Determination of epidemiological relationships ofStreptococcus agalactiaeisolated from bovine mastitis

Abstract

In the present study 79 streptococcal cultures isolated from subclinical mastitis of 54 cows from seven dairy farms (A^G) in Hesse, Germany, were comparatively investigated using conventional and molecular methods. The isolates could be identified as Streptococcus agalactiae, belonging to Lancefield's serological group B by determination of cultural, biochemical and serological properties and by polymerase chain reaction (PCR)-mediated amplification of species-specific parts of the 16S ribosomal DNA, the 16S^23S rDNA intergenic spacer region and the CAMP factor gene cfb. The investigated group B streptococci were further characterized serologically for specific polysaccharide and protein antigens. Serotyping the isolates revealed a predominance of surface protein antigen X, either alone or in combination with polysaccharide antigen Ia. This could be observed for 39 isolates of farms A, B and C. Six group B streptococci from farm E displayed the serotype pattern III/Rib, two isolates from farm G showed the serotype pattern Ib/cK. The remaining cultures from farms D and F (n = 32) were non-typable. The occurrence of protein Rib could be confirmed by PCR amplification of the gene rib. The two isolates with serotype pattern Ib/cK also reacted positively for the cL-encoding gene bag. Additional properties which allowed a phenotypic characterization of the S. agalactiae were the degree of pigmentation, growth properties in fluid media and soft agar, the surface hydrophobicity, the ability to hemagglutinate rabbit erythrocytes and their resistance reactions to tetracycline and minocycline. The isolates of the seven farms showed identical or almost identical characteristics. The 79 group B streptococci were additionally investigated by macrorestriction analysis of their chromosomal DNA using the restriction endonucleases SmaI, ApaI and SalI. The restriction patterns obtained by pulsed-field gel electrophoresis displayed identical or closely related patterns for the cultures of the various farms. The pheno-and genotypic characteristics of the 79 group B streptococci of the present study revealed that a single S. agalactiae strain or at least closely related subtypes of this strain were responsible for the mastitis situation of the seven farms.

Phenotypic and Molecular Characteristics of Streptococcus agalactiae Isolates Recovered from Milk of Dairy Cows in Brazil

“…These aspects support the hypotheses of a bovineadapted ecovar of S. agalactiae compared to strains from other hosts (9). Similar results were previously found when isolates from bovine milk were investigated in Kenya, New Zealand, and North America (14,23,24,36). In accordance with earlier observations (14,24), production of acids from galactose, lactose, and salicin was a trait found frequently among bovine strains.…”

“…This was unexpected because we have obtained enzyme restriction for other isolates with identical biotypes and serotypes and also because we have not experienced difficulties with SmaI restriction during an ongoing study involving a large number of GBS isolates from human sources. On the other hand, the occurrence of failures with PFGE typing of GBS isolates has already been documented in previous reports, frequently associated with isolates obtained from the same herd and harboring similar phenotypic and genotypic characteristics (13,23). Methylation of the cutting sequences seems to be related to the isolates showing unrestricted PFGE profiles.…”

“…One system (PFGE using SmaI) is now considered a "gold standard" technique for typing several bacterial pathogens including the streptococci associated with bovine mastitis (2,23). The other system (RAPD-PCR using primer 1254) has been used for typing different microorganisms (1, 28) but has not previously been applied to type GBS isolates.…”

Presence and antibiotic susceptibility patterns of contagious mastitis agents (Staphylococcus aureus and Streptococcus agalactiae) isolated from milks of dairy cows with subclinical mastitis

“…Similarly, Kaşıkçı et al (8) Subclinical mastitis, which is a hidden form of mammary gland infection, is a very complex disease with numerous causative agents. Contagious pathogens such as S. aureus or S. agalactiae, which are the most common agents related to subclinical mastitis, are responsible for the strong indicators of the presence of intramammary infections in a herd (1,4). In the present study, S. aureus was detected in 4.44% of analyzed milk samples, while S. agalactiae was found in 9.25% of milk samples.…”

“…agalactiae is a major contagious pathogen causing bovine subclinical mastitis that can survive for long periods within the mammary gland and can be transmitted to healthy cows through poor milking hygiene (3,4). S. aureus is considered to be one of the most common causes of bovine mastitis in the world, which is most frequently subclinical (1).…”