Bottle Use Associated with Increased Risk of Candida Infections

Candida species are fungi that can live in human tissues and cause infections in the
mouth (thrush), vagina, and skin (as on the breast). Sometimes the organism can be
present without obvious symptoms. The most common signs and symptoms associated
with infection in nursing mothers include burning nipples, painful breasts, stabbing pain
throughout the breast, and shiny or flaky skin on the nipple or areola area. Usually,
doctors make a diagnosis based on clinical signs and symptoms but a new technique for
culturing milk samples can also be used. The purpose of this study was to determine
Candida infection rates using this technique and risk factors in a group of lactating
mothers.

Recruited from private clinics in Reno Nevada, the sample included 100 breastfeeding
mothers and, as a comparison group, 40 nonbreastfeeding, nonpregnant women, of
similar age, ethnicity, and educational background. The subjects used sterile swabs to
collect samples from skin on the nipples and breast. The breastfeeding women also
provided milk samples and swabs of the baby’s mouth. Other data, collected by
interview, included history of vaginal or other yeast infections and antibiotic use in the
past nine months. The first interview and sampling occurred about two weeks after
delivery; a follow-up interview took place at nine weeks postpartum.

Twenty-three percent of the breastfeeding mothers tested positive for Candida, compared
to none of the nonbreastfeeding women. Twenty percent of the infants tested positive,
including five infants whose mothers had tested negative. In the mothers, the strongest
risk factors for presence of Candida were bottle use during the first two weeks and
duration of pregnancy beyond 40 weeks, whereas antibiotic use at delivery reduced the
risk. In the infants, bottle use and mother’s multiparity increased the risk. Among the
women who tested positive at two weeks, only 43% were still breastfeeding at nine
weeks, compared to 69% of those who tested negative for Candida (p < 0.27). Although
the exact reasons for these associations are not known, iron-fortified formula may
stimulate growth of the organism in the infant’s mouth. Longer duration of pregnancy
may cause changes in the vaginal flora that enhance growth of Candida. Infants of
multiparous mothers may be exposed to Candida through older siblings.

Conclusions and Implications: Although “cause and effect” cannot be proven in
observational studies, bottle use in the first two weeks of life may increase the risk of
Candida infection in mothers and infants. Candida infection is associated with early
termination of breastfeeding.

Source: Morrill JF, Heinig MJ, Pappagianis D, Dewey KG. Risk factors for mammary candidosis among
lactating women. JOGNN 2005; 34: 37-45.