Mastitis is a common problem causing cessation of breast feeding in modern nurseries. In an attempt to identify early markers for mastitis we measured the cell count and inflammatory chemokine content of breast milk longitudinally in 10 mothers following healthy term deliveries over 2-6 weeks(median 2.5 weeks). Two mothers gave milk samples separately from each breast. Milk samples were kept at 4°C, and processed within 8 hours of collection; centrifuged aliquots were frozen for batch ELISA assays (triplicates) for IL-8 and RANTES. Aliquots were cultured using routine microbiology. These methods were verified using spiked samples. We observed high levels of the chemokines in all samples (median IL-8 2.5 ± 0.5 ng/ml, range 0.5-12ng/ml, median RANTES 5.5 ± 0.8 ng/ml, range 0-20 ng/ml). Concentrations were higher in the first week of lactation, but particularly high levels were identified in one mother, and from one breast which subsequently over 4 days developed sterile mastitis (peak IL-8 12 ±0.9 ng/ml, peak RANTES 20 ± 1.1 ng/ml). Higher chemokine levels were associated with higher cell counts, this was not a linear association. There was no correlation with bacterial colony counts. Milk cytokines are useful preclinical indicators and as inflammatory mediators may play an important role in the aetiology of mastitis.
