Emerging Options for Treatment of Invasive, Multidrug-ResistantStaphylococcus aureusInfections

In silico exploration of 4(α-l-rhamnosyloxy)-benzyl isothiocyanate: A promising phytochemical-based drug discovery approach for combating multi-drug resistant Staphylococcus aureus

Multidrug-resistant (MDR) Staphylococcus aureus infections significantly threaten global health. With rising resistance to current antibiotics and limited solutions, the urgent discovery of new, effective, and affordable antibacterials with low toxicity is imperative to combat diverse MDR S. aureus strains. Hence, in this study, we introduce an in silico phytochemical-based approach for discovering novel antibacterial agents, underscoring the potential of computational approaches in therapeutic discovery. Glucomoringin Isothiocyanate (GMG-ITC) from Moringa oleifera Lam. is one of the phytochemical compounds with several biological activities, including antimicrobial, anti-inflammatory, and antioxidant activities, and is also effective against S. aureus. This study focuses on screening GMG-ITC as a potential drug candidate to combat MDR S. aureus infections through a molecular docking approach. Moreover, interaction amino acid analysis, in silico pharmacokinetics, compound target prediction, pathway enrichment analysis and molecular dynamics (MD) simulations were conducted for further investigation. Molecular docking and interaction analysis showed strong binding affinity towards S. aureus lipase, dihydrofolate reductase, and other MDR S. aureus proteins, including penicillin-binding protein 2a, MepR, D-Ala:D-Ala ligase, and RPP TetM, through hydrophilic and hydrophobic interactions. GMG-ITC also showed a strong binding affinity to cyclooxygenase-2 and FAD-dependent NAD(P)H oxidase, suggesting that it is a potential anti-inflammatory and antioxidant candidate that may eliminate inflammation and oxidative stress associated with S. aureus infections. MD simulations validated the stability of the GMG-ITC molecular interactions determined by molecular docking. In silico pharmacokinetic analysis highlights its potency as a drug candidate, showing strong absorption, distribution, and excretion properties in combination with low toxicity. It acts as an active protease and enzyme inhibitor with moderate activity against GPCR ligands, ion channels, nuclear receptor ligands, and kinases. Enrichment analysis further elucidated its involvement in important biological, molecular, and cellular functions with potential therapeutic applications in diseases like cancer, hepatitis B, and influenza. Results suggest that GMG-ITC is an effective antibacterial agent that could treat MDR S. aureus-associated infections.

Efficacy and safety of novel glycopeptides versus vancomycin for the treatment of gram-positive bacterial infections including methicillin resistant Staphylococcus aureus: A systematic review and meta-analysis

OBJECTIVE

To compare between current evidence of novel glycopeptides against vancomycin for the treatment of gram-positive bacterial infections.

METHODOLOGY

A systematic review and meta-analysis was done. Major databases were searched for eligible randomized control trials that assessed clinical success, microbiological success and safety profile of novel glycopeptides versus vancomycin for infections caused by gram-positive bacteria.

RESULTS

This meta-analysis included eleven trials (7289 participants) comparing telavancin, dalbavancin and oritavancin with vancomycin. No differences were detected between novel glycopeptides and vancomycin for the treatment of skin and soft tissue infections (SSTIs) among modified intent-to-treat patients (OR: 1.04, CI: 0.92-1.17) as well as within the clinically evaluable patients (OR: 1.09, CI: 0.91-1.30). Data analysed from SSTIs, HAP and bacteremia studies on telavancin showed insignificant high clinical response in microbiologically evaluable patients infected with methicillin resistant Staphylococcus aureus (MRSA) (OR: 1.57, CI: 0.94-2.62, p: 0.08) and in the eradication of MRSA (OR: 1.39, CI: 0.99-1.96, P:0.06). Dalbavancin was non-inferior to vancomycin for the treatment of osteomyelitis in a phase II trial, while it was superior to vancomycin for the treatment of bacteremia in a phase II trial. Data analysed from all trials showed similar rates of all-cause mortality between compared antibiotics groups (OR: 0.67, CI: 0.11-4.03). Telavancin was significantly related with higher adverse events (OR: 1.24, CI: 1.07-1.44, P: <0.01) while dalbavancin and oritavancin were associated with significant fewer adverse events (OR: 0.73, CI: 0.57-0.94, p: 0.01; OR: 0.72, CI: 0.59-0.89, p: <0.01 respectively).

CONCLUSION

Efficacy and safety profiles of both dalbavancin and oritavancin were the same as vancomycin in the treatment of gram-positive bacterial infections in different clinical settings, while telavancin might be an effective alternative to vancomycin in MRSA infections, but caution is required during its clinical use due to the high risk of adverse events, especially nephrotoxicity.

Finding the First Potential Inhibitors of Shikimate Kinase from Methicillin Resistant Staphylococcus aureus through Computer-Assisted Drug Design

Methicillin-resistant Staphylococcus aureus (MRSA) is an important threat as it causes serious hospital and community acquired infections with deathly outcomes oftentimes, therefore, development of new treatments against this bacterium is a priority. Shikimate kinase, an enzyme in the shikimate pathway, is considered a good target for developing antimicrobial drugs; this is given because of its pathway, which is essential in bacteria whereas it is absent in mammals. In this work, a computer-assisted drug design strategy was used to report the first potentials inhibitors for Shikimate kinase from methicillin-resistant Staphylococcus aureus (SaSK), employing approximately 5 million compounds from ZINC15 database. Diverse filtering criteria, related to druglike characteristics and virtual docking screening in the shikimate binding site, were performed to select structurally diverse potential inhibitors from SaSK. Molecular dynamics simulations were performed to elucidate the dynamic behavior of each SaSK–ligand complex. The potential inhibitors formed important interactions with residues that are crucial for enzyme catalysis, such as Asp37, Arg61, Gly82, and Arg138. Therefore, the compounds reported provide valuable information and can be seen as the first step toward developing SaSK inhibitors in the search of new drugs against MRSA.

