TOC-39, a novel parenteral broad-spectrum cephalosporin with excellent activity against methicillin-resistant Staphylococcus aureus

QSAR analysis of five generations of cephalosporins to establish the structural basis of activity against methicillin-resistant and methicillin-sensitive Staphylococcus aureus

Solving the worldwide problem of growing bacterial drug resistance will require a short-run and medium-term strategy. Structure-activity relationship (SAR) and quantitative SAR (QSAR) analyses have recently been utilized to reveal the molecular basis of the antibacterial activity and antibacterial spectrum of penicillins, the use of which is no longer solely empirical. Likewise, a more rational drug design can be achieved with cephalosporins, the largest group of β-lactam antibiotics. The current contribution aimed to establish the molecular and physicochemical basis of the antibacterial activity of five generations of cephalosporins on methicillin-sensitive (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). With SAR and QSAR analyses, the molecular portions that provide essential and additional antibacterial activity were identified. The substitutions with greater volume and polarity on the R2 side chain of the cephem nucleus increase potency on MSSA. The best effect is produced by substitutions with polar nitrogen atoms at the alpha-carbon (Cα). Substitutions with greater volume and polarity on the R1 side chain further enhance antibacterial activity. In contrast, the effect against MRSA seems to be independent of any substitution on R2 or at the Cα, while depending on the accessory portions with greater volume and polarity on R1.

β-Lactams and β-Lactamase Inhibitors: An Overview

β-Lactams are the most widely used class of antibiotics. Since the discovery of benzylpenicillin in the 1920s, thousands of new penicillin derivatives and related β-lactam classes of cephalosporins, cephamycins, monobactams, and carbapenems have been discovered. Each new class of β-lactam has been developed either to increase the spectrum of activity to include additional bacterial species or to address specific resistance mechanisms that have arisen in the targeted bacterial population. Resistance to β-lactams is primarily because of bacterially produced β-lactamase enzymes that hydrolyze the β-lactam ring, thereby inactivating the drug. The newest effort to circumvent resistance is the development of novel broad-spectrum β-lactamase inhibitors that work against many problematic β-lactamases, including cephalosporinases and serine-based carbapenemases, which severely limit therapeutic options. This work provides a comprehensive overview of β-lactam antibiotics that are currently in use, as well as a look ahead to several new compounds that are in the development pipeline.

Osteoprotegerin Regulates Pancreatic β-Cell Homeostasis upon Microbial Invasion

Osteoprotegerin (OPG), a decoy receptor for receptor activator of NF-κB ligand (RANKL), antagonizes RANKL’s osteoclastogenic function in bone. We previously demonstrated that systemic administration of lipopolysaccharide (LPS) to mice elevates OPG levels and reduces RANKL levels in peripheral blood. Here, we show that mice infected with Salmonella, Staphylococcus, Mycobacteria or influenza virus also show elevated serum OPG levels. We then asked whether OPG upregulation following microbial invasion had an effect outside of bone. To do so, we treated mice with LPS and observed OPG production in pancreas, especially in β-cells of pancreatic islets. Insulin release following LPS administration was enhanced in mice lacking OPG, suggesting that OPG inhibits insulin secretion under acute inflammatory conditions. Consistently, treatment of MIN6 pancreatic β-cells with OPG decreased their insulin secretion following glucose stimulation in the presence of LPS. Finally, our findings suggest that LPS-induced OPG upregulation is mediated in part by activator protein (AP)-1 family transcription factors, particularly Fos proteins. Overall, we report that acute microbial infection elevates serum OPG, which maintains β-cell homeostasis by restricting glucose-stimulated insulin secretion, possibly preventing microbe-induced exhaustion of β-cell secretory capacity.

In vitro and in vivo anti-MRSA activities of nosokomycins

The anti-methicillin-resistant Staphylococcus aureus (MRSA) activity of nosokomycins A to D discovered in the silkworm-MRSA infection screening was investigated. The minimum inhibitory concentration (MIC) values of nosokomycins for authentic MRSA and S. aureus strains were calculated to be 0.06 to 2.0 μg/mL. They also showed potent inhibitory activity against 54 clinically isolated MRSA strains. Furthermore, nosokomycin A proved effective in the mouse-MRSA infection model.

