Synthesis and antibacterial activity of some new derivatives of pyrazole

In this study, we report the synthesis and antibacterial activity of a new series of 5-amido-1-(2,4-dinitrophenyl)-1H-4-pyrazolecarbonitriles. Our results show that all compounds exhibit antimicrobial activities against methicillin susceptible Staphylococcus aureus and methicillin resistant S. aureus with MIC values of 25.1 and 91.0 μM.     

Clinical and Epidemiological Factors Associated with Methicillin Resistance in Community-Onset Invasive Staphylococcus aureus Infections: Prospective Multicenter Cross-Sectional Study in Korea

Successful empirical therapy of Staphylococcus aureus infections requires the ability to predict methicillin resistance. Our aim was to identify predictors of methicillin resistance in community-onset (CO) invasive S. aureus infections. Sixteen hospitals across Korea participated in this study from May to December 2012. We prospectively included cases of S. aureus infection in which S. aureus was isolated from sterile clinical specimens ≤72 hours after hospitalization. Clinical and epidemiological data were gathered and compared in methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) cases. Community-associated (CA) infections were defined as in previous studies. In total, there were 786 cases of community-onset S. aureus infection, 102 (13.0%) of which were CA-MRSA. In addition to known risk factors, exposure to 3rd generation cephalosporins in the past 6 months [odds ratio (OR), 1.922; 95% confidence interval (CI), 1.176–3.142] and close contact with chronically ill patients in the past month (OR, 2.647; 95% CI, 1.189–5.891) were independent risk factors for MRSA infection. However, no clinical predictors of CA-MRSA were identified. Methicillin resistance, CO infection, and appropriateness of empirical antibiotics were not significantly related to 30-day mortality. MRSA infection should be suspected in patients recently exposed to 3rd generation cephalosporins or chronically-ill patients. There were no reliable predictors of CA-MRSA infection, and mortality was not affected by methicillin resistance.     

Novel Inhibitors of Staphylococcus aureus Virulence Gene Expression and Biofilm Formation

Staphylococcus aureus is a major human pathogen and one of the more prominent pathogens causing biofilm related infections in clinic. Antibiotic resistance in S. aureus such as methicillin resistance is approaching an epidemic level. Antibiotic resistance is widespread among major human pathogens and poses a serious problem for public health. Conventional antibiotics are either bacteriostatic or bacteriocidal, leading to strong selection for antibiotic resistant pathogens. An alternative approach of inhibiting pathogen virulence without inhibiting bacterial growth may minimize the selection pressure for resistance. In previous studies, we identified a chemical series of low molecular weight compounds capable of inhibiting group A streptococcus virulence following this alternative anti-microbial approach. In the current study, we demonstrated that two analogs of this class of novel anti-virulence compounds also inhibited virulence gene expression of S. aureus and exhibited an inhibitory effect on S. aureus biofilm formation. This class of anti-virulence compounds could be a starting point for development of novel anti-microbial agents against S. aureus.     

Intragenus generalized transduction in Staphylococcus spp. by a novel giant phage

Bacteriophage (phage)-mediated generalized transduction is expected to contribute to the emergence of drug-resistant staphylococcal clones in various environments. In this study, novel phage S6 was isolated from sewage and used to test generalized transduction in human- and animal-derived staphylococci. Phage S6 was a novel type of giant myophage, which possessed a DNA genome that contained uracil instead of thymine, and it could infect all of the tested staphylococcal species. The phage S6 appeared to be similar to the transducing phage PBS1, which infects Bacillus spp. Moreover, phage S6 facilitated the transduction of a plasmid in Staphylococcus aureus and from S. aureus to non-aureus staphylococcal species, as well as vice versa. Transduction of methicillin resistance also occurred in S. aureus. This is the first report of successful intragenus generalized transduction among staphylococci.     

Epidemiology of Staphylococcus aureus Bacteraemia at a Tertiary Children’s Hospital in Cape Town,South Africa

Background

Staphylococcus aureus is an important pathogen in paediatric patients with bloodstream infections. The epidemiology of S. aureus bacteraemia, however, has not been well documented in children in South Africa.

Methods

A retrospective study was conducted at a children’s hospital in Cape Town, South Africa, to investigate the epidemiology of S. aureus bacteraemia from 2007-2011. The incidence, clinical presentation, risk factors, management and outcomes of methicillin sensitive S. aureus (MSSA) and methicillin resistant S. aureus (MRSA) bacteraemia were compared.

