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1.
Staphylococcus aureus and Pseudomonas aeruginosa are rapidly increasing as multidrug resistant strains worldwide. In nosocomial settings because of heavy exposure of different antimicrobials, resistance in these pathogens turned into a grave issue in both developed and developing countries. The aim of this study was to investigate in vitro antibiotic synergism of combinations of β-lactam–β-lactam and β-lactam–aminoglycoside against clinical isolates of S. aureus and P. aeruginosa. Synergy was determined by checkerboard double dilution method. The combination of amoxicillin and cefadroxil was found to be synergistic against 47 S. aureus isolates, in the FICI range of 0.14–0.50 (81.03%) followed by the combination of streptomycin and cefadroxil synergistic against 44 S. aureus isolates in the FICI range of 0.03–0.50 (75.86%). The combination of streptomycin and cefadroxil was observed to be synergistic against 39 P. aeruginosa isolates in the FICI range of 0.16–0.50 (81.28%). Further actions are needed to characterize the possible interaction mechanism between these antibiotics. Moreover, the combination of streptomycin and cefadroxil may lead to the development of a new and vital antimicrobial against simultaneous infections of S. aureus and P. aeruginosa. 相似文献
2.
A bacterial strain, designated BzDS03 was isolated from water sample, collected from Dal Lake Srinagar. The strain was characterized by using 16S ribosomal RNA gene and 16S-23S rRNA internal transcribed spacer region sequences. Phylogenetic analysis showed that 16S rRNA sequence of the isolate formed a monophyletic clade with genera Escherichia. The closest phylogenetic relative was Escherichia coli with 99% 16S rRNA gene sequence similarity. The result of Ribosomal database project's classifier tool revealed that the strain BzDS03 belongs to genera Escherichia.16S rRNA sequence of isolate was deposited in GenBank with accession number FJ961336. Further analysis of 16S-23S rRNA sequence of isolate confirms that the identified strain BzDS03 be assigned as the type strain of Escherichia coli with 98% 16S-23S rRNA sequence similarity. The GenBank accession number allotted for 16S-23S rRNA intergenic spacer sequence of isolate is FJ961337. 相似文献
3.
We describe the development and application of a Pooled Suppression Subtractive Hybridization (PSSH) method to describe differences between the genomic content of a pool of clinical Staphylococcus aureus isolates and a sequenced reference strain. In comparative bacterial genomics, Suppression Subtractive Hybridization (SSH) is normally utilized to compare genomic features or expression profiles of one strain versus another, which limits its ability to analyze communities of isolates. However, a PSSH approach theoretically enables the user to characterize the entirety of gene content unique to a related group of isolates in a single reaction. These unique fragments may then be linked to individual isolates through standard PCR. This method was applied to examine the genomic diversity found in pools of S.aureus isolates associated with complicated bacteremia infections leading to endocarditis and osteomyelitis. Across four pools of 10 isolates each, four hundred and twenty seven fragments not found in or significantly divergent from the S. aureus NCTC 8325 reference genome were detected. These fragments could be linked to individual strains within its pool by PCR. This is the first use of PSSH to examine the S. aureus pangenome. We propose that PSSH is a powerful tool for researchers interested in rapidly comparing the genomic content of multiple unstudied isolates. 相似文献
4.
5.
Zhihong Gui Huafu Wang Ting Ding Wei Zhu Xiyi Zhuang Weihua Chu 《Indian journal of microbiology》2014,54(1):114-117
Staphylococcus aureus causes a broad range of life-threatening diseases in humans. This bacterium produces a large number of extracellular virulence factors that are closely associated with specific diseases which are controlled by quorum sensing. In this study, we show that azithromycin was active against methicillin-resistant Staphylococcus aureus (MRSA) strains with MICs ranged from 32 to 64 μg/mL. Azithromycin at subinhibitory concentration, markedly reduced the production of α-hemolysin at (1/16MIC, 1/8MIC) and biofilm formation at (1/16MIC, 1/8MIC), respectively. The results indicated that sub-inhibitory concentrations of azithromycin decreased the production of α-hemolysin and biofilm formation in MRSA in a dose-dependent manner. Therefore, azithromycin may be useful in the treatment of α-hemolysin producing and biofilm formation MRSA infections. 相似文献
6.