The nonantibiotic small molecule cyslabdan enhances the potency of β-lactams against MRSA by inhibiting pentaglycine interpeptide bridge synthesis

The nonantibiotic small molecule cyslabdan, a labdan-type diterpene produced by Streptomyces sp. K04-0144, markedly potentiated the activity of the β-lactam drug imipenem against methicillin-resistant Staphylococcus aureus (MRSA). To study the mechanism of action of cyslabdan, the proteins that bind to cyslabdan were investigated in an MRSA lysate, which led to the identification of FemA, which is involved in the synthesis of the pentaglycine interpeptide bridge of the peptidoglycan of MRSA. Furthermore, binding assay of cyslabdan to FemB and FemX with the function similar to FemA revealed that cyslabdan had an affinity for FemB but not FemX. In an enzyme-based assay, cyslabdan inhibited FemA activity, where as did not affected FemX and FemB activities. Nonglycyl and monoglycyl murein monomers were accumulated by cyslabdan in the peptidoglycan of MRSA cell walls. These findings indicated that cyslabdan primarily inhibits FemA, thereby suppressing pentaglycine interpeptide bridge synthesis. This protein is a key factor in the determination of β-lactam resistance in MRSA, and our findings provide a new strategy for combating MRSA.

New β-lactam antibiotics and β-lactamase inhibitors

IMPORTANCE OF THE FIELD

β-Lactam antibiotics are among the most frequently prescribed antibiotics used to treat bacterial infections. However, their utility is being threatened by the worldwide proliferation of β-lactamases with broad hydrolytic capabilities, especially in multidrug-resistant Gram-negative bacteria.

AREAS COVERED IN THIS REVIEW

This review describes new β-lactams and β-lactamase inhibitors described in the patent literature primarily between 2007 and 2010, together with supportive meeting abstracts and relevant descriptive literature.

WHAT THE READER WILL GAIN

Readers will learn which classes of β-lactam antibiotics are being explored as the most promising groups of compounds to counteract resistance in Gram-negative pathogenic bacteria. Somewhat surprisingly, few traditional β-lactam classes such as penicillins or cephalosporins were described in the literature, other than in combinations with other β-lactams or β-lactamase inhibitors that are being developed to inhibit enzymes from all molecular classes.

TAKE HOME MESSAGE

β-Lactam antibiotics are currently being developed as monotherapy by only a few companies. The major emphasis in the past 4 years has been the discovery of novel β-lactamase inhibitors or inhibitor combinations that will allow use of β-lactams against multidrug-resistant bacteria. The use of β-lactams as single agents appears to be a limited option for the future.

Two diallyl sulphides derived from garlic inhibit meticillin-resistant Staphylococcus aureus infection in diabetic mice

The inhibitory effect of diallyl sulphide (DAS) and diallyl disulphide (DADS) against meticillin-resistant Staphylococcus aureus (MRSA) infection in diabetic mice was studied. The influence of these agents on the plasma levels of fibronectin, C-reactive protein (CRP), fibrinogen, interleukin (IL)-6 and tumour necrosis factor-alpha (TNF-alpha), and on the activity of plasminogen activator inhibitor-1 (PAI-1), antithrombin III (AT-III) and protein C, in MRSA-infected diabetic mice was examined. To induce diabetes, mice were treated intraperitoneally with streptozotocin for 5 consecutive days. Ten clinical MRSA isolates obtained from infected patients were used in this study. Diabetic mice were infected by injecting 200 microl MRSA/PBS suspension containing 10(7) c.f.u. via the tail vein. At day 4 post-infection, 200 microl DAS or DADS was administrated twice orally with an interval of 12 h. Eight hours after each administration, the blood and organs of mice were collected. Results showed that DAS and DADS significantly decreased MRSA viability in the kidney (P<0.05), with administration of each agent twice showing a greater inhibitory effect than when given once (P<0.05). MRSA infection in diabetic mice significantly elevated the plasma levels of IL-6 and TNF-alpha (P<0.05). DAS or DADS given once did not affect the plasma levels of IL-6 and TNF-alpha (P>0.05); however, DAS or DADS given twice significantly decreased the plasma levels of both IL-6 and TNF-alpha (P<0.05). DAS and DADS treatments also significantly reduced the plasma levels of CRP, fibronectin and fibrinogen (P<0.05). DAS or DADS treatment did not affect PAI-1 activity (P>0.05), but DAS or DADS given twice significantly increased AT-III activity (P<0.05). DADS given twice elevated protein C activity (P<0.05). MRSA infection significantly increased malondialdehyde levels in the kidney and spleen (P<0.05), and these levels were significantly decreased by treatment with DAS or DADS (P<0.05). These data suggest that DAS and DADS could provide multiple protective functions against MRSA infection in diabetic mice.

