Treatment Of Staphylococcal Infections Research Articles

Polyclonal but not monoclonal circulating memory CD4+ T cells attenuate the severity of Staphylococcus aureus bacteremia.

Staphylococcus aureus bacteremia causes significant morbidity and mortality. Treatment of staphylococcal infections is hindered by widespread antibiotic resistance, and attempts to develop an S. aureus vaccine have failed. Improved S. aureus treatment and infection prevention options require a deeper understanding of the correlates of protective immunity. CD4+ T cells have been identified as key orchestrators in the defense against S. aureus, but uncertainties persist regarding the subset, polarity, and breadth of the memory CD4+ T-cell pool required for protection. Here, using a mouse model of systemic S. aureus infection, we discovered that the breadth of bacterium-specific memory CD4+ T-cell pool is a critical factor for protective immunity against invasive S. aureus infections. Seeding mice with a monoclonal bacterium-specific circulating memory CD4+ T-cell population failed to protect against systemic S. aureus infection; however, the introduction of a polyclonal and polyfunctional memory CD4+ T-cell pool significantly reduced the bacterial burden. Our findings support the development of a multi-epitope T-cell-based S. aureus vaccine, as a strategy to mitigate the severity of S. aureus bacteremia.

Profile of antibiotic resistance of Staphylococcus aureus isolated from patients and bacterial carriers of the Astrakhan region as the basis for the selection of bacteriophage producing strains for further combined phage therapy

Staphylococcus aureus has a high level of antibiotic resistance and is a common cause of nosocomial infections, which primarily requires development of new therapeutic strategies.Aim of the study was to investigate the level and spectrum of antibiotic resistance of S. aureus isolates for further isolation of virulent bacteriophages.Material and methods. The study used samples of clinical material obtained on the basis of the City Clinical Hospital No. 3 named after S.M. Kirov (Astrakhan). Bacterial strains isolated from patients were identified on the basis of morphological, cultural, biochemical and molecular genetic characteristics. The determination of the resistance of the isolated cultures was carried out by the disco-diffusion method using standardized commercial discs with antibiotics, in accordance with the guidelines.Results. Evaluation of antibiotic resistance of Staphylococcus aureus isolated during the study of clinical material from patients and analysis of sensitivity level of isolated strains of S. aureus allow us to conclude that all S. aureus isolated from patients are resistant to at least one antibiotic, and most strains are characterized by multidrug resistance to antibiotics.Conclusions. The presence of multi-resistant strains indicates the need to search for new approaches in the treatment of staphylococcal infection and to develop effective means for combination therapy based on virulent staphylococcal bacteriophages.

Protein kinase PknB as a promising target for the development of antibacterial drugs toward Staphylococcus aureus

Antibiotic resistance is one of the biggest challenges in modern medicine. Uncontrolled use of antibiotics has led to the emergence of multidrug and extensively drug-resistant bacterial strains which are non-susceptible to almost all currently known antimicrobial drugs. Unfortunately, only a few novel antibacterial drugs have been developed in recent decades. Approximately 30% of the human population is colonized by Staphylococcus aureus. Unfortunately, the treatment of staphylococcal infections is complicated due to the ability of S. aureus to produce antibiotic-neutralizing enzymes. Today, methicillin-(MRSA) and vancomycin-resistant (VRSA) S. aureus strains are very widespread in the world and become serious medical and public problem. For example, in 2019, more than 1 million people died from infections caused by antibiotic-resistant S. aureus. Therefore, the search of novel antistaphylococcal agents with unexploited mechanisms of action is of urgent need. The serine/threonine protein kinase PknB is involved in a number of important signaling pathways of S. aureus, such as cell wall metabolism, antibiotic susceptibility, and virulence regulation. Taking into account that protein kinase PknB is a key component of the bacterial cell signaling network involved in a number of important biological processes, this enzyme can be considered as a promising molecular target for the search of novel inhibitors as antibacterial agents [7]. In this review we analyzed the current data on the structure, mechanisms of PknB activity regulation and functions, and also summarized the results of inhibitors search

Molecular Characteristics of Staphylococcus aureus Strains to Carry Panton-Valentine Leukocidin Genes Isolated from Hospitalized Patients in Tehran, Iran