Results

Over the five year study period, 365 episodes of S. aureus bacteraemia were identified. The annual incidence was 3.28 cases per 1000 hospital admissions. MRSA was responsible for 26% of S. aureus bacteraemia and 72% of nosocomial infections. Only six possible cases of community-acquired MRSA infections were described. MSSA bacteraemia was more likely to present as pulmonary and bone or joint infections, while bacteraemia without a source was the most common presentation with MRSA.  Infants, children with malnutrition, and residents of long-term care facilities were at highest risk for MRSA bacteraemia. The overall case fatality rate for S. aureus bacteraemia was 8.8% over five years, with MRSA being the only significant risk factor for mortality.

Conclusion

The incidence of S. aureus bacteraemia and MRSA bacteraemia in children has remained stable over the past five years. MRSA is a predominantly nosocomial pathogen in children with S. aureus bacteraemia in Cape Town, South Africa.     

Exploring extra-cellular proteins in methicillin susceptible and methicillin resistant Staphylococcus aureus by liquid chromatography–tandem mass spectrometry

Staphylococcus aureus (S. aureus) strains cause several diseases in humans from minor skin infections to severe lethal infections. To explore the virulence determinants of this important microorganism, two clinical isolates of methicillin susceptible S. aureus (MSSA) and methicillin resistant S. aureus (MRSA) were subjected to proteomic analysis of their extracellular products using liquid chromatography–tandem mass spectrometry. The numbers of proteins identified in MSSA and MRSA extracellular products were 168 and 261; respectively, from them 117 were shared, while 144 proteins were unique to MRSA. The shared proteins, having a higher protein score with increased number of peptide matches in MRSA over MSSA, reflect the relatively active secretory state of MRSA rather than biased analytical variances. Characteristic determinants for MRSA were identified; mostly found to play a role in the virulence. We conclude that MRSA produces distinct proteins considered as its virulence determinants and we found that the shared extracellular products are more abundant in MRSA than MSSA that supporting the high invasiveness of MRSA over MSSA in pathogenesis.     

Antimicrobial effect of different types of honey on Staphylococcus aureus

Honey exhibits antimicrobial activities against a wide range of bacteria in different milieu. This study aims to compare the effects of five types of honey (both imported and local Saudi honey) against Staphylococcus aureus. The five types of honey (Manuka Honey UMF +20, Manuka Honey UMF +16, Active +10 Manuka Honey, Sidr honey and Nigella sativa honey) were evaluated for their bactericidal/bacteriostatic activities against both methicillin resistant and sensitive S. aureus. The inhibitory effect of honey on bacterial growth was evident at concentrations of 20% and 10% (v/v). Manuka Honey showed the best results. Manuka Honey UMF +20 had a bactericidal effect on both methicillin resistant and sensitive S. aureus. However, Sidr and N. sativa honey exerted only a bacteriostatic effect. The efficacy of different types of honey against S. aureus was dependent on the type of honey and the concentration at which it was administered. Manuka Honey had the best bactericidal activity. Future experiments should be conducted to evaluate the effects of honey on bacterial resistance.     

Novel targets of pentacyclic triterpenoids in Staphylococcus aureus: A systematic review

BackgroundStaphylococcus aureus is an important pathogen both in community-acquired and healthcare-associated infections, and has successfully evolved numerous strategies for resisting the action to practically all antibiotics. Resistance to methicillin is now widely described in the community setting (CMRSA), thus the development of new drugs or alternative therapies is urgently necessary. Plants and their secondary metabolites have been a major alternative source in providing structurally diverse bioactive compounds as potential therapeutic agents for the treatment of bacterial infections. One of the classes of natural secondary metabolites from plants with the most bioactive compounds are the triterpenoids, which comprises structurally diverse organic compounds. In nature, triterpenoids are often found as tetra- or penta-cyclic structures.AimThis review highlights the anti-staphylococcal activities of pentacyclic triterpenoids, particularly α-amyrin (AM), betulinic acid (BA) and betulinaldehyde (BE). These compounds are based on a 30-carbon skeleton comprising five six-membered rings (ursanes and lanostanes) or four six-membered rings and one five-membered ring (lupanes and hopanes).MethodsElectronic databases such as ScienceDirect, PubMed and Scopus were used to search scientific contributions until March 2018, using relevant keywords. Literature focusing on the antimicrobial and antibiofilms of effects of pentacyclic triterpenoids on S. aureus were identified and summarized.ResultsPentacyclic triterpenoids can be divided into three representative classes, namely ursane, lupane and oleananes. This class of compounds have been shown to exhibit analgesic, immunomodulatory, anti-inflammatory, anticancer, antioxidant, antifungal and antibacterial activities. In studies of the antimicrobial activities and targets of AM, BA and BE in sensitive and multidrug-resistant S. aureus, these compounds acted synergistically and have different targets from the conventional antibiotics.ConclusionThe inhibitory mechanisms of S. aureus in novel targets and pathways should stimulate further researches to develop AM, BA and BE as therapeutic agents for infections caused by S. aureus. Continued efforts to identify and exploit synergistic combinations by the three compounds and peptidoglycan inhibitors, are also necessary as alternative treatment options for S. aureus infections.     

