Rotating Magnetic Field Increases β-Lactam Antibiotic Susceptibility of Methicillin-Resistant Staphylococcus aureus Strains

Methicillin-resistant strains of Staphylococcus aureus (MRSA) have developed resistance to most β-lactam antibiotics and have become a global health issue. In this work, we analyzed the impact of a rotating magnetic field (RMF) of well-defined and strictly controlled characteristics coupled with β-lactam antibiotics against a total of 28 methicillin-resistant and sensitive S. aureus strains. The results indicate that the application of RMF combined with β-lactam antibiotics correlated with favorable changes in growth inhibition zones or in minimal inhibitory concentrations of the antibiotics compared to controls unexposed to RMF. Fluorescence microscopy indicated a drop in the relative number of cells with intact cell walls after exposure to RMF. These findings were additionally supported by the use of SEM and TEM microscopy, which revealed morphological alterations of RMF-exposed cells manifested by change of shape, drop in cell wall density and cytoplasm condensation. The obtained results indicate that the originally limited impact of β-lactam antibiotics in MRSA is boosted by the disturbances caused by RMF in the bacterial cell walls. Taking into account the high clinical need for new therapeutic options, effective against MRSA, the data presented in this study have high developmental potential and could serve as a basis for new treatment options for MRSA infections.

The effect of red passion fruit (Passiflora edulis Sims.) fermentation time on its activity against Extended Strain Methicillin-Resistant (ESBL) Escherichia coli and Methicillin-Resistant Staphylococcus aureus (MRSA)

OBJECTIVES

The purpose of this study is to determine the effect of fermentation techniques on the inhibitory activity of red passion fruit (Passiflora edulis Sims.) fermentation filtrate in De Man Rogosa Sharpe-broth (MRS-B) media against Extended Strain Methicillin-Resistant (ESBL) Escherichia coli and Methicillin-Resistant Staphylococcus aureus (MRSA).

METHODS

The fruit pulp was wrapped in banana leaves before compared to direct fermentation processes. This study was divided into three treatment groups. Group 1 was the fruit pulp (5 g) fermented in 45 mL of MRS-B medium for 24 h. Group 2 was the fruit pulp wrapped in banana leaves for 3 days before fermented in MRS-B for 24 h. Group 3 was the fruit pulp wrapped in banana leaves for 3 days before fermentation in MRS-B for 48 h. Fermentation broth of each condition was taken and then filtered using millipore (0.2 µm). As many as 50 µL of filtrates was tested for its inhibitory activity against E. coli ESBL and MRSA using the Kirby Bauer method.

RESULTS

Group 2 showed the best antibacterial activity against E. coli ESBL and MRSA with the average zone of inhibition of 38.3 and 37.6 mm respectively. These values were higher than the first and group 3s activities.

CONCLUSIONS

The inhibitory activity of group 1s against ESBL and MRSA is categorized as a moderate potency with a diameter of growth inhibition zone of 16-20 mm, whereas the other groups are categorized as strong potency with a diameter higher than 20 mm.

Study on Demethoxycurcumin as a Promising Approach to Reverse Methicillin-Resistance of Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has always been a threatening pathogen. Research on phytochemical components that can replace antibiotics with limited efficacy may be an innovative method to solve intractable MRSA infections. The present study was devoted to investigate the antibacterial activity of the natural compound demethoxycurcumin (DMC) against MRSA and explore its possible mechanism for eliminating MRSA. The minimum inhibitory concentrations (MICs) of DMC against MRSA strains was determined by the broth microdilution method, and the results showed that the MIC of DMC was 62.5 μg/mL. The synergistic effects of DMC and antibiotics were investigated by the checkerboard method and the time–kill assay. The ATP synthase inhibitors were employed to block the metabolic ability of bacteria to explore their synergistic effect on the antibacterial ability of DMC. In addition, western blot analysis and qRT-PCR were performed to detect the proteins and genes related to drug resistance and S. aureus exotoxins. As results, DMC hindered the translation of penicillin-binding protein 2a (PBP2a) and staphylococcal enterotoxin and reduced the transcription of related genes. This study provides experimental evidences that DMC has the potential to be a candidate substance for the treatment of MRSA infections.

Staphylococcus aureus resistance to albocycline can be achieved by mutations that alter cellular NAD/PH pools

Small molecule target identification is a critical step in modern antibacterial drug discovery, particularly against multi-drug resistant pathogens. Albocycline (ALB) is a macrolactone natural product with potent activity against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) whose mechanism of action has been elusive to date. Herein, we report biochemical and genomic studies that reveal ALB does not target bacterial peptidoglycan biosynthesis or the ribosome; rather, it appears to modulate NADPH ratios and upregulate redox sensing in the cell consistent with previous studies at Upjohn. Owing to the complexity inherent in biological pathways, further genomic assays are needed to identify the true molecular target(s) of albocycline.

First Report on the Characteristics of Methicillin-Resistant Staphylococcus Capitis Isolates and an NRCS-A-clone Related Isolate Obtained from Iranian Children

BACKGROUND

Methicillin-resistant staphylococcus capitis (MRSC) NRCS-A clone (Multi- resistant and vancomycin-non susceptible) has been recently described as an emerging cause of nosocomial bacteremia, especially in neonatal intensive-care units (NICUs).

OBJECTIVE

The objective of this study was to evaluate the antibiotic and antiseptic resistance patterns, biofilm-producing ability and the prevalence of SCCmec and ACME types among MRSC isolates as well as to check the possible presence of NRCS-A clone at Tehran's Children's Medical Center, Iran.

METHODS

A total of 256 coagulase-negative Staphylococcal isolates were collected, of which 10 S. capitis isolates were obtained and tested for susceptibility against 13 antimicrobial and 3 antiseptic agents, as well as biofilm production. The presence of 15 distinct resistance genes, staphylococcal cassette chromosome mec (SCCmec), and arginine catabolic mobile elements (ACMEs) were tracked.

RESULTS

Seven out of 10 S. capitis isolates were MRSC (MIC90 van=8μg/mL) and resistant to trimethoprim/sulfamethoxazole, produced biofilm, (3 as strong biofilm producers) and carried ACME types I and II. Despite the identification of mec and ccr complexes in some isolates, all the SCCmec cassettes were untypeable (UT).

CONCLUSION

According to the studied features, only one isolate belonged to the NRSC-A clone. The results indicate that MRSC with high antibiotic resistance and unknown SCCmec might become a serious problem in the future for the treatment of patients, particularly children.

Prevalence of methicillin-resistant coagulase-negative staphylococci among Egyptian patients after surgical interventions

Coagulase-negative staphylococci (CoNS) are frequently isolated from wound infections. There are limited data examining the prevalence of methicillin-resistant CoNS (MRCoNS) among Egyptian patients after surgery. Thus, we studied 208 hospitalised patients, who had skin and soft tissue infections (SSTIs) due to various causes. Samples were cultured for isolation and identification of CoNS and isolates were screened for susceptibility against 23 different antimicrobials. Out of 241 Staphylococcal isolates, 114 (47.3%) were CoNS. The prevalence of MRCoNS among surgical site infection, diabetic foot, abscess, and burn patients was 13.4%, 11.5%, 15.6%, and 10.3%, respectively. The lowest resistance of the 27 identified MRCoNS isolates was to vancomycin, amikacin and gatifloxacin (7% each). We conclude that CoNS isolates are major pathogens associated with wound infections at our institution and MRCoNS probably poses a substantial threat for patients in Egypt, though most MRCoNS isolates demonstrated susceptibility to vancomycin.

Potential combinations of endocannabinoid/endocannabinoid-like compounds and antibiotics against methicillin-resistant Staphylococcus aureus

Infections caused by antibiotic-resistant strains of Staphylococcus aureus have reached epidemic proportions globally. Our previous study showed antimicrobial effects of anandamide (AEA) and arachidonoyl serine (AraS) against methicillin (MET)-resistant S. aureus (MRSA) strains, proposing the therapeutic potential of these endocannabinoid/endocannabinoid-like (EC/EC-like) agents for the treatment of MRSA. Here, we investigated the potential synergism of combinations of AEA and AraS with different types of antibiotics against MRSA grown under planktonic growth or biofilm formation. The most effective combinations under planktonic conditions were mixtures of AEA and ampicillin (AMP), and of AraS and gentamicin (GEN). The combination with the highest synergy in the biofilm formation against all tested bacterial strains was AEA and MET. Moreover, the combination of AraS and MET synergistically caused default of biofilm formation. Slime production of MRSA was also dramatically impaired by AEA or AraS combined with MET. Our data suggest the novel potential activity of combinations of EC/EC-like agents and antibiotics in the prevention of MRSA biofilm formation.

