Juan M. Rodríguez

Is meconium from healthy newborns actually sterile

In a previous study, bacteria were able to be isolated from umbilical cord blood of healthy neonates and from murine amniotic fluid obtained by caesarean section. This suggested that term fetuses are not completely sterile and that a prenatal mother-to-child efflux of commensal bacteria may exist. Therefore, the presence of such bacteria in meconium of 21 healthy neonates was investigated. The identified isolates belonged predominantly to the genuses Enterococcus and Staphylococcus. Later, a group of pregnant mice were orally inoculated with a genetically labelled E. fecium strain previously isolated from breast milk of a healthy woman. The labelled strain could be isolated and PCR-detected from meconium of the inoculated animals obtained by caesarean section one day before the predicted date of labor. In contrast, it could not be detected in samples obtained from a non-inoculated control group.

Isolation of Commensal Bacteria from Umbilical Cord Blood of Healthy Neonates Born by Cesarean Section

In a previous study, lactic acid bacteria were isolated from meconium obtained from healthy neonates born by cesarean section. Such a finding suggested that term fetuses are not completely sterile, and that a mother-to-child efflux of commensal bacteria may exist. Therefore, presence of such bacteria in umbilical cord blood of healthy neonates born by elective cesarean section was investigated. The blood samples were submitted to an enrichment step and then inoculated onto agar plates. All the identified isolates belonged to the genus Enterococcus, Streptococcus, Staphylococcus, or Propionibacterium. Later, a group of pregnant mice were orally inoculated with a genetically labeled E. faecium strain previously isolated from breast milk of a healthy woman. The labeled strain could be isolated and polymerase chain reaction detected from the amniotic fluid of the inoculated animals. In contrast, it could not be detected in the samples obtained from a noninoculated control group.

The human milk microbiota: origin and potential roles in health and disease.

Human milk has been traditionally considered sterile; however, recent studies have shown that it represents a continuous supply of commensal, mutualistic and/or potentially probiotic bacteria to the infant gut. Culture-dependent and -independent techniques have revealed the dominance of staphylococci, streptococci, lactic acid bacteria and bifidobacteria in this biological fluid, and their role on the colonization of the infant gut. These bacteria could protect the infant against infections and contribute to the maturation of the immune system, among other functions. Different studies suggest that some bacteria present in the maternal gut could reach the mammary gland during late pregnancy and lactation through a mechanism involving gut monocytes. Thus, modulation of maternal gut microbiota during pregnancy and lactation could have a direct effect on infant health. On the other hand, mammary dysbiosis may lead to mastitis, a condition that represents the first medical cause for undesired weaning. Selected strains isolated from breast milk can be good candidates for use as probiotics. In this review, their potential uses for the treatment of mastitis and to inhibit mother-to-infant transfer of HIV are discussed.

The composition of the gut microbiota throughout life, with an emphasis on early life

Abstract The intestinal microbiota has become a relevant aspect of human health. Microbial colonization runs in parallel with immune system maturation and plays a role in intestinal physiology and regulation. Increasing evidence on early microbial contact suggest that human intestinal microbiota is seeded before birth. Maternal microbiota forms the first microbial inoculum, and from birth, the microbial diversity increases and converges toward an adult-like microbiota by the end of the first 3–5 years of life. Perinatal factors such as mode of delivery, diet, genetics, and intestinal mucin glycosylation all contribute to influence microbial colonization. Once established, the composition of the gut microbiota is relatively stable throughout adult life, but can be altered as a result of bacterial infections, antibiotic treatment, lifestyle, surgical, and a long-term change in diet. Shifts in this complex microbial system have been reported to increase the risk of disease. Therefore, an adequate establishment of microbiota and its maintenance throughout life would reduce the risk of disease in early and late life. This review discusses recent studies on the early colonization and factors influencing this process which impact on health.

Isolation of Bifidobacteria from Breast Milk and Assessment of the Bifidobacterial Population by PCR-Denaturing Gradient Gel Electrophoresis and Quantitative Real-Time PCR

ABSTRACT The objective of this work was to elucidate if breast milk contains bifidobacteria and whether they can be transmitted to the infant gut through breastfeeding. Twenty-three women and their respective infants provided samples of breast milk and feces, respectively, at days 4 to 7 after birth. Gram-positive and catalase-negative isolates from specific media with typical bifidobacterial shapes were identified to the genus level by F6PPK (fructose-6-phosphate phosphoketolase) assays and to the species level by 16S rRNA gene sequencing. Bifidobacterial communities in breast milk were assessed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE), and their levels were estimated by quantitative real-time PCR (qRTi-PCR). Bifidobacteria were present in 8 milk samples and 21 fecal samples. Bifidobacterium breve, B. adolescentis, and B. bifidum were isolated from milk samples, while infant feces also contained B. longum and B. pseudocatenulatum. PCR-DGGE revealed the presence of one to four dominant bifidobacterial bands in 22 milk samples. Sequences with similarities above 98% were identified as Bifidobacterium breve, B. adolescentis, B. longum, B. bifidum, and B. dentium. Bifidobacterial DNA was detected by qRTi-PCR in the same 22 milk samples at a range between 40 and 10,000 16S rRNA gene copies per ml. In conclusion, human milk seems to be a source of living bifidobacteria for the infant gut.