Background: Staphylococcus aureus with concurrent resistance to antibacterial agents is emerging globally. This emergence might be due to the production of different virulence determinants, notably Panton-Valentine leukocidin (PVL). Objectives: This study aimed to investigate the genetic characteristics of PVL-positive S. aureus strains isolates from clinical samples. Methods: An epidemiological study was conducted on 65 S. aureus isolates carrying pvl genes. An antibiogram test by the disk diffusion and broth microdilution methods was conducted to assess antimicrobial resistance profiles. Results: All detected methicillin-resistant S. aureus (MRSA) isolates were confirmed by mecA polymerase chain reaction (PCR) assays. The PVL-positive isolates were characterized using multiplex PCR assay to detect staphylococcal cassette chromosome mec (SCCmec) and agr types. The PVL frequency was 19.5% and 17.6% in MRSA and methicillin-susceptible S. aureus (MSSA), respectively. Among the PVL-positive isolates, 66.2% and 33.8% were MRSA and MSSA, respectively. Multidrug resistance amounted to 84.6% of the isolates (MRSA: 61.5%, MSSA: 23.1%). Staphylococcal cassette chromosome mec III was dominated (55.8%; 24/43). The most commonly identified agr was type III (53.8%; 35/65). Resistance to vancomycin amounted to 12.3% of the isolates, and all belonged to agr type III and SCCmec type III. The frequency of inducible and constitutive clindamycin resistance among PVL-positive MRSA strains (12.3% and 26.1%) was higher than PVL-positive MSSA strains (7.7% and 15.4%). Most constitutive and inducible clindamycin resistance isolates belonged to agr type III (26.2% and 18.5%) and SCCmec type III (each 27.9%). In the present study, 32.3% of the isolates were confirmed as mupirocin resistant, and all were MRSA, 9 (42.9%) and 12 (57.1%) isolates of which exhibited high-level mupirocin resistant (HLMUPR) and low-level mupirocin resistant phenotypes. All HLMUPR MRSA isolates belonged to SCCmec III and recovered from wound samples. Conclusions: The emergence of vancomycin-resistant S. aureus strains among PVL-positive S. aureus strains in Iran is a serious alarm and seems to be becoming the greatest concern in the treatment of staphylococcal infections in the healthcare setting. The present study reinforces plausible direct transfers between community and nosocomial PVL-positive S. aureus types.

In vivo efficiency of the produced recombinant lysostaphin antimicrobial peptide in treatment of methicillin-resistant Staphylococcus aureus (MRSA) skin infection in a mouse model.

Staphylococcus simulans secretes an antimicrobial compound called lysostaphin, which has bactericidal properties. It destroys staphylococci through the hydrolysis of peptidoglycan in the cell wall. Therefore, this unique property indicates the high ability of lysostaphin in the treatment of staphylococcal infections and is considered as an anti-staphylococcal agent. Escherichia coli BL21 (DE3) competent cells were transformed with pET32a-lysostaphin clone and induced by isopropyl-β-D-thio-galactoside (IPTG). The recombinant protein was purified by affinity chromatography. Recombinant lysostaphin -A-based ointment was used for external wound healing in animal model. In vivo activity of ointment was evaluated by clinical evidences and cytological microscopic assessment. Our results showed the recombinant protein was produced exactly. The results of checkerboard tests showed MIC, MBC and antibacterial activity test an acute reduction of cell viability during the use of lysostaphin, and SEM results approved the intense wrecking effects of lysostaphin in combination on bacterial cells. Macroscopic findings and microscopic data showed that the recombinant lysostaphin ointment was effective on excisional wound healing. Our findings proved that the recombinant lysostaphin ointment was effective on wound healing due to Staphylococcus aureus infection.

Anti-staphylococcal and antibiotic-potentiating activities of botanicals from nine Cameroonian food plants towards multidrug-resistant phenotypes