Staphylococcus epidermidis MSCRAMM SesJ Is Encoded in Composite Islands

Staphylococcus epidermidis is a leading cause of nosocomial infections in patients with a compromised immune system and/or an implanted medical device. Seventy to 90% of S. epidermidis clinical isolates are methicillin resistant and carry the mecA gene, present in a mobile genetic element (MGE) called the staphylococcal cassette chromosome mec (SCCmec) element. Along with the presence of antibiotic and heavy metal resistance genes, MGEs can also contain genes encoding secreted or cell wall-anchored virulence factors. In our earlier studies of S. epidermidis clinical isolates, we discovered S. epidermidis surface protein J (SesJ), a prototype of a recently discovered subfamily of the microbial surface component recognizing adhesive matrix molecule (MSCRAMM) group. MSCRAMMs are major virulence factors of pathogenic Gram-positive bacteria. Here, we report that the sesJ gene is always accompanied by two glycosyltransferase genes, gtfA and gtfB, and is present in two MGEs, called the arginine catabolic mobile element (ACME) and the staphylococcal cassette chromosome (SCC) element. The presence of the sesJ gene was associated with the left-hand direct repeat DR_B or DR_E. When inserted via DR_E, the sesJ gene was encoded in the SCC element. When inserted via DR_B, the sesJ gene was accompanied by the genes for the type 1 restriction modification system and was encoded in the ACME. Additionally, the SCC element and ACME carry different isoforms of the SesJ protein. To date, the genes encoding MSCRAMMs have been seen to be located in the bacterial core genome. Here, we report the presence of an MSCRAMM in an MGE in S. epidermidis clinical isolates.IMPORTANCES. epidermidis is an opportunistic bacterium that has established itself as a successful nosocomial pathogen. The modern era of novel therapeutics and medical devices has extended the longevity of human life, but at the same time, we also witness the evolution of pathogens to adapt to newly available niches in the host. Increasing antibiotic resistance among pathogens provides an example of such pathogen adaptation. With limited opportunities to modify the core genome, most of the adaptation occurs by acquiring new genes, such as virulence factors and antibiotic resistance determinants present in MGEs. In this study, we describe that the sesJ gene, encoding a recently discovered cell wall-anchored protein in S. epidermidis, is present in both ACME and the SCC element. The presence of virulence factors in MGEs can influence the virulence potential of a specific strain. Therefore, it is critical to study the virulence factors found in MGEs in emerging pathogenic bacteria or strains to understand the mechanisms used by these bacteria to cause infections.

Linezolid Resistance in Staphylococcus haemolyticus - Case Series and Review of Literature

BACKGROUND

Coagulase negative Staphylococci (CoNS) are important. The common antibiotics used for the treatment of the infections caused by CoNS are penicillin, oxacillin, ciprofloxacin, clindamycin, erythromycin, gentamicin, and vancomycin. Linezolid is an oxazolidinone group of antibiotic with activity against Gram-positive bacteria. It is used for the treatment of serious infections caused by Gram-positive bacteria resistant to other antibiotics, including streptococci, vancomycin-resistant enterococci (VRE).

AIMS AND OBJECTIVE

This study emphasizes on the judicious use of newer antibiotics to contain the spread of resistance.

METHOD

We are discussing five cases of Linezolid resistant Staphylococcus Haemolyticus which were reported in our laboratory during one year from patients with device related infections and also review of literature is being presented for an update.

RESULT

In our study, the isolates were resistant to other groups of antimicrobials but susceptible to glycopeptides. All the isolates were methicillin-resistant.

CONCLUSION

Linezolid is approved as an alternative drug to be given for catheter-related bloodstream infections. In earlier studies, linezolid-resistant staphylococci have been reported increasingly all over the world. This study is to create awareness amongst clinicians that improper and excessive use of linezolid will make this antibiotic-resistant and thus will be of no help in future, so judicious and relevant use of antibiotics needs to be emphasized.

Local Treatment of Local Staphylococcal Infection with Complex Preparations Based on Metal Nanoparticles in the Experiment

Antibacterial activity of powdered preparations based on copper and silver nanoparticles was compared with activity of the reference preparation Baneocin on the model of local staphylococcal infection in white rats. The developed preparations exhibited pronounced antibacterial activity against methicillin-resistant S. epidermidis strains in vivo significantly (p<0.001) exceeding that of Baneocin, reduced microbial contamination of the wound on day 5 of study by 2 lg and more in comparison with bacterial load before treatment, and provided effective decontamination of the wound within 7-10 days.

Photothermal inactivation of methicillin-resistant Staphylococcus aureus: anti-biofilm mediated by a polypyrrole-carbon nanocomposite

Widespread resistance to antibiotics amongst pathogens has become a tremendous challenge of high morbidity and mortality rates which increases the needs to exploring novel methods of treatment. An efficient antimicrobial procedure to root out pathogenic bacteria is photothermal therapy. In this study, antimicrobial effects of a polypyrrole-carbon nanocomposite (PPy-C) upon laser irradiation in order to destroy the pathogenic gram-positive bacterium, methicillin-resistant Staphylococcus aureus (MRSA) were assessed. The bacterial cells were incubated with 500, 750 and 1000 μg ml-1 concentrations of PPy-C and irradiated with an 808-nm laser at a power density of 1.0 W cm-2. To indicate the biocompatibility and toxic effect of the nanocomposite without and with laser irradiation, the authors counted the number of CFUs and compared it to an untreated sample. Antibacterial mechanisms of PPy-C were assessed through temperature increment, reactive oxygen species production, and protein and DNA leakages. Photothermal heating assay showed that 26°C temperature increases in the presence of 1000 µg ml-1 PPy-C led to >98% killing of MRSA. Furthermore, 20 min radiation of near-infrared light to PPy-C in different concentrations indicated destruction and reduction in the MRSA biofilm formation. Therefore, PPy-C was introduced as a photothermal absorber with a bactericidal effect in MRSA.

Susceptibility of microorganisms causing acute hand infections

Hand infections are a common presentation at the emergency departments. Without knowing the source of infection clinicians are dependent on systematic reports on the bacterial spectrum and susceptibility tests of the specific infection in their patient community. This study was based on a retrospective chart review of patients presenting to our outpatient clinic with acute hand infections. We documented patient demographics, the etiology, location, culture tests of the infection and analyzed if certain bacteria could be cultured significantly more often in certain etiologies or in specific sites of the hand infection. Susceptibility tests were added. Bacterial swabs of 204 patients were analyzed. Overall S. aureus was found in 53% of all cases, in only one case revealed methicillin-resistant S. aureus (MRSA). There was no significant difference in the bacterial spectrum according to the etiology of the hand infections, except for animal bites where Pasteurella multocida was the dominating bacteria in 63% of all cases. Amoxicillin-clavulanic acid, fluoroquinolones, and piperacillin were effective against the main bacteria. Our study confirms the previously published antibiotic resistance reports and reinforces the current antibiotic treatment guidelines also in this western European population.

Nationwide Organism Susceptibility Patterns to Common Preoperative Prophylactic Antibiotics: What Are We Covering?

BACKGROUND

Many periprosthetic joint infections (PJIs) are caused by organisms not susceptible to first-generation cephalosporins. We sought to evaluate the national susceptibility patterns of organisms to cefazolin and, or oxacillin, clindamycin, and vancomycin using antibiogram data.

METHODS

Publically available regional and state antibiograms were evaluated for antibiotic susceptibility patterns to commonly infecting gram-positive organisms. The number of isolates tested in each antibiogram and percent of strains susceptible to oxacillin, clindamycin, and vancomycin were recorded. Oxacillin is used as a surrogate to cefazolin in antibiograms. A comparison of antibiotic susceptibilities was performed.

