SA Strains Research Articles

Machine Learning with Alpha Toxin Phenotype to Predict Clinical Outcome in Patients with Staphylococcus aureus Bloodstream Infection.

Staphylococcus aureus bloodstream (SAB) infection remains a leading cause of sepsis-related mortality. Yet, current treatment does not account for variable virulence traits that mediate host dysregulated immune response, such as SA α-toxin (Hla)-mediated thrombocytopenia. Here, we applied machine learning (ML) to bacterial growth images combined with platelet count data to predict patient outcomes. We profiled Hla phenotypes of SA isolates collected from patients with bacteremia by taking smartphone images of beta-hemolytic growth on sheep blood agar (SBA). Electronic medical records were reviewed to extract relevant laboratory and clinical data. A convolutional neural network was applied to process the plate image data for input along with day 1 patient platelet count to generate ML-based models that predict thrombocytopenia on day 4 and mortality. A total of 229 patients infected with SA strains exhibiting varying zone sizes of beta-hemolysis on SBA were included. A total of 539 images of bacterial growth on SBA were generated as inputs for model development. One-third of patients developed thrombocytopenia at onset, with an overall mortality rate of 18.8%. The models developed from the ML algorithm showed strong performance (AUC 0.92) for predicting thrombocytopenia on day 4 of infection and modest performance (AUC 0.711) for mortality. Our findings support further development and validation of a proof-of-concept ML application in digital microbiology, with a measure of bacterial virulence factor production that carries prognostic significance and can help guide treatment selection.

A New Algorithm Identifying Association of Staphylococcus aureus Strains with Low Expression of Filaggrin in Atopic Dermatitis

Skin colonization with Staphylococcus aureus (S. aureus; Sa) contributes to the development of atopic dermatitis (AD). AD is associated with low filaggrin (FLG) expression in the skin due to genetic mutations and inflammation. We hypothesized that in the context of low FLG, colonizing Sa strains may have distinct gene patterns.

Genetic analysis of human parechovirus type 5 isolated from children in Sapporo, Japan in the summer of 2018

Human parechovirus (HPeV) types 1 and 3 are frequently detected in Japan, but HPeV5 is not detected. HPeV5 was isolated for the first time in Japan from seven clinical samples collected from children in Sapporo as part of the National Epidemiological Surveillance of Infectious Diseases from July to August in 2018. Seven HPeV5 strains that were detected in Sapporo (HPeV5 Sa) were analyzed in the VP1 region by direct sequencing using Sanger sequencing methods. Whole genome sequence of these strains was determined by next-generation sequencing. The VP1 region of HPeV5 Sa was closely related to HPeV5 strains detected in Belarus and Germany in 2018, and to those detected in Australia in 2019. The 3D polymerase region of HPeV5 Sa strains showed a high nucleotide identity to HPeV3 strain detected in Australia in 2013. These findings suggest that HPeV5 Sa is a recombinant virus of HPeV5 and HPeV3, and HPeV5 strains that are genetically closely related to each other may have circulated in Europe, Japan, and Australia between 2018 and 2019.

Resistance to veterinary antimicrobials of Staphylococcus aureus from mastitic milk

Abstract Background Use of antimicrobials in veterinary medicine for prophylactic and therapeutic purposes is one of the main culprits for the selection of antimicrobial resistant bugs that currently threaten human and animal health. Therefore, surveillance on antimicrobial resistance (AMR) selection trends in animal husbandry is of utmost importance to prevent the spread of resistant bugs to humans. The species Staphylococcus aureus (Sa), that is of particular concern for the spread of methicillin-resistant (MRSA) strains, often causes mastitis in milk producing animals, thus requiring antibiotic treatment that can impact on the AMR status of this pathogen. With the aim of elucidating the current evolution of AMR in Sa involved in mastitis and the threats posed by the consumption of raw milk or inadequately pasteurized dairy products, data from antimicrobial susceptibility testing carried out on Sa strains from mastitis in years 2013 - 2019 in Molise region, Italy, were analyzed. Methods Sa isolates were tested by disk diffusion and inhibition halo sizes were converted in Minimum inhibitory concentrations (MIC) according to the EUCAST standards for the antibiotics there included. One isolate per AMR profile per farm was considered to define the percentage of the antibiotic resistant on the total number of isolates per year. Results The number of diagnosed Sa infections per year ranged between seven and nineteen, with a total of 78 isolates from 70 farms. The percentages of those resistant to aminoglycosides kanamycin, neomycin and paromomycin, to the macrolide tylosin and the multi drug resistant (MDR) isolates increased since 2015. The latter ranged between 26.3 and 85.7%. Conclusions AMR and MDR Sa in milk producing animals pose a serious risk to public health and needs stricter surveillance. Key messages Limiting use of antibiotics is needed to revert the trend. AMR Sa strains in dairy products, need to be kept under control for the strict connection with human health.