Anti-MRSA agents: under investigation, in the exploratory phase and clinically available

Staphylococcal infections are difficult to treat due to the rapid emergence of methicillin-resistant staphylococci and, unfortunately, vancomycin-intermediate or -resistant staphylococci. Numerous alternative treatments are urgently required. In this special report, intensive research of new molecules is highlighted--in known antibacterial families and new medicinal chemical entities.

In vitro and in vivo antibacterial activities of SM-216601, a new broad-spectrum parenteral carbapenem

SM-216601 is a novel parenteral 1beta-methylcarbapenem. In agar dilution susceptibility testing, the MIC of SM-216601 for 90% of the methicillin-resistant Staphylococcus aureus (MRSA) strains tested (MIC(90)) was 2 microg/ml, which was comparable to those of vancomycin and linezolid. SM-216601 was also very potent against Enterococcus faecium, including vancomycin-resistant strains (MIC(90) = 8 microg/ml). SM-216601 exhibited potent activity against penicillin-resistant Streptococcus pneumoniae, ampicillin-resistant Haemophilus influenzae, Moraxella catarrhalis, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, with MIC(90)s of less than 0.5 microg/ml, and intermediate activity against Citrobacter freundii, Enterobacter cloacae, Serratia marcescens, and Pseudomonas aeruginosa. The therapeutic efficacy of SM-216601 against experimentally induced infections in mice caused by S. aureus, E. faecium, E. coli, and P. aeruginosa reflected its in vitro activity and plasma level. Thus, SM-216601 is a promising candidate for nosocomial bacterial infections caused by a wide range of gram-positive and gram-negative bacteria, including multiresistant pathogens.

Cephalosporins in clinical development

Bacterial resistance to established classes of antibiotics in clinical use is continuing to increase, making the need for new agents that can be used to treat the newly multi-drug resistant organisms steadily more urgent. Cephalosporins have been a successful group of antibiotics since they were first introduced to combat drug-resistant organisms, including staphylococci. The history of cephalosporins has emphasised an improvement of their stability towards beta-lactamases, thus expanding their spectrum of activity against important Gram-negative pathogens. New cephalosporins that have potent activity against multi-resistant Gram-positive bacteria, including methicillin-resistant staphylococci and penicillin-resistant pneumococci have recently entered clinical development. At least two of these, BAL-5788 and S-3578, also have Gram-negative activity, which is comparable to that of the third-and fourth-generation cephalosporins, making them broad-spectrum agents that could be used in hospital infections where methicillin-resistant staphylococci is likely to be present.

Novel anti-staphylococcal targets and compounds

Many antimicrobial drugs have become less effective at combating infectious diseases, and experts in the field are concerned about the possibility of a 'post-antibiotic era' for some clinically important pathogens, particularly staphylococci. In our hospitals, nosocomial infections due to vancomycin-resistant enterococci have emerged, and there are concerns that the same resistance pattern may evolve in methicillin-resistant Staphylococcus aureus (MRSA). Examples from three main areas addressed to prevent this scenario are discussed: (i) screening of isolated biochemical targets and intact bacteria using high-throughput screening technologies, (ii) modifying existing compound classes like quinolones and glycopeptides to create more powerful compounds overcoming pathogen resistance and (iii) introduction of completely new classes of antibiotics.

In vitro activities of a novel cephalosporin, CB-181963 (CAB-175), against methicillin-susceptible or -resistant Staphylococcus aureus and glycopeptide-intermediate susceptible staphylococci

We examined the activity of CB-181963, a novel cephalosporin, against methicillin-resistant Staphylococcus aureus (MRSA) (n = 200), methicillin-susceptible S. aureus (MSSA) (n = 50), glycopeptide-intermediate Staphylococcus species (GISS) (n = 47), and VRSA (n = 2) isolates. CB-181963 exhibited MIC profiles similar to those of linezolid against MRSA and GISS; however, activity against MSSA was similar to that of vancomycin. Time-kill study results of investigations of activity against MRSA, MSSA, and GISS at 24 h were as follows: CB-181963 activity = vancomycin activity > linezolid activity (P < 0.001); CB-181963 = quinupristin-dalfopristin = vancomycin > linezolid (P < 0.05); CB-181963 > linezolid (P = 0.003); and CB-181963 = quinupristin-dalfopristin = vancomycin. CB-181963 may provide an alternative treatment for multidrug-resistant staphylococci.

