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Staphylococcal Infections [keywords]
- Longitudinal genetic analyses of Staphylococcus aureus nasal carriage dynamics in a diverse population. [JOURNAL ARTICLE]
- BMC Infect Dis 2013 May 16; 13(1):221.
BACKGROUND:Staphylococcus aureus (SA) nasal colonization plays a critical role in the pathogenesis of staphylococcal infections and SA eradication from the nares has proven to be effective in reducing endogenous infections. To understand SA nasal colonization and its relation with consequent disease, assessment of nasal carriage dynamics and genotypic diversity among a diverse population is a necessity.
RESULTS:We have performed extensive longitudinal monitoring of SA nasal carriage isolates in 109 healthy individuals over a period of up to three years. Longitudinal sampling revealed that 24% of the individuals were persistent SA nasal carriers while 32% were intermittent. To assess the genetic relatedness between different SA isolates within our cohort, multi locus sequence typing (MLST) was performed. MLST revealed that not only were strains colonizing intermittent and persistent nasal carriers genetically similar, belonging to the same clonal complexes, but strain changes within the same host were also observed over time for both types of carriers. More highly discriminating genetic analyses using the hypervariable regions of staphylococcal protein A and clumping factor B virulence genes revealed no preferential colonization of specific SA strains in persistent or intermittent carriers. Moreover, we observed that a subset of persistent and intermittent carriers retained clinically relevant community-acquired methicillin-resistant SA (CA-MRSA) strains in their nares over time.
CONCLUSIONS:The findings of this study provides added perspective on the nasal carriage dynamics between strains colonizing persistent and intermittent carriers; an area currently in need of assessment given that persistent carriers are at greater risk of autoinfection than intermittent carriers.
- Longitudinal Analysis of Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Carriage in Healthy Adolescents. [JOURNAL ARTICLE]
- J Clin Microbiol 2013 May 15.
To determine the long-term carriage pattern, strain relatedness and incidence of subsequent infections among methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) carriers, we screened 154 high school students for nasal carriage of S. aureus at 8 occasions during 11 months. Persistent carriage was defined as positive cultures in ≥7 occasions. Two consecutive isolates from the same subject comprised a pair, and strain relatedness was determined for each pair by molecular typings. Of 1232 nasal swab cultures obtained in 8 occasions, 323 (26.2%) were positive for S. aureus. The isolates consisted of 45 (3.7%) MRSA and 278 (22.6%) MSSA respectively from 12 and 63 subjects. Thirty-five (77.8%) MRSA isolates harbored a type IV or VT staphylococcal chromosomal cassette mec. Among 154 subjects, 52 (33.8%) were intermittent carriers. Persistent carriage was identified in 23 (14.9%) subjects and the incidence was not significantly different for MRSA carriers and MSSA carriers (3/12 [25%] versus 20/63 [31.7%], P =.7449). The MRSA and MSSA isolates were respectively comprised of 33 and 215 strain pairs. Of them, indistinguishable genotype was identified in 33 (100%) MRSA pairs and 173 (80.5%) MSSA pairs (P = .0053). Five subjects developed cellulitis and the incidence was higher for MRSA carriers (2/12, 16.7%) than for MSSA carriers (1/63, 1.58%, P = .0632) and non-carriers (2/79, 2.56%, P = .0828). In conclusion, the long-term carriage pattern in healthy individuals was similar for MRSA and MSSA. MRSA carriers were more likely to carry a single strain with a trend toward higher chance of developing cellulitis compared to MSSA carriers.
- Methicillin-Resistant Staphylococcal Contamination of Clothing Worn by Personnel in a Veterinary Teaching Hospital. [JOURNAL ARTICLE]
- Vet Surg 2013 May 10.
OBJECTIVE:To determine the methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP) contamination rate of white coats (WC) and surgical scrubs (SS) worn by personnel at the Ontario Veterinary College Health Sciences Centre (OVCHSC) and to identify risk factors associated with clothing contamination.