SsrA RNA (small stable RNA A), also known as tmRNA and 10Sa RNA, functions both as tRNA and mRNA through its unique structure. The carotenoid pigment is the eponymous feature of human pathogen Staphylococcus aureus. Here, we found that the pigment of the mutant strain with ssrA deletion was increased. Furthermore, it was demonstrated that ssrA could act as an antisense RNA aside from its well-known biological function, and crtMN, encoding two essential enzymes for the pigment synthesis, was identified as target of ssrA. Further investigation showed ssrA could specifically base pair with the RBS (ribosomal binding site) region of the crtMN mRNA. Our results revealed a new mechanism by which ssrA regulated the biosynthesis of pigment in S. aureus. 相似文献
7.
The intermediates in the ribosome assembly in exponentially growing Escherichia coli have been identified by centrifuging a crude lysate, pulse-labeled with a radioactive RNA base, through a sucrose gradient and analyzing for precursor rRNA in the gradient fractions by gel electrophoresis. The major intermediate in the assembly of the 50 S subunit cosediments with the mature subunit, whereas two minor precursor species sediment between the 30 S and 50 S peaks. The assembly of the 30 S subunit proceeds via a minor intermediate sedimenting slightly behind the mature subunit and a major precursor particle that cosediments with the mature 30 S subunit.The fraction of the rRNA contained in these precursor particles was determined by direct determination of the amount of rRNA in the precursor particles, and from the labeling kinetics of their rRNA. The direct estimation indicated that about 2% of the total 23 S type RNA, and 3 to 5% of the total 16 S type RNA is harboured in precursor particles. In the kinetic experiments the specific activity of the nucleoside triphosphates and of the different ribosomal particles was followed after addition of a radioactive RNA precursor to the growth medium. The results were compared with a digital simulation of the flow of isotopes through the assembly pathways. This method indicated that approximately 2% of the total 23 S type RNA, as well as 2% of the total 16 S type RNA, is contained in the precursor particles. 相似文献
8.
Staphylococcus aureus is a Gram-positive pathogen that causes opportunistic infections and a wide variety of diseases. Methicillin-resistant S. aureus (MRSA) is frequently isolated as multidrug-resistant in nosocomial and community infections. Molecular genetic manipulation is an important tool for understanding the molecular mechanism of S. aureus infection. However the number of available antibiotic markers is limited due to multidrug resistance. In this study, we constructed two Escherichia coli-S. aureus shuttle vectors, pKFT and pKFC, that carry a temperature-sensitive origin of replication in S. aureus, lacZ(a) enabling a simple blue-white screening in E. coli, an ampicillin resistant gene, and either a tetracycline resistance gene or a chloramphenicol resistance gene. We report a simple technique using pKFT to construct a markerless gene deletion mutant in S. aureus by allelic replacement without the use of a counter-selection marker. Subculture twice at 25 °C was critical to promote an allelic exchange rate in S. aureus. This technique is very simple and useful to facilitate genetic research on S. aureus. 相似文献
9.
Delphine Patin Audrey Boniface Andreja Kovač Mireille Hervé Sébastien Dementin Hélène Barreteau Dominique Mengin-Lecreulx Didier Blanot 《Biochimie》2010
The Mur ligases (MurC, MurD, MurE and MurF) catalyze the stepwise synthesis of the UDP-N-acetylmuramoyl-pentapeptide precursor of peptidoglycan. The murC, murD, murE and murF genes from Staphylococcus aureus, a major pathogen, were cloned and the corresponding proteins were overproduced in Escherichia coli and purified as His6-tagged forms. Their biochemical properties were investigated and compared to those of the E. coli enzymes. Staphylococcal MurC accepted l-Ala, l-Ser and Gly as substrates, as the E. coli enzyme does, with a strong preference for l-Ala. S. aureus MurE was very specific for l-lysine and in particular did not accept meso-diaminopimelic acid as a substrate. This mirrors the E. coli MurE specificity, for which meso-diaminopimelic acid is the preferred substrate and l-lysine a very poor one. S. aureus MurF appeared less specific and accepted both forms (l-lysine and meso-diaminopimelic acid) of UDP-MurNAc-tripeptide, as the E. coli MurF does. The inverse and strict substrate specificities of the two MurE orthologues is thus responsible for the presence of exclusively meso-diaminopimelic acid and l-lysine at the third position of the peptide in the peptidoglycans of E. coli and S. aureus, respectively. The specific activities of the four Mur ligases were also determined in crude extracts of S. aureus and compared to cell requirements for peptidoglycan biosynthesis. 相似文献
10.