RESULTS

Seven state and 38 regional antibiograms were reviewed. Oxacillin was a sensitive antibiotic in 99.2 ± 4.8% of methicillin-sensitive Staphylococcus aureus (MSSA) isolates, 0 ± 0% of methicillin-resistant Staphylococcus aureus (MRSA) isolates, 44.5 ± 13.7% of coagulase-negative staphylococcus organism isolates (CNS), and 30.6 ± 10.5% of Staphylococcus epidermidis isolates. Clindamycin was a sensitive antibiotic in 75.8 ± 8.4% of MSSA isolates, 60.2 ± 13.2% of MRSA isolates, 60.3 ± 11.4% of CNS isolates, and 56.2 ± 6.5% of S epidermidis isolates. Vancomycin was a sensitive antibiotic in 99.9 ± 0.4% of MSSA isolates, 99.8 ± 0.4% of MRSA isolates, 99.8 ± 0.5% of CNS isolates, and 99.6 ± 0.7% of S epidermidis isolates. Clindamycin was significantly less sensitive in MSSA isolates as compared with oxacillin and vancomycin (P < .0001). Oxacillin was significantly less sensitive in CNS, S epidermidis, and MRSA isolates as compared with clindamycin and vancomycin (P < .0001).

CONCLUSION

The national clindamycin susceptibility pattern is limited to MSSA and may not have an optimal susceptibility profile suitable for use as a prophylactic antibiotic. Cefazolin continues to have excellent coverage against MSSA.

A Small-Molecule Inhibitor of trans-Translation Synergistically Interacts with Cathelicidin Antimicrobial Peptides To Impair Survival of Staphylococcus aureus

Staphylococcus aureus is a leading cause of infection in the United States, and due to the rapid development of resistance, new antibiotics are constantly needed. trans-Translation is a particularly promising antibiotic target because it is conserved in many bacterial species, is critical for bacterial survival, and is unique among prokaryotes. We have investigated the potential of KKL-40, a small-molecule inhibitor of trans-translation, and find that it inhibits both methicillin-susceptible and methicillin-resistant strains of S. aureus KKL-40 is also effective against Gram-positive pathogens, including a vancomycin-resistant strain of Enterococcus faecalis, Bacillus subtilis, and Streptococcus pyogenes, although its performance with Gram-negative pathogens is mixed. KKL-40 synergistically interacts with the human antimicrobial peptide LL-37, a member of the cathelicidin family, to inhibit S. aureus but not other antibiotics tested, including daptomycin, kanamycin, or erythromycin. KKL-40 is not cytotoxic to HeLa cells at concentrations that are 100-fold higher than the effective MIC. We also find that S. aureus develops minimal resistance to KKL-40 even after multiday passage at sublethal concentrations. Therefore, trans-translation inhibitors could be a particularly promising drug target against S. aureus, not only because of their ability to inhibit bacterial growth but also because of their potential to simultaneously render S. aureus more susceptible to host antimicrobial peptides.

Efficacy of Azadirachta indica organic extracts against clinical methicillin resistant Staphylococcus aureus isolates

In current study we investigated the efficacy of organic extracts of Azadirachta indica leaves against Methicillin Resistant Staphylococcus aureus (MRSA) clinical isolates. For this purpose fresh leaves were used to prepare ethanol, methanol and chloroform extract. Secondly, a cross sectional study was conducted to isolate MRSA in clinical samples from patients having surgical/ non-surgical wounds from Allied Hospital and District Head Quarter Hospital, Faisalabad. The S. aureus isolates were initially identified by biochemical characterization, followed by identification of MRSA using cefoxitin disc diffusion test that was finally confirmed by genomic amplification of mecA gene, responsible for resistance. All MRSA isolates were tested to find vancomycin resistant S. aureus (VRSA) using E-strips (M.I.C. Evaluator^TM, Oxide, UK). The data showed an overall 37% prevalence of S. aureus including 56.75% clinical MRSA isolates while none of the isolated S. aureus showed resistance to vancomycin. The antimicrobial activity was measured as mean zone of inhibition for each extract against all MRSA isolates and it was found as 15.38±2.26, 16.09±3.09 and 17.42±2.48 for methanol, ethanol and chloroform extracts respectively. Chloroform extract showed significantly high antimicrobial activity against MRSA isolates. Altogether, the current study exposed the high prevalence of MRSA isolates from tertiary care hospitals. However, all MRSA isolates were found susceptible to organic extracts of A. indica leaves.

Bacteria isolated from companion animals in Japan (2014-2016) by blood culture

We aimed to identify microorganisms isolated by blood culture (BC) from companion animals and to determine antimicrobial resistance of these isolates during 2014-2016 at veterinary laboratory, in comparison with those during 2010-2013, in Japan. Clinical data (animal species, visiting animals/hospitalized animals, and others except for disease type and clinical course including history of antimicrobial agent use) on ill animals at veterinary clinics or hospitals were obtained. We retrospectively analyzed animal-origin BC results extracted from the database in 2014-2016 and those obtained in 2010-2013. BC-positive samples were from most of dogs (n = 174 in 2014-2016 and n = 86 in 2010-2013). Escherichia coli (n = 50, 25.1%) and Staphylococcus intermedius group (SIG) bacteria (n = 23, 11.6%) were most prevalent in 2014-2016, while the percentages of E. coli (n = 22, 25.3%) and SIG (n = 9, 10.3%) in 2010-2013 were similar to those in 2014-2016. Percentages of extended-spectrum β-lactamase (ESBL)-producing E. coli and methicillin-resistant staphylococci (MRS) rate of SIG bacteria isolated in 2014-2016 were 28.0% and 69.6% (vs. 22.7% and 44.4% in 2010-2013), respectively. Fourteen ESBL-producing E. coli in 2014-2016 were isolated from 7 visiting animals and 7 hospitalized ones, whereas the sixteen MRS of SIG were from 7 visiting animals and 9 hospitalized ones. Our observations support the prevalent microorganisms isolated by BC and their antimicrobial resistance patterns for two study periods.

Genomics-Driven Discovery of Chlorinated Cyclic Hexapeptides Ulleungmycins A and B from a Streptomyces Species

Analysis of the genome sequence of Streptomyces sp. KCB13F003 showed the presence of a cryptic gene cluster encoding flavin-dependent halogenase and nonribosomal peptide synthetase. Pleiotropic approaches using multiple culture media followed by LC-MS-guided isolation and spectroscopic analysis enabled the identification of two new chlorinated cyclic hexapeptides, ulleungmycins A and B (1 and 2). Their structures, including absolute configurations, were determined by 1D and 2D NMR techniques, advanced Marfey's analysis, and GITC derivatization. The new peptides, featuring unusual amino acids 5-chloro-l-tryptophan and d-homoleucine, exhibited moderate antibacterial activities against Gram-positive pathogenic bacteria including methicillin-resistant and quinolone-resistant Staphylococcus aureus.

Nasal and pharyngeal carriage of methicillin-resistant Staphylococcus sciuri among hospitalised patients and healthcare workers in a Serbian university hospital

There has been a paucity of data on methicillin-resistant Staphylococcus sciuri (MRSS) epidemiology in European healthcare settings. The aim of the study was to determine the prevalence of nasal and pharyngeal carriage and diversity of MRSS among inpatients and healthcare workers (HCWs) in the largest healthcare centre in Serbia, and to assess performance of different methods for MRSS screening. Nasal and pharyngeal swabs were obtained from 195 patients and 105 HCWs in different departments. Each swab was inoculated directly onto MRSA-ID, oxacillin-resistance screening agar and mannitol salt agar (MSA) with 2 mg/L of oxacillin. After inoculation, each swab was dipped in Mueller-Hinton broth with 6.5% NaCl and after overnight incubation, subcultured onto oxacillin-MSA. Characterisation of isolated MRSS strains was determined by antimicrobial susceptibility testing, PFGE, SCCmec typing and antimicrobial resistance genes detection. MRSS nasal and pharyngeal carriage rate was high (5%) in our hospital and department-variable. PFGE revealed a possible cross-transmission of MRSS between a patient and an HCW, and dissemination across hospital wards. All analysed isolates were multidrug resistant. Fusidic acid resistance was discovered in 93.7% of isolates, but fusA mutations in EF-G and fusB/C genes were not detected. SCCmec regions of MRSS contained elements of classic methicillin-resistant S. aureus type III. Broth enrichment prior to isolation on oxacillin-MSA was superior to direct cultivation on different media with a sensitivity/specificity of 100% and 88.5%, respectively. MRSS is a significant coloniser of patients and HCWs in the hospital. Further research is needed to investigate the clinical significance of the bacterium in our settings.