STUDY DESIGN:Cross-sectional study. SAMPLE
POPULATION:Personnel including clinical faculty, house officers, technicians, and veterinary students working at the OVCHSC.
METHODS:Electrostatic cloths were used to sample WC and SS of hospital personnel. Samples were tested for MRSA and MRSP and isolates were typed. Participants completed a self-administered questionnaire and data was evaluated for risk factors.
RESULTS:Of 114 specimens, MRS were isolated from 20 (17.5%), MRSA from 4 (3.5%), and MRSP from 16 (14.0%). Technicians were 9.5× (OR = 0.95, 95% CI: 1.2-∞, P = .03) more likely than students to have clothing contaminated with MRSA. No risk factors were identified for MRSP or for overall MRS contamination.
CONCLUSIONS:Standard hospital clothing was found to have a high prevalence of MRS contamination in a veterinary teaching hospital and could be a source of hospital-acquired infections.
- Staphylococcal biofilm growth on smooth and porous titanium coatings for biomedical applications. [JOURNAL ARTICLE]
- J Biomed Mater Res A 2013 May 10.
Implant-related infections are a serious complication in prosthetic surgery, substantially jeopardizing implant fixation. As porous coatings for improved osseointegration typically present an increased surface roughness, their resulting large surface area (sometimes increasing with over 700% compared to an ideal plane) renders the implant extremely susceptible to bacterial colonization and subsequent biofilm formation. Therefore, there is particular interest in orthopaedic implantology to engineer surfaces that combine both the ability to improve osseointegration and at the same time reduce the infection risk. As part of this orthopaedic coating development, the interest of in vitro studies on the interaction between implant surfaces and bacteria/biofilms is growing. In this study, the in vitro staphylococcal adhesion and biofilm formation on newly developed porous pure Ti coatings with 50% porosity and pore sizes up to 50 μm is compared to various dense and porous Ti or Ti-6Al-4V reference surfaces. Multiple linear regression analysis indicates that surface roughness and hydrophobicity are the main determinants for bacterial adherence. Accordingly, the novel coatings display a significant reduction of up to five times less bacterial surface colonization when compared to a commercial state-of-the-art vacuum plasma sprayed coating. However, the results also show that a further expansion of the porosity with over 15% and/or the pore size up to 150 μm is correlated to a significant increase in the roughness parameters resulting in an ascent of bacterial attachment. Chemically modifying the Ti surface in order to improve its hydrophilicity, while preserving the average roughness, is found to strongly decrease bacteria quantities, indicating the importance of surface functionalization to reduce the infection risk of porous coatings. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
- Desired Vancomycin Trough Serum Concentration for Treating Invasive Methicillin-Resistant Staphylococcal Infections. [JOURNAL ARTICLE]
- Pediatr Infect Dis J 2013 May 6.
Vancomycin AUC/MIC >400 best predicts outcome when treating invasive MRSA infection, however trough serum concentrations are used clinically to assess the appropriateness of dosing. We used pharmacokinetic modeling and simulation to examine the relationship between vancomycin trough values and AUC/MIC in children receiving vancomycin 15mg/kg every 6h and MRSA MIC of 1 μg/ml. A trough of 7-10 μg/ml predicted achievement of AUC/MIC >400 for >90% of children.
- A novel synthetic (poly)glycerolphosphate-based anti-staphylococcal conjugate vaccine. [JOURNAL ARTICLE]
- Infect Immun 2013 May 6.
