Characterization of Staphylococcus caprae Clinical Isolates Involved in Human Bone and Joint Infections, Compared with Goat Mastitis Isolates

Dalbavancin-resistant Staphylococcus epidermidis in vivo selection following a prosthetic joint infection: phenotypic and genomic characterization

Background

Dalbavancin is a lipoglycopeptide antibiotic with a wide spectrum of activity against Gram-positive bacteria, including MDR isolates. Its pharmacokinetic properties and administration patterns could be useful for the treatment of bone and joint infections, especially prosthetic joint infections (PJIs).

Introduction

We report the case of an 80-year-old man who experienced an acute periprosthetic joint infection of his right total knee arthroplasty (TKA). A DAIR procedure was done with tissue sampling, which allowed identification of a linezolid-resistant MDR S. epidermidis (LR-MDRSE) strain. The patient was then treated with dalbavancin (four injections).

Methods

We studied the phenotypic and genomic evolution of the strains and plasma through concentrations of dalbavancin at different points in time.

Results

After four injections (1500 mg IV) of dalbavancin over a 6 month period, the dalbavancin MIC increased 4-fold. Calculated fAUC0-24/MIC ratios were 945, 1239 and 766.5, respectively, at Days 49, 71 and 106, assuming an MIC of 0.032 mg/L. The PFGE dendrogram revealed 97% similarity among all the isolates. These results suggest acquisition by the S. epidermidis strain of dalbavancin resistance when the patient underwent dalbavancin treatment. A 4-amino-acid deletion in the walK gene coinciding with the emergence of phenotypic resistance was revealed by WGS without any other relevant indels.

Conclusions

Despite dalbavancin treatment with pharmacokinetic management, emerging dalbavancin resistance in S. epidermidis was observed, resulting in treatment failure. This outcome led to a prosthesis revision and long-term suppressive antibiotic therapy, with no recurrence of PJI after an 18 month follow-up.

Phenotypic Variation in Staphylococcus aureus during Colonisation Involves Antibiotic-Tolerant Cell Types

Staphylococcus aureus is a bacterial species that is commonly found colonising healthy individuals but that presents a paradoxical nature: simultaneously, it can migrate within the body and cause a range of diseases. Many of these become chronic by resisting immune responses, antimicrobial treatment, and medical intervention. In part, this ability to persist can be attributed to the adoption of multiple cell types within a single cellular population. These dynamics in the S. aureus cell population could be the result of its interplay with host cells or other co-colonising bacteria-often coagulase-negative Staphylococcal (CoNS) species. Further understanding of the unique traits of S. aureus alternative cell types, the drivers for their selection or formation during disease, as well as their presence even during non-pathological colonisation could advance the development of diagnostic tools and drugs tailored to target specific cells that are eventually responsible for chronic infections.

Association of coagulase-negative staphylococci with orthopedic infections detected by in-house multiplex real-time PCR

Introduction

Clinical significance of coagulase-negative staphylococci (CoNS) has been gradually acknowledged in both healthcare and clinical research, but approaches for their precise discrimination at the species level remain scarce. The current study aimed to evaluate the association of CoNS with orthopedic infections, where accurate and prompt identification of etiology is crucial for appropriate diagnosis and treatment decision-making.

Methods

A 16S rRNA-based quantitative PCR (qPCR) assay was developed for the detection of Staphylococcus genus and two panels of 3-plex qPCR assays for further differentiation of six CoNS species with remarkable clinical significance, including S. epidermidis, S. haemolyticus, S. simulans, S. hominis, S. capitis, and S. caprae. All the assays exhibited excellent analytical performance. ΔCq (quantification cycle) between 16S rRNA and CoNS species-specific targets was established to determine the primary CoNS. These methods were applied to detect CoNS in wound samples from orthopedic patients with and without infection.