[Successful Treatment of Ascending Aortic Graft Infection with a Rifampicin-soaked Vascular Prosthesis and Continuous Irrigation]

A 68-year-old woman underwent replacement of the ascending aorta for acute type A aortic dissection. She was then diagnosed with postoperative methicillin-resistant Staphylococcus aureus (MRSA) infection, and the infected aortic graft was replaced with a rifampicin-soaked vascular prosthesis, which was followed by continuous irrigation using a 0.1% povidone-iodine solution. The postoperative course was uneventful, and she has been doing well for 5 years with no recurrence of infection. Prosthetic graft replacement using a rifampicin-soaked graft followed by continuous irrigation with povidone-iodine is useful for treatment of an MRSA-infected prosthetic vascular graft.

Infectious Diseases: Pharmacologic Treatment Options for Nosocomial Pneumonia Involving Methicillin-Resistant Staphylococcus aureus

Objective:

To discuss current and potential treatment options for nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA).

Data Sources:

A MEDLINE search (1966–January 2007) was conducted to identify English-language literature on pharmacotherapy of nosocomial pneumonia and the bibliographies of pertinent articles. Programs and abstracts from infectious disease meetings were also searched. Search terms included MRSA, nosocomial pneumonia, pulmonary infections, vancomycin, quinupristin/dalfopristin, linezolid, daptomycin, tigecycline, dalbavancin, oritavancin, and ceftobiprole.

Data Selection and Data Extraction:

All articles were critically evaluated and all pertinent information was included in this review.

Data Synthesis:

Vancomycin has been the drug of choice for MRSA infections for many years. Recent data suggest that linezolid may be superior to vancomycin in the treatment of MRSA nosocomial pneumonia. However, there are limitations to the available data. Therefore, prospective, randomized studies are needed before linezolid is recommended as the preferred first-line therapy. Other approved agents for nosocomial MRSA infections, such as quinupristin/dalfopristin and daptomycin, should not be used in the treatment of MRSA pneumonia, as they were inferior in clinical trials. Tigecycline has excellent activity against MRSA in vitro, but should not be routinely used for the treatment of MRSA pneumonia, as clinical data are lacking. In a Phase III clinical trial, an anti-MRSA cephalosporin, ceftobiprole, is being evaluated for effectiveness against nosocomial pneumonia. Investigational glycopeptides may eventually have a role in the treatment of nosocomial pneumonia, but data are currently lacking.

Conclusions:

Vancomycin is still the drug of choice for treatment of MRSA pneumonia, and linezolid should be used as an alternative agent. Linezolid should carry strong consideration for patients with vancomycin-induced nephrotoxicity or a documented lack of response to vancomycin. Tigecycline and investigational agents with activity against MRSA may be future options for nosocomial pneumonia due to MRSA.

Analysis of Empiric Antimicrobial Strategies for Cellulitis in the Era of Methicillin-Resistant Staphylococcus aureus

Background:

The rise in community-onset methicillin-resistant Staphylococcus aureus (MRSA) infections potentially complicates the empiric management of cellulitis. The threshold at which drugs active against MRSA, such as clindamycin and trimethoprim/sulfamethoxazole (TMP/SMX), should be incorporated into empiric therapy is unknown.

Objective:

To evaluate the cost-effectiveness of using cephalexin, TMP/SMX, or clindamycin for outpatient empiric therapy of cellulitis, given various likelihoods of infection due to MRSA.

Methods:

A decision analysis of the empiric treatment of cellulitis was performed from the perspective of a third-party payer. The model included initial therapy with cephalexin, clindamycin, or TMP/SMX, followed by treatment with linezolid in cases of clinical failure. Probability and cost estimates were obtained from clinical trials, epidemiologic data, and publicly available cost data and were subjected to sensitivity analysis.

Results:

Under the base-case scenario (37% probability of infection by S. aureus and a 27% MRSA prevalence), cephalexin was the most cost-effective option. Clindamycin became a more cost-effective therapy at MRSA probabilities from 41–80% when the probability of staphylococcal infection was greater than 40%. TMP/SMX was cost-effective only at very high likelihoods of MRSA infection. Variables with the most influence in the model were probability of S. aureus being methicillin-resistant, cost of linezolid, probability of a cure with cephalexin for a non-MRSA infection, and probability of infection due to S. aureus.

Conclusions:

Cephalexin remains a cost-effective therapy for outpatient management of cellulitis at current estimated MRSA levels. Cephalexin was the most cost-effective choice over most of the modeled range of probabilities, with clindamycin becoming more cost-effective at high likelihoods of MRSA infection. TMP/SMX is unlikely to be cost-effective for treatment of simple cellulitis. Further studies of the microbiology of cellulitis, the epidemiology of MRSA, and the clinical effectiveness of clindamycin and TMP/SMX in skin and soft tissue infections are needed.

Antibacterial Effects of Glycyrrhetinic Acid and Its Derivatives on Staphylococcus aureus

Staphylococcus aureus is a major pathogen in humans and causes serious problems due to antibiotic resistance. We investigated the antimicrobial effect of glycyrrhetinic acid (GRA) and its derivatives against 50 clinical S. aureus strains, including 18 methicillin-resistant strains. The minimum inhibitory concentrations (MICs) of GRA, dipotassium glycyrrhizate, disodium succinoyl glycyrrhetinate (GR-SU), stearyl glycyrrhetinate and glycyrrhetinyl stearate were evaluated against various S. aureus strains. Additionally, we investigated the bactericidal effects of GRA and GR-SU against two specific S. aureus strains. DNA microarray analysis was also performed to clarify the mechanism underlying the antibacterial activity of GR-SU. We detected the antimicrobial activities of five agents against S. aureus strains. GRA and GR-SU showed strong antibacterial activities compared to the other three agents tested. At a higher concentration (above 2x MIC), GRA and GR-SU showed bactericidal activity, whereas at a concentration of 1x MIC, they showed a bacteriostatic effect. Additionally, GRA and GR-SU exhibited a synergistic effect with gentamicin. The expression of a large number of genes (including transporters) and metabolic factors (carbohydrates and amino acids) was altered by the addition of GR-SU, suggesting that the inhibition of these metabolic processes may influence the degree of the requirement for carbohydrates or amino acids. In fact, the requirement for carbohydrates or amino acids was increased in the presence of either GRA or GR-SU. GRA and GR-SU exhibited strong antibacterial activity against several S. aureus strains, including MRSA. This activity may be partly due to the inhibition of several pathways involved in carbohydrate and amino acid metabolism.

Graft Infectivity of Rifampin and Silver-Bonded Polyester Grafts to MRSA Contamination

The purpose of this study was to evaluate the ability of vascular polyester grafts with antibacterial properties to resist colonization following surface contamination by methicillin-resistant Staphylococcus aureus(MRSA) in an experimental canine model or aortic graft infection. Twenty-four pathogen-free dogs underwent replacement of the infrarenal aorta with either a rifampin-soaked (30 mg/mL) or silver-impregnated (Ag-acetate) woven polyester graft. Following implantation, the external graft surface was inoculated with 2 mL of 107 colonyforming units/mL (CFU) of MRSA. Preoperative antibiotic prophylaxis consisted of a single intravenous dose of 500 mg of sodium cefazolin. Four grafts of each type were explanted at 3, 7, and 14 days after implantation. Quantitative cultures (CFU/specimen) of perigraft fluid (1 mL), graft material (1 cm segment), and adjacent aorta (1 cm segment) were performed. Differences between grafts are expressed as% mean log reduction in recoverable CFU compared to the inoculation solution concentration of 107 CFUs. At 3 days, explanted rifampinsoaked grafts exhibited no MRSA growth (4 of 4 grafts) and a =97% mean log reduction of MRSA CFUs from the adjacent aorta and perigraft fluid (PGF). At 3 days, all silver-bonded grafts exhibited signs of infection and a mean log CFU reduction of MRSA ranging from 68% (absolute range 101–103 recoverable CFU) for the graft, 79% (absolute range 101–103 recoverable CFU) for the aorta, and 86% (absolute range 101–104 recoverable CFU) for PGF. The 7-day rifampin group had an average log reduction in MRSA CFU of 72% (graft), 58% (PGF), 75% (aorta). Quantitative cultures of 14-day rifampin grafted demonstrated continued bacterial growth suppression with mean MRSA CFU log reductions of 82%, graft; 72%, PGF; 89%, aorta. Silver-bonded grafts demonstrated <50% mean CFU reduction in MRSA growth at 7 days (absolute range 105–107 recoverable CFU) and 14 days (absolute range 103–107 recoverable CFU). No animal died from sepsis or anastomotic hemorrhage. Neither rifampin nor silverbonded grafts demonstrated prolonged resistance to surface MRSA contamination. Rifampinsoaked polyester grafts exhibited a marked but transient resistance MRSA colonization likely the result of high antibiotic concentration in the perigraft tissue. While both types of grafts failed to eradicate the MRSA infection future research with silver-bonded grafts that have an additional antibiotic attached may have a place in the treatment of MRSA infection.

