Isolation, characterization and genomic analysis of vB‐AhyM‐AP1, a lytic bacteriophage infectingAeromonas hydrophila

Abstract

Aims: Aeromonas hydrophila is a zoonotic pathogen displaying resistance to multiple antibiotics. Here, we aim to develop a candidate biocontrol agent against A. hydrophila. Methods and Results: In this study, we isolated and characterized the phage vB-AhyM-AP1 from sewage. It showed lytic activity against A. hydrophila strains. One-step growth curve revealed that the latent period lasted for 40 min. The burst size of one lytic cycle was 1413 PFU per infected cell. Temperature stability studies showed that the phage vB-AhyM-AP1 was active over temperatures ranging from 4 to 45°C for 1 h. pH stability studies indicated that the phage remained active within a pH range of 5-10 after 24 h of incubation. Stability tests in salt solutions showed that the phage was stable at salinities ranging from 0Á1 to 2%. The phage also showed stabilities in organic solvents when incubated for 10 min. The Illumina Hiseq sequencing of its genome indicated that the phage vB-AhyM-AP1was a jumbo phage with a genome size of 2, 54 490 bp and GC content of 40Á3%. The phylogenetic analysis of the terminase large subunit and major capsid protein indicated that the phage closely clustered with other Tevenvirinae phages. The genome encoded 455 ORFs and 22 tRNAs. The phage resulted in a reduction of 0Á8 log units of viable A. hydrophila cells in biofilms grown on PVC coupons maintained in a low nutrient medium for 10 days. Conclusions: The phage showed lytic activity against planktonic and biofilm cells of A. hydrophila. Genome-based prediction showed it to be a strictly lytic phage without any virulence or antibiotic resistance genes indicating safety for environmental and clinical applications. Significance and Impact of the Study: The multidrug-resistant strains of A. hydrophila pose a significant health risk to both cultured fishes and consumers leaving few options for treatment. Phage vB-AhyM-AP1 may be used as a candidate biocontrol agent against A. hydrophila strains.

Isolation and characterization of bacteriophage Ib_pec2 against shigatoxigenic Escherichia coli

“…Ib_pec2 exhibited a burst size of 893 pfu/ml. Similar large burst sizes were also reported in podoviridae phages [22], myoviridae phages [23], and Autographiviridae [24]. The results of one-step growth curve depend upon the media, incubation conditions, the number of receptors in bacteria, and so on [23].…”

Bacteriophages in the Control of Aeromonas sp. in Aquaculture Systems: An Integrative View

“…The majority of marine phages are highly host-specific [ 232 , 233 , 234 ], and about 73% lyse only the original host bacterium [ 234 ]. Although phages with a broad host range are hard to find, some examples of virulent phages have shown some promise for therapeutic use in aquaculture, infecting strains of several bacterial species [ 180 , 181 , 217 , 235 , 236 ] and genera [ 92 , 237 ] ( Table S2 ). Liu et al (2020) reported that the isolated phages had a relatively broad infectivity spectrum against A. hydrophila and showed the potential to infect A. veronii , A. caviae and A. bestiarum [ 236 ].…”

“…A. hydrophila phages vB-AhyM-AP1 and pAh-1 presented high burst sizes (1413 and 608 PFU/host cell, respectively); however, the latent period of phage vB-AhyM-AP1 (40 min) is higher than that of phage pAh-1 (15 min) [ 211 , 235 ] ( Table S2 ). Phage AhyVDH1 infected A. hydrophila producing 274 PFU/host cell [ 214 ], TG25P (79 ± 11.9 PFU/host cell) [ 212 ]; Akh-2 (139 PFU/host cell) [ 149 ] and AHP-1 (97 PFU/host cell) [ 181 ].…”

“…Generally, the phage lytic activity decreases in pH values ranging between 10 < pH < 5, with optimum pH conditions around neutrality (pH of 6–8) [ 196 , 260 ]. Several phages isolated for A. salmonicida and A. hydrophila control and presented in Table S2 can tolerate a wide range of pH values, namely phage AS-D (pH 5.5–8) [ 150 ], phages AS-yj (pH 5–10) and AS-gz (pH 4–11) [ 217 ], phages CT45P and TG25P (pH 5–9) [ 261 ], phage ASP-1 (pH 4–11) [ 180 ], phage Akh-2 (pH 7–9) [ 149 ], phage AhyVDH1 (pH 5–10) [ 214 ], phage PVN02 (pH 7–9) [ 148 ], phage pAh6.2T (pH 7–11) [ 94 ], phage AHP-1 (pH 7–10) [ 181 ], phage vB-AhyM-AP1 (pH 5–10) [ 235 ], phage pAh-1 (pH 5–11) [ 211 ], phages N21 (pH 5–11), W3 (pH 4–10), G65 (pH 4–11), Y71 (pH5–10) and Y81 (pH 4–10) [ 236 ], and phages AhFM4 and AhFM5 (pH 5–8) [ 231 ].…”

“…A. salmonicida phage AS-D remained stable at salinity concentrations of 15%, 20% and 35% for 49 days, after which a decrease of about three orders of magnitude until the 107th day occurred [ 150 ]. Phages isolated to control A. hydrophila can tolerate a wide range of salinity concentrations, namely phage ASP-1 (0.1–3.5%) [ 180 ], phage vB-AhyM-AP1 (0.1–2.0%) [ 235 ] and phages AhFM4 and AhFM5 (0.5–2.0%) [ 231 ]. Phage pAh6.2TG was relatively stable at a wide range of salinity concentrations (0–40%) for 24 h [ 94 ] ( Table S2 ).…”