The role of the computerized tomography scanner in the cross-transmission of carbapenem-resistant Acinetobacter baumannii between hospitalized patients

ObjectiveTo assess the role of the computerized tomography (CT) scanner in cross-transmission of carbapenem-resistant Acinetobacter baumannii between hospitalized patients undergoing CT scan.MethodsA single-centre retrospective observational analysis of inpatients undergoing CT scans. Patient-unique CT scans were defined as ‘index cases’ (patients undergoing CT scan with carbapenem-resistant Acinetobacter baumannii (CRAB) colonization documented during the previous 60 days), ‘incident cases’ (patients found colonized with CRAB within 14 days following CT scan), and ‘negative cases’ (negative for CRAB before and after CT scan). CRAB acquisition was analysed by time interval between CT scan and CT scan of the prior index-case patient.ResultsAmongst 73 047 CT scans performed over 5 years, 4834 scans were performed within 12 hours of an index case. CRAB acquisition was detected in 20 patients (incident cases), including 16/2725 (5.8/1000 scans) who underwent CT scan within 6 hours of an index-case CT scan and 4/2109 (1.9/1000 scans) who had their CT scan 7–12 hours after the CT scan of an index-case patient (p 0.033, risk ratio 3.1, 95%CI 1.03–9.25). Patient characteristics for the two time periods were similar. While not the only significant predictor of CRAB acquisition (others included age and length of hospital stay prior to the CT scan), the time elapsed from an index case remained a significant predictor for CRAB acquisition on multivariate analysis (OR 0.84, 95%CI 0.74–0.95, p 0.007).ConclusionsPerforming a CT scan within 6 hours of a CT scan performed in a CRAB-positive patient was an independent predictor of CRAB acquisition, approximately tripling the risk. This probably reflects poor infection control practice in the CT suite.     

瑞金医院重症监护病房和烧伤病房鲍曼不动杆菌的流行病学监测和分析

目的:监测并分析瑞金医院重症监护病房(ICU)及烧伤病房鲍曼不动杆菌(Acineto bacterbaumannii,Ab)的检出率和耐药率的变化趋势,为临床预防和治疗Ab感染提供临床依据。方法:采用细菌耐药监测软件WHONET5.4回顾分析我院呼吸重症监护病房(RICU)、外科重症监护病房(SICU)、急诊重症监护病房(EICU)和烧伤病房患者体液和导管标本中检出的Ab,应用脉冲场凝胶电泳(PFGE)对泛耐药鲍曼不动杆菌(PDR-Ab)进行同源性分析。结果:2006年1月至2008年12月从我院4个病房患者中检出332株Ab,2006至2008年分别为85株、111株、136株,其中来自血液株数占3.7%,导管株数占11.2%,伤口和创面株数占31.9%,痰液株数占46.7%。4个病房中,Ab是最常见的检出菌种之一。相对于2006年,2008年Ab对临床主要抗菌药物的耐药率有显著上升(P<0.05),其对头孢哌酮-舒巴坦的耐药率最低。3年内4个病房共检出PDR-Ab57株。2007年RICU检出4株PDR-Ab,通过临床资料和PFGE分析证实为同源菌株,结合临床资料分析,高度提示为交叉感染;2008年RICU检出2株PDR-Ab虽为同源菌株,但结合临床资料分析可排除交叉感染的可能。结论:Ab在ICU和烧伤病房都是重要的检出细菌之一,其对临床常用抗菌药物耐药率呈显著上升趋势。交叉感染可能是引起Ab检出率和耐药率上升的原因之一。     

Use of RAPD-ALF analysis for investigating the frequency of bacterial cross-transmission in an adult intensive care unit

Bacterial cross-transmission was investigated during a 12-month period in an adult intensive care unit (ICU) by the generation of random amplified polymorphic DNA (RAPD) fingerprinting profiles, combined with automated laser fluorescence (ALF) analysis. The potential episodes of cross-transmission identified, were compared with those detected by the conventional first-line screen of antibiogram typing. Over the year, 215 primary gram-negative bacterial isolates were obtained from 160 patients. In total, 22 possible episodes of cross-transmission, involving 70 (44%) of the 160 patients, were identified by RAPD-ALF analysis, and 19 of these were substantiated with epidemiological evidence. Conversely, 31 possible episodes were identified on the basis of antibiogram data, but only three of these episodes, two involving Acinetobacter baumannii and one involving Serratia marcescens, correlated with those identified by RAPD-ALF analysis. It was concluded that analysis of antibiogram data alone is an unreliable method for assessing bacterial cross-transmission, unless the organism involved has a particularly stable or unusual resistance pattern. In contrast, the technique of RAPD-ALF analysis may provide a rapid and simple technique for obtaining an insight into the population dynamics of gram-negative bacteria in adult ICUs.