Development of a monoclonal antibody-based co-agglutination test to detect enterotoxigenic Escherichia coli isolated from diarrheic neonatal calves

Molecular screening and risk factors of enterotoxigenic Escherichia coli and Salmonella spp. in diarrheic neonatal calves in Egypt

The aim of the present study was to carry out molecular epidemiological investigation on enterotoxigenic Escherichia coli (ETEC) K99 and Salmonella spp. in diarrheic neonatal calves. Fecal samples were obtained from 220 diarrheic calves at 9 farms related to four governorates in central and northern Egypt. E. coli and Salmonella spp. isolates were examined for E. coli K99 and Salmonella spp. using PCR. ETEC K99 was recovered from 20 (10.36 %) out of 193 isolates, whereas Salmonella spp. was recovered from nine calves (4.09%). Multivariable logistic regression was used to evaluate the risk factors associated with both infections. ETEC K99 was significantly affected by age (P<0.01; OR: 1.812; CI 95%: 0.566-1.769), colostrum feeding practice (P<0.01; OR: 5.525; CI 95%: 2.025-15.076), rotavirus infection (P<0.001; OR: 2.220; CI 95%: 0.273-1.251), vaccination of pregnant dams with combined vaccine against rotavirus, coronavirus and E. coli (K99) (P<0.001; OR: 4.753; CI 95%: 2.124-10.641), and vitamin E and selenium administration to the pregnant dam (P<0.01; OR: 3.933; CI 95%: 0.703-1.248). Infection with Salmonella spp. was found to be significantly affected by the animal age (P<0.05; OR: 0.376; CI 95%: 0.511-1.369), Hygiene (P<0.05; OR: 0.628; CI 95%: 1.729-5.612), and region (P<0. 01; OR: 0.970; CI 95%: 0.841-1.624). The results of the present study indicate the importance of PCR as rapid, effective and reliable tool for screening of ETEC and Salmonella spp. when confronted with cases of undifferentiated calf diarrhea. Moreover, identification of the risk factors associated with the spreading of bacteria causing diarrhea may be helpful for construction of suitable methods for prevention and control.

Coagglutination for viral DNA preparation of canine parvovirus for molecular diagnosis

The use of PCR for molecular diagnosis is accepted as the standard method for detecting nucleic acids from numerous major infectious agents using diverse sampling techniques. Although PCR is an essential tool in the research laboratory; the success of the method depends on a sample free of inhibitors that was obtained preferably by a simple and fast extraction method. The coagglutination test (COA test) is based on the propriety of protein A, from Staphylococcus aureus, which can bind specifically to the Fc portion of immunoglobulin G (IgG) in various mammals and to several IgG subclasses in mice. In this study, the COA method capacity of generating inhibitor-free DNA sample was tested. Ten fecal samples positive for canine parvovirus were subjected to nucleic acid extraction using COA method and a commercial kit (Illustra GFX Genomic Blood DNA Purification Kit/G.E. Healthcare); and the samples' viral DNA content were compared using real-time PCR. The COA procedure allowed the extraction of larger amount of viral DNA from feces than the commercial kit. This method was shown to be simple and effective for DNA extraction, concentrating viral particles dispersed in the biological samples.