Meilleures Pratiques Internationales De Lutte Contre Le Terrorisme Et La Criminalite Organisee Par Des Unites Speciales Et Des Services De Detection Et De Repression

Therefore, this unit as a component of the gendarmerie is built on the principle of a military unit. The gendarmerie, one of the few state institutions in France, has been in existence for over 200 years and has a status as DOI: 10.32370/IA_2021_03_07 a significant component of the country's armed forces and is an extremely important part of the police system. The gendarmerie is subordinated to the Ministry of Defense (on the authority of the Main Directorate), and on the ground - to the command of military districts. At the same time, the gendarmerie is at the operational disposal of the Ministry of Internal Affairs and the Ministry of Justice. Significant autonomy within the Armed Forces allows the gendarmerie to combine military functions with purely police and administrative ones. The difference between police and gendarmerie is that the police are civilian civil servants. They can wear civilian clothes and trade union and political freedoms. Gendarmes also have the status of servicemen and military ranks, always in uniform, not entitled to strike and are responsible for violations in accordance with military charters - from guardians to dismissal from service (for example, for the use of alcohol "in the performance of official duties" the gendarme is threatened arrest for up to 30 days). The need for the creation of the Austrian Special Forces was conditioned by the urgency of taking measures to ensure the safety of the flow of emigrants of Jewish nationality from the former USSR since in autumn 1973 against them was committed serious terrorist act. Special unit "Cobra" enters the warehouse of the Ministry of Internal Affairs and has got a double subordination: through direct combat engagement to the head of public safety, and in relation to personnel issues and logistics - the central command of the gendarmerie of the Austrian Ministry of Internal Affairs. Among the well-known British Special Political Service (Special Air Service, or SAS) is probably the best counterterrorism unit. Its component - Special Projects (SP) team - the main anti-terrorist squad. The Special Air Service and its Counter Revolutionary Warfare Squadron (CRW) unit, the Antirevolutionary Military Squadron, were founded in 1942. The feature of training SAS servicemen is to teach each soldier to possess all methods and means of combating terrorism. To achieve this, SAS trains all of its squadron through training cycles. Acquired skills are improved later in the SP-team's combat duties. The main thing in the work is the maximum approximation of training sessions to a real combat situation in the conduct of operations on the release of hostages, in the role of which are civilians. Anti-terrorist training of SAS and the development of practical measures for the release of hostages is facilitated by the fact that high-ranking members of the British Government, including the Prime Minister, are personally involved in it.

Staphylococcus aureus PSM Peptides Modulate Human Monocyte-Derived Dendritic Cells to Prime Regulatory T Cells.

