Abstract
BackgroundInfectious mastitis is a common condition during lactation and in fact, represents one of the main causes leading to a precocious weaning. The number of studies dealing with lactational mastitis is low and, up to now, the etiological diagnosis is frequently made on the basis of unspecific clinical signs. The aim of this study was to investigate the microbial diversity of breast milk in 20 women with lactational mastitis employing culture-dependent and culture-independent (PCR-DGGE) approaches.MethodsBreast milk samples were cultured in different media to investigate the presence of bacteria and/or yeasts, and a total of 149 representative isolates were identified to the species level by 16S rRNA gene PCR sequencing. The microorganisms recovered were compared with those found by PCR-DGGE analysis. To identify the DGGE profiles two reference markers of different microbial species were constructed. Sequence analysis of unknown bands was also performed.ResultsStaphylococci were the dominant bacterial group and Staphylococcus epidermidis was the dominant species. In a lower number of samples, other bacteria (mainly streptococci and a few gram-negative species) were also identified. Globally, PCR-DGGE results showed a good correlation with those obtained by culture-based methods. However, although DNA bands corresponding to different lactic acid bacteria were detected, such bacteria could not be isolated from the milk samples.ConclusionStaphylococci seem to be the main etiological agents of human lactational mastitis. The combined use of culture and molecular techniques allowed a better characterization of the bacterial diversity in milk from women suffering from infectious mastitis. Our results suggest that this condition could be the result of a disbiotic process where some of the bacterial species usually present in human milk outgrow (staphylococci) while others disappear (lactobacilli or lactococci).
Highlights
Infectious mastitis is a common condition during lactation and represents one of the main causes leading to a precocious weaning
The number of studies dealing with human lactational mastitis is low [1], Staphylococcus aureus and some streptococcal species have been traditionally considered as the main etiological agents [3]
Isolation of bacteria from the milk samples Globally, CNA and Baird Parker (BP) counts in the milk samples oscillated between 3.50 to 5.87 log10 cfu mL-1 and, with the exception of sample M13, no statistically significant differences between CNA and BP counts were found
Summary
Infectious mastitis is a common condition during lactation and represents one of the main causes leading to a precocious weaning. The number of studies dealing with lactational mastitis is low and, up to now, the etiological diagnosis is frequently made on the basis of unspecific clinical signs. Despite the advertences highlighting the need to analyze and cultivate human milk [4], the etiological diagnosis of infectious mastitis cases is frequently made on the sole basis of unspecific clinical signs [5,6]. This situation contrasts with that in Veterinary Medicine, where infectious mastitis leads to important economical losses in dairy farms and, microbiological and somatic cell analyses are performed routinely
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