?Fig.1.1. nonproductive complex with template primer DNA (19). Open in a separate windows FIG. 1 Constructions of the four AUs used in this study: HB-EMAU, HB-IMAU, MB-EMAU, and MB-IMAU. Structure-activity associations of these AUs have been explained previously (18, 19). The prototypic AUs, which have either poor antimicrobial activities or unacceptably low aqueous solubility (3C6, 13, 17), have now been substituted in their N3 positions and aryl rings to produce a series of more potent and more soluble molecules (13, 16, 19). The latest generation of these soluble forms (19) includes the N3-hydroxybutyl (HB) and N3-methoxybutyl (MB) derivatives of 6-[3-ethyl-4-methylanilino]uracil (EMAU) and 6-[3-iodo-4-methylanilino]uracil (IMAU) demonstrated in Fig. ?Fig.1.1. In this study, we describe the in vitro activities of HB-IMAU, HB-EMAU, MB-IMAU, and MB-EMAU against staphylococci and enterococci, bacteria that are pathogenic in humans and are hard to treat with currently available and investigational antimicrobial providers. (This work was presented in part in the 39th Interscience Conference on Antimicrobial Providers and Chemotherapy, San Francisco, Calif., 1999 [J. S. Daly, T. Giehl, N. C. Brown, C. Zhi, G. E. Wright, and R. T. Ellison III, Abstr. 39th Intersci. Conf. Antimicrob. Providers Chemother., abstr. 1808, 1999].) Materials and BAY885 methods. Bacterial strains used in this study were unique medical isolates collected in the medical microbiology Rabbit Polyclonal to GPRC5C laboratory at UMass Memorial Health Care, Worcester, Mass. ATCC 29212 (isolates; 16, 16, 16, and 16 g/ml for oxacillin-susceptible isolates; 32, 16, 16, and 8 g/ml for coagulase-negativeCoxacillin-susceptible staphylococci; 16, 8, 8, and 8 g/ml for coagulase-negativeCoxacillin-resistant staphylococci; 16, 8, 8, and 16 g/ml for isolates; 16, 16, 16, and 16 g/ml for vancomycin-susceptible isolates; and 16, 16, 16, and 8 g/ml for vancomycin-resistant isolates. The novel AUs inhibited most strains at a concentration of 8 to 16 g/ml, with there becoming no difference in the levels of activity against the oxacillin-resistant staphylococci or the vancomycin-resistant enterococci compared to those against the vulnerable strains. There was no cross-resistance between the AUs and additional inhibitors of DNA or RNA synthesis. The MICs for ATCC 25923 were 8 to 32 g/ml, and the MBCs were identical to the MICs for this strain in the instances of all four compounds. For the enterococcal control strain ATCC 29212 MICs were 4 to 8 g/ml and MBCs were two to four occasions higher. The AUs were bactericidal to most of the medical strains of staphylococci at one to two occasions their MICs and to the enterococci at one to four occasions their MICs. Time-kill assays, demonstrated in Fig. ?Fig.22 confirmed the bactericidal activities of HB-EMAU and MB-IMAU. TABLE 1 Activities of DNA pol III inhibitors and additional antimicrobial providers against staphylococci and?enterococci strain (SA 82820) (A), BAY885 a vancomycin-susceptible (VSE) strain (EN 512) (B), and a vancomycin-resistant (VRE) strain (EN 513) (C). MRSA, methicillin-resistant species and BAY885 mycoplasmas, species that contain the same target DNA pol III, but further study is needed (19). They have no activity against the mouse peritonitis model, BAY885 with 10 mg/kg of body weight providing protection equal to that of vancomycin at 20 mg/kg (19). This study is the 1st to fine detail the in vitro activities of members of this class of antimicrobial providers against medical isolates in comparison to those of available providers. There was no cross-resistance between these AUs and the fluoroquinolones or rifampin, additional inhibitors of DNA and RNA synthesis. Similarly, no cross-resistance was recognized with providers that exert their antibacterial action at the level of cell wall or protein synthesis. The AUs were bactericidal at one to four occasions their MICs for most strains. The BAY885 results of this study confirm the general hypothesis (14) that bacterial DNA pol III is definitely a valid target for antimicrobial drug development, including the development of providers effective against clinically relevant organisms resistant to standard antimicrobials. More specifically, our results demonstrate the strong potential of the AUs as model antibacterial providers. Given their potential, fresh forms of these AUs are under development with the objective of enhancing their aqueous solubility and in vitro potency, so that their security and effectiveness can be assessed in vivo against infections with relevant pathogens. Acknowledgments We say thanks to Maureen Jankins, Brenda Torres, and Rosemary Dodge in the Clinical Microbiology Lab, UMass Memorial Health Care, for help with preparation of the MIC panels and collection of the bacterial strains. We say thanks to Pharmacia Upjohn and Rh?ne-Poulenc Rorer for providing antimicrobial research powders. This work was supported in part by STTR phase I give AI41260 from your National Institutes of Health. Recommendations 1. Barnes M H,.