The first genomic characterization of a stable, hemin-dependent small colony variant strain of Staphylococcus epidermidis isolated from a prosthetic-joint infection.

Phenotype switching from a wild type (WT) to a slow-growing subpopulation, referred to as small colony variants (SCVs), supports an infectious lifestyle of Staphylococcus epidermidis, the leading cause of medical device-related infections. Specific mechanisms underlying formation of SCVs and involved in the shaping of their pathogenic potential are of particular interest for stable strains as they have been only rarely cultured from clinical specimens. As the SCV phenotype stability implies the existence of genetic changes, the whole genome sequence of a stable, hemin-dependent S. epidermidis SCV strain (named 49SCV) involved in a late prosthetic joint infection was analyzed. The strain was isolated in a monoculture without a corresponding WT clone, therefore, its genome was compared against five reference S. epidermidis strains (ATCC12228, ATCC14990, NBRC113846, O47, and RP62A), both at the level of the genome structure and coding sequences. According to the Multilocus Sequence Typing analysis, the 49SCV strain represented the sequence type 2 (ST2) regarded as the most prominent infection-causing lineage with a worldwide dissemination. Genomic features unique to 49SCV included the absence of the Staphylococcal Cassette Chromosome (SCC), ~12 kb deletion with the loss of genes involved in the arginine deiminase pathway, and frameshift-generating mutations within the poly(A) and poly(T) homopolymeric tracts. Indels were identified in loci associated with adherence, metabolism, stress response, virulence, and cell wall synthesis. Of note, deletion in the poly(A) of the hemA gene has been considered a possible trigger factor for the phenotype transition and hemin auxotrophy in the strain. To our knowledge, the study represents the first genomic characterization of a clinical, stable and hemin-dependent S. epidermidis SCV strain. We propose that previously unreported indels in the homopolymeric tracts can constitute a background of the SCV phenotype due to a resulting truncation of the corresponding proteins and their possible biological dysfunction. Streamline of genetic content evidenced by the loss of the SCC and a large genomic deletion can represent a possible strategy associated both with the SCV phenotype and its adaptation to chronicity.

Synergistic Antifungal Interactions between Antibiotic Amphotericin B and Selected 1,3,4-thiadiazole Derivatives, Determined by Microbiological, Cytochemical, and Molecular Spectroscopic Studies.

In recent years, drug-resistant and multidrug-resistant fungal strains have been more frequently isolated in clinical practice. This phenomenon is responsible for difficulties in the treatment of infections. Therefore, the development of new antifungal drugs is an extremely important challenge. Combinations of selected 1,3,4-thiadiazole derivatives with amphotericin B showing strong synergic antifungal interactions are promising candidates for such formulas. In the study, microbiological, cytochemical, and molecular spectroscopy methods were used to investigate the antifungal synergy mechanisms associated with the aforementioned combinations. The present results indicate that two derivatives, i.e., C1 and NTBD, demonstrate strong synergistic interactions with AmB against some Candida species. The ATR-FTIR analysis showed that yeasts treated with the C1 + AmB and NTBD + AmB compositions, compared with those treated with single compounds, exhibited more pronounced abnormalities in the biomolecular content, suggesting that the main mechanism of the synergistic antifungal activity of the compounds is related to a disturbance in cell wall integrity. The analysis of the electron absorption and fluorescence spectra revealed that the biophysical mechanism underlying the observed synergy is associated with disaggregation of AmB molecules induced by the 1,3,4-thiadiazole derivatives. Such observations suggest the possibility of the successful application of thiadiazole derivatives combined with AmB in the therapy of fungal infections.

MicroRNA hsa-let-7a facilitates staphylococcal small colony variants survival in the THP-1 macrophages by reshaping inflammatory responses.

