Genotypic diversity of coagulase-negative staphylococci causing endocarditis: a global perspective

Infective Endocarditis Caused by Staphylococcus lugdunensis

Staphylococcus lugdunensis, a minor species of coagulase-negative staphylococci, has attracted attention because of its formidable pathogenicity. We present a case of infective endocarditis (IE) caused by S. lugdunensis in a 72-year-old woman with a history of breast cancer and metastases who presented with fever. Two of two blood culture bottles were positive for gram-positive cocci. Transesophageal echocardiography revealed vegetation attached to the right cusp of the aortic valve and an abscess in the annulus, which was less evident on transthoracic echocardiography. This case underscores the importance of considering S. lugdunensis as a potential cause of IE.

From Obscurity To Spotlight: Staphylococcus lugdunensis-Induced Infective Endocarditis, a Profound Case Unraveling

Infective endocarditis (IE) represents a grave infection characterized by endocardial inflammation and valve impairment due to diverse pathogens. Staphylococcus lugdunensis, a coagulase-negative organism, has garnered increasing recognition as a significant etiological agent of IE. This bacterium is renowned for its aggressive tissue infections encompassing bone and joint, bloodstream, and IE sites. Particularly noteworthy is the rapid devastation and abscess formation it induces on heart valves, resulting in elevated mortality rates. The pathogen's affinity for von Willebrand factor facilitates its attachment to cardiac valves and blood vessels, thereby exacerbating its virulence. This abstract provides a comprehensive overview of S. lugdunensis-triggered IE. We present a compelling case involving a 66-year-old female afflicted by IE attributed to this microorganism, illuminating the clinical manifestations and challenges linked to the ailment. Moreover, we scrutinize previously reported instances of S. lugdunensis-related IE spanning from 1993 to 2022, accentuating the escalating importance of this pathogen in disease causality. The deleterious consequences of S. lugdunensis-induced IE emanate from its distinctive clinical attributes, necessitating tailored diagnostic strategies and treatment considerations. Given the gravity and swift progression of the infection, healthcare professionals play a pivotal role in administering timely and efficacious management for afflicted patients. Further research is imperative to enhance diagnostic modalities and explore therapeutic approaches aimed at effectively combating this formidable and life-threatening infection.

Increasing clinical impact and microbiological difficulties in diagnosing coagulase-negative staphylococci in infective endocarditis - a review starting from a series of cases

Coagulase-negative staphylococci (CoNS) are an emergent aetiology of infective endocarditis (IE) on native valves in previously healthy individuals, its presence is associated with prosthetic valves or with other cardiac implants. The identification of CoNS in cultures was customarily seen as contamination, but more recent epidemiological studies have revealed an increasing number of causative and virulent new CoNS species. Starting from two clinical cases of community-acquired CoNS IE on native valves, the review debates the difficulties in identifying CoNS as the causal pathogens, comprising differentiation of contamination from infection in IE, alongside the challenges raised by antibiotic resistance. Even if the risk of CoNS IE is more increased in subjects with prosthetic materials or other foreign devices and immunodeficiencies, native valve infections with these staphylococci are increasing and should be considered important pathogens in IE. Despite the lack of sensitive and specific tools to correctly differentiate contamination from infection in CoNS endocarditis, a comprehensive evaluation with clinical and paraclinical data accurately succeeds in establishing the diagnosis. The genetic profile of CoNS predisposes to antibiotic multi-resistance, making the treatment of IE challenging; the rapid identification of antibiotic susceptibility is essential to prescribe the appropriate therapy and improve outcomes.

Underrecognized pathogen; Staphylococcus warneri ‐associated native mitral valve endocarditis in an immunocompetent host: A case report and literature review

Staphylococcus warneri‐related endocarditis is rarely reported, raising diagnostic challenges and is often associated with considerable morbidity and mortality. We describe a case of native valve endocarditis caused by S. warneri and complicated by a valve perforation in an immunocompetent patient to raise awareness of this emerging organism.

Native tricuspid valve infective endocarditis with Staphylococcus lugdunesis: An unusual complication post spinal epidural injection - Case report and literature review

Infective Endocarditis (IE) is a very rare complication following spinal epidural injection and requires high index of suspicion for early diagnosis and effective management.