Results and discussion

Overall, CoNS were detected in 17.8% (21/118) of patients with clinically suspected infection and in 9.8% (12/123) of patients without any infection symptom (p < 0.05). Moreover, the association with infection was found to be bacterial quantity dependent. S. epidermidis was identified as the predominant species, followed by S. simulans, S. haemolyticus, and S. hominis. Male sex, open injury, trauma, and lower extremity were determined as risk factors for CoNS infections. CoNS-positive patients had significantly longer hospitalization duration (20 days (15, 33) versus 13 days (7, 22) for Staphylococcus-negative patients, p = 0.003), which could be a considerable burden for healthcare and individual patients. Considering the complex characteristics and devastating consequences of orthopedic infections, further expanding the detection scope for CoNS may be pursued to better understand the etiology of orthopedic infections and to improve therapeutic strategies.

A capricious case of Staphylococcus caprae thoracic osteomyelitis

Staphylococcus caprae (S. caprae) is a gram positive, coagulase-negative Staphylococci (CoNS) that occurs as a commensal pathogen on the human skin. It recently has been recognized in causing nosocomial infections involving the bloodstream, urinary tract, heart, bone, and joints, particularly in immunosuppressed patients or individuals with prosthetic devices. Previously, S. caprae was underreported as it was difficult to identify in the clinical microbiology laboratory; however, due to advances in molecular identification methods and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), more clinical cases are being identified in human isolates and appropriately treated. S. caprae osteoarticular infections are usually associated with polymicrobial infections and presence of orthopedic prostheses in immunocompromised adults. This pathogen has an even rarer presentation of bone and joint infections (BJIs) in immunocompetent individuals without orthopedic devices. Our case is of a 65-year-old immunocompetent male with diet-controlled diabetes mellitus type 2 and end-stage renal disease (ESRD) on hemodialysis who presented with worsening mid-thoracic pain after a ground-level fall and was diagnosed with biopsy-proven S. caprae thoracic discitis/osteomyelitis, associated with recurrent catheter-related bloodstream infection (CRBSI). It illustrates the importance of recognizing S. caprae as an emerging human pathogen, even in immunocompetent individuals without orthopedic hardware, requiring prompt targeted treatment of native BJIs to prevent unfavorable outcomes.

The composition of the maternal breastmilk microbiota influences the microbiota network structure during early infancy

BACKGROUND/PURPOSE(S)

Human breastmilk (BM) is important for microbiome maturation in infants across different body sites. Streptococcus and Staphylococcus are considered universally predominant genera in the BM microbiota. However, whether the differential abundance of Streptococcus and Staphylococcus in BM can differentially affect microbiome maturation in infants remains unclear.

METHODS

We recruited exclusively breastfeeding mothers from among the donors of the human milk bank established at National Cheng-Kung University Hospital. The donor mothers provided 35 BM samples at three months (3 M; before introducing children to complementary feeding) and 23 BM samples at six months (6 M; after introducing children to complementary feeding) postpartum. At both time points, samples from different body sites, including nasal swabs, oral swabs and stool, were collected from the mothers and their infants.

RESULTS

Maternal BMI was inversely associated with coagulase-negative Staphylococcus (CoNS) abundance in breastmilk. Staphylococcus caprae representation in BM CoNS showed a negative correlation with Streptococcus abundance. Network analysis revealed that infants fed Staphylococcus-dominated BM had better gut and nasal microbiota networks than infants fed Streptococcus-abundant BM during early infancy.

CONCLUSION

Our work suggests that maternal metabolic status plays a crucial role in Staphylococcus/Streptococcus competition in BM, which in turn can impact the development of the infant microbiota. Our microbiota co-occurrence network analysis might serve as a helpful bioinformatic tool to monitor microbiota maturation during early infancy.

Upregulation of ica Operon Governs Biofilm Formation by a Coagulase-Negative Staphylococcus caprae

