Begum N, Shamsuzzaman S M
Dhaka Medical College, Department of Microbiology, Dhaka, Bangladesh.
Malays J Pathol. 2016 Dec;38(3):241-249.
Extended-spectrum β-lactamase (ESBL) producing uropathogens has become prevalent worldwide. E. coli O25b-ST131 clone, associated with blaCTX-M-15, has been reported from many parts of the world and is frequently associated with multidrug resistance. Thus far, there are no reports about this clone in Bangladesh. The objective of this study was to investigate ESBL producing uropathogens and to survey the prevalence of E. coli O25b-ST131 clone among ESBL positive E. coli isolates.
From symptomatic urinary tract infection cases, a total of 800 urine samples were collected. Bacterial identification and antimicrobial susceptibility testing was performed using established methods. Screening of ESBL producers was done using the disk diffusion method. Screening positive isolates were phenotypically confirmed by double disk synergy (DDS) test. Genes encoding ESBLs (blaCTX-M-15, blaOXA-1) were identified both by PCR and DNA sequencing. Phenotypic positive ESBL producers were also studied by PCR for existence of class 1 integron. Subsequently, O25b-ST131 clone was identified by allele specific PCR.
Of 138 gram-negative uropathogens, 45 (32.6%) were positive for ESBLs. ESBL producers showed high frequency of antimicrobial resistance except imipenem. Among 45 ESBL producers, 36 (80%) produced blaCTX-M-15, 18 (40%) produced blaOXA-1. Fifteen (33.3%) strains simultaneously produced both blaOXA-1 and blaCTX-M-15. Class 1 integron was present in 30 (66.7%) isolates. Of the 31 blaCTX-M-15 positive E. coli, 22 (71%) were positive for E. coli O25b-ST131 clone and all (100%) belonged to B2 phylogenetic group.
Rising antimicrobial resistance among uropathogens, and especially the emergence of blaCTX-M-15 positive E. coli O25b-ST131 clone in Bangladesh has provided urgency to the development of novel preventive and therapeutic strategies.
产超广谱β-内酰胺酶（ESBL）的尿路致病菌在全球范围内已变得普遍。与blaCTX-M-15相关的大肠杆菌O25b-ST131克隆已在世界许多地区被报道，并且经常与多重耐药性相关。迄今为止，孟加拉国尚无关于该克隆的报道。本研究的目的是调查产ESBL的尿路致病菌，并调查大肠杆菌O25b-ST131克隆在ESBL阳性大肠杆菌分离株中的流行情况。
从有症状的尿路感染病例中，共收集了800份尿液样本。使用既定方法进行细菌鉴定和抗菌药物敏感性测试。使用纸片扩散法筛选产ESBL菌。筛选阳性分离株通过双纸片协同试验（DDS）进行表型确认。通过PCR和DNA测序鉴定编码ESBLs（blaCTX-M-15、blaOXA-1）的基因。对表型阳性的产ESBL菌也通过PCR研究1类整合子的存在情况。随后，通过等位基因特异性PCR鉴定O25b-ST131克隆。
在138株革兰氏阴性尿路致病菌中，45株（32.6%）ESBLs呈阳性。除亚胺培南外，产ESBL菌显示出较高的抗菌药物耐药率。在45株产ESBL菌中，36株（80%）产生blaCTX-M-15，18株（40%）产生blaOXA-1。15株（33.3%）菌株同时产生blaOXA-1和blaCTX-M-15。30株（66.7%）分离株中存在1类整合子。在31株blaCTX-M-15阳性大肠杆菌中，22株（71%）大肠杆菌O25b-ST131克隆呈阳性，且全部（100%）属于B2系统发育群。
尿路致病菌中抗菌药物耐药性的上升，尤其是孟加拉国blaCTX-M-15阳性大肠杆菌O25b-ST131克隆的出现，为开发新的预防和治疗策略提供了紧迫性。