Zhou J Tun TN Hong SH Mercer-Chalmers JD Laabei M Young AE Jenkins AT 《Biosensors & bioelectronics》2011,30(1):67-72
A new methodology for detecting the microbiological state of a wound dressing in terms of its colonization with pathogenic bacteria such as Staphylococcus aureus or Pseudomonas aeruginosa has been developed. Here we report how stabilized lipid vesicles containing self-quenched carboxyfluorescein dye are sensitive to lysis only by toxins/virulence factors from P. aeruginosa and S. aureus but not by a non-toxic Escherichia coli species. The development of the stabilized vesicles is discussed and their response to detergent (triton), bacterial toxin (α-hemolysin) and lipases (phospholipase A2). Finally, fabrics with stabilized vesicles attached via plasma deposited maleic anhydride coupling are shown visibly responding to S. aureus (MSSA 476) and P. aeruginosa (PAO1) but not E. coli DH5α in a prototype dressing. 相似文献
11.
Cheryl R Kuske Chris M Yeager Shannon Johnson Lawrence O Ticknor Jayne Belnap 《The ISME journal》2012,6(4):886-897
The impact of 10 years of annual foot trampling on soil biocrusts was examined in replicated field experiments at three cold desert sites of the Colorado Plateau, USA. Trampling detrimentally impacted lichens and mosses, and the keystone cyanobacterium, Microcoleus vaginatus, resulting in increased soil erosion and reduced C and N concentrations in surface soils. Trampled biocrusts contained approximately half as much extractable DNA and 20–52% less chlorophyll a when compared with intact biocrusts at each site. Two of the three sites also showed a decline in scytonemin-containing, diazotrophic cyanobacteria in trampled biocrusts. 16S rRNA gene sequence and terminal restriction fragment length polymorphism (T-RFLP) analyses of soil bacteria from untrampled and trampled biocrusts demonstrated a reduced proportion (23–65% reduction) of M. vaginatus and other Cyanobacteria in trampled plots. In parallel, other soil bacterial species that are natural residents of biocrusts, specifically members of the Actinobacteria, Chloroflexi and Bacteroidetes, became more readily detected in trampled than in untrampled biocrusts. Replicate 16S rRNA T-RFLP profiles from trampled biocrusts at all three sites contained significantly more fragments (n=17) than those of untrampled biocrusts (n⩽6) and exhibited much higher variability among field replicates, indicating transition to an unstable disturbed state. Despite the dramatic negative impacts of trampling on biocrust physical structure and composition, M. vaginatus could still be detected in surface soils after 10 years of annual trampling, suggesting the potential for biocrust re-formation over time. Physical damage of biocrusts, in concert with changing temperature and precipitation patterns, has potential to alter performance of dryland ecosystems for decades. 相似文献
12.
Keven M Robinson Benjamin Lee Erich V Scheller Sivanarayana Mandalapu Richard I Enelow Jay K Kolls John F Alcorn 《Respiratory research》2015,16(1)
Background
Influenza is a common respiratory virus and Staphylococcus aureus frequently causes secondary pneumonia during influenza infection, leading to increased morbidity and mortality. Influenza has been found to attenuate subsequent Type 17 immunity, enhancing susceptibility to secondary bacterial infections. IL-27 is known to inhibit Type 17 immunity, suggesting a potential critical role for IL-27 in viral and bacterial co-infection.Methods
A murine model of influenza and Staphylococcus aureus infection was used to mimic human viral, bacterial co-infection. C57BL/6 wild-type, IL-27 receptor α knock-out, and IL-10 knock-out mice were infected with Influenza H1N1 (A/PR/8/34) or vehicle for 6 days followed by challenge with Staphylococcus aureus or vehicle for 24 hours. Lung inflammation, bacterial burden, gene expression, and cytokine production were determined.Results
IL-27 receptor α knock-out mice challenged with influenza A had increased morbidity compared to controls, but no change in viral burden. IL-27 receptor α knock-out mice infected with influenza displayed significantly decreased IL-10 production compared to wild-type. IL-27 receptor α knock-out mice co-infected with influenza and S. aureus had improved bacterial clearance compared to wild-type controls. Importantly, there were significantly increased Type 17 responses and decreased IL-10 production in IL-27 receptor α knock-out mice. Dual infected IL-10−/− mice had significantly less bacterial burden compared to dual infected WT mice.Conclusions
These data reveal that IL-27 regulates enhanced susceptibility to S. aureus pneumonia following influenza infection, potentially through the induction of IL-10 and suppression of IL-17. 相似文献13.