Staphylococcus Lugdunesis is a coagulase negative staphylococcus (CoNS) that, unlike other CoNS, may result in aggressive form of native valve infective endocarditis (IE) mimicking IE caused by S aureus. Surgical intervention is usually needed to control infection in most cases of S. Lugdunesis IE.

Herein, we report a case of young lady with congenital Gerbode defect who developed tricuspid native valve IE with S. Lugdunesis secondary to spondylodiscitis post lumbar epidural injection that was performed for disk prolapse. She required urgent surgical intervention and had an excellent outcome.

Virulence Factors in Coagulase-Negative Staphylococci

Coagulase-negative staphylococci (CoNS) have emerged as major pathogens in healthcare-associated facilities, being S. epidermidis, S. haemolyticus and, more recently, S. lugdunensis, the most clinically relevant species. Despite being less virulent than the well-studied pathogen S. aureus, the number of CoNS strains sequenced is constantly increasing and, with that, the number of virulence factors identified in those strains. In this regard, biofilm formation is considered the most important. Besides virulence factors, the presence of several antibiotic-resistance genes identified in CoNS is worrisome and makes treatment very challenging. In this review, we analyzed the different aspects involved in CoNS virulence and their impact on health and food.

The Nasal Carriage of Coagulase-Negative Staphylococci Among Animals and Its Public Health Implication

Background: The research scope toward nasal colonization of coagulase-negative staphylococci (CoNS) in animals is largely ignored for many years. Therefore, this study was conducted to investigate the nasal carriage of CoNS among different animals and its public health implication. Materials and Methods: Nasal swabs were gathered from 152 animals (36 cats, 31 dogs, 29 sheep, 32 goats, and 24 cattle). These samples were subjected for isolation and identification of CoNS by conventional bacteriological methods, then molecular confirmation was carried out using Staphylococcus genus-specific 16S rRNA PCR. All CoNS isolates were screened for the presence of antibiotic resistance (mecA and blaZ) and virulence (lukS/F-PV and tsst-1) genes. Moreover, strains carrying resistance and/or virulence genes were identified to species level by 16S rRNA gene sequencing approach. Results: CoNS were identified in 14.5% (22/152) of the examined animals, whereas the prevalence rates among different animals were 27.8%, 3.2%, 8.3%, 10.3%, and 18.8% for cats, dogs, cattle, sheep, and goats, respectively. Of all isolates, two strains (Staphylococcus epidermidis and Staphylococcus warneri) harbored mecA gene, which carried on staphylococcal cassette chromosome mec type I in S. epidermidis and type V in S. warneri, while blaZ gene has been found in one strain (Staphylococcus felis). Importantly, two isolates (S. epidermidis and S. felis) had tsst-1 gene but all of CoNS isolates were negative for Panton-Valentine leukocidin gene. The phylogenetic analysis of the obtained sequences of CoNS of the current study revealed high similarity to those of serious human clinical cases to underscore the public health significance of such isolates. Conclusion: The nasal carriage of antibiotic-resistant and toxigenic CoNS among different animals highlights the potential zoonotic link with great public health implication.

An unusual case of Staphylococcus pasteuri osteomyelitis

Staphylococcus pasteuri is a gram-positive organism found in food products as well as naturally occurring in air and on surfaces. We present the first known case of Staphylococcus pasteuri osteomyelitis caused by machine injection injury. The patient was treated with emergent surgical debridement as well as doxycycline for a soft tissue infection. Despite targeted therapy, the infection progressed to osteomyelitis and was treated successfully with additional surgical debridement and trimethoprim-sulfamethoxazole. There is sparse information on both infections and treatment of Staphylococcus pasteuri. We present our case report as well as a review of the literature on the epidemiology, susceptibility and treatment recommendations for Staphylococcus pasteuri infections.