Staphylococcal infections are a major source of global morbidity and mortality. Currently there exists no anti-staphylococcal vaccine in clinical use. Previous animal studies suggested a possible role for purified lipoteichoic acid as a vaccine target for eliciting protective IgG to several Gram-positive pathogens. Since the highly-conserved (poly)glycerolphosphate backbone of lipoteichoic acid is a major antigenic target of the humoral immune system during staphylococcal infections, we developed a synthetic method for producing glycerol phosphoramidites to create a covalent 10-mer of (poly)glycerolphosphate for potential use in a conjugate vaccine. We initially demonstrate that intact Staphylococcus aureus elicits murine CD4+ T cell-dependent (poly)glycerolphosphate-specific IgM and IgG responses in vivo. Naïve mice immunized with a covalent conjugate of (poly)glycerolphosphate and tetanus toxoid in alum + CpG-oligodeoxynucleotides produced high secondary titers of serum (poly)glycerolphosphate-specific IgG. Sera from immunized mice enhanced opsonophagocytic killing of live Staphylococcus aureus in vitro. Mice actively immunized with the (poly)glycerolphosphate conjugate vaccine showed rapid clearance of staphylococcal bacteremia in vivo relative to mice similarly immunized with an irrelevant conjugate vaccine. In contrast to purified, natural lipoteichoic acid, the (poly)glycerolphosphate conjugate vaccine itself exhibited no detectable inflammatory activity. These data suggest that a synthetic (poly)glycerolphosphate-based conjugate vaccine will contribute to active protection against extracellular Gram-positive pathogens expressing this highly conserved backbone structure in their membrane-associated lipoteichoic acid.
- Population Diversification in Staphylococcus aureus Biofilms May Promote Dissemination and Persistence. [Journal Article]
- PLoS One 2013; 8(4):e62513.
The biofilm mode of growth can lead to diversification of the bacterial population by promoting the emergence of variants. Here we report the identification and characterization of two major subpopulations of morphological variants arising in biofilms of S. aureus. One of these lacked pigmentation (termed white variants; WVs), whilst the other formed colonies on agar that were larger and paler than the parental strain (termed large pale variants; LPVs). WVs were unable to form biofilms, and exhibited increased proteolysis and haemolysis; all phenotypes attributable to loss-of-function mutations identified in the gene encoding the alternative sigma factor, sigB. For LPVs, no differences in biofilm forming capacity or proteolysis were observed compared with the parental strain. Genetic analysis of LPVs revealed that they had undergone mutation in the accessory gene regulator system (agrA), and deficiency in agr was confirmed by demonstrating loss of both colony spreading and haemolytic activity. The observation that S. aureus biofilms elaborate large subpopulations of sigB and agr mutants, both genotypes that have independently been shown to be of importance in staphylococcal disease, has implications for our understanding of staphylococcal infections involving a biofilm component.
- Effects of 5-aminolevulinic acid-mediated photodynamic therapy on antibiotic-resistant staphylococcal biofilm: an in vitro study. [JOURNAL ARTICLE]
- J Surg Res 2013 Apr 18.
BACKGROUND:Treatments of infections are not always successful because of multi-antibiotic-resistant organisms. It is therefore particularly urgent to provide more effective anti-infective strategy against these organisms. 5-Aminolevulinic acid (ALA), with the chemical structure C5H9NO3, is the only photodynamic therapy agent that is a biochemical precursor of a photosensitizer (protoporphyrin IX [PpIX]), which is naturally produced by the body. 5-Aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) has been shown to have a strong effect on the treatment of localized cancerous and precancerous lesions, and further study demonstrated its efficacy for gram-positive and gram-negative bacteria. However, its effect on biofilm formed by antibiotic-resistant strains has not been reported.
METHODS:In this study, we evaluated the effectiveness of ALA-PDT on biofilms formed by methicillin-resistant Staphylococcus aureus (ATCC 43300) and methicillin-resistant S epidermidis (MRSE 287). The strains were cultured with 40 mM of ALA in 24-well microtiter plates containing coverslips at 37°C for 24 h in the dark. PpIX fluorescence in biofilms formed by the two strains was observed by confocal laser scanning microscopy (CLSM). ALA-treated biofilms were irradiated at different doses (0, 100, 200, and 300 J/cm(2)) using a semiconductor laser. Biofilm exposed only to Tryptone Soy Broth or irradiation (300 J/cm(2)) was investigated. Viability determination, CLSM, and scanning electron microscopy were used to investigate the photodynamic inactivation of ALA-PDT.