A new antidiabetic foot bacteria formula from marine chitosan nanosilver-metal complex

In more than two-thirds of the diabetic foot ulcer (DFUs) cases, lower limb amputation of foot ulceration is caused by the infection. The role of transition a metal complex as a therapeutic compound is becoming increasingly important. In vitro, four groups of antibiotics and one sulfa drug were tested against diabetic foot resistant bacteria. Using three concentrations of two different prepared metal complexes: copper (Cu) and silver (Ag) - isoniazid (Iso) and nicotinamide (Nicot) were tested against diabetic foot isolates. Results revealed that β-lactam drugs (cephradine and piperacillin) showed the minimum averages of MIC 265 μg/ml against Gram-positive and Gram-negative isolates. Silver isoniazid (Iso-Ag-1) metal complex was selected depending on the maximum averages of MIC against both types of clinical isolates. The combination between β-lactams and Iso-Ag-1 showed maximum FICI averages of 0.24 for Gram-positive and 0.28 for Gram-negative. In addition, a combination between Iso-Ag-1 with squilla chitosan nanoparticles (CSSq-nAg) showed averages of synergistic index by 0.23 against Staphylococcus aureus and 0.13, 0.30, and 0.27 against E. coli, K. pneumoniae, and Ps. aeruginosa, respectively. Final formula of Iso-Ag-1+CSSq-nAg + β-lactams (cephradine and piperacillin) showed a synergistic effect at FICI = 0.044 and 0.047, against G+ve and -ve, respectively. These two combinations showed a slight toxicity against the water flea Daphnia magna by 3.49 and 3.6 ppm, respectively. Results suggest the use of Iso-Ag-1-CSSq-nAg as enhancing agent in combination with β-lactams as a blind therapy in pharmaceutical preparations.

Novel 2,4-disubstituted quinazoline analogs as antibacterial agents with improved cytotoxicity profile: Optimization of the 2,4-substituents

The emergence of bacterial resistance has triggered a multitude of efforts to develop new antibacterial agents. There are many compounds in literature that were reported as potent antibacterial agents, however, they lacked the required safety to mammalian cells or no clear picture about their toxicity profile was presented. Inspired by discovered hit from our in-house library and by previously reported 2,4-diaminosubstituted quinazolines, we describe the design and synthesis of novel 2,4-disubstituted-thioquinazolines (3-13 and 36), 2-thio-4-amino substituted quinazolines (14-33) and 6-substituted 2,4-diamonsubstituted quinazolines (37-39). The synthesized compounds showed potent antibacterial activity against a panel of Gram-positive, efflux deficient E.coli and Mycobacterium smegmatis. The panel also involved resistant strains including methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae, vancomycin-resistant Enterococcus faecalis and vancomycin-resistant Enterococcus faecium, in addition to Mycobacterium smegmatis. The newly synthesized compounds revealed MIC values against the tested strains ranging from 1 to 64 µg/mL with a good safety profile. Most of the 2-thio-4-amino substituted-quinazolines showed significant antimycobacterial activity with the variations at position 2 and 4 offering additional antibacterial activity against the different strains. Compared to previously reported 2,4-diaminosubstituted quinazolines, the bioisosteric replacement of the 2-amino with sulfur offered a successful approach to keep the high antibacterial potency while substantially improving safety profile as indicated by the reduced activity on different cell lines and a lack of hemolytic activity.

Antibiotic Resistance and Virulence Gene Characteristics of Methicillin-Resistant Staphylococcus aureus (MRSA) Isolated from Healthy Edible Marine Fish

Thirty-three (33) isolates of methicillin-resistant Staphylococcus aureus (MRSA) from healthy edible marine fish harvested from two aquaculture settings and the Kariega estuary, South Africa, were characterised in this study. The phenotypic antimicrobial susceptibility profiles to 13 antibiotics were determined, and their antibiotic resistance determinants were assessed. A multiplex PCR was used to determine the epidemiological groups based on the type of SCCmec carriage followed by the detection of staphylococcal enterotoxin-encoding genes sea-sed and the Panton Valentine leucocidin gene (pvl). A high antibiotic resistance percentage (67–81%) was observed for Erythromycin, Ampicillin, Rifampicin, and Clindamycin, while maximum susceptibility to Chloramphenicol (100%), Imipenem (100%), and Ciprofloxacin (94%) was recorded. Nineteen (58%) of the MRSA strains had Vancomycin MICs of ≤2 μg/mL, 4 (12%) with MICs ranging from 4–8 μg/mL, and 10 (30%) with values ≥16 μg/mL. Overall, 27 (82%) isolates were multidrug-resistant (MDR) with Erythromycin-Ampicillin-Rifampicin-Clindamycin (E-AMP-RIP-CD) found to be the dominant antibiotic-resistance phenotype observed in 4 isolates. Resistance genes such as tetM, tetA, ermB, blaZ, and femA were detected in two or more resistant strains. A total of 19 (58%) MRSA strains possessed SCCmec types I, II, or III elements, characteristic of healthcare-associated MRSA (HA-MRSA), while 10 (30%) isolates displayed SCCmec type IVc, characteristic of community-associated MRSA (CA-MRSA). Six (18%) of the multidrug-resistant strains of MRSA were enterotoxigenic, harbouring the see, sea, or sec genes. A prevalence of 18% (6/33) was also recorded for the luk-PVL gene. The findings of this study showed that marine fish contained MDR-MRSA strains that harbour SCCmec types, characteristic of either HA-MRSA or CA-MRSA, but with a low prevalence of enterotoxin and pvl genes. Thus, there is a need for continuous monitoring and implementation of better control strategies within the food chain to minimise contamination of fish with MDR-MRSA and the ultimate spread of the bug.

Influence of administration of antimicrobial medications after tibial plateau leveling osteotomy on surgical site infections: A retrospective study of 308 dogs

OBJECTIVE

To determine the influence of prophylactic administration of oral antimicrobial medications after tibial plateau leveling osteotomy (TPLO) on surgical site infections (SSI) and antimicrobial-resistant infections.

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

Dogs treated with unilateral TPLO (n = 308) between January 2013 and December 2015.

METHODS

Medical records were reviewed for signalment, surgically treated limb, duration of surgery and anesthesia, postoperative administration of antimicrobial medications, antibiotic agent, surgeon, and development of SSI. Statistical analyses included descriptive statistics, simple linear regression, analysis of variance, Fisher's protected least significant difference, and χ² testing.

RESULTS

Data were collected from records of 31 dogs that did not receive antimicrobial medications and 277 dogs that did receive oral antimicrobial medications for 14 days after TPLO. Superficial incisional SSI was detected in two of 31 dogs that did not receive antimicrobial medications and in 48 of 277 dogs that did receive antimicrobial medications (P = .1194). Deep incisional SSI occurred in two of 31 dogs that did not receive antimicrobial medications and in 27 of 277 dogs that did receive antimicrobial medications (P = .5513). Antibiotic-resistant deep incisional SSI occurred in two of 31 dogs that did not receive antimicrobial medications and in 18 of 277 dogs that did receive antimicrobial medications (P = .9920). Body weight correlated with deep incisional SSI and resistant infections. Prolonged duration of surgery and anesthesia were associated with superficial incisional SSI, deep incisional SSI, and antibiotic resistance. Surgeons influenced deep incisional SSI.

