2023 Volume 72 Issue 3 Pages 452-457
A woman in her 50s was undergoing chemotherapy for breast cancer and bone metastasis. She had been admitted to our hospital with a diagnosis of obstructive jaundice since she had abdominal pain for one month. Blood culture was performed for a detailed examination of fever after biliary stent placement by endoscopic retrograde cholangiopancreatography (ERCP). Gram-negative bacilli were observed in blood cultures after 18 h of culture. It was determined to be Pseudomonas aeruginosa or Pseudomonas putida by VITEK2. As an additional test, the acyl amidase test was conducted and growth at 42°C was confirmed, but the results did not match those of either P. aeruginosa or P. putida, and thus the cells were not identifiable. In the drug susceptibility test, the strain was susceptible to both imipenem and meropenem, but resistant to doripenem. The strain was also found to be a carbapenemase-producing strain, as shown by the results of the modified carbapenem inactivation method. On the basis of these results, Pseudomonas otitidis was suspected. It was finally identified as P. otitidis, which is characterized by the presence of chromosomal metallo-β-lactamase determined using MALDI Biotyper. P. otitidis can only be identified using 16S rRNA gene sequence analysis and MALDI Biotyper. If we understand the pattern of drug susceptibility test results and the key biochemical characteristics of similar bacteria, we should be able to presume P. otitidis. We believe that this will lead to appropriate antimicrobial treatment and correct nosocomial infection control.