Background: Staphylococcus aureus is a commensal and pathogenic bacterium responsible for both community and nosocomial infections, superficial or deep, and benign or lethal. Staphylococcus aureus is a commensal and pathogenic bacterium responsible for both community and nosocomial infections, superficial or deep, and benign or lethal. Because of its infectious potential and its ability to develop resistance to many antibiotics, staphylococcal infections remain the target of reinforced clinical surveillance. To contribute to the fight against resistant staphylococcal infections, the in vitro assessment of the anti-staphylococcal activity of methanol extracts (or botanicals) of nine food plants from Cameroon, Persea americana, Psidium guajava, Syzygium jambos, Vernonia amygdalina, Citrus sinensis, passiflora edulis, Carica papaya, Aframomum letestuanum, and Garcinia kola), as well as the effects of the association of some of these botanicals with antibiotics against resistant and multidrug-resistant staphylococci. Methods: The plant secondary metabolites were extracted by maceration in methanol; the microdilution method using the rapid para-Iodonitrotetrazolium chloride (INT) colorimetric method was applied to evaluate the antibacterial activities of the botanicals as well as the effects of combining these extracts with antibiotics. Results: The botanicals had a minimum inhibitory concentration (MIC) range of 64-2048 µg/mL on the 17 staphylococcal strains and isolates tested. Extracts from Aframomum letestuanum seeds and Psidium guajava leaves and bark had the broadest activity spectra, inhibiting the growth of 95% and 85% of the studied bacteria, respectively. In the presence of an efflux pump inhibitor, reserpine, methanol extracts from Syzygium jambos leaves, Psidium guajava bark and epicarp, and Afromomum letestuanum epicarp showed a considerable increase in their activity. Botanicals from the leaves of Syzygium jambos improved the activities of tetracycline, ceftriaxone, chloramphenicol, and ampicillin against more than 80% of the tested bacteria. Conclusion: The investigated pants, mostly Psidium guajava, Syzygium jambos, and Aframomum letestuanum could be used in the treatment of staphylococcal infections with multidrug-resistant phenotypes.

Identification of Quinolones/Fluoroquinolones Resistance Genes from Staphylococci Strains Isolated at the University Hospital of Brazzaville, Republic of the Congo

Staphylococci strains, like the majority of bacterial strains, have developed the resistance to several antibiotics, including Quinolones and Fluoroquin-olones In the Republic of the Congo, cases of resistance leading to treat-ment failures have been observed during the treatment of staphylococcal infections with antibiotics in hospitals. The objective of this study was to identify the Quinolone/Fluoroquinolone resistance genes from staphylo-cocci strains isolated in hospitals. A total of 51 strains of Staphylococci were isolated, including 16 (31.37%) community strains, and 35 (68.62%) clinical strains. 46 strains of Staphylococcus aureus (S. aureus) and 5 SCNs were identified. A total of 34 DNA fragments from different strains resistant to Quinolones/Fluoroquinolones, including 21 (61.67%) DNA fragments from clinical S. aureus and 13 (38.23%) from community SCN strains were analyzed by the molecular method (genotypic detection) by PCR. The genotypic results made it possible to identify the gyrA, grLA and norA genes and to show that these genes are involved in the resistance of the strains to the various antibiotics used. The grLA gene was the most identified gene with a frequency of 75%. The gyrA and grLA genes have been identified in Staphylococcus aureus and Coagulase Negative Staphy-lococci. The norA gene, on the other hand, has only been identified in Staphylococcus aureus. Two mechanisms are essentially involved in the resistance of Staphylococci to quinolones/Fluoroquinolones, the mecha-nism of resistance by efflux, which takes place thanks to a transmembrane protein coded by the norA gene and by point mutations (substitution and deletion of acids or nucleotides) observed within the protein and nucleic sequences of the chromosomal gyrA and grLA genes.

SmdA is a Novel Cell Morphology Determinant in Staphylococcus aureus.

ABSTRACTCell division and cell wall synthesis in staphylococci need to be precisely coordinated and controlled to allow the cell to multiply while maintaining its nearly spherical shape. The mechanisms ensuring correct placement of the division plane and synthesis of new cell wall have been studied intensively. However, hitherto unknown factors and proteins are likely to play key roles in this complex interplay. Here, we identified and investigated a protein with a major influence on cell morphology in Staphylococcus aureus. The protein, named SmdA (for staphylococcal morphology determinant A), is a membrane protein with septum-enriched localization. By CRISPRi knockdown and overexpression combined with different microscopy techniques, we demonstrated that proper levels of SmdA were necessary for cell division, including septum formation and cell splitting. We also identified conserved residues in SmdA that were critical for its functionality. Pulldown and bacterial two-hybrid interaction experiments showed that SmdA interacted with several known cell division and cell wall synthesis proteins, including penicillin-binding proteins (PBPs) and EzrA. Notably, SmdA also affected susceptibility to cell wall targeting antibiotics, particularly in methicillin-resistant S. aureus (MRSA). Together, our results showed that S. aureus was dependent on balanced amounts of membrane attached SmdA to carry out proper cell division.

