Colostrum of Healthy Slovenian Mothers: Microbiota Composition and Bacteriocin Gene Prevalence

<div><p>Microbial communities inhabiting the breast milk microenvironment are essential in supporting mammary gland health in lactating women and in providing gut-colonizing bacterial 'inoculum' for their infants’ gastro-intestinal development. Bacterial DNA was extracted from colostrum samples of 45 healthy Slovenian mothers. Characteristics of the communities in the samples were assessed by polymerase chain reaction (PCR) coupled with denaturing gradient gel electrophoresis (DGGE) and by quantitative real-time PCR (qPCR). PCR screening for the prevalence of bacteriocin genes was performed on DNA of culturable and total colostrum bacteria. DGGE profiling revealed the presence of <i>Staphylococcus</i> and <i>Gemella</i> in most of the samples and exposed 4 clusters based on the abundance of 3 bands: <i>Staphylococcus epidermidis/Gemella</i>, <i>Streptococcus oralis/pneumonia</i> and <i>Streptococcus salivarius</i>. <i>Bacilli</i> represented the largest proportion of the communities. High prevalence in samples at relatively low quantities was confirmed by qPCR for enterobacteria (100%), <i>Clostridia</i> (95.6%), <i>Bacteroides-Prevotella</i> group (62.2%) and bifidobacteria (53.3%). Bacterial quantities (genome equivalents ml^-1) varied greatly among the samples; <i>Staphylococcus epidermidis</i> and staphylococci varied in the range of 4 logs, streptococci and all bacteria varied in the range of 2 logs, and other researched groups varied in the range of 1 log. The quantity of most bacterial groups was correlated with the amount of all bacteria. The majority of the genus <i>Staphylococcus</i> was represented by the species <i>Staphylococcus epidermidis</i> (on average 61%), and their abundances were linearly correlated. Determinants of salivaricin A, salivaricin B, streptin and cytolysin were found in single samples. This work provides knowledge on the colostrum microbial community composition of healthy lactating Slovenian mothers and reports bacteriocin gene prevalence.</p></div

(a) Normalized distribution of detected bacterial groups across the sample set (one dot represents % of the detected group’s specific DNA in relation to all bacterial DNA in the sample).

<p>(a, b). (b) Distribution of genome equivalents ml-1 colostrum for detected bacterial groups across the investigated maternal population.</p

Correlation of <i>Staphylococcus</i> and <i>Staphylococcus epidermidis</i> in 29 colostrum samples in which both groups were detected.

<p>The data are presented as copies (GE) ml^-1.</p

Distribution of the relative fluorescence (abundance, %) of major bands (with signal above 2% of total sample fluorescence) in a sample set together with presumptive band identification.

<p>The overlaid box plot represents the values (circles), the box medians and interquartile ranges, and error bars (5^th and 95^th percentiles).</p

Cultivation media, conditions and copy number estimates of traced bacterial operons in the standard curve calibration.

<p>^aIM <i>Microbial Collection of Institute of Dairy Science and Probiotics</i>, Biotechnical Faculty, University of Ljubljana, Slovenia</p><p>^aDSM <i>Deutsche Sammlung von Mikroorganismen und Zellkulturen</i>, Braunschweig, Germany</p><p>^bBHI Brain Heart Infusion Broth (Merck, Darmstadt, Germany)</p><p>^bM17 Broth acc. to TERZAGHI (Merck, Darmstadt, Germany)</p><p>^bMRS de Man, Rogosa and Sharpe Medium (Merck, Darmstadt, Germany)</p><p>^c 16S rRNA operon copy numbers of target species were derived from the rrnDB database</p><p>Cultivation media, conditions and copy number estimates of traced bacterial operons in the standard curve calibration.</p