First Case of Necrotizing Fasciitis and Septicemia Caused by Pigmentibacter ruber.

We report the first case of necrotizing fasciitis caused by Pigmentibacter ruber. The isolated strain could not be identified by biochemical characterization or matrix-assisted laser desorption/ionization time-of-flight mass spectrometry but was identified as P. ruber by 16S ribosomal RNA and whole-genome sequencing. Although much remains unknown about the pathogenicity of this bacterial species in humans, it has been shown to cause life-threatening infections such as septicemia and necrotizing fasciitis. Because the isolate was highly resistant to ß-lactams, it was difficult to treat with antimicrobial therapy. Thus, further documentation of cases and analyses are required.

Identification of cfxA gene variants and susceptibility patterns in ß-lactamase-producing Prevotella strains.

OBJECTIVES: Antimicrobial-resistant isolates of Prevotella species, especially those resistant to ß-lactams, have become increasingly common. Here, we aimed to elucidate the underlying mechanisms contributing to the emergence and spread of antimicrobial resistance in Prevotella species. METHODS: Prevotella species were isolated from a variety of clinical specimens. ß-lactamase production was determined using nitrocefin discs, and the determination of minimum inhibitory concentration (MIC) to ten antimicrobials was done by the agar dilution method. Four resistance genes (cfxA, tetQ, ermF, and nim) and cfxA-flanking regions were detected using polymerase chain reaction. cfxA and the flanking regions were sequenced, and a phylogenetic tree was constructed based on CfxA amino acid sequences using the UPGMA method. RESULTS: Among the 45 Prevotella isolates identified, 35 (77.8%) produced ß-lactamases and had the cfxA genes. The tetQ, ermF, and nim genes were detected in 53.3%, 17.8%, and 0% of the 45 isolates, respectively. Among the 33 sequenced cfxA alleles, cfxA2 (45.5%) was the most frequent, followed by cfxA3 (42.4%) and a novel variant (cfxA7, 12.1%). The novel CfxA7 ß-lactamase had a novel L155F substitution not previously reported in CfxA variants. The MICs of all ß-lactam agents tested, excluding cefmetazole and meropenem, were lower among cfxA7-positive isolates than in cfxA2-and cfxA3-positive isolates. CONCLUSIONS: Differences in MICs of penicillins and cephalosporins may be due to amino acid substitutions in the CfxA variants, CfxA2, CfxA3, and CfxA7, among Prevotella isolates. Possession of cfxA-mobA, tetQ, and ermF may increase the risks of the emergence and spread of multidrug-resistant Prevotella species.