Unbiased Species-Level Identification of Clinical Isolates of Coagulase-Negative Staphylococci: Does It Change the Perspective on Staphylococcus lugdunensis?

Abstract

Unbiased species-level identification of coagulase-negative staphylococci (CoNS) using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) identified Staphylococcus lugdunensis to be a more commonly isolated CoNS in our laboratory than previously observed. It has also highlighted the possibility of vertical transmission. C oagulase-negative staphylococci (CoNS) have been mostly considered insignificant contaminants when isolated from clinical samples. This, in turn, has led to a lack of universal agreement on the importance of identifying them to the species level (1, 2).The introduction of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) to routine clinical laboratories has made it feasible to rapidly and accurately identify clinical isolates without adding significant costs (3, 4).MALDI-TOF MS has been in routine diagnostic use at our laboratory since 2010. We identify all clinical isolates, irrespective of site or clinical details. In an attempt to assess the value of unbiased species-level identification of CoNS, we investigated the epidemiology and clinical correlates associated with the isolation of Staphylococcus lugdunensis, a relatively virulent CoNS that causes a spectrum of disease similar to that of Staphylococcus aureus (5).S. lugdunensis isolates were identified from the laboratory information management system (LIMS). Specimen request forms, electronic clinical records, and written clinical records were reviewed (for hospital and community samples). Only the isolates with a MALDI-TOF MS spectral score of Ն2 (which reflects high confidence in identification to the species level) were included. A total of 20,806 CoNS isolates were identified using MALDI-TOF MS in a 24-month period. Of those, 559 were identified as S. lugdunensis (Table 1), whereas 31 isolates were identified in the preceding 24 months using conventional techniques. Duplicate results from the same patient were removed (n ϭ 81). In total, 478 individual isolates were reviewed ( Table 2). The clinical data we collected included demographics, sample type, sample site, clinical symptoms, diagnosis, comorbidities, antibiotic usage, surgical procedures, and indwelling and prosthetic devices.A total of 121 isolates (25.3%) were from primary care. The male-to-female ratio was 0.84, and the median age was 42 years, with a calculated incidence of 30.5 cases per 100,000 persons in the local population. Twenty-two isolates (4.6%) were from neonates (Ͻ30 days old), with 10 isolated in the first 7 days of life. Of the 22 neonatal isolates, 5 were from sterile sites (blood, n ϭ 3; cerebrospinal fluid [CSF], n ϭ 1; and urine, n ϭ 1) and the rest were from swabs ( Table 3).The commonest infections were skin and soft tissue infections (SSTI), with a total of 237 episodes; of these, 99 (41.8%) were abscesses, and 79 (79.8%) required drainage. Abscesses were equally distributed between the upper and lower halves of the body. The commonest abscess sites were the axilla (n ...

Evaluation of Oxacillin and Cefoxitin Disk Diffusion and MIC Breakpoints Established by the Clinical and Laboratory Standards Institute for Detection of mecA -Mediated Oxacillin Resistance in Staphylococcus schleiferi

“…The widespread adoption of MALDI-TOF MS for bacterial identification has allowed clinical laboratories to better identify staphylococci to the species level (6,38). Rapid adoption of this technology, combined with an increasing immunocompromised population and close contact between humans and companion animals, has increased the number and diversity of clinically significant CoNS isolates identified (39). This increase leads to the issue of determining which methods are best for detecting mecA-mediated oxacillin resistance in CoNS, which has not been critically evaluated for many species.…”

Implementation of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry in Routine Clinical Laboratories Improves Identification of Coagulase-Negative Staphylococci and Reveals the Pathogenic Role of Staphylococcus lugdunensis

“…Based on a retrospective study, Elamin et al (29) showed that implementation of MALDI-TOF MS in 2010 for routine diagnostic use allowed the identification of 559 S. lugdunensis strains among 20,806 CoNS during a 24-month period, whereas 31 isolates were identified in the preceding 24 months using conventional methods (29). They also performed a clinical analysis for 478 individual isolates of S. lugdunensis and found no infectious diagnosis for 80 strains (16.7%), wound infection for 124 strains (25.9%), 99 abscesses (20.7%), and 12 significant bacteremias (2.5%), with 2 endocarditis cases (0.4%).…”

Staphylococcus aureus Aggregation and Coagulation Mechanisms, and Their Function in Host–Pathogen Interactions

“…For this reason these species have often been misidentified as S. aureus in the clinic, leading to an under appreciation of their contribution to disease (Argemi et al, 2015; Elamin et al, 2015). S. lugdunensis is particularly virulent among CoNS species, and can cause a range of invasive infections, including endocarditis, sepsis, abscesses and wound infections (Frank et al, 2008).…”