Effects of tungstosilicate on strains of methicillin-resistant Staphylococcus aureus with unique resistant mechanisms

In a previous study, it was found that polyoxotungstates such as undecatungstosilicate (SiW11) greatly sensitized strains of methicillin-resistant Staphylococcus aureus (MRSA) to beta-lactams. In this report, the effects of SiW11 on several MRSA strains with unique resistant mechanisms were studied. SiW11 was still effective to MRSA mutants with higher beta-lactam resistance due to reduced cell-lytic activity. Since the antimicrobial effect of TOC-39 (a cephem antibiotic with strong affinity to penicillin-binding protein (PBP) 2') was not strongly enhanced in any case, it was confirmed that the sensitizing effect of SiW11 is due to reduced expression of PBP2'. However, the sensitizing effect of SiW11 was relatively weak in MRSA strains with lowered susceptibility to glycopeptide antibiotics. A certain resistant mechanism other than the mecA-PBP2' system worked in such a strain. Interestingly, an MRSA mutant with the Eagle-type resistance was dramatically sensitized. This result suggests that SiW11 has another site of action besides reducing the expression of PBP2'.

CP6679, a new injectable cephalosporin with broad spectrum and potent activities against methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa

The antibacterial activities of CP6679, a new injectable cephalosporin with a broad antibacterial spectrum, were compared with those of other cephalosporins. CP6679 had stronger in-vitro activity than ceftazidime and cefpirome against methicillin-resistant Staphylococcus aureus(MRSA), methicillin-resistant coagulase-negative staphylococci, and Pseudomonas aeruginosa. Its activity against MRSA was eight times stronger than that of cefpirome, and it showed high binding affinity for penicillin-binding protein 2' of MRSA. Furthermore, the antibacterial activity of CP6679 against ceftazidime-resistant and imipenem-resistant P. aeruginosawas eight times stronger than that of ceftazidime and four times stronger than that of imipenem. In addition to its in-vitro activities, CP6679 showed the highest efficacy among all cephalosporins tested in murine models of systemic infection induced by MRSA or P. aeruginosa. It was more effective than vancomycin and cefpirome against respiratory tract infections induced by MRSA in mice.

In vitro activity of cephalosporin RWJ-54428 (MC-02479) against multidrug-resistant gram-positive cocci

RWJ-54428 (MC-02479) is a novel cephalosporin that binds to penicillin-binding protein (PBP) PBP 2' (PBP 2a) of methicillin-resistant staphylococci. Its in vitro activity was assessed against 472 gram-positive cocci, largely selected as epidemiologically unrelated isolates with multidrug resistance. The MIC at which 50% of isolates are inhibited (MIC(50)) and MIC(90) of RWJ-54428 for methicillin-resistant Staphylococcus aureus (MRSA) were 1 and 2 microg/ml, respectively, whereas they were 0.5 and 0.5 microg/ml, respectively, for methicillin-susceptible S. aureus. The MIC(50) and MIC(90) were 1 and 4 microg/ml, respectively, for methicillin-resistant coagulase-negative staphylococci (MRCoNS), whereas they were 0.25 and 1 microg/ml, respectively, for methicillin-susceptible isolates. The highest MICs for MRSA and MRCoNS isolates were 2 and 4 microg/ml, respectively. The MIC(50) and MIC(90) of RWJ-54428 for Enterococcus faecalis were 0.5 and 1 microg/ml, respectively, but they were 4 and 8 microg/ml, respectively, for Enterococcus faecium. For penicillin-susceptible, -intermediate, and -resistant pneumococci, the MIC(90)s of RWJ-54428 were 0.03, 0.25, and 0.5 microg/ml, respectively, with the highest MIC for a pneumococcus being 1 microg/ml, recorded for a strain for which penicillin and cefotaxime MICs were 8 and 4 microg/ml. MICs for Lancefield group A, B, C, and G streptococci were < or =0.008 microg/ml; those for viridans group streptococci, including isolates not susceptible to penicillin, were from 0.015 to 0.5 microg/ml. RWJ-54428 did not select resistant mutants of MRSA or enterococci in challenge experiments and has the potential to be useful for the treatment of infections caused by gram-positive cocci.