Recent studies have provided emerging evidence of the critical involvement of microRNAs in host immune defence against bacterial infection and that likewise the expression of the miRNAs is profoundly impacted by a variety of pathogens to subvert the immune response. Here, we report the role of hsa-let-7a miRNA in response to Staphylococcus epidermidis Small Colony Variants infection. We also assessed whether the expression levels of inflammatory cytokines associated with the hsa-let-7a are manipulated by the pathogen and the effect of the IFN-γ priming on the expression of hsa-let-7a and the fate of SCVs/WTs in infected macrophages. A striking observation was the downregulation of the let-7a miRNA upon challenge of the THP-1 activated cells with the SCV isolates while no significant changes in expression were noticed after the infection of macrophages with their WT counterparts. Staphylococcus epidermidis WT and SCV strains were found to invade and survive in macrophages. A significant reduction in bacterial load for both phenotypes was observed in macrophages treated with let-7a mimic compared to untreated ones. Survival of WTs was augmented in cells treated with the inhibitor in 4 out of 5 strains as compared to the number of bacteria recovered from non-transfected cells. At the same time, let-7a inhibitor did not influence on the survival of SCVs in macrophages as their number was comparable to number recovered from non-transfected cells. When the ratio of both let-7a cytokine targets was compared, anti-inflammatory IL-10 cytokine was induced by SCVs predominantly, while the macrophage challenge with WTs was characterized by the inflammatory cytokine profile with high IL-6 and low IL-10 production. Moreover, the balance between pro-inflammatory and anti-inflammatory cytokines has been expectedly retrieved when macrophages were transfected with let-7a mimic before infection with WT or SCV strains. The results also show that IFN-γ likely regulates the macrophage environment contributing to the inflammatory response and elimination of bacteria from intracellular milieu by augmenting the synthesis of pro-inflammatory cytokines and supressing the anti-inflammatory IL-10. Our work has shown that SCVs have the potential to regulate the let-7a miRNA to balance the pro-inflammatory IL-6 with anti-inflammatory IL-10 and this mechanism is one of the ways in a complex regulatory network adopted by SCVs to promote their survival.

The road to success of coagulase-negative staphylococci: clinical significance of small colony variants and their pathogenic role in persistent infections.

Bacterial small colony variants represent an important aspect of bacterial variability. They are naturally occurring microbial subpopulations with distinctive phenotypic and pathogenic traits, reported for many clinically important bacteria. In clinical terms, SCVs tend to be associated with persistence in host cells and tissues and are less susceptible to antibiotics than their wild-type (WT) counterparts. The increased tendency of SCVs to reside intracellularly where they are protected against the host immune responses and antimicrobial drugs is one of the crucial aspects linking SCVs to recurrent or chronic infections, which are difficult to treat. An important aspect of the SCV ability to persist in the host is the quiescent metabolic state, reduced immune response and expression a changed pattern of virulence factors, including a reduced expression of exotoxins and an increased expression of adhesins facilitating host cell uptake. The purpose of this review is to describe in greater detail the currently available data regarding CoNS SCV and, in particular, their clinical significance and possible mechanisms by which SCVs contribute to the pathogenesis of the chronic infections. It should be emphasized that in spite of an increasing clinical significance of this group of staphylococci, the number of studies unraveling the mechanisms of CoNS SCVs formation and their impact on the course of the infectious process is still scarce, lagging behind the studies on S. aureus SCVs.

Evaluation of the role of staphylococci in the pathomechanism of conjunctivitis.

PURPOSE: Determination of the association between ica genes and phenotypic biofilm formation in staphylococcal isolates involved in conjunctivitis, their antibiotic resistance as well as detection of selected virulence characteristics: adhesion to epithelial cells and in vitro cytotoxicity. METHODS: The study included 26 Staphylococcus aureus (SA) and 26 Staphylococcus epidermidis (SE) isolates. The presence of icaAD genes and ica operon was determined by the PCR assay. Phenotypic biofilm formation was verified using the microtitre plate assay. Antibiotic resistance was performed using the disc diffusion method. Staphylococcal ability to attach to host cells was assessed by flow cytometry. Cytotoxicity on epithelial cells was evaluated by LDH assay. RESULTS: The ica genes were detected in 26.9% of SE and in 42.3% of SA isolates. Only 15.3% of isolates (SE) were positive for both the icaAD and the ica operon. Phenotypically, 19.2% of SE isolates were strong biofilm producers, among which three were both icaAD- and ica operon-positive. About 26.9% of SA isolates were strong biofilm producers. Methicillin resistance (MR) was detected in 34.6% of SE and 26.9% of SA isolates. About 75% of MR isolates were multidrug resistant. SA isolates adhered to host cells more extensively than SE. SA isolates released higher level of LDH than SE. CONCLUSIONS: Adherence abilities were commonly observed in staphylococci associated with conjunctivitis. However, low prevalence of isolates positive for a complete and functional ica locus and low prevalence of strong biofilm producers was detected. SA adhered to a greater extent to eukaryotic cells than SE and were more cytotoxic.

