Avian pathogenic E. coli (APEC) has meticulous virulence properties making it a
potential pathogen causing insidious infections in poultry, termed as colibacillosis either
as primary pathogen or as a secondary pathogen. All over the world, there are major
economic losses in poultry industry due to this disease. To prevent APEC infection,
strategies include improving hygienic methods, vaccination, antibiotic treatment and
introduction of novel immunopotentiators but all these measures had limited success.
Moreover, because of extensive use of antibiotics for treatment purposes, antibiotic
resistance is major growing concern. Bacteriophage therapy is promising new alternative
to antibiotics. There are many benefits of phages over antibiotics and are now used in
research for the treatment of enteric and respiratory problems in poultry and are proved to
be effective in reducing E.coli infection.
In present study bacteriophages was used to minimize and control the number of
E.coli causing colibacillosis in poultry. For this, E.coli (n = 10) from liver of infected
commercial poultry birds and E.coli (n = 5) from intestines of apparently healthy birds
was isolated and characterized using biochemical tests. Final confirmation of E.coli
isolates was done by PCR. To differentiate between pathogenic and non-pathogenic
E.coli, Congo Red Dye binding test (CR test) was performed. Antibiotic resistance
profiling of the isolates was also determined against 10 commonly used antibiotics
through Kirby-Bauer disk diffusion method.
For the isolation of bacteriophages, sewage or poultry sludge sample was
processed according to literature method and purified bacteriophages (n = 5) were
Summary
63
assessed for their stability at various temperature and pH. Bacteriophages were also
assessed for their In-Vitro Lytic Activity of against E. coli isolates.
Five numbers of lytic bacteriophages were isolated and purified against avian
pathogenic E.coli, showing resistance against Ampicillin, Doxycycline, Ciprofloxacin,
Neomycin, Trimethoprim-sulphamethoxazole, Nalidixic acid and Ceftriaxone. Isolates
were also classified into pathogenic and non-pathogenic on the basis of their ability to
bind Congo red dye on Congo red media. Phages were highly lytic against pathogenic
isolates while there was no lytic activity against non-pathogenic isolates thus making
them unique for in vivo trials. Phages were found to be stable at temperature from 25oC
to 56oC with highest stability at 37oC while on the basis of pH, phages were stable
between 5-9 pH with highest stability at pH 7. Maximum lytic activity observed was for
12 hours and then there was emergence of resistant bacteria and this problem may be
tackled by increasing MOI or by using combinations of phages against resistant bacteria.
Present study helped to reveal the effectiveness of bacteriophages against antibiotic
resistant E.coli and proved that bacteriophages can be used as promising alternatives to
antibiotics for reducing E.coli infection in poultry.