Mammary candidiasis: A medical condition without scientific evidence?

Abstract

Many physicians, midwives and lactation consultants still believe that yeasts (particularly Candida spp.) play an important role as an agent of nipple and breast pain despite the absolute absence of scientific proofs to establish such association. In this context, the objective of this study was to investigate the microorganisms involved in sore nipples and/or painful "shooting" breastfeeding by using a variety of microscopy techniques, as well as culture-dependent and-independent identification methods. Initially, 60 women (30 diagnosed as suffering "mammary candidiasis" and 30 with no painful breastfeeding) were recruited to elucidate the role of their pumps on the milk microbial profiles. After realizing the bias introduced by using such devices, manual expression was selected as the collection method for the microbiological analysis of milk samples provided by 529 women with symptoms compatible with "mammary candidiasis". Nipple swabs and nipple biopsy samples were also collected from the participating women. Results showed that the role played by yeasts in breast and nipple pain is, if any, marginal. In contrast, our results strongly support that coagulase-negative staphylococci and streptococci (mainly from the mitis and salivarius groups) are the agents responsible for such cases. As a consequence, and following the recommendations of the US Library of Medicine for the nomenclature of infectious diseases, the term "mammary candidiasis" or "nipple thrush" should be avoided when referring to such condition and replaced by "subacute mastitis".

Fig 1. Schematic representation of the two parts of the study, including the number of recruited women and the type and number of the biological samples that were analysed.

Fig 2. Microbial counts of milk samples obtained after milk extraction by manual expression (panel A) or pumping (panel B).

Samples from women without painful breastfeeding are marked as "NoP" at the bottom of the figure while samples from women with painful breastfeeding are marked as "P" at the bottom of the figure and are shaded in grey. Abbreviations: Sepi, Staphylococcus epidermidis; Saur, Staphylococcus aureus; Stm/o, Streptococcus mitis/oralis; Stsal, Streptococcus salivarius; Roth, genus Rothia; Cory, genus Corynebacterium; Entb, Enterobacteriaceae; Ogneg, otherGram-negativebacteria; Ytot, yeasts (total); Calb, Candida albicans; Cpar, Candida parapsilosis; Scer, Saccharomyces cerevisiae. *, P<0.05; ***, P<0.001.

Fig 3. Optical microscopy observation of milk samples from a woman with presumptive signs of “mammary candidiasis” (A), and from another women without painful breastfeeding (B).

1, Staphylococcus epidermidis cells; 2, T cells; 3, epithelial cells; 4, polymorphonuclear neutrophil. Note the absence of yeasts’ cells.

Fig 4. TEM images of two nipple biopsies from women with presumptive signs of “mammary candidiasis”.

1, Staphylococcus epidermidis cells. Note the absence of yeasts’ cells.

Fig 5. TEM image showing a closer view of rapidly dividing Staphylococcus epidermidis cells in a nipple biopsy from a woman with presumptive signs of “mammary candidiasis”.