Tetracycline resistance in Moraxella catarrhalis clinical strains isolated in Poland.

Moraxella catarrhalis is considered an important, exclusively human respiratory tract pathogen which, along with Streptococcus pneumoniae and Haemophilus influenzae, is classified as one of the most frequent bacterial etiological factors causing upper respiratory tract infections. In this manuscript, we report the existence of five tetracycline-resistant M. catarrhalis strains with confirmed presence of tetracycline resistance tetB gene. The strains were isolated from children under the age of three with signs of upper respiratory tract infections. Our research also investigated the occurrence of virulence genes in these strains and involved the analysis of drug resistance to five antibiotic groups. It is the first description of clinical strains with confirmed presence of drug resistance tetB genes isolated in Europe.

Draft whole-genome sequence of Brevibacterium casei strain isolated from a bloodstream infection.

Despite its low virulence potential and a commensal lifestyle as a member of the human skin microbiota, Brevibacterium casei has been increasingly reported as an opportunistic pathogen, especially in immunocompromised patients. Here, we present the draft genome sequence of the S51 strain isolated from a bloodstream infection. To the best of the authors' knowledge, this is the first report of the draft genome sequence of the B. casei strain isolated from the clinical infection. The strain was identified using phenotypic and molecular methods and subsequently sequenced using the next-generation sequencing. The draft whole genome was assembled de novo, automatically annotated by Rapid Annotations using Subsystems Technology (RAST) server and scrutinized to predict the presence of virulence, resistance, and stress response proteins. The genome size of the S51 strain was 3,743,532 bp and an average G+C content was 68.3%. The predicted genes included 48 genes involved in resistance to antibiotics (including vancomycin, fluoroquinolones, and beta-lactams) and toxic compounds (heavy metals), 16 genes involved in invasion and intracellular resistance (Mycobacterium virulence operons), and 94 genes involved in stress response (osmotic, oxidative stress, cold and heat shock). ResFinder has indicated the presence of a beta-lactamase, and a phenotypic analysis showed resistance to penicillin. This whole-genome NGS project for the S51strain has been deposited at EMBL/GenBank under the accession no. QNGF00000000.

Cytokine Levels in the In Vitro Response of T Cells to Planktonic and Biofilm Corynebacterium amycolatum.

