is rare pathogen, and its pathogenicity to humans has been unknown. We describe an infant with bacteremia caused by Kalamiella piersonii. The patient was a 2-month-old girl presented with diarrhea, poor oral intake, and vomiting. The patient was tentatively diagnosed with acute enterocolitis. After admission, the patient developed a fever and blood culture yielded Gram-negative cocci, first determined to be Pantoea septica by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. However, genetic analysis of 16S rRNA allowed its identification as Kalamiella piersonii (GenBank accession number is OQ547240). Other housekeeping genes such as gyrB, rpoB, and atpD also identified the isolated strain as Kalamiella piersonii. The patient was successfully treated with cefotaxime without sequelae. Later, the patient was diagnosed as non-IgE-mediated gastrointestinal food allergy. Our experience indicated that Kalamiella piersonii is a potential human pathogen that can cause invasive infections even in infants and children. Identification of Kalamiella piersonii is difficult with routine conventional tests, and detailed studies including genetic analyses are necessary to clarify the pathogenicity of Kalamiella piersonii in humans.Keywords: Kalamiella piersonii, 16S rRNA, non-IgE-mediated gastrointestinal food allergy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Jun Hirai,1,2 Hiroyuki Suzuki,3 Daisuke Sakanashi,2 Yuji Kuge,4 Takaaki Kishino,4 Nobuhiro Asai,1,2 Mao Hagihara,5 Hiroshige Mikamo1,2 1Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Nagakute, Aichi, Japan; 2Department of Infection Control and Prevention, Aichi Medical University Hospital, Nagakute, Aichi, Japan; 3Department of Neurology, Aichi Medical University, Nagakute, Aichi, Japan; 4Department of Emergency and Critical Care Medicine, Aichi Medical University Hospital, Nagakute, Aichi, Japan; 5Department of Molecular Epidemiology and Biomedical Sciences, Aichi Medical University, Nagakute, Aichi, JapanCorrespondence: Jun Hirai, Department of Clinical Infectious Diseases, Aichi Medical University Hospital, 1-1, Yazako-karimata, Nagakute, Aichi, 480-1195, Japan, Tel +81-561-62-3311, Fax +81-561-76-2673, Email hiraichimed@gmail.comAbstract: Staphylococcus argenteus is a new species classified as part of the Staphylococcus aureus-related complex in 2015 and has been recognized to be as pathogenic as S. aureus. We describe the first case of endocarditis caused by S. argenteus. A 51-year-old man presented with chief complaints of fever and headaches. On admission, he showed a slight decrease in consciousness level (Glasgow Coma Scale, E4V4M6). Careful physical examination and imaging revealed a systolic heart murmur, Janeway lesions, and complicating convexity subarachnoid hemorrhage (cSAH) of the left frontal lobe. Ceftriaxone 4 g/day was administered immediately after blood cultures were obtained. The next day, all blood cultures grew Gram-positive cocci, identified as Staphylococcus aureus or Staphylococcus argenteus by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). However, the version of MALDI-TOF MS used could not distinguish these bacteria. Although we could not find valvular vegetation, he was clinically diagnosed with infective endocarditis according to the modified Duke’s criteria. Meropenem 6 g/day and linezolid 1.2 g/day were started to cover S. aureus and methicillin-resistant S. aureus. Finally, ampicillin was selected based on drug susceptibility, and the patient was treated for 8 weeks and recovered without permanent damage. The isolated strain formed white colonies on blood agar plates, characteristic of S. argenteus, and differs from golden colony-forming S. aureus. Genetic analysis revealed the isolated strain as S. argenteus (sequence type 1223). Although distinguishing S. argenteus from S. aureus using routine conventional laboratory tests is difficult, the updated library version of MALDI-TOF MS is useful in identifying S. argenteus. Interestingly, all published cases of infection caused by ST1223 have been reported in Japan. Therefore, the trend of infections from the ST1223 strain should be carefully monitored, particularly in Japan. Further investigation is needed to clarify the epidemiology and clinical characteristics of S. argenteus infection, as there are few studies regarding this pathogen.Keywords: Staphylococcus argenteus, sequence type 1223, infective endocarditis, convexity subarachnoid hemorrhage, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Japan