Staphylococcus lugdunensis: Review of Epidemiology, Complications, and Treatment

Staphylococcus lugdunensis is a species of coagulase-negative staphylococci (CNS) that induces a variety of infectious diseases, including skin and soft tissue infection (SSTI), infective endocarditis (IE), and bone and PJI. This review article underscores the important points in the literature about S. lugdunensis infections, including its epidemiology, diagnosis, and treatment, as well as specific types of infections it can cause. Anatomical and age-related distributions of S. lugdunensis SSTIs have been noted, though they most commonly occur as abscesses. S. lugdunensis can also manifest as an aggressive form of IE presenting with valve destruction and abscess formation, frequently requiring surgery and with a high mortality rate. Bone and joint infections caused by S. lugdunensis are also more invasive than infections by other species of CNS. The clinical presentation of S. lugdunensis infection in SSTI, IE, and bone/joint infection is frequently more similar to that of S. aureus infection than that of other CNS infections, necessitating species-level differentiation of CNS for proper diagnosis. Though historically, this depended upon biochemical tests that were neither routine nor reliable, the implementation of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) in clinical laboratories has made identification of CNS species such as S. lugdunensis more practical. Imaging modalities, especially the fluorodeoxyglucose (FDG) with positron emission tomography (PET), are another important emerging trend in the diagnosis of infectious diseases such as S. lugdunensis infection. S. lugdunensis remains highly susceptible to a wide gamut of antibacterial therapies, which is uncharacteristic of other CNS. Infections can usually be treated by antibiotics traditionally used for CNS such as oxacillin. The breakpoints for S. lugdunensis are higher than those of other CNS and similar to S. aureus breakpoints. In the case of aggressive IE or bone/joint infection by S. lugdunensis, it is recommended to treat with a β-lactam agent. Further study is needed to understand the diversity, virulence, and population structure of this species, as well as its role in other infections, such as urinary tract infections (UTIs), respiratory infections, peritonitis, and bacteremia. 

Evaluation of two rapid molecular test systems to establish an algorithm for fast identification of bacterial pathogens from positive blood cultures

Fast identification of pathogens directly from positive blood cultures is of highest importance to supply an adequate therapy of bloodstream infections (BSI). There are several platforms providing molecular-based identification, detection of antimicrobial resistance genes, or even a full antimicrobial susceptibility testing (AST). Two of such test systems allowing rapid diagnostics were assessed in this study: The Biofire FilmArray® and the Genmark ePlex®, both fully automated test system with a minimum of hands-on time. Overall 137 BSI episodes were included in our study and compared to conventional culture–based reference methods. The FilmArray® is using one catridge including a panel for the most common bacterial and fungal BSI pathogens as well as selected resistance markers. The ePlex® offers three different cartridges for detection of Gram-positives, Gram-negatives, and fungi resulting in a broader panel including also rare pathogens, putative contaminants, and more genetic resistance markers. The FilmArray® and ePlex® were evaluated for all 137 BSI episodes with FilmArray® detecting 119 and ePlex® detecting 128 of these. For targets on the respective panel of the system, the FilmArray® generated a sensitivity of 98.9% with 100% specificity on Gram-positive isolates. The ePlex® system generated a sensitivity of 94.7% and a specificity of 90.7% on Gram-positive isolates. In each case, the two systems performed with 100% sensitivity and specificity for the detection of Gram-negative specimens covered by each panel. In summary, both evaluated test systems showed a satisfying overall performance for fast pathogen identification and are beneficial tools for accelerating blood culture diagnostics of sepsis patients.

Staphylococcus pasteuri infective endocarditis: A case report

Staphylococcus pasteuri is a coagulase negative bacterium which although formally described in 1993, has only recently become possible to reliably speciate in diagnostic microbiology laboratories. S. pasteuri remains an extremely infrequent cause of human infection to date, namely bacteremia in an individual suffering acute myeloid leukemia, catheter-associated urinary tract infection in a patient receiving chemotherapy and endocarditis within a case series without specific clinical information. As such, our report provides the first detailed account of Staphylococcus pasteuri infective endocarditis entailing a subacute community-onset infection involving native aortic and mitral valves, multiple systemic emboli, and ultimately cardiothoracic surgery.

Antimicrobial Activity of Exebacase (Lysin CF-301) against the Most Common Causes of Infective Endocarditis

Exebacase, a recombinantly produced lysin (cell wall hydrolase), and comparator antibiotics were tested by the broth microdilution method against strain sets of Staphylococcus and Streptococcus spp., which are the most common causes of infective endocarditis in humans. Exebacase was active against all Staphylococcus spp. tested, including S. aureus and coagulase-negative staphylococci (MIC_50/90, 0.5/1 μg/ml). Activity against Streptococcus spp. was variable, with S. pyogenes, S. agalactiae, and S. dysgalactiae (MIC_50/90, 1/2 μg/ml) among the most susceptible.

