RESUMO
The development of powerful sequencing techniques has allowed, albeit with some biases, the identification and inventory of complex microbial communities that inhabit different body sites or body fluids, some of which were previously considered sterile. Notably, milk is now considered to host a complex microbial community with great diversity. Milk microbiota is now well documented in various hosts. Based on the growing literature on this microbial community, we address here the question of what milk microbiota is. We summarize and compare the microbial composition of milk in humans and in ruminants and address the existence of a putative core milk microbiota. We discuss the factors that contribute to shape the milk microbiota or affect its composition, including host and environmental factors as well as methodological factors, such as the sampling and sequencing techniques, which likely introduce distortion in milk microbiota analysis. The roles that milk microbiota are likely to play in the mother and offspring physiology and health are presented together with recent data on the hypothesis of an enteromammary pathway. At last, this fascinating field raises a series of questions, which are listed and commented here and which open new research avenues.
RESUMO
Humans are a natural reservoir of Staphylococcus aureus and asymptomatic colonization is far more common than infection. The aim of this work was to characterize genotypically 68 S. aureus strains isolated from nasal swabs of healthy people and from human clinical infections. A total of fourteen (20%) strains were susceptible to all the antimicrobials tested. The strains isolated from nasal swabs showed the lowest percentages of resistance. Resistance to one or more than one antibiotics tested was detected in 83% and 70% of the S. aureus strains isolated from clinical infections and nasal swabs, respectively. All of the 68 S. aureus strains were subject to RAPD-PCR analysis. Cluster A-I grouped 42 (87%) clinical infection strains and cluster A-II grouped 13 (65%) strains isolated from nasal swabs suggesting a genetic relationship among S. aureus strains. Cluster A-II grouped 65% of the S. aureus strains associated with the anterior nares, suggesting that these strains may be adapted to this site. Furthermore, five RAPD profiles isolated from nasal swabs, belonged to clusters B to F, were similar to strains isolated from clinical infection, suggesting that they might have a high propensity to cause disease. The results of the present study allow a characterization of S. aureus strains isolated from humans and shows that some S. aureus genotypes from nasal swabs are similar to the genotypes obtained from clinical infections, suggesting that clinical isolates may be originated from human normal flora.