Staphylococcus aureus (Sa), as one of the major human pathogens, has very effective strategies to subvert the human immune system. Virulence of the emerging community-associated methicillin-resistant Sa (CA-MRSA) depends on the secretion of phenol-soluble modulin (PSM) peptide toxins e.g., by binding to and modulation of innate immune cells. Previously, by using mouse bone marrow-derived dendritic cells we demonstrated that PSMs in combination with various Toll-like receptor (TLR) ligands induce a tolerogenic DC phenotype (tDC) characterized by the production of IL-10 and impaired secretion of pro-inflammatory cytokines. Consequently, PSM-induced tDCs favored priming of CD4+CD25+FoxP3+ Tregs with suppressor function while impairing the Th1 response. However, the relevance of these findings for the human system remained elusive. Here, we analyzed the impact of PSMα3 on the maturation, cytokine production, antigen uptake, and T cell stimulatory capacity of human monocyte-derived DCs (moDCs) treated simultaneously with either LPS (TLR4 ligand) or Sa cell lysate (TLR2 ligand). Herein, we demonstrate that PSMs indeed modulate human moDCs upon treatment with TLR2/4 ligands via multiple mechanisms, such as transient pore formation, impaired DC maturation, inhibited pro- and anti-inflammatory cytokine secretion, as well as reduced antigen uptake. As a result, the adaptive immune response was altered shown by an increased differentiation of naïve and even CD4+ T cells from patients with Th1/Th17-induced diseases (spondyloarthritis and rheumatoid arthritis) into CD4+CD127−CD25hiCD45RA−FoxP3hi regulatory T cells (Tregs) with suppressor function. This Treg induction was mediated most predominantly by direct DC-T-cell interaction. Thus, PSMs from highly virulent Sa strains affect DC functions not only in the mouse, but also in the human system, thereby modulating the adaptive immune response and probably increasing the tolerance toward the bacteria. Moreover, PSMα3 might be a novel peptide for tolerogenic DC induction that may be used for DC vaccination strategies.

Antimicrobial resistance in bacterial pathogens among hospitalised patients with severe invasive infections.

The most severe infections are invasive infections, due to the fact that the germs can accumulate in multiple sites and produce a body-wide infection known as sepsis. Septic shock has the highest mortality rate among non-traumatic medical conditions. In this study, we aimed to evaluate the incidence and prevalence of invasive infections in a hospital environment. Another second objective was to establish the aetiology of invasive infections in our hospital and the antibiotic resistance profile of the germs involved, which are both important for determining the therapeutic approach for the treatment of these infections. The study included 505 hospitalized patients from which we collected a total of 974 blood cultures. For the analysis of the blood cultures, we used an automated incubator. The bottles flagged as positive were subcultured on blood agar, and the grown colonies were identified using an identification system. Invasive infections had a prevalence rate of 27.72% in our hospital. From the 974 blood cultures, we isolated 170 bacterial strains: Staphylococcus aureus (SA; 63 strains, 37.06%), Klebsiella spp. (27 strains, 15.88%), coagulase-negative staphylococci (CoNS; 18 strains, 10.59%), Enterococcus spp. (17 strains, 10.00%), Escherichia coli (12 strains, 7.06%), Streptococcus spp. (11 strains, 6.47%) and other bacterial species. The prevalence of methicillin-resistant SA (MRSA) in our study was 36.51% from the SA strains. The MRSA prevalence differed significantly according to age (37.50% in adults vs. 28.57% in children, P=0.047) and ICU admission (42.42% in ICU patients vs. 30.00% in non-ICU patients, P=0.018). We performed a multivariate analysis of the invasive infection risk which detected as significant predictors the admission into the cardiology ward and plastic surgery ward. On the whole, the findings of this study indicate that the high prevalence of Gram-positive cocci in blood cultures, mostly SA, with multidrug resistance has important consequences for the management of invasive infections.

In Vitro Activity of Lefamulin against S. aureus Collected Worldwide from Hospitalized Patients with Bacterial Pneumonia