In vitro activities of novel trans-3,5-disubstituted pyrrolidinylthio-1beta-methylcarbapenems with potent activities against methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa

The in vitro activities of the novel 1beta-methylcarbapenems J-111, 225, J-114,870, and J-114,871, which have a structurally unique side chain that consists of a trans-3,5-disubstituted 5-arylpyrrolidin-3-ylthio moiety at the C-2 position, were compared with those of reference antibiotics. Among isolates of both methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRCoNS), 90% were inhibited by J-111,347 (prototype), J-111,225, J-114,870, and J-114,871 at concentrations of 2, 4, 4, and 4 microgram/ml (MICs at which 90% of isolates are inhibited [MIC(90)s]), respectively, indicating that these agents were 32- to 64-fold more potent than imipenem, which has an MIC(90) of 128 microgram/ml. Although these drugs were less active in vitro than vancomycin, which had MIC(90)s of 1 and 2 microgram/ml for MRSA and MRCoNS, respectively, the new carbapenems displayed better killing kinetics than vancomycin. The potent anti-MRSA activity was ascribed to the excellent affinities of the new carbapenems for penicillin-binding protein 2a of MRSA. Since the new carbapenems also exhibited good activity against gram-positive and -negative bacteria including clinically important pathogens such as penicillin-resistant Streptococcus pneumoniae, Haemophilus influenzae, members of the family Enterobacteriaceae, Pseudomonas aeruginosa, and Clostridium difficile, as well as MRSA, the novel carbapenems are worthy of further evaluation.

Vancomycin resistance in staphylococci

Recent emergence of vancomycin resistance in methicillin-resistant Staphylococcus aureus (VRSA) has posed a new threat to hospital infection control and antibiotic chemotherapy. Relatively low-level resistance of VRSA compared to that of vancomycin-resistant enterococci (VRE), and prevalence of S. aureus clinical strains heterogeneously resistant to vancomycin (hetero-VRSA), challenge the value of routine antibiotic susceptibility tests as a tool for the prediction of clinical efficacy of vancomycin therapy. This review summarizes the history of emergence of glycopeptide resistance in staphylococci and considers the mechanism of resistance in these organisms.

Therapeutic efficacy of BO-3482, a novel dithiocarbamate carbapenem, in mice infected with methicillin-resistant Staphylococcus aureus

The in vivo activity of BO-3482, which has a dithiocarbamate chain at the C-2 position of 1beta-methyl-carbapenem, was compared with those of vancomycin and imipenem in murine models of septicemia and thigh infection with methicillin-resistant Staphylococcus aureus (MRSA). Because BO-3482 was more susceptible than imipenem to renal dehydropeptidase I in a kinetic study of hydrolysis by this renal enzyme, the therapeutic efficacy of BO-3482 was determined during coadministration with cilastatin. In the septicemia models, which involved two homogeneous MRSA strains and one heterogeneous MRSA strain, the 50% effective doses were, respectively, 4.80, 6.06, and 0.46 mg/kg of body weight for BO-3482; 5.56, 2.15, and 1.79 mg/kg for vancomycin; and >200, >200, and 15.9 mg/kg for imipenem. BO-3482 was also as effective as vancomycin in an MRSA septicemia model with mice with cyclophosphamide-induced immunosuppression. In the thigh infection model with a homogeneous MRSA strain, the bacterial counts in tissues treated with BO-3482-cilastatin were significantly reduced in a dose-dependent manner compared with the counts in those treated with vancomycin and imipenem-cilastatin (P < 0.001). These results indicate that BO-3482-cilastatin is as effective as vancomycin in murine systemic infections and is more bactericidal than vancomycin in local-tissue infections. The potent in vivo activity of BO-3482-cilastatin against such MRSA infections can be ascribed to the good in vitro anti-MRSA activity and improved pharmacokinetics in mice when BO-3482 is combined with cilastatin and to the bactericidal nature of the carbapenem.

Methicillin resistance in staphylococci: molecular and biochemical basis and clinical implications

Methicillin resistance in staphylococci is determined by mec, composed of 50 kb or more of DNA found only in methicillin-resistant strains. mec contains mecA, the gene for penicillin-binding protein 2a (PBP 2a); mecI and mecR1, regulatory genes controlling mecA expression; and numerous other elements and resistance determinants. A distinctive feature of methicillin resistance is its heterogeneous expression. Borderline resistance, a low-level type of resistance to methicillin exhibited by strains lacking mecA, is associated with modifications in native PBPs, beta-lactamase hyperproduction, or possibly a methicillinase. The resistance phenotype is influenced by numerous factors, including mec and beta-lactamase (bla) regulatory elements, fem factors, and yet to be identified chromosomal loci. The heterogeneous nature of methicillin resistance confounds susceptibility testing. Methodologies based on the detection of mecA are the most accurate. Vancomycin is the drug of choice for treatment of infection caused by methicillin-resistant strains. PBP 2a confers cross-resistance to most currently available beta-lactam antibiotics. Investigational agents that bind PBP 2a at low concentrations appear promising but have not been tested in humans. Alternatives to vancomycin are few due to the multiple drug resistances typical of methicillin-resistant staphylococci.