Mupirocin for Controlling Methicillin-ResistantStaphylococcus Aureus: Lessons From a Decade of Use at a University Hospital

Background:

From 1990 to 1995 at Hospital Universitario dementino Fraga Filho, patients colonized or infected with methicillin-resistantStaphylococcus aureus(MRSA) were treated with mupirocin to eliminate MRSA carriage. In 1995, 65% of MRSA patients at this hospital had mupirocin-resistant isolates. Starting in 1996, mupirocin use was restricted to patients colonized, but not infected, with MRSA.

Objectives:

To describe the use of mupirocin for controlling MRSA over a decade and to analyze the molecular epidemiology of mupirocin-resistant MRSA infections at this hospital.

Setting:

A 490-bed, tertiary-care university hospital.

Methods:

The incidence densities of patients with MRSA and acquisition of mupirocin by the hospital were calculated for the period 1992–2001.S. aureusisolates from 1999–2000 were analyzed by pulsed-field gel electrophoresis. Mupirocin-resistant MRSA isolates from 1994–1995 and 1999–2000 were analyzed forileS-2gene background polymorphisms.

Results:

The incidence density of MRSA patients increased slightly over time, whereas the purchase of mupirocin decreased dramatically. Mupirocin-resistant MRSA infections decreased from 65% in 1994–1995 to 15% in 1999–2000. The MRSA Brazilian clone, detected in 1992, was still highly prevalent. The sameileS-2 encoding plasmid found in 1994–1995 persisted in three identical MRSA isolates from 1999–2000 belonging to the Brazilian clone.

Conclusions:

After mupirocin use decreased, theileS-2 encoding plasmid persisted in only a few Brazilian clone isolates. Our data on mupirocin-resistant MRSA incidence and mupirocin use strongly suggested that restricted use was related to decreased rates of mupirocin resistance at our hospital. (Infect Control Hosp Epidemiol 2005;26:662-667)

Importance of Control Group Selection for Evaluating Antimicrobial Use as a Risk Factor for Methicillin-ResistantStaphylococcus AureusBacteremia

Objective:

We investigated the importance of control group selection during an evaluation of antimicrobial use as a risk factor for methicillin-resistantStaphylococcus aureus(MRSA) bacteremia at our institution.

Methods:

We performed a case-control study. A case was defined as any patient admitted between January 1997 and May 2001 who developed nosocomial MRSA bacteremia. We used two control groups; control group I consisted of patients with nosocomial methicillin-susceptibleS. aureus(MSSA) bacteremia and control group II included only patients without bacteremia. We matched control-patients to case-patients using age, gender, time at risk, and hospital ward. Data collected on all patients included demographics, comorbidities, antibiotic use, time at risk, length of stay, severity of illness, and outcome.

Results:

We evaluated 63 patients (21 in each group). The three groups were well matched regarding age, gender, underlying diseases, and severity of illness. Patients in the MRSA group were more likely to have received a fluoroquinolone and had a higher mean number of days of fluoroquinolone use than did patients in the MSSA group (P= .027 andP= .015, respectively). However, all measures of fluoroquinolone use were similar for case-patients and for control-patients who did not have nosocomial bloodstream infection.

Conclusions:

Control group selection is important in evaluating antimicrobial use as a risk factor for MRSA bacteremia. Using control-patients infected with MSSA, rather than uninfected control-patients, may overestimate the association between antimicrobial use and MRSA infection. (Infect Control Hosp Epidemiol 2005;26:634-637)

Laxitextines A and B, Cyathane Xylosides from the Tropical Fungus Laxitextum incrustatum

Bioassay-guided fractionation of the mycelial extract of a basidiomycete culture collected in Kenya led to the isolation of two new cyathane diterpenoids named laxitextines A (1) and B (2). The producer strain was characterized by detailed taxonomic studies based on rDNA using the 5.8S gene region, the internal transcribed spacer 2 (ITS2), and part of the large subunit that identified the fungus as Laxitextum incrustatum. The structures of 1 and 2 were elucidated by NMR spectroscopic and mass spectrometric analyses. Both compounds exhibited moderate activities against Gram-positive bacteria Bacillus subtilis (DSM 10), Staphylococcus aureus (DSM 346), and methicillin-resistant Staph. aureus (DSM 1182). The two compounds also showed variable antiproliferative activities against mouse fibroblast (L929) and selected human cell lines (breast cancer MCF-7, epidermoid carcinoma A431, and umbilical vein endothelial HUVEC). The IC50 values with respect to the MCF-7 cell line for compounds 1 and 2 were 2.3 and 2.0 μM, respectively.

Whole-Genome Sequencing of Methicillin-Resistant Staphylococcus aureus Resistant to Fifth-Generation Cephalosporins Reveals Potential Non-mecA Mechanisms of Resistance

Fifth-generation cephalosporins, ceftobiprole and ceftaroline, are promising drugs for treatment of bacterial infections from methicillin-resistant Staphylococcus aureus (MRSA). These antibiotics are able to bind native PBP2a, the penicillin-binding protein encoded by the mecA resistance determinant that mediates broad class resistance to nearly all other beta-lactam antibiotics, at clinically achievable concentrations. Mechanisms of resistance to ceftaroline based on mecA mutations have been previously described. Here we compare the genomes of 11 total parent-daughter strains of Staphylococcus aureus for which specific selection by serial passaging with ceftaroline or ceftobiprole was used to identify novel non-mecA mechanisms of resistance. All 5 ceftaroline-resistant strains, derived from 5 different parental strains, contained mutations directly upstream of the pbp4 gene (coding for the PBP4 protein), including four with the same thymidine insertion located 377 nucleotides upstream of the promoter site. In 4 of 5 independent ceftaroline-driven selections, we also isolated mutations to the same residue (Asn138) in PBP4. In addition, mutations in additional candidate genes such as ClpX endopeptidase, PP2C protein phosphatase and transcription terminator Rho, previously undescribed in the context of resistance to ceftaroline or ceftobiprole, were detected in multiple selections. These genomic findings suggest that non-mecA mechanisms, while yet to be encountered in the clinical setting, may also be important in mediating resistance to 5th-generation cephalosporins.

Synergistic, collaterally sensitive β-lactam combinations suppress resistance in MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most prevalent multidrug-resistant pathogens worldwide, exhibiting increasing resistance to the latest antibiotic therapies. Here we show that the triple β-lactam combination meropenem-piperacillin-tazobactam (ME/PI/TZ) acts synergistically and is bactericidal against MRSA subspecies N315 and 72 other clinical MRSA isolates in vitro and clears MRSA N315 infection in a mouse model. ME/PI/TZ suppresses evolution of resistance in MRSA via reciprocal collateral sensitivity of its constituents. We demonstrate that these activities also extend to other carbapenem-penicillin-β-lactamase inhibitor combinations. ME/PI/TZ circumvents the tight regulation of the mec and bla operons in MRSA, the basis for inducible resistance to β-lactam antibiotics. Furthermore, ME/PI/TZ subverts the function of penicillin-binding protein-2a (PBP2a) via allostery, which we propose as the mechanism for both synergy and collateral sensitivity. Showing in vivo activity similar to that of linezolid, ME/PI/TZ demonstrates that combinations of older β-lactam antibiotics could be effective against MRSA infections in humans.

In Vitro Activity of Epigallocatechin Gallate and Quercetin Alone and in Combination versus Clinical Isolates of Methicillin-Resistant Staphylococcus aureus

Topical infections can become life threatening in immunocompromised patients. However, fewer treatments are available as multi-drug-resistant bacteria become more common. The natural compounds epigallocatechin gallate (1) and quercetin (2) alone and in combination were tested as potential antimicrobial clinical therapies. Strong antimicrobial activity was produced by 1 alone against methicillin-resistant Staphylococcus aureus, and activity was significantly increased in the presence of 2. A synergistic interaction was observed between the two compounds. Kill kinetics indicate the combination is bactericidal over 24 h.