Probiotic Potential of 3 Lactobacilli Strains Isolated From Breast Milk

Breast milk is an important factor in the initiation, development, and composition of the neonatal gut microbiota. In a previous study, the authors isolated lactic acid bacteria from milk of healthy mothers. Since some of the identified isolates belonged to the genus Lactobacillus, the objective of this work was to evaluate the probiotic potential of 2 Lactobacillus gasseri and 1 Lactobacillus fermentu strains. Different assays, including survival to conditions simulating those existing in the gastrointestinal tract, production of antimicrobial compounds, adherence to intestinal cells, production of biogenic amines, degradation of mucin, enzymatic profile, and pattern of antibiotic resistance, were performed. Globally, the results showed that the probiotic potential of lactobacilli isolated from milk of healthy mothers is, at least, similar to that of the strains commonly used in commercial probiotic products. This fact, together with the presence of prebiotic substances, indicates that breast milk is a natural synbiotic food. J Hum Lact. 21(1):8-17.

Pediocin PA-1, a wide-spectrum bacteriocin from lactic acid bacteria

Referee: Dr. Helen Dodd, Food Safety Science Division, Institute of Food Research, Norwich Research Park, Colney NR4 7UA, Norwich, United Kingdom Pediocin PA-1 is a broad-spectrum lactic acid bacteria bacteriocin that shows a particularly strong activity against Listeria monocytogenes, a foodborne pathogen of special concern among the food industries. This antimicrobial peptide is the most extensively studied class IIa (or pediocin family) bacteriocin, and it has been sufficiently well characterized to be used as a food biopreservative. This review focuses on the progress that have been made in the elucidation of its structure, mode of action, and biosynthesis, and includes an overview of its applications in food systems. The aspects that need further research are also addressed. In the future, protein engineering, genetic engineering and/or chemical synthesis may lead to the development of new antimicrobial peptides with improved properties, based on some features of the pediocin PA-1 molecule.

Antimicrobial activity of phenolic acids against commensal, probiotic and pathogenic bacteria

Phenolic acids (benzoic, phenylacetic and phenylpropionic acids) are the most abundant phenolic structures found in fecal water. As an approach towards the exploration of their action in the gut, this paper reports the antimicrobial activity of thirteen phenolic acids towards Escherichia coli, Lactobacillus spp., Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. The growth of E. coli ATCC 25922 was inhibited by only four of the phenolic acids tested at a concentration of 1000 microg/mL, whereas pathogenic E. coli O157:H7 (CECT 5947) was susceptible to ten of them. The genetically manipulated E. coli lpxC/tolC strain was highly susceptible to phenolic acids. The growth of lactobacilli (Lactobacillus paraplantarum LCH7, Lactobacillus plantarum LCH17, Lactobacillus fermentum LPH1, L. fermentum CECT 5716, Lactobacillus brevis LCH23, and Lactobacillus coryniformis CECT 5711) and pathogens (S. aureus EP167 and C. albicans MY1055) was also inhibited by phenolic acids, but to varying extents. Only P. aeruginosa PAO1 was not susceptible to any of the phenolic compounds tested. Structure-activity relationships of phenolic acids and some of their diet precursors [(+)-catechin and (-)-epicatechin] were established, based on multivariate analysis of microbial activities. The antimicrobial properties of phenolic acids reported in this paper might be relevant in vivo.

Bacterial Diversity in Meconium of Preterm Neonates and Evolution of Their Fecal Microbiota during the First Month of Life

The establishment and succession of bacterial communities in infants may have a profound impact in their health, but information about the composition of meconium microbiota and its evolution in hospitalized preterm infants is scarce. In this context, the objective of this work was to characterize the microbiota of meconium and fecal samples obtained during the first 3 weeks of life from 14 donors using culture and molecular techniques, including DGGE and the Human Intestinal Tract Chip (HITChip) analysis of 16S rRNA amplicons. Culture techniques offer a quantification of cultivable bacteria and allow further study of the isolate, while molecular techniques provide deeper information on bacterial diversity. Culture and HITChip results were very similar but the former showed lower sensitivity. Inter-individual differences were detected in the microbiota profiles although the meconium microbiota was peculiar and distinct from that of fecal samples. Bacilli and other Firmicutes were the main bacteria groups detected in meconium while Proteobacteria dominated in the fecal samples. Culture technique showed that Staphylococcus predominated in meconium and that Enterococcus, together with Gram-negative bacteria such as Escherichia coli, Escherichia fergusonii, Klebsiella pneumoniae and Serratia marcescens, was more abundant in fecal samples. In addition, HITChip results showed the prevalence of bacteria related to Lactobacillus plantarum and Streptococcus mitis in meconium samples whereas those related to Enterococcus, Escherichia coli, Klebsiella pneumoniae and Yersinia predominated in the 3rd week feces. This study highlights that spontaneously-released meconium of preterm neonates contains a specific microbiota that differs from that of feces obtained after the first week of life. Our findings indicate that the presence of Serratia was strongly associated with a higher degree of immaturity and other hospital-related parameters, including antibiotherapy and mechanical ventilation.

Heterologous production of bacteriocins by lactic acid bacteria.

Over the last two decades, bacteriocins produced by lactic acid bacteria (LAB) have been the subject of considerable research and industrial interest due to their potential as food biopreservatives. The development of heterologous expression systems for such antimicrobial compounds may offer a number of advantages over native systems, such as facilitating the control of bacteriocin gene expression or achieving higher production levels. In addition, the heterologous production by food-grade LAB offers an attractive method for overcoming some of the adverse situations that may affect the effectiveness of some bacteriocins in food systems. Construction of multibacteriocinogenic strains or acquisition of antimicrobial properties by industrial strains are further objectives that can be achieved through the use of heterologous gene expression systems. The development of new biotechnological tools and recent advances in LAB genetics account for the escalating number of studies dealing with heterologous production of bacteriocins by such hosts. This paper reviews the literature published on the subject and compares the different experimental strategies that have been used up to the present for this purpose.