Comparative epidemiology of Staphylococcus epidermidis isolates from patients with catheter-related bacteremia and from healthy volunteers

Combined metagenomic- and culture-based approaches to investigate bacterial strain-level associations with medication-controlled mild-moderate atopic dermatitis

Background

The skin microbiome is disrupted in atopic dermatitis (AD). Existing research focuses on moderate to severe, unmedicated disease.

Objective

We sought to investigate metagenomic- and culture-based bacterial strain-level differences in mild, medicated AD and the effects these have on human keratinocytes (HKs).

Methods

Skin swabs from anterior forearms were collected from 20 pediatric participants (11 participants with AD sampled at lesional and nonlesional sites and 9 age- and sex-matched controls). Participants had primarily mild to moderate AD and maintained medication use. Samples were processed for microbial metagenomic sequencing and bacterial isolation. Isolates identified as Staphylococcus aureus were tested for enterotoxin production. HK cultures were treated with cell-free conditioned media from representative Staphylococcus species to measure barrier effects.

Results

Metagenomic sequencing identified significant differences in microbiome composition between AD and control groups. Differences were seen at the species and strain levels for Staphylococci, with S aureus found only in participants with AD and differences in Staphylococcus epidermidis strains between control and AD swabs. These strains showed differences in toxin gene presence, which was confirmed in vitro for S aureus enterotoxins. The strain from the participant with the most severe AD produced enterotoxin B levels more than 100-fold higher than the other strains (P < .001). Strains also displayed differential effects on HK metabolism and barrier function.

Conclusions

Strain-level differences in toxin genes from Staphylococcus strains may explain varying effects on HK, with S aureus and non-aureus strains negatively affecting viability and barrier function. These differences are likely important in AD pathogenesis.

Completed genome and emergence scenario of the multidrug-resistant nosocomial pathogen Staphylococcus epidermidis ST215

BACKGROUND

A multidrug-resistant lineage of Staphylococcus epidermidis named ST215 is a common cause of prosthetic joint infections and other deep surgical site infections in Northern Europe, but is not present elsewhere. The increasing resistance among S. epidermidis strains is a global concern. We used whole-genome sequencing to characterize ST215 from healthcare settings.

RESULTS

We completed the genome of a ST215 isolate from a Swedish hospital using short and long reads, resulting in a circular 2,676,787 bp chromosome and a 2,326 bp plasmid. The new ST215 genome was placed in phylogenetic context using 1,361 finished public S. epidermidis reference genomes. We generated 10 additional short-read ST215 genomes and 11 short-read genomes of ST2, which is another common multidrug-resistant lineage at the same hospital. We studied recombination's role in the evolution of ST2 and ST215, and found multiple recombination events averaging 30-50 kb. By comparing the results of antimicrobial susceptibility testing for 31 antimicrobial drugs with the genome content encoding antimicrobial resistance in the ST215 and ST2 isolates, we found highly similar resistance traits between the isolates, with 22 resistance genes being shared between all the ST215 and ST2 genomes. The ST215 genome contained 29 genes that were historically identified as virulence genes of S. epidermidis ST2. We established that in the nucleotide sequence stretches identified as recombination events, virulence genes were overrepresented in ST215, while antibiotic resistance genes were overrepresented in ST2.

CONCLUSIONS

This study features the extensive antibiotic resistance and virulence gene content in ST215 genomes. ST215 and ST2 lineages have similarly evolved, acquiring resistance and virulence through genomic recombination. The results highlight the threat of new multidrug-resistant S. epidermidis lineages emerging in healthcare settings.

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

Medical devices such as venous catheters (VCs) and urinary catheters (UCs) are widely used in the hospital setting. However, the implantation of these devices is often accompanied by complications. About 60 to 70% of nosocomial infections (NIs) are linked to biofilms. The main complication is the ability of microorganisms to adhere to surfaces and form biofilms which protect them and help them to persist in the host. Indeed, by crossing the skin barrier, the insertion of VC inevitably allows skin flora or accidental environmental contaminants to access the underlying tissues and cause fatal complications like bloodstream infections (BSIs). In fact, 80,000 central venous catheters-BSIs (CVC-BSIs)-mainly occur in intensive care units (ICUs) with a death rate of 12 to 25%. Similarly, catheter-associated urinary tract infections (CA-UTIs) are the most commonlyhospital-acquired infections (HAIs) worldwide.These infections represent up to 40% of NIs.In this review, we present a summary of biofilm formation steps. We provide an overview of two main and important infections in clinical settings linked to medical devices, namely the catheter-asociated bloodstream infections (CA-BSIs) and catheter-associated urinary tract infections (CA-UTIs), and highlight also the most multidrug resistant bacteria implicated in these infections. Furthermore, we draw attention toseveral useful prevention strategies, and advanced antimicrobial and antifouling approaches developed to reduce bacterial colonization on catheter surfaces and the incidence of the catheter-related infections.

A look at staphylococci from the one health perspective

Staphylococcus aureus and other staphylococcal species are resident and transient multihost colonizers as well as conditional pathogens. Especially S. aureus represents an excellent model bacterium for the "One Health" concept because of its dynamics at the human-animal interface and versatility with respect to host adaptation. The development of antimicrobial resistance plays another integral part. This overview will focus on studies at the human-animal interface with respect to livestock farming and to companion animals, as well as on staphylococci in wildlife. In this context transmissions of staphylococci and of antimicrobial resistance genes between animals and humans are of particular significance.

Calcium Phosphate Cements as Carriers of Functional Substances for the Treatment of Bone Tissue

Interest in calcium phosphate cements as materials for the restoration and treatment of bone tissue defects is still high. Despite commercialization and use in the clinic, the calcium phosphate cements have great potential for development. Existing approaches to the production of calcium phosphate cements as drugs are analyzed. A description of the pathogenesis of the main diseases of bone tissue (trauma, osteomyelitis, osteoporosis and tumor) and effective common treatment strategies are presented in the review. An analysis of the modern understanding of the complex action of the cement matrix and the additives and drugs distributed in it in relation to the successful treatment of bone defects is given. The mechanisms of biological action of functional substances determine the effectiveness of use in certain clinical cases. An important direction of using calcium phosphate cements as a carrier of functional substances is the volumetric incorporation of anti-inflammatory, antitumor, antiresorptive and osteogenic functional substances. The main functionalization requirement for carrier materials is prolonged elution. Various release factors related to the matrix, functional substances and elution conditions are considered in the work. It is shown that cements are a complex system. Changing one of the many initial parameters in a wide range changes the final characteristics of the matrix and, accordingly, the kinetics. The main approaches to the effective functionalization of calcium phosphate cements are considered in the review.

Difficult-to-Treat Pathogens: A Review on the Management of Multidrug-Resistant Staphylococcus epidermidis

Multidrug-resistant Staphylococcus epidermidis (MDRSE) is responsible for difficult-to-treat infections in humans and hospital-acquired-infections. This review discusses the epidemiology, microbiology, diagnosis, and treatment of MDRSE infection and identifies knowledge gaps. By using the search term "pan resistant Staphylococcus epidermidis" OR "multi-drug resistant Staphylococcus epidermidis" OR "multidrug-resistant lineages of Staphylococcus epidermidis", a total of 64 records have been identified from various previously published studies. The proportion of methicillin resistance in S. epidermidis has been reported to be as high as 92%. Several studies across the world have aimed to detect the main phylogenetic lineages and antibiotically resistant genes through culture, mass spectrometry, and genomic analysis. Molecular biology tools are now available for the identification of S. epidermidis and its drug resistance mechanisms, especially in blood cultures. However, understanding the distinction between a simple colonization and a bloodstream infection (BSI) caused by S. epidermidis is still a challenge for clinicians. Some important parameters to keep in mind are the number of positive samples, the symptoms and signs of the patient, the comorbidities of the patient, the presence of central venous catheter (CVC) or other medical device, and the resistance phenotype of the organism. The agent of choice for empiric parenteral therapy is vancomycin. Other treatment options, depending on different clinical settings, may include teicoplanin, daptomycin, oxazolidinones, long-acting lipoglycopeptides, and ceftaroline. For patients with S. epidermidis infections associated with the presence of an indwelling device, assessment regarding whether the device warrants removal is an important component of management. This study provides an overview of the MDRSE infection. Further studies are needed to explore and establish the most correct form of management of this infection.

Teicoplanin-Resistant Coagulase-Negative Staphylococci: Do the Current Susceptibility Testing Methods Reliably Detect This Elusive Phenotype?

