No abstract

Procedures for diagnosis of mammary candidosis, including laboratory confirmation, are not well defined. Lactoferrin present in human milk can inhibit growth of Candida albicans, thereby limiting the ability to detect yeast infections. The inhibitory effect of various lactoferrin concentrations on the growth of C. albicans in whole human milk was studied. The addition of iron to the milk led to a two-to threefold increase in cell counts when milk contained 3.0 mg of lactoferrin/ml and markedly reduced the likelihood of false-negative culture results. This method may provide the necessary objective support needed for diagnosis of mammary candidosis.Candida albicans is an opportunistic pathogen that can cause superficial, localized, and/or systemic infection (4). Superficial and localized breast yeast infections (mammary candidosis) in lactating women have been reported (1, 2). The diagnosis and management of candidosis in the breastfeeding mother and infant are challenging (5). Mammary candidosis is most often presumptively diagnosed by signs or symptoms such as burning or shooting pain in the breast during and after feedings and persistently sore or cracked nipples that do not heal (11). In a recent survey of 312 physicians in the Academy of Breastfeeding Medicine, 95% of family practitioners and 87% of obstetricians/gynecologists did not use laboratory tests to diagnose mammary candidosis (5). However, diagnosis of mammary candidosis based on symptoms alone may be erroneous, as it has been shown that breast pain is frequently associated with Staphylococcus aureus infection among breastfeeding women (1, 12). On the other hand, laboratory culturing of human milk for mammary candidosis is not well defined. Constituents of milk (9), such as lactoferrin (10), may interfere with recovery of Candida by culture. Iron-free human lactoferrin kills C. albicans in a dose-dependent manner (13), whereas iron-saturated lactoferrin does not inhibit C. albicans growth (7). Andersson et al. found that dilute, skim human milk (diluted with RPMI 1640 medium) had fungistatic effects on C. albicans that were reversed by the addition of iron (3). Therefore, we studied the effects of lactoferrin, with and without added iron, on the growth of C. albicans in undiluted whole human milk.The objectives of this study were (i) to determine how various concentrations of lactoferrin in whole human milk affect the growth of C. albicans and (ii) to quantitate the effect of added iron in cultural recovery of C. albicans from human milk containing lactoferrin. The ultimate goal was to develop a culture technique that minimizes the likelihood of false-negative cultures.Lactoferrin-free human milk was used as the culture medium. Lactoferrin was removed by treatment with heparinSepharose (6). Lactoferrin purchased from Sigma-Aldrich (St. Louis, Mo.) was then added to the milk to obtain three concentrations: 0.1, 1.0, and 3.0 mg per ml. Lactoferrin-free milk and phosphate-buffered saline (PBS) served as control media. C. albicans EK2001 isolated from ...