Background S. aureus (SA) is a well-recognized cause of pneumonia from both the community and hospital settings. The clinical management of SA pneumonia is complicated by the invasive infection it can cause and the high prevalence of methicillin-resistance (MR). Lefamulin (LEF) is the first semi-synthetic pleuromutilin antibiotic for IV and oral use in humans. LEF is the first semi-synthetic pleuromutilin antibiotic for IV and oral use in humans and it specifically inhibits bacterial protein synthesis. LEF is currently in Phase 3 trials for the treatment of community-acquired bacterial pneumonia (CABP). This study investigated the in vitro activity of LEF and comparators against SA strains collected from patients hospitalized with pneumonia in 2015.Methods1273 unique SA isolates were collected from hospitalized patients with pneumonia worldwide in 28 countries (33 sites) in 2015 as part of the SENTRY surveillance program. Isolates included 401 hospital-acquired (HA) SA (259 from ICU, 152 from ventilator associated pneumonia, VAP). Susceptibility testing was conducted using the CLSI broth microdilution method and susceptibility was interpreted per CLSI 2017 breakpoint criteria.ResultsLEF was the most potent compound tested, with 99.7% of all SA isolates being inhibited at a concentration of ≤0.25 mg/L (MIC50/90 values of 0.06/0.12 mg/L) and irrespective of the collection source (ICU/non-ICU, VAP/non-VAP). 31.6% of isolates (n = 402) were MRSA of which 99.3% were inhibited at a LEF concentration of ≤0.25 µg/mL (MIC50/90, 0.06/0.12 mg/L). Susceptibility rates for all SA isolates were >90% for ceftaroline, vancomycin, linezolid and doxycycline. Susceptibility to azithromycin, levofloxacin and clindamycin was limited, particularly among MRSA (see Table).ConclusionSA strains collected from patients hospitalized with pneumonia including HAP and VAP were highly susceptible to LEF regardless of the resistance phenotype to the other antibiotics tested. Due to its potent activity against resistant SA and the most prevalent typical and atypical respiratory pathogens, as well as the availability of IV and oral formulations, LEF has the potential to play a role in the empiric treatment of CABP and supports evaluation in HAP and VAP caused by SA.Disclosures S. Paukner, Nabriva Therapeutics: Employee and Shareholder, Salary; R. K. Flamm, Nabriva Therapeutics: Research Contractor, Research grant; J. Schuchert, Nabriva Therapeutics: Research Contractor, Research grant; S. P. Gelone, Nabriva Therapeutics: Employee and Shareholder, Salary; H. S. Sader, The Medicines Company: Research Contractor, Research grant

Citral, a monoterpenoid aldehyde interacts synergistically with norfloxacin against methicillin resistant Staphylococcus aureus

BackgroundStaphylococcus aureus (SA), is a major human pathogen causing wide range of clinical infections, which has been further complicated by drug resistance like methicillin resistant S. aureus (MRSA), vancomycin intermediate S. aureus (VISA)/vancomycin resistant S. aureus (VRSA), etc. The present study was aimed at determining anti-staphylococcal potential of citral against drug resistant clinical isolates alone and in combination with antibiotics. PurposeTo assess the potential of citral in combination with norfloxacin in treating drug resistant infections of SA. Study designIn the present study, synergistic interaction of citral and norfloxacin against drug resistant SA strains was evaluated. Further the efficacy and possible mechanism of action of the combination was also evaluated using in vitro and in vivo assays. MethodThe anti-staphylococcal activity of each of the monoterpene and the antibiotic was determined in terms of MIC and the effective concentration of both compounds in combination was obtained by checkerboard assay. In vivo efficacy and oral acute toxicity was evaluated in Swiss albino mice model. To understand the mechanism of action, time-kill curve, bacteriolysis, leakage, membrane depolarization, salt tolerance and ethidium bromide efflux assays were performed. ResultsCitral was found effective against clinical isolates of SA with MIC values ranging from 75 to 150 µg ml−1 exhibiting bacteriostatic activity. Citral interacted synergistically, reducing MIC of norfloxacin up to 32-folds with FICI ≤ 0.50. Citral did not affect cell wall, but could damage cell membrane, inhibit efflux pump and affect the membrane potential. Citral could reduce the staphylococcal load of spleen and liver tissues in a dose-dependent manner which was further reduced when used in combination with norfloxacin. Citral did not exhibit any mortality or morbidity up to 500 mg kg−1 body weight and found to prolong the post-antibiotic effect of norfloxacin. ConclusionBased on these observations, citral could be a lead candidate phytomolecule for further developing it into an anti-staphylococcal agent. The observations of combination study will help in reducing the burden of antibiotics leading to delayed resistance development.