Staphylococcus caprae is a Gram-positive, coagulase-negative staphylococci (CoNS), which appears as commensal in the skin, as well as a prevalent mastitis pathogen of goats. Occasionally, it is also associated with infections in humans. Biofilm formation has been identified as a putative virulence factor in S. caprae. Biofilms are multicellular communities protected by a self-produced extracellular matrix (ECM), which facilitates the resistance of bacterial cells to antimicrobial treatments. The ECM is constructed by exopolysaccharides, including the major exopolysaccharide-polysaccharide intercellular adhesion (PIA), regulated by the ica operon in Staphylococcus species. The aim of this study was to characterize the expression of the ica operon in relation to biofilm formation in S. caprae. Results showed that within a few hours of growth, S. caprae could adhere to polystyrene surfaces, start to accumulate, and form biofilm. Peak biofilm biomass and maturation were reached after 48 h, followed by a reduction in biomass after 72 h. Confocal laser scanning microscopy showed the expression of matrix-associated proteins and polysaccharides at various time points. The expression dynamics of the ica operon were investigated using real-time reverse transcriptase PCR (RT)-qPCR, which showed elevated expression during the early stages of biofilm formation and subsequent downregulation throughout the biofilm aging process. In conclusion, our results show that the ica operon is essential in regulating biofilm formation in S. caprae, similar to other Staphylococcus species. Furthermore, the robustness of the observed biofilm phenotype could account for the successful intramammary colonization and may explain disease persistence caused by this pathogenic bacterium.

Leveraging molecular docking to understand Congo red degradation by Staphylococcus caprae MB400

Congo red (CR) is a genotoxic, sulphonated azo dye and poses significant pollution problem. We hereby report its degradation by Staphylococcus caprae MB400. The bacterium initially propagated as a suspected contaminant upon CR dye supplemented nutrient agar plates, forming zones of clearance around its growth area. The bacterium was purified, gram stained and identified as Staphylococcus caprae via 16S rRNA gene sequencing. Dye decolourization was analysed in liquid culture, and Fourier-transform infrared spectroscopy (FTIR) was conducted for analysis of degraded product/metabolites. A decolourization of ~ 96.0% at 100 µg/ml concentration and pH 7 after 24 h of incubation was observed. Structure of the azoreductase enzyme, responsible for breakage of the bond in the dye and ultimately decolourization, was predicted, and molecular docking was harnessed for understanding the mechanism behind the reduction of azo bond (-N=N-) and conversion to metabolites. Our analysis revealed 12 residues critical for structural interaction of the azoreductase enzyme with this dye. Among these, protein backbone region surrounding four residues, i.e. Lys65, Phe122, Ile166 and Phe169, showed major displacement changes, upon binding with the dye. However, overall the conformational changes were not large.

A Rare Case of Staphylococcus caprae-Caused Periprosthetic Joint Infection Following Total Hip Arthroplasty: A Literature Review and Antibiotic Treatment Algorithm Suggestion

In this study, we discuss a case of a 59-year-old male who developed a periprosthetic joint infection (PJI) three months after a total hip arthroplasty (THA). The patient complained of groin and buttock pain, swelling, and high temperature. A palpable fluid collection, discomfort, edema, and elevated local temperature were present in the clinical examination. Laboratory analysis revealed elevated white blood cells, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). The preoperative joint aspiration came up positive for Staphylococcus caprae (S. caprae) infection. Diagnosis and pathogen identification were confirmed by histological examination of six tissue samples obtained during surgery. We initially performed early debridement, antibiotics, and implant retention (DAIR) followed by antibiotic therapy suggested by an infectious disease specialist. DAIR failed two months later, and we proceeded to a two-stage revision. Following surgery, the patient was treated with intravenous antibiotic combination therapy for three weeks and thereafter with oral antibiotics for three months. Four months down the line, the patient is free of symptoms, and the inflammatory markers are normal. Finally, we will proceed with the second stage of revision. This study highlights a very rare case of PJI infection by S. caprae, reviews the limited literature, and provides the available evidence for surgical and antibiotic management.

Importance of Staphylococcus epidermidis findings in the blood and cerebrospinal fluid of a full-term newborn: a case report

Methicillin-resistant Staphylococcus epidermidis (MRS) predominantly colonizes the skin and mucous membranes of humans and other animals. We describe the case of a male newborn of gestational age 39 weeks whose primary and repeated blood cultures and cerebrospinal fluid samples isolated MRS. The choice and duration of antibiotic therapy were determined by the clinical presentation, infection parameters, and results of bacteriological analyses of blood and cerebrospinal fluid samples obtained from the newborn on the day 5 of life. After 28 days of antibiotic therapy for sepsis accompanied by meningitis, the newborn was discharged home without sequelae.

