Hospital outbreak caused by a carbapenem-resistant strain of Acinetobacter baumannii: patient prognosis and risk-factors for colonisation and infection

Between October 2001 and August 2002, 30 hospital patients became infected or colonised by a multiresistant (including to carbapenems) epidemic strain of Acinetobacter baumannii (AbMR) in a hospital outbreak. This study analysed the risk-factors associated with acquisition of this epidemic strain and investigated the prognosis of patients infected by AbMR, with the aim of elucidating factors which lead to mortality. A case-control study of the acquisition of AbMR in patients infected or colonised in the hospital outbreak was performed. Independent risk-factors leading to death were studied by logistic regression analysis. Multivariate analysis of the risk-factors for colonisation/infection with AbMR revealed an independent association with the presence of an arterial catheter (OR, 1.13; 95% CI, 1.03-1.25) and administration of imipenem as monotherapy (OR, 11.12; 95% CI, 2.33-53.09). Multivariate analysis of the prognostic features leading to mortality revealed a significant association with hypotension or shock (OR, 24.63; 95% CI, 1.56-387.56) at the time of bacterial isolation.     

Effect of basic amino acids on susceptibility to carbapenems in clinical Pseudomonas aeruginosa isolates

We evaluated effects of medium composition, including basic amino acid content and pH, on susceptibility to carbapenems such as imipenem, panipenem and meropenem, in clinical isolates of Pseudomonas aeruginosa. Susceptibility to carbapenems was reduced by basic amino acids in the medium, while susceptibilities to ceftazidime and aztreonam were not. Among carbapenems, susceptibility to panipenem was most sharply reduced by addition of basic amino acids to 1:16 Mueller-Hinton agar (MHA). In 174 of 175 clinical isolates, MICs for carbapenems were affected to different degrees by medium composition. One isolate, in which MICs for carbapenems did not differ between MHA and 1:16 MHA, showed reduced production of porin (OprD). Our results suggest that susceptibility to individual carbapenems, especially panipenem, is difficult to evaluate based on MICs for other carbapenems determined on MHA. For a better prediction of antibiotic efficacy, it may be important to evaluate the susceptibility for each carbapenem individually.     

Molecular epidemiology of a clonal outbreak of multidrug-resistant Acinetobacter baumannii in a university hospital in Italy

This study investigated the molecular epidemiology of a clonal outbreak of multidrug-resistant Acinetobacter baumannii that occurred between June 2003 and June 2004 in a tertiary-care hospital in Naples, Italy. A. baumannii was isolated from 74 patients, of whom 38 were infected and 36 were colonised. Thirty-three patients had ventilator-associated pneumonia, three had hospital-acquired pneumonia, and two had sepsis. Genotypic analysis of 45 available A. baumannii isolates revealed two distinct pulsed-field gel electrophoresis (PFGE) patterns. Of these, PFGE pattern 1 was represented by isolates from 44 patients and was identical to that of an epidemic A. baumannii clone isolated in another hospital of Naples during 2002. All A. baumannii isolates of PFGE type 1 showed identical multiresistant antibiotypes, characterised by resistance to all antimicrobial agents tested, including carbapenems, with the exception of colistin. In these isolates, inhibition of OXA enzymes by 200 mM NaCl reduced the imipenem MIC by up to four-fold. Molecular analysis of antimicrobial resistance genes showed that all A. baumannii isolates of PFGE type 1 harboured a class 1 integron containing the aacA4, orfX and bla(OXA-20) gene cassettes, an ampC gene and a bla(OXA-51)-like allele. Moreover, a bla(OXA-58)-like gene surrounded by the regulatory elements ISAba2 and ISAba3 was identified in a 30-kb plasmid from A. baumannii isolates of PFGE type 1, but not PFGE type 2. Thus, selection of a single A. baumannii clone producing an OXA-58-type carbapenem-hydrolysing oxacillinase was responsible for the increase in the number of A. baumannii infections that occurred in this hospital.     

Carbapenem-resistant and OXA-23-producing Acinetobacter baumannii isolates in the United Arab Emirates

Five carbapenem-resistant Acinetobacter baumannii isolates, collected from the United Arab Emirates in 2006, were investigated to identify the mechanism(s) responsible for carbapenem resistance. Genotyping was performed by pulsed-field gel electrophoresis, and the location of the bla _OXA-23 gene was determined by using the endonuclease I Ceu I technique and mating-out assays. The four isolates in which the bla _OXA-23 gene was located on the chromosome within a Tn 2006 composite transposon were clonally related. The single non-clonally related isolate harboured the bla _OXA-23 gene on a 70-kb transferable plasmid. This study reports on the dissemination of OXA-23-producing A. baumannii isolates in the Middle East.     

