ABSTRACT
Carba-NP original report for blood cultures described the need of subculture and mechanical lysis before testing, reaching the turnaround time of approximately 4 hours for sample preparation. We tested 100 consecutive blood cultures positive for Gram-negative bacilli on the Gram stain from a large clinical laboratory. Bacterial pellets were prepared by centrifugation and submitted to Carba-NP and Blue-Carba tests and used further to prepare smears for Vitek MS. Results obtained with colonies grown on sheep blood agar using the same methodologies were used as the gold standard. Carbapenemase genes were confirmed by PCR and DNA sequencing. Vitek MS identified correctly 86% of the samples. Of note, 7% of the samples were incorrectly reported by the instrument as containing a single isolate. KPC-2 was the predominant carbapenemase detected. There was 100% concordance for both negative and positive results for Carba-NP. In contrast, for Blue-Carba the concordance for positive results was 92.8%, and 41% of strains negative for carbapenemases presented a yellowish color on control well turning the test non-interpretable. The turnaround time for sample preparation for preparing the pellet was 13 min, and no subculture or mechanical lysis is needed when detecting KPC production in Enterobacterales.
Subject(s)
Bacterial Proteins/metabolism , Blood Culture/methods , Enterobacteriaceae Infections/blood , Enterobacteriaceae/isolation & purification , Bacterial Proteins/genetics , Enterobacteriaceae/classification , Enterobacteriaceae/genetics , Enterobacteriaceae Infections/diagnosis , Enterobacteriaceae Infections/microbiology , Humans , Polymerase Chain Reaction , Sensitivity and Specificity , Workflow , beta-Lactamases/genetics , beta-Lactamases/metabolismSubject(s)
Anti-Bacterial Agents/pharmacology , Carbapenems/pharmacology , Drug Resistance, Bacterial , Klebsiella Infections/epidemiology , Klebsiella Infections/microbiology , Klebsiella pneumoniae/drug effects , Polymyxin B/pharmacology , Brazil/epidemiology , Humans , Klebsiella pneumoniae/classification , Klebsiella pneumoniae/genetics , Microbial Sensitivity Tests , Multilocus Sequence Typing , Population SurveillanceABSTRACT
In Enterobacteriaceae, the blaNDM genes have been found in many different genetic contexts, and a wide diversity of plasmid scaffolds bearing those genes has been found. In August 2013, we identified NDM-1-producing Escherichia coli and Enterobacter hormaechei strains from a single rectal swab sample from a patient hospitalized in Rio de Janeiro, Brazil, who had no history of travel abroad. Complete DNA sequencing using the Illumina platform and annotation of the two plasmids harboring the blaNDM-1 gene, one from each strain, showed that they belonged to incompatibility groups IncFIIK and IncX3 and harbored a novel transposon named Tn3000. Similar genetic structures have been identified among other isolates in Brazil but also on plasmids from other continents. Our findings suggest that the blaNDM-1 gene may be transmitted by Tn3000 in different parts of the world.