Characteristics and genome analysis of a novel bacteriophage IME1323_01, the first temperate bacteriophage induced from Staphylococcus caprae

Temperate phages play an important role in the evolution of bacteria. So far, lytic phages have been wildly reported, but there is still limited knowledge regarding temperate phages in the genome of pathogenic Staphylococcus caprae. Here we present the characteristics and genome analysis of a novel bacteriophage IME1323_01, which is the first isolated bacteriophage of S. caprae. The phage genome is a 44282-bp linear dsDNA molecule with a GC content of 34.18%, which is similar to its host. The genome of IME1323_01 is most closely related with that of temperate phage IME1318_01, whereas the homology coverage is just 34%. Genome and proteome analyses confirmed the lysogenic nature of phage IME1323_01, which encodes the typical lysogen-related proteins integrase, CI, Cro, and anti-repressor proteins. Genomic and phylogenetic analysis revealed that phage IME1323_01 is a newly discovered phage, which belongs to subfamily Azeredovirinae in the family Siphoviridae. The goal of this study is to increase our knowledge about the phages of S. caprae and expand our armamentarium against the escalating threat of pathogenic bacteria.

A Rare Case of Extremely Severe Heterotopic Ossification after Primary Total Hip Arthroplasty due to Persistent Mild Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) caused by coagulase-negative staphylococci (CNS) can be a mild, persisting infection. Although heterotopic ossification (HO) is common following total hip arthroplasty (THA), the etiology of severe HO remains unclear. Herein, we describe a rare case of extremely severe HO after a PJI associated with a Staphylococcus caprae infection in a 78-year-old male patient. The patient had poorly controlled diabetes mellitus with no diabetic complications. The patient had no previous history of hip surgery, hip injury, or systemic bacterial infection. Immediately after the initial THA, he developed intermittent low-grade fever (37°C), which persisted for 3 months; consequently, he also reported mild hip pain during walking. He experienced a gradual decrease in hip range of motion within 5 years after the surgery, with progressive gait impairment. Two revision surgeries were required for the successful treatment of this difficult case. The patient's hip function improved, and the PJI was controlled following the second revision surgery. Based on the clinical course, CNS-caused PJI may lead to severe HO. This possibility warrants verification from an accumulated number of cases.

Beneficial effects of coagulase-negative Staphylococci on Staphylococcus aureus skin colonization

Our skin is constantly exposed to a large number of pathogens while at the same time undergoing selective colonization by commensal microorganisms such as coagulase-negative Staphylococci. Staphylococcus aureus, however, is a facultative pathogen that is usually absent from healthy skin but frequently colonizes the inflamed skin of atopic dermatitis patients, where it further promotes inflammation. Enhanced S. aureus skin colonization was shown to correlate with a loss of microbiome diversity indicating a role for skin commensals to shape pathogen colonization. Together, keratinocytes and immune cells in the skin need to discriminate commensals from pathogens and orchestrate subsequent immune reactions in response to colonizing microbes. However, the mechanisms how individual commensals cooperate with keratinocytes and the immune system of the skin to prevent pathogen colonization are barely understood. In this review, we discuss the current knowledge on the functional effects of coagulase-negative staphylococci, the most frequently isolated skin commensals, on S. aureus skin colonization.

A rare lumbar pyogenic spondylodiscitis caused by staphylococcus caprae with initial misdiagnosis: case report and literature review

Background

Staphylococcus caprae (Sc) is an uncommon causative organism for human. Lumbar pyogenic spondylodiscitis (LPS) of Sc is extremely rare and only a few cases have been reported. As far as we know, there is no specific literature on the diagnosis and treatment for LPS of Sc with L5 nerve root irritation.

Case presentation

A 65-year-old male patient complained of chronic low back pain for 10 years, acute worsening with radiating pain to left lower extremity over a month. Physical examination revealed tenderness point on his low back, 3/5 dorsiflexor strength in his left 1st toe and decreased sensation of pin prick over the left lateral shank and medial dorsal foot. The individual was initially misdiagnosed with lumbar disc herniation (LDH) without further examination in outpatient, which was then found to be LPS of Sc with L5 nerve root irritation after admission to our hospital. Magnetic resonance images (MRI) of lumbar spine exhibited inflammation signal at L4-L5 level of the vertebral body and disc with hypointense on T1-weighted images (T1-WI) and hyperintense on T2-weighted images (T2-WI). The causative organism was confirmed by the culture of irrigation fluid obtained from L5 vertebrae by needle puncture. After systemic conservative treatment including using sensitive antimicrobial agents and immobilization, the rare infection was finally cured. The patient also showed a satisfactory recovery during the 36-month follow-up period.