Staphylococcus Aureus Carriage in French Athletes at Risk of CA-MRSA Infection: a Prospective, Cross-sectional Study

BackgroundStaphylococcus aureus (SA) is a leading cause of infectious diseases in sports teams. In recent decades, community-associated SA (CA-SA) strains have emerged worldwide and have been responsible for outbreaks in sports teams. There are very few data on the prevalence of these strains in France, and none on the carriage among athletes.MethodsWe conducted a cross-sectional study to determine the SA carriage proportion among athletes practicing sports at risk for CA-SA infection in a French county, and determined the methicillin-resistant and/or CA-SA proportion. We also analyzed SA carriage according to risks factors and studied the SA clonality in a sample of our population.ResultsWe included 300 athletes; SA carriage proportion was 61% (n = 183) and one was MRSA carrier (0.33%). The MRSA strain belonged to the clonal complex ST5. None of the strain produced Panton Valentine Leucocidin, and we did not find clonal distribution within the teams. Interestingly, we found a high throat-only carriage (n = 57), 31.1% of the SA carriers.ConclusionWe found a high SA carriage with a local epidemiology quite different than that reported in a similar population in the USA. Further studies on SA carriage should include throat sampling.Trial registrationThe approved protocol was registered on ClinicalTrial.gov, NCT01148485.

Using Quantitative Spectrometry to Understand the Influence of Genetics and Nutritional Perturbations On the Virulence Potential of Staphylococcus aureus

Staphylococcus aureus (Sa) is the leading cause of a variety of bacterial infections ranging from superficial skin infections to invasive and life threatening diseases such as septic bacteremia, necrotizing pneumonia, and endocarditis. The success of Sa as a human pathogen is contributed to its ability to adapt to different environments by changing expression, production, or secretion of virulence factors. Although Sa immune evasion is well-studied, the regulation of virulence factors under different nutrient and growth conditions is still not well understood. Here, we used label-free quantitative mass spectrometry to quantify and compare the Sa exoproteins (i.e. exoproteomes) of master regulator mutants or established reference strains. Different environmental conditions were addressed by growing the bacteria in rich or minimal media at different phases of growth. We observed clear differences in the composition of the exoproteomes depending on the genetic background or growth conditions. The relative abundance of cytotoxins determined in our study correlated well with differences in cytotoxicity measured by lysis of human neutrophils. Our findings demonstrate that label-free quantitative mass spectrometry is a versatile tool for predicting the virulence of bacterial strains and highlights the importance of the experimental design for in vitro studies. Furthermore, the results indicate that label-free proteomics can be used to cluster isolates into groups with similar virulence properties, highlighting the power of label-free quantitative mass spectrometry to distinguish Sa strains.

