A genomics‐based approach was used to identify the entire gene complement of putative two‐component signal transduction systems (TCSTSs) in Streptococcus pneumoniae. A total of 14 open reading frames (ORFs) were identified as putative response regulators, 13 of which were adjacent to genes encoding probable histidine kinases. Both the histidine kinase and response regulator proteins were categorized into subfamilies on the basis of phylogeny. Through a systematic programme of mutagenesis, the importance of each novel TCSTS was determined with respect to viability and pathogenicity. One TCSTS was identified that was essential for the growth of S. pneumoniaeThis locus was highly homologous to the yycFG gene pair encoding the essential response regulator/histidine kinase proteins identified in Bacillus subtilis and Staphylococcus aureus. Separate deletions of eight other loci led in each case to a dramatic attenuation of growth in a mouse respiratory tract infection model, suggesting that these signal transduction systems are important for the in vivo adaptation and pathogenesis of S. pneumoniae. The identification of conserved TCSTSs important for both pathogenicity and viability in a Gram‐positive pathogen highlights the potential of two‐component signal transduction as a multicomponent target for antibacterial drug discovery.

Pexiganan, a 22-amino-acid antimicrobial peptide, is an analog of the magainin peptides isolated from the skin of the African clawed frog. Pexiganan exhibited in vitro broad-spectrum antibacterial activity when it was tested against 3,109 clinical isolates of gram-positive and gram-negative, anaerobic and aerobic bacteria. The pexiganan MIC at which 90% of isolates are inhibited (MIC90) was 32 μg/ml or less forStaphylococcus spp., Streptococcus spp.,Enterococcus faecium, Corynebacterium spp.,Pseudomonas spp., Acinetobacter spp.,Stenotrophomonas spp., certain species of the familyEnterobacteriaceae, Bacteroides spp.,Peptostreptococcus spp., and Propionibacteriumspp. Comparison of the MICs and minimum bactericidal concentrations (MBCs) of pexiganan for 143 isolates representing 32 species demonstrated that for 92% of the isolates tested, MBCs were the same or within 1 twofold difference of the MICs, consistent with a bactericidal mechanism of action. Killing curve analysis showed that pexiganan killed Pseudomonas aeruginosa rapidly, with 106 organisms/ml eliminated within 20 min of treatment with 16 μg of pexiganan per ml. No evidence of cross-resistance to a number of other antibiotic classes was observed, as determined by the equivalence of the MIC50s and the MIC90s of pexiganan for strains resistant to oxacillin, cefazolin, cefoxitin, imipenem, ofloxacin, ciprofloxacin, gentamicin, and clindamicin versus those for strains susceptible to these antimicrobial agents. Attempts to generate resistance in several bacterial species through repeated passage with subinhibitory concentrations of pexiganan were unsuccessful. In conclusion, pexiganan exhibits properties in vitro which make it an attractive candidate for development as a topical antimicrobial agent.

PPI-0903M is a novel N-phosphono-type cephalosporin active against oxacillin-resistant staphylococci and many other gram-positive organisms. This study evaluated the in vitro activity and spectrum of PPI-0903M against 1,478 recent clinical isolates collected from 80 medical centers (22 countries). PPI-0903M demonstrated broader in vitro activity against gram-positive bacteria, particularly against multidrug-resistant staphylococci and streptococci of current clinical concern, than currently available extended-spectrum cephalosporins while maintaining similar activity against gram-negative pathogens.

Ceftaroline, the bioactive metabolite of ceftaroline fosamil (previously PPI-0903, TAK-599), is a broadspectrum cephalosporin with potent in vitro activity against multidrug-resistant gram-positive aerobic pathogens, including methicillin-resistant Staphylococcus aureus. A randomized, observer-blinded study to evaluate the safety and efficacy of ceftaroline versus standard therapy in treating complicated skin and skin structure infections (cSSSI) was performed. Adults with cSSSI, including at least one systemic marker of inflammation, were randomized (2:1) to receive intravenous (i.v.) ceftaroline (600 mg every 12 h) or i.v. vancomycin (1 g every 12 h) with or without adjunctive i.v. aztreonam (1 g every 8 h) for 7 to 14 days. The primary outcome measure was the clinical cure rate at a test-of-cure (TOC) visit 8 to 14 days after treatment. Secondary outcomes included the microbiological success rate (eradication or presumed eradication) at TOC and the clinical relapse rate 21 to 28 days following treatment. Of 100 subjects enrolled, 88 were clinically evaluable; the clinical cure rate was 96.7% (59/61) for ceftaroline versus 88.9% (24/27) for standard therapy. Among the microbiologically evaluable subjects (i.e., clinically evaluable and having had at least one susceptible pathogen isolated at baseline), the microbiological success rate was 95.2% (40/42) for ceftaroline versus 85.7% (18/21) for standard therapy. Relapse occurred in one subject in each group (ceftaroline, 1.8%; standard therapy, 4.3%). Ceftaroline exhibited a very favorable safety and tolerability profile, consistent with that of marketed cephalosporins. Most adverse events from ceftaroline were mild and not related to treatment. Ceftaroline holds promise as a new therapy for treatment of cSSSI and other serious polymicrobial infections.

