Original article Arch Argent Pediatr 2013;111(2):115-119 / 115 Comparison of the risk of microbiological contamination between samples of breast milk obtained at home and at a healthcare facility Vera Vanina Serra, M.D.,a Sergio Teves, M.D.,b Agustina López de Volder, M.D.,b Fabiana Ossorio, M.D.,cNora Aguilar, R.N.,aand Marcelo Armadans, M.D.a ABSTRACT capitis), streptococci (salivarius, mitis, Introduction. Breast milk is the best food for parasanguis and peroris), lactobacilli preterm infants. Due to their inadequate suc- tion-swallowing action, the administration of (gasseri, rhamnosus, acidophilus, planta- expressed breast milk should be done with an rum and fermentum) and enterococci orogastric tube. There is little information avail- (faecium) are bacteria commonly isola- able regarding the microbiological safety of ex- ted in breast milk that can be conside- pressed breast milk. The aim of this article was to evaluate if there red part of the natural flora instead of were any differences regarding the contamina- contaminating microorganisms. The- tion of breast milk obtained at a healthcare fa- se bacteria have a protective action cility versus at home. against other microorganisms poten- Methods. Cross-sectional study that analyzed 3 pairs of breast milk samples (one obtained at tially harmful for the preterm infant. home and the other one at a healthcare facility, The importance of feeding breast the same day) from mothers of hospitalized new- milk to preterm infants has resulted born infants with a gestational age ≤35 weeks. in its manipulation. Expressed mi- Samples with over 105CFU/mL of mesophilic aerobic bacteria, or with the presence of Esch- lk should be given via an orogastric erichia coli, Staphylococcus aureus, Streptococcus tube because premature infants’ suc- faecalis, enterobacterias, Pseudomonas, Salmonella, tion-swallowing action is usually in- fungi, and yeast were considered contaminated. adequate.4 Results. A total of 280 breast milk samples (140 pairs) from 53 mothers were analyzed; Despite the enormous populari- 139 samples (49.6%; 95% CI: 43.6 to 55.6) were ty of this practice, there is little infor- contaminated; contamination was significantly mation about the microbiological safe more frequent in the samples obtained at home a. Neonatology preparation of expressed breast milk. than in those obtained at a healthcare facility Division, Instituto 5 (59.6% versus 39.6%; p = 0.0008; OR 2.25; 95% By and large, less than 10 CFU/mL Argentino de 5,6 IC: 1.36 to 3.7). of mesophilic aerobic bacteria, with Diagnóstico y Conclusion. Half of the breast milk samples had Tratamiento, a total count of enterobacteria lower bacterial growth, which was more frequent in the Marcelo T. de than 10 CFU/mL is considered bacte- samples obtained at home than those obtained Alvear 2346, Buenos at a healthcare facility. riologically acceptable. The presence Aires, Argentina Key words: breast milk, nutrition, newborn infant, of pathogenic bacteria such as Esche- b. Microbiology Chair, preterm baby. School of Pharmacy richia coli, Staphylococcus aureus, Strep- and Biochemistry, tococcus faecalis, Enterobacter sakazakii, Universidad de http://dx.doi.org/10.5546/aap.2013.115 (β-hemolytic) Streptococcus pyogenes, Buenos Aires species of Pseudomonas, Proteus and c. Department of Pediatrics, School Salmonellais considered unacceptable. of Medicine, INTRODUCTION The presence of fungi and yeast would Universidad de Breast milk is considered the best indicate unsatisfactory hygiene con- Buenos Aires food for preterm newborn infants, ditions.7,8 Mail: not only for its nutritional value but Even though food intolerance (vo- Marcelo Armadans, M.D. also for its capacity to provide pro- miting, abdominal bloating, diarrhea, marmadans@speedy. tection from infections.1,2 Part of this or gastric retention) is frequent in the com.ar protective effect would be given by feeding process of preterm infants,9,10 the natural microflora present in mi- it is difficult to prove whether breast Conflict of interest: lk, an important factor in the develop- milk bacterial contamination is the None. ment and composition of the newborn cause of such intolerance because the- Received: 4-4-2012 infant’s intestinal microflora. Sta- re are many other factors that might Accepted: 2-11-2012 phylococci (epidermidis, hominis and have an impact on this event. 