Synthesis and evaluation of novel pleuromutilin derivatives with a substituted pyrimidine moiety

A series of novel pleuromutilin derivatives possessing 6-hydroxy pyrimidine moieties were synthesized via acylation reactions under mild conditions. The in vitro antibacterial activities of the synthesized derivatives against methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), Bacillus subtilis (B. subtilis), and Escherichia coli (E. coli) were tested by the agar dilution method. The majority of the screened compounds displayed potent activities. Compounds 3 and 6a were found to be the most active antibacterial agents against MRSA and MRSE. Moreover, in the vivo experiment, compound 6a showed comparable antibacterial activity to that of tiamulin, with ED50 of 5.47 mg/kg body weight against MRSA.

Characteristics of SCCmec IV and V Methicillin-Resistant Staphylococcus aureus (MRSA) in Israel

BACKGROUND

Isolation of methicillin-resistant Staphylococcus aureus (MRSA) in healthy individuals is not common in Israel. In our hospital, about 30% of MRSA isolates were SCCmec types IV and V.

OBJECTIVES

To identify the demographic and clinical characteristics of patients carrying MRSA SCCmec type IV or V, and to compare them with each other and with those of patients with SCCmec types I-III.

METHODS

We conducted a case-control study that included 501 patients from whom MRSA was isolated: 254 with SCCmec type I, II, or III, and 243 isolates from SCCmec types IV or V.

RESULTS

MRSA was isolated from surveillance cultures in 75% of patients and from a clinical site in 25%. The majority of our study population was elderly, from nursing homes, and with extensive exposure to health care. First, we compared characteristics of patients identified through screening. Statistically significant predictors of SCCmec V vs. IV were Arab ethnicity (OR 7.44, 95% CI 1.5-37.9) and hospitalization in the year prior to study inclusion (OR 5.7, 95% CI 1.9-16.9). No differences were found between patients with SCCmec types I-III and patients with SCCmec type IV or V. Analysis of the subset of patients who had clinical cultures yielded similar results.

CONCLUSIONS

SCCmec types IV and V were common in the hospital setting although rare in the community. It seems that in Israel, SCCmec IV and V are predominantly health care-associated MRSA.

Economic features of antibiotic resistance: the case of methicillin-resistant Staphylococcus aureus

This paper analyses and updates the economic information regarding methicillin-resistant Staphylococcus aureus (MRSA), including information that has been previously reviewed by other authors, and new information, for the purpose of facilitating health management and clinical decisions. The analysed articles reveal great disparity in the economic burden on MRSA patients; this is mainly due to the diversity of the designs of the studies, as well as the variability of the patients and the differences in health care systems. Regarding prophylactic strategies, the studies do not provide conclusive results that could unambiguously orientate health management. The studies addressing treatments noted that linezolid seems to be a cost-effective treatment for MRSA, mostly because it is associated with a shorter length of stay (LOS) in hospital. However, important variables such as antimicrobial susceptibility, infection type and resistance emergence should be included in these analyses before a conclusion is reached regarding which treatment is the best (most efficient). The reviewed studies found that rapid MRSA detection, using molecular techniques, is an efficient technique to control MRSA. As a general conclusion, the management of MRSA infections implicates important economic costs for hospitals, as they result in higher direct costs and longer LOS than those related to methicillin-susceptible S. aureus (MSSA) patients or MRSA-free patients; there is wide variability in those increased costs, depending on different variables. Moreover, the research reveals a lack of studies on other related topics, such as the economic implications of changes in MRSA epidemiology (community patients and lineages associated with farm animals).

[Antibiotic Resistance of Coagulase-Negative Staphylococci Isolated at Hospitals of St. Petersburg and Moscow]

Antibiotic susceptibility of 119 coagulase-negative staphylococci isolated at hospitals of St. Petersburg and Moscow was investigated and estimated at the local laboratories as oxacillin resistant. The following species were identified: Staphylococcus epidermidis, S. haemolyticus, S. hominis, S.capitis, S. simulans, S. pettenkoferi, S. lentus, S. carnosus and S. warneri. The oxacillin resistance was confirmed in 79.8% of the isolates. The frequency of the associated resistance to non-beta-lactams was much higher in the oxacillin resistant isolates vs. the oxacillin susceptible ones. When the CLSI and EUCAST susceptibility criteria were used, 1-3% difference in the resistance levels was recorded. Among the oxacillin resistant isolates the frequency of resistance to gentamicin, ciprofloxacin, erythromycin, moxifloxacin, tetracycline and clindamycin equaled 90, 88, 88, 63, 43 and 26% respectively. Two linezolid resistant isolates of S. epidermidis with lower susceptibility to tedizolid were isolated. Eight isolates of S. epidermidis showed lower resistance to mupirocin. The MIC of ceftarolin for oxacillin resistant coagulase-negative staphylococci varied from 0.5 to 2.0 mcg/ml, while for the oxacillin susceptible ones it was lower than 0.25 mcg/ml. No resistance to tigecyclin and vancomycin was observed.

Two new terpenoids from the stems of Manihot esculenta

A new eremophilane sesquiterpene, sporogen AO-2 (1), and a new beyerane diterpene, thecacorin C (2), together with two known compounds, longifoamide-B (3) and methylcholestane-3β,5α,6β-triol (4), were isolated from the stems of Manihot esculenta. The structures of the two new compounds were determined by spectroscopic techniques (UV, IR, MS, 1D, and 2D NMR). Antimicrobial assay showed that compound 3 possessed modest inhibitory effects on Saphylococcus aureus and methicillin-resistant S.aureus, diameters of inhibition zones of which were 7.5 and 8.0 mm, respectively. Compound 4 possessed modest inhibitory effect on S. aureus, the diameter of inhibition zone of which was 6.8 mm.

Curcumin reverse methicillin resistance in Staphylococcus aureus

Curcumin, a natural polyphenolic flavonoid extracted from the rhizome of Curcuma longa L., was shown to possess superior potency to resensitize methicillin-resistant Staphylococcus aureus (MRSA) to antibiotics. Previous studies have shown the synergistic activity of curcumin with β-lactam and quinolone antibiotics. Further, to understand the anti-MRSA mechanism of curcumin, we investigated the potentiated effect of curcumin by its interaction in diverse conditions. The mechanism of anti-MRSA action of curcumin was analyzed by the viability assay in the presence of detergents, ATPase inhibitors and peptidoglycan (PGN) from S. aureus, and the PBP2a protein level was analyzed by western blotting. The morphological changes in the curcumin-treated MRSA strains were investigated by transmission electron microscopy (TEM). We analyzed increased susceptibility to MRSA isolates in the presence of curcumin. The optical densities at 600 nm (OD₆₀₀) of the suspensions treated with the combinations of curcumin with triton X-100 and Tris were reduced to 63% and 59%, respectively, compared to curcumin without treatment. N,N'-dicyclohexylcarbodiimide (DCCD) and sodium azide (NaN₃) were reduced to 94% and 55%, respectively. When peptidoglycan (PGN) from S. aureus was combined with curcumin, PGN (0–125 μg/mL) gradually blocked the antibacterial activity of curcumin (125 μg/mL); however, at a concentration of 125 µg/mL PGN, it did not completely block curcumin. Curcumin has a significant effect on the protein level of PBP2a. The TEM images of MRSA showed damage of the cell wall, disruption of the cytoplasmic contents, broken cell membrane and cell lysis after the treatment of curcumin. These data indicate a remarkable antibacterial effect of curcumin, with membrane permeability enhancers and ATPase inhibitors, and curcumin did not directly bind to PGN on the cell wall. Further, the antimicrobial action of curcumin involved in the PBP2a-mediated resistance mechanism was investigated.

Cyclic Hexapeptides from the Deep South China Sea-Derived Streptomyces scopuliridis SCSIO ZJ46 Active Against Pathogenic Gram-Positive Bacteria

Three new cyclohexapeptides, desotamides B-D (2-4), and the known desotamide (1) were isolated from marine microbe Streptomyces scopuliridis SCSIO ZJ46. The sequences and absolute configurations of 2-4 were elucidated on the basis of high-resolution spectroscopic data, Marfey's method, and chiral-phase HPLC data. Desotamide C (3) contains a unique N-formyl-kynurenine residue, whereas 4 lacks formylation at the same site. Compounds 1 and 2 displayed notable antibacterial activities against strains of Streptococcus pnuemoniae, Staphylococcus aureus, and methicillin-resistant Staphylococcus epidermidis (MRSE), and structure activity relationship studies revealed the indispensability of the Trp component for antibacterial activity within this new scaffold.

