A Case of Catabacter hongkongensis and Alistipes indistinctus Isolated from Blood Cultures of a Patient with Acute Appendicitis

Catabacter hongkongensis is an anaerobic gram-positive coccobacillus that was first isolated in Hong Kong. It is infectious and causes high mortality in patients with rare but underlying diseases. Alistipes indistinctus is an anaerobic gram-negative coccobacillus. This bacterium is a common member of the human intestinal microbiota. We report a case of C. hongkongensis and A. indistinctus isolated from blood cultures of a patient with acute appendicitis. A 35-year-old female patient with no specific medical history was admitted to the hospital due to abdominal pain, vomiting, nausea, and diarrhea experienced on the day before admission. On admission, laboratory tests revealed leukocytosis, neutropenia, and elevated C–reactive protein and procalcitonin levels. Following an abdominal computed tomography showing acute appendicitis with suspected perforation, emergency surgery was performed. Growth was observed in two anaerobic blood culture bottles after four days. After further culturing of the bacteria on Brucella Blood Agar, two types of bacteria were obtained. The two bacterial isolates, one gram-positive and one gram-negative, were unable to be identified using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Thus, 16S rRNA gene sequence analysis was performed, resulting in identification of the bacteria as C. hongkongensis and A. indistinctus. The patient was administered antibiotics and discharged two days after surgery. Although MALDI-TOF MS enables fast and accurate identification of bacteria, C. hongkongensis and A. indistinctus were not listed in the spectral library, and 16S rRNA gene sequence analysis was useful for identifying the two bacteria.

Five Cases of the Gram Variable Bacterium Paenibacillus urinalis Isolated from Clinical Specimens and its Clinical Significance

Paenibacillus urinalis was first isolated from the urine of a woman in 2008, and was reported to be a contaminant. Here, we report 5 cases of P. urinalis isolated over 5 months at a tertiary hospital. Using an API kit, 4 cases were classified as Cellulomonas species. Owing to the low reliability of API kit results and Gram stain results indicating gram variable bacilli for few specimens, MALDI-TOF MS and 16S rRNA gene sequencing were performed for identification. The last case showed Gram variable bacilli, and therefore, based on previous experience, 16S rRNA gene base sequence analysis was carried out without an additional API kit. All isolated strains were confirmed to be P. urinalis, and were judged to be contaminants. As for Gram variable bacteria, the use of current biochemical identification systems may lead to misidentification as other bacteria, which may cause unnecessary or improper use of antibiotics. Moreover, whereas most of the Paenibacillus species are reported to be contaminants, some of them are being reported as sources of infection. Therefore, more accurate identification will be necessary in the future. Accordingly, it is expected that accurate identification of this genus will help clinical physicians make decisions regarding appropriate treatment and use of antibiotics.