Synergistic effect of antibiotic combinations on Staphylococcus aureus biofilms and their persister cell populations

Treatment of staphylococcal infections is difficult due to multidrug resistance with their persister forms posing an added threat of recalcitrant infections. Antibiotic combinations are widely studied as an alternative strategy to combat them; therefore, they merit further investigation into their effect on the number of persister cells. In the present study, the fractional inhibitory concentrations of antibiotic combinations ciprofloxacin-daptomycin, ciprofloxacin-vancomycin, daptomycin-tobramycin, and tobramycin-vancomycin (checkerboard assay) were determined against two previously studied clinical (S48 and J6) and one standard (NCIM 5021) isolate of Staphylococcus aureus. They showed synergistic effects with a 2 to 256-fold reduction in MICs. All combinations also resulted in inhibition and disruption of biofilms in a concentration-dependent manner. All antibiotic combinations, except ciprofloxacin-daptomycin, showed total biofilm inhibition at 100X MICs. Similarly, antibiotic combination at 100X MIC showed 77–97% disruption of preformed biofilms. Time-kill assays performed at a 100X MIC combination against stationary-phase cells showed a two to six log10 reduction in CFU followed by a plateau indicating the presence of persisters. Significant differences were observed in persister cell fraction remaining after treatment with antibiotic combinations compared to monotherapies (p < 0.05) and therefore merit further investigation in clinical use for treatment against persisters.

ISOLYQUIRITIGENIN AFFECTS PHAGOCYTES FUNCTIONS AND INCREASES MICE SURVIVAL RATE IN STAPHYLOCOCCAL INFECTION

The results of studying the effect of isoliquiritigenin on animal survival in the model of staphylococcal infection and the function of human and animal phagocytes are presented in this article.The aim of the investigation was to study the effect of an isoliquiritigenin preliminary administration on the survival of animals against the background of staphylococcal infection, as well as on the function of phagocytes in mice and humans.Materials and methods. To assess the survival of Balb/C mice, a model of infection caused by Staphylococcus aureus J49 ATCC 25923 with the construction of Kaplan-Meier curves, was used. The effect on the phagocytes functions was studied by assessing the peptone-induced migration of phagocytes into the abdominal cavity of Balb/C mice, the absorption activity of phagocytes (neutrophils and monocytes) of human blood, as well as their production of reactive oxygen intermediates (ROIs) using а flow cytometry.Results. It was found out that a preliminary triple intraperitoneal administration of isoliquiritigenin (30 mg/kg) increases the survival rate of Balb/C mice in staphylococcal infection caused by Staphylococcus aureus J49 ATCC 25923. At the same time, isoliquiritigenin dose-dependently activates the production of reactive oxygen intermediates by human neutrophils and monocytes without statistically significantly suppressing a phagocytic activity of monocytes and neutrophils against fluoresceinisothiocyanate-labeled S. aureus J 49 ATCC 25923, as well as peptone-induced migration of phagocytes into the abdominal cavity of mice.Conclusion. Thus, a preliminary administration of isoliquiritigenin increases the survival rate of mice with staphylococcal infection and increases the production of reactive oxygen intermediates by phagocytes. The data obtained, can become the basis for further research of antibacterial and immunotropic effects of isoliquiritigenin in order to find new drugs for the treatment of staphylococcal infection.

Anthraquinone Derivatives and its Antibacterial Properties from Paederia foetida Stems

Background: Paederia foetida (Rubiaceae) locally known as Chinese fever vine is a prominent plant species in the east and south Asia. The extract of Paederia foetida Linn. has been used for the treatment of gastric infections or other digestive disorders in Chinese traditional medicine. Objective: The main aim of the study was to isolate bioactive constituents of P. foetida stem through a bio-guided assay, then evaluate their antibacterial activity and compare them with standard agents. Materials and Methods: The stems of P. foetida were extracted by methanol and successively partitioned with ethyl acetate and n-butanol. The ethyl acetate layer further fractionated using column chromatography and normal phase HPLC. The chemical structures of the isolated compounds were elucidated through comparison of the 1H and 13C NMR and MS spectral data with the literature. The antibacterial activity of P. foetida stem was evaluated using agar well diffusion assay and resazurin based micro-dilution technique. Results: Ten compounds were isolated from the Chinese fever vine stem including four anthraquinones, morindaparvin A (1), 1,3-dihydroxy-2-methoxyanthraquinone (2), digiferrol (3), and alizarin (4); two steroids, β-sitosterol (5), and stigmastan-3-one (6); two coumarins, scopoletin (7) and fraxidin (8) and two aromatics, ferulic acid (9) and vanillic acid (10). The four anthraquinones 1-4 were isolated for the first time from Chinese fever vine stem. Compound 2 and 3 significantly inhibited Staphylococcus aureus with MIC values 18.75 and 9.37 μg/mL respectively, and streptomycin (1.8 μg/mL) was used as a positive control. Conclusion: Compound 2 and 3 can be considered as a prospective candidate for the treatment of staphylococcal bacterial infections in both human and animals.