Coagulase-negative staphylococci (CoNS), members of the skin commensal microbiota, are increasingly associated with local or systemic infections due to a shift in patient populations in recent decades. Subsequently, more CoNS strains have been subjected to antibiotic susceptibility testing (AST), thus leading to the increased detection of teicoplanin resistance. However, data concerning teicoplanin resistance among CoNS strains remain limited, heterogeneous, and inconclusive. We collected 162 consecutive CoNS strains identified using Vitek-2 as teicoplanin-resistant and tested them with a range of AST methods. The results of standard and high inoculum broth microdilution (sBMD; hBMD), agar dilution (AD) after 24 h and 48 h incubation, standard and macrogradient diffusion strip (sGDT, MET), screening agar, and disc diffusion were compared to assess their robustness and to establish a diagnostic algorithm to detect teicoplanin resistance. sBMD was used as the reference method, and the lowest number of strains were teicoplanin-resistant using this method. sGDT and disc diffusion generated similar results to sBMD. Compared with sBMD, AD-24 h generated the lowest number of false teicoplanin-resistant strains, followed by hBMD, AD-48 h, and Vitek-2. sGDT, a fast, easy, affordable method in diagnostic settings, generated the highest rate of false teicoplanin-susceptible strains. Vitek-2 testing produced the highest number of teicoplanin-resistant strains. Only in two strains was the initial Vitek-2 teicoplanin resistance confirmed using five other AST methods. In conclusion, the different antibiotic susceptibility testing methods generated inconsistent, inconclusive, and discrepant results, thus making it difficult to establish a diagnostic algorithm for suspected teicoplanin resistance. Teicoplanin testing proved to be challenging and easily influenced by technical factors. This study aimed not only to raise awareness of teicoplanin resistance testing but also of the need for future studies focusing on the clinical efficacy of teicoplanin in relation to its susceptibility results.

Effect of Long-Term Use of Alcohol-Containing Handwashing Gels on the Biofilm-Forming Capacity of Staphylococcus epidermidis

The spread of coronavirus disease 2019 (COVID-19) has promoted the use of hand sanitizers among the general population as recommended by health authorities. Alcohols, which are used in many hand sanitizers, have been shown to promotes the formation of biofilms by certain bacteria and to increase bacterial resistance to disinfection. We investigated the effect of continued use of alcohol-based gel hand sanitizer on biofilm formation by the Staphylococcus epidermidis resident strain isolated from the hands of health science students. Hand microbes were counted before and after handwashing, and the ability to produce biofilms was investigated. We found that 179 (84.8%) strains of S. epidermidis isolated from hands had the ability to form biofilm (biofilm-positive strains) in an alcohol-free culture medium. Furthermore, the presence of alcohol in the culture medium induced biofilm formation in 13 (40.6%) of the biofilm-negative strains and increased biofilm production in 111 (76.6%) strains, which were classified as low-grade biofilm-producing. Based on our findings, there is no clear evidence that the continued use of alcohol-based gels results in the selection of strains with the capacity to form biofilms. However, other disinfectant formulations that are more commonly used in clinical settings, such as alcohol-based hand-rub solutions, should be tested for their long-term effects.

The Role of Coagulase-Negative Staphylococci Biofilms on Late-Onset Sepsis: Current Challenges and Emerging Diagnostics and Therapies

Infections are one of the most significant complications of neonates, especially those born preterm, with sepsis as one of the principal causes of mortality. Coagulase-negative staphylococci (CoNS), a group of staphylococcal species that naturally inhabit healthy human skin and mucosa, are the most common cause of late-onset sepsis, especially in preterms. One of the risk factors for the development of CoNS infections is the presence of implanted biomedical devices, which are frequently used for medications and/or nutrient delivery, as they serve as a scaffold for biofilm formation. The major concerns related to CoNS infections have to do with the increasing resistance to multiple antibiotics observed among this bacterial group and biofilm cells’ increased tolerance to antibiotics. As such, the treatment of CoNS biofilm-associated infections with antibiotics is increasingly challenging and considering that antibiotics remain the primary form of treatment, this issue will likely persist in upcoming years. For that reason, the development of innovative and efficient therapeutic measures is of utmost importance. This narrative review assesses the current challenges and emerging diagnostic tools and therapies for the treatment of CoNS biofilm-associated infections, with a special focus on late-onset sepsis.

Transcriptome Mining to Identify Molecular Markers for the Diagnosis of Staphylococcus epidermidis Bloodstream Infections

Bloodstream infections caused by Staphylococcus epidermidis are often misdiagnosed since no diagnostic marker found so far can unequivocally discriminate "true" infection from sample contamination. While attempts have been made to find genomic and/or phenotypic differences between invasive and commensal isolates, possible changes in the transcriptome of these isolates under in vivo-mimicking conditions have not been investigated. Herein, we characterized the transcriptome, by RNA sequencing, of three clinical and three commensal isolates after 2 h of exposure to whole human blood. Bioinformatics analysis was used to rank the genes with the highest potential to distinguish invasive from commensal isolates and among the ten genes identified as candidates, the gene SERP2441 showed the highest potential. A collection of 56 clinical and commensal isolates was then used to validate, by quantitative PCR, the discriminative power of the selected genes. A significant variation was observed among isolates, and the discriminative power of the selected genes was lost, undermining their potential use as markers. Nevertheless, future studies should include an RNA sequencing characterization of a larger collection of isolates, as well as a wider range of conditions to increase the chances of finding further candidate markers for the diagnosis of bloodstream infections caused by S. epidermidis.

Phenol-soluble modulin contributes to the dispersal of Staphylococcus epidermidis isolates from catheters

Staphylococcus epidermidis (S. epidermidis), a human commensal, has been implicated in invasive infection in humans due to their ability to form biofilm. It is assumed that when a biofilm is dispersed it will subsequently cause a more severe infection. The clinical significance of S. epidermidis isolated from sterile body fluid (BF) remains unclear, and might be related to dispersal from catheter-associated biofilm infection. To evaluate this relationship, we evaluated S. epidermidis isolates from catheters (CA) or BF in hospitalized patients. Sequence type 2 (ST2) is the most prevalent type isolated from infection sites. Although the specific STs were also observed in isolates from different sites, we observed that the main sequence type was ST2, followed by ST59, among all the 114 isolates from different infection sites. Interestingly, ST2 strains isolated from BF exhibited significantly thicker biofilm than those from CA. The thicker biofilm was due to the higher expression of accumulation-associated protein (aap) but not intercellular adhesion (ica) operon. Moreover, the transcription of PSMδ and PSMε were significantly increased in ST2 strains isolated from BF. Although the bacterial loads on catheters were similar infected by CA- or BF-originated strains in mouse biofilm-associated infection model, we observed a higher CFU in peri-catheter tissues infected by ST2 clones isolated from BF, suggesting that S. epidermidis with thicker biofilm formation might be able to disperse. Taken together, our data suggested that S. epidermidis originated from diverse infection sites exhibited different biofilm forming capacity. The major ST2 clone isolated from BF exhibited thicker biofilm by increasing the expression of Aap. The higher expression of PSM of these strains may contribute to bacteria dispersal from biofilm and the following bacterial spread.

Highly Synergistic Effects of Melittin With Vancomycin and Rifampin Against Vancomycin and Rifampin Resistant Staphylococcus epidermidis

Methicillin-resistant Staphylococcus epidermidis (MRSE) strains are increasingly emerging as serious pathogens because they can be resistant to many antibiotics called multidrug resistance (MDR) that limit the therapeutic options. In the case of vancomycin- and rifampin-resistant MDR-MRSE, the physicians are not allowed to increase the doses of antibiotics because of severe toxicity. Accordingly, we investigated the synergistic activity of melittin antimicrobial peptide with vancomycin and rifampin against vancomycin-resistant, and rifampin-resistant MDR-MRSE isolates. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), fractional inhibitory concentration index (FICi), and fractional bactericidal concentration index (FBCi) of antimicrobial agents against isolates were determined. Coagulate activities and serum and salt stability as well as melittin cytotoxicity on the human embryonic kidney (HEK) 293 cells and human red blood cells (RBCs) at their synergistic concentrations. MIC and MBC values for melittin were in the range of 0.312–2.5 and 0.312–5, respectively. Results also showed that the interaction of melittin with drugs was highly synergistic in which the geometric means of FICi and FBCi were < 0.5. Induced synergism led to a decrease in melittin, rifampin, and vancomycin concentrations by 8–1,020, 2–16, and 4–16-folds, respectively. This phenomenon caused a reduction in melittin toxicity by which the synergistic concentration of melittin needed to kill bacteria did not show cytotoxicity and hemolytic activity. Besides, no coagulation activity was found for the synergistic and alone concentrations of melittin in both Prothrombin Time (PT) and Partial Thromboplastin Time (PTT). Interestingly, the antibacterial activity of melittin in Mueller Hinton Broth (MHB) containing human serum did no significant differences between MIC and MBC values of melittin in MHB and MHB containing 10% human serum. The present findings showed that the therapeutic index of melittin was improved by 32.08- and 12.82-folds when combined with vancomycin and rifampin, respectively. Taken together, the obtained data show that melittin alone was effective against MDR-MRSE isolates and this antimicrobial peptide showed highly synergistic effects with vancomycin and rifampin without causing toxicity. Therefore, the combination of melittin and traditional antibiotics could be a promising strategy for the treatment of infections caused by MDR-MRSE.

