Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India-202002.
Ann Clin Microbiol Antimicrob. 2010 Jan 14;9:2. doi: 10.1186/1476-0711-9-2.
The study aimed at (i) characterizing the mode of transmission of bla(CTX-M) and bla(TEM-1) among extended-spectrum-beta-lactamase (ESBL)-producing Escherichia coli strains isolated from infected diabetic foot ulcers, and (ii) identifying the risk factors for "sex-associated multidrug resistant Gram-negative bacterial (MDRGNB)-infection status" of the ulcers.
Seventy-seven diabetic patients having clinically infected foot ulcers were studied in a consecutive series. The E. coli strains isolated from the ulcers were screened for bla(CTX-M), bla(TEM-1), armA, rmtA and rmtB during the 2-year study-period. PCR amplified bla(CTX-M) genes were cloned and sequenced. Enterobacterial repetitive intergenic consensus (ERIC)-PCR was used for the analysis of genetic relatedness of the ESBL-producers. Risk factors for "sex-associated MDRGNB-infection status" of ulcers were assessed. Modeling was performed using Swiss-Model-Server and verified by Procheck and verify3D programmes. Discovery Studio2.0 (Accelrys) was used to prepare Ramachandran plots. Z-scores were calculated using 'WHAT IF'-package. Docking of cefotaxime with modeled CTX-M-15 enzyme was performed using Hex5.1.
Among 51 E. coli isolates, 14 (27.5%) ESBL-producers were identified. Only 7 Class1 integrons, 2 bla(CTX-M-15), and 1 bla(TEM-1) were detected. Ceftazidime and cefotaxime resistance markers were present on the plasmidic DNA of both the bla(CTX-M-15) positive strains and were transmissible through conjugation. The residues Asn132, Glu166, Pro167, Val172, Lys234 and Thr235 of CTX-M-15 were found to make important contacts with cefotaxime in the docked-complex. Multivariate analysis proved 'Glycemic control at discharge' as the single independent risk factor.
Male diabetic patients with MDRGNB-infected foot ulcers have poor glycemic control and hence they might have higher mortality rates compared to their female counterparts. Plasmid-mediated conjugal transfer, albeit at a low frequency might be the possible mechanism of transfer of bla(CTX-M-15) resistance marker in the present setting. Since the docking results proved that the amino acid residues Asn132, Glu166, Pro167, Val172, Lys234 and Thr235 of CTX-M-15 (enzyme) make important contacts with cefotaxime (drug) in the 'enzyme-drug complex', researchers are expected to duly utilize this information for designing more potent and versatile CTX-M-inhibitors.
本研究旨在：（i）描述感染性糖尿病足溃疡中产超广谱β-内酰胺酶（ESBL）的大肠杆菌菌株bla（CTX-M）和bla（TEM-1）传播模式；（ii）确定溃疡“与性别相关的多药耐药性革兰氏阴性菌（MDRGNB）感染状态”的相关危险因素。
在连续 2 年的研究期间，对 77 例患有临床感染性糖尿病足溃疡的糖尿病患者进行了研究。从溃疡中分离出的大肠杆菌菌株在研究期间筛选 bla（CTX-M）、bla（TEM-1）、armA、rmtA 和 rmtB。扩增的 bla（CTX-M）基因进行克隆和测序。肠杆菌重复基因间一致性（ERIC）-PCR 用于分析 ESBL 生产者的遗传相关性。评估溃疡“与性别相关的 MDRGNB 感染状态”的危险因素。使用 Swiss-Model-Server 进行建模，并使用 Procheck 和 verify3D 程序进行验证。Discovery Studio2.0（Accelrys）用于准备 Ramachandran 图。使用“WHAT IF”-程序包计算 Z 分数。使用 Hex5.1 将头孢噻肟与建模的 CTX-M-15 酶进行对接。
在 51 株大肠杆菌分离株中，鉴定出 14 株（27.5%）ESBL 生产者。仅检测到 7 个 Class1 整合子、2 个 bla（CTX-M-15）和 1 个 bla（TEM-1）。头孢他啶和头孢噻肟耐药标记均存在于 bla（CTX-M-15）阳性菌株的质粒 DNA 中，并可通过接合传递。CTX-M-15 的残基 Asn132、Glu166、Pro167、Val172、Lys234 和 Thr235 与对接复合物中的头孢噻肟有重要接触。多变量分析证明“出院时的血糖控制”是唯一的独立危险因素。
患有 MDRGNB 感染性糖尿病足溃疡的男性糖尿病患者血糖控制较差，因此与女性相比，他们的死亡率可能更高。尽管频率较低，但可能是 bla（CTX-M-15）耐药标记在目前情况下通过质粒介导的接合转移的可能机制。由于对接结果表明 CTX-M-15（酶）的氨基酸残基 Asn132、Glu166、Pro167、Val172、Lys234 和 Thr235（酶）与头孢噻肟（药物）在“酶-药物复合物”中形成重要接触，研究人员有望充分利用这些信息设计更有效和通用的 CTX-M 抑制剂。
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