ABSTRACT
A multiplex PCR method was developed to characterize the potential variability within the sip gene from bovine isolates of Streptococcus agalactiae. An incomplete sip gene (ncosip) was found in four isolates of S. agalactiae. According to the in silico analysis of the missing region at amino acid level, the N-terminal of surface immunogenic protein (Sip) was found to contain a LysM domain motif; whilst the incomplete Sip (NcoSip) lacked a part of this motif. Immunity elicitation against Sip was confirmed by immunization of mice. This response was partially observed also with NcoSip.
Subject(s)
Antigens, Bacterial/chemistry , Antigens, Bacterial/immunology , Streptococcal Infections/immunology , Streptococcus agalactiae/immunology , Amino Acid Motifs , Amino Acid Sequence , Animals , Antibodies, Bacterial/blood , Antigens, Bacterial/genetics , Humans , Male , Mice , Mice, Inbred BALB C , Molecular Sequence Data , Streptococcal Infections/microbiology , Streptococcus agalactiae/chemistry , Streptococcus agalactiae/geneticsABSTRACT
A simple and specific method for direct detection of bovine mastitis pathogens (Streptococcus agalactiae (GBS), Staphylococcus aureus and Escherichia coli) in milk products, bacterial samples from milk and isolated bacterial DNA was developed. The method is based on polymerase chain reaction (PCR) using sequence-specific primers only for GBS and species-specific primers derived from 16S and 23S rRNA for all chosen species. The presence of the gene of surface immunogenic protein (Sip) in bovine GBS isolates, described previously only in human GBS isolates was confirmed. The GBS detection was performed with the sequence coding for surface immunogenic protein from GBS human isolates designated as Sip specific sequence (SSS); this sequence was selected for specific primer design. The sequence is unique for GBS and was designed from a consensus of all known sip genes. The specific identification was shown on a collection of 75 GBS bovine isolates from different localities in Slovakia. All isolates were positive to SSS, 16S and 23S rRNA sequence. The 16S and 23S rRNA PCR detection was also performed with S. aureus and E. coli isolates and specific PCR products were also detected. The detection limit of this assay for milk products was 6 CFU/microL (i.e. 6000 CFU/mL) for GBS and E. coli, and 16 CFU/microL for S. aureus. This rapid, sensitive and specific diagnostic method can be performed within hours and represents an innovative diagnostic tool for the detection of milk pathogens in dairy products.