CONCLUSION

Previously reported predisposing factors for infection were confirmed, but postoperative administration of antimicrobial medications was not protective against SSI nor did it predispose to antibiotic resistance in our clinical setting.

CLINICAL SIGNIFICANCE

This study does not provide evidence to support administration of prophylactic oral antimicrobial medications after unilateral TPLO.

Daptomycin use in adult inpatients in a Canadian tertiary care setting

BACKGROUND

Daptomycin is approved by Health Canada for the treatment of Staphylococcus aureus bacteremia and complicated skin and soft tissue infections caused by gram-positive organisms, but is often used for other indications. We aimed to understand the indications, dosing, and safety profile of daptomycin use in a Canadian inpatient setting.

METHODS

We included consecutive adult patients who received intravenous daptomycin as inpatients from January 1, 2016, to December 31, 2016, at two tertiary care teaching hospitals in Hamilton, Ontario.

RESULTS

We identified 86 courses in 77 unique patients. S. aureus was the most common pathogen (n = 38, 44%) of which 87% (n = 33) were methicillin-resistant. The most common indications were bloodstream infections (n = 31, 36%). The average treatment duration was 10 days, at an average dose of 7.4 mg/kg. The infectious diseases service was consulted in all but two courses. Less than half of treatment courses were given for an indication approved by Health Canada (n = 41, 48%). Almost half of the unapproved indications (n = 21, 47%) followed Infectious Diseases Society of America (IDSA) recommendations. Creatine kinase elevation of 3 × the upper limit of normal or higher occurred in a small number of courses (n = 7, 8%), with only one instance requiring discontinuation of the drug.

CONCLUSIONS

Daptomycin is being used to treat inpatients for a variety of unapproved indications. Importantly, a sizable portion of these are within IDSA guideline recommendations. Most patients are treated with doses higher than the approved 6 mg/kg without major safety concerns.

Biochemical, Kinetic, and Computational Structural Characterization of Shikimate Kinase from Methicillin-Resistant Staphylococcus aureus

One of the most widespread pathogens worldwide is methicillin-resistant Staphylococcus aureus, a bacterium that provokes severe life-threatening illnesses both in hospitals and in the community. The principal challenge lies in the resistance of MRSA to current treatments, which encourages the study of different molecular targets that could be used to develop new drugs against this infectious agent. With this goal, a detailed characterization of shikimate kinase from this microorganism (SaSK) is described. The results showed that SaSK has a K_m of 0.153 and 224 µM for shikimate and ATP, respectively, and a global reaction rate of 13.4 µmol/min/mg; it is suggested that SaSK utilizes the Bi-Bi Ping Pong reaction mechanism. Furthermore, the physicochemical data indicated that SaSK is an unstable, hydrophilic, and acidic protein. Finally, structural information showed that SaSK presented folding that is typical of its homologous counterparts and contains the typical domains of this family of proteins. Amino acids that have been shown to be important for SaSK protein function are conserved. Therefore, this study provides fundamental information that may aid in the design of inhibitors that could be used to develop new antibacterial agents.

Invitro synergistic activity of lactic acid bacteria against multi-drug resistant staphylococci

Background

Multi-drug resistance in microorganisms is a serious problem at national as well as at a global level. Many researches have suggested alternatives to antibiotics with minimal or no major side effects. LAB is one of the most human-friendly probiotic strains known to mankind from times immemorial. With the objective to deal with progressing antibiotic resistance among microorganisms, the present work demonstrates the inhibitory activity of LAB consortium against MDR clinical isolates.

Methods

Total of nine hospital isolates of staphylococci were obtained and distinguished as S.aureus and coagulase-negative Staphylococcus (CoNS) based on their ability to ferment mannitol and form clumping with citrated plasma. All the test organisms were tested for antibiotic sensitivity with HiMedia (India) Octadisc Combi 92. Sets of L .plantarum, L .acidophilus and L.casei var. rhamnosus were prepared and tested against a standard culture of S.aureus NCIM 2129 by agar well diffusion method. To identify the primary source of substances responsible for inhibitory action, whole broth, cell-free supernatant, and cell lysate was prepared from the above-mentioned set. These were tested for their inhibitory action initially against standard S.aureus NCIM 2127, followed by clinical isolates.

Results

The antibiotic sensitivity profile revealed that all clinical isolates were multi-drug resistant. The maximum inhibitory potential was seen in a combination of the three LAB in the ratio 1:1:1. Highest antagonistic activity was observed with whole broth and cell lysate of LAB consortium. In liquid broth assay, the cell lysate of LAB consortium astoundingly exhibited up to 85% inhibition of multi-drug resistant Staphylococcus isolates.

Conclusions

Our results suggest antagonistic role of LAB metabolites against methicillin resistant staphylococci.

Methicillin-Resistant Staphylococcus aureus Prosthetic Valve Endocarditis: Pathophysiology, Epidemiology, Clinical Presentation, Diagnosis, and Management

Staphylococcus aureus prosthetic valve endocarditis (PVE) remains among the most morbid bacterial infections, with mortality estimates ranging from 40% to 80%. The proportion of PVE cases due to methicillin-resistant Staphylococcus aureus (MRSA) has grown in recent decades, to account for more than 15% of cases of S. aureus PVE and 6% of all cases of PVE. Because no large studies or clinical trials for PVE have been published, most guidelines on the diagnosis and management of MRSA PVE rely upon expert opinion and data from animal models or related conditions (e.g., coagulase-negative Staphylococcus infection). We performed a review of the literature on MRSA PVE to summarize data on pathogenic mechanisms and updates in epidemiology and therapeutic management and to inform diagnostic strategies and priority areas where additional clinical and laboratory data will be particularly useful to guide therapy. Major updates discussed in this review include novel diagnostics, indications for surgical management, the utility of aminoglycosides in medical therapy, and a review of newer antistaphylococcal agents used for the management of MRSA PVE.

N-(1,3,4-oxadiazol-2-yl)benzamide analogs, bacteriostatic agents against methicillin- and vancomycin-resistant bacteria

Various reports of multidrug-resistant bacteria that are immune to all available FDA-approved drugs demand the development of novel chemical scaffolds as antibiotics. From screening a chemical library, we identified compounds with antibacterial activity. The most potent compounds, F6-5 and F6, inhibited growth of various drug-resistant Gram-positive bacterial pathogens at concentrations ranging from 1 μg/mL to 2 μg/mL. Both compounds were active against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate and vancomycin-resistant S. aureus (VISA and VRSA respectively) and vancomycin-resistant Enterococcus faecalis (VRE). Resistance generation experiments revealed that MRSA could develop resistance to the antibiotic ciprofloxacin but not to F6. Excitingly, F6 was found to be non-toxic against mammalian cells. In a mouse skin wound infection model, F6 was equipotent to the antibiotic fusidic acid in reducing MRSA burden.