Complication of radiation therapy among patients with positive S. aureus culture from genital tract

AimThe main goal of this investigation was to evaluate the influence of positive Staphylococcus aureus culture from the genital tract on patients receiving radiation therapy, suffering from carcinoma of the uterus. The other aim was to observe radiation therapy complications.BackgroundRadiation therapy of patients suffering from cervical cancer can be connected with inflammation of the genitourinary tract.Materials and methodsIn years 2006–2010 vaginal swabs from 452 patients were examined. 39 women with positive S. aureus cultures were analysed.ResultsComplications and interruptions during radiation therapy were observed in 7 (18.9%) of 37 patients with positive vaginal S. aureus culture. One of them, a 46-year-old woman developed pelvic inflammatory disease. None of the six patients who received palliative radiotherapy showed interruption in this treatment. Isolated S. aureus strains were classified into 13 sensitivity patterns, of which 8 were represented by 1 strain, two by 2 strains and three by 13, 8 and 6 strains. One strain was diagnosed as methicillin resistant S. aureus (MRSA).ConclusionsThe results of the present study show that S. aureus may generally be isolated from the genital tract of female patients with neoplastic disease of uterus but is not often observed as inflammation factor of this tract. Comparison of species’ resistance patterns may be used in epidemiological studies in order to discover the source of infections and therefore be of profound significance in the prevention of nosocomial infections.     

Design,synthesis and molecular modeling studies of new series of s-triazine derivatives as antimicrobial agents against multi-drug resistant clinical isolates

Three novel series of s-triazine derivatives, including thirty-five new compounds 2a-d, 3a-3p, 4b-d, 5b-d, 6d-6d, and 7a-7f were synthesized comprising a diversity of substituents based on the structure of Astrazeneca arylaminotriazine DNA gyrase B inhibitor. The antimicrobial activity was determined for all compounds against Staphylococcus aureus, Escherichia coli and Candida albicans using the two-fold serial dilution technique and against reference standards Ampicillin for the antibacterial screening and Clotrimazole regarding the antifungal evaluation. The tested compounds showed strong to moderate antibacterial inhibitory action and weak antifungal activity. Compounds 3j and 6b were the most potent antibacterial agents against the tested strains and multi-drug resistant (MDR) clinical isolates of Klebsiella pneumoniae and methicillin resistant Staphylococcus aureus (MRSA1) with minimal toxicity in comparison to the reference drugs. In silico molecular properties calculations and molecular docking study for 3j and 6b revealed that both compounds could be considered as promising antibacterial DNA gyrase B inhibitors.     

Heterogeneous vancomycin-intermediate susceptibility in a community-associated methicillin-resistant Staphylococcus aureus epidemic clone, in a case of Infective Endocarditis in Argentina

Background

There has been considerable effort to discover plant-derived antibacterials against methicillin-resistant strains of Staphylococcus aureus (MRSA) which have developed resistance to most existing antibiotics, including the last line of defence, vancomycin. Pentacyclic triterpenoid, a biologically diverse plant-derived natural product, has been reported to show anti-staphylococcal activities. The objective of this study is to evaluate the interaction between three pentacyclic triterpenoid and standard antibiotics (methicillin and vancomycin) against reference strains of Staphylococcus aureus.

Methods and Results

The activity of the standard antibiotics and compounds on reference methicillin-sensitive and resistant strains of S. aureus were determined using the macrodilution broth method. The minimum inhibitory concentration (MIC) of the compounds was compared with that of the standard antibiotics. The interaction between any two antimicrobial agents was estimated by calculating the fractional inhibitory concentration (FIC index) of the combination. The various combinations of antibiotics and compounds reduced the MIC to a range of 0.05 to 50%.

Conclusion

Pentacyclic triterpenoids have shown anti-staphylococcal activities and although individually weaker than common antibiotics produced from bacteria and fungi, synergistically these compounds may use different mechanism of action or pathways to exert their antimicrobial effects, as implicated in the lowered MICs. Therefore, the use of current antibiotics could be maintained in their combination with plant-derived antibacterial agents as a therapeutic option in the treatment of S. aureus infections.     