Conclusions

Confirming the diagnosis and identifying the causative organism as soon as possible is the key point for the treatment of LPS. LPS of Sc causing nerve root irritation is rare but curable with early diagnosis and proper therapy. The culture of irrigation fluid obtained from vertebrae by needle puncture may be an effective and sensitive attempt for potential infection of spine to identify the causative organism at early stage of the disease.

Misidentification of Cutibacterium namnetense as Cutibacterium acnes among clinical isolates by MALDI-TOF VitekMS: usefulness of gyrB sequencing and new player in bone infections

The taxonomy modification of Propionibacterium sp. with the description of new species, especially Cutibacterium namnetense, raises the question of species distribution in routine clinical samples. We performed a retrospective study during 3 years before the implementation of MALDI-TOF. Two hundred sixty-nine isolates were included in the study. MALDI-TOF identification, 16S rRNA, and new developed gyrB partial sequencings were performed. The most representative species was C. acnes in 88% of the cases, regardless of the origin of the clinical sample. Eventually, we identified three C. namnetense strains, representing a 1.1% prevalence over the period of time, including two bone infections. MALDI-TOF databases should be regularly updated to incorporate new species. gyrB sequencing constitutes a both easy and relevant method to identify Cutibacterium sp. especially C. namnetense, a new player in bone infections.

Skin Microbiome Differences in Atopic Dermatitis and Healthy Controls in Egyptian Children and Adults, and Association with Serum Immunoglobulin E

Atopic dermatitis (AD) is a complex, multifactorial, chronic pruritic inflammatory skin disease. We report the first microbiome study and new insights on the relationship between skin microbiota variation and AD susceptibility in a population sample from Egypt. We characterized the skin microbiome in 75 patients with AD and 20 healthy controls using Illumina MiSeq sequencing of 16S rRNA gene. Overall, bacterial diversity of skin microbiome in patients with AD was less than those of the healthy subjects. Genus level analysis revealed significant abundance variations by age, disease severity, locality, or immune response. Among these genera, Streptococcus, Cutibacterium, and Corynebacterium appeared to be specific signatures for AD in children, adolescents, and adults, respectively, while Staphylococcus was noted as a potential biomarker candidate for AD. Additionally, functional potential of metagenomes shifted the overall metabolic pathways to participate in the exacerbation of disease. Total immunoglobulin E (IgE) levels were positively correlated with relative enrichment of certain Staphylococcus aureus subspecies. Finally, AD-related differences in skin bacterial diversity appeared to be in part linked to the serum IgE level. These new observations attest to the promise of microbiome science and metagenomic analysis in AD specifically, and clinical dermatology broadly.

Propionibacterium/Cutibacterium species-related positive samples, identification, clinical and resistance features: a 10-year survey in a French hospital

A 10-year retrospective study of Propionibacterium/Cutibacterium-positive samples gathered from hospitalized patients was conducted at Nantes University hospital. A total of 2728 Propionibacterium/Cutibacterium-positive samples analyzed between 2007 and 2016 were included. Due to the implementation of MALDI-TOF identification in 2013, most non-Cutibacterium acnes isolates were identified a second time using this technology. Over that period, Cutibacterium acnes remained the most predominant species accounting for 91.5% (2497/2728) of the isolates, followed by Cutibacterium avidum (4.2%, 115/2728) and Cutibacterium granulosum (2.4%, 64/2728). Regarding the origin of samples, the orthopaedic department was the main Cutibacterium sample provider representing 51.9% (1415/2728) of all samples followed by the dermatology department (11.5%, 315/2728). Samples were recovered from various tissue locations: 31.5% (858/2728) from surgery-related samples such as shoulder, spine or hip replacement devices and 19.1% (520/2728) from skin samples. MALDI-TOF method revealed misidentification before 2013. Cutibacterium avidum was falsely identified as C. granulosum (n = 33). Consequently, MALDI-TOF technology using up-to-date databases should be preferred to biochemical identification in order to avoid biased species identification. Regarding antibiotic resistance, 14.7% (20/136) of C. acnes was resistant to erythromycin. 4.1% (41/1005) of C. acnes strains, 17.9% (12/67) of C. avidum strains and 3.6% (1/28) of C. granulosum strains were found resistant to clindamycin.