Pegylated Curcumin with Gold Nanoparticles: Antimicrobial Agent Evaluation

Extended Abstract Curcumin is a polyphenol derived from the Curcuma Longa plant. Curcumin exhibits a variety of therapeutic properties, including antioxidant, analgesic, anti-inflammatory, anticancer and antiseptic activities [1]. Curcumin acts as photosensitizer in photodynamic therapy (PDT), which is an alternative way to kill pathogenic microorganisms [2]. The use of gold nanoparticles (AuNPs) as the vehicle for curcumin delivery increases photodynamic ability [3]. Therefore, the present study aim is to investigate the effect of the photodynamic action of LED-activated curcumin gold nanoparticles, on cell viability of Staphylococcus aureus, Staphylococcus aureus (Sa), Staphylococcus epidermidis (Se), Pseudomonas aeruginosa (Pa), Escherichia coli (Ec), Citrobacter freundii (Cf) and Klebsiella pneumoniae (Kp). To prepare Curcumin gold nanoparticles (Curc:AuNps) solutions, 3.2 mg of HAuCl4 was mixed with 1.5 mg Curcumin and Polyethylene glycol (PEG) in Mili-Q water. This solution was exposed to light from a mercury metal halide lamp. The resulting solutions were characterized by UV-Vis and transmission electron microscopy (TEM). The in vitro antibacterial activity of Curc:AuNps was evaluated against Sa, Se, Pa, Ec, Cf and Kp using the minimum inhibitory concentration (MIC) test. The effects of exposure to yellow LED light with ~38 J/cm fluence and variations in the Curc:AuNPs concentrations (50, 75 and 100% dilutions) were studied. The presence of a surface plasmon resonance band at ~520 nm indicated the formation of spherical gold nanoparticles. In the presence of PEG, the solution color changed some minutes after the mixing of reagents, and solution size homogeneity was improved with the mercury metal halide lamp illumination. TEM analyses showed ~17±2 nm nanoparticles. The results indicate that PDT with curcumin gold nanoparticles strongly inhibits the development of Gram positive and Gram negative bacteria. This study revealed antibacterial probability of inhibition >80% with 32 mM of Curc:AuNPs and light against Sa, Se, Cf and Kp strains after 18 hours of incubation. NOVA/Tukey's tests were conducted to compare groups curcumin/Curc:AuNPs, with and without photodynamic excitation. This work was supported by the “Fundacao de Amparo a Pesquisa do Estado de Sao Paulo” (FAPESP), Grant number 2014/06960-9.

104 Antimicrobial susceptibility of Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA) isolated from CF patients over 13 years

Objectives Aim of this study was to determine the frequency and pattern of antimicrobial susceptibility of isolated microorganisms. Method Clinical materials (sputum, deep throat swab and BAL) were obtained from 155 pts (age range 0.5–21 yrs; 82 F/73 M), observed from 2002 to 2014. Isolation, identification and susceptibility testing were performed by standard methods. 2324 specimens were analyzed. Results In 1949 isolates collected over 13 yrs the most frequent microorganism was SA, 53%, followed by PA, 17.5%, HI, 17.3%, and non-fermenting Gram(–) bacilli other than PA, 3.7%. SA was identified in 80% pts, 12% of whom were colonized with MRSA strains. The prevalence of small colony variants in SA-positive pts was 9%. SA strains were susceptible to gentamicin (97%) and sulfamethoxazole (96%), ciprofloxacin (93%), macrolides (64%). All strains were susceptible to glycopeptides and linezolid. PA was isolated from 34% pts; in this group 52% were colonized chronically, 42% presented mucoid phenotype and 25% were infected with multi-drug-resistant strains. PA strains were susceptible to colistin 97%, imipenem 86%, ceftazidime 86%, tobramicin 84%, ciprofloxacin 83%, piperacillin 79%, gentamicin 71%. Over 13 yrs, PA resistance to antibiotics increased substantially: carbapenems from 0% to 10%, ciprofloxacin from 0% to 13%, third generation cephalosporins from 0% to 15%, aminoglycosides from 9% to 45%; SA resistance to ciprofloxacin from 2% to 11%. Conclusion SA and PA are still the most commonly isolated microorganisms in CF pts. PA increasing resistance gives a serious cause for concern.

Comparison of nosocomial infection rates in a neonatal intensive care unit before and after moving into a new location

women. This study aimed to screen the antimicrobial susceptibility and the virulent factors of SA strains isolated from patients with puerperal mastitis. Methods: All SA isolated from the clinical specimens obtained from patients with puerperal mastitis were tested. Susceptibility to common antimicrobial agents was determined using the disk diffusion method. The genes encoding antimicrobial resistance(mecA) and virulent factors encoding the exotoxins(pvl, eta, etb, and tsst) and classic staphylococcal enterotoxins (SEs)(sea, seb, sec, sed, and see) were tested by specific PCR. Some strains were selected for multilocus sequence typing(MLST). Results: A total of 76 SA isolates were obtained from 48 women, 51(67.1%) isolates were oxacillin resistant(ORSA). Most ORSAs were susceptible to the antimicrobial agents [Susceptible rates: gentamicin(67.3%), TMP/ SMX(98.0%), 100% to teicoplanin, rifampin, fusidic acid, linezolid, levofloxacin, doxycycline], but resistant to clindamycin(6.1%) and erythromycin(6.1%); while most of the OSSA isolates were susceptible to clindamycin(74.1%) and erythromycin(74.1%). All but one ORSA carried mecA gene. Of the 76 SA strains, 42.1%(32/76) were positive for pvl, 68.4%(52/76) were positive for at least one enterotoxin genes. Few isolates carried eta 8/76(10.5%), etb 0/76, and tsst 3/76(3.9%). Sequence type 59(ST 59) was the most common(26 strains) type among the 29 SA with MLST performed. Conclusions: Oxacillin resistance was common among SA isolated from puerperal mastitis, but some other common antimicrobial agents remained susceptible, e.g., fusidic acid and TMP/SMX. The association with abscess formation and pvl positive SA infection is not significant.