116 / Arch Argent Pediatr 2013;111(2):115-119 / Original article Quite often mothers of preterm infants who were stored at 4 ºC until the time of processing are admitted to the neonatal intensive care units (less than 8 hours) performed in the Microbiology (NICU) are at home while their babies are hos- Laboratory (School of Pharmacy and Biochemis- pitalized, therefore milk sometimes is expressed try, Universidad de Buenos Aires) by staff blin- somewhere else rather than in the healthcare fa- ded at their origin (expressed at home or at the cility. Precautions are necessary to prevent conta- healthcare facility). mination; it is quite likely that expressing breast Case selection: samples were collected once a milk at home, where there is less control, will week due to operative reasons. In order to ensu- result in a more significant contamination than re their representatation, the day of each week in doing it at the healthcare facility. which collection would take place was determi- The objective of this study was to compare the ned a priori based on a table of random numbers degree of contamination of breast milk expressed (by assigning a consecutive number from 1 to 5). at a healthcare facility versus at home. On each selected day, a couple of milk samples were collected from each participating mother POPULATION, MATERIAL AND METHODS (one previously expressed at home and the other A cross-sectional study was performed to test one at the healthcare facility). All those mothers breast milk samples obtained from mothers of who met the inclusion criteria accepted to parti- newborn infants with ≤35 weeks of gestational cipate in the study. age who received enteral feeding between April Microbiological screening: for the purpose of 17, 2009 and January 6, 2011. All mothers of hos- this study, a milk sample that had more than 105 pitalized preterm infants were included; breast CFU/mL of mesophilic aerobic bacteria,6 presen- milk samples from mothers with infectious con- ce of Escherichia coli, enterobacteria, Staphylococcus ditions considered a contraindication to breast- aureus, Streptococcus faecalis, Pseudomonas, Salmo- feeding or who used illegal drugs or medications nella or fungi was considered to be contaminated. not allowed during breastfeeding were excluded. Microbiological test: quantitative tests of me- Newborn infant status: in all cases the gesta- sophilic aerobic bacteria, fungi and yeast count, tional age, birth weight, and presence of food in- and enterobacteria count were done as indica- tolerance (vomiting, abdominal bloating, diarrhea tors of microbiological safety, as well as the exa- or gastric retention ≥25% of the volume) or necro- mination in 1 mL of milk of species of Salmonella, tizing enterocolitis were recorded. coliforms, Escherichia coli, Staphylococcus aureus, Breast milk samples: pairs of breast milk ex- Pseudomonas aeruginosa and Burkholderia cepacia. pressed at home or at the NICU on the same day Mesophilic aerobic count: it was done by deep- were obtained. Instructions describing all the pro- seeding in Plate Count Agar (PCA), by adding cedures related to milk expression were provided 0.1% of skimmed milk powder, and incubated together with a sterilized bottle and a thermal bag during 48 hours at 35°C. for storage and transportation. Milk expressed at Fungi and yeast count: it was performed by the breast pumping room in the NICU was ob- deep-seeding in Yeast Extract Glucose Chloram- tained via an aseptic technique with an electrical phenicol (YGC) agar plates, and incubated during pump, a milk pump sterilized in steam during 90 5 days at 25°C. minutes and with simple packing, hair tied back, Enterobacteria count: it was performed by no jewelry, rolled up sleeves and hands washed deep-seeding in Violet Red Bile Glucose Agar with liquid soap before milk expression. (VRBGA) plates, and incubated during 24 days Though breast milk could be expressed at ho- at 35°C. me manually or with a milk pump, all mothers Testing for E. coli and coliforms: 1 mL of milk used a milk pump and transported the milk to was incubated during 24/48 hours at 35°C in lac- the healthcare facility in a sterilized bottle inside tose broth. After this period of enrichment, it was an insulated container, packed in ice. Milk expres- inoculated in a hooded tube that contained bright sion procedures were different at the healthcare green broth; in those tubes that presented growth facility in comparison to procedures used at ho- (turbidity and gas), an isolation on chromogenic me because the former were monitored following agar was done to confirm E. coli and coliforms. the standard hospital procedures while at home Testing for Salmonella: from the lactose broth, it was not, as it happens in “real life”. Date of ex- two tubes were seeded, one with Rappaport- pression, sample temperature, volume and appea- Vassiliadis broth and one with tetrationate broth, rance were recorded in all the cases. All samples which were incubated during 24 hours at 35°C Comparison of the risk of microbiological contamination between samples of breast milk obtained at home and at a healthcare facility / 117 and then isolated on xylose-lysine-desoxycholate The frequency of categorical variables is des- (XLD) and bismuth-sulfite (BS) agar plate surfa- cribed by percentages with their 95% confidence ces. In case of yielding typical colonies, biochemi- intervals. The association between the contamina- cal tests with API 20E were done. tion and the source of the breast milk was evalua- Testing for Staphylococcus aureus: 1 mL of ted with a χ2 test, assuming a two tailed p < 0.05 breast milk was incubated during 24/48 hours at significance level; the OR was estimated with its 35°C in trypticase soy broth (TSB), after this pe- corresponding 95% confidence intervals.