RESUMEN
Escherichia coli (E. coli) is one of the most common sources of infection in humans and animals. The emergence of E. coli which acquires resistance to various antibiotics has made treatment difficult. Bacteriophages can be considered promising agents to expand the options for the treatment of antibiotic-resistant bacteria. This study describes the isolation and characterization of Escherichia phage KIT06, which can infect E. coli resistant to the quinolone antibiotic nalidixic acid. Phage virions possess an icosahedral head that is 93 ± 8 nm in diameter and a contractile tail (116 ± 12 nm × 13 ± 5 nm). The phage was found to be stable under various thermal and pH conditions. A one-step growth curve showed that the latent time of the phage was 20 min, with a burst size of 28 particles per infected cell. Phage KIT06 infected 7 of 12 E. coli strains. It inhibited the growth of the host bacterium and nalidixic acid-resistant E. coli. The lipopolysaccharide and outer membrane proteins of E. coli, tsx and btuB, are phage receptors. Phage KIT06 is a new species of the genus Tequatrovirus with a genome of 167,059 bp consisting of 264 open reading frames (ORFs) that encode gene products related to morphogenesis, replication, regulation, and host lysis. The lack of genes encoding integrase or excisionase indicated that this phage was lytic. Thus, KIT06 could potentially be used to treat antibiotic-resistant E. coli using phage therapy. However, further studies are essential to understand its use in combination with other antimicrobial agents and its safe use in such applications.
RESUMEN
Vibrio parahaemolyticus is a bacterial pathogen in marine aquaculture systems and a major cause of food-borne illnesses worldwide. In the present study, Vibrio phage KIT05 was isolated from water collected from a shrimp farm in the Mekong Delta, Vietnam. It was characterized based on its morphology, growth curve, lytic properties, and genome sequence. Under the electron microscope, KIT05 particles had an icosahedral head with a diameter of 62.3 nm and a short tail of 24.1 nm. The one-step growth curve of KIT05 showed that its latency time was approximately 40 min and burst size was 18 plaque-forming units/cell. The genome of KIT05 comprises 50,628 bp with a GC content of 41.63%. It contains 60 open reading frames that are encoded within both strands and four tRNAs. The presence of direct terminal repeats of 130 bp at both ends of the KIT05 DNA was determined. According to phage morphology, genomic organization, and phylogeny analysis, Vibrio phage KIT05 was classified into the family Podoviridae. The genome annotation revealed that KIT05 had no virulent or lysogenic genes. This study may help identify a novel candidate for developing biocontrol agents for Vibrio parahaemolyticus.