Treatment of Staphylococcus aureus Infections

Staphylococcus aureus, although generally identified as a commensal, is also a common cause of human bacterial infections, including of the skin and other soft tissues, bones, bloodstream, and respiratory tract. The history of S. aureus treatment is marked by the development of resistance to each new class of antistaphylococcal antimicrobial drugs, including the penicillins, sulfonamides, tetracyclines, glycopeptides, and others, complicating therapy. S. aureus isolates identified in the 1960s were sometimes resistant to methicillin, a ß-lactam antimicrobial active initially against a majority S. aureus strains. These MRSA isolates, resistant to nearly all ß-lactam antimicrobials, were first largely confined to the health care environment and the patients who attended it. However, in the mid-1990s, new strains, known as community-associated (CA-) MRSA strains, emerged. CA-MRSA organisms, compared with health care-associated (HA-) MRSA strain types, are more often susceptible to multiple classes of non ß-lactam antimicrobials. While infections caused by methicillin-susceptible S. aureus (MSSA) strains are usually treated with drugs in the ß-lactam class, such as cephalosporins, oxacillin or nafcillin, MRSA infections are treated with drugs in other antimicrobial classes. The glycopeptide drug vancomycin, and in some countries teicoplanin, is the most common drug used to treat severe MRSA infections. There are now other classes of antimicrobials available to treat staphylococcal infections, including several that have been approved after 2009. The antimicrobial management of invasive and noninvasive S. aureus infections in the ambulatory and in-patient settings is the topic of this review. Also discussed are common adverse effects of antistaphylococcal antimicrobial agents, advantages of one agent over another for specific clinical syndromes, and the use of adjunctive therapies such as surgery and intravenous immunoglobulin. We have detailed considerations in the therapy of noninvasive and invasive S. aureus infections. This is followed by sections on specific clinical infectious syndromes including skin and soft tissue infections, bacteremia, endocarditis and intravascular infections, pneumonia, osteomyelitis and vertebral discitis, epidural abscess, septic arthritis, pyomyositis, mastitis, necrotizing fasciitis, orbital infections, endophthalmitis, parotitis, staphylococcal toxinoses, urogenital infections, and central nervous system infections.

Daptomycin Use After Vancomycin-Induced Neutropenia in a Patient with Left-Sided Endocarditis

Objective:

To report a positive outcome in a patient treated with daptomycin for left-sided endocarditis associated with methicillin-resistant Staphylococcus aureus (MRSA) subsequent to vancomycin-induced neutropenia.

Case Summary:

A 55-year-old African American male was diagnosed with left-sided endocarditis, brain abscesses, and septic arthritis due to community-acquired MRSA. He began treatment with intravenous vancomycin to achieve a trough concentration of 15–20 μg/mL and oral rifampin 600 mg/day. A repair and resection of the mitral valve was completed on day 15 of hospitalization. Vancomycin was discontinued on day 36 secondary to drug-induced neutropenia (absolute neutrophil count nadir 162 cells/μL). Intravenous therapy with daptomycin 6 mg/kg every 24 hours was then initiated and the neutropenia resolved. The patient was discharged from the hospital on day 56.

Discussion:

Upon discontinuation of vancomycin, treatment options were limited to a small number of alternatives. Documented clinical experience and relevant studies are limited regarding the use of quinupristin/dalfopristin (Q/D), linezolid, trimethoprim/sulfamethoxazole (TMP/SMX), and daptomycin for the treatment of MRSA left-sided endocarditis. Daptomycin was selected because of its bactericidal qualities and its recent approval for this indication. The prognostic outlook for use of daptomycin in this treatment was uncertain; however, Q/D, linezolid, and TMP/SMX posed greater risks of failure.

Conclusions:

Treatment of MRSA left-sided endocarditis in patients intolerant to vancomycin is challenging. The positive outcome in our patient is likely attributable to aggressive vancomycin dosing and extended duration of treatment prior to the initiation of daptomycin. The use of daptomycin in this case enabled successful management of left-sided endocarditis.

Systematic Review and Meta-Analysis of the Efficacy and Safety of Telavancin for Treatment of Infectious Disease: Are We Clearer?

Objective: Telavancin is approved to treat complicated skin and skin structure infections, hospital-acquired, and ventilator-associated bacterial pneumonia caused by Staphylococcus aureus. A previous meta-analysis of randomized controlled trials suggested that it might be an alternative to vancomycin in cases of difficult-to-treat meticillin-resistant S. aureus infections. We did a meta-analysis including one new trial to access the efficacy and safety of telavancin. Methods: We searched PubMed, Cochrane Central Register of Controlled Trials, EMBASE and ClinicalTrials.gov up to December 30, 2015 to identify randomized controlled trials that assessed the clinical efficacy, eradication efficiency, adverse events and laboratory abnormalities of telavancin vs. other antibiotic agents for bacterial infection. Meta-analysis was performed using Review Manager 5.3.0. Results: Five studies (3790 participants) were included in the meta-analysis. There was no significant difference in treatment success with telavancin than with control antibiotic agents. The pooled pathogen eradication for the telavancin group was numerically higher than that for the control groups, but there was no significant difference. While all-cause mortalities and serious adverse events were comparable between telavancin and control antibiotic agents, adverse event-related withdrawals (OR 1.47, 95% CI 1.13-1.91) were higher in telavancin group. The total number adverse events were more in the telavancin group than in the control groups, especially in the digestive system (OR 1.57, 95% CI 1.37-1.79), nervous system (OR 2.14, 95% CI 1.86-2.47) and urogenital system (OR 2.54, 95% CI 1.99-3.25). Serum creatinine increase (OR 2.25, 95% Cl 1.78-2.85) and hypokalemia (OR 1.74, 95% CI 1.19-2.53) occurred more frequently in telavancin group compared to control groups. Conclusion: Telavancin may be as effective as but no better than the comparison therapy for S. aureus infection. However, because of the high risk of adverse event-related withdrawals and potential nephrotoxicity, prudence with the clinical use of telavancin in infections is required.