Bacterial contamination of human skin allografts and antimicrobial resistance: a skin bank problem

Background

Bacterial contamination remains the major problem in skin banks, even after antimicrobial treatment, and results in high rates of tissue discarding. This study aimed to analyze bacterial contamination in 32 human skin allografts from the skin bank of Dr. Roberto Corrêa Chem from the Hospital Complex Santa Casa de Misericórdia de Porto Alegre. These samples were already discarded due to microbial contamination. The identification of the bacteria isolated from skin allografts was performed by matrix assisted laser desorption ionization–time of flight. The antimicrobial susceptibility of the isolates to six different classes of antimicrobials was determined using the disk-diffusion agar method, and the evaluation of the inhibitory potential was determined by the minimal inhibitory concentration (50/90) of antimicrobials already used in the skin bank and those that most isolates were susceptible to.

Results

A total of 21 (65.6%) skin samples were contaminated with Gram-positive bacteria: 1 (4.7%) with Paenibacillus sp., 12 (61.9%) with Bacillus sp., 6 (28.5%) with Staphylococcus sp., and 2 (9.5%) with Bacillus sp. and Staphylococcus sp. Several resistance profiles, including multiresistance, were found among the isolates. Most of the isolates were susceptible to at least one of the antimicrobials used in the skin bank. All isolates were susceptible to amikacin, gentamicin, and tetracycline, which demonstrated the best inhibitory activities against the isolates and were considered as potential candidates for new antimicrobial treatments.

Conclusions

Bacillus, Paenibacillus, and Staphylococcus were isolated from the skin allografts, thus demonstrating the predominance of Gram-positive bacteria contamination. Other factors not related to the resistance phenotype may also be involved in the persistence of bacterial isolates in the skin allografts after antibiotic treatment. Gentamicin, amikacin, and tetracycline can be considered as an option for a more effective treatment cocktail.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1261-1) contains supplementary material, which is available to authorized users.

Is Staphylococcus lugdunensis Significant in Clinical Samples?

The implication of coagulase-negative staphylococci in human diseases is a major issue, particularly in hospital settings wherein these species often act as opportunistic pathogens. In addition, some coagulase-negative staphylococci such as S. lugdunensis have emerged as pathogenic bacteria, implicated in severe infections, particularly, osteoarticular infections, foreign-body-associated infections, bacteremia, and endocarditis. In vitro studies have shown the presence of several putative virulence factors such as adhesion factors, biofilm production, and proteolytic factors that might explain clinical manifestations. Taken together, the clinical and microbiological data might change the way clinicians and microbiologists look at S. lugdunensis in clinical samples.

Extreme diversity and multiple SCCmec elements in coagulase-negative Staphylococcus found in the Clinic and Community in Beijing, China

Background

Coagulase-negative staphylococci (CoNS) are recognized as a large reservoir of staphylococcal cassette chromosome mec (SCCmec) harboured by Staphylococcus aureus. However, data of SCCmec in CoNS are relatively absent particularly in China.

Methods

Seventy-eight CoNS clinical and 47 community isolates were collected in Beijing. PCR was performed to classify SCCmec types. Under oxacillin treatment, quantitative real-time reverse transcription PCR (qRT-PCR) was performed to compare mecA mRNA levels and mRNA half-life between isolates with single SCCmec element and those with multiple one. Their growth curves were analysed. Their bacterial cell wall integrity was also compared by performing a Gram stain. All ccr complex segments were sequenced and obtained ccr segments were analysed by phylogenetic analyses.

Results

All 78 clinical isolates had mecA segments compared with 38% in community isolates (total 47). Only 29% clinical isolates and 33% community isolates (among mecA positive isolates) harboured a single previously identified SCCmec type; notably, 17% clinical isolates and 28% community isolates had multiple SCCmec types. Further studies indicated that isolates with multiple SCCmec elements had more stable mecA mRNA expression compared with isolates with single SCCmec elements. CoNS with multiple SCCmec elements demonstrated superior cell wall integrity. Interestingly, phylogenetic analyses of obtained 70 ccr segments indicated that horizontal gene transfer of the ccr complex might exist among various species of clinical CoNS, community CoNS and S. aureus.

Conclusions

CoNS recovered from patients carried extremely diverse but distinctive SCCmec elements compared with isolates from the community. More attention should be given to CoNS with multiple SCCmec not only because they had superior cell wall integrity, but also because CoNS and S. aureus might acquire multiple SCCmec through the ccr complex.

Electronic supplementary material

The online version of this article (doi:10.1186/s12941-017-0231-z) contains supplementary material, which is available to authorized users.