Lack of Direct Correlation between Biofilm Formation and Antimicrobial Resistance in Clinical Staphylococcus epidermidis Isolates from an Italian Hospital

Staphylococcus epidermidis is an opportunistic pathogen and a frequent cause of nosocomial infections. In this work, we show that, among 51 S. epidermidis isolates from an Italian hospital, only a minority displayed biofilm formation, regardless of their isolation source (peripheral blood, catheter, or skin wounds); however, among the biofilm-producing isolates, those from catheters were the most efficient in biofilm formation. Interestingly, most isolates including strong biofilm producers displayed production levels of PIA (polysaccharide intercellular adhesin), the main S. epidermidis extracellular polysaccharide, similar to reference S. epidermidis strains classified as non-biofilm formers, and much lower than those classified as intermediate or high biofilm formers, possibly suggesting that high levels of PIA production do not confer a particular advantage for clinical isolates. Finally, while for the reference S. epidermidis strains the biofilm production clearly correlated with the decreased sensitivity to antibiotics, in particular, protein synthesis inhibitors, in our clinical isolates, such positive correlation was limited to tetracycline. In contrast, we observed an inverse correlation between biofilm formation and the minimal inhibitory concentrations for levofloxacin and teicoplanin. In addition, in growth conditions favoring PIA production, the biofilm-forming isolates showed increased sensitivity to daptomycin, clindamycin, and erythromycin, with increased tolerance to the trimethoprim/sulfamethoxazole association. The lack of direct correlation between the biofilm production and increased tolerance to antibiotics in S. epidermidis isolates from a clinical setting would suggest, at least for some antimicrobials, the possible existence of a trade-off between the production of biofilm determinants and antibiotic resistance.

Random amplified polymorphic DNA analysis reveals no clear link between Staphylococcus epidermidis and acute mastitis

Mastitis is commonly experienced by breastfeeding women. While Staphylococcus aureus is usually implicated in infectious mastitis, coagulase‐negative staphylococci (CoNS) are a possible alternative pathogen. This case‐control study examined the role of CoNS in mastitis using isolates cultured from breast milk of 20 women with mastitis and 16 women without mastitis. Gene sequencing determined bacterial species, and random amplified polymorphic DNA (RAPD) analysis investigated strain‐level variation. The majority of CoNS isolates were Staphylococcus epidermidis (182/199; 91%). RAPD analysis identified 33 unique S. epidermidis profiles, with no specific profile associated with mastitis cases.

Surveillance and prevalence of antimicrobial resistant bacteria from public settings within urban built environments: Challenges and opportunities for hygiene and infection control

Antimicrobial resistant (AMR) bacteria present one of the biggest threats to public health; this must not be forgotten while global attention is focussed on the COVID-19 pandemic. Resistant bacteria have been demonstrated to be transmittable to humans in many different environments, including public settings in urban built environments where high-density human activity can be found, including public transport, sports arenas and schools. However, in comparison to healthcare settings and agriculture, there is very little surveillance of AMR in the built environment outside of healthcare settings and wastewater. In this review, we analyse the existing literature to aid our understanding of what surveillance has been conducted within different public settings and identify what this tells us about the prevalence of AMR. We highlight the challenges that have been reported; and make recommendations for future studies that will help to fill knowledge gaps present in the literature.

[In vivo study on the effects of intercellular adhesion operon of Staphylococcus epidermidis on the inflammation associated with bacteria-fungal mixed biofilm]

Objective

To study the effect of intercellular adhesion (ica) operon of Staphylococcus epidermidis on the inflammation associated with mixed biofilm of Staphylococcus epidermidis and Candida albicans on endotracheal tube material in rabbits.

Methods

The standard strains of Staphylococcus epidermidis RP62A (ica operon positive, positive group) and ATCC12228 (ica operon negative, negative group) were taken to prepare a bacterial solution with a concentration of 1×10 ⁶ CFU/mL, respectively. Then, the two bacterial solutions were mixed with the standard strain of Candida albicans ATCC10231 of the same concentration to prepare a mixed culture solution at a ratio of 1∶1, respectively. The mixed culture solution was incubated with endotracheal tube material for 24 hours. The formation of mixed biofilm on the surface of the material was observed by scanning electron microscope. Thirty New Zealand rabbits, aged 4-6 months, were divided into two groups ( n=15), and the endotracheal tube materials of the positive group and the negative group that were incubated for 24 hours were implanted beside the trachea. The body mass of rabbits in the two groups was measured before operation and at 1, 3, and 7 days after operation. At 1, 3, and 7 days after operation, the levels of interleukin 1β (IL-1β), IL-6, tumor necrosis factor α (TNF-α), and monocytechemotactic protein 1 (MCP-1) were detected by using an ELISA test kit. At 7 days after operation, the formation of mixed biofilm on the surface of the endotracheal tube materials was observed by scanning electron microscope, the inflammation and infiltration of tissues around the materials were observed by HE staining, and the bacterial infections in heart, lung, liver, and kidney were observed by plate colony counting method.

Results

Scanning electron microscope observation showed that the mixed biofilm structure was obvious in the positive group after 24 hours in vitro incubation, but no mixed biofilm formation was observed in the negative group. In vivo studies showed that there was no significant difference in body mass between the two groups before operation and at 1, 3, and 7 days after operation ( P>0.05). Compared with the negative group, the levels of MCP-1 and IL-1β at 1 day, and the levels of IL-1β, MCP-1, IL-6, and TNF-α at 3 and 7 days in the positive group all increased, with significant differences ( P<0.05). Scanning electron microscope observation showed that a large amount of Staphylococcus epidermis and mixed biofilm structure were observed in the positive group, and a very small amount of bacteria was observed in the negative group with no mixed biofilm structure. HE staining of surrounding tissue showed inflammatory cell infiltration in both groups, and neutrophils and lymphocytes were more in the positive group than in the negative group. There was no significant difference in the number of bacterial infections in heart and liver between the two groups ( P>0.05). The number of bacterial infections in lung and kidney in the positive group was higher than that in negative group ( P<0.05).

Conclusion

In the mixed infection of Staphylococcus epidermidis and Candida albicans, the ica operon may strengthen the structure of the biofilm and the spread of the biofilm in vivo, leading to increased inflammatory factors, and the bacteria are difficult to remove and persist.

IL-6 Signaling Protects Zebrafish Larvae during Staphylococcus epidermidis Infection in a Bath Immersion Model

The host immune responses to Staphylococcus epidermidis, a frequent cause of nosocomial infections, are not well understood. We have established a bath immersion model of this infection in zebrafish (Danio rerio) larvae. Macrophages play a primary role in the host immune response and are involved in clearance of infection in the larvae. S. epidermidis infection results in upregulation of tlr-2 There is marked inflammation characterized by heightened NF-κB signaling and elevation of several proinflammatory cytokines. There is rapid upregulation of il-1b and tnf-a transcripts, whereas an increase in il-6 levels is relatively more delayed. The IL-6 signaling pathway is further amplified by elevation of IL-6 signal transducer (il-6st) levels, which negatively correlates with miRNA dre-miR-142a-5p. Enhanced IL-6 signaling is protective to the host in this model as inhibition of the signaling pathway resulted in increased mortality upon S. epidermidis infection. Our study describes the host immune responses to S. epidermidis infection, establishes the importance of IL-6 signaling, and identifies a potential role of miR-142-5p-il-6st interaction in this infection model.