14.
Robyn Kroop Shaffer 《The Yale journal of biology and medicine》2013,86(2):261-270
In the late 1940s, epidemics of antibiotic-resistant strains of
Staphylococcus
aureus began to plague postpartum nurseries in hospitals
across the United States. Exacerbated by overcrowding and nursing shortages,
resistant S. aureus outbreaks posed a novel challenge to
physicians and nurses heavily reliant on antibiotics as both prophylaxis and
treatment. This paper explores the investigation of the reservoir, mode of
transmission, and virulence of S. aureus during major hospital
outbreaks and the subsequent implementation of novel infection control measures
from the late 1940s through the early 1960s. The exploration of these measures
reveals a shift in infection control policy as hospitals, faced with the failure
of antibiotics to slow S. aureus outbreaks, implemented
laboratory culture routines, modified nursery structure and layout, and altered
nursing staff procedures to counter various forms of S. aureus
transmission. Showcasing the need for widespread epidemiologic surveillance,
ultimately manifesting itself in specialized “hospital epidemiology” training
promoted in the 1970s, the challenges faced by hospital nurses in the 1950s
prove highly relevant to the continued struggle with methicillin-resistant
Staphylococcus
aureus (MRSA) and other resistant nosocomial
infections. 相似文献
15.
Nyree J West Philippe Lebaron Pete G Strutton Marcelino T Suzuki 《The ISME journal》2011,5(6):933-944
A novel high-light (HL)-adapted Prochlorococcus clade was discovered in high nutrient and low chlorophyll (HNLC) waters in the South Pacific Ocean by phylogenetic analyses of 16S ribosomal RNA (rRNA) and 16S–23S internal transcribed spacer (ITS) sequences. This clade, named HNLC fell within the HL-adapted Prochlorococcus clade with sequences above 99% similarity to one another, and was divided into two subclades, HNLC1 and HNLC2. The distribution of the whole HNLC clade in a northwest to southeast transect in the South Pacific (HNLC-to-gyre) and two 8°N to 8°S transects in the Equatorial Pacific was determined by quantitative PCR using specific primers targeting ITS regions. HNLC was the dominant HL Prochlorococcus clade (2–9% of bacterial 16S rRNA genes) at the three westernmost stations in the South Pacific but decreased to less than 0.1% at the other stations being replaced by the eMIT9312 ecotype in the hyperoligotrophic gyre. The highest contributions of HNLC Prochlorococcus in both Equatorial Pacific transects along the latitudinal lines of 170°W and 155°W were observed at the southernmost stations, reaching 16 and 6% of bacterial 16S rRNA genes, respectively, whereas eMIT9312 dominated near the Equator. Spearman Rank Order correlation analysis indicated that although both the HNLC clade and eMIT9312 were correlated with temperature, they showed different correlations with regard to nutrients. HNLC only showed significant correlations to ammonium uptake and regeneration rates, whereas eMIT9312 was negatively correlated with inorganic nutrients. 相似文献
16.
The maturation of ribosomal RNAs (rRNAs) is an important but incompletely understood process required for rRNAs to become functional. In order to determine the enzymes responsible for initiating 3' end maturation of 23S rRNA in Escherichia coli, we analyzed a number of strains lacking different combinations of 3' to 5' exo-RNases. Through these analyses, we identified RNase PH as a key effector of 3' end maturation. Further analysis of the processing reaction revealed that the 23S rRNA precursor contains a CC dinucleotide sequence that prevents maturation from being performed by RNase T instead. Mutation of this dinucleotide resulted in a growth defect, suggesting a strategic significance for this RNase T stalling sequence to prevent premature processing by RNase T. To further explore the roles of RNase PH and RNase T in RNA processing, we identified a subset of transfer RNAs (tRNAs) that contain an RNase T stall sequence, and showed that RNase PH activity is particularly important to process these tRNAs. Overall, the results obtained point to a key role of RNase PH in 23S rRNA processing and to an interplay between this enzyme and RNase T in the processing of different species of RNA molecules in the cell. 相似文献
17.