Managing skin and soft-tissue infection and nosocomial pneumonia caused by MRSA: a 2014 follow-up survey

As a follow-up to our 2009 survey, in order to explore opinion and practice on the epidemiology and management of meticillin-resistant Staphylococcus aureus (MRSA) in Europe, we conducted a second survey to elicit current opinions on this topic, particularly around antibiotic choice, dose, duration and route of administration. We also aimed to further understand how the management of MRSA has evolved in Europe during the past 5 years. Members of an expert panel of infectious diseases specialists convened in London (UK) in January 2014 to identify and discuss key issues in the management of MRSA. Following this meeting, a survey was developed comprising 36 questions covering a wide range of topics on MRSA complicated skin and soft-tissue infection and nosocomial pneumonia management. The survey instrument, a web-based questionnaire, was sent to the International Society of Chemotherapy for distribution to registered European infection societies and their members. This article reports the survey results from the European respondents. At the time of the original survey, the epidemiology of MRSA varied significantly across Europe and there were differing views on best practice. The current findings suggest that the epidemiology of healthcare-associated MRSA in Europe is, if anything, even more polarised, whilst community-acquired MRSA has become much more common. However, there now appears to be a much greater knowledge of current treatment/management options, and antimicrobial stewardship has moved forward considerably in the 5 years since the last survey.

Generation of a Novel Staphylococcus aureus Ghost Vaccine and Examination of Its Immunogenicity against Virulent Challenge in Rats

Staphylococcus aureus is a Gram-positive pathogen that causes a wide range of infections in humans and animals. Bacterial ghosts are nonliving, empty cell envelopes and are well represented as novel vaccine candidates. In this study, we examined the immunogenicity and protective efficacy of S. aureus ghosts (SAGs) against a virulent challenge in rats. Nonliving SAGs were generated by using the MIC of sodium hydroxide. The formation of a transmembrane lysis tunnel structure in SAGs was visualized by scanning electron microscopy. To investigate these SAGs as a vaccine candidate, rats were divided into four groups, A (nonimmunized control), B (orally immunized), C (subcutaneously immunized), and D (intravenously immunized). The IgG antibody responses were significantly stronger in the SAG-immunized groups than in the nonimmunized control group (P < 0.05). Moreover, a significant increase in the populations of CD4(+) and CD8(+) T cells was observed in all three immunized groups (P < 0.05). We also found that serum bactericidal antibodies were significantly elicited in the SAG-immunized groups (P < 0.05). Most importantly, the bacterial loads in the immunized groups were significantly lower than those in the nonimmunized control group (P < 0.01). These results suggest that immunization with SAGs induces immune responses and provides protection against a virulent S. aureus challenge.

Copper nanoparticles as an efflux pump inhibitor to tackle drug resistant bacteria

Casein capped copper nanoparticles at sub inhibitory concentrations function as an efflux pump inhibitor and restores susceptibility to antibiotics in drug resistant bacteria.

Double-disk synergy test for detection of synergistic effect between antibiotics against nosocomial strains of staphylococcus aureus

Objective:

Synergistic effect between commonly used antibiotics against nosocomial multidrug-resistant strains of Staphylococcus aureus, if present, could provide a viable option as an alternative therapy for infections due to this pathogen. The aim of this study was searching for any synergistic effect between several antibiotics against drug-resistant strains of S. aureus with nosocomial origin using double-disk synergy test and to determine the applicability of this test for such a purpose.

Methods:

Over a 6-month period, strains of S. aureus isolated from clinical specimens of hospitalized patients with documented nosocomial infection underwent disk diffusion test using antibiotic disks of oxacillin, cephalothin, clindamycin, ciprofloxacin, vancomycin, cotrimoxazole, rifampin, erythromycin, gentamicin and meropenem. Double-disk synergy test was performed for all isolates resistant to at least two of applied antibiotics. Combinations of all possible pairs of antibiotics (to which the microorganism was resistant) were tested by placing antibiotic disks at distance of 20 mm from each other (center to center). After 16- 20 hours of incubation, if synergistic effect was present among two antibiotics, an inhibition zone was formed between their disks.

Findings:

Among all of possible two-antibiotic combinations tested for 41 resistant isolates, only two cases of synergistic effect were detected; both effects were among rifampin and cotrimoxazole.

Conclusion:

The combination of rifampin and cotrimoxazole could provide a viable option for treatment of infections due to resistant strains of S. aureus; however, clinical trials are needed before any new recommendation. Also, double-disk synergy test seems to be capable of detecting the synergistic effect between antibiotics at in vitro level.

Antifolate agents: a patent review (2010 - 2013)

INTRODUCTION

The folate biosynthetic pathway, responsible for the de novo synthesis of thymidine and other key cellular components, is essential in all life forms and is especially critical in rapidly proliferating cells. As such, druggable targets along this pathway offer opportunities to impact many disease states such as cancer, infectious disease and autoimmune disease. In this article, recent progress on the development of antifolate compounds is reviewed.

AREAS COVERED

The evaluation of the patent literature during the period 2010 - 2013 focused on any compounds inhibiting recognized targets on the folate biosynthetic pathway.

EXPERT OPINION

The folate pathway constitutes a well-validated and well-characterized set of targets; this pathway continues to elicit considerable enthusiasm for new drug discovery from both academic and industrial pharmaceutical research groups. Within the pathway, the enzymes dihydrofolate reductase and thymidylate synthase persist as the most attractive targets for new drug discovery for the treatment of cancer and infectious disease. Importantly, new potential targets for antifolates such as those on the purine biosynthetic pathway have been recently explored. The use of structure-based drug design is a major aspect in modern approaches to these drug targets.

Fragment Screening on Staphylococcus aureus HPPK – a Folate Pathway Target

An NMR-based screen of a commercially available fragment library was performed on the folate pathway antimicrobial target, 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase from Staphylococcus aureus (SaHPPK). Initial 1D saturation transfer difference-NMR screening resulted in an impractically high hit rate (43 %), which advocated the use of a strategy based on 2D (SOFAST) 15N HMQC NMR experiments. Chemical shift perturbations were used to identify, validate, and map the location of 16 initial binders (hit rate of 2 %). Fourteen compounds were purchased based on an identified thioamide pharmacophore. Binding affinities (Kd) were measured by surface plasmon resonance, revealing a modest improvement in potency over the initial 16 hits, with the best fragment found to bind to the apo enzyme with a Kd of 420 µM, corresponding to a ligand efficiency of 1.8 kJ/heavy atom. Four fragments identified represent useful starting points for the generation of leads that may ultimately be developed into new antimicrobial agents.

Winning the arms race by improving drug discovery against mutating targets

Enzymes are often excellent drug targets. Yet drug pressure on an enzyme target often fosters the rise of cells with resistance-conferring mutations, some of which may compromise fitness and others that compensate to restore fitness. This review presents, first, a structural analysis of a diverse group of wild-type and mutant enzyme targets and, second, an in-depth analysis of five diverse targets to elucidate a broader perspective of the effects of resistance-conferring mutations on protein or organismal fitness. The structural analysis reveals that resistance-conferring mutations may introduce steric hindrance or eliminate critical interactions, as expected, but that they may also have indirect effects such as altering protein dynamics and enzyme kinetics. The structure-based development of the latest generation of inhibitors targeting HIV reverse transcriptase, P. falciparum and S. aureus dihydrofolate reductase, neuraminidase, and epithelial growth factor receptor (EGFR) tyrosine kinase, is highlighted to emphasize lessons that may be applied to future drug discovery to overcome mutation-induced resistance. Successful next-generation drugs tend to be more flexible and exploit a greater number of interactions mimicking those of the substrate with conserved residues.