Loop-mediated isothermal amplification assays for identification of antiseptic- and methicillin-resistant Staphylococcus aureus

A method for rapid identification of antiseptic- and methicillin-resistant Staphylococcus aureus (MRSA) based on 3 loop-mediated isothermal amplification (LAMP) assays was developed. LAMP targeting the femB gene identified S. aureus with 100% specificity, and LAMP targeting the mecA gene associated with methicillin resistance identified methicillin-resistant staphylococci with 100% specificity. LAMP targeting the qacA/B gene encoding an efflux pump responsible for antiseptic resistance identified high-acriflavine-resistant (MIC ≥ 100 mg/L) MRSA (92.5% positive) and acriflavine-susceptible (MIC < 25 mg/L) MRSA (100% negative). They were performed under the same reaction conditions within 60 min at 63 °C. The combined LAMP assays will be useful for rapid identification of S. aureus isolates and determination of their antibiotic and antiseptic resistance patterns with regard to methicillin and organic cationic substrates.     

Complete genome sequence of methicillin-sensitive Staphylococcus aureus containing a heterogeneic staphylococcal cassette chromosome element

Staphylococcus aureus is a common human bacterium that sometimes becomes pathogenic,causing serious infections.A key feature of S.aureus is its ability to acquire resistance to antibiotics.The presence of the staphylococcal cassette chromosome(SCC) element in serotypes of S.aureus has been confirmed using multiplex PCR assays.The SCC element is the only vector known to carry the mecA gene,which encodes methicillin resistance in S.aureus infections.Here,we report the genome sequence of a novel methicillin-sensitive S.aureus(MSSA) strain:SCC-like MSSA463.This strain was originally erroneously serotyped as methicillin-resistant S.aureus in a clinical laboratory using multiplex PCR methods.We sequenced the genome of SCC-like MSSA463 using pyrosequencing techniques and compared it with known genome sequences of other S.aureus isolates.An open reading frame(CZ049;AB037671) was identified downstream of attL and attR inverted repeat sequences.Our results suggest that a lateral gene transfer occurred between S.aureus and other organisms,partially changing S.aureus infectivity.We propose that attL and attR inverted repeats in S.aureus serve as frequent insertion sites for exogenous genes.     

Isolation and characterization of methicillin-resistantStaphylococcus aureus from livestock and poultry meat

Meat samples from sheep, bovine, camel and poultry were collected from Amman area and were processed and tested for the presence of methicillin (oxacillin) resistantStaphylococcus aureus (MRSA). Identity ofS. aureus was ensured by Gram-staining and a battery of biochemical tests. From 1260 meat samples, 157S. aureus positive isolates were identified. Of the 157 isolates, 30 were resistant to methicillin levels greater than 2 μg/ml and only 15 weremecA-positive MRSA originating mainly from sheep and chicken. Subjecting themecA-positive MRSA to antibiotic susceptibility testing revealed that all isolates were resistant to β-lactam antibiotics (ampicillin, penicillin, and oxacillin) and were sensitive to vancomycin, trimethoprim, chloramphenicol and cephalothin. Randomamplified polymorphic DNA (RAPD) analysis ofmecA-positive animal isolates generated six different patterns. Comparing these results with results of isolates of human origin of our laboratory there is some molecular epidemiological relatedness between both and could be a possible source of infections through consuming contaminated meat products, direct contact or meat processing.     

Genetic Organization of the mecA Region in Methicillin-Susceptible and Methicillin-Resistant Strains of Staphylococcus sciuri

A homolog of the Staphylococcus aureus methicillin resistance gene mecA was recently shown to be ubiquitous in independent isolates of the animal species Staphylococcus sciuri. The mecA gene homolog and regions flanking it were cloned and sequenced from four strains of S. sciuri: strain K1 (ATCC 29062), a representative of S. sciuri subsp. sciuri; two strains (K3 and K8) representing S. sciuri subsp. rodentius; and strain K11, a representative of S. sciuri subsp. carnaticum. Strains K1 and K11 were susceptible to methicillin, while strains K3 and K8 showed heterogeneous resistance. The mecA genes of strains K1 and K11 and one of the two copies of mecA (mecA1) present in strain K3 had virtually identical DNA sequences in the mecA gene and were similar in genetic organization in the flanking regions. In contrast, the single copy of mecA in strain K8 and the second copy of mecA (mecA2) in strain K3 had mecA DNA sequences identical to that of S. aureus mecA, and the mecA region in these two strains was also similar to that of the same region in the S. aureus strain used for comparison. Interestingly, an open reading frame defining an N-terminal truncated polypeptide, NTORF101, with a high degree of homology to a DNA segment in the hypervariable region of methicillin-resistant S. aureus (and also similar to the Escherichia coli gene ugpQ) was also identified downstream of the mecA homolog of strain K11, representing S. sciuri subsp. carnaticum. The ugpQ-like gene is not present in methicillin-susceptible strains of S. aureus. The presence of such a ugpQ-like gene together with the homolog of mecA in strain K11 supports the speculation that these genetic elements may be evolutionary relatives and/or precursors of the genetic determinant of methicillin resistance in S. aureus.     

