The effects of cloxacillin on staphylococci phagocytosed by bovine neutrophils

The effects of cloxacillin on staphylococci within neutrophils from the peripheral blood of cattle were examined. When cloxacillin was added to a preparation of intracellular staphylococci suspended in nutrient broth at 37 degrees C in the presence of lysostaphin, significantly more staphylococci were killed than in the controls without the antibiotic. Cloxacillin entered the neutrophils and made the intracellular staphylococci sensitive to lysis by lysostaphin when the neutrophils were disrupted. The intracellular action of cloxacillin was greater than when Hanks' balanced salt solution was the suspending fluid or when the broth was incubated at 4 degrees C. Failure to observe the effect in these circumstances was possibly due to a very low rate of metabolism in the staphylococci.