Unravelling of the interplay between the immune system and non-diphtheria corynebacteria would contribute to understanding their increasing role as medically important microorganisms. We aimed at the analysis of pro- (TNF, IL-1ß, IL-6, IL-8, and IL-12p70) and anti-inflammatory (IL-10) cytokines produced by Jurkat T cells in response to planktonic and biofilm Corynebacterium amycolatum. Two reference strains: C. amycolatum ATCC 700207 (R-CA), Staphylococcus aureus ATCC 25923 (R-SA), and ten clinical strains of C. amycolatum (C-CA) were used in the study. Jurkat T cells were stimulated in vitro by the planktonic-conditioned medium (PCM) and biofilm-conditioned medium (BCM) derived from the relevant cultures of the strains tested. The cytokine concentrations were determined in the cell culture supernatants using the flow cytometry. The levels of the cytokines analyzed were lower after stimulation with the BCM when compared to the PCM derived from the cultures of C-CA; statistical significance (p < 0.05) was observed for IL-1ß, IL-12 p70, and IL-10. Similarly, planktonic R-CA and R-SA stimulated a higher cytokine production than their biofilm counterparts. The highest levels of pro-inflammatory IL-8, IL-1ß, and IL-12p70 were observed after stimulation with planktonic R-SA whereas the strongest stimulation of anti-inflammatory IL-10 was noted for the BCM derived from the mixed culture of both reference species. Our results are indicative of weaker immunostimulatory properties of the biofilm C. amycolatum compared to its planktonic form. It may play a role in the persistence of biofilm-related infections. The extent of the cytokine response can be dependent on the inherent virulence of the infecting microorganism.Unravelling of the interplay between the immune system and non-diphtheria corynebacteria would contribute to understanding their increasing role as medically important microorganisms. We aimed at the analysis of pro- (TNF, IL-1ß, IL-6, IL-8, and IL-12p70) and anti-inflammatory (IL-10) cytokines produced by Jurkat T cells in response to planktonic and biofilm Corynebacterium amycolatum. Two reference strains: C. amycolatum ATCC 700207 (R-CA), Staphylococcus aureus ATCC 25923 (R-SA), and ten clinical strains of C. amycolatum (C-CA) were used in the study. Jurkat T cells were stimulated in vitro by the planktonic-conditioned medium (PCM) and biofilm-conditioned medium (BCM) derived from the relevant cultures of the strains tested. The cytokine concentrations were determined in the cell culture supernatants using the flow cytometry. The levels of the cytokines analyzed were lower after stimulation with the BCM when compared to the PCM derived from the cultures of C-CA; statistical significance (p < 0.05) was observed for IL-1ß, IL-12 p70, and IL-10. Similarly, planktonic R-CA and R-SA stimulated a higher cytokine production than their biofilm counterparts. The highest levels of pro-inflammatory IL-8, IL-1ß, and IL-12p70 were observed after stimulation with planktonic R-SA whereas the strongest stimulation of anti-inflammatory IL-10 was noted for the BCM derived from the mixed culture of both reference species. Our results are indicative of weaker immunostimulatory properties of the biofilm C. amycolatum compared to its planktonic form. It may play a role in the persistence of biofilm-related infections. The extent of the cytokine response can be dependent on the inherent virulence of the infecting microorganism.

A Novel Approach to Study the Effect of Ciprofloxacin on Biofilms of Corynebacterium spp. Using Confocal Laser Scanning Microscopy.

Non-diphtherial corynebacteria are Gram-positive rods that cause opportunistic infections, what is supported by their ability to produce biofilm on artificial surfaces. In this study, the characteristic of the biofilm produced on vascular and urological catheters was determined using a confocal microscopy for the most frequently involved in infections diphtheroid species. They were represented by the reference strains of Corynebacterium striatum ATCC 6940 and C. amycolatum ATCC 700207. The effect of ciprofloxacin on the biofilm produced by the antibiotic-susceptible C. striatum strain was evaluated using three concentrations of the antimicrobial agent (2 ×, 4 ×, and 6 × the MIC - the Minimum Inhibitory Concentration). The basis for the interpretation of results was the statistical analysis of maximum points readings from the surface comprising a total of 245 areas of the biofilm image under the confocal microscope. It was observed that ciprofloxacin at a concentration equal to 4 × MIC paradoxically caused an enlargement of areas with live bacteria within the biofilm. Biofilm destruction required the application of ciprofloxacin at a concentration higher than 6 × MIC. This suggests that the use of relatively low doses of antimicrobial agents may increase the number of live bacteria within the biofilm, and further facilitate their detachment from the biofilm's structure thus leading to the spread of bacteria into the bloodstream or to the neighboring tissues. The method of biofilm analysis presented here provides the original and novel approach to the investigation of the diphtheroid biofilms and their interaction with antimicrobial agents.Non-diphtherial corynebacteria are Gram-positive rods that cause opportunistic infections, what is supported by their ability to produce biofilm on artificial surfaces. In this study, the characteristic of the biofilm produced on vascular and urological catheters was determined using a confocal microscopy for the most frequently involved in infections diphtheroid species. They were represented by the reference strains of Corynebacterium striatum ATCC 6940 and C. amycolatum ATCC 700207. The effect of ciprofloxacin on the biofilm produced by the antibiotic-susceptible C. striatum strain was evaluated using three concentrations of the antimicrobial agent (2 ×, 4 ×, and 6 × the MIC ­ the Minimum Inhibitory Concentration). The basis for the interpretation of results was the statistical analysis of maximum points readings from the surface comprising a total of 245 areas of the biofilm image under the confocal microscope. It was observed that ciprofloxacin at a concentration equal to 4 × MIC paradoxically caused an enlargement of areas with live bacteria within the biofilm. Biofilm destruction required the application of ciprofloxacin at a concentration higher than 6 × MIC. This suggests that the use of relatively low doses of antimicrobial agents may increase the number of live bacteria within the biofilm, and further facilitate their detachment from the biofilm's structure thus leading to the spread of bacteria into the bloodstream or to the neighboring tissues. The method of biofilm analysis presented here provides the original and novel approach to the investigation of the diphtheroid biofilms and their interaction with antimicrobial agents.

