Isolation, characterization and genomic analysis of vB-AhyM-AP1, a lytic bacteriophage infecting Aeromonas hydrophila

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 0·1 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 40·3%. 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 0·8 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.

Prevalence of adhesive genes among uropathogenic Escherichia coli strains isolated from patients with urinary tract infection in Mangalore

The study was carried out to detect the adhesive genes pap (pyelonephritis associated pili), sfa (S fimbrial adhesin) and afa (afimbrial adhesin) from Escherichia coli strains isolated in patients diagnosed with urinary tract infection (UTI). A total of 23% of the isolates were positive for pap, sfa and afa genes with a prevalence of 60.87% (14/23), 39.1% (9/23) and 39.1% (9/23), respectively. Prevalence of multiple adhesive genes was 8.7% (2/23) for pap and afa, 30.43% (7/23) for pap and sfa. Significant numbers of isolates were positive for Congo red binding (80%) and haemolysin production 60%. The prevalence of multiple adhesive genes indicate the potential to adhere and subsequently cause a systemic infection among UTI patients.

Presence of T3SS2β genes in trh⁺ Vibrio parahaemolyticus isolated from seafood harvested along Mangalore coast, India

Vibrio parahaemolyticus is a seafood-borne pathogen autochthonous to the marine and estuarine ecosystem, responsible for gastroenteritis when contaminated raw seafood is consumed. The pathogenicity has been associated with thermostable direct haemolysin (TDH) and TDH-related haemolysin (TRH). Of late, the presence of T3SS2α and T3SS2β gene clusters has been well documented in clinical isolates of Vibrio parahaemolyticus and known to play an essential role in pathogenesis. However, reports on the presence of T3SSβ genes in V. parahaemolyticus isolated from the seafood and/or environmental samples are scanty. In this study, we have identified and analysed the distribution of the T3SS2β genes in V. parahaemolyticus isolated from seafood harvested along southwest coast of India. Results showed that T3SS2β genes are solely associated with trh⁺ and tdh⁺ /trh⁺ strains of V. parahaemolyticus. Reverse transcriptase PCR (RT-PCR) showed that the T3SS2β genes identified in trh⁺ V. parahaemolyticus were transcriptionally active. To our knowledge, this study appears to be the first description on the presence of T3SS2β-positive V. parahaemolyticus isolated from seafood in India. The study of T3SS2 along with other virulence factors will help in better understanding of the risk of seafood-borne illness due to V. parahaemolyticus.

SIGNIFICANCE AND IMPACT OF THE STUDY

T3SSs (α or β) are the important virulence factors of Vibrio parahaemolyticus that contribute to their pathogenicity in humans. This study demonstrated the presence of T3SS2β genes in V. parahaemolyticus isolated from the seafood harvested along Mangalore coast. RT-PCR showed that the T3SS2β genes identified in seafood isolates of V. parahaemolyticus were found to be functional. To the best of our knowledge, this is the first description of T3SS2β genes in trh⁺ V. parahaemolyticus isolated from seafood in India. The presence of T3SS2 along with other virulence factors such as TDH and/or TRH highlights a potential health risk for seafood consumers.

Use of positive-negative deviant analyses to improve programme targeting and services: example from the TamilNadu Integrated Nutrition Project

This paper describes the characteristics of southern rural Indian children who grow best (positive deviants) and worst (negative deviants) as compared to median growers. A 100 each of positive and negative deviants and 120 median growers were selected after analysing the 12-month growth patterns (weight-for-age) of 2954 children enrolled in the TamilNadu Integrated Nutrition Project (TINP), a major health and nutrition intervention project covering nearly one million children in rural south India. The determinants of poor growth that have been left unaddressed by 6 years of TINP exposure are delineated to address the question of what more needs to be done. Further, the rationale for differential targeting of services to negative deviants and to median growers is discussed, as are the implications for programme evaluation. Data indicate that the next generation of projects targeted at the most needy (negative deviants) should address the issues of gender discrimination in childcare, of breastfeeding, of diarrhoeal disease, and of maternal empowerment. Such interventions will, however, not improve the growth of median growers in the direction of positive deviance. Instead, programmes targeted at the median growers need to support the hygienic use of nonbreast milk supplements. Improving family wealth will also improve the nutritional status of the median growers, but less so than for the negative deviants.