Longitudinal genetic analyses of Staphylococcus aureus nasal carriage dynamics in a diverse population

BackgroundStaphylococcus 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.ResultsWe 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.ConclusionsThe 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.

Epidemiological investigation of community-acquired Staphylococcus aureus infection

The current study aimed to reveal the pathogenic and spreading mechanisms of community-acquired Staphylococcus aureus (CA-SA) by analyzing its prevalence, drug resistance, virulence, and pathogenic factors. Historical information regarding CA skin and soft tissue infections were collected and disease characteristics were analyzed. Isolated CA-SA strains were subjected to antibiotic sensitivity tests using the agar dilution method, Staphylococcus cassette chromosome mec (SCCmec) tests, multilocus sequence typing (MLST), and staphylococcal protein A (SPA) and toxin gene screening. A total of 55 skin and soft tissue infections were investigated, and 12 strains of SA bacteria were isolated, which were all CA methicillin-susceptible SA (CA-MSSA). The antibiotic sensitivity tests showed that CA-MSSA was susceptible to all antibacterials with the exception of high resistance to erythromycin, clindamycin, tetracycline, gentamicin, and levofloxacin (ranging from 8.3 to 50%). The toxin detection results showed that the Panton-Valentine leukocidin (PVL) positive rate in CA-MSSA was 33.3%, the enterotoxin positive rate was 25%, and the toxic shock syndrome toxin-1 (TSSL) positive rate was 8.3%. No Staphylococcus enterotoxin H or Staphylococcus exfoliati was detected. MLST and SPA typing showed that the clones of CA-MSSA included ST5-t002 (2 strains), ST22-t309 (2 strains), ST398-t034, ST15-t5864, ST7-t091, ST25-t078, ST30-t318, ST121-t1425, ST800-t1425, and ST630-t377. No methicillin-resistant SA (MRSA) strains were detected in this study. CA-MSSA strains have high drug susceptibility and diverse genetic backgrounds. The coexistence of multiple toxins may provide a survival advantage in community dissemination for CA-MSSA.

The Effect of Environmental Conditions on Biofilm Formation of Burkholderia pseudomallei Clinical Isolates

Burkholderia pseudomallei, a Gram-negative saprophytic bacterium, is the causative agent of the potentially fatal melioidosis disease in humans. In this study, environmental parameters including temperature, nutrient content, pH and the presence of glucose were shown to play a role in in vitro biofilm formation by 28 B. pseudomallei clinical isolates, including four isolates with large colony variants (LCVs) and small colony variants (SCVs) morphotypes. Enhanced biofilm formation was observed when the isolates were tested in LB medium, at 30°C, at pH 7.2, and in the presence of as little as 2 mM glucose respectively. It was also shown that all SVCs displayed significantly greater capacity to form biofilms than the corresponding LCVs when cultured in LB at 37°C. In addition, octanoyl-homoserine lactone (C8-HSL), a quorum sensing molecule, was identified by mass spectrometry analysis in bacterial isolates referred to as LCV CTH, LCV VIT, SCV TOM, SCV CTH, 1 and 3, and the presence of other AHL's with higher masses; decanoyl-homoserine lactone (C10-HSL) and dodecanoyl-homoserine lactone (C12-HSL) were also found in all tested strain in this study. Last but not least, we had successfully acquired two Bacillus sp. soil isolates, termed KW and SA respectively, which possessed strong AHLs degradation activity. Biofilm formation of B. pseudomallei isolates was significantly decreased after treated with culture supernatants of KW and SA strains, demonstrating that AHLs may play a role in B. pseudomallei biofilm formation.