Intraphagolysosomal conditions predispose to Staphylococcus epidermidis small colony variants persistence in macrophages.

Staphylococcus epidermidis small colony variants can survive inside macrophages and their survival has been proposed as a pivotal process in the pathogenesis of biomaterial associated infections. In the present study the intracellular location of clinical isolates of SCV and parental wild type strains inside macrophages was determined. Furthermore, the effect of IFN-γ and rapamycin on the level of SCV/WT as well as lysosomes colocalisation and iNOS induction in THP-activated macrophages in response to WT and SCV strains of Staphylococcus epidermidis were examined. It was demonstrated that SCV strain of S. epidermidis can survive and persist inside macrophages and its intracellular survival is supported by the induction of phagosomal acidification. The ability to reduce the high proportion of LysoTracker positive SCV containing phagosomes was exclusively found when IFN-γ was used. The findings suggest that IFN-γ mediates SCV killing via two distinct mechanisms, phagosome alkalisation and an increased iNOS synthesis, so the cytokine may control S. epidermidis WT and SCV infection in macrophages. Staphylococcus epidermidis SCV is a less potent stimulus of iNOS than the WT strain and the feature may help SCV to persist in hostile environment of macrophages. Rapamycin treatment did not influence the iNOS synthesis but reduced the percentage of both bacterial strains within acidic organelles. However, the percentage of SCV within LysoTracker positive organelles, even though reduced comparing to non-primed cells, was higher than in the WT strain indicating that Staphylococcus epidermidis possesses unique metabolic features allowing SCV to survive within macrophages.

The role of the PI3K/mTOR signaling pathway in Staphylococcus epidermidis small colony variants intracellular survival.

The objective of this study was to analyze how Staphylococcus epidermidis SCV and WT strains manipulate the PI3K/Akt/mTOR signaling pathway. Six S. epidermidis strains with normal phenotype (WT) and six S. epidermidis strains with SCV phenotype were isolated in parallel from six patients with the prosthetic hip joint infections. THP-1 activated cells were incubated with or without PI3K inhibitor-wortmannin or with mTOR inhibitor-rapamycin. Next, macrophages were exposed to S. epidermidis WT and SCV strains. After 4 h incubation, bacterial survival inside macrophages as well as PI3K-mTOR activation was analyzed. SCV strains of S. epidermidis increased the level of Akt phosphorylation, compared to uninfected macrophages and to their parental WT forms. Wild type variants of S. epidermidis phosphorylated Akt at similar or lower levels as control uninfected cells. Next, the induction of mTOR target, phosphorylated ribosomal protein S6, was measured in bacteria-infected macrophages. The level of phosphorylation was significantly reduced when the cells were exposed to WT strains of S. epidermidis. In contrast, the SCV strains activated S6 protein mostly at a level comparable to the control cells. Rapamycin inhibited mTOR activation as the number of p-S6 positive cells decreased in the tested cases. To conclude, the SCV strains activate the PI3K-Akt signaling pathway in opposite to WT strains. This fact however did not influence the increase in the number of live SCV bacteria as compared to the WT strains. Knowing that the PI3K-Akt pathway is involved in proinflammatory cytokines suppression, SCVs seem to use this pathway to reduce the inflammatory response during the infection.

Investigation of the Actual Causes of Hip Joint Implant Loosening Classified as Aseptic--Analysis of Microbiological Culture Results and Levels of Inflammatory Markers.