Toward new therapeutics for skin and soft tissue infections: propargyl-linked antifolates are potent inhibitors of MRSA and Streptococcus pyogenes

Hospital- and community-acquired, complicated skin and soft tissue infections, often attributed to Staphylococcus aureus and Streptococcus pyogenes, present a significant health burden that is associated with increased health care costs and mortality. As these two species are difficult to discern on diagnosis and are associated with differential profiles of drug resistance, the development of an efficacious antibacterial agent that targets both organisms is a high priority. Herein we describe a structure-based drug development effort that has produced highly potent inhibitors of dihydrofolate reductase from both species. Optimized propargyl-linked antifolates containing a key pyridyl substituent display antibacterial activity against both methicillin-resistant S. aureus and S. pyogenes at MIC values below 0.1 µg/mL and minimal cytotoxicity against mammalian cells. Further evaluation against a panel of clinical isolates shows good efficacy against a range of important phenotypes such as hospital- and community-acquired strains as well as strains resistant to vancomycin.

The MUT056399 inhibitor of FabI is a new antistaphylococcal compound

MUT056399 is a highly potent new inhibitor of the FabI enzyme of both Staphylococcus aureus and Escherichia coli. In vitro, MUT056399 was very active against S. aureus strains, including methicillin-susceptible S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), linezolid-resistant, and multidrug-resistant strains, with MIC(90)s between 0.03 and 0.12 μg/ml. MUT056399 was also active against coagulase-negative staphylococci, with MIC(90)s between 0.12 and 4 μg/ml. The antibacterial spectrum is consistent with specific FabI inhibition with no activity against bacteria using FabK but activity against FabI-containing Gram-negative bacilli. In vitro, resistant clones of S. aureus were obtained at a low frequency. All of the resistant clones analyzed were found to contain mutations in the fabI gene. In vivo, MUT056399, administered subcutaneously, protected mice from a lethal systemic infection induced by MSSA, MRSA, and vancomycin-intermediate S. aureus strains (50% effective doses ranging from 19.3 mg/kg/day to 49.6 mg/kg/day). In the nonneutropenic murine thigh infection model, the same treatment with MUT056399 reduced the bacterial multiplication of MSSA and MRSA in the thighs of immunocompetent mice. These properties support MUT056399 as a very promising candidate for a novel drug to treat severe staphylococcal infections.

The challenge of developing robust drugs to overcome resistance

Drug resistance is problematic in microbial disease, viral disease and cancer. Understanding at the outset that resistance will impact the effectiveness of any new drug that is developed for these disease categories is imperative. In this Feature, we detail approaches that have been taken with selected drug targets to reduce the susceptibility of new drugs to resistance mechanisms. We will also define the concepts of robust drugs and resilient targets, and discuss how the design of robust drugs and the selection of resilient targets can lead to successful strategies for combating resistance.

A review of telavancin in the treatment of complicated skin and skin structure infections (cSSSI)

Telavancin is a novel antibiotic being investigated for the treatment of serious infections caused by Gram-positive bacteria, including complicated skin and skin structure infections (cSSSI) and pneumonia. This once-daily intravenous lipoglycopeptide exerts rapid bactericidal activity via a dual mechanism of action. It is intended for use to combat infections caused by Staphylococcus aureus and other Gram-positive bacteria, including methicillin-resistant and vancomycin-intermediate strains of S. aureus (MRSA and VISA, respectively). Vancomycin is the current gold standard in treating serious infections caused by Gram-positive bacteria, especially MRSA. In recent clinical trials, telavancin has shown excellent efficacy in phase II and III multinational, randomized, double-blinded studies of cSSSI. In the phase II FAST 2 study, which compared telavancin 10 mg/kg intravenously q 24 h vs standard therapy (an antistaphylococcal penicillin at 2 g IV q 6 h or vancomycin 1 gm IV q 12 h), the clinical success rate in the telavancin-treated group was 96% vs 94% in the standard therapy group. In two identical phase III trials comparing telavancin versus vancomycin at the doses of the FAST 2 study for cSSSI, the clinical cure rates were 88.3% and 87.1%, respectively. Two additional phase III clinical trials investigating telavancin for use in hospital-acquired pneumonia, caused by Gram-positive bacteria are currently ongoing. Telavancin is currently under regulatory review in both the United States and Europe for the indication of treatment of cSSSI.

Optimizing delivery of care for patients with MRSA infection: focus on transitions of care

Staphylococcus aureus is among the most prevalent pathogens isolated from hospitalized patients; those infected with methicillin-resistant strains have longer hospital stays and higher total costs compared with those infected by methicillin-susceptible strains. A multidisciplinary team of health care providers, including hospitalists and other hospital-based physicians, clinical pharmacists, infectious disease specialists, infection control professionals, and case managers, is key to improving treatment and outcomes in these patients. Optimizing transitions of care for hospitalized patients with S aureus infections can improve quality and reduce total costs of care. Hospital length of stay can be shortened by initiating timely, appropriate empiric therapy and by transitioning suitable patients to outpatient antimicrobial therapy. The number of hospitalizations can be reduced by identifying patients who are suitable candidates for initial outpatient antimicrobial therapy. Consistent with good antimicrobial stewardship, the risk of resistance can be minimized by de-escalating empiric therapy to a more narrow-spectrum agent once culture and susceptibility testing results are known. There are several antimicrobial agents available for the management of S aureus infections, including methicillin-resistant S aureus. Consideration of these agents' characteristics may facilitate optimal transition of patients through health care settings.

Critical shortage of new antibiotics in development against multidrug-resistant bacteria-Time to react is now

Two commercial databases (Pharmaprojects and Adis Insight R&D) were queried for antibacterial agents in clinical development. Particular attention was given to antibacterial agents for systemic administration. For each agent, reviewers were requested to indicate whether its spectrum of activity covered a set of selected multidrug-resistant bacteria, and whether it had a new mechanism of action or a new target. In addition, PubMed was searched for antibacterial agents in development that appeared in review articles. Out of 90 agents that were considered to fulfil the inclusion criteria for the analysis, 66 were new active substances. Fifteen of these could be systemically administered and were assessed as acting via a new or possibly new mechanism of action or on a new or possibly new target. Out of these, 12 agents were assessed as having documented in vitro activity against antibiotic-resistant Gram-positive bacteria and only four had documented in vitro activity against antibiotic-resistant Gram-negative bacteria. Of these four, two acted on new or possibly new targets and, crucially, none acted via new mechanisms of action. There is an urgent need to address the lack of effective treatments to meet the increasing public health burden caused by multidrug-resistant bacteria, in particular against Gram-negative bacteria.