Coagulase-Negative Staphylococci Clones Are Widely Distributed in the Hospital and Community

Coagulase-negative staphylococci (CoNS) may be considered contaminants when isolated from clinical specimens but may also be a cause of true infection. This study aimed to compare the clonality and SCCmec type of a collection of CoNS isolated from blood cultures of inpatients, nasal swabs of healthy individuals, and patients with chronic wounds, all from the same community, using SCCmec typing, pulsed-field gel electrophoresis (PFGE), and MLST. Staphylococcus epidermidis, exhibited high clonal diversity, but hospital and community clusters were observed. Nosocomial S. epidermidis clones belonged to sequence types ST2, ST6, and ST23. Some Staphylococcus haemolyticus clones were found to circulate in the hospital and community, while Staphylococcus saprophyticus exhibited very high clonal diversity. Staphylococcus lugdunensis, Staphylococcus warneri, and Staphylococcus capitis revealed several isolates belonging to the same clone in the hospital and community. The detection of different SCCmec types within the same cluster indicated high diversity. S. epidermidis was associated with SCCmec I and III, S. haemolyticus with I and II, S. capitis with type V, Staphylococcus hominis with mec complex type A and ccr1, and S. warneri and S. saprophyticus with SCCmec I. The generation of elements and new combinations of cassette genes were highly associated with CoNS isolates, suggesting that SCCmec may not be a good marker of clonality in these bacteria.

S. epidermidis Isolates from a Tertiary Care Portuguese Hospital Show Very High Antibiotic Non-Susceptible Rates and Significant Ability to Form Biofilms

Healthcare-associated infections (HAIs) have been increasing during recent decades, leading to long hospital stays and high morbidity and mortality rates. The usage of antibiotics therapy against these infections is enhancing the emergence of more multiple-drug resistant strains, in particular in Staphylococcus epidermidis. Hence, this study focused on the resistance pattern of S. epidermidis isolates from clinical settings and its association with phenotypic and molecular traits. Our results showed that HAIs were more prevalent among infants and older adults, and the most frequent type of HAI was central line-associated bloodstream infection. Half of the patients received antibiotic therapy before laboratory diagnosis. Preceding microbiological diagnosis, the number of patients receiving antibiotic therapy increased by 29.1%. Eighty-six per cent of the clinical isolates presented a multidrug resistance (MDR) profile, and a quarter were strong biofilm producers. Furthermore, polysaccharide intercellular adhesin (PIA)-dependent biofilms presented higher biomass production (p = 0.0041) and a higher rate of antibiotic non-susceptibility than PIA-independent biofilms, emphasizing the role of icaABDC operon in infection severity. Therefore, this study suggests that a thorough understanding of the phenotypic and molecular traits of the bacterial cause of the HAIs may lead to a more suitable selection of antibiotic therapy, improving guidance and outcome assessment.

Coagulase negative Staphylococcus bacteremia in hematopoietic stem cell transplant recipients: Clinical features and molecular characterization

The purpose of our study was to investigate the epidemiology of coagulase negative staphylococci (CoNS) responsible for bacteremia in hematopoietic stem cell transplant (HSCT) recipients and to determine the prevalence and the genetic background of methicillin resistance. The prevalence of CoNS bacteremia was 7.4% (54/728), higher in allograft (10.7%) than in autograft (4.7%) recipients. A sepsis or a septic shock were observed in 9% of cases. No deaths were attributable to CoNS bacteremia. The methicillin resistance rate was 81%. All MR-CoNS, harbored mecA gene and 90% were typeable with SCCmec typing using PCR amplification. The SCCmec type IV was the most frequent (44%). Clonal dissemination of MR- Staphylococcus epidermidis strains was limited. Our study showed a low prevalence and favorable outcome of CoNS bacteremia in HSCT recipients with limited clonal diffusion. However, they were associated with a significant rate of severe infections and a high rate of methicillin resistance, mediated by SCCmec IV element in most cases.

Comparative Genomics Analysis Demonstrated a Link Between Staphylococci Isolated From Different Sources: A Possible Public Health Risk

Coagulase-negative staphylococci (CoNS) have been recovered from different ecological niches, however, little is known about the genetic relatedness of these isolates. In this study, we used whole genome sequencing to compare mecA positive (mecA ⁺) Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus hominis isolates recovered from hand-touched surfaces from general public settings in East and West London with data of isolates deposited to European Nucleotide Archive (ENA) by other research groups. These included isolates associated with hospital settings (including those recovered from patients), healthy humans, livestock, pets, plants and natural, and other public environments. Using core and accessory phylogenetic analyses we were able to identify that the mecA⁺ S. epidermidis and S. haemolyticus isolates recovered from general public settings were genetically related to isolates recovered from the bloodstream, urinary tract and eye infections. S. epidermidis isolates recovered in our study were also shown to be genetically related to isolates previously recovered from livestock/livestock housing, whereas S. haemolyticus isolates were genetically related to isolates recovered from a dog and kefir (fermented cow milk drink). MecA ⁺ S. hominis isolates were not genetically related to any isolates recovered from clinical samples but were genetically related to isolates recovered from mosquitoes, air samples (residential areas) and kefir. All three species showed to have genetic relatedness to isolates recovered from healthy humans. These results show that CoNS isolates in this study share genetic similarities with those of different lineages and that mecA⁺ S. epidermidis and S. haemolyticus isolates found in general public settings in this study may pose a risk to public health.

Genomic investigation of clinically significant coagulase-negative staphylococci

Introduction. Coagulase-negative staphylococci have been recognized both as emerging pathogens and contaminants of clinical samples. High-resolution genomic investigation may provide insights into their clinical significance.Aims. To review the literature regarding coagulase-negative staphylococcal infection and the utility of genomic methods to aid diagnosis and management, and to identify promising areas for future research.Methodology. We searched Google Scholar with the terms (Staphylococcus) AND (sequencing OR (infection)). We prioritized papers that addressed coagulase-negative staphylococci, genomic analysis, or infection.Results. A number of studies have investigated specimen-related, phenotypic and genetic factors associated with colonization, infection and virulence, but diagnosis remains problematic.Conclusion. Genomic investigation provides insights into the genetic diversity and natural history of colonization and infection. Such information allows the development of new methodologies to identify and compare relatedness and predict antimicrobial resistance. Future clinical studies that employ suitable sampling frames coupled with the application of high-resolution whole-genome sequencing may aid the development of more discriminatory diagnostic approaches to coagulase-staphylococcal infection.

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 staphylococcal exopolysaccharide PIA - Biosynthesis and role in biofilm formation, colonization, and infection

Exopolysaccharide is a key part of the extracellular matrix that contributes to important mechanisms of bacterial pathogenicity, most notably biofilm formation and immune evasion. In the human pathogens Staphylococcus aureus and S. epidermidis, as well as in many other staphylococcal species, the only exopolysaccharide is polysaccharide intercellular adhesin (PIA), a cationic, partially deacetylated homopolymer of N-acetylglucosamine, whose biosynthetic machinery is encoded in the ica locus. PIA production is strongly dependent on environmental conditions and controlled by many regulatory systems. PIA contributes significantly to staphylococcal biofilm formation and immune evasion mechanisms, such as resistance to antimicrobial peptides and ingestion and killing by phagocytes, and presence of the ica genes is associated with infectivity. Due to its role in pathogenesis, PIA has raised considerable interest as a potential vaccine component or target.

The staphylococcal exopolysaccharide PIA - Biosynthesis and role in biofilm formation, colonization, and infection

•

PIA is a key extracellular matrix component in staphylococci and other bacteria.

•

PIA is a cationic, partially deacetylated N-acetylglucosamine polymer.

•

PIA has a major role in bacterial biofilms and biofilm-associated infection.

Exopolysaccharide is a key part of the extracellular matrix that contributes to important mechanisms of bacterial pathogenicity, most notably biofilm formation and immune evasion. In the human pathogens Staphylococcus aureus and S. epidermidis, as well as in many other staphylococcal species, the only exopolysaccharide is polysaccharide intercellular adhesin (PIA), a cationic, partially deacetylated homopolymer of N-acetylglucosamine, whose biosynthetic machinery is encoded in the ica locus. PIA production is strongly dependent on environmental conditions and controlled by many regulatory systems. PIA contributes significantly to staphylococcal biofilm formation and immune evasion mechanisms, such as resistance to antimicrobial peptides and ingestion and killing by phagocytes, and presence of the ica genes is associated with infectivity. Due to its role in pathogenesis, PIA has raised considerable interest as a potential vaccine component or target.

