ABSTRACT
OBJECTIVE: To evaluate the sensitivity and specificity of influenza virus detection by two commercial reverse transcriptase PCR methods compared with a reference real-time PCR. METHODS: 122 clinical specimens were tested on Xpert(®) Flu and RealStar(®) Influenza Screen & Type. A reference real-time RT-PCR, at a specialist laboratory was chosen as the gold standard for comparison. RESULTS: RealStar(®) Influenza Screen & Type had higher sensitivity for influenza A and influenza B respectively (92.3% and 88.2%) when compared to Xpert(®) Flu (78.8% and 76.5%). Both tests had excellent specificity. CONCLUSIONS: The simplicity and speed of the Xpert(®) Flu system could allow it to be used in the near-patient setting; however in circumstances where excluding a diagnosis of influenza may be critical, negative specimens may need to be repeated using a more sensitive assay.
Subject(s)
Influenza, Human/diagnosis , Molecular Diagnostic Techniques/methods , Orthomyxoviridae/isolation & purification , Reverse Transcriptase Polymerase Chain Reaction/methods , Virology/methods , Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Female , Humans , Infant , Influenza, Human/virology , Male , Middle Aged , Orthomyxoviridae/genetics , Real-Time Polymerase Chain Reaction/methods , Sensitivity and Specificity , Young AdultABSTRACT
We evaluated toxigenic Clostridium difficile detection by a lateral flow assay for antigen and toxin, an enzyme immunoassay, and two commercial PCR methods. Compared to the cell cytotoxicity neutralization assay and toxigenic culture, both toxin detection methods lacked sensitivity. PCR following combined antigen and toxin detection provided the most useful diagnostic information.
Subject(s)
Clinical Laboratory Techniques/methods , Clostridioides difficile/isolation & purification , Diagnostic Tests, Routine/methods , Enterocolitis, Pseudomembranous/diagnosis , Immunoenzyme Techniques/methods , Polymerase Chain Reaction/methods , Aged , Aged, 80 and over , Antigens, Bacterial/analysis , Bacterial Toxins/analysis , Cell Culture Techniques/methods , Clostridioides difficile/chemistry , Clostridioides difficile/genetics , Humans , Neutralization Tests/methodsABSTRACT
OBJECTIVES: Conventional detection of extended-spectrum beta-lactamase (ESBL) producers in blood cultures usually requires overnight incubation. This could delay the prescribing of appropriate therapy. We evaluated whether the chromogenic cephalosporin HMRZ-86, which is hydrolysed by ESBLs, could be used for the rapid detection of ESBL producers directly in blood culture broths. METHODS: The HMRZ-86 test was first applied to broth cultures of isolates producing known beta-lactamases. A colour change indicating hydrolysis, which was inhibited by clavulanic acid, was taken as an indication of ESBL production. A similar method was used for testing blood culture supernatants and broth subcultures of blood cultures. RESULTS: The HMRZ-86 test detected all the ESBL producers among 83 clinical isolates and control strains. Only one false positive was seen. The usefulness of HMRZ-86 for the direct testing of blood culture broths was limited by the presence of lysed blood. However, by using a 2 h broth subculture of the blood culture broths, the HMRZ-86 test was able to detect all those blood cultures containing an ESBL producer. No false positive or negative tests occurred according to the results of our standard phenotypic tests. CONCLUSIONS: The HMRZ-86 test is a simple and rapid method that can be used for detecting ESBL producers in blood cultures.
Subject(s)
Anti-Bacterial Agents/metabolism , Blood/microbiology , Cephalosporins , Gram-Negative Bacteria/enzymology , beta-Lactamases/analysis , Clavulanic Acid/pharmacology , Color , Culture Media , Enzyme Inhibitors/pharmacology , False Positive Reactions , Gram-Negative Bacteria/drug effects , Gram-Negative Bacterial Infections/microbiology , Humans , Hydrolysis , beta-Lactamase Inhibitors , beta-Lactamases/biosynthesisSubject(s)
Bacterial Proteins/metabolism , Escherichia coli/isolation & purification , Klebsiella pneumoniae/isolation & purification , Microbial Sensitivity Tests/methods , beta-Lactam Resistance , beta-Lactamases/metabolism , Bacterial Proteins/antagonists & inhibitors , Bacterial Proteins/drug effects , Boronic Acids/pharmacology , Cefoxitin/pharmacology , Enzyme Inhibitors/pharmacology , Escherichia coli/drug effects , Escherichia coli/enzymology , Klebsiella pneumoniae/drug effects , Klebsiella pneumoniae/enzymology , Thiophenes/pharmacology , beta-Lactamase Inhibitors , beta-Lactamases/drug effectsABSTRACT
CTX-M-25 is a novel extended-spectrum beta-lactamase isolated from a single Canadian Escherichia coli isolate. Susceptibility testing demonstrated that this enzyme confers resistance to both cefotaxime and ceftazidime, but the level of resistance was reduced with the addition of beta-lactamase inhibitors. The bla(CTX-M-25) gene was detected on a 111-kb plasmid. It is a member of the CTX-M-8 group and has the closest amino acid identity (99%; three amino acid substitutions) with CTX-M-26. The bla(CTX-M-26) gene was detected on a 100-kb plasmid isolated from a Klebsiella pneumoniae strain from the United Kingdom, and plasmid profiling revealed that it showed some homology to the bla(CTX-M-25)-harboring plasmid. Both CTX-M genes were located downstream of ISEcp1, although the copy upstream of bla(CTX-M-25) was disrupted by IS50-A. Comparative kinetic studies of recombinant CTX-M-25 and CTX-M-26 enzymes showed that CTX-M-25 has a higher level of ceftazidime hydrolysis (kcat values, 33 and 0.005 s(-1) for CTX-M-25 and CTX-M-26, respectively).