Doripenem: a new carbapenem antibiotic

PURPOSE

The chemistry, pharmacology, antimicrobial activity, pharmacokinetics, pharmacodynamics, efficacy and safety in humans, and formulary considerations of doripenem are reviewed.

SUMMARY

Doripenem, a member of the β-lactam class of antibiotics, is the newest addition to the carbapenems. It exhibits concentration-independent bactericidal activity against gram-positive bacteria; enteric and nonenteric gram-negative bacteria, including extended-spectrum β-lactamase-producing strains; and anaerobic pathogens. Doripenem was found to be noninferior to meropenem in the treatment of complicated intraabdominal infections and noninferior to levofloxacin in the treatment of complicated urinary tract infections including pyelonephritis and was granted marketing approval by the Food and Drug Administration for these two indications. Doripenem was also found to be noninferior to imipenem in the treatment of ventilator-associated pneumonia and noninferior to piperacillin-tazobactam in the treatment of hospital-acquired pneumonia. It has a favorable safety profile, with gastrointestinal complaints and headache being the most common adverse effects and allergic reactions the most serious adverse effects. Doripenem has a relatively low potential to induce seizures. The only known clinically relevant drug interaction is that coadministration with valproic acid may result in reductions of valproic acid serum concentrations. As with most renally eliminated antibiotics, the dose of doripenem should be adjusted according to kidney function.

CONCLUSION

Doripenem is an injectable carbapenem antibiotic with a spectrum of activity comparable to that of imipenem and meropenem. Its safety is similar to that of other carbapenems.

Clinical Experience with Linezolid at a Large Academic Medical Center: A Case Series and Review of the Literature

Purpose

The objectives of this study were to evaluate current patterns of use, microbiologic cure rates, and hematologic toxicities, including identification of risk factors, associated with linezolid utilization at our institution.

Methods

Utilization, clinical, microbiological, and toxicity data were collected prospectively over an 8-month period (August 1, 2006 to March 31, 2007). Binary logistic and multivariate stepwise regression analyses were performed to identify potential risk factors for linezolid-associated thrombocytopenia and anemia.

Results

A total of 116 linezolid courses (102 patients) were identified with a mean duration of therapy of 12.3 days. Appropriate infectious disease service approval and consults were found in 87.9% and 62.1% of the cases, respectively. Bloodstream, urinary tract, and respiratory tract infections accounted for 29%, 21%, and 16% of clinical indications, respectively. Vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and coagulase-negative staphylococci accounted for 43%, 24%, and 7% of clinical isolates, respectively. Overall, the microbiologic cure rate among evaluable patients was 83.8%. Development of thrombocytopenia was found in approximately 30% of linezolid-treated patients. Risk factors for linezolid-associated thrombocytopenia included female gender (OR 5.66, P = .002), serum creatinine (SCr) ≥ 2 mg/dL (OR 4.48, P = .009), intensive care unit admission (OR 3.06, P = .038), and duration of therapy ≥ 28 days (OR 3.76, P = .049).

Conclusion

Utilization patterns may suggest strategies for conserving linezolid, including improved compliance with current approval policies and clinical pathway development. Linezolid microbiological cure rates were similar to those found in the primary literature. Linezolid-associated thrombocytopenia was common and risk factors were identified. Further well-designed prospective studies are needed to confirm these findings. Hosp Pharm-2010;45(12):916-926

Methicillin-resistant Staphylococcus aureus: the superbug

Over the last decade, methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged as serious pathogens in the nosocomial and community setting. Hospitalization costs associated with MRSA infections are substantially greater than those associated with methicillin-sensitive S. aureus (MSSA) infections, and MRSA has wider economic effects that involve indirect costs to the patient and to society. In addition, there is some evidence suggesting that MRSA infections increase morbidity and the risk of mortality. Glycopeptides are the backbone antibiotics for the treatment of MRSA infections. However, several recent reports have highlighted the limitations of vancomycin, and its role in the management of serious infections is now being reconsidered. Several new antimicrobials demonstrate in vitro activity against MRSA and other Gram-positive bacteria. Data from large surveys indicate that linezolid, daptomycin, and tigecycline are almost universally active against MRSA. This review will briefly discuss the epidemiology, costs, outcome, and therapeutic options for the management of MRSA infections.

Efficacy of fosfomycin and its combination with linezolid, vancomycin and imipenem in an experimental peritonitis model caused by a Staphylococcus aureus strain with reduced susceptibility to vancomycin

The objective of this study was to evaluate the in vitro and in vivo efficacies of therapies including fosfomycin against clinical Staphylococcus aureus isolates with reduced susceptibility to vancomycin (hGISA). Time-kill curves were performed over 24 h. Peritonitis in C57BL/6 mice was induced by intraperitoneal inoculation of 10(8) CFU/ml. Four hours later (0 h), therapy was started and the treatment groups were: control (not treated), fosfomycin (100 mg/kg/5 h), vancomycin (60 mg/kg/5 h), imipenem (30 mg/kg/5 h), fosfomycin plus linezolid, fosfomycin plus vancomycin and fosfomycin plus imipenem, receiving subcutaneous therapy over 25 h. Bacterial counts in peritoneal fluid, bacteraemia and mortality rates were determined. In vitro, fosfomycin showed a synergistic effect when combined with the other antimicrobials tested. In the animal model, fosfomycin combinations were effective and significantly reduced the bacteraemia rates achieved in the control, imipenem and vancomycin groups (p < 0.05). The best combination in vivo was fosfomycin plus imipenem. Also, fosfomycin plus linezolid was significantly better than vancomycin alone, reducing the bacterial concentration in the peritoneal fluid. In conclusion, in vitro and in vivo, fosfomycin in combination with linezolid, vancomycin or imipenem exerted a good activity. Fosfomycin plus imipenem was the most active combination, decreasing 3 log CFU/ml, and appears to be a promising combination for clinical practice.

