Pallecchi Lucia, Bartoloni Alessandro, Fiorelli Costanza, Mantella Antonia, Di Maggio Tiziana, Gamboa Herlan, Gotuzzo Eduardo, Kronvall Göran, Paradisi Franco, Rossolini Gian Maria
Dipartimento di Biologia Molecolare, Sezione di Microbiologia, Università di Siena, Policlinico Santa Maria alle Scotte, Siena, Italy.
Antimicrob Agents Chemother. 2007 Aug;51(8):2720-5. doi: 10.1128/AAC.00026-07. Epub 2007 Jun 4.
A survey carried out in 2005 among members of a healthy population of children living in Bolivia and Peru revealed that fecal carriage of Escherichia coli strains resistant to expanded-spectrum cephalosporins was remarkably increased compared to that observed in the same settings in 2002 (1.7% in 2005 versus 0.1% in 2002). In this work, we demonstrated that this phenomenon was mainly related to the dissemination of CTX-M-type extended-spectrum beta-lactamase (ESBL) determinants among commensal E. coli strains. Of 50 ESBL-producing isolates collected in the 2005 survey, 44 harbored a CTX-M-type and 6 an SHV-type (SHV-2 or SHV-12) ESBL. Compared to 2002 results, an increased diversity of CTX-M-type ESBLs was also observed: members of the CTX-M-1 group (CTX-M-15) emerged in Bolivia (where only CTX-M-2 was observed in 2002), while members of the CTX-M-9 group (CTX-M-14 and CTX-M-24) emerged in Peru (where only CTX-M-15 and CTX-M-2 were observed in 2002). A new CTX-M-2 variant named CTX-M-56 was also detected. Molecular characterization of the CTX-M-producing isolates and gene transfer experiments suggested that different mechanisms could be involved in the spreading of different CTX-M group determinants and revealed that additional resistance determinants for non-beta-lactam antibiotics were preferentially carried by plasmids encoding certain CTX-M variants (CTX-M-15 and variants of the CTX-M-2 group). Three CTX-M-15-encoding conjugative plasmids from Peruvian isolates carried the new fluoroquinolone resistance gene aac(6')-Ib-cr. To our best knowledge, this is the first report of the detection of aac(6')-Ib-cr in Latin America.
2005年对生活在玻利维亚和秘鲁的健康儿童群体成员进行的一项调查显示，与2002年在相同环境中观察到的情况相比，对广谱头孢菌素耐药的大肠杆菌菌株的粪便携带率显著增加（2005年为1.7%，2002年为0.1%）。在这项研究中，我们证明这种现象主要与CTX-M型超广谱β-内酰胺酶（ESBL）决定簇在共生大肠杆菌菌株中的传播有关。在2005年调查收集的50株产ESBL分离株中，44株携带CTX-M型ESBL，6株携带SHV型（SHV-2或SHV-12）ESBL。与2002年的结果相比，还观察到CTX-M型ESBL的多样性增加：CTX-M-1组（CTX-M-15）的成员出现在玻利维亚（2002年仅观察到CTX-M-2），而CTX-M-9组（CTX-M-14和CTX-M-24）的成员出现在秘鲁（2002年仅观察到CTX-M-15和CTX-M-2）。还检测到一种名为CTX-M-56的新CTX-M-2变体。对产CTX-M分离株的分子特征分析和基因转移实验表明，不同的机制可能参与不同CTX-M组决定簇的传播，并揭示非β-内酰胺类抗生素的其他耐药决定簇优先由编码某些CTX-M变体（CTX-M-15和CTX-M-2组变体）的质粒携带。来自秘鲁分离株的三个携带CTX-M-15的接合质粒携带了新的氟喹诺酮耐药基因aac(6')-Ib-cr。据我们所知，这是在拉丁美洲首次检测到aac(6')-Ib-cr的报告。