Emergence of resistance to last-resort antibiotics in clinical isolates of staphylococci with special reference to daptomycin and linezolid

Background: Treatment of staphylococcal infections has been complicated by the continuous emergence of antibiotic-resistant strains. Objective: In this study, we investigated the resistance pattern of clinical isolates of both coagulase-positive and coagulase-negative staphylococci to antibiotics recently introduced to treat staphylococcal infections. Methodology: Minimum inhibitory concentrations of antibiotics were determined by agar dilution or broth microdilution method. Identification of daptomycin- and linezolid-resistant isolates was performed by matrixassisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Moreover, the mechanism of resistance to daptomycin and linezolid was investigated on the molecular basis using PCR and amplicon sequencing. Results: Out of 104 staphylococci, 9 were resistant to ciprofloxacin (8.7%), 68 to clindamycin (65.4%), 2 to daptomycin (1.9%), 54 to erythromycin (51.9%), 6 to linezolid (5.8%), 3 to nitrofurantoin (2.9%), 75 to oxacillin (72.1%), 37 to teichoplanin (35.6%), 69 to tetracycline (66.3%), 51 to tigecycline (49%), and 41 to vancomycin (39.4%). Identification of daptomycin- and linezolid-resistant isolates revealed that they belong to Staphylococcus aureus, S. hominis, S. capitis, and S. epidermidis. In addition, sequencing of the mprF gene conferring daptomycin resistance revealed L431F and S829L point mutations in the two resistant isolates identified as S. aureus and S. hominis, respectively. Furthermore, linezolid resistance was due to optrA gene in two, and cfr in three of the resistant isolates. Conclusion: Resistance to the last-resort antibiotics used to treat staphylococcal infection has emerged. Therefore, the use of daptomycin and linezolid should be restricted to critical cases not susceptible to other available agents.

The current view on betalactam resistance in Staphylococcus aureus

The review presents the current view on the different resistance mechanisms of Staphylococcus aureus to beta-lactams, which are ones of the main antibiotics of choice for the treatment of staphylococcal infections. Currently, there are several mechanisms of resistance such as production of staphylococcal beta-lactamase (blaZ), which provides resistance to penicillins and aminopenicillins. Another one is the presence of an alternative penicillin-binding protein (PBP2a), which is the main marker of methicillinresistant S. aureus (MRSA), virtually providing resistance to all beta-lactams, with the exception of antiMRSA cephalosporins. Mutations in PBP2a contribute to the resistance to ceftaroline and ceftobiprol. Among the MRSA there are few exceptions with regards to the phenotypes called oxacillin-sensitive MRSA (OS-MRSA) which are susceptible to oxacillin despite the presence of the mecA encoding PBP2a. In addition, there are mec-independent pathways of beta-lactam resistance that could be found in S. aureus. In particular, mutations in the gdpP are associated with an increase in the intracellular concentration of c-diAMP messengers that promote resistance to beta-lactams, including anti-MRSA cephalosporins. Mutations in PBP4 or its promoter also contribute to the resistance. The mechanism of resistance to beta-lactams in mec-negative S. aureus (borderline oxacillin-resistant S. aureus, BORSA) is associated with the mutations in PBP1, PBP2, PBP3, and PBP4 or the overexpression of staphylococcal beta-lactamase. This review describes those and other phenotypes, the features of resistance mechanisms, clinical significance, as well as the possibilities for phenotypic detection.