In vitro and in vivo activities of linezolid alone and combined with vancomycin and imipenem against Staphylococcus aureus with reduced susceptibility to glycopeptides

The objective of this study was to evaluate the in vitro and in vivo efficacies of linezolid (35 mg/kg/5 h), vancomycin (60 mg/kg/5 h), imipenem (30 mg/kg/5 h), linezolid+imipenem, linezolid+vancomycin and vancomycin+imipenem against two clinical Staphylococcus aureus isolates with reduced susceptibility to glycopeptides using time–kill curves and the murine peritonitis model. Time–kill curves were performed over 24 h. For the murine peritonitis model, peritonitis was induced by the intraperitoneal inoculation of 10⁸ CFU/ml of each bacterial strain. Four hours later (0 h), the mice were randomly assigned to a control group or to therapeutic groups receiving subcutaneous treatment for 25 h. Bacterial counts in peritoneal fluid, bacteraemia and mortality rates were determined. The time–kill curves showed that the addition of linezolid to imipenem yielded synergistic results after 24 h. The addition of linezolid decreased vancomycin activity. In the animal model, vancomycin and linezolid monotherapies produced comparable bacterial decreases in mice infected with each strain but linezolid achieved higher rates of blood sterilisation. Linezolid tested either in monotherapy or in combination showed similar efficacy against both strains in terms of bacterial killing, number of negative blood cultures and survival. Linezolid and vancomycin were moderately bactericidal and similar in efficacy against glycopeptide-intermediate or -resistant S. aureus. Linezolid combinations, as effective as linezolid tested alone, could be considered as alternative options for the treatment of glycopeptide-intermediate S. aureus (GISA) infections.

A European survey of antibiotic management of methicillin-resistant Staphylococcus aureus infection: current clinical opinion and practice

Although the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) varies across Europe, healthcare-associated MRSA infections are common in many countries. Despite several national guidelines, the approach to treatment of MRSA infections varies across the continent, and there are multiple areas of management uncertainty for which there is little clinical evidence to guide practice. A faculty, convened to explore some of these areas, devised a survey that was used to compare the perspectives of infection specialists from across Europe on the management of MRSA infections with those of the faculty specialists. The survey instrument, a web-based questionnaire, was sent to 3840 registered delegates of the 19th European Congress of Clinical Microbiology and Infectious Diseases, held in April 2009. Of the 501 (13%) respondents to the survey, 84% were infection/microbiology specialists and 80% were from Europe. This article reports the survey results from European respondents, and shows a broad range of opinion and practice on a variety of issues pertaining to the management of minor and serious MRSA infections, such as pneumonia, bacteraemia, and skin and soft tissue infections. The issues include changing epidemiology, when and when not to treat, choice of treatment, and duration and route of treatment. The survey identified areas where practice can be improved and where further research is needed, and also identified areas of pan-European consensus of opinion that could be applied to European guidelines for the management of MRSA infection.

Crystallization and preliminary X-ray analysis of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase from Staphylococcus aureus

6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) catalyzes the Mg(2+)-dependent transfer of pyrophosphate from ATP to 6-hydroxymethyl-7,8-dihydropterin (HMDP), forming 6-hydroxymethyl-7,8-dihydropterin pyrophosphate, which is a critical step in the de novo folic acid-biosynthesis pathway. Diffraction-quality crystals of HPPK from the medically relevant species Staphylococcus aureus were grown in the presence of ammonium sulfate or sodium malonate and diffracted to better than 1.65 A resolution. The crystals belonged to space group P2(1), with unit-cell parameters a = 36.8, b = 76.6, c = 51.5 A, alpha = gamma = 90.0, beta = 100.2 degrees . The crystals contained two molecules per asymmetric unit, with a volume per protein weight (V(M)) of 2.04 A(3) Da(-1) and an estimated solvent content of 39.6%.

Staphylococcus aureus meningitis: case series and literature review

Staphylococcus aureus meningitis is a challenging disease and little is known about its epidemiology. There are no established management guidelines. We retrospectively reviewed the clinical information, bacteriologic data, and outcomes of all 33 patients with cerebrospinal fluid (CSF) cultures positive for S aureus seen at a single urban teaching hospital from 1999 to 2008. Pulsed-field gel electrophoresis (PFGE) and polymerase chain reaction for staphylococcal cassette chromosome mec (SCCmec), accessory gene regulator (agr) typing, and Panton-Valentine leukocidin (PVL) loci were done on methicillin-resistant S aureus (MRSA) CSF isolates starting in 2005. S aureus caused 12 (36%) cases of postoperative and 21 (64%) cases of hematogenous meningitis. MRSA isolates were found in 6 (50%) cases of postoperative and 10 (48%) cases of hematogenous meningitis. Twelve (75%) of the 16 MRSA infections occurred in the last 5 years of the study. Hematogenous meningitis was associated with older age (p = 0.04), injection drug use (p < 0.01), community-acquired infection (p < 0.01), underlying disease (p = 0.01), staphylococcal infection outside the central nervous system (p = 0.01), altered mental status (p = 0.02), fever (p = 0.01), septic shock (p = 0.03), and bacteremia (p < 0.01). The analysis of the 9 MRSA isolates showed 3 PFGE types: 3 USA100 (33%), 5 USA300 (56%), and 1 USAnot100-1100 (11%). For SCCmec typing, there were 2 (22%) type II and 7 (78%) type IV. All USA300 strains were SCCmec IVa. For agr typing, there were 5 (56%) type I and 4 (44%) type II. Three isolates (33%) were positive for the PVL gene and were USA300 strains. Most patients received nafcillin or vancomycin with or without rifampin or trimethoprim/sulfamethoxazole for a mean period of 17 days (range, 1-42 d). Overall mortality was 36%, and it was associated with community-acquired infection (p = 0.02). Postoperative and hematogenous S aureus meningitis are distinct clinical syndromes. S aureus hematogenous meningitis has devastating clinical consequences and elevated mortality rates, especially if it is acquired in the community. The incidence of MRSA meningitis increased over the last 5 years of the study. Treatment of choice is nafcillin for methicillin-sensitive strains and vancomycin for MRSA strains. The addition of trimethoprim/sulfamethoxazole or rifampin to vancomycin is recommended in severe cases and community-acquired MRSA infections. Linezolid is also a good option due to its good CSF penetration and favorable case reports. The mortality rate is higher in infections acquired in the community.

Antibiotics for gram-positive bacterial infections: vancomycin, teicoplanin, quinupristin/dalfopristin, oxazolidinones, daptomycin, dalbavancin, and telavancin

An overview of the mechanism of action, dosing, clinical indications, and toxicities of the glycopeptide vancomycin is provided. The emerging gram-positive bacterial resistance to antimicrobials and its mechanisms are reviewed. Strategies to control this emergence of resistance are expected to be proposed. Newer antimicrobial agents that have activity against vancomycin-resistant organisms are now available and play a critical role in the treatment of life-threatening infections.