Molecular features of heterogeneous vancomycin-intermediate Staphylococcus aureus strains isolated from bacteremic patients

Background  

Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) bacteremia is an emerging infection. Our objective was to determine the molecular features of hVISA strains isolated from bacteremic patients and to compare them to methicillin resistant S. aureus (MRSA) and methicillin sensitive S. aureus (MSSA) blood isolates.     

The Giant Protein Ebh Is a Determinant of Staphylococcus aureus Cell Size and Complement Resistance

Staphylococcus aureus USA300, the clonal type associated with epidemic community-acquired methicillin-resistant S. aureus (MRSA) infections, displays the giant protein Ebh on its surface. Mutations that disrupt the ebh reading frame increase the volume of staphylococcal cells and alter the cross wall, a membrane-enclosed peptidoglycan synthesis and assembly compartment. S. aureus ebh variants display increased sensitivity to oxacillin (methicillin) as well as susceptibility to complement-mediated killing. Mutations in ebh are associated with reduced survival of mutant staphylococci in blood and diminished virulence in mice. We propose that Ebh, following its secretion into the cross wall, contributes to the characteristic cell growth and envelope assembly pathways of S. aureus, thereby enabling complement resistance and the pathogenesis of staphylococcal infections.     

Identification of novel bacterial histidine biosynthesis inhibitors using docking,ensemble rescoring,and whole-cell assays

The rapid spread on multidrug-resistant strains of Staphylococcus aureus requires not just novel treatment options, but the development of faster methods for the identification of new hits for drug development. The exponentially increasing speed of computational methods makes a more extensive use in the early stages of drug discovery attractive if sufficient accuracy can be achieved. Computational target identification using systems-level methods suggested the histidine biosynthesis pathway as an attractive target against S. aureus. Potential inhibitors for the pathway were identified through docking, followed by ensemble rescoring, that is sufficiently accurate to justify immediate testing of the identified compounds by whole-cell assays, avoiding the need for time-consuming and often difficult intermediary enzyme assays. This novel strategy is demonstrated for three key enzymes of the S. aureus histidine biosynthesis pathway, which is predicted to be essential for bacterial biomass productions. Virtual screening of a library of ～10⁶ compounds identified 49 potential inhibitors of three enzymes of this pathway. Eighteen representative compounds were directly tested on three S. aureus- and two Escherichia coli strains in standard disk inhibition assays. Thirteen compounds are inhibitors of some or all of the S. aureus strains, while 14 compounds weakly inhibit growth in one or both E. coli strains. The high hit rate obtained from a fast virtual screen demonstrates the applicability of this novel strategy to the histidine biosynthesis pathway.     

Detection of methicillin-resistance (mec-A) gene inStaphylococcus aureus strains by PCR and determination of antibiotic susceptibility

Methicillin-ResistantStaphylococcus aureus (MSRA) has become a frequent cause of serious infections. Extended hospitalization and antibiotic therapy have been identified as additional risk factors for MRSA carrier and infection. The aim of this study was to determine the incidence of MRSA infections in the hospitals affiliated to Hamedan University of Medical Sciences. SeventyS. aureus clinical strains were isolated from patients from June 2005 to June 2006 and examined by PCR and conventional microbiological tests. Then, the antibiotic susceptibility to methicillin/oxacillin and other antibiotics were performed by Disc Diffusion Agar (DDA). The results of this study showed that methicillin resistance gene was detected in 35 (50%) and 22 (31.4%) cases by PCR and DDA, respectively. The results of antibiotic susceptibility assays also showed there were high resistance MRSA strains to penicilin (100%), cloxacillin (91.4%), tetracycline (74.2%), cotrimoxazole (68.5%), erythromycin (68.5%) and less resistance to rifampin (11.4). Two MRSA also had decreased susceptibility to vancomycin. But the strains of Methicillin-SensitiveS. aureus (MSSA) showed high sensitivity to all antibiotics profiles except to penicillin (complete resistance). As a conclusion, the resistance to methicillin/oxacillin ofS. aureus in Hamedan hospitals has reached to 50% and they show multidrug resistance.