Antimicrobial Susceptibility Profiles of Gram-Negative Bacteria Causing Infections Collected Across India during 2014–2016: Study for Monitoring Antimicrobial Resistance Trend Report

Background: The emergence of antibiotic resistance among bacterial pathogens in the hospital and community has increased the concern to the health-care providers due to the limited treatment options. Surveillance of antimicrobial resistance (AMR) in frequently isolated bacterial pathogens causing severe infections is of great importance. The data generated will be useful for the clinicians to decide empiric therapy on the local epidemiological resistance profile of the antimicrobial agents. This study aims to monitor the distribution of bacterial pathogen and their susceptibility pattern to the commonly used antimicrobial agents. Materials and Methods: This study includes Gram-negative bacilli collected from intra-abdominal, urinary tract and respiratory tract infections during 2014–2016. Isolates were collected from seven hospitals across India. All the study isolates were characterised up to species level, and minimum inhibitory concentration was determined for a wide range of antimicrobials included in the study panel. The test results were interpreted as per standard Clinical Laboratory Standards Institute guidelines. Results: A total of 2731 isolates of gram-negative bacteria were tested during study period. The most frequently isolated pathogens were 44% of Escherichia coli (n = 1205) followed by 25% of Klebsiella pneumoniae (n = 676) and 11% of Pseudomonas aeruginosa (n = 308). Among the antimicrobials tested, carbapenems were the most active, followed by amikacin and piperacillin/tazobactam. The rate of extended-spectrum beta-lactamase (ESBL)-positive isolates were ranged from 66%–77% in E. coli to 61%–72% in K. pneumoniae, respectively. Overall, colistin retains its activity in > 90% of the isolates tested and appear promising. Conclusion: Increasing rates of ESBL producers have been noted, which is alarming. Further, carbapenem resistance was also gradually increasing, which needs much attention. Overall, this study data show that carbapenems, amikacin and colistin continue to be the best agents available to treat drug-resistant infections. Thus continuous monitoring of susceptibility profile of the clinically important Gram-negative pathogens is of great importance to guide effective antimicrobial therapy.     

Identification and screening of carbapenemase-producing Enterobacteriaceae

Carbapenem-hydrolysing β-lactamases are the most powerful β-lactamases, being able to hydrolyse almost all β-lactams. They are mostly of the KPC, VIM, IMP, NDM and OXA-48 types. Their current extensive spread worldwide in Enterobacteriaceae is an important source of concern, as these carbapenemase producers are multidrug-resistant. Detection of infected patients and of carriers are the two main approaches for prevention of their spread. Phenotypic and molecular-based techniques are able to identify these carbapenemase producers, although with variable efficiencies. The detection of carriers still relies mostly on the use of screening culture media.     

抑制剂增强碳青霉烯类灭活法对革兰阴性杆菌碳青霉烯酶初步分类的评价

目的评价抑制剂增强碳青霉烯类灭活法(ieCIM)对革兰阴性杆菌碳青霉烯酶检测及初步分类的可靠性。方法分别以他唑巴坦和乙二胺四乙酸作为碳青霉烯酶抑制剂,对CIM进行改良。选取临床分离的198株肠杆菌科细菌和35株非发酵菌,采用ieCIM检测碳青霉烯酶并进行初步分类,以PCR方法检测碳青霉烯酶基因作对比。结果 198株肠杆菌科细菌中碳青霉烯酶基因阳性101株,CIM检测阳性99株;碳青霉烯酶基因阴性97株,CIM检测均阴性。35株非发酵菌中碳青霉烯酶基因阳性25株,CIM检测阳性24株;碳青霉烯酶基因阴性10株,CIM检测均阴性。使用ieCIM初步分类碳青霉烯酶,87株产A类酶菌株中检出85株(97.7%),25株产B类酶菌株中检出22株(88.0%),12株产D类酶菌株和2株同时产A、B类酶菌株全部检出,ieCIM检测敏感性为96%,特异性100%。结论 ieCIM与基因检测结果一致性高,适合临床微生物常规工作中对碳青霉烯酶的检测及初步分类。     

Novel β-lactam/β-lactamase inhibitors versus alternative antibiotics for the treatment of complicated intra-abdominal infection and complicated urinary tract infection: a meta-analysis of randomized controlled trials

Introduction: The aim of this study is to compare the efficacy and safety of novelBL/BLIs with alternative antibiotics for the treatment of cIAI and cUTI.

