Suzuki Satowa, Shibata Naohiro, Yamane Kunikazu, Wachino Jun-ichi, Ito Kenitiro, Arakawa Yoshichika
Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1 Musashi-murayama, Tokyo 208-0011,
J Antimicrob Chemother. 2009 Jan;63(1):72-9. doi: 10.1093/jac/dkn463. Epub 2008 Nov 11.
In the early 2000s, there was a rapid increase in extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in hospital settings throughout Japan. The reasons for this rapid increase are unclear.
Between 2002 and 2003, 142 clinical isolates of E. coli suspected of producing ESBL were obtained from 37 hospitals and commercial clinical laboratories in geographically distinct regions throughout Japan. They were tested for ESBL types and further subtyped for serogroups, fimH single nucleotide polymorphism, pulsed-field gel electrophoresis patterns and multilocus sequence type (MLST). Representative isolates were also subjected to plasmid analysis.
Of 142 E. coli isolates suspected of producing ESBL, 130 were confirmed as harbouring blaCTX-M by PCR analysis and sequencing. Of these, 84 (65%) harboured CTX-M-9-group blaCTX-M. Two serogroups O25 and O86 accounted for 41% of the 130 blaCTX-M-positive E. coli. All O86 serogroup strains belonged to ST38 by MLST and they formed 18% of all the blaCTX-M-positive E. coli. Serogroup O25 strains belonged to ST131 and ST73, and formed 21% and 1% of blaCTX-M-positive E. coli, respectively. Seven characterized plasmids carrying blaCTX-M genes belonged to three distinct incompatibility groups: IncF, IncN and IncI1.
In this study, clonally related strains of E. coli accounted for a large proportion of blaCTX-M-positive E. coli. This high proportion of clonal groups identified in different regions of Japan suggests their recent spread by mechanisms other than healthcare-associated transmission. These observations imply that restricting antimicrobial use in human clinical settings may have limited impact on the spread of ESBL-producing E. coli.
21世纪初，日本各地医院中产超广谱β-内酰胺酶（ESBL）的大肠杆菌迅速增多。这种快速增长的原因尚不清楚。
在2002年至2003年期间，从日本各地地理上不同区域的37家医院和商业临床实验室获得了142株疑似产ESBL的大肠杆菌临床分离株。对它们进行了ESBL类型检测，并进一步对血清群、fimH单核苷酸多态性、脉冲场凝胶电泳图谱和多位点序列类型（MLST）进行了亚型分析。代表性分离株还进行了质粒分析。
在142株疑似产ESBL的大肠杆菌分离株中，通过PCR分析和测序确认130株携带blaCTX-M。其中，84株（65%）携带CTX-M-9组blaCTX-M。血清群O25和O86占130株blaCTX-M阳性大肠杆菌的41%。所有O86血清群菌株通过MLST属于ST38，它们占所有blaCTX-M阳性大肠杆菌的18%。血清群O25菌株属于ST131和ST73，分别占blaCTX-M阳性大肠杆菌的21%和1%。7个携带blaCTX-M基因的特征性质粒属于3个不同的不相容群：IncF、IncN和IncI1。
在本研究中，大肠杆菌的克隆相关菌株在blaCTX-M阳性大肠杆菌中占很大比例。在日本不同地区鉴定出的如此高比例的克隆群表明它们最近是通过医疗保健相关传播以外的机制传播的。这些观察结果意味着在人类临床环境中限制抗菌药物的使用可能对产ESBL大肠杆菌的传播影响有限。
