title: Ruptured aortic aneurysm due to Mycobacterium bovis BCG with a delayed bacteriological diagnosis due to false negative result of the MPB 64 immunochromatographic assay.
abstract: BACKGROUND
  Adjuvant therapy with bacillus Calmette-Guerin (BCG), a live attenuated strain of Mycobacterium bovis, has become the treatment of choice for low-risk superficial bladder carcinoma following transurethral resection of the bladder. Complications following vesical BCG instillations are uncommon but, in some cases, severe side-effects can occur such as sepsis or mycotic aneurysm. Besides usual laboratory techniques used for the diagnosis of Mycobacterium tuberculosis complex (MTBC) infections (smear microscopy and cultures), commercial immunochromatographic assays detecting MBP64, a 24 kDa M. tuberculosis complex-specific secretory protein, can rapidly distinguish MTBC and non-tuberculosis mycobacteria (NTM). MPB64 is found in M. tuberculosis, M. bovis and some but not all substrains of M.bovis BCG. Therefore, these immunochromatographic tests can lead to false negative results and delayed bacteriological diagnosis depending on the presence or absence of MPB64 protein in BCG substrains used for intravesical therapy.
  
  
  METHODS
  We report the case of a 78-year-old male patient who was admitted to the hospital because of a 1-month history of unexplained fever, thrill, weight-loss and general malaise. His past medical history was marked by a non-muscle-invasive bladder carcinoma treated by transurethral resection followed by BCG instillations (Oncotice, Merck, USA). The patient was initially treated for a urinary tract infection but as fever persists after 72 h of antibiotherapy, urinary tract ultrasound was performed and revealed a large abdominal aortic aneurysm confirmed by computed tomography. Surgery was performed after multidisciplinary discussion. Direct smear of perioperative samples revealed acid-fast bacilli and both solid and liquid cultures were massively positive. Rapid identification of the positive mycobacterial culture was performed using an immunochromatographic assay based on the detection of the Mycobacterium tuberculosis MPB 64 antigen. The result was negative for Mycobacterium tuberculosis complex. After review of the medical record, a polymerase chain reaction (PCR) was performed and gave a positive result for M. tuberculosis complex. Anti-tuberculosis therapy was started immediately and the patient evolved favorably.
  
  
  CONCLUSIONS
  Through this case, we showed how the utilisation of MPB64 immunochromatographic assays can provide misleading information due to the variable presence of this protein among the different BCG strains. This case further illustrates the utility of rapid TB complex-specific PCR assays which provide a more reliable identification of all MTBC species.
authors.affiliation: Microbiology Unit, Laboratory Department, Cliniques Universitaires Saint-Luc, Brussels, Belgium. simar.joanna@gmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Simar
authors.affiliation: Infectious Diseases Unit, Department of Internal Medicine, Cliniques Universitaires Saint Luc, Brussels, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Belkhir
authors.affiliation: Urology Unit, Department of Surgery, Cliniques Universitaires Saint Luc, Brussels, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Tombal
authors.affiliation: Microbiology Unit, Laboratory Department, Cliniques Universitaires Saint-Luc, Brussels, Belgium.|Pôle de Microbiologie Médicale, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: André
mesh_terms: D000368:Aged; D001014:Aortic Aneurysm / Q000000981:diagnostic imaging / Q000382:microbiology*; D001019:Aortic Rupture / Q000000981:diagnostic imaging / Q000382:microbiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D002846:Chromatography, Affinity / Q000379:methods*; D005188:False Negative Reactions; D006801:Humans; D008297:Male; D009163:Mycobacterium bovis / Q000502:physiology*; D014057:Tomography, X-Ray Computed
chemical_list: D001426:Bacterial Proteins
keywords: BCG therapy; Case report; MPB64 immunchromatographic assays; Mycobacterium tuberculosis complex infections