ABSTRACT
High accuracy of direct from positive blood culture molecular panels is imperative, particularly for the detection of resistance determinants as it allows for antimicrobial optimization prior to conventional susceptibility testing. In this study, we provide extensive data since implementation of the Verigene Gram-positive blood culture panel (BC-GP) in 2013. Within 5 years, 1636 blood culture bottles positive for a Gram-positive organism were tested on the BC-GP panel. The BC-GP panel identified 1520 Gram-positive organisms in 1636 (92.9%) blood cultures tested. For positive blood cultures, we observed 96.4% (806/834) concordance to the species level. Compared with conventional antimicrobial susceptibility testing, the positive percent agreement (PPA) of methicillin-resistant SA (MRSA) (50) and methicillin-resistant SE (MRSE) (365) was 100%. The mecA gene was detected in two methicillin-susceptible Staphylococcus aureus (MSSA) and one methicillin-susceptible S. epidermidis (MSSE) with a negative percent agreement (NPA) of 99.1% (221/223) and 99.2% (120/121), respectively. The PPA and NPA for vancomycin-resistant Enterococcus faecium (VRE) was 100%. The BC-GP panel demonstrated excellent performance and clinicians can confidently de-escalate antimicrobial therapy in the absence of mecA and vanA/B gene.
Subject(s)
Bacteremia , Blood Culture , Cross Infection , Gram-Positive Bacteria/genetics , Gram-Positive Bacterial Infections/diagnosis , Gram-Positive Bacterial Infections/microbiology , Hospitals, Pediatric , Bacteriological Techniques , Drug Resistance, Bacterial , Genes, Bacterial , Gram-Positive Bacteria/drug effects , Humans , Molecular Diagnostic Techniques , Retrospective StudiesABSTRACT
Group A Streptococcus (GAS) pharyngitis is a very common condition causing significant morbidity in children. Accurate diagnosis followed by appropriate antimicrobial therapy is recommended to prevent postinfectious sequelae. Diagnosis of GAS pharyngitis by a rapid antigen detection test (RADT) or culture in the absence of discriminating clinical findings remains challenging. Validation of new sensitive rapid diagnostic tests is therefore a priority. The performance of a loop-mediated isothermal amplification (LAMP) assay (illumigene assay) for the diagnosis of GAS pharyngitis was compared with that of a RADT and standard culture in 361 pediatric throat swab samples. Discrepant results were resolved using an alternate molecular assay. Test results were correlated with clinical presentations in patients positive by either method. The closest estimate of the true prevalence of GAS pharyngitis was 19.7% (71/361 samples). The illumigene assay alone detected 70/71 GAS-positive samples; RADT and culture detected 35/71 and 55/71 samples, respectively. RADT followed by culture confirmation of RADT-negative specimens detected 58/71 cases. The illumigene assay increased identification among children eligible for testing by American College of Physicians (ACP)/American Academy of Family Physicians (AAFP) criteria from 31 to 39 positive cases, five of which were false positives. Analysis of clinical data in GAS-positive patients indicated that a significantly greater proportion of children with McIsaac scores of ≥ 4 tested positive by the illumigene assay versus RADT and culture. Overall, the illumigene assay was much more sensitive and was similarly specific for GAS detection, compared to culture alone, RADT alone, or the ACP/AAFP RADT/culture algorithm. Combining high sensitivity with rapidly available results, the illumigene GAS assay is an appropriate alternative to culture for the laboratory diagnosis of GAS pharyngitis in patients for whom testing is clinically indicated.
Subject(s)
Molecular Diagnostic Techniques/methods , Nucleic Acid Amplification Techniques/methods , Pharyngitis/diagnosis , Pharyngitis/microbiology , Streptococcal Infections/diagnosis , Streptococcal Infections/microbiology , Streptococcus pyogenes/isolation & purification , Adolescent , Bacteriological Techniques/methods , Child , Child, Preschool , Female , Humans , Immunoassay/methods , Infant , Male , Sensitivity and Specificity , Streptococcus pyogenes/geneticsABSTRACT
The performance characteristics of the Verigene Gram-positive blood culture (BC-GP) assay were evaluated in pediatric patients. Concordance of the BC-GP assay was 95.8%, with significant decreases in turnaround time for identification and resistance detection. BC-GP is highly accurate and can be integrated into the routine workflow of the microbiology laboratory.
