Fecal carriage of extended-spectrum β-lactamases and AmpC-producing Escherichia coli in a Libyan community.
Fecal carriage of extended-spectrum β-lactamases and AmpC-producing Escherichia coli in a Libyan community.
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DOI：
10.1186/1476-0711-13-22
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发表时间：
2014-06-16
影响因子：
5.7
通讯作者：
Klena JD
中科院分区：
文献类型：
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作者：
Ahmed SF;Ali MM;Mohamed ZK;Moussa TA;Klena JD
超广谱 β-内酰胺酶 (ESBL)，包括 AmpC 型，是肠杆菌科细菌的重要耐药机制。 CTX-M型超广谱β-内酰胺酶目前有90多种变体，分布于全球，但区域分布似乎有所不同。 AmpC β-内酰胺酶可水解第三代头孢菌素，但在体外对克拉维酸或其他 β-内酰胺酶抑制剂的抑制具有抵抗力。据报道，在社区获得性感染的患者及其健康家庭成员中，粪便携带和具有这些耐药机制的细菌定植率。这些 ESBL 的表达会损害当前抗菌疗法的功效，可能会增加医院和社区获得性大肠杆菌 (E. coli) 感染的严重性。旨在调查从居住在利比亚城市 Zleiten 和 Abou El Khoms 的两个儿科人群中分离出的人类粪便菌群中产 ESBL 大肠杆菌的情况。对分离株进行了进一步研究，以表征编码 β-内酰胺抗性的基因，并建立遗传关系。通过纸片扩散法测定了 2001 年和 2007 年两个监测期期间从 243 名利比亚儿童的粪便中回收的具有表型特征的大肠杆菌分离株的抗生素耐药性谱。采用头孢菌素/克拉维酸双协同圆盘法进行ESBL筛选，并通过氨苯硼酸试验确认AmpC表型。 ESBL 基因进行了分子表征。确定了产 ESBL 菌株的系统发育组和多位点序列分型 (MLST)，并进行 PFGE 来比较一些优势菌株的条带图谱。 13.4% (18/134) 的大肠杆菌分离株中鉴定出 ESBL，其中 9 个分离株 (6.7%) 表现出 AmpC 活性；所有 18 个分离株均含有 CTX-M 基因。三个 CTX-M 基因家族（CTX-M-1，n = 9；CTX-M-15，n = 8 和 CTX-M-3，n = 1）分布在不同的大肠杆菌背景中（系统发育组 D，39%；B2，28%；B1，22% 和 A，11%）。 MLST 分析揭示了 14 种序列类型 (ST)，其中包括 6 种新序列类型。在 5 个 AmpC 阳性大肠杆菌中检测到编码 CMY-2 酶的基因。这些结果在粪便分离物中鉴定出产生 CTX-M 的大肠杆菌的异质克隆，表明肠道是产生 ESBL 的微生物的储存库，也是抗生素抗性基因的贩运者。
Extended-spectrum β-lactamases (ESBLs), including the AmpC type, are important mechanisms of resistance among Enterobacteriaeceae. CTX-M type extended-spectrum β- lactamases, of which there are now over 90 variants, are distributed globally, yet appear to vary in regional distribution. AmpC β-lactamases hydrolyze third generation cephalosporins, but are resistant to inhibition by clavulanate or other β-lactamase inhibitors in vitro. Fecal carriage and rates of colonization by bacteria harboring these resistance mechanisms have been reported in patients with community-acquired infections and in healthy members of their households. Expression of these ESBLs compromises the efficacy of current antibacterial therapies, potentially increasing the seriousness of hospital- and community-acquired Escherichia coli (E. coli) infections. To investigate the occurrence of ESBL-producing E. coli in human fecal flora isolated from two pediatric populations residing in the Libyan cities Zleiten and Abou El Khoms. Isolates were further studied to characterize genes encoding β-lactam resistance, and establish genetic relationships. Antibiotic resistance profiles of phenotypically characterized E. coli isolates recovered from the stools of 243 Libyan children during two surveillance periods in 2001 and 2007 were determined by the disk diffusion method. ESBL-screening was performed using the cephalosporin/clavulanate double synergy disc method, and the AmpC-phenotype was confirmed by the aminophenyl-boronic acid test. ESBL genes were molecularly characterized. Phylogenetic group and multilocus sequence typing (MLST) were determined for ESBL-producing isolates and PFGE was performed to compare banding profiles of some dominant strains. ESBLs were identified in 13.4% (18/134) of E. coli isolates, and nine isolates (6.7%) demonstrated AmpC activity; all 18 isolates contained a CTX-M gene. Three CTX-M gene families (CTX-M-1, n = 9; CTX-M-15, n = 8 and CTX-M-3, n = 1) were distributed in diverse E. coli backgrounds (phylogenetic group D, 39%; B2, 28%; B1, 22% and A, 11%). MLST analysis revealed 14 sequence type (ST) with six new sequence types. The gene encoding the CMY-2 enzyme was detected in five AmpC-positive E. coli. These results identified heterogeneous clones of CTX-M-producing E. coli in the fecal isolates, indicating that the intestinal tract acts as a reservoir for ESBL-producing organisms, and a trafficker of antibiotic resistance genes.