Coagulase-Negative Staphylococci Pathogenomics

Coagulase-negative Staphylococci (CoNS) are skin commensal bacteria. Besides their role in maintaining homeostasis, CoNS have emerged as major pathogens in nosocomial settings. Several studies have investigated the molecular basis for this emergence and identified multiple putative virulence factors with regards to Staphylococcus aureus pathogenicity. In the last decade, numerous CoNS whole-genome sequences have been released, leading to the identification of numerous putative virulence factors. Koch’s postulates and the molecular rendition of these postulates, established by Stanley Falkow in 1988, do not explain the microbial pathogenicity of CoNS. However, whole-genome sequence data has shed new light on CoNS pathogenicity. In this review, we analyzed the contribution of genomics in defining CoNS virulence, focusing on the most frequent and pathogenic CoNS species: S. epidermidis, S. haemolyticus, S. saprophyticus, S. capitis, and S. lugdunensis.

Staphylococcus caprae: A Skin Commensal with Pathogenic Potential

Staphylococcus caprae (S. caprae) is a catalase-positive, coagulase-negative organism that was first isolated from goat milk, and was later found to colonize healthy human skin, nails, and nasal mucosa. Rarely, this commensal organism can become pathogenic in humans. S. caprae has been implicated in a variety of human infections, with the highest incidence being in bone and joint infections. We describe a man who, after receiving facet joint injections for back pain, developed native vertebral discitis, vertebral osteomyelitis with phlegmon, and bilateral psoas abscesses, from which S. caprae was isolated.

Clinical and Biological Features of Cutibacterium (Formerly Propionibacterium) avidum, an Underrecognized Microorganism

The recent description of the genus Cutibacterium has altered the taxonomy of Propionibacterium species. These organisms still belong to the genera of the skin coryneform group, and the most-studied species remains Cutibacterium acnes. Cutibacterium avidum is also a known skin commensal. This underrecognized microorganism can, however, act as a pathogen after bacterial seeding and can be considered opportunistic, causing either superficial or deep/invasive infections. It can cause numerous infections, including but not limited to breast infections, skin abscesses, infective endocarditis, and device-related infections. The ecological niche of C. avidum is clearly different from that of other members of the genus: it is found in the axillary region or at wet sites rather than in dry, exposed areas, and the number of microorganisms increases during puberty. Historically, it has been used for its ability to modulate the immune response and for its antitumor properties. Conventional microbial culture methods and identification processes allow for its accurate identification and characterization. Thanks to the modern omics tools used for phylogenomic approaches, understanding C. avidum pathogenesis (including host-bacterium interactions and virulence factor characterization) is becoming easier, allowing for more thorough molecular characterization. These analyses have revealed that C. avidum causes diverse diseases mediated by multiple virulence factors. The recent genome approach has revealed specific genomic regions within this species that are involved in adherence and biofilm formation as well as fitness, survival, and defense functions. Numerous regions show the presence of phages and horizontal gene transfer. C. avidum remains highly sensitive to a broad spectrum of antibiotics, such as β-lactams, fluoroquinolones, macrolides, and rifampin, although erythromycin and clindamycin resistance has been described. A long-term treatment regimen with a combination of antibiotics is required to successfully eliminate the remaining adherent bacteria, particularly in the case of deep infections after debridement surgery.

Crossed Wires: Interspecies Interference Blocks Pathogen Colonization

Commensal bacteria protect against invading pathogens using many strategies. In this issue of Cell Host & Microbe, Paharik et al. (2017) find that a commensal blocks Staphylococcus aureus colonization by producing a signal to shut down virulence.