Area covered: We performed a systematic review and meta-analysis of all randomized controlled trials comparing novel BL/BLIs with other antibiotics for the treatment of cIAI and cUTI. The primary outcome included clinical and microbiological treatment success.

Expert commentary: We found that novel BL/BLIs obtained a similar clinical outcome with other antibiotics in CE population (OR = 1.07, 95%CI = (0.80, 1.44), P = 0.64). However, novel BL/BLIs had better clinical treatment success in the cUTI subgroup (OR = 2.14, 95%CI = (1.06, 4.31), P = 0.03). Furthermore, novel BL/BLIs achieved significant microbiological treatment success in patie nts with cUTI (OR = 1.70, 95%CI = (1.29, 2.25), P = 0.0002) and had higher eradication rates for Gram-negative pathogens (OR = 1.82, 95%CI = (1.26, 2.64), P = 0.001) including E.coli and K.pneumoniae. No difference was observed concerning the incidence of mortality and adverse events between the two groups. Therefore, we concluded that novel BL/BLIs are not inferior to other available antibiotics for the treatment of cIAI, and they have advantages in patients with cUTI. Simultaneously, they are sensitive to Gram-negative pathogens, especially for E.coli and K.pneumoniae.     

ICU患者血流感染耐碳青霉烯类鲍曼不动杆菌同源性分析

目的了解某院重症监护病房(ICU)血流感染患者分离的耐碳青霉烯类鲍曼不动杆菌(CRAB)同源性。方法收集该院ICU2012年1—12月血流感染患者血液、下呼吸道和静脉导管尖端分离的CRAB,进行药物敏感试验,以及运用脉冲场凝胶电泳(PFGE)分析菌株同源性。结果 50株CRAB分离自患者血液26株、下呼吸道20株、静脉导管4株;对哌拉西林、哌拉西林/他唑巴坦、氨苄西林/舒巴坦、头孢曲松、头孢噻肟、头孢吡肟、亚胺培南、美罗培南、环丙沙星的耐药率均为100%。对分离自患者血液(26株)、呼吸道(6株)和静脉导管尖端(4株)的36株CRAB进行PFGE,结果表明主要为7个PFGE型(A~G),其中A克隆5株,B克隆2株,C克隆3株,D克隆4株,E克隆3株,F克隆8株,G克隆3株;其余8株菌为散发。该ICU分为Ⅰ、Ⅱ区,其中A、B、F克隆在两个病区间均存在。3例患者不同部位分离的CRAB为同一克隆,其中2例血液、下呼吸道、静脉导管尖端为同一克隆,另1例血液和下呼吸道为同一克隆。对其中6例患者下呼吸道分离的CRAB进行PFGE分型,3例同属D克隆。对12例血流感染患者静脉导管尖端进行培养,4例患者培养阳性,且为CRAB,分别与各自血液分离株为同一克隆。结论 ICU存在CRAB血流感染流行,患者间交叉传播是医院流行的主要方式。     

mCIM与eCIM在产碳青霉烯酶肠杆菌科细菌表型筛查中的价值

目的分析改良碳青霉烯灭活试验(mCIM)与乙二胺四乙酸碳青霉烯灭活试验(eCIM)对产碳青霉烯酶肠杆菌科细菌表型筛查的效能及应用价值。方法收集碳青霉烯类耐药肠杆菌科细菌(CRE)117株(实验组)、碳青霉烯类敏感肠杆菌科细菌50株(对照组)。分别采用改良Hodge试验(MHT)、mCIM和eCIM进行表型筛查,采用聚合酶链反应(PCR)检测常见碳青霉烯耐药基因,统计表型筛查试验结果与基因检测结果的一致性。结果以PCR检测出碳青霉烯酶基因为金标准,MHT筛查碳青霉烯酶的敏感性为87.0%、特异性为100.0%,mCIM筛查碳青霉烯酶的敏感性、特异性均为100.0%,eCIM筛查金属酶的敏感性为82.4%、特异性为100.0%。结论mCIM筛查碳青霉烯酶的敏感性比MHT高,mCIM与eCIM联合检测能更有效地筛查碳青霉烯酶,且可区分碳青霉烯酶类型,从而有效指导临床用药。