Staphylococcal Biofilm Development: Structure, Regulation, and Treatment Strategies

In many natural and clinical settings, bacteria are associated with some type of biotic or abiotic surface that enables them to form biofilms, a multicellular lifestyle with bacteria embedded in an extracellular matrix. Staphylococcus aureus and Staphylococcus epidermidis, the most frequent causes of biofilm-associated infections on indwelling medical devices, can switch between an existence as single free-floating cells and multicellular biofilms. During biofilm formation, cells first attach to a surface and then multiply to form microcolonies. They subsequently produce the extracellular matrix, a hallmark of biofilm formation, which consists of polysaccharides, proteins, and extracellular DNA. After biofilm maturation into three-dimensional structures, the biofilm community undergoes a disassembly process that leads to the dissemination of staphylococcal cells. As biofilms are dynamic and complex biological systems, staphylococci have evolved a vast network of regulatory mechanisms to modify and fine-tune biofilm development upon changes in environmental conditions. Thus, biofilm formation is used as a strategy for survival and persistence in the human host and can serve as a reservoir for spreading to new infection sites. Moreover, staphylococcal biofilms provide enhanced resilience toward antibiotics and the immune response and impose remarkable therapeutic challenges in clinics worldwide. This review provides an overview and an updated perspective on staphylococcal biofilms, describing the characteristic features of biofilm formation, the structural and functional properties of the biofilm matrix, and the most important mechanisms involved in the regulation of staphylococcal biofilm formation. Finally, we highlight promising strategies and technologies, including multitargeted or combinational therapies, to eradicate staphylococcal biofilms.

Staphylococcal Biofilm Development: Structure, Regulation, and Treatment Strategies

In many natural and clinical settings, bacteria are associated with some type of biotic or abiotic surface that enables them to form biofilms, a multicellular lifestyle with bacteria embedded in an extracellular matrix. Staphylococcus aureus and Staphylococcus epidermidis, the most frequent causes of biofilm-associated infections on indwelling medical devices, can switch between an existence as single free-floating cells and multicellular biofilms. During biofilm formation, cells first attach to a surface and then multiply to form microcolonies. They subsequently produce the extracellular matrix, a hallmark of biofilm formation, which consists of polysaccharides, proteins, and extracellular DNA. After biofilm maturation into three-dimensional structures, the biofilm community undergoes a disassembly process that leads to the dissemination of staphylococcal cells. As biofilms are dynamic and complex biological systems, staphylococci have evolved a vast network of regulatory mechanisms to modify and fine-tune biofilm development upon changes in environmental conditions. Thus, biofilm formation is used as a strategy for survival and persistence in the human host and can serve as a reservoir for spreading to new infection sites. Moreover, staphylococcal biofilms provide enhanced resilience toward antibiotics and the immune response and impose remarkable therapeutic challenges in clinics worldwide. This review provides an overview and an updated perspective on staphylococcal biofilms, describing the characteristic features of biofilm formation, the structural and functional properties of the biofilm matrix, and the most important mechanisms involved in the regulation of staphylococcal biofilm formation. Finally, we highlight promising strategies and technologies, including multitargeted or combinational therapies, to eradicate staphylococcal biofilms.

Epidemiological Analysis of Antimicrobial Resistance in Staphylococcus epidermidis in Scotland, 2014-2018

Aims: This study aimed to investigate recent national surveillance trends in Staphylococcus epidermidis antibiotic resistance in Scotland and to draw conclusions on the potential clinical and public health impact of multidrug-resistant isolates. Results: Resistance in S. epidermidis isolates to individual agents was broadly stable over the past 5 years. Isolates from sterile sites, and therefore those most likely to be associated with clinical infection, were found to be more resistant to the majority of reported agents, than isolates from nonsterile sites. Increased resistance to a number of important antibiotics was observed in rifampicin-, vancomycin-, and daptomycin-resistant isolates, suggesting limited treatment options for infections caused by these isolates. Conclusions: Although S. epidermidis resistance to individual agents has been broadly stable over the past 5 years nationally, of particular concern is the association of multidrug resistance in rifampicin-resistant isolates, which has been reported elsewhere. This has the potential to result in treatment failures in significant device-related infections.

Characteristics of oral methicillin-resistant Staphylococcus epidermidis isolated from dental plaque

The oral microbial community is widely regarded as a latent reservoir of antibiotic resistance genes. This study assessed the molecular epidemiology, susceptibility profile, and resistance mechanisms of 35 methicillin-resistant Staphylococcus epidermidis (MRSE) strains isolated from the dental plaque of a healthy human population. Broth microdilution minimum inhibitory concentrations (MICs) revealed that all the isolates were nonsusceptible to oxacillin and penicillin G. Most of them were also resistant to trimethoprim (65.7%) and erythromycin (54.3%). The resistance to multiple antibiotics was found to be largely due to the acquisition of plasmid-borne genes. The mecA and dfrA genes were found in all the isolates, mostly dfrG (80%), aacA-aphD (20%), aadD (28.6%), aphA3 (22.9%), msrA (5.7%), and the ermC gene (14.3%). Classical mutational mechanisms found in these isolates were mainly efflux pumps such as qacA (31.4%), qacC (25.7%), tetK (17.1%), and norA (8.6%). Multilocus sequence type analysis revealed that sequence type 59 (ST59) strains comprised 71.43% of the typed isolates, and the eBURST algorithm clustered STs into the clonal complex 2-II(CC2-II). The staphyloccoccal cassette chromosome mec (SCCmec) type results showed that 25 (71.43%) were assigned to type IV. Moreover, 88.66% of the isolates were found to harbor six or more biofilm-associated genes. The aap, atlE, embp, sdrF, and IS256 genes were detected in all 35 isolates. This research demonstrates that biofilm-positive multiple-antibiotic-resistant ST59-SCCmec IV S. epidermidis strains exist in the dental plaque of healthy people and may be a potential risk for the transmission of antibiotic resistance.

Emergence of linezolid-resistant Staphylococcus epidermidis in the tertiary children's hospital in Cracow, Poland

Coagulase-negative staphylococci, ubiquitous commensals of human skin, and mucous membranes represent important pathogens for immunocompromised patients and neonates. The increasing antibiotic resistance among Staphylococcus epidermidis is an emerging problem worldwide. In particular, the linezolid-resistant S. epidermidis (LRSE) strains are observed in Europe since 2014. The aim of our study was to genetically characterize 11 LRSE isolates, recovered mostly from blood in the University Children’s Hospital in Krakow, Poland, between 2015 and 2017. For identification of the isolates at the species level, we used 16S rRNA sequencing and RFLP of the saoC gene. Isolates were characterized phenotypically by determining their antimicrobial resistance patterns and using molecular methods such as PFGE, MLST, SCCmec typing, detection of the ica operon, and analysis of antimicrobial resistance determinants. All isolates were multidrug-resistant, including resistance to methicillin, and exhibited so-called PhLOPS_A phenotype. In PFGE, all isolates (excluding one from a catheter) represented identical patterns, were identified as ST2, and harbored the ica operon, responsible for biofilm formation. Linezolid resistance was associated with acquisition of A157R mutation in the ribosomal protein L3 and the presence of cfr gene. All isolates revealed new SCCmec cassette element composition. Recently, pediatric patients with serious staphylococcal infections are often treated with linezolid. The increasing linezolid resistance in bacterial strains becomes a real threat for patients, and monitoring such infections combined with surveillance and infection prevention programs is very important to decrease number of linezolid-resistant staphylococcal strains.

Genotypic and phenotypic analysis of biofilm formation Staphylococcus epidermidis isolates from clinical specimens

OBJECTIVES

Staphylococcus epidermidis is the primary causative agent of infections associated with indwelling biomaterials. Antibiotic susceptibility patterns, Biofilm formation capability, and screening of responsible genes in biofilm formation procedure in clinical isolates (icaA, icaB, icaC, icaD, sdrG, and atlE) were assigned as the main objectives in this study. The clinical samples were analyzed via standard biochemical assays for identifying different bacteria which were confirmed using the multiplex colony PCR method. Subsequently, biofilm-formation capability, antibiotic susceptibility testing, and the frequency of genes responsible for biofilm formation in the confirmed strains were checked.