RESULTS:ALA was absorbed and converted to PpIX by both methicillin-resistant S aureus and methicillin-resistant S epidermidis. No cell inactivation was detectable in biofilms of either strain incubated with ALA without exposure to light, incubated with Tryptone Soy Broth only, or irradiated with red light only. However, a significant number of cells within biofilms were inactivated during irradiation with different doses of red light in the presence of 40 mM of ALA in a dose-dependent manner. The drastic reduction in cell survival within biofilms and the disruption of biofilms were confirmed by CLSM and scanning electron microscopy.
CONCLUSIONS:ALA-PDT has the potential to eliminate the biofilm of Staphylococcus, especially antibiotic-resistant strains, effectively. It will be suitable for the treatment of superficial local infections such as surface wounds, burns, oral and dental infections, dermatologic infections such as acne and rosacea, and soft tissue and bone infections with bone exposure.
- Activity-guided isolation and identification of anti-staphylococcal components from Senecio tenuifolius Burm. F. leaf extracts. [Journal Article]
- Asian Pac J Trop Biomed 2013 Mar; 3(3):191-5.
To investigate activity-guided isolation and identification of anti-Staphylococcus aures components from Senecio tenuifolius Burm. F. (S. tenuifolius).Hexane, chloroform, ethyl acetate, methanol and aqueous extracts of S. tenuifolius were prepared by soxilation for antimicrobial activity against one registered Staphylococcus aureus (S. aureus) (ATCC No: 25923) and two clinical isolates, methicillin resistant and methicillin sensitive S. aureus. NCCL standard methods were followed for antibacterial activity. GC-MS was performed to identify the chemical composition of bio active fraction.Among all solvent extracts, methanol extract significantly reduced the growth of S. aureus (ATCC No: 25923), methicillin resistant and methicillin sensitive S. aureus with the best zone of inhibition at 16.23, 14.06 and 15.23 mm and minimum inhibition concentration (MIC) values at 426.16, 683.22 and 512.12 µg/mL, respectively. In order to detect the active component in methanol extract, it was further purified by column chromatography, which yielded four fractions (St1, St2, St3, and St4). Among these four fractions, St3 was effective against the tested strains of S. aures, with the best zone of inhibition at 15.09, 13.25 and 14.12 mm and with best MIC values at 88.16, 128.11 and 116.12 µg/mL, respectively. Effective fraction partially purified from S. tenuifolius (St3) yielded MIC's that were at least 20 fold less when compared to crude extract. GC-MS analysis of St3 revealed the presence of 3-[methyl-6,7-dihydro benzofuran-4 (5H)-one], 1,2-benzenedicarboxylic acid, hydroquinone, methyl ester and 3 unknown compounds.The study provides scientific evidence for traditional and folklore medicinal use of S. tenuifolius in skin infections treatment.
- Staphylococcus aureus mutants lacking cell wall-bound protein A found in isolates from bacteraemia, MRSA infection and a healthy nasal carrier. [Journal Article]
- Pathog Dis 2013 Feb; 67(1):19-24.
Staphylococcus aureus is a major human pathogen and a multitude of virulence factors enables it to cause infections, from superficial lesions to life-threatening systemic conditions. Staphylococcal protein A (SpA) is a surface protein contributing to S. aureus pathogenesis by interfering with immune responses and activating inflammation. Seven isolates with frameshift mutations in the spa repeat region were investigated to determine whether these mutations lead to truncation and secretion of SpA into the extracellular environment. Five isolates originated from blood cultures, one from an MRSA infection and one from a persistent nasal carrier. Full-length spa genes from the seven isolates were sequenced, and Western blot experiments were performed to localize SpA. Three isolates had identical deviating 25-bp spa repeats, but all isolates displayed different repeat successions. The DNA sequence revealed that the frameshift mutations created premature stop codons in all seven isolates, resulting in truncated SpA of different lengths, however, all lacking the XC region with the C-terminal sorting signal. SpA was detected by Western blot in six of the seven isolates, mainly extracellularly. Our findings demonstrate that S. aureus isolates with truncated SpA, not anchored to the cell wall, can still be found in bacteraemia, infection and among carriers.