Loosening of the hip joint prosthesis is considered as one of the most significant postoperative complications in recent years. The laboratory diagnostic procedure used to differentiate periprosthetic infection from aseptic loosening is very difficult because of the biofilm which microorganisms form on the implant surface. The purpose of this research was to evaluate the level of concordance between clinical classification of implant loosening among 50 patients subjected to reimplantation procedure and laboratory investigation of PJI including microbiological culture results and the levels of inflammatory markers assessed in the patients' synovial fluid samples, serum, and full blood. The synovial fluid was collected for leukocyte count, differential cell count, and culture on standard media. The levels of systemic inflammation markers such as the ESR and CRP concentration were determined in serum and full blood. Tissue samples were collected for microbiological studies. Components from endoprostheses were exposed to ultrasound in a process called sonication. Among the parameters measured in serum and full blood the levels of ESR and CRP were higher in the septic group of patients. Cytologic analysis of synovial fluid was in correlation with microbiologic identification. The most frequent isolated bacteria was Staphylococcus epidermidis. Culture results from materials such as synovial fluid, sonicate and tissues are crucial to establish the infectious aetiology of the loosening. Microscopic analysis of synovial fluid represents a simple, rapid and accurate method for differentiating PJI from aseptic failure. Sonication increases detection of the infectious process, and culture results are in correlation with the cytologic analysis of synovial fluid.

The role of programmed death ligand 1 pathway in persistent biomaterial-associated infections.

Staphylococcus epidermidis is commonly involved in biomaterial-associated infections. Bacterial small colony variants (SCV) seem to be well adapted to persist intracellularly in professional phagocytes evading the host immune response. We studied the expression of PD-L1/L2 on macrophages infected with clinical isolates of S. epidermidis SCV and their parent wild type (WT) strains. The cytokine pattern which is triggered by the examined strains was also analysed. In the study, we infected macrophages with S. epidermidis WT and SCV strains. Persistence and release from macrophages were monitored via lysostaphin protection assays. Moreover, the effect of IFN-γ pre-treatment on bacterial internalisation was investigated. Expression of PD-L1/L2 molecules was analysed with the use of FACS. Inflammatory reaction was measured by IL-10, TNF-α ELISAs, and transcriptional induction of TNF-α. Our study revealed that clinical SCV isolates were able to persist and survive in macrophages for at least 3 days with a low cytotoxic effect and a reduced proinflammatory response as compared to WT strains. Bacteria upregulated PD-L1/L2 expression on macrophages as compared to non-stimulated cells. The results demonstrated that the ability of S. epidermidis SCVs to induce elevated levels of anti-inflammatory cytokine, IL-10, and reduced transcriptional induction of TNF-α, together with expression of PD-L1 on macrophages and the ability to persist intracellularly without damaging the host cell could be the key factor contributing to chronicity of SCV infections.

Sonication as a diagnostic approach used to investigate the infectious etiology of prosthetic hip joint loosening.

The purpose of the study was to evaluate the usefulness of sonication for the diagnosis of prosthetic joint infections (PJIs) by its comparison with periprosthetic tissues (PTs) and synovial fluid (SV-F) cultures. The study groups included 54 patients undergoing exchange of total hip prostheses for so called "aseptic" loosening occurring without clinical manifestations of an accompanying PJI and 22 patients who developed a sinus tract communicating with the prosthesis which was indicative of an ongoing infectious process. Significant positive culture results were obtained among 10 (18.5%) patients with "aseptic" implant failure and in 18 (81.8%) patients who developed a sinus tract. Sonicate-fluid (S-F) yielded bacterial growth in all culture-positive patients with "aseptic" loosening vs. 15 patients with presumed PJIs. There was a concordance in terms of bacterial species isolated from S-F and conventional cultures from individual patients. Coagulase-negative staphylococci were isolated most frequently. Sensitivity of sonication (75%) exceeded that estimated for PTs (69%) and SV-F (45%) cultures. We conclude that identification of causative agents of PJIs which is critical to further therapeutic decisions is aided by the combination of sonication and conventional culture.

Infectious prosthetic hip joint loosening: bacterial species involved in its aetiology and their antibiotic resistance profiles against antibiotics recommended for the therapy of implant-associated infections.

