DAIRY INFECTION WITH STREPTOCOCCUS EPIDEMICUS

Lipid lysination by MprF contributes to hemolytic pigment retention in group B Streptococcus

Group B Streptococcus (GBS) is the leading cause of neonatal sepsis and meningitis. A major virulence factor is a pigmented beta-haemolytic/cyto-lysin (β-h/c) toxin with an ornithine rhamnolipid structure. We initially observed that absence of MprF enzyme altered pigmentation and haemolytic activity in GBS. Next, we showed that MprF-dependent lipid lysination contributes to the retention of the ornithine rhamnolipid within GBS membrane. Furthermore, cationic lipidation by MprF altered membrane properties contributing to resistance to the cyclic lipopeptide daptomycin and to acidic pH. This study highlights the importance of cationic lipids in cell envelope homeostasis and in modulating β-h/c activity.

Growth of Streptococcus pyogenes in milk stored at atmospheric temperatures

1.Streptococcus pyogenesmultiplies readily in sterilized milk stored at 22 and 18° C., and more slowly at 15° C. In fresh raw milk this organism begins to multiply slowly only after 48–72 hours of storage at 18–22° C. In laboratory pasteurized milk the result is similar, but both commercially pasteurized milk and raw graded milk bottled for distribution sour too rapidly for multiplication to take place after artificial contamination. These facts suggest that widespread epidemics are rarely due to extensive multiplication ofS. pyogenesin milk during commercial or household storage.

2. The initial degree of contamination of milk withS. pyogeneshas no influence upon this organism's ability to multiply during storage.

3. The failure ofS. pyogenesto multiply during storage is due to (a) its natural reluctance to grow at atmospheric temperatures, (b) the bacteriostatic action of the milk, and (c) the readiness with which saprophytic bacteria multiply at atmospheric temperatures.

4. It is contended that infected cows play a major part in the spread of milk-borneS. pyogenesepidemics, and relevant literature is quoted to support this view. It is urged that routine investigation of apparent milk-borne epidemics should include the immediate bacteriological examination of an individual sample of milk from every cow concerned in the supply under suspicion.

UDDER INFECTION WITH STREPTOCOCCI OF THE SCARLET FEVER TYPE : I. SPONTANEOUS AND EXPERIMENTAL UDDER INFECTION

The clinical and bacteriological findings in two cows the udders of which became infected under natural conditions with hemolytic streptococci of the scarlet fever type are discussed. One of the cows was found in a herd supplying raw milk to a small town where a milkborne outbreak of scarlet fever had occurred a short time before. When small numbers of the streptococcus obtained from this case were injected into the udder of a normal cow severe mastitis accompanied by a well marked general reaction resulted. Evidence leads to the conclusion that a severe attack of mastitis due to this organism in one quarter does not sufficiently immunize the other quarters to protect them completely since the streptococcus can be readily implanted in them. The secondary infections were much milder than the original process.