RESULTS

Out of 183 clinical specimens 54 S. epidermidis isolates were detected by targeting a housekeeping gene (sesc) taking advantage of the PCR procedure. All of the strains were Biofilm forming producers. The in vitro biofilm formation assays determined that 45 (83.33%), 5 (9.26%), 4 (7.41%) were strong, moderate, and weak biofilm former strains respectively. Among the isolated strains, the specific frequencies of the biofilm-forming genes were specified to be (98%) for sdrG, (84%) for atlE, (80%) for icaC, and (70%) for icaD. Cefamandole and Amikacin are the most effective antibiotics in isolated strains. All strains were ascertained to be methicillin and amoxicillin/clavulanic acid resistant.

Whole-genome sequencing of Staphylococcus epidermidis bloodstream isolates from a prospective clinical trial reveals that complicated bacteraemia is caused by a limited number of closely related sequence types

OBJECTIVES

The significance of isolating Staphylococus epidermidis from a blood culture is highly heterogeneous, ranging from contamination to an indication of a serious infection. Herein we sought to determine whether there is a relationship between S. epidermidis genotype and clinical severity of bacteraemia.

METHODS

S. epidermidis bacteraemias from a prospective, multicentre trial at 15 centres in the United States and one in Spain were classified as simple (including possible contamination), uncomplicated, and complicated. Whole-genome sequencing (WGS) was performed on 161 S. epidermidis isolates, and clinical outcomes were correlated with genotypic information.

RESULTS

A total of 49 S. epidermidis sequence types (STs) were identified. Although strains of all 49 STs were isolated from patients with either simple or uncomplicated infection, all strains causing complicated infections were derived from five STs: ST2, ST5, ST7, ST16, and ST32. ST2 and ST5 isolates were significantly more likely to cause uncomplicated and complicated bloodstream infections compared to simple bacteraemia (odds ratio 2.0, 95%CI 1.1-3.9, p 0.04). By multivariate regression analysis, having an ST2 or ST5 S. epidermidis bacteraemia was an independent predictor of complicated bloodstream infection (odds ratio 3.7, 95%CI 1.2-11.0, p 0.02). ST2/ST5 strains carried larger numbers of antimicrobial resistance determinants compared to non-ST2/ST5 isolates (6.34 ± 1.5 versus 4.4 ± 2.5, p < 0.001).

CONCLUSION

S. epidermidis bacteraemia was caused by a genetically heterogeneous group of organisms, but only a limited number of STs-particularly multidrug-resistant ST2 and ST5 strains-caused complicated infections.

Antimicrobial resistance and genetic characterization of coagulase-negative staphylococci from bovine mastitis milk samples in Korea

Coagulase-negative staphylococci (CNS) are one of the most common bovine mastitis pathogens found worldwide. In this study, we investigated the prevalence and distribution of CNS species in mastitis milk samples and further characterized the methicillin-resistant (MR) CNS. A total of 311 CNS were isolated from 3,692 quarter milk samples from 1,373 dairy cattle at 81 farms between 2013 and 2017. Further evaluation of the CNS isolates revealed 14 CNS species among the samples and 3 predominant species-namely, Staphylococcus chromogenes, Staphylococcus simulans, and Staphylococcus epidermidis. Resistance was higher in S. epidermidis than in other CNS species except for resistance against oxacillin in Staphylococcus sciuri. Resistance to β-lactams was the most common in all CNS species (8.4% in ampicillin, 21.2% in oxacillin, and 13.5% in penicillin). Conversely, only minimal resistance to cephalothin, ceftiofur, and pirlimycin/novobiocin was found. Twenty-one isolates from 4 species were mecA-carrying MRCNS strains, including 18 S. epidermidis and 1 each of S. sciuri, Staphylococcus equorum, and Staphylococcus hominis. The majority of the mecA-carrying MRCNS isolates were produced in the biofilm. Furthermore, multidrug-resistant sequence type 179 isolate produced the strongest biofilm. Seven genotypes were detected in the 18 MR S. epidermidis strains, the most predominant of which persisted on a farm for 2 yr. Our findings for the antimicrobial susceptibility profiles and genotypic characterization of the MRCNS isolates could provide valuable information for controlling the spread of resistance and the selection of appropriate antimicrobial therapies for mastitis in the future. Further, strategic antibiotic use for mastitis treatment and hygienic management practices aimed at the prevention of the growth of resistant bacteria are urgently needed on dairy farms.

Distinct Phenotypic and Genomic Signatures Underlie Contrasting Pathogenic Potential of Staphylococcus epidermidis Clonal Lineages

Background: Staphylococcus epidermidis is a common skin commensal that has emerged as a pathogen in hospitals, mainly related to medical devices-associated infections. Noteworthy, infection rates by S. epidermidis have the tendency to rise steeply in next decades together with medical devices use and immunocompromized population growth. Staphylococcus epidermidis population structure includes two major clonal lineages (A/C and B) that present contrasting pathogenic potentials. To address this distinction and explore the basis of increased pathogenicity of A/C lineage, we performed a detailed comparative analysis using phylogenetic and integrated pangenome-wide-association study (panGWAS) approaches and compared the lineages's phenotypes in in vitro conditions mimicking carriage and infection. Results: Each S. epidermidis lineage had distinct phenotypic signatures in skin and infection conditions and differed in genomic content. Combination of phenotypic and genotypic data revealed that both lineages were well adapted to skin environmental cues. However, they appear to occupy different skin niches, perform distinct biological functions in the skin and use different mechanisms to complete the same function: lineage B strains showed evidence of specialization to survival in microaerobic and lipid rich environment, characteristic of hair follicle and sebaceous glands; lineage A/C strains showed evidence for adaption to diverse osmotic and pH conditions, potentially allowing them to occupy a broader and more superficial skin niche. In infection conditions, A/C strains had an advantage, having the potential to bind blood-associated host matrix proteins, form biofilms at blood pH, resist antibiotics and macrophage acidity and to produce proteases. These features were observed to be rare in the lineage B strains. PanGWAS analysis produced a catalog of putative S. epidermidis virulence factors and identified an epidemiological molecular marker for the more pathogenic lineage. Conclusion: The prevalence of A/C lineage in infection is probably related to a higher metabolic and genomic versatility that allows rapid adaptation during transition from a commensal to a pathogenic lifestyle. The putative virulence and phenotypic factors associated to A/C lineage constitute a reliable framework for future studies on S. epidermidis pathogenesis and the finding of an epidemiological marker for the more pathogenic lineage is an asset for the management of S. epidermidis infections.

Antimicrobial susceptibility, virulence determinants profiles and molecular characteristics of Staphylococcus epidermidis isolates in Wenzhou, eastern China

BACKGROUND

Staphylococcus epidermidis has emerged as an often encountered pathogen responsible for hospital-acquired infections. The aim of present study is to investigate the microbiological characteristic of S. epidermidis isolates isolated from sterile specimens and skin in a Chinese tertiary hospital.

METHODS

A total of 223 non-duplicate S. epidermidis were collected from various sterile specimens of inpatients among 10 years in Wenzhou, China. 106 S. epidermidis obtained from the skin (urethral orifices) of healthy volunteers. All isolates were tested for antimicrobial susceptibility. PCR was used to detect the virulence- and resistance-associated genes and 7 housekeeping genes to determine the sequence types (STs) of selected isolates.

RESULTS

The resistance rates to antimicrobials tested except linezolid and vancomycin and the prevalence of methicillin-resistant S. epidermidis (MRSE) of S. epidermidis clinical isolates were significantly higher than those among colonized isolates (P < 0.05). The positive rates of virulence-associated genes including aap, sesI, ACME-arcA, IS256, bhp, altE, aae and gehD for S. epidermidis clinical isolates were significantly higher than those for colonized isolate (P < 0.05). A total of 60 STs including 28 from clinical isolates and 32 from colonized isolates were identified by MLST. A novel, rarely encountered clone, ST466, was found to be the second prevalent clone among clinical isolates. The great majority of the S. epidermidis isolates tested (73.86%) belonged to clone complex 2 (CC2). Compared with ST2, ST130, ST20 and ST59 clones, ST466 clone had the highest resistance rate to tetracycline (50.00%), the second highest prevalence of ACME-arcA (65.00%), bhp (30.00%) and qacA/B (65.00%), very low prevalence of carriage of icaA (0.00%) and biofilm formation (0.00%), the lack of sesI and high prevalence of aap, altE and aae (> 90%), which was similar to the characteristics of ST59 clone with one locus difference from ST466. ST466 clone competence with Staphylococcus aureus was relatively stronger, relative to ST2, ST20, ST130 and ST59 clones.

