Identification of antimicrobial resistance genes in multidrug-resistant clinical Bacteroides fragilis isolates by whole genome shotgun sequencing.

Bacteroides fragilis constitutes the most frequent anaerobic bacterium causing bacteremia in humans. The genetic background for antimicrobial resistance in B. fragilis is diverse with some genes requiring insertion sequence (IS) elements inserted upstream for increased expression. To evaluate whole genome shotgun sequencing as a method for predicting antimicrobial resistance properties, one meropenem resistant and five multidrug-resistant blood culture isolates were sequenced and antimicrobial resistance genes and IS elements identified using ResFinder 2.1 (http://cge.cbs.dtu.dk/services/ResFinder/) and a custom BLAST database. Combinations of cfxA, cepA, cfiA, nimA, nimD, nimE, nimJ, tetQ, ermB, ermF, bexB, linAn2 and mefEn2 genes were identified in the six isolates. blaOXA-347, an open reading frame predicted to be a β-lactamase (Cheng et al., 2012), was identified in one strain. Full length IS elements were identified directly upstream of four genes, but in most cases contigs terminated 100-150 bases upstream of the gene in question. Even though partial IS elements were identified in these short sequences, certain identification could not be ascertained. Full antiobiograms for B. fragilis from genetic data will most likely require complete or nearly complete genomes. Current approaches to this are laborious and/or costly. Emerging technologies such as nanopore based single DNA strand sensing could perhaps provide a solution in the future.

Sydenham TV ，Sóki J ，Hasman H ，Wang M ，Justesen US ，ESGAI (ESCMID Study Group on Anaerobic Infections) ... -  《-》

Characterisation of a multidrug-resistant Bacteroides fragilis isolate recovered from blood of a patient in Denmark using whole-genome sequencing.

Here we describe a patient undergoing extensive abdominal surgery and hyperthermic intraperitoneal chemotherapy due to primary adenocarcinoma in the sigmoid colon with peritoneal carcinomatosis. During hospitalisation the patient suffered from bacteraemia with a multidrug-resistant Bacteroides fragilis isolate. Whole-genome sequencing of the isolate resulted in identification of nimE, cfiA and ermF genes corresponding to metronidazole, carbapenem and clindamycin resistance.

Ank N ，Sydenham TV ，Iversen LH ，Justesen US ，Wang M ... -  《-》

Fatal sepsis caused by multidrug-resistant Bacteroides fragilis, harboring a cfiA gene and an upstream insertion sequence element, in Japan.

Here, we report a case of fatal sepsis resulting from an intra-abdominal infection caused by a Bacteroides fragilis strain containing a CfiA4 metallo-β-lactamase and an upstream insertion sequence (IS) element. Meropenem was used as empiric therapy for septic shock as a result of the intra-abdominal infection, although two rounds of carbapenem treatment had been administered previously. B. fragilis was isolated from two anaerobic blood culture bottles 4 days after the onset of septic shock. Susceptibility testing revealed that the isolate was non-susceptible to all tested agents except metronidazole and tigecycline. The isolate gave a positive result in ethylenediaminetetraacetic acid and carbapenem inactivation tests, but a negative result in a double-disk synergy test using sodium mercaptoacetate. Next-generation whole-genome sequencing indicated the presence of the cfiA4, emrG and emrF genes. PCR indicated the presence of an IS element upstream of the cifA4 gene. Although carbapenem-resistant B. fragilis isolates have previously been reported, clinical sepsis by this organism is considered rare. In Japan, as in most countries worldwide, routine susceptibility testing and the detection of metallo-β-lactamases is not carried out in anaerobic organisms, including B. fragilis. The emergence of carbapenem resistance during therapy should be monitored, as B. fragilis strains containing the cfiA gene show decreased sensitivity during carbapenem therapy. Therefore, susceptibility testing and appropriate antibiotic stewardship are required in cases of anaerobic bacterial infections.

Nakamura I ，Aoki K ，Miura Y ，Yamaguchi T ，Matsumoto T ... -  《-》

The occurrence of antibiotic resistance genes in drug resistant Bacteroides fragilis isolates from Groote Schuur Hospital, South Africa.

Bacteroides fragilis, an anaerobic gut commensal and opportunistic pathogen, is a leading cause of anaerobic abscesses and bacteraemias. Treatment of infections is complicated by the emergence of resistance to several of the antibiotics used in the clinical setting. Genetic analysis of 23 B. fragilis isolates found that none of the metronidazole resistant strains carried the nimA-J genes, and no cfxA or ermF genes were detected. All of the tetracycline resistant isolates contained the tetQ gene and were sensitive to tigecycline. The cfiA gene was found in 3 of the strains, one of which was imipenem resistant and contained an upstream IS4351 insertion sequence. Another resistant strain had a unique G to A substitution in the promoter region of the cfiA gene, while the third was imipenem sensitive. Thirty percent of the isolates contained at least one plasmid, however, tetQ gene was located on the chromosome and not on any of the plasmids.

Meggersee R ，Abratt V 《-》

New cfiA variant and novel insertion sequence elements in carbapenem-resistant Bacteroides fragilis isolates from Korea.

Of 276 nonduplicate Bacteroides fragilis clinical isolates recovered from 1997 to 2004, 3 were resistant to carbapenem. cepA and cfiA alleles were detected by polymerase chain reaction in 240 (87.0%) and 11 (4.0%) of the isolates, respectively. Insertion sequence (IS) elements were found only in the 3 carbapenem-resistant B. fragilis isolates, which produced metallo-beta-lactamase at a level detectable by UV spectrophotometry. Sequence analysis showed 1 new cfiA variant, cfiA(11), and 2 novel IS elements. The cfiA(11) gene revealed 5 amino acid substitutions compared to cfiA, with 97.6% amino acid identity. The transposase, terminal inverted repeat sequence, and target site duplication sequence of the 2 novel IS elements were unique. This study reconfirmed the correlation between ISs and carbapenem resistance in B. fragilis.

Roh KH ，Kim S ，Kim CK ，Yum JH ，Kim MS ，Yong D ，Jeong SH ，Lee K ，Kim JM ，Chong Y ... -  《-》