Staphylococcal species heterogeneity in the nasal microbiome following antibiotic prophylaxis revealed by tuf gene deep sequencing

BACKGROUND

Staphylococci are a major constituent of the nasal microbiome and a frequent cause of hospital-acquired infection. Antibiotic surgical prophylaxis is administered prior to surgery to reduce a patient's risk of postoperative infection. The impact of surgical prophylaxis on the nasal staphylococcal microbiome is largely unknown. Here, we report the species present in the nasal staphylococcal microbiome and the impact of surgical prophylaxis revealed by a novel culture independent technique. Daily nasal samples from 18 hospitalised patients, six of whom received no antibiotics and 12 of whom received antibiotic surgical prophylaxis (flucloxacillin and gentamicin or teicoplanin +/- gentamicin), were analysed by tuf gene fragment amplicon sequencing.

RESULTS

On admission to hospital, the species diversity of the nasal staphylococcal microbiome varied from patient to patient ranging from 4 to 10 species. Administration of surgical prophylaxis did not substantially alter the diversity of the staphylococcal species present in the nose; however, surgical prophylaxis did impact on the relative abundance of the staphylococcal species present. The dominant staphylococcal species present in all patients on admission was Staphylococcus epidermidis, and antibiotic administration resulted in an increase in species relative abundance. Following surgical prophylaxis, a reduction in the abundance of Staphylococcus aureus was observed in carriers, but not a complete eradication.

CONCLUSIONS

Utilising the tuf gene fragment has enabled a detailed study of the staphylococcal microbiome in the nose and highlights that although there is no change in the heterogeneity of species present, there are changes in abundance. The sensitivity of the methodology has revealed that the abundance of S. aureus is reduced to a low level by surgical prophylaxis and therefore reduces the potential risk of infection following surgery but also highlights that S. aureus does persist.

A Novel MSCRAMM Subfamily in Coagulase Negative Staphylococcal Species

Coagulase negative staphylococci (CoNS) are important opportunistic pathogens. Staphylococcus epidermidis, a coagulase negative staphylococcus, is the third leading cause of nosocomial infections in the US. Surface proteins like Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs) are major virulence factors of pathogenic gram positive bacteria. Here, we identified a new chimeric protein in S. epidermidis, that we call SesJ. SesJ represents a prototype of a new subfamily of MSCRAMMs. Structural predictions show that SesJ has structural features characteristic of a MSCRAMM along with a N-terminal repeat region and an aspartic acid containing C-terminal repeat region, features that have not been previously observed in staphylococcal MSCRAMMs but have been found in other surface proteins from gram positive bacteria. We identified and analyzed structural homologs of SesJ in three other CoNS. These homologs of SesJ have an identical structural organization but varying sequence identities within the domains. Using flow cytometry, we also show that SesJ is expressed constitutively on the surface of a representative S. epidermidis strain, from early exponential to stationary growth phase. Thus, SesJ is positioned to interact with protein targets in the environment and plays a role in S. epidermidis virulence.

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

The use of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for staphylococcal identification is now considered routine in laboratories compared with the conventional phenotypical methods previously used. We verified its microbiological relevance for identifying the main species of coagulase-negative staphylococci (CoNS) by randomly selecting 50 isolates. From 1 January 2007 to 31 August 2008, 12,479 staphylococci were isolated with phenotypic methods, of which 4,594 were identified as Staphylococcus aureus and 7,885 were coagulase negative staphylococci. Using MALDI-TOF MS from 1 January 2011 to 31 August 2012, 14,913 staphylococci were identified, with 5,066 as S. aureus and 9,847 as CoNS. MALDI-TOF MS allowed the identification of approximately 85% of the CoNS strains, whereas only 14% of the CoNS strains were identified to the species level with phenotypic methods because they were often considered contaminants. Furthermore, the use of MALDI-TOF MS revealed the occurrence of recently characterized Staphylococcus species, such as S. pettenkoferi, S. condimenti, and S. piscifermentans. Microbiological relevance analysis further revealed that some species displayed a high rate of microbiological significance, i.e., 40% of the S. lugdunensis strains included in the analysis were associated with infection risk. This retrospective microbiological study confirms the role of MALDI-TOF MS in clinical settings for the identification of staphylococci with clinical consequences. The species distribution reveals the occurrence of the recently identified species S. pettenkoferi and putative virulent species, including S. lugdunensis.

