Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
Institute of Clinical Microbiology, University of Szeged, Szeged, Hungary.
Anaerobe. 2019 Aug;58:30-34. doi: 10.1016/j.anaerobe.2019.01.011. Epub 2019 Feb 1.
Bacteroides fragilis can be classified into division I (cfiA negative) and division II (cfiA positive) isolates. Division II isolates have a silent chromosomal carbapenemase gene (cfiA) that can become overexpressed by an insertion of a mobile genetic element and thus develop a phenotypic resistance to carbapenems. Aims of our study were (i) to determine the prevalence of B. fragilis division II (cfiA positive) isolates among blood stream and non-blood stream isolates from two major Slovenian tertiary-care hospitals and (ii) to assess its influence on phenotypic resistance to imipenem. Consecutive non-duplicate B. fragilis isolates from blood stream and non-blood stream specimens were included in the analysis from 2015 to 2017 period. Data from laboratory information system were matched with mass spectra obtained with Microflex LT instrument and MALDI Biotyper 3.1 software (Bruker Daltonik, Bremen, Germany). All mass spectra were reanalyzed using Bruker taxonomy library. Spectra with a log(score) > 2.0 were further analyzed with cfiA library that separates B. fragilis division I and II isolates based on a log(score) value difference of >0.3. Minimal inhibitory concentrations (MICs) for imipenem were determined with Etest (bioMérieux, Marcy l'Étoile, France), using supplemented Brucella agar and EUCAST breakpoints (S ≤ 2 mg/L, R > 8 mg/L). Altogether 623 consecutive B. fragilis isolates were included in the analysis; 47 (7.5%) were isolated from blood stream and 576 (92.5%) from non-blood stream specimens. Among all study isolates, 51 (8.2%) proved to belong to division II (cfiA positive). The proportions of division II isolates among blood stream and non-blood stream isolates were 14.9% and 7.6%, respectively (p = 0.081, ns). In total, 1.3% (n = 8) were non-susceptible to imipenem (MIC >2 mg/L); 4.3% (n = 2) among blood stream and 1% (n = 6) among non-blood stream isolates. All imipenem resistant isolates belonged to division II. Modal MICs (MIC range) were 0.064 mg/L (0.016 mg/L-2 mg/L) and 0.125 mg/L (0.064 mg/L-≥32 mg/L) for division I and II isolates, respectively.
脆弱拟杆菌可分为 I 型（cfiA 阴性）和 II 型（cfiA 阳性）分离株。II 型分离株具有沉默的染色体碳青霉烯酶基因（cfiA），该基因可通过插入移动遗传元件而过度表达，从而表现出对碳青霉烯类药物的表型耐药性。我们研究的目的是：（i）确定来自斯洛文尼亚两家主要的三级保健医院的血流和非血流分离株中脆弱拟杆菌 II 型（cfiA 阳性）分离株的流行率；（ii）评估其对亚胺培南表型耐药性的影响。从 2015 年到 2017 年期间，从血流和非血流标本中连续分离出非重复的脆弱拟杆菌分离株进行分析。实验室信息系统的数据与使用 Microflex LT 仪器和 MALDI Biotyper 3.1 软件（Bruker Daltonik，不来梅，德国）获得的质谱进行匹配。使用 Bruker 分类库重新分析所有质谱。对 log（得分）>2.0 的谱进行进一步分析，使用 cfiA 库将脆弱拟杆菌 I 型和 II 型分离株基于 log（得分）值差异>0.3 进行分离。使用 Etest（bioMérieux，Marcy l'Étoile，法国），在补充布鲁氏琼脂和 EUCAST 折点（S≤2mg/L，R>8mg/L）下测定亚胺培南的最小抑菌浓度（MIC）。共纳入 623 例连续脆弱拟杆菌分离株进行分析；47 例（7.5%）从血流中分离，576 例（92.5%）从非血流标本中分离。在所有研究的分离株中，有 51 株（8.2%）被证明属于 II 型（cfiA 阳性）。血流和非血流分离株中 II 型分离株的比例分别为 14.9%和 7.6%（p=0.081，ns）。总共，有 1.3%（n=8）对亚胺培南不敏感（MIC>2mg/L）；血流中 4.3%（n=2）和非血流中 1%（n=6）。所有亚胺培南耐药的分离株均属于 II 型。I 型和 II 型分离株的模式 MIC（MIC 范围）分别为 0.064mg/L（0.016mg/L-2mg/L）和 0.125mg/L（0.064mg/L-≥32mg/L）。