Yousry Hawash 《The Korean journal of parasitology》2014,52(3):263-271
PCR detection of intestinal protozoa is often restrained by a poor DNA recovery or by inhibitors present in feces. The need for an extraction protocol that can overcome these obstacles is therefore clear. QIAamp® DNA Stool Mini Kit (Qiagen) was evaluated for its ability to recover DNA from oocysts/cysts directly from feces. Twenty-five Giardia-positive, 15 Cryptosporidium-positive, 15 Entamoeba histolytica-positive, and 45 protozoa-free samples were processed as control by microscopy and immunoassay tests. DNA extracts were amplified using 3 sets of published primers. Following the manufacturer''s protocol, the kit showed sensitivity and specificity of 100% towards Giardia and Entamoeba. However, for Cryptosporidium, the sensitivity and specificity were 60% (9/15) and 100%, respectively. A series of optimization experiments involving various steps of the kit''s protocol were conducted using Cryptosporidium-positive samples. The best DNA recoveries were gained by raising the lysis temperature to the boiling point for 10 min and the incubation time of the InhibitEX tablet to 5 min. Also, using a pre-cooled ethanol for nucleic acid precipitation and small elution volume (50-100 µl) were valuable. The sensitivity of the amended protocol to Cryptosporidium was raised to 100%. Cryptosporidium DNA was successfully amplified by either the first or the second primer set. When applied on parasite-free feces spiked with variable oocysts/cysts counts, ≈ 2 oocysts/cysts were theoretically enough for detection by PCR. To conclude, the Qiagen kit with the amended protocol was proved to be suitable for protozoan DNA extraction directly from feces and support PCR diagnosis. 相似文献
18.
Kathleen M. Frey 《Journal of molecular biology》2009,387(5):1298-1308
Both hospital- and community-acquired Staphylococcus aureus infections have become major health concerns in terms of morbidity, suffering and cost. Trimethoprim-sulfamethoxazole (TMP-SMZ) is an alternative treatment for methicillin-resistant S. aureus (MRSA) infections. However, TMP-resistant strains have arisen with point mutations in dihydrofolate reductase (DHFR), the target for TMP. A single point mutation, F98Y, has been shown biochemically to confer the majority of this resistance to TMP. Using a structure-based approach, we have designed a series of novel propargyl-linked DHFR inhibitors that are active against several trimethoprim-resistant enzymes. We screened this series against wild-type and mutant (F98Y) S. aureus DHFR and found that several are active against both enzymes and specifically that the meta-biphenyl class of these inhibitors is the most potent. In order to understand the structural basis of this potency, we determined eight high-resolution crystal structures: four each of the wild-type and mutant DHFR enzymes bound to various propargyl-linked DHFR inhibitors. In addition to explaining the structure-activity relationships, several of the structures reveal a novel conformation for the cofactor, NADPH. In this new conformation that is predominantly associated with the mutant enzyme, the nicotinamide ring is displaced from its conserved location and three water molecules complete a network of hydrogen bonds between the nicotinamide ring and the protein. In this new position, NADPH has reduced interactions with the inhibitor. An equilibrium between the two conformations of NADPH, implied by their occupancies in the eight crystal structures, is influenced both by the ligand and the F98Y mutation. The mutation induced equilibrium between two NADPH-binding conformations may contribute to decrease TMP binding and thus may be responsible for TMP resistance. 相似文献
19.
Two-component systems (TCSs) are widely employed by bacteria to sense specific external signals and conduct an appropriate response via a phosphorylation cascade within the cell. The TCS of the agr operon in the bacterium Staphylococcus aureus forms part of a regulatory process termed quorum sensing, a cell-to-cell communication mechanism used to assess population density. Since S. aureus manipulates this “knowledge” in order to co-ordinate production of its armoury of exotoxin virulence factors required to promote infection, it is important to understand fully how this process works. We present three models of the agr operon, each incorporating a different phosphorylation cascade for the TCS since the precise nature of the cascade is not fully understood. Using numerical and asymptotic techniques we examine the effects of inhibitor therapy, a novel approach to controlling bacterial infection through the attenuation of virulence, on each of these three cascades. We present results which, if evaluated against appropriate experimental data, provide insights into the potential effectiveness of such therapy. Moreover, the TCS models presented here are of broad relevance given that TCSs are widely conserved throughout the bacterial kingdom. 相似文献