Cagnacci Simone, Gualco Laura, Roveta Simona, Mannelli Stefania, Borgianni Luisa, Docquier Jean-Denis, Dodi Ferdinando, Centanaro Monica, Debbia Eugenio, Marchese Anna, Rossolini Gian Maria
Di.S.C.A.T., Microbiology Unit, University of Genoa, Genoa, Italy.
J Antimicrob Chemother. 2008 Feb;61(2):296-300. doi: 10.1093/jac/dkm471. Epub 2007 Dec 6.
To investigate the first Italian outbreak of bloodstream infections caused by multidrug-resistant (MDR) Klebsiella pneumoniae producing metallo-beta-lactamase (MBL), which occurred in three wards of one large tertiary-care hospital in Genoa, Italy, from September 2004 to March 2005.
MBL production was screened by an imipenem-EDTA disc synergy test and confirmed by a conventional hydrolysis test. Antibiotic susceptibility was determined by broth microdilution or disc diffusion. PFGE was used to study the genetic relatedness of isolates. PCR and sequencing were carried out to identify the beta-lactamase genes and to analyse the genetic context of the MBL gene. Outer membrane protein (OMP) profiles were analysed by SDS-PAGE.
Nine cases of bloodstream infections caused by an MDR strain of K. pneumoniae producing the VIM-1 MBL and the SHV-5 extended-spectrum beta-lactamase (ESBL) were identified. The isolates exhibited various carbapenem resistance levels (imipenem MICs ranged from 4 to 64 mg/L) and were resistant to other beta-lactams, fluoroquinolones, trimethoprim/sulfamethoxazole and chloramphenicol. The isolate with the highest imipenem MIC also lacked the k36 OMP. The bla(VIM-1) gene cassette was part of the variable region of a class 1 integron that also included an aac(6')-IIc cassette. The ESBL and MBL genes were transferable by conjugation.
This is the first report on the emergence of an MDR strain of K. pneumoniae producing the VIM-1 MBL, causing an outbreak of bloodstream infections in an Italian hospital. The strain evolved through OMP alterations generating a mutant with increased carbapenem resistance.
调查2004年9月至2005年3月在意大利热那亚一家大型三级医院的三个病房发生的由产金属β-内酰胺酶（MBL）的多重耐药（MDR）肺炎克雷伯菌引起的首次意大利血流感染暴发。
通过亚胺培南-EDTA纸片协同试验筛选MBL的产生，并通过常规水解试验进行确认。采用肉汤微量稀释法或纸片扩散法测定抗生素敏感性。用脉冲场凝胶电泳（PFGE）研究分离株的遗传相关性。进行聚合酶链反应（PCR）和测序以鉴定β-内酰胺酶基因并分析MBL基因的遗传背景。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）分析外膜蛋白（OMP）图谱。
鉴定出9例由产VIM-1 MBL和SHV-5超广谱β-内酰胺酶（ESBL）的MDR肺炎克雷伯菌菌株引起的血流感染病例。分离株表现出不同的碳青霉烯耐药水平（亚胺培南最低抑菌浓度[MIC]范围为4至64 mg/L），并且对其他β-内酰胺类、氟喹诺酮类、甲氧苄啶/磺胺甲恶唑和氯霉素耐药。亚胺培南MIC最高的分离株也缺乏k36 OMP。bla(VIM-1)基因盒是1类整合子可变区的一部分，该可变区还包括一个aac(6')-IIc基因盒。ESBL和MBL基因可通过接合转移。
这是关于产VIM-1 MBL的MDR肺炎克雷伯菌菌株出现并在一家意大利医院引起血流感染暴发的首次报告。该菌株通过OMP改变进化，产生了对碳青霉烯耐药性增加的突变体。