Vancomycin and piperacillin-tazobactam against methicillin-resistant Staphylococcus aureus and vancomycin-intermediate Staphylococcus aureus in an in vitro pharmacokinetic/pharmacodynamic model

PURPOSE

Synergy between β-lactams and vancomycin against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-intermediate Staphylococcus aureus (VISA) has been observed in vitro and in vivo. However, studies investigating piperacillin-tazobactam with vancomycin against MRSA and VISA are limited despite broad clinical use of these antibiotics in combination. This study evaluated vancomycin and piperacillin-tazobactam against MRSA and VISA by using an in vitro pharmacokinetic/pharmacodynamic model.

METHODS

Two clinical MRSA strains (M3425 and M494) and one VISA strain (Mu50) were tested in duplicate by using a 72-hour, 1-compartment pharmacokinetic/pharmacodynamic model with the following exposures: growth control, vancomycin only, piperacillin-tazobactam only, and vancomycin with piperacillin-tazobactam. Vancomycin 1 g every 12 hours (free trough concentration, 8.75 mg/L; Cmin, 17.5 mg/L) and piperacillin-tazobactam 13.5 g per 24 hours' continuous infusion (free steady-state concentration, 27 mg/L) were simulated. Time-kill curves were constructed, and reductions in log10 CFU/mL at all time points were compared between regimens tested.

FINDINGS

Vancomycin and piperacillin-tazobactam MICs for M494, M3425, and Mu50 were 1, 1, and 4 and 1.5, 32, and >256 mg/L, respectively. All isolates had an oxacillin MIC ≥ 4 mg/L. Against all 3 isolates, vancomycin with piperacillin-tazobactam achieved a significant reduction in inoculum at 72 hours compared with vancomycin alone (all, P ≤ 0.015). The superiority of vancomycin with piperacillin-tazobactam compared with vancomycin alone became detectable at 8 hours for M3425 (P < 0.001) and at 24 hours for M494 and Mu50 (both, P ≤ 0.008). Although vancomycin with piperacillin-tazobactam achieved enhanced antibacterial activity at 72 hours against M3425 compared with vancomycin alone, bacterial regrowth occurred. Reduced susceptibility to vancomycin at 72 hours for M3425 was confirmed by using population analysis profile/AUC analysis. At 72 hours, M3425 had a PAP/AUC ratio of 0.77 compared to 0.51 at baseline.

IMPLICATIONS

Vancomycin with piperacillin-tazobactam demonstrated enhanced antimicrobial activity against MRSA and VISA compared with vancomycin alone. These results further enhance existing data that support using vancomycin in combination with a β-lactam for invasive MRSA infections. Combination therapy with vancomycin and a β-lactam against MRSA warrants clinical consideration.

Synthesis and biological activities of novel pleuromutilin derivatives with a substituted thiadiazole moiety as potent drug-resistant bacteria inhibitors

A series of novel pleuromutilin derivatives possessing thiadiazole moieties were synthesized via acylation reactions under mild conditions. The in vitro antibacterial activities of the derivatives against methicillin-resistant Staphylococcus aureus, methicillin-resistant Staphylococcus epidermidis, Escherichia coli, and Streptococcus agalactiae were tested by the agar dilution method and Oxford cup assay. The majority of the tested compounds displayed moderate antibacterial activities. Importantly, the three compounds with amino or tertiary amine groups in their side chains, 11, 13b, and 15c, were the most active antibacterial agents. Docking experiments carried out on the peptidyl transferase center (PTC) of 23S rRNA proved that there is a reasonable direct correlation between the binding free energy (ΔGb, kcal/mol) and the antibacterial activity. Moreover, the pharmacokinetic profiles of 11 and 15c in rat were characterized by moderate clearance and oral bioavailability.

Polyphenolic Constituent Structures ofZanthoxylum piperitumFruit and the Antibacterial Effects of Its Polymeric Procyanidin on Methicillin-ResistantStaphylococcus aureus

Zanthoxylum piperitum (Rutaceae) is used as a spice and a natural medicine in Japan. Our study found that ZP-CT-A, a polymeric proanthocyanidin purified from the fruit of this species, noticeably decreased the minimum inhibitory concentrations of beta-lactam antibiotics for methicillin-resistant Staphylococcus aureus (MRSA). The structure of ZP-CT-A was characterized on the basis of (13)C NMR and size exclusion chromatographic data and the results of thiolytic degradation. A mechanistic study of the effects of ZP-CT-A indicated that it suppressed the activity of beta-lactamase and largely decreased the stability of the bacterial cell membrane of MRSA, as shown by a reduction in the tolerance of MRSA to low osmotic pressure and high ionic strength solutions.

Detection of methicillin-resistant Staphylococcus aureus directly by loop-mediated isothermal amplification and direct cefoxitin disk diffusion tests

We evaluated the utility of 2 methods for detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from signal-positive blood culture bottles: loop-mediated isothermal amplification (LAMP) assay, and direct cefoxitin disk diffusion (DCDD) test using a 30 μg cefoxitin disk. In parallel, standard microbiological identification and oxacillin susceptibility testing with MecA PCR was performed. Of 60 blood cultures positive for Gram-positive cocci in clusters, LAMP (via detection of the FemA and MecA genes) showed 100% sensitivity and specificity for identification of MRSA/MSSA. When coagulase-negative staphylococci were tested, sensitivity for detection of methicillin resistance was 91.7% and specificity was 100%. DCDD along with direct tube coagulase assay detected only 80.6% of MRSA/MSSA. LAMP showed higher diagnostic accuracy although DCDD was more cost-effective and did not require additional reagents or supplies.

A novel microfluidic wound model for testing antimicrobial agents against Staphylococcus pseudintermedius biofilms

BACKGROUND

Current methods for testing treatments for veterinary surgical site infections can successfully emulate elements of a chronic wound, but these are time consuming and costly, requiring specialized laboratory equipment and considerable space to house study animals. Microfluidic devices however, can be coated with collagen and maintained at basal body temperature, providing a more cost-effective and space-saving model of a chronic wound. Our study assesses the applicability of a new microfluidic model by testing the activity of DispersinB against biofilms of methicillin-resistant Staphylococcus pseudintermedius (MRSP); DispersinB has been shown to prevent biofilm growth of Staphylococcus epidermidis, another prominent wound colonizer.

RESULTS

We successfully developed a microfluidic model to examine the effects of antimicrobial therapy on biofilms formed by organisms associated with wound infections in companion animals (e.g. MRSP). Although, we were unable to recapitulate previous findings that DispersinB-Gentamycin is highly effective against Staphylococcal biofilms using this model, we were able to confirm its effect in a microtitre plate. Differences in the experimental conditions likely account for this result (e.g. strains tested, flow conditions, treatment time, etc.). In the microtitre plate assay, DispersinB inhibited biofilm growth after a 24 hour period; there was an inverse relationship between the concentration of DispersinB-Gentamycin and the amount of biofilm remaining following treatment. Collagen-coated microtitre plates showed a similar result, but this did not correlate as well; collagen, the most abundant protein in the body may help to retain the biomass of treated biofilms.

CONCLUSIONS

Our model may be useful in examining the effect of treatment on wound infections, although we acknowledge that in this model the test organisms may be more recalcitrant to antimicrobials than in other published systems. We contend that this may in fact better represent the conditions in vivo, where organisms associated with chronic wound infections are highly resistant to antimicrobials.

Prevention of surgical site infections

In the current era of pay-for-performance standards, the incidence of surgical site infections is increasingly becoming an institutional marker of quality assurance. Surgical site infections lead to increased morbidity and mortality in the surgical population and contribute to an already rising healthcare cost. As a result, the surgical community goes to great lengths to prevent this costly and occasionally lethal complication. Many practices are evidence based, however, many are not. In this article, the most commonly used preventive strategies in practice today and the evidence behind each are reviewed. In addition, an overview of the epidemiology, pathophysiology and microbiology of surgical site infections will be provided.