Cefpirome. A review of its antibacterial activity, pharmacokinetic properties and clinical efficacy in the treatment of severe nosocomial infections and febrile neutropenia

Cefpirome is an injectable extended-spectrum or 'fourth generation' cephalosporin. Its antibacterial activity encompasses many of the pathogens involved in hospital-acquired infections such as Enterobacteriaceae, methicillin-susceptible Staphylococcus aureus, coagulase-negative staphylococci and viridans group streptococci. Cefpirome also has in vitro activity against Streptococcus pneumoniae regardless of penicillin susceptibility. It is stable against most plasmid- and chromosome-mediated beta-lactamases, with the exception of the extended-spectrum plasmid-mediated SHV enzymes. Intravenous cefpirome 2g twice daily has shown clinical efficacy comparable to that of ceftazidime 2g 3 times daily in the treatment of hospitalised patients with moderate to severe infections. Clinical response and bacteriological eradication rates were similar in patients with severe pneumonia or septicaemia treated with either cefpirome or ceftazidime. Cefpirome appeared more effective than ceftazidime in the eradication of bacteria in patients with febrile neutropenia in 1 study; however, clinical response rates were similar in the 2 treatment groups. The tolerability of cefpirome appears similar to that of ceftazidime and other third generation cephalosporins, diarrhoea being the most frequently observed event. Thus, cefpirome is likely to be a valuable extended-spectrum agent for the treatment of severe infections. Cefpirome offers improved coverage against some Gram-positive pathogens and Enterobacteriaceae producing class I beta-lactamases compared with the third generation cephalosporins, although this has yet to be demonstrated in clinical trials.

Novelties in the field of parenteral cephem antibacterials since 1993

There is still considerable interest in cephem antibacterial agents. In fact, there are a significant number of patents submitted for this antibacterial class. All the new cephem derivatives, independent of which group they belong to (III to V), possess a 2-amino-5-thiazolyl or a 5-amino-2-thiadiazolyl ring with an oxime group (at position 7 of the cephem nucleus). At position 3, they have a C-3' quaternary ammonium moiety. Research has focused on the following structural modifications: the nature of the oxime residues and the charged azolium heterocycle, and the addition of the vinylogous chain. The aim of researchers is to increase the overall activity of these compounds against Gram-negative bacilli, including against isolates producing type 1 beta-lactamases or extended spectrum beta-lactamases (Enterobacteriaceae). Non-fermentative Gram-negative bacilli are now included in the first screening process, in addition to Pseudomonas aeruginosa. Extensive research is ongoing with the aim of solving the MRSA problem. New promising entities have been reported.

In vitro activity of the trinem sanfetrinem (GV104326) against gram-positive organisms

The in vitro activity of the trinem sanfetrinem (formerly GV104326) (GV) was compared with that of vancomycin, ampicillin, and/or nafcillin against 287 gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and multiresistant enterococci, by the agar and microbroth dilution methods. GV demonstrated 2 to 16 times more activity than ampicillin and nafcillin against the majority of these organisms. The MIC range of GV was 16 to 64 micrograms/ml for 19 Enterococcus faecium strains that were highly resistant to ampicillin (ampicillin MIC range, 64 to 512 micrograms/ml) and vancomycin resistant and 0.25 to 32 micrograms/ml for resistant Rhodococcus spp. Similar activities (+/-1 dilution) were observed by either the agar or the broth microdilution method. GV demonstrated bactericidal activity against a beta-lactamase-producing Enterococcus faecalis strain and against two methicillin-susceptible Staphylococcus aureus strains in 10(5)-CFU/ml inocula. Synergy between GV and gentamicin was observed against an E. faecalis strain that lacked high-level gentamicin resistance. The activity of GV suggests this compound warrants further study.

Synthesis and structure-activity relationship of (lactamylvinyl)cephalosporins exhibiting activity against staphylococci, pneumococci, and enterococci

The synthesis and structure-activity relationships of a new class of vinylcephalosporins substituted with a lactamyl residue are described. These compounds show excellent activity against enterococci and retain the broad spectrum activity of third-generation cephalosporins such as ceftriaxone.