Bacteriophages against methicillin resistant Staphylococcus aureus strains

Staphylococcus aureus is one of the most common opportunistic pathogens that causes a variety of diseases, from minor skin infections to life-threatening sepsis, meningitis, pneumonia and a number of other diseases. Particular attention was paid to methicillin-resistant Staphylococcus aureus (MRSA) strains with multiple drug resistance. The purpose of this study is investigation of the sensitivity of clinical isolates of Staphylococcus aureus, including methicillin-resistant strains, to bacteriophage drugs and determination of possibility of using this agent for the treatment of staphylococcal infections. A number of classical and modern microbiological methods for the isolation and identification of Staphylococcus aureus: an indication of genes, responsible for antibiotic resistance (PCR analysis), determination of sensitivity to antibiotics (disc diffusion method) and bacteriophages (spot test, Gracia method, Appelman method) were used in the study. The susceptibility analysis of Staphylococcus aureus with presence and absence of mecA gene to the commercial bacteriophage product – “PYOFAG® BACTERIOPHAGE POLYVALENT” was performed. The results of the study showed that the total number of susceptible strains of bacteria was 95±0,2%. The use of investigational Bacteriophage drug for the treatment of furunculosis caused by MRSA has shown positive results. After one week of using the bacteriophage as monotherapy, the patient experienced regression of the clinical symptoms. For the period of use no adverse effects have been detected. Thus, the phage drugs using can become an important tool in the control of antibiotic-resistant strains, which cause a variety of infections in humans.

Phenotypic Detection of Inducible Clindamycin Resistance among Clinical Isolates of Staphylococcus aureus in Bharatpur Hospital

Background: Clindamycin is regarded as a reserve drug in the treatment of staphylococcal infections. Among few therapeutic alternatives available for treatment of erythromycin-resistant Staphylococcus aureus infections, clindamycin has several advantages but major limitation in its use is the development of resistance resulting in treatment failure. Routine clindamycin susceptibility test may fail to detect such inducible resistance which can be detected by Double disc diffusion test (D-test). The present study was undertaken to determine the incidence of inducible clindamycin resistance among clinical isolates of S. aureus in a tertiary care hospital in central Nepal. Methods: A cross-sectional study was carried out among the patients visiting Bharatpur Hospital from September to November 2019. A total of 1279 clinical samples were examined for the identification of S. aureus by standard microbiological procedures. Antibiotic susceptibility testing of the isolates was done by Kirby-Bauer disc diffusion method and all the erythromycin-resistant isolates were subjected to D-test for the phenotypic detection of inducible clindamycin resistance according to CLSI guidelines (2016). Results: S. aureus was recovered from 4.5% (58/1279) samples of which 35 isolates were Methicillin-Resistant Staphylococcus aureus (MRSA) and 23 were multi-drug resistant (MDR). Tetracycline was found to be the most effective antibiotic whereas erythromycin was the least effective. D-test revealed that 39.7% isolates showed iMLSB phenotype, 3.5% showed cMLSB phenotype and 56.8% showed MS phenotype. The percentage of inducible and constitutive resistance was seen higher amongst MRSA isolates compared to Methicillin-Sensitive Staphylococcus aureus (MSSA) isolates. Incidence of S. aureus was found higher among females and in the age group 20-30 years and in pus samples (p&lt;0.01). Conclusions: Routine testing of inducible clindamycin resistance is suggested among the clinical isolates of erythromycin-resistant Staphylococci to avoid treatment failure.&#x0D;

Should the Vancomycin Minimal Inhibitory Concentration be used as an Infant Critical Care Regular Criteria?

Vancomycin is the first-line antibiotic used for the treatment of staphylococcal infections. Because of its narrow therapeutic window and the pharmacokinetics variability, vancomycin trough serum concentration should be monitored. However, due to the increased cases of staphylococcus' commensal species infections and the case of vancomycin resistance, the minimal inhibitory concentration should be considered on antimicrobial therapy. This article aimed to show the importance of the minimal inhibitory concentration to infants on vancomycin therapy as regular criteria. Three infants in the use of vancomycin, hospitalized in the same maternity hospital, and that had at least one blood culture performed during the intensive-care-unit hospitalization were included in the study. Vancomycin serum concentrations were determined by particleenhanced- turbidimetric inhibition-immunoassay. The vancomycin minimal inhibitory concentration data were interpreted by following the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST). The trough serum concentration range of 10 to 20 mg.L-1 was considered therapeutic. All three patients had at least one infection by S. epidermidis, being one patient exhibit vancomycin- resistant S. epidermidis infection. All patients had stoppages in the vancomycin treatment, and the minimal inhibitory concentration was performed for only one patient. The data obtained from these patients also showed the need to perform therapeutic monitoring by using minimal inhibitory concentration values, because, although the serum concentrations were within the reference range, they are insufficient to guarantee patient therapeutic success.