Management of healthcare-associated methicillin-resistantStaphylococcus aureus

Healthcare-associated methicillin-resistant Staphylococcus aureus is a major cause of nosocomial infections worldwide, with significant attributable morbidity and mortality in addition to pronounced healthcare costs. Treatment results with vancomycin--the current recommended antibiotic for serious methicillin-resistant S. aureus infections--have not been impressive. The recent availability of effective antimicrobial agents other than glycopeptides, such as linezolid and daptomycin, as well as the anticipated approval of newer agents with diverse mechanisms of action, has somewhat ameliorated the threat posed by this organism. However, these drugs are expensive, and there is still no overall satisfactory strategy for reducing the incidence of healthcare-associated methicillin-resistant S. aureus in endemic regions. Although early results with the Society for Healthcare Epidemiology of America guidelines give cause for cautious optimism, long-term experience is lacking, and it is likely that these guidelines will have to be adapted according to local conditions and resources before implementation. Trends to keep in mind when considering the problem of healthcare-associated methicillin-resistant S. aureus include the advent of community-associated methicillin-resistant S. aureus, and the propensity of S. aureus to evolve and acquire resistance determinants over time. This was last vividly demonstrated by the handful of vancomycin-resistant S. aureus isolated recently, which had acquired the vancomycin resistance gene from vancomycin-resistant enterococci.

[Methicillin-resistant Staphylococcus aureus (MRSA) isolation in breast abscesses in a Public Maternity]

Mastitis and breast abscess in lactating women are risk factors for early breastfeeding cessation. This pathology is included in the group of skin and soft tissue infections. A descriptive study was performed with an advanced outlook. As of January 2007 through December 2011 a total of 137 breast abscesses were treated in our institution. We analyzed incidence, parity, postpartum days, risk factors, microbiological isolation and the adequacy of initial antibiotic treatment. In that period we observed a steady and significant increase in breast abscesses. Incidence from 0.19 to 0.84% in lactating women 2007 vs. 2011 p = 0.0001 IC 95% (-0.009; 0.003), 70.6% of them primiparous and a mean interval from delivery to breast abscess of 41.9 ± 35.8 days. The most frequent risk factors were sore nipples and breast engorgement. Staphylococcus aureus was isolated in 82.3 to 95.0%. Methicillin resistance was higher than 60%. These strains were susceptible to erythromycin, clindamycin, gentamicin, rifampicin, ciprofloxacin and trimethoprim-sulfamethoxazol. All the cases were surgically drained; the initial empirical treatment was inadequate in 60% of them, 90% of patients could maintain breast feeding after the procedure.

IN CONCLUSION

these data emphasize the need to prevent risk factors associated to breast abscesses: sore nipples and breast engorgement. In order to determine the adequate antibiotic treatment, bacteriological studies are required at every collection because SAMR prevalence varies according to diverse populations and geographic location.

Effect of thioridazine on experimental cutaneous staphylococcal infections

BACKGROUND

Some non-antibiotic drugs, such as the phenothiazine antipsychotic agents, may have antimicrobial activity.

MATERIALS AND METHODS

We sought to determine the in vivo antimicrobial effects of the phenothiazine thioridazine in two mouse models of Staphylococcus aureus skin infection.

RESULTS

Thioridazine significantly suppressed dissemination from skin to spleen and kidney after inoculation of the skin surface. However, the drug did not affect infection parameters in the skin itself. Thioridazine did suppress the size of abscesses produced when the bacteria were injected intradermally. On the other hand, using the cutaneous abscess model we were not able to demonstrate synergistic activity between thioridazine and the β-lactam drug cefazolin against methicillin-resistant S. aureus, as previously demonstrated in vitro.

CONCLUSION

The phenothiazine drug thioridazine has in vivo antimicrobial activity against certain S. aureus skin infections, although the previously-demonstrated reversal of methicillin resistance by this agent may not be readily evident in vivo.

Cytotoxic and antibacterial marfuraquinocins from the deep South China Sea-derived Streptomyces niveus SCSIO 3406

Four new sesquiterpenoid naphthoquinones, marfuraquinocins A-D (1-4), and two new geranylated phenazines, phenaziterpenes A (5) and B (6), were isolated from the fermentation broth of Streptomyces niveus SCSIO 3406, which originated from a South China Sea sediment sample obtained from a depth of 3536 m. The structures of 1-6 were elucidated on the basis of extensive MS and one-dimensional and two-dimensional NMR spectroscopic analyses. In a panel of cytotoxicity and antibacterial assays, 1 and 3 were found to inhibit a NCI-H460 cancer cell line with IC50 values of 3.7 and 4.4 μM, respectively. Compounds 1, 3, and 4 exhibited antibacterial activities against Staphylococcus aureus ATCC 29213 with equivalent MIC values of 8.0 μg/mL; compounds 3 and 4 each showed antibacterial activity against methicillin-resistant Staphylococcus epidermidis (MRSE) shhs-E1 with MIC values of 8.0 μg/mL.

β-Lapachone activity in synergy with conventional antimicrobials against methicillin resistant Staphylococcus aureus strains

The aim of this study was to evaluate the antimicrobial activity of lapachol, α-lapachone, β-lapachone and six antimicrobials (ampicillin, amoxicillin/clavulanic acid, cefoxitin, gentamicin, ciprofloxacin and meropenem) against twelve strains of Staphylococcus aureus from which resistance phenotypes were previously determined by the disk diffusion method. Five S. aureus strains (LFBM 01, LFBM 26, LFBM 28, LFBM 31 and LFBM 33) showed resistance to all antimicrobial agents tested and were selected for the study of the interaction between β-lapachone and antimicrobial agents, busing checkerboard method. The criteria used to evaluate the synergistic activity were defined by the Fractional Inhibitory Concentration Index (FICI). Among the naphthoquinones, β-lapachone was the most effective against S. aureus strains. FICI values ranged from 0.07 to 0.5, suggesting a synergistic interaction against multidrug resistant S. aureus (MRSA) strains. An additive effect was observed with the combination β-lapachone/ciprofloxacin against the LFBM 33 strain. The combination of β-lapachone with cefoxitin showed no added benefit against LFBM 31 and LFBM 33 strains. This study demonstrated that, in general, β-lapachone combined with beta lactams antimicrobials, fluoroquinolones and carbapenems acts synergistically inhibiting MRSA strains.

Indolo[3,2-a]carbazoles from a deep-water sponge of the genus Asteropus

Two new indolo[3,2-a]carbazoles (1, 2) were isolated from a deep-water collection of a sponge of the genus Asteropus. The structures of 1 and 2 were determined through the analysis of spectroscopic data including mass spectrometry and 2D-NMR. Compound 1 showed minimum inhibitory concentrations of 25 μg/mL against the fungal pathogen Candida albicans and 50 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA). Compounds 1 and 2 showed no cytotoxicity against the PANC1 human pancreatic carcinoma and NCI/ADR-RES ovarian adenocarcinoma cell lines at our standard test concentration of 5 μg/mL.

Photodynamic inactivation of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus with Ru(II)-based type I/type II photosensitizers

BACKGROUND

The introduction of new disinfection and sterilization methods, such as antimicrobial photodynamic therapy, is urgently needed for the healthcare industry, in particular to address the pervasive problem of antibiotic resistance. This study evaluated the efficacy and the mechanisms of photodynamic antimicrobial chemotherapy (PACT), also known as photodynamic inactivation (PDI) of microorganisms, induced by novel Ru(II)-based photosensitizers against Staphylococcus aureus and methicillin-resistant S. aureus strains.

METHODS

The photodynamic antibacterial effects of a new class of Ru(II)-based photosensitizers (TLD1411 and TLD1433) were evaluated against a strain of S. aureus (ATCC 25923) and a methicillin-resistant strain of S. aureus (MRSA, ATCC 33592). Bacterial samples were dosed with a range of photosensitizer concentrations (0.3-12 μM) and exposed to 530 nm light (90J cm(-2)) in normoxic conditions (ambient atmosphere) and in hypoxic conditions (0.5% O2).

RESULTS

Both photosensitizers exerted photodynamic inactivation (PDI) of the microorganisms in normoxia, and this activity was observed in the nanomolar regime. TLD1411 and TLD1433 maintained this PDI potency under hypoxic conditions, with TLD1433 becoming even more active in the low-oxygen environment.

CONCLUSION

The observation of activity in hypoxia suggests that there exists an oxygen-independent, Type I photoprocess for this new class of compounds in addition to the typical Type II pathway mediated by singlet oxygen. The intrinsic positive charge of the Ru(II) metal combined with the oxygen independent activity demonstrated by this class of photosensitizers presents a new strategy for eradicating both gram-positive and gram-negative bacteria regardless of oxygenation level.