CONCLUSION

Taken together, a high-level of genetic diversity was found between clinical and colonized S. epidermidis isolates. A novel ST466 clone with distinct and similar characteristics relative to other prevalent clones, emerging as a prevalent clone in China, should be of major concern.

Emergence and control of linezolid-resistant Staphylococcus epidermidis in an ICU of a German hospital

Objectives

To investigate an outbreak of linezolid-resistant Staphylococcus epidermidis (LRSE) in an interdisciplinary ICU, linezolid consumption and infection control measures taken.

Methods

Routine surveillance of nosocomial infections revealed colonization and infection with LRSE affecting 14 patients during a 15 month period. LRSE isolates were analysed with respect to their clonal relatedness, antimicrobial susceptibility, the presence of cfr and/or mutations in the 23S rRNA, rplC, rplD and rplV genes. cfr plasmids were characterized by Illumina sequencing. Medical records were reviewed and antibiotic consumption was determined.

Results

Molecular typing identified the presence of three different LRSE clusters: PFGE type I/ST168 (n = 5), PFGE type II/ST5 (n = 10) and PFGE type III/ST2 (n = 1). Ten strains harboured the cfr gene; we also detected mutations in the respective ribosomal protein genes. WGS revealed an almost identical 39 kb cfr plasmid obtained from strains of different genetic background (ST2, ST5, ST168) that shows high similarity to the recently published LRSE plasmid p12-02300. Due to an increase in the number of patients treated for infections with MRSA, a significant increase in linezolid usage was noted from January to July 2014 (from 5.55 to 20.41 DDDs/100 patient-days).

Conclusions

Here, we report the molecular epidemiology of LRSE in an ICU. Our results suggest the selection of resistant mutants under linezolid treatment as well as the spread of cfr-carrying plasmids. The reduction of linezolid usage and the strengthening of contact precautions proved to be effective infection control measures.

Clonally Diverse Methicillin and Multidrug Resistant Coagulase Negative Staphylococci Are Ubiquitous and Pose Transfer Ability Between Pets and Their Owners

Sixty-eight owners and 66 pets, from 43 unrelated pet-owning households were screened for methicillin-resistant coagulase negative staphylococci (MRCoNS), potential cases of MRCoNS interspecies transmission (IT), and persistence. MRCoNS isolates were identified by microbiological and molecular tests. MLST-based phylogenetic analysis was performed in Staphylococcus epidermidis isolates. Antimicrobial susceptibility was evaluated using phenotypic and molecular methods. SCCmec type and the presence of biofilm-related ica locus was PCR-tested. Isolates suspected for MRCoNS IT cases were subjected to SmaI-PFGE analysis and individuals from positive households were followed-up for 1 year for carriage dynamics (every 3 months, T0-T4). Nineteen MRCoNS isolates from owners (27.9%) and 12 from pets (16.7%) were detected, coming from 20 households (46.5%). S. epidermidis was predominant (90 and 67% of human and animal strains, respectively), showing high phylogenetic diversity (16 STs among 24 strains). Methicillin-resistant S. epidermidis (MRSE) strains belonged to CC5 (75%), CC11 (12.5%), singleton S556 (8.3%), and S560 (4.17%). Significant host-associated differences were observed for resistance to aminoglycosides, co-trimoxazole, chloramphenicol (higher in animal isolates) and tetracycline (higher among human strains). Multidrug resistance (MDR) was common (68.4%) and associated with human strains. Great diversity of ccr and mec complexes were detected, most strains being non-typeable, followed by SCCmecIV and V. Over one third of isolates (most from owners), carried the ica locus, all MRSE CC5. Two sporadic IT cases (T0) were identified in owners and dogs from two households (4.7%), with diverse interspecies-exchanged clones detected along the sampling year, especially in dogs. A comparative analysis of all MRCoNS, with all nasal coagulase positive staphylococci (CoPS) recovered from the same individuals at T0, revealed that CoPS alone was predominant in owners and pets, followed by co-carriage of CoPS and MRCoNS in owners but single MRCoNS in pets. Statistical analyses revealed that owners are more prone to co-carriage and that co-existence of IT cases and co-carriage are positively interrelated. MRCoNS from healthy owners and their pets are genetically heterogeneous MDR strains that are spread in the community. Therefore, pets also contribute to the dissemination of successful human clones. Owner-pet inhabitancy increases the risk for staphylococcal temporal concomitance with its subsequent risk for bacterial infection and genetic exchange.

Variability of resistance plasmids in coagulase-negative staphylococci and their importance as a reservoir of antimicrobial resistance

Coagulase-negative staphylococci (CoNS) are an important cause of human and animal diseases. Treatment of these diseases is complicated by their common antimicrobial resistance, caused by overuse of antibiotics in hospital and veterinary environment. Therefore, they are assumed to serve as a reservoir of resistance genes often located on plasmids. In this study, we analyzed plasmid content in 62 strains belonging to 10 CoNS species of human and veterinary origin. In 48 (77%) strains analyzed, 107 different plasmids were detected, and only some of them showed similarities with plasmids found previously. In total, seven different antimicrobial-resistance genes carried by plasmids were identified. Five of the CoNS staphylococci carried plasmids identical with either those of other CoNS species tested, or a well characterized Staphylococcus aureus strain COL, suggesting plasmid dissemination through horizontal transfer. To demonstrate the possibility of horizontal transfer, we performed electroporation of four resistance plasmids among Staphylococcus epidermidis, Staphylococcus petrasii, and coagulase-positive S. aureus strains. Plasmids were transferred unchanged, were stably maintained in recipient strains, and expressed resistance genes. Our work demonstrates a great variability of plasmids in human and veterinary staphylococcal strains and their ability to maintain and express resistance plasmids from other staphylococcal species.

Tetrasodium EDTA Is Effective at Eradicating Biofilms Formed by Clinically Relevant Microorganisms from Patients' Central Venous Catheters

The colonization of catheters by microorganisms often precludes their long-term use, which can be a problem for human patients that have few body sites available for new catheters. The colonizing organisms often form biofilms, and increasingly these organisms are resistant to multiple antibiotics, making them difficult to treat. In this article, we have taken microorganisms that are associated with biofilm formation in catheters from two Canadian hospitals and tested them with tetrasodium EDTA, a new antimicrobial catheter lock solution. Tetrasodium EDTA was effective at eliminating Gram-positive, Gram-negative, and fungal species and represents a promising alternative to antibiotic treatment with less chance of the organisms developing resistance. We expect that our results will be of interest to researchers and clinicians and will lead to improved patient care.

Central venous access devices (CVADs) are an essential component of modern health care. However, their prolonged use commonly results in microbial colonization, which carries the potential risk of hospital-acquired bloodstream infections. These infections complicate the treatment of already sick individuals and cost the existing health care systems around the world millions of dollars. The microbes that colonize CVADs typically form multicellular biofilms that are difficult to dislodge and are resistant to antimicrobial treatments. Clinicians are searching for better ways to extend the working life span of implanted CVADs, by preventing colonization and reducing the risk of bloodstream infections. In this study, we analyzed 210 bacterial and fungal isolates from colonized CVADs or human bloodstream infections from two hospitals geographically separated in the east and west of Canada and screened the isolates for biofilm formation in vitro. Twenty isolates, representing 12 common, biofilm-forming species, were exposed to 4% tetrasodium EDTA, an antimicrobial lock solution that was recently approved in Canada for use as a medical device. The EDTA solution was effective at eradicating surface-attached biofilms from each microbial species, indicating that it could likely be used to prevent biofilm growth within CVADs and to eliminate established biofilms. This new lock solution fits with antibiotic stewardship programs worldwide by sparing the use of important antibiotic agents, targeting prevention rather than the expensive treatment of hospital-acquired infections.

IMPORTANCE The colonization of catheters by microorganisms often precludes their long-term use, which can be a problem for human patients that have few body sites available for new catheters. The colonizing organisms often form biofilms, and increasingly these organisms are resistant to multiple antibiotics, making them difficult to treat. In this article, we have taken microorganisms that are associated with biofilm formation in catheters from two Canadian hospitals and tested them with tetrasodium EDTA, a new antimicrobial catheter lock solution. Tetrasodium EDTA was effective at eliminating Gram-positive, Gram-negative, and fungal species and represents a promising alternative to antibiotic treatment with less chance of the organisms developing resistance. We expect that our results will be of interest to researchers and clinicians and will lead to improved patient care.