Reliable microbiological diagnosis along with surgery and prolonged antibiotic therapy are key elements in the management of prosthetic-joint infections (PJIs). The purpose of this study was to characterize antibiotic resistance profiles of bacteria involved in the aetiology of PJIs. A total of 33 bacterial isolates cultured from 31 patients undergoing exchange of total hip prostheses were analyzed. The diagnostic approach toward isolation of prosthesis- associated microorganisms included sonication of retrieved implants and conventional cultures of periprosthetic tissues and synovial fluid. The in vitro resistance profiles of bacterial isolates were determined in relation to antibiotics recommended for the therapy of PJIs using the disc diffusion method, E-tests(®) and broth microdilution system. Coagulase-negative staphylococci (CNS) were predominant microorganisms followed by Staphylococcus aureus, Enterobacter cloacae, Streptococcus mitis, and Propionibacterium acnes. Twenty out of 30 and 12 out of 30 staphylococcal isolates were methicillin- and multi-drug resistant, respectively. Only two isolates were rifampicinresistant. All staphylococci were susceptible to glycopeptides and linezolid. This paper stresses the pathogenic role of staphylococci in patients suffering from implant loosening and reports high methicillin- and multidrug-resistance rates in these bacteria. Hence, antimicrobial susceptibility tests of individual bacterial isolates must always be performed to guide selection of the optimal therapeutic option.

Characterization of Staphylococcus epidermidis and Staphyloccocus warneri small-colony variants associated with prosthetic-joint infections.

We determined the frequency of isolation of staphylococcal small-colony variants (SCVs) from 31 culture-positive patients undergoing revision of total hip prosthesis for aseptic loosening or presumed prosthetic-joint infection (PJI). We analysed auxotrophy of cultured SCVs, their antimicrobial susceptibility profiles and their biofilm-forming capacity. Eight SCV strains were cultivated from six (19 %) patients. All SCVs were coagulase-negative staphylococci (CNS) with Staphylococcus epidermidis as the predominant species; there was also one Staphylococcus warneri SCV. The SCVs were auxotrophic for haemin, with one strain additionally auxotrophic for menadione. We noted the presence of two phenotypically (differences concerning antimicrobial susceptibility) and genetically distinct SCV strains in one patient, as well as the growth of two genetically related SCVs that differed in terms of their morphology and the type of auxotrophy in another. Seven out of eight SCVs were resistant to meticillin and gentamicin. In addition, antibiotic sensitivity testing revealed three multidrug-resistant SCV-normal-morphology isolate pairs. One S. epidermidis SCV harboured icaADBC genes and was found to be a proficient biofilm producer. This paper highlights the involvement of CNS SCVs in the aetiology of PJIs, including what is believed to be the first report of a S. warneri SCV. These subpopulations must be actively sought in the routine diagnosis of implant-associated infections. Moreover, in view of the phenotypic and genetic diversity of some SCV pairs, particular attention should be paid to the investigation of all types of observed colony morphologies, and isolates should be subjected to antimicrobial susceptibility testing.

The effects of cooperation between orthopaedic surgeons and microbiologists on the effectiveness of diagnosis and treatment of septic hip joint loosening.

BACKGROUND: The objective of this study is to compare the results of microbiological examinations of two types of materials: specimens collected intraoperationally upon removal of prostheses following septic loosening and cultures from sonicated implants. The study was the effect of collaboration between the Clinic of Orthopedics of A. Gruca Hospital in Otwock and the Department of Microbiology in Lublin. MATERIAL AND METHODS: The study population consisted of 24 patients aged 39 to 84 years, average of 68 years, undergoing surgeries at the Department of Bone and Joint Inflammation, Clinic of Orthopedics of A. Gruca Hospital in Otwock in years 2010-2011. All patients were qualified for surgical treatment consisting of removal of hip prosthesis due to inflammation. Sixty percent of the group were women, while the remaining forty percent were men. The methodology of the study was based on intraoperational collection of material for microbiological examinations at the Department of Microbiology of A. Gruca Hospital. The study material was collected from 3 locations: femoral shank, hip acetabulum and gluteal muscle. Explanted implants were placed in sterile containers, frozen at -20°C and transported to the Department of Microbiology in Lublin. There, the implants were sonicated. RESULTS: The obtained results were consistent in both groups in 37% of cases. In 9 patients (37%), standard cultures were negative while the cultures of sonicated material were positive. In 16 patients (67%), the spectrum of perioperative and sequential antibiotic therapy included flora cultured by standard methods as well as flora obtained from sonicated implant cultures. In the remaining patients, cultures obtained from sonicated material were resistant to antibiotics used. CONCLUSIONS: Cultures of sonicated implant materials increase the chance for identification of microbes responsible for inflammation. Limitations of the method include the requirement to either examine the implant shortly after removal or freeze the implant in order to prevent secondary infections of the material.

