Faculty Publications

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    T4-like Escherichia coli phages from the environment carry blaCTX-M
    (John Wiley and Sons Inc, 2018) Mohan Raj, J.R.; Vittal, R.; Huilgol, P.; Bhat, U.; Karunasagar, I.
    The resistance determinant blaCTX-M has many variants and has been the most commonly reported gene in clinical isolates of extended spectrum beta-lactamase producing Escherichia coli. Phages have been speculated as potential reservoirs of resistance genes and efficient vehicles for horizontal gene transfer. The objective of the study was to determine the prevalence and characterize bacteriophages that harbour the resistance determinant blaCTX-M. Escherichia coli specific bacteriophages were isolated from 15 samples including soil and water across Mangaluru, India using bacterial hosts that were sensitive to ?-lactams. Phenotypic and genotypic characterization based on plaque morphology, host range, restriction fragment length polymorphism (RFLP), presence of blaCTX-M and electron microscopy was performed. Of 36 phages isolated, seven were positive for Group 1 of blaCTX-M. Based on host range and RFLP pattern, the seven phages were classified into four distinct groups, each harbouring a variant of blaCTX-M. Five phages were T4-like Myoviridae by electron microscopy which was further confirmed by polymerase chain reaction (PCR) for T4 specific gp14. Generalized transduction of the CTX-M gene from these phages was also observed. The high prevalence (20%) of this gene blaCTX-M in the phage pool confirms the significant role of Myoviridae members, specifically T4-like phages in the dissemination of this resistance gene. Significance and Impact of the Study: The CTX-M gene that confers resistance to Beta-lactam class of drugs is widespread and diverse. Understanding mechanisms of antimicrobial resistance transfer is a key to devise methods for controlling it. Few studies indicate that bacteriophages are involved in the transfer of this gene but the type of phages involved and the degree of involvement remains to be explored. Our work has been able to identify the class of phages and the magnitude of involvement in the dissemination of this gene. © 2018 The Society for Applied Microbiology
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    Isolation of Novel Aerobic denitrifier and optimization of process parameters for biological denitrification using RSM
    (Slovak University of Agriculture info@jmbfs.org, 2019) Joshi, K.; Navalgund, N.; Shet, V.B.; Srinikethan, G.; Ashwini; Sneha; Anusha; Aparna, A.
    The study aimed to isolate and characterize a high efficiency novel bacterium for denitrification in waste water and also to optimize process parameters under aerobic condition. One of the bacteria chosen among four, displayed a maximum of 98% reduction of nitrate. The strain was identified as Enterobacter sp. NCCP-29 by biochemical tests and further identified based on similarity of PCR-16S rRNA using universal primers. The parameters (pH, temperature, agitation speed, C:N ratio) which effect the denitrification were screened using one factor at a time. The pH, temperature and C:N ratio exhibited significant effect on the denitrification using Enterobacter sp. NCCP-29. The levels of these parameters were optimized using a central composite design (CCD). A maximum of 98% denitrification was achieved at pH 6.5, temperature 30°C and C: N ratio of 3:1. The second order model was generated and found to have a good fit with R2 value of 0.93. Investigations revealed the ability of Enterobacter sp. NCCP-29 to remove nitrate under aerobic conditions. © 2019, Slovak University of Agriculture.