The recovery of small numbers of Staphylococcus aureus infused into the bovine teat cistern

Abstract

SummarySmall volumes of milk each containing an average of less than 10 colonyforming units of Staphylococcus aureus were injected into the teat cisterns of 39 quarters of 10 cows.Typical staphylococci were recovered from only 14 quarters following overnight incubation of milk stripped manually from each quarter 10 min after injection. There was an inverse relationship between the total leucocyte count of the milk taken from the quarter before infusion and recovery of staphylococci.From 4 of 8 quarters from which Staph. aureus could not be recovered by enrichment it was possible to recover the organism by centrifuging the milk and culturing the deposit of leucocytes and bacteria.It is suggested that release of ingested staphylococci from defunct phagocytes may be important in initiation of infection, failure of antibiotic therapy and recurrence of infection.

Ability of Staphylococcus aureus coagulase genotypes to resist neutrophil bactericidal activity and phagocytosis

“…Various pathogenic mechanisms may mediate the suppression of neutrophil populations. Previous researchers have shown that S. aureus is capable of surviving intracellularly, which may contribute to the chronic nature of S. aureus mastitis (19,20). Furthermore, S. aureus produces several substances that have been associated with virulence (2), includ-ing the enzyme coagulase (15).…”

Evaluation of antibacterial agents in a high-volume bovine polymorphonuclear neutrophil Staphylococcus aureus intracellular killing assay

“…Although acute mastitis can sometimes be treated, chronic mastitis has a cure rate of only 50% (9) or less (21). It has been suggested (1,4,19) that chronicity may be due to survival of the microbe within phagocytes. This intracellular location may afford the microbe protection from the effects of the antibiotic (5,8).…”

Immune-Mediated Inflammation in the Lumen of the Bovine Mammary Gland

“…Mammary gland infections have been ex perimentally established by intraluminal in oculation of small numbers of pathogenic streptococci or staphylococci [15,16,20,21,25]. Indirect evidence indicates that nat ural infections are similarly initiated by small numbers of infecting organisms.…”

“…Preexisting low grade inflammation, assessed by the number of leukocytes in milk, has been associated with protection against small numbers of S. agalactiae or Staphylococcus aureus that are infective for normal glands. An early in flammatory response to experimental infu sion of small numbers of S. agalactiae or Aerobacter aerogenes has been associated with rapid clearance of the infection [2,8,11,15,16,22,23].…”