[The characteristics of Gram-positive bacteria isolated from skin lesions observed in ambulatory patients and the assessment of their susceptibility to antimicrobial drugs]. / Charakterystyka bakterii Gram-dodatnich wyizolowanych od pacjentów ambulatoryjnych ze zmian skórnych oraz ocena ich lekowrazliwosci.

The bacterial skin and soft-tissue infections occur commonly and are characterized by more or less intensified changes within skin and subcutaneous tissue. The bacterial skin infections give rise to significant therapeutic problems associated with increasing resistance etiological agents of these infections to antibiotics and chemotherapeutics. The aim of this study was to assess the distribution of various Gram-positive microorganisms in skin lesion observed in ambulatory patients in a period from June 2005 to December 2006. There were 116 bacterial strains isolated and identified from clinical samples: Staphylococcus aureus, coagulase - negative staphylococi (S.epidermidis, S. xylosus, S.capitis, S.saccharolyticus), Propionobacterium acnes, Streptococcus spp. (S.agalactiae, S.pyogenes) i Corynebacterium spp. (C. striatum, C. amycolatum, C. aquaticum). In the further part of this study we analyzed a profile of their susceptibility to antibiotics and chemotherapeutics in relation to drugs recommended for the empirical therapy. The resultant resistance patterns among the examined bacterial isolates are indicative of certain divergence between recommended empirical antibiotic therapy and actual antimicrobial susceptibility of many etiologic factors of skin and soft-tissue infections.

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in Poland: further evidence for the changing epidemiology of MRSA.

This study reports the isolation of CA-MRSA strain which was found to colonize the nasal mucosa of a patient undergoing haemodialysis treatment. The MRSA was subjected to molecular analysis by Pulsed Field Gel Electrophoresis (PFGE), multiplex PCR assay for staphylococcal cassette chromosome mec (SCCmec) typing, and PCR detection of the pvl gene encoding for Panton-Valentine leukocidin. The analyzed MRSA harbored the SCCmec type IV and the pvl gene-two unique genetic markers of CA-MRSA. The PFGE pattern of the strain corresponded to the common European CA-MRSA (MLST Type ST80). Moreover, the strain was only resistant to beta-lactam agents and tetracycline. This study adds further evidence for the changing epidemiology of MRSA and indicates the ability of CA-MRSA to affect persons with established risk factors in addition to previously healthy individuals.

Characterisation of Staphylococcus aureus nasal and skin carriage among patients undergoing haemodialysis treatment.

The aim of the study was to investigate the rate of Staphylococcus aureus nasal and skin carriage in patients undergoing haemodialysis. The cultured staphylococcal isolates were subsequently characterized by molecular methods. The study group comprised 43 haemodialysed patients from whom nasal and skin swabs from the vascular access sites were collected. The identification of staphylococcal isolates and antibiotic susceptibility testing were performed on the basis of conventional diagnostic procedures. The staphylococci were further characterized using Pulsed-Field Gel Electrophoresis (PFGE). S. aureus was cultured from 12 (27.9%) patients. Only one (8.3%) patient was colonized with the microorganism both in the anterior nares and the vascular access site representing a single strain, as evidenced by PFGE analysis. Antibiotic susceptibility testing identified one (7.6%) methicillin-resistant S. aureus (MRSA) strain. PFGE typing identified several S. aureus genotypes with the lack of one specific strain responsible for colonization. However, it should be noted that among two (A and D) PFGE patterns genetically indistinguishable and closely related isolates (two isolates for each pattern) were identified. The obtained results revealed a relatively low rate of S. aureus carriage accompanied by low methicillin resistance rate and a significant genetic diversity of cultured isolates with the lack of one predominant strain responsible for colonization.