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Updated: Dec 11, 2025
Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR RS-PCR
Published on: November 4, 2016
Molecular characterization of methicillin-resistant and methicillin-sensitive Staphylococcus aureus isolates from
Jéssica Bomfim de Almeida1,2, Suzi Pacheco de Carvalho1, Lucas S C da Silva2
1Universidade Estadual de Santa Cruz (UESC), Campus Soane Nazaré de Andrade,, Ilhéus, Brazil.
Abstract:
Human milk is the best nutrient for infants. The donor human milk is stored in a milk bank before pasteurization. However, the human milk is not sterile and could be colonized with different types of bacteria. Many studies have shown S. aureus to be the most prevalent potential pathogen detected in human milk. This study characterized 22 methicillin-resistant and methicillin-sensitive Staphylococcus aureus isolates from raw human milk for the presence of virulence genes and agr type. Moreover, the genotypic as identified characterization was realized. The presence of virulence genes sei, seg, sec, seh, and etb was identified in resistant and sensitive strains. We observed the predominance of agr type II. The presence of SCCmec IV (67%, 4/6) and V (33%, 2/6) characterized resistant strains as CA-MRSA. Endemic lineages detected (ST1635/CC5-t002, ST5/CC5-t002, ST72/CC5-t126, ST1/CC1-t127, ST45/CC45-t065, and ST398/t1451) could be related to epidemic clones, such as USA800/ST5, USA700/ST72, USA400/ST1, USA600/ST45, and ST398. This study made it possible to understand the characteristics of virulence and clonality of some strains that circulate in breast milk in our region. The discovery of human milk colonization by MSSA and MRSA strains with molecular characteristics similar to infectious clones spread globally demonstrates the importance of monitoring strains that can spread and cause serious infections.
Insights
This study found that Staphylococcus aureus strains in donor human milk carry virulence genes and are similar to global epidemic clones. Monitoring these milk-borne bacteria is crucial for infant health and preventing infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Public Health
Background:
- Human milk is vital for infant nutrition, but donor milk may harbor bacteria.
- Staphylococcus aureus is a common pathogen found in human milk.
- Understanding the characteristics of S. aureus in milk is essential for safety.
Purpose of the Study:
- To characterize Staphylococcus aureus isolates from raw donor human milk.
- To investigate the presence of virulence genes and agr types in these isolates.
- To determine the genotypic relatedness of S. aureus strains to global epidemic clones.
Main Methods:
- Isolation and characterization of 22 S. aureus strains from raw human milk.
- Detection of virulence genes (sei, seg, sec, seh, etb) and agr typing.
- Genotypic identification including SCCmec typing and sequence typing (ST) for MRSA strains.
Main Results:
- Both methicillin-resistant (MRSA) and methicillin-sensitive (MSSA) S. aureus strains were identified.
- Predominant agr type was II; SCCmec types IV and V were found in MRSA strains, indicating CA-MRSA.
- Identified endemic lineages (e.g