Assessment of immunity against avian colibacillosis induced by an aroA mutant containing increased serum survival gene in broilers

Abstract

Colibacillosis is an important disease in the poultry industry which causes serious economic damages. As it is suggested that vaccination is one of the means to control colibacillosis, we tried to investigate the vaccine potential of a ΔaroA derivative of an O78:K80 avian pathogenic Escherichia coli containing increased serum survival gene. 490 chicks were selected as follows: For assessment of virulence of ΔaroA mutant, 30 chicks were divided into three groups and injected with 0.5ml of PBS or bacterial suspension containing either10(7)colony forming units (CFU) of mutant or parent strains via subcutaneous route. Macroscopic lesions and mortality rate were recorded in different groups during the week after challenge. For assessment of safety and immunogenicity of the ΔaroA mutant, three groups of 20 chicks were vaccinated by aerosol administration of 250 ml of suspension containing 10(8) CFU of mutant strain at days 1 and 14, while the two other groups received PBS or wild type strain. Macroscopic lesions and mortality rate were recorded in different groups until day 21. To determine whether the vaccination is protective against challenges or not, the chickens were vaccinated at days 1 and 14 and challenged intramuscularly with either a homologous or heterologous strains at day 21. Macroscopic lesions and mortality rate were recorded in different groups during the week after challenge. The results revealed that the ΔaroA mutant was slightly virulent, however it was safe and did not cause mortality, lesions or weight loss after vaccination. Antibody responses were similar in the control and mutant groups and vaccination did not induce a significant humoral immunity. The mutant could not protect chickens against both homologous and heterologous challenges. This could be due to several factors such as the high amount of maternal antibodies in the first two weeks of life, and the vaccination procedure

Avian Pathogenic Escherichia coli and Clostridium perfringens: Challenges in No Antibiotics Ever Broiler Production and Potential Solutions

“…Early attempts in APEC vaccines resulted only in protection against homologous challenge; that is, protection was only effective against the single strain that was used to create the vaccine [152,[161][162][163]. Effective vaccination whether by subunit vaccines, that target specific genetic virulence factors, or by live attenuated vaccines (LAV), have mostly resulted in coverage only against homologous challenge [164][165][166][167]. One commercially available LAV produced from nonpathogenic E. coli provides protection via cell-mediated immunity [168].…”

Protective Efficacy of a Commercial Live Attenuated aroA mutant Vaccine Against Avian Pathogenic Escherichia coli Challenge in Broilers

“…Two-fold serial dilution of each serum sample was carried out using nine clean dry tubes containing a diluent of 0.9% w/v of NaCl sterile solution [21]. In the first tube 0.1 mL of serum was mixed with a 0.9 mL of diluent and then 0.5 mL of diluted serum was transferred to a second tube containing 0.5 mL of a diluent.…”

Bioavailability pharmacokinetics and residues of marbofloxacin in normal and E.coli infected broiler chicken

“…Each chicken was experimentally infected with a pathogenic strain of Escherichia coli. (E. coli O111:H4) by injection of 0.5 ml of the required concentration (10 7 micro-organism/ml) subcutaneously in the neck region of birds (Salehi et al, 2012). After appearance of the clinical symptoms of bacteraemia as fever and bloody diarrhea 48 hours post infection with Escherichia coli suspension, each infected bird was given marbofloxacin orally at dose rate of 2 mg/kg b.wt of once daily for five consecutive days.…”