Coagulase-negative staphylococci

The definition of the heterogeneous group of coagulase-negative staphylococci (CoNS) is still based on diagnostic procedures that fulfill the clinical need to differentiate between Staphylococcus aureus and those staphylococci classified historically as being less or nonpathogenic. Due to patient- and procedure-related changes, CoNS now represent one of the major nosocomial pathogens, with S. epidermidis and S. haemolyticus being the most significant species. They account substantially for foreign body-related infections and infections in preterm newborns. While S. saprophyticus has been associated with acute urethritis, S. lugdunensis has a unique status, in some aspects resembling S. aureus in causing infectious endocarditis. In addition to CoNS found as food-associated saprophytes, many other CoNS species colonize the skin and mucous membranes of humans and animals and are less frequently involved in clinically manifested infections. This blurred gradation in terms of pathogenicity is reflected by species- and strain-specific virulence factors and the development of different host-defending strategies. Clearly, CoNS possess fewer virulence properties than S. aureus, with a respectively different disease spectrum. In this regard, host susceptibility is much more important. Therapeutically, CoNS are challenging due to the large proportion of methicillin-resistant strains and increasing numbers of isolates with less susceptibility to glycopeptides.

Identification of endosymbionts in ticks by broad-range polymerase chain reaction and electrospray ionization mass spectrometry

Many organisms, such as insects, filarial nematodes, and ticks, contain heritable bacterial endosymbionts that are often closely related to transmissible tickborne pathogens. These intracellular bacteria are sometimes unique to the host species, presumably due to isolation and genetic drift. We used a polymerase chain reaction/electrospray ionization-mass spectrometry assay designed to detect a wide range of vectorborne microorganisms to characterize endosymbiont genetic signatures from Amblyomma americanum (L.), Amblyomma maculatum Koch, Dermacentor andersoni Stiles, Dermacentor occidentalis Marx, Dermacentor variabilis (Say), Ixodes scapularis Say, Ixodes pacificus Cooley & Kohls, Ixodes ricinus (L.), and Rhipicephalus sanguineus (Latreille) ticks collected at various sites and of different stages and both sexes. The assay combines the abilities to simultaneously detect pathogens and closely related endosymbionts and to identify tick species via characterization of their respective unique endosymbionts in a single test.

Molecular methods for pathogen and microbial community detection and characterization: current and potential application in diagnostic microbiology

Clinical microbiology laboratories worldwide have historically relied on phenotypic methods (i.e., culture and biochemical tests) for detection, identification and characterization of virulence traits (e.g., antibiotic resistance genes, toxins) of human pathogens. However, limitations to implementation of molecular methods for human infectious diseases testing are being rapidly overcome allowing for the clinical evaluation and implementation of diverse technologies with expanding diagnostic capabilities. The advantages and limitation of molecular techniques including real-time polymerase chain reaction, partial or whole genome sequencing, molecular typing, microarrays, broad-range PCR and multiplexing will be discussed. Finally, terminal restriction fragment length polymorphism (T-RFLP) and deep sequencing are introduced as technologies at the clinical interface with the potential to dramatically enhance our ability to diagnose infectious diseases and better define the epidemiology and microbial ecology of a wide range of complex infections.

Tuf gene sequence analysis has greater discriminatory power than 16S rRNA sequence analysis in identification of clinical isolates of coagulase-negative staphylococci

We compared and analyzed 16S rRNA and tuf gene sequences for 97 clinical isolates of coagulase-negative staphylococci (CNS) by use of the GenBank, MicroSeq, EzTaxon, and BIBI databases. Discordant results for definitive identification were observed and differed according to the different databases and target genes. Although higher percentages of sequence identity were obtained with GenBank and MicroSeq for 16S rRNA analysis, the BIBI and EzTaxon databases produced less ambiguous results. Greater discriminatory power and fewer multiple probable identifications were observed with tuf gene analysis than with 16S rRNA analysis. The most pertinent results for tuf gene analysis were obtained with the GenBank database when the cutoff values for the percentage of identity were adjusted to be greater than or equal to 98.0%, with >0.8% separation between species. Analysis of the tuf gene proved to be more discriminative for certain CNS species; further, this method exhibited better distinction in the identification of CNS clinical isolates.

