tularemia is a potentially fatal , multisystemic disease in humans , and it is caused by francisella tularensis and is primarily observed in the northern hemisphere including europe , north america , and asia . pneumonic tularemia occurs after exposure to aerosolized f tularensis particles or from hematogenous spread from a distal site ; it has remained the most lethal form of tularemia.f tularensis has two predominant subspecies , namely subsp tularensis ( type a ) and subsp holarctica ( type b ) . type b is much less virulent compared with type a and almost never causes lethal infection in humans . tularemia pneumonia was a more invasive form of infection and more likely to be caused by f tularensis type a previously . in this report , we present a 68-year - old man californian resident with tularemic bacteremic pneumonia caused by type b tularemia following treatment for 5 months with steroids for hypersensitivity pneumonitis . this case suggests that low virulence f tularensis should be included in the differential diagnoses of bacteremic pneumonia in immune - compromised hosts , particularly for those with endemic tularemia . in june , a 68-year - old man with a 3-day history of high fever was admitted to our hospital . the patient lived in a californian metropolitan area for the past few decades and arrived in taiwan 1 day before admission . he had been diagnosed with diabetes ; dry cough , and progressive shortness of breath were observed for 6 months . hypersensitivity pneumonitis was diagnosed after extensive studies involving high - resolution chest computed tomography ( ct ) and lung biopsy in addition to the exclusion of toxoplasma , rubella , cytomegalovirus , and herpes simplex virus type 1 and 2 . thereafter , a high dose of steroids with prednisolone 60  mg per day was prescribed for 5 months . , laboratory examinations revealed leukocytosis and considerably elevated c - reactive protein levels ( 260.1  mg a chest radiograph revealed left lower lung opacities ( figure 1 ) . despite the administration of empiric therapy with ceftriaxone plus clindamycin for community - acquired pneumonia , the fever persisted , and admission chest radiograph : left lower lung consolidation and pleural effusion . initial chest computed tomography ( ct ) : left lower lung air - bronchial ground with pleural effusion . a blood culture was performed in 2 sets , and both sets were positive for gram - negative bacilli after 1 day . a polymerase chain reaction ( pcr ) analysis for the 16s rrna showed the presence of f tularensis on detection of the lpna encoding a 17-kda lipoprotein which is specific for strains of the genus francisella . using the primer of 5-aggcggagatctaggaa - ccttt-3 and 5-agcccaagctgactaaaatcttt-3 , holarctica was confirmed by the amplification of ft - m19 , which is located between the genes dead and ppic , showing the specific 30-bp deletion ( figure 3 ) . the serology test for tularemia by the capture enzyme - linked immunosorbent assay , which was based on antigen binding to a monoclonal antibody ( mab ) coated onto a solid phase ( microtitre plate ) and detection of the bound antigen using the same mab ( peroxidase labeled ) , had been prescribed but were negative result at that time . sputum , bronchial washing , and pleural effusion cultures were negative for bacteria , fungi , and tuberculosis . in addition , tests for mycoplasma , legionella , and human immunodeficiency virus were negative . streptomycin ( 1  g every 12  h ) and doxycycline ( 100  mg every 12  h ) were administered for severe tularemia with bacteremic pneumonitis . the fever subsided after 1 day , and parenchymal changes in the lung improved steadily thereafter . although no pathogen was isolated from the lung or associated specimen , the clinical course of concomitant bacteremia and fulminant pneumonia suggested that they were caused by the same pathogen of f tularensis . the fever , pneumonia , and pleural effusion were progressive at first even under coverage with extended - spectrum antibiotics . subspecies identification with ft - m19 assay , the pcr product has a band over 220  bp area . assessment of risk exposures regarding this case revealed no history of hunting , skinning , farming , lawn mowing , brush cutting , or contaminated food ( such as hares ) consumption . the patient is a biochemist who oversees his own biochemistry company , which manufactures products from the ascites of mice and the serum of rabbits . during the past 6 years , he was in frequent contact with the secretion of the animals ( either ascites or serum ) during routine laboratory procedures . tularemia is a zoonotic infection primarily observed in the northern hemisphere , and it is caused by f tularensis , a strictly aerobic , gram - negative coccobacillus . it is associated with rodents and hares and is transmitted to humans by direct contact with animals , aerogenic exposure , contaminated food or water consumption , and arthropod bites . laboratory - acquired tularemia has been frequently reported , and it remains a threat for laboratory personnel . the most common ( 80% of cases ) clinical manifestation of tularemia is ulceroglandular tularemia . pneumonia occurs in approximately 30% of patients with ulceroglandular tularemia and 80% of those with typhoidal tularemia ( prevalence varies widely between clinical series ) . f tularensis has two predominant subspecies : subsp tularensis ( type a ) and subsp . type a is predominantly isolated in north america , highly virulent , and can cause invasive diseases such as pneumonia and bacteremia . before the advent of effective antibiotics , type b spreads more widely over the northern hemisphere , and it is the predominant subspecies in europe , japan , and north america . type b is much less virulent compared with type a. it is rarely invasive and almost never causes lethal infection in humans , even when early appropriate treatment is not applied . primary pneumonia is associated with pulmonary involvement because of inhalation , whereas secondary pneumonia is considered to be caused by hematogenic spread during the course of the disease . bacteremic tularemia is rare , and most cases were due to type a. by contrast , pulmonary involvement with type b infection has been of much lower incidence , even in outbreaks or epidemics . type b tularemia with bacteremia was reported only in immune - compromised hosts , including those with acquired immune deficiency syndrome , and in patients who have undergone liver transplantation . serology is the most frequently ordered diagnostic test for f tularensis infection ; however , it is limited by poor sensitivity because of undetectable antibody levels until the second week of illness . blood cultures remain useful for an early diagnosis of severe forms of tularemia , whereas serological tests are not yet positive . molecular subtyping assays are directed against an upstream region of an ribonucleic acid ( ribonucleic acid ) helicase ( the ft - m19 assay ) , the presence or absence of the isftu2 insertion sequence element ( isftu2 assay ) , the f tularensis region of difference 1 ( rd1 assay ) , and the pdpd gene ( pdpd-2 assay ) . we report an immune - compromised patient who presented with severe bacteremic tularemic pneumonia caused by low virulence f tularensis ( type b ) and was administered high doses of steroids . this case suggests that low virulence f tularensis should be included in the differential diagnoses of bacteremic pneumonia for endemic tularemia . real - time pcr can facilitate the early diagnosis of tularemia , particularly in patients with less frequent clinical manifestations and those from endemic regions .
abstracttularemia is a zoonotic infection seen primarily in the northern hemisphere . 
 it is caused by the bacteria francisella tularensis . although the ulceroglandular form of the disease is the more common manifestation of infection , f tularensis is known to cause pneumonia . f tularensis has two predominant subspecies , namely subsp . 
 tularensis ( type a ) and subsp . 
 holarctica ( type b ) . 
 type b tularemia is considered to be much less virulent than type a and barely caused lethal disease and pneumonia.we reported a case with a 68-year - old man immune - compromised patient diagnosed with bacteremic pneumonia engendered by type b tularemia with initial presentation of high fever , pneumonia with pleural effusion ; the diagnosis was performed using 16s rrna gene sequence analysis . 
 the patient 's fever , pneumonia , and pleural effusion were resolved with appropriate antibiotics for tularemia . 
 this case involving severe bacteremic pneumonia in an immune - compromised patient is rare.this case suggests that low virulence f tularensis should be included in the differential diagnoses of bacteremic pneumonia for endemic tularemia .