Mortality from bloodstream infections (BSIs) correlates with diagnostic delay and the use of inappropriate empirical treatment. Early PCR-based diagnosis could decrease inappropriate treatment, improving patient outcome. The aim of the present study was to assess the clinical utility of this molecular technology to diagnose BSIs. We assessed a new dual-priming oligonucleotide-based multiplex PCR assay, the Magicplex Sepsis Test (MST) (Seegene), along with blood culture (BC). A total of 267 patients from the intensive care unit and haematology and emergency departments were enrolled. Clinical data were also used by physicians to determine the likelihood of infection. Ninety-eight (37 %) specimens were positive: 29 (11 %) by both the MST and BC, 29 (11 %) by the MST only, and 40 (15 %) by BC only. The proportion of agreement between the two methods was 73 % (Cohen's k: 0.45; 0.28-0.6; indicating fair to moderate agreement). According to clinical assessment, 63 (64 %) positive specimens were considered BSIs: 23 (36 %) were positive by both the MST and BC, 22 (35 %) were positive only by BC, and 18 (29 %) were positive only by the MST. Thirty-eight (14 %) positive specimens by the MST and/ or BC were considered as contaminants. Of 101 specimens collected from patients receiving antibiotics, 20 (20 %) were positive by the MST and 32 (32 %) by BC. Sensitivity and specificity were 65 % and 92 %, respectively, for the MST and 71 % and 88 %, respectively for BC. We concluded that the MST shows a high specificity but changes in design are needed to increase bacteraemia detection. For viability in clinical laboratories, technical improvements are also required to further automate the process.

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Colistin resistance was detected in 53 of 10,011 Escherichia coli (0.5%) by prospective phenotypic testing of consecutive clinical isolates in a single hospital in Barcelona, Spain (2012-15). The mcr-1 gene was retrospectively identified by PCR and sequencing in 15 of 50 available isolates. Each isolate had a unique PFGE pattern except for two. This clonal diversity supports the hypothesis of horizontal dissemination of the mcr-1 gene in the local study population.Following the report on the plasmid-mediated colistin resistance gene mcr-1 in China [1], several authors have reported the detection of this gene in Escherichia coli isolates of animal origin [1][2][3][4][5]. Currently there have been few reports of detections in humans and these involve mainly multidrug-resistant (MDR) Gram-negative bacilli [3,[5][6][7]. To date, mcr-1 has been detected in at least five European countries in animals and humans, and often in association with recent travel to Asia [3,[5][6][7]. In this context, we describe mcr-1 detection in unselected clinical isolates of E. coli in Barcelona in samples from 2012 to 2015. Laboratory investigationA total of 10,011 E. coli were isolated between January 2012 and December 2015 from clinical specimens in our institution, a tertiary referral teaching hospital covering an area of 407,902 inhabitants in Barcelona, Spain. Only one isolate per patient was included.Isolates from colonisation screenings were not considered. Antibiotic susceptibility testing was performed by disc diffusion according to guidelines from the Clinical and Laboratory Standards Institute (CLSI) [8]. As a first approach to screen colistin resistance, a 10 µg disc of colistin was used. Isolates displaying an inhibition zone ≤ 12 mm (n = 61) were selected for further testing of minimal inhibitory concentration (MIC) by gradient diffusion (Etest, bioMérieux, France). Both diffusion methods were performed on Mueller Hinton agar (bioMérieux, France). MIC results of colistin were interpreted following the EUCAST breakpoints for Enterobacteriaceae [9]. Resistance to colistin was detected in 53 E. coli isolates (0.5%). Of these, 40 were isolated from urine specimens, eight from blood cultures and the remaining five from other clinical specimens. The average age of the patients with infections caused by colistin-resistant E. coli was 70.9 years (range: 6-99 years). The male:female ratio was 1:2.By amplification and Sanger sequencing, we searched for the presence of the mcr-1 gene in our collection of colistin-resistant E. coli isolates (only 50 isolates were available). The amplification of mcr-1 was performed as described by Liu et al. [1]. This gene was detected in 15 isolates; the amplified fragments had 100% sequence homology with the previously described mcr-1 [1].The patients' average age was 62 years (range: 6-97), eight of them were male and seven were female. Patients were not epidemiologically linked (Table). One patient was referred from a nursing home, and nine had had at least one hospital admission during the previo...

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