Influence of some environmental variables and addition of r-lysozyme on efficacy of Vibrio harveyi phage for therapy

Bacteriophage therapy is a viable proposition for controlling luminous vibriosis caused by Vibrio harveyi in shrimpaquaculture. However, environmental factors influence the growth and activity of phage and affect its efficiency incontrolling bacterial diseases. An essential problem in the use of vibrio phage as a therapeutic agent was the development ofresistance to phage attachment, rendering them resistant to the lytic action of phage. This problem could be overcome byapplying a cocktail of phages. This study aimed to evaluate the effect of salinity and pH on the phage activity and also tostudy the role of recombinant shrimp lysozyme on the performance of the V. harveyi phage. Out of three different levels ofsalinity (20, 25 and 30 ppt) and pH (6, 7 and 8) tested, optimum phage activity was observed at a salinity of 25 ppt and atneutral pH. Application of recombinant shrimp lysozyme in combination with V. harveyi phage significantly improved theactivity of phage in in vitro assay as well as in microcosm study using seawater. The application of phage along withlysozyme can be a useful approach to overcome the inability of phage to enter the bacteria and thus eliminate or reduce fish/shrimp pathogenic bacteria in aquaculture.

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for rapid diagnosis of neonatal sepsis.

Background & objectives: The difficulties in diagnosis of neonatal sepsis are due to varied clinical presentation, low sensitivity of blood culture which is considered the gold standard and empirical antibiotic usage affecting the outcome of results. Though polymerase chain reaction (PCR) based detection of bacterial 16S rRNA gene has been reported earlier, this does not provide identification of the causative agent. In this study, we used restriction fragment length polymorphism (RFLP) of amplified 16S rRNA gene to identify the organisms involved in neonatal sepsis and compared the findings with blood culture. Methods: Blood samples from 97 neonates were evaluated for diagnosis of neonatal sepsis using BacT/Alert (automated blood culture) and PCR-RFLP. Results: Bacterial DNA was detected by 16S rRNA gene PCR in 55 cases, while BacT/Alert culture was positive in 34 cases. Staphylococcus aureus was the most common organism detected with both methods. Klebsiella spp. was isolated from four samples by culture but was detected by PCR-RFLP in five cases while Acinetobacter spp. was isolated from one case but detected in eight cases by PCR-RFLP. The sensitivity of PCR was found to be 82.3 per cent with a negative predictive value of 85.7 per cent. Eighty of the 97 neonates had prior exposure to antibiotics. Interpretation & conclusions: The results of our study demonstrate that PCR-RFLP having a rapid turnaround time may be useful for the early diagnosis of culture negative neonatal sepsis.