novobiocin and Enterobacteriaceae-Infections

The efficacy of a novel attenuated Edwardsiella ictaluri vaccine (B-50348) was determined in channel catfish (Ictalurus punctatus) by bath immersion and intraperitoneal (IP) injection. The vaccine was developed from a virulent strain of E. ictaluri (AL93-58) through selection for novobiocin resistance. When channel catfish (average weight 10 g) were IP injected with 4.2 × 10⁶ colony-forming units (CFU) of the attenuated vaccine B-50348, no fish died. However, when the same age and size matched group of the catfish were IP injected with a lesser amount (2.4 × 10⁶ CFU/fish) of modified live RE-33 vaccine or the AL93-58 virulent strain (2.5 × 10⁶ CFU/fish) of E. ictaluri, 65% and 95% fish died, respectively. When channel catfish were challenged with AL93-58, relative percent survival values of vaccinated fish were all greater than 90% at 22, 32, and 63 days post B-50348 vaccination through intraperitoneal injection. By bath immersion, at 37 and 57 days post vaccination of B-50348, relative percent survival values were both 100% when fish were challenged by virulent E. ictaluri AL93-58. Our results suggest that B-50348 could be used as a novel safe and efficacious vaccine against ESC in channel catfish.

Topics: Animals; Bacterial Vaccines; Drug Resistance, Bacterial; Edwardsiella ictaluri; Enterobacteriaceae Infections; Enzyme-Linked Immunosorbent Assay; Fish Diseases; Ictaluridae; Novobiocin; Plasmids; Vaccines, Attenuated

Enterobacter cloacae is an emerging clinical pathogen that may be responsible for nosocomial infections. Management of these infections is often difficult, owing to the high frequency of strains that are resistant to disinfectants and antimicrobial agents in the clinical setting. Multidrug efflux pumps, especially those belonging to the resistance-nodulation-division family, play a major role as a mechanism of antimicrobial resistance in gram-negative pathogens. In the present study, we cloned and sequenced the genes encoding an AcrAcB-TolC-like efflux pump from an E. cloacae clinical isolate (isolate EcDC64) showing a broad antibiotic resistance profile. Sequence analysis showed that the acrR, acrA, acrB, and tolC genes encode proteins that display 79.8%, 84%, 88%, and 82% amino acid identities with the respective homologues of Enterobacter aerogenes and are arranged in a similar pattern. Deletion of the acrA gene to yield an AcrA-deficient EcDC64 mutant (EcDeltaacrA) showed the involvement of AcrAB-TolC in multidrug resistance in E. cloacae. However, experiments with an efflux pump inhibitor suggested that additional efflux systems also play a role in antibiotic resistance. Investigation of several unrelated isolates of E. cloacae by PCR analysis revealed that the AcrAB system is apparently ubiquitous in this species.

Topics: Bacterial Proteins; Base Sequence; beta-Lactamases; Carrier Proteins; Cloning, Molecular; DNA, Bacterial; Drug Resistance, Bacterial; Enterobacter cloacae; Enterobacteriaceae Infections; Genes, MDR; Genetic Vectors; Humans; Microbial Sensitivity Tests; Molecular Sequence Data; Plasmids; Porins

Topics: Ampicillin; Anti-Bacterial Agents; Carbenicillin; Chloramphenicol; Colistin; Drug Combinations; Drug Interactions; Drug Synergism; Enterobacteriaceae Infections; Erythromycin; Gentamicins; Glycosides; Humans; Hydrogen-Ion Concentration; Infections; Neoplasms; Novobiocin; Penicillins; Polymyxins; Streptomycin; Sulfonamides; Tetracycline; Trimethoprim