Nocardia abscessus Cutaneous Abscess: A Case Report and Review of the Literature / 대한임상미생물학회지

We describe a cutaneous abscess caused by Nocardia abscessus in a previously healthy woman. A 74-year-old woman presented with recurrent bullae on her left forearm that developed 1 week prior and was initially suspected to be a cutaneous infection with Mycobacteria or Tinea corporis. Histopathologically, the skin lesion formed an abscess. A smear revealed a few branched Gram-positive filamentous microorganisms that formed a creamy white colony on a blood agar plate after incubation for 3 days. The colony tested negative on acid-fast bacilli (AFB) staining, but was positive on modified AFB staining. The isolate was confirmed to be N. abscessus by 16S rRNA sequencing analysis. The isolate was susceptible to trimethoprim-sulfamethoxazole, amikacin, cefotaxime and erythromycin but resistant to penicillin. The patient was treated with clarithromycin but subsequently lost to follow-up. To the best of our knowledge, this is the first report of a human cutaneous infection with N. abscessus in Korea.

Polyphyly in 16S rRNA-based LVTree Versus Monophyly in Whole-genome-based CVTree / 基因组蛋白质组与生物信息学报·英文版

We report an important but long-overlooked manifestation of low-resolution power of 16S rRNA sequence analysis at the species level, namely, in 16S rRNA-based phylogenetic trees polyphyletic placements of closely-related species are abundant compared to those in genome-based phylogeny. This phenomenon makes the demarcation of genera within many families ambiguous in the 16S rRNA-based taxonomy. In this study, we reconstructed phylogenetic relationship for more than ten thousand prokaryote genomes using the CVTree method, which is based on whole-genome information. And many such genera, which are polyphyletic in 16S rRNA-based trees, are well resolved as monophyletic clusters by CVTree. We believe that with genome sequencing of prokaryotes becoming a commonplace, genome-based phylogeny is doomed to play a definitive role in the construction of a natural and objective taxonomy.

First isolation of Laribacter hongkongensis from stool samples of Rattus norvegicus / 中国人兽共患病学报

In order to investigate whether Laribacter hongkongensis could be detected in stool samples of Rattus norvegicus in the wild,Rattus norvegicus were trapped alive in an urban community of Guangzhou,China over a period of one year from June 2015 to May 2016,and their stool samples were examined for the presence of L.hongkongensis strains.Isolates were identified based on phenotypic characteristics and 16S rRNA sequence analysis,and were examined for their susceptibility to 19 antimicrobial agents.Further typing of the isolates was performed using multi-loci sequence typing (MLST) analysis.A total of 191 R.norvegicus were trapped alive.L.hongkongensis was identified and successfully isolated from two samples,representing a prevalence of 1.05 ％.Although the two isolates possessed similar phenotypic characteristics and have no base difference of 16S rRNA gene,they constituted two new distinct sequence types (STs),ST-163 and ST-164.This is the first report that L.hongkongensis can be detected in the intestinal tract of R.norvegicus.Results suggest that R.norvegicus could serve as carriers of L.hongkongensis and therefore could be another potential source of infection.

Misidentification of Brevibacterium casei as Propionibacterium acnes Isolated from the Blood of a Patient with Malignant Lymphoma / 대한임상미생물학회지

Brevibacterium spp. are Gram-positive, irregularly rod-shaped, strictly aerobic bacteria that resemble corynebacteria. Since they are a part of normal skin flora, they have been regarded as apathogenic, and human infections related to them are very rare. A 46-year-old man previously diagnosed with diffuse large B-cell lymphoma presented with fever without a definitive infectious source. Blood cultures from both peripheral blood and a central venous catheter showed that only aerobic bottles grew contaminants, while anaerobic bottles did not. Although the automated microbial identification system indicated Propionibacterium acnes, the isolated species was identified as B. casei by 16S rRNA sequence analysis. Our case emphasizes the utilization of 16S rRNA sequence analysis when the result from an automated system does not correspond with other laboratory findings. This is the first case of catheter-related blood stream infection due to B. casei identified by 16S rRNA sequence analysis.

Campylobacter jejuni Bacteremia in a Healthy Child / 대한임상미생물학회지

Campylobacter jejuni is one of the important bacterial pathogens causing entero-invasive diarrhea; however, C. jejuni infection is rarely complicated by bacteremia or extra-intestinal localization. In the domestic literature, the majority of the relevant reports have focused on Campylobacter fetus, which causes bacteremia more frequently than enteritis, but there are no reports of C. jejuni bacteremia in Korea. We present the case of a 13-year-old girl who presented with abdominal pain. Blood cultures revealed curved Gram- negative bacilli and small, mucoid, gray colonies on blood agar plates at 37degrees C. Biochemical tests showed oxidase-positive colonies. To confirm the species, 16S rRNA sequence analysis was performed. The isolate exhibited 99.7% homology to C. jejuni subsp. jejuni. The patient was treated with third-generation cephalosporin and aminoglycoside and had negative blood cultures after three days of treatment. She fully recovered within four days with no complications.