Comparison of Real-Time PCR and Conventional Biochemical Methods for Identification of Staphylococcus lugdunensis

Abstract

Staphylococcus lugdunensis is an aggressive, virulent member of the coagulase-negative staphylococci (CoNS) that is responsible for severe, rapidly progressive skin and soft tissue infections and native valve endocarditis. To facilitate prompt identification and appropriate therapy, we describe here a rapid and robust multiplex real-time PCR assay that is able to definitively distinguish S. lugdunensis from other staphylococci. Using melting curve analysis, the assay also identifies Staphylococcus aureus and CoNS other than S. lugdunensis and determines MecA-dependent resistance to methicillin (meticillin). When applied to a panel of well-characterized staphylococcal reference strains, as well as 165 clinical isolates previously identified by conventional methods, the assay was both sensitive and specific for S. lugdunensis, correctly identifying the reference strain and all 47 S. lugdunensis isolates without inappropriate amplification of other staphylococci. Furthermore, rapid biochemical identification using the WEE-TAB system to detect ornithine decarboxylase activity was found to be unsuitable as an alternative to PCR identification, displaying just 31% sensitivity and 77% specificity when tested on a subset (90 isolates) of the clinical strains. We therefore propose that this simple, accurate PCR approach will allow for the routine and timely identification of S. lugdunensis in the clinical microbiology laboratory.

Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications

“…As outlined above, β-lactam allergy evaluation should be conducted in every case in which vancomycin is considered for use because poorer outcomes related to vancomycin therapy for a variety of MSSA infections are well recognized. 147 Clindamycin has been associated with IE relapse and is not recommended. 157 For MSSA IE in patients with anaphylactoid-type β-lactam allergy who exhibit either a suboptimal response to vancomycin or vancomycin allergy, β-lactam desensitization should be considered as noted above.…”

Carriage niches and molecular epidemiology of Staphylococcus lugdunensis and methicillin-resistant S. lugdunensis among patients undergoing long-term renal replacement therapy

“…In the laboratory, CoNS may be misidentified. Pinsky et al reported that biochemical identification was only 31% sensitive and 77% specific for Staphylococcus lugdunensis when tested against PCR-based method (Pinsky et al, 2009). With increasing access to molecular and mass-spectrometry techniques, an increasing number of CoNS recovered from blood cultures and other sterile body sites are being correctly identified to the species level (Chen et al, 2013;Ho et al, 2014).…”

Is Staphylococcus lugdunensis Significant in Clinical Samples?

“…Regarding S. lugdunensis identification, despite its biochemical peculiarities, the reliability of these systems is too low and the accuracy of identification ranges from 70% to 90% depending on the system used and the performance of additional tests (7,8). In an effort to improve the identification rate, various molecular methods, particularly real-time PCR assays targeting some conserved genes such as gyrA, gap, sodA, and rpoB or 16S and 23S ribosomal DNA, have been successfully proposed (6,9,10). Identification by nucleic acid-based approaches appears to be a gold standard for S. lugdunensis, but the implementation of proteomic methods, particularly MALDI-TOF MS, in routine clinical laboratories has allowed a rapid, cost-effective, and reliable identification of bacteria, including staphylococci (2).…”