From Substrate to Fragments to Inhibitor Active In Vivo against Staphylococcus aureus.

Antibiotic resistance is a worldwide threat due to the decreasing supply of new antimicrobials. Novel targets and innovative strategies are urgently needed to generate pathbreaking drug compounds. NAD kinase (NADK) is essential for growth in most bacteria, as it supports critical metabolic pathways. Here, we report the discovery of a new class of antibacterials that targets bacterial NADK. We generated a series of small synthetic adenine derivatives to screen those harboring promising substituents in order to guide efficient fragment linking. This led to NKI1, a new lead compound inhibiting NADK that showed in vitro bactericidal activity against Staphylococcus aureus. In a murine model of infection, NKI1 restricted survival of the bacteria, including methicillin-resistant S.aureus. Collectively, these findings identify bacterial NADK as a potential drug target and NKI1 as a lead compound in the treatment of staphylococcal infections.

Infections Due to Staphylococci

Staphylococci are nonsporulating, nonmotile, gram-positive cocci that have an average diameter of 1 µm. Microscopically, staphylococci tend to be larger and rounder than streptococci. Because cell division occurs on three planes, these organisms are typically found in grapelike clusters and tetrads, as well as in pairs and sometimes in short chains. Staphylococci are very hardy organisms and can withstand much more physical and chemical stress than pneumococci and streptococci. Because staphylococci are facultative anaerobes, they will grow in the presence or absence of oxygen. Staphylococci are catalase positive. Of the species of staphylococci, Staphylococcus aureus is by far the most important human pathogen. This review covers the epidemiology and pathogenesis of S. aureus, clinical infections associated with S. aureus, treatment of staphylococcal infections, and staphylococcal toxic shock syndrome. Clinically important coagulase-negative staphylococci such as S. epidermidis and S. saprophyticus are also discussed. Tables list antibiotic treatment for staphylococcal infections, clinical manifestations of staphylococcal toxic shock syndrome, and antibiotic treatment for staphylococcal toxic shock syndrome. This review contains 3 figures, 6 tables, and 54 references. Key words: Staphylococcus aureus; Staphylococcal infections; Coagulase-negative staphylococci; Skin and soft tissue infections; S. aureus bacteremia; MRSA; Methicillin-resistant S. aureus; Toxic shock syndrome

Pathogenicity Islands and Their Role in Staphylococcal Biology.

Pathogenicity islands are members of a vast collection of genomic islands that encode important virulence, antibiotic resistance and other accessory functions and have a critical role in bacterial gene transfer. Staphylococcus aureus is host to a large family of such islands, known as SaPIs, which encode super antigen and other virulence determinants, are mobilized by helper phages and transferred at extremely high frequencies. They benefit their host cells by interfering with phage predation and enhancing horizontal gene transfer. This chapter describes their life cycle, the bases of their phage interference mechanisms, their transfer system and their conversion to antibacterial agents for treatment ofstaphylococcal infections.

STAPHYLOCOCCUS AUREUS: PATHOGENICITY, ANTIMICROBIAL RESISTANCE AND CLINICAL IMPLICATIONS

Objective: To conduct a reflection about the pathogenicity, antimicrobial resistance, and clinical implications of the infections caused by Staphylococcus aureus . Method: Reflexive analysis, supported by theoretical references about the pathogenicity, antimicrobial resistance, and clinical implications of the staphylococcal infections. Results: The pathogenesis of S. aureus infections is complex and depends on the host characteristics, expression of virulence factors and ability to develop resistance to antimicrobials. Methicillin-resistant S. aureus (MRSA) is related to an advancement of healthcare- and community-acquired infections, being vancomycin the primary therapeutic option. Infections caused by S. aureus with reduced vancomycin susceptibility (hVISA/VISA) have been associated with treatment failures and increased mortality. Conclusion: With the evolution of S. aureus to MRSA, hVISA and VISA, the treatment of staphylococcal infections has become a major challenge for the medical clinic, and an adequate and early antibiotic therapy is essential for decreasing morbidity and mortality rates related to this microorganism.