Jun Hirai,1,2 Tessei Kuruma,3 Daisuke Sakanashi,2 Yuji Kuge,4 Takaaki Kishino,4 Yuuichi Shibata,5 Nobuhiro Asai,1,2 Mao Hagihara,6 Hiroshige Mikamo1,2 1Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Nagakute, Aichi, 480-1195, Japan; 2Department of Infection Control and Prevention, Aichi Medical University Hospital, Nagakute, Aichi, 480-1195, Japan; 3Department of Otolaryngology, Aichi Medical University Hospital, Nagakute, Aichi, 480-1195, Japan; 4Department of Emergency and Critical Care Medicine, Aichi Medical University Hospital, Nagakute, Aichi, 480-1195, Japan; 5Department of Pharmacy, Aichi Medical University Hospital, Nagakute, Aichi, 480-1195, Japan; 6Department of Molecular Epidemiology and Biomedical Sciences, Aichi Medical University, Nagakute, Aichi, 480-1195, JapanCorrespondence: Jun Hirai, Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Nagakute, Aichi, 480-1195, Japan, Tel +81-561-62-3311, Fax +81-561-76-2673, Email hiraichimed@gmail.comAbstract: Although Dialister pneumosintes is a commensal microorganism of the oral cavity, it may sometimes cause severe systemic infections. We report a case of Lemierre syndrome (LS), which developed after D. pneumosintes infection, in a 73-year-old Japanese woman who was admitted to the hospital for throat pain, neck swelling, and fever for 3 days. She had a 3-month history of neglected dental caries, gingivitis, and periodontitis. Physical examination revealed right tonsillar erythema and swelling, and computed tomography (CT) showed peritonsillar and retropharyngeal abscesses. Ampicillin/sulbactam was promptly administered after collecting two sets of blood cultures. Surgical drainage for peritonsillar and retropharyngeal abscesses was also conducted on the second hospital day. Although only commensal oral microflora grew in the culture from the drained pus, Gram-negative bacilli were confirmed in the anaerobic blood cultures. Metronidazole was administered intravenously; however, the fever and neck swelling persisted. Repeat CT performed on the fifth hospital day revealed right internal jugular vein thrombosis, a known complication of tonsillitis and pharyngitis once the infection extends beyond the oropharynx. We diagnosed she had coexisting LS, and anticoagulant therapy was added to her treatment regimen. Her condition improved, and she was discharged after completing 3 weeks of antibiotics. Conventional methods failed to identify the isolated bacterium, and 16S rRNA sequencing ultimately identified it as D. pneumosintes. In a literature review of bacteremia due to D. pneumosintes, poor oral hygiene was considered a probable risk factor for invasive D. pneumosintes infection. We consider this to be the case in our patient who presented with dental caries, gingivitis, and periodontitis. In addition, all cases revealed that the 16S rRNA gene sequencing is useful for identifying this species. Although the diagnosis of LS by physical examination is difficult, physicians should always consider it as a potential complication of infections in the pharyngeal area.Keywords: Dialister pneumosintes, Lemierre syndrome, tonsillar abscess, retropharyngeal abscess, oral hygiene, anticoagulation

Jun Hirai,1 Daisuke Sakanashi,2 Takeshi Kinjo,1 Shusaku Haranaga,3 Jiro Fujita2 1Department of Infectious, Respiratory and Digestive Medicine, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan; 2Department of Infection Control and Prevention, Aichi Medical University Hospital, Aichi 480-1195, Japan; 3Comprehensive Health Professions Education Center, University of the Ryukyus Hospital, Okinawa 903-0215, JapanCorrespondence: Jun Hirai Email j.eichi419@gmail.comAbstract: Hypervirulent Klebsiella pneumoniae (HV-KP) typically causes pyogenic liver abscess and bacteremia with metastatic infections. Community-acquired pneumonia (CAP) due to HV-KP is uncommon and details of its clinical and microbiological features are limited. We report the first case of CAP due to capsular genotype K2-ST86 HV-KP in Okinawa, Japan and review infections caused by the K2-ST86 strain. A 79-year-old woman presenting with fever and productive cough persisting for the past three days was admitted to hospital. Her vital signs indicated septic shock. Lung