Tuf gene sequence analysis has greater discriminatory power than 16S rRNA sequence analysis in identification of clinical isolates of coagulase-negative staphylococci

We compared and analyzed 16S rRNA and tuf gene sequences for 97 clinical isolates of coagulase-negative staphylococci (CNS) by use of the GenBank, MicroSeq, EzTaxon, and BIBI databases. Discordant results for definitive identification were observed and differed according to the different databases and target genes. Although higher percentages of sequence identity were obtained with GenBank and MicroSeq for 16S rRNA analysis, the BIBI and EzTaxon databases produced less ambiguous results. Greater discriminatory power and fewer multiple probable identifications were observed with tuf gene analysis than with 16S rRNA analysis. The most pertinent results for tuf gene analysis were obtained with the GenBank database when the cutoff values for the percentage of identity were adjusted to be greater than or equal to 98.0%, with >0.8% separation between species. Analysis of the tuf gene proved to be more discriminative for certain CNS species; further, this method exhibited better distinction in the identification of CNS clinical isolates.

Very late-onset lead-associated endocarditis

Lead-associated endocarditis is a serious complication due to device implantation. The present article reports on a case involving a 57-year-old man with microbiologically and pathologically confirmed lead-associated endocarditis caused by Staphylococcus capitis. Transesophageal echocardiography is essential for diagnosis, and treatment usually requires appropriate antibiotics and removal of the lead.

Quantitative reverse transcription-PCR assay for the rapid detection of methicillin-resistant Staphylococcus aureus

AIM

To evaluate a new quantitative reverse transcription-PCR (qRT-PCR) assay for the rapid detection of methicillin-resistant Staphylococcus aureus (MRSA).

METHODS AND RESULTS

Primers for Staphylococcus-specific regions of 16S rRNA gene, spa gene and mecA gene were newly designed. RNAs extracted from broth-cultured strains were tested by qRT-PCR targeting each primer, and the bacterial counts obtained correlated well with those counted by the plating method with detection limits of 10(0), 10(1) and 10(2) CFU. The qRT-PCR assay targeting the 16S rRNA was 6430-fold or more sensitive than qPCR assay. All Staph. aureus strains tested were detected and none of the other Staphylococcus species and genus strains tested cross-reacted with the assay targeting the spa gene. All MRSAs tested were detected by the assay targeting the mecA gene. Clinical samples, faecal material and bronchial washout solutions were tested by our assay, and MRSAs were detected with a high sensitivity within 6 h.

CONCLUSION

Our qRT-PCR assay targeting three new primers to the target genes is a rapid and sensitive tool for the detection of MRSA directly from clinical samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

Because of its sensitivity and rapidity, our qRT-PCR assay is considered to be a valuable tool for clinical management.

Analysis of the genotype and virulence of Staphylococcus epidermidis isolates from patients with infective endocarditis

Staphylococcus epidermidis is one of the most common causes of infections of prosthetic heart valves (prosthetic valve endocarditis [PVE]) and an increasingly common cause of infections of native heart valves (native valve endocarditis [NVE]). While S. epidermidis typically causes indolent infections of prosthetic devices, including prosthetic valves and intravascular catheters, S. epidermidis NVE is a virulent infection associated with valve destruction and high mortality. In order to see if the differences in the course of infection were due to characteristics of the infecting organisms, we examined 31 S. epidermidis NVE and 65 PVE isolates, as well as 21 isolates from blood cultures (representing bloodstream infections [BSI]) and 28 isolates from nasal specimens or cultures considered to indicate skin carriage. Multilocus sequence typing showed both NVE and PVE isolates to have more unique sequence types (types not shared by the other groups; 74 and 71%, respectively) than either BSI isolates (10%) or skin isolates (42%). Thirty NVE, 16 PVE, and a total of 9 of the nasal, skin, and BSI isolates were tested for virulence in Caenorhabditis elegans. Twenty-one (70%) of the 30 NVE isolates killed at least 50% of the worms by day 5, compared to 1 (6%) of 16 PVE isolates and 1 (11%) of 9 nasal, skin, or BSI isolates. In addition, the C. elegans survival rate as assessed by log rank analyses of Kaplan-Meier survival curves was significantly lower for NVE isolates than for each other group of isolates (P < 0.0001). There was no correlation between the production of poly-beta(1-6)-N-acetylglucosamine exopolysaccharide and virulence in worms. This study is the first analysis suggesting that S. epidermidis isolates from patients with NVE constitute a more virulent subset within this species.