A large motility operon, referred to as the flgB operon, was identified, characterized, and mapped at 310 to 320 kb on the linear chromosome of the spirochete Borrelia burgdorferi. This is the first report that a The bacterial motility apparatus is a highly organized but complicated structure composed of the flagellar filament, the hook-basal body complex, membrane-associated energy-transducing components, and proteins involved in export (1, 49, 69). Most of the flagellar genes of Escherichia coli and Salmonella typhimurium (1, 49), Bacillus subtilis (3,9,22,51,52,56,73), and Caulobacter crescentus (4, 19, 69) have been identified and sequenced. More than 50 genes are involved in flagellar structure and assembly, motility, and chemotaxis. These genes are organized into clusters and constitute functional operons. For example, in E. coli there are four motility and chemotaxis clusters (regions I, II, IIIa, and IIIb) consisting of 15 operons (49). These operons together comprise a large flagellar regulon. In contrast, the organization of the B. subtilis motilitychemotaxis genes is quite different (3,9,17,22,51,56,73). Although these genes are not clustered into four regions as is found in E. coli, the orders of certain flagellar genes in B. subtilis and E. coli are similar. The genes in B. subtilis are arranged such that several small flagellar clusters are involved in the last stage of flagellar assembly (17, 51, 52). In addition, there is a large (26-kb) fla/che locus containing more than 30 structural, motility, and chemotaxis genes (9). The genes encoding the proteins for early flagellar assembly are concentrated within this operon. In C. crescentus (4,19), the flagellar regulon is composed of more than 10 small operons with a gene order different from those in S. typhimurium, E. coli, and B. subtilis.The morphological pathway of flagellar assembly has been studied in detail for E. coli and S. typhimurium (1, 49) and C. crescentus (4, 69). Flagellar synthesis is highly coordinated, involving a specific order of gene expression which is achieved by a tightly controlled transcriptional cascade (1,4,19,60). In E. coli and S. typhimurium, the class 1 master proteins FlhD and FlhC are regulated under catabolite repression by glucose (49). Expression of both proteins results in the activation of all seven class 2 operons encoding components of the hook-basal body complex, the export apparatus, and the flagellum-specific sigma factor 28 (FliA) (36,44,49). The majority of the products encoded by class 2 genes are essential for full expression of class 3 genes.28 is utilized to initiate transcription of the seven class 3 operons. The class 3 gene products include the hook-associated proteins, flagellin, the motor proteins (MotA and MotB), and chemotaxis proteins. All class 3 genes and many of the class 2 genes, including fliA itself, are transcribed from 28 -like promoter elements (36,44,49). In B. subtilis, the genes corresponding to the class 2 and class 3 genes, including those from the large fla/che operon, are tra...

This study evaluated the in vitro activity of ceftaroline, a novel cephalosporin with broad-spectrum activity against gram-negative and -positive pathogens, against 4,151 recent clinical isolates collected in the United States. Ceftaroline was very potent against bacteria found in community-and hospital-acquired infections, including methicillin-resistant Staphylococcus aureus, multidrug-resistant Streptococcus pneumoniae, and common Enterobacteriaceae spp.

Ceftaroline has impressive anti-MRSA and anti-pneumococcal activity. Slight lability to classical TEM and SHV beta-lactamases is exceptional for an oxyimino-cephalosporin, but was reversible with clavulanate, as was the greater resistance mediated by ESBLs. Resistance selection occurred with Enterobacteriaceae, not MRSA.

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