Staphylococcus caprae bacteraemia and native bone infection complicated by therapeutic failure and elevated MIC: a case report

Introduction.Staphylococcus caprae is a coagulase-negative staphylococcus that has been reported in several cases as a human pathogen. However, it has rarely been reported as pathogen in native bone. Furthermore, the reported MIC levels noted in the literature for vancomycin were <2 µg ml⁻¹making vancomycin a first line choice for infected patients.

Case presentation. We report a case of Staphylococcus caprae causing osteomyelitis of the lumbar spine and bacteraemia and resulting in sepsis and ultimately the demise of a patient despite appropriate prolonged antibiotic therapy.

Conclusion.Staphylococcus caprae has been reported as a human pathogen since 1983 when it was discovered. We report a case involving native bone infection which is rare in the absence of mechanical hardware. Furthermore, this strain had an elevated MIC for vancomycin which has not been reported in the literature.

In vitro emergence of fluoroquinolone resistance in Cutibacterium (formerly Propionibacterium) acnes and molecular characterization of mutations in the gyrA gene

In vitro occurrence of levofloxacin (LVX) resistance in C. acnes and characterization of its molecular background were investigated. The mutation frequency was determined by inoculation of 10⁸ cfu of C. acnes ATCC 11827 (LVX MIC = 0.25 mg/L) on LVX-containing agar plates. The progressive emergence of resistance was studied by a second exposure to increasing LVX concentrations. For mutants, the QRDR regions including the gyrA and parC genes were sequenced and compared to both C. acnes ATCC 11827 and C. acnes KPA171202 reference sequences (NC006085). The importance of the efflux pump system in resistance was investigated by using inhibitors on selected resistant mutants with no mutation in the QRDR. C. acnes growth was observed on LVX-containing plates with mutation frequencies of 3. 8 cfu × 10^-8 (8 × MIC) and 1.6 cfu × 10^-7 (4 × MIC). LVX resistance emerged progressively after one-step or two-step assays. In LVX-resistant isolates, the MIC ranged from 0.75 to >32 mg/L. Mutations were detected exclusively in the gyrA gene. Ten genotypes were identified: G99 C, G99 D, D100N, D100 H, D100 G, S101L, S101W, A102 P, D105 H and A105 G. Mutants S101L and S101W were always associated with a high level of resistance. Mutants with no mutation in the QRDR were more susceptible when incubated with an efflux pump inhibitor (phenyl-arginine β-naphthylamide) only, suggesting, for the first time, the expression of such a system in C. acnes LVX-resistant mutants.

Staphylococcus capitis isolated from prosthetic joint infections

Further knowledge about the clinical and microbiological characteristics of prosthetic joint infections (PJIs) caused by different coagulase-negative staphylococci (CoNS) may facilitate interpretation of microbiological findings and improve treatment algorithms. Staphylococcus capitis is a CoNS with documented potential for both human disease and nosocomial spread. As data on orthopaedic infections are scarce, our aim was to describe the clinical and microbiological characteristics of PJIs caused by S. capitis. This retrospective cohort study included three centres and 21 patients with significant growth of S. capitis during revision surgery for PJI between 2005 and 2014. Clinical data were extracted and further microbiological characterisation of the S. capitis isolates was performed. Multidrug-resistant (≥3 antibiotic groups) S. capitis was detected in 28.6 % of isolates, methicillin resistance in 38.1 % and fluoroquinolone resistance in 14.3 %; no isolates were rifampin-resistant. Heterogeneous glycopeptide-intermediate resistance was detected in 38.1 %. Biofilm-forming ability was common. All episodes were either early post-interventional or chronic, and there were no haematogenous infections. Ten patients experienced monomicrobial infections. Among patients available for evaluation, 86 % of chronic infections and 70 % of early post-interventional infections achieved clinical cure; 90 % of monomicrobial infections remained infection-free. Genetic fingerprinting with repetitive sequence-based polymerase chain reaction (rep-PCR; DiversiLab®) displayed clustering of isolates, suggesting that nosocomial spread might be present. Staphylococcus capitis has the potential to cause PJIs, with infection most likely being contracted during surgery or in the early postoperative period. As S. capitis might be an emerging nosocomial pathogen, surveillance of the prevalence of PJIs caused by S. capitis could be recommended.