In vitro time–kill analysis of oritavancin against clinical isolates of methicillin-resistant Staphylococcus aureus with reduced susceptibility to daptomycin

Oritavancin exhibited lower MIC 50 values (0.03 and 0.5 mg/L) than comparators against methicillin-resistant Staphylococcus aureus (MRSA, n = 50) and vancomycin-intermediate SA strains ( n = 60). At subtherapeutic concentrations, oritavancin demonstrated rapid (within 9 h) and concentration-dependent bactericidal activity against daptomycin nonsusceptible (DNS) MRSA. Further investigations are warranted to determine the therapeutic potential of oritavancin against DNS MRSA.

Antimicrobial Susceptibility Testing of Bacillus anthracis Using the Nccls Broth Microdilution Reference and Etest Agar Gradient Diffusion Methods

Results:Only 1 of 11,836 (0.01%) SA strains exhibited nonsusceptibility to daptomycin (MIC, 2mg/L), and resistance to oxacillin or other antimicrobials did not adversely influence daptomycin activity. Daptomycin was active against enterococci (100.0% susceptible), including strains resistant to vancomycin. Vancomycin-resistant E. faecium increased in Europe from 12.0% in 2004 to 25.8% in 2007 and varied significantly by country. Only 72.1% of E. faeciumwere susceptible to quinupristin/dalfopristin. All VGS strains resistant to penicillin and/or clindamycin and/or levofloxacin were susceptible to daptomycin. CoNS (MIC90, 0.5mg/L) and BHS (MIC 90, 0.25mg/L) were also very susceptible to daptomycin. Conclusions: Daptomycin displayed significant potency and a wide spectrum of activity against problematic clinical isolates of Gram-positive cocci causing nosocomial infections in European hospitals, including MDR subsets. Daptomycin activity remained stable over the 5 year period evaluated and resistance to other antimicrobial classes did not adversely affect the high daptomycin activity.

Relation between phylogenetic position, lipid metabolism and butyrate production by different Butyrivibrio-like bacteria from the rumen

The Butyrivibrio group comprises Butyrivibrio fibrisolvens and related Gram-positive bacteria isolated mainly from the rumen of cattle and sheep. The aim of this study was to investigate phenotypic characteristics that discriminate between different phylotypes. The phylogenetic position, derived from 16S rDNA sequence data, of 45 isolates from different species and different countries was compared with their fermentation products, mechanism of butyrate formation, lipid metabolism and sensitivity to growth inhibition by linoleic acid (LA). Three clear sub-groups were evident, both phylogenetically and metabolically. Group VA1 typified most Butyrivibrio and Pseudobutyrivibrio isolates, while Groups VA2 and SA comprised Butyrivibrio hungatei and Clostridium proteoclasticum, respectively. All produced butyrate but strains of group VA1 had a butyrate kinase activity <40 U (mg protein)(-1), while strains in groups VA2 and SA all exhibited activities >600 U (mg protein)(-1). The butyrate kinase gene was present in all VA2 and SA bacteria tested but not in strains of group VA1, all of which were positive for the butyryl-CoA CoA-transferase gene. None of the bacteria tested possessed both genes. Lipase activity, measured by tributyrin hydrolysis, was high in group VA2 and SA strains and low in Group VA1 strains. Only the SA group formed stearic acid from LA. Linoleate isomerase activity, on the other hand, did not correspond with phylogenetic position. Group VA1 bacteria all grew in the presence of 200 microg LA ml(-1), while members of Groups VA2 and SA were inhibited by lower concentrations, some as low as 5 microg ml(-1). This information provides strong links between phenotypic and phylogenetic properties of this group of clostridial cluster XIVa Gram-positive bacteria.