examination by auscultation revealed holo-crackle and lobar pneumonia in chest radiography, and Streptococcus pneumoniae was suspected. However, sputum and blood cultures revealed Gram-negative coccus identified as K. pneumoniae. Genetic analysis identified the isolated strain as the K2 serotype harboring rmpA, iutA, entB, and mrkD. Therefore, we identified the isolated strain as hypervirulent. The isolate belonged to ST86 as determined by multilocus sequence typing. The case was not complicated by predisposing factors such as diabetes mellitus and malignancy related to HV-KP infection; thus, this CAP-causing HV-KP strain may differ from the typical HV-KP strain that induces liver abscess. A literature review identified only nine cases with CAP due to HV-KP. In all cases, the disease mainly occurred in older males with diabetes mellitus, which makes the present case unusual, and had high rates of septic shock and death. No case, including ours, was complicated by metastatic infection, suggesting that CAP due to HV-KP poses little distant metastasis risk, even in patients with bloodstream infection. In our review, consistent with our case, K2-ST86 was the most common strain of HV-KP in patients with CAP. Therefore, studies are needed to elucidate the clinical and microbiological features of HV-KP CAP, with a focus on the K2-ST86 strain. Physicians should always consider K. pneumoniae in cases of sepsis CAP with lobar pneumonia.Keywords: hypervirulent Klebsiella pneumoniae, community-acquired pneumonia, serotype K2, sequence type 86, lobar pneumonia, Streptococcus pneumoniae

Jun Hirai,1,2 Daisuke Sakanashi,3 Masashi Momose,1 Tomomi Koga,4 Takeshi Kinjo,2 Shusaku Haranaga,5 Eiji Motonaga,6 Jiro Fujita2 1Department of Internal Medicine, Okinawa Miyako Hospital, Okinawa 906-0012, Japan; 2Department of Infectious, Respiratory and Digestive Medicine, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan; 3Department of Infection Control and Prevention, Aichi Medical University Hospital, Aichi 480-1195, Japan; 4Department of Radiology, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan; 5Comprehensive Health Professions Education Center, University of the Ryukyus Hospital, Okinawa 903-0215, Japan; 6Department of General Medicine, Okinawa Miyako Hospital, Okinawa 906-0012, JapanCorrespondence: Jun Hirai Email j.eichi419@gmail.comAbstract: Hypervirulent Klebsiella pneumoniae (HV-KP) is typically associated with community-acquired liver abscess and bacteremia with metastatic infection; however, primary lung abscess (PLA) caused by HV-KP is rare, with only one such case report to date. A 69-year-old man with a history of diabetes mellitus (DM) was admitted to hospital complaining of slight bloody sputum. Chest imaging showed multiple consolidations with cavities in both lung fields. A culture of bronchoalveolar lavage fluid confirmed the presence of K. pneumoniae. Genetic analyses identified the isolate as serotype K2 and sequence type 375 (K2-ST375), and that it harbored the rmpA gene. The patient was an Asian middle-aged male with DM, all of which are risk factors for HV-KP infection. Although complicating DM and the presence of the rmpA gene are more likely to induce disseminated infection, metastatic infections were not found in this patient. The clinical and microbiological characteristics of our patient were different from those of a previous reported case, although in both cases the patient was from Asia and had DM. Therefore, DM appears to be one of the predisposing factors for HV-KP lung abscesses and physicians should pay attention to emerging HV-KP lung abscess infection, particularly in Asian countries. Previous studies have also revealed that K2-ST375 is one of the major clones causing HV-KP infection, and that it is mainly isolated from patients with liver abscess. Interestingly, including the present case, most of the infectious cases caused by K2-ST375 have been reported from Okinawa Prefecture in Japan. Therefore, the trend of the K2-ST375 strain should be carefully monitored, particularly in Okinawa, Japan. The serotype of HV-KP that causes PLA is still unknown and further study is needed to elucidate the etiology of PLA due to HV-KP and the relationship between the strain K2-ST375 and PLA.Keywords: hypervirulent Klebsiella pneumoniae, primary lung abscess, serotype K2, sequence type 375, Okinawa, Japan