Cationic Branched Polyethylenimine (BPEI) Disables Antibiotic Resistance in Methicillin-Resistant Staphylococcus epidermidis (MRSE)

Staphylococcus epidermidis is one of the most prevalent prokaryotic species on human skin and mucosal membranes that constitute the commensal flora. S. epidermidis has become one of the most common causes of primary bacteremia. Infections are difficult to diagnose because the pathogen has natural niches on human skin and the ability to adhere to inanimate surfaces via biofilms. Alarmingly, S. epidermidis has acquired resistance to many antibiotics, which presents a danger to human health. Known as methicillin-resistant S. epidermidis (MRSE), most clinical isolates of MRSE in North America exhibit β-lactam resistance primarily due to the presence of mecA, a gene that bestows β-lactam antibiotic resistance in a manner similar to methicillin-resistant Staphylococcus aureus (MRSA). MecA encodes for expression of penicillin-binding protein 2a (PBP2a), which is absent in β-lactam susceptible strains of S. epidermidis. We can disable this resistance factor in MRSE with 600-Da branched polyethylenimine (BPEI). Cationic BPEI targets anionic wall teichoic acid (WTA), an essential cofactor for proper functioning of PBP2a. We found that BPEI synergizes the activity of β-lactam antibiotics against MRSE. Growth curves suggest that the combination of BPEI and oxacillin is bactericidal. Electron micrographs indicate abnormalities in the cellular septa and cell walls of treated samples. Therefore, first-line clinical treatments can be effective against MRSE when used in combination with BPEI.

Clonal Emergence of Invasive Multidrug-Resistant Staphylococcus epidermidis Deconvoluted via a Combination of Whole-Genome Sequencing and Microbiome Analyses

Background

Pathobionts, bacteria that are typically human commensals but can cause disease, contribute significantly to antimicrobial resistance. Staphylococcus epidermidis is a prototypical pathobiont as it is a ubiquitous human commensal but also a leading cause of healthcare-associated bacteremia. We sought to determine the etiology of a recent increase in invasive S. epidermidis isolates resistant to linezolid.

Methods

Whole-genome sequencing (WGS) was performed on 176 S. epidermidis bloodstream isolates collected at the MD Anderson Cancer Center in Houston, Texas, between 2013 and 2016. Molecular relationships were assessed via complementary phylogenomic approaches. Abundance of the linezolid resistance determinant cfr was determined in stool samples via reverse-transcription quantitative polymerase chain reaction.

Results

Thirty-nine of the 176 strains were linezolid resistant (22%). Thirty-one of the 39 linezolid-resistant S. epidermidis infections were caused by a particular clone resistant to multiple antimicrobials that spread among leukemia patients and carried cfr on a 49-kb plasmid (herein called pMB151a). The 6 kb of pMB151a surrounding the cfr gene was nearly 100% identical to a cfr-containing plasmid isolated from livestock-associated staphylococci in China. Analysis of serial stool samples from leukemia patients revealed progressive staphylococcal domination of the intestinal microflora and an increase in cfr abundance following linezolid use.

Conclusions

The combination of linezolid use plus transmission of a multidrug-resistant clone drove expansion of invasive, linezolid-resistant S. epidermidis. Our results lend support to the notion that a combination of antibiotic stewardship plus infection control measures may help to control the spread of a multidrug-resistant pathobiont.

Molecular Epidemiology of Staphylococcus epidermidis Implicated in Catheter-Related Bloodstream Infections at an Academic Hospital in Pretoria, South Africa

Staphylococcus epidermidis is one of the most prevalent pathogens implicated in catheter-related bloodstream infections (CRBSI) at an academic hospital in Pretoria, South Africa. Little is known about the clonality and the prevalence of antibiotic resistance and virulence genes in S. epidermidis (e.g., icaAB, IS256, mecA, and qacA/B). A total of 508 intravascular catheters (IVCs) from 331 patients were submitted for culture from May to October 2013. Only 50% (n = 253/508) of the IVCs were accompanied by blood cultures (BCs) taken within 48 h. Forty-four percent (44%; n = 112/253) of IVCs were colonised, of which 26% (n = 65/253) were associated with a CRBSI. We identified S. epidermidis as the causal agent in 31% (n = 20/65) of the CRBSI cases. Fifty-nine S. epidermidis isolates were obtained, 23 isolates were cultured from 22 IVCs and 36 isolates were cultured from 36 BCs. All S. epidermidis isolates were resistant to β-lactams (100%; n = 59/59), followed by high levels of resistance toward erythromycin (86%; n = 51/59) and gentamicin (81%; n = 49/59). The mecA gene was prevalent in all the (100%, n = 59/59) isolates. Isolates contained the IS256 element (83%, n = 49/59), the icaAB gene (81%, n = 48/59) and, the qacA/B gene (81%, n = 48/59). All 48 isolates were qacA positive upon restriction enzyme digestion of the qacA/B amplicons. Phenotypic resistance toward 0.5% (m/v) chlorhexidine was not observed. Staphylococcal Cassette Chromosome (SCC) mec typing showed that SCCmec type IV (31%; n = 18/59) was the most prevalent. The remaining SCCmec elements were highly diverse. Pulsed-field gel electrophoresis (PFGE) showed that S. epidermidis isolates from individual patients were mostly clonal. Multilocus sequencing typing (MLST) of 10 sequenced isolates showed that sequence type (ST) 2 (40%; n = 4/10) was the most frequently detected, followed by ST54 (20%; n = 2/10), ST28 (10%; n = 1/10), ST59 (10%; n = 1/10) and ST490 (10%; 1/10). One isolate was newly assigned to ST596. These S. epidermidis infections can be attributed to patients' skin microflora or to poor infection control practices. Currently, S. epidermidis strains circulating in the studied hospital are multidrug-resistant and highly adaptive to environmental changes.

SesI May Be Associated with the Invasiveness of Staphylococcus epidermidis

Staphylococcus epidermidis is a commensal bacterium which widely colonizes in human skin and mucous membrane and rarely causes clinically manifested infections. S. epidermidis surface protein I (SesI) is considered to be the major virulence factor of S. epidermidis infection, but its pathogenesis is not clear. Here, we demonstrated that the prevalence of sesI among S. epidermidis invasive isolates (20.8%, 26/125) was significantly higher than that among colonizing isolates (3.8%, 4/106). The positive rates of biofilm-associated genes (aap, icaA, IS256) and resistance-associated genes mupA among the sesI-positive isolates were significantly higher than those among sesI-negative isolates (p < 0.05). And antimicrobial susceptibility testing showed that the resistance rates of sesI-positive isolates to ciprofloxacin, gentamicin and trimethoprim/sulfamethoxazole were significantly higher than those among sesI-negative isolates. Interestingly, 80.8% (21/26) of sesI-positive isolates belong to ST2 determined by MLST, while ST2 was not found among any of the 99 sesI-negative invasive isolates, indicating that there is a strong association between carriage of sesI and ST2 clone. In order to further study the role of sesI gene in pathogenesis, the sesI gene mutant (S. epidermidis RP62AΔsesI) and complementary expression strain (S. epidermidis RP62AΔsesI-C) were successfully constructed. All experimental data indicated that sesI may promote S. epidermidis to adhere and aggregate, but it had no obvious effect on the mature stage of biofilm formation. Taken together, these results suggest that sesI, along with antimicrobial and other biofilm-associated genes enables S. epidermidis easier for colonization and adhesion and contributes to the spread of S. epidermidis, especially ST2 clone.

Bacteria antibiotic resistance: New challenges and opportunities for implant-associated orthopedic infections

There has been a dramatic increase in the emergence of antibiotic-resistant bacterial strains, which has made antibiotic choices for infection control increasingly limited and more expensive. In the U.S. alone, antibiotic-resistant bacteria cause at least 2 million infections and 23,000 deaths a year resulting in a $55-70 billion per year economic impact. Antibiotics are critical to the success of surgical procedures including orthopedic prosthetic surgeries, and antibiotic resistance is occurring in nearly all bacteria that infect people, including the most common bacteria that cause orthopedic infections, such as Staphylococcus aureus (S. aureus). Most clinical cases of orthopedic surgeries have shown that patients infected with antibiotic-resistant bacteria, such as methicillin-resistant S. aureus (MRSA), are associated with increased morbidity and mortality. This paper reviews the severity of antibiotic resistance at the global scale, the consequences of antibiotic resistance, and the pathways bacteria used to develop antibiotic resistance. It highlights the opportunities and challenges in limiting antibiotic resistance through approaches like the development of novel, non-drug approaches to reduce bacteria functions related to orthopedic implant-associated infections. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:22-32, 2018.