Woodford Neil, Kaufmann Mary E, Karisik Edi, Hartley John W
Centre for Infections, Health Protection Agency, London, UK.
J Antimicrob Chemother. 2007 Jan;59(1):106-9. doi: 10.1093/jac/dkl435. Epub 2006 Nov 6.
To study the clonality of gentamicin-resistant, extended-spectrum beta-lactamase (ESBL)-negative and ESBL-producing Escherichia coli isolated from community-onset urinary tract infections (UTIs) in Cornwall.
Isolates were identified by API, susceptibilities were determined by local disc testing, and MICs were determined at the reference laboratory, both interpreted using BSAC guidelines. bla(CTX-M) genes were sought by PCR, and isolates were compared by PFGE.
In the years 2004 and 2005, 69 E. coli were submitted by Truro (Cornwall) laboratory for reference laboratory testing: these included 14 gentamicin-resistant, ESBL-negative isolates; 45 with group 1 CTX-M enzymes; seven with group 9 CTX-M enzymes; and three with non-CTX-M ESBLs. By PFGE, nine gentamicin-resistant, ESBL-negative E. coli were distinct (<85% similarity) from all the ESBL producers, but three were related to producers of group 1 CTX-M enzymes, and two isolates were related to a non-CTX-M ESBL producer. An outbreak strain was identified, represented by 11 gentamicin-resistant and one gentamicin-susceptible isolates, all with group 1 CTX-M enzymes, and two gentamicin-resistant, ESBL-negative isolates. This was distinct by PFGE from nationally distributed CTX-M-producing strains. Five of nine patients infected with this strain had been on the same ward in a local hospital; four presented with community-onset UTIs; one inpatient developed a hospital-acquired bacteraemia. Of the other four patients presenting with community-onset UTIs, three were admitted to different hospitals and the fourth had only attended an outpatient clinic.
Community-onset, ESBL-producing and non-producing E. coli were diverse. Two ESBL-negative isolates were closely related to a local CTX-M-producing outbreak strain, suggesting gain or loss of a bla(CTX-M)-carrying plasmid. An outbreak strain was linked with prior hospital admission and appeared not to represent genuine community acquisition.
研究从康沃尔郡社区获得性尿路感染（UTI）中分离出的耐庆大霉素、超广谱β-内酰胺酶（ESBL）阴性及产ESBL的大肠埃希菌的克隆性。
采用API鉴定分离株，通过局部纸片法测定药敏，在参考实验室测定最低抑菌浓度（MIC），均按照英国抗菌化疗学会（BSAC）指南进行解读。通过聚合酶链反应（PCR）查找bla(CTX-M)基因，并用脉冲场凝胶电泳（PFGE）对分离株进行比较。
2004年和2005年，特鲁罗（康沃尔郡）实验室提交了69株大肠埃希菌供参考实验室检测：其中包括14株耐庆大霉素、ESBL阴性分离株；45株携带1组CTX-M酶；7株携带9组CTX-M酶；3株携带非CTX-M型ESBL。通过PFGE分析，9株耐庆大霉素、ESBL阴性的大肠埃希菌与所有产ESBL菌株不同（相似度<85%），但有3株与1组CTX-M酶产生菌相关，2株分离株与1株非CTX-M型ESBL产生菌相关。鉴定出1株暴发菌株，由11株耐庆大霉素和1株庆大霉素敏感分离株代表，均携带1组CTX-M酶，以及2株耐庆大霉素、ESBL阴性分离株。通过PFGE分析，该菌株与全国分布的产CTX-M菌株不同。感染该菌株的9例患者中有5例曾在当地医院的同一病房；4例表现为社区获得性UTI；1例住院患者发生了医院获得性菌血症。在其他4例表现为社区获得性UTI的患者中，3例入住不同医院，第4例仅去过门诊。
社区获得性、产ESBL和不产ESBL的大肠埃希菌具有多样性。2株ESBL阴性分离株与当地1株产CTX-M的暴发菌株密切相关，提示携带bla(CTX-M)的质粒获得或丢失。1株暴发菌株与先前的住院史有关，似乎并非真正的社区获得。
