Comparison of some properties of the CAMP-factor from Streptococcus agalactiae with the haemolytically latent active exosubstance from Streptococcus uberis

CAMP factor homologues in Propionibacterium acnes: a new protein family differentially expressed by types I and II

Analysis of the draft genome sequence of the opportunistic pathogenPropionibacterium acnestype strain NCTC 737 (=ATCC 6919) revealed five genes with sequence identity to the co-haemolytic Christie–Atkins–Munch-Peterson (CAMP) factor ofStreptococcus agalactiae. The predicted molecular masses for the expressed proteins ranged from 28 to 30 kDa. The genes were present in each of the three recently identifiedrecA-based phylogenetic groupings ofP. acnes(IA, IB and II), as assessed by PCR amplification. Conserved differences in CAMP factor gene sequences between these three groups were also consistent with their previous phylogenetic designations. All type IA, IB and II isolates were positive for the co-haemolytic reaction on sheep blood agar. Immunoblotting and silver staining of SDS-PAGE gels, however, revealed differential protein expression of CAMP factors amongst the different groups. Type IB and II isolates produced an abundance of CAMP factor 1, detectable by specific antibody labelling and silver staining of SDS-PAGE gels. In contrast, abundant CAMP factor production was lacking in type IA isolates, although larger amounts of CAMP factor 2 were detectable by immunoblotting compared with type II isolates. While the potential role of the abundant CAMP factor 1 in host colonization or virulence remains to be determined, it should be noted that the type strain ofP. acnesused in much of the published literature is a type IA isolate and is, therefore, lacking in this attribute.

Virulence factors of Streptococcus uberis isolated from cows with mastitis

For intramammary infections (IMI) to occur, mechanisms associated with avoidance of phagocytic defenses, rapid growth of bacteria, adherence of bacteria to epithelial cells, and/or bacterial colonization of mammary tissue are probably present. During the last decade, several potential virulence factors of Streptococcus uberis have been identified. Some of these factors are cell-associated while other factors are extracellular. Proposed antiphagocytic factors of S. uberis include capsule, neutrophil toxin, M-like protein and R-like protein. Activation of plasminogen by S. uberis has been proposed as an important mechanism for this organism to obtain nutrients for optimal bacterial growth. Potential virulence factors produced by S. uberis and released extracellularly include hyaluronic acid capsule, hyaluronidase and uberis factor. Streptococcus uberis isolated from bovine IMI adhere to and invade mammary epithelial cells. Involvement of intact microfilaments and de novo eukaryotic protein synthesis are required for bacterial invasion of mammary epithelial cells; a process that appeared to occur by a receptor-mediated endocytosis mechanism. De novo bacterial protein synthesis was also required for invasion of S. uberis into mammary epithelial cells. Furthermore, S. uberis survived within mammary epithelial cells for extended periods of time without losing viability or damaging the eukaryotic cell. Further research directed towards characterization of host-pathogen interactions that take place during the early stages of S. uberis intramammary infection are needed to enhance our understanding of pathogenesis and thus contribute to development of methods to minimize production losses associated with S. uberis mastitis in dairy cows.

Partial characterization of the cohemolytic factor produced by Streptococcus uberis and comparison with the CAMP-factor

Exosubstances (cohemolysins) produced by Streptococcus agalactiae (CAMP-factor) and Streptococcus uberis (Uberis-factor) showing hemolytic synergism with beta-lysin produced by Staphylococcus aureus were compared. Cohemolytic activity was evaluated in the supernatants of bacterial cultures, before and after ammonium sulfate precipitation. Sheep erythrocytes sensitized with beta-lysin were used as substrate. The assays were performed in microtiter plates and results were expressed as cohemolytic units/ml. Maximum cohemolytic activity was detected, respectively, after 8 h and 14 h of growth in Columbia broth in S. uberis and S. agalactiae cultures. Cohemolytic activities of both microorganisms showed similarities when submitted to various physical and chemical treatments. They were significantly decreased by heating at 60 degrees C and 100 degrees C, or in presence of trypsin, and were abolished in the presence of Tween 20. Activities were found to be stable in crude supernatants and concentrated preparations maintained at -20 degrees C for 3 months. Differences were related to levels of activity and kinetics of detection during the growth cycle. The results indicate the proteic nature, at least in part, of the Uberis factor. Analysis by PAGE in the presence or absence of SDS allowed us to correlate Uberis activity with a protein band with apparent molecular mass of 42 kDa, while CAMP activity was associated with a protein band of 27 kDa.

Antigenicity of Dermatophilus congolensis hemolysin

The separated cell-free form of hemolytic exosubstance was obtained from five strains of Dermatophilus congolensis. Three strains produced exosubstance with high activity, two strains produced exosubstance with lower intensity of activity. The separated forms exhibited the same hemolytic interactions as the native forms produced by growing strains, namely the antagonism with staphylococcal beta hemolysin and the synergism with staphylococcal delta hemolysin, streptococcal CAMP factor and rhodococcal equi factor. Rabbit sera obtained after intravenous or intraperitoneal application of the separated forms contained precipitation and neutralization antibodies. Cross tests of precipitation and neutralization proved antigen identity of hemolysins of different D. congolensis, strains which makes the serodiagnostics of this species possible.

Biochemical and serological properties of Streptococcus uberis

The Strep-Zym identification system, a combination of 23 enzymatic tests, allowed a rapid biochemical characterization of Streptococcus uberis. The biochemical profiles of the S. uberis cultures clearly differed from those of S. agalactiae and S. dysgalactiae. Serological grouping of S. uberis revealed polysaccharide antigens of groups E, G, P and U. Some cultures of S. uberis demonstrated CAMP-like synergistic hemolytic activities on sheep blood agar and reacted specifically with the lectins of Helix pomatia and Dolichos biflorus. The occurrence of group polysaccharides, CAMP-like reactivities, and the lectin agglutination reactions were obviously not related to each other or to any of the biochemical properties. These reactions, possibly of importance as virulence factors, might serve as epidemiological markers.

Purification and partial characterization of a cohaemolysin (CAMP-factor) produced by Streptococcus canis

A cohaemolysin from the culture supernate of a canine pathogenic group G streptococcus (S. canis) was purified to electrophoretic homogeneity. The purification procedure involved ammonium sulphate precipitation, ultrafiltration, gel filtration and preparative isoelectric focusing. The cohaemolysin consisted of a single polypeptide chain, 18.6 kDa, with an isoelectric point at pH 5.1. The protein reacted with an homologous antiserum, appeared to be trypsin-sensitive and relatively heat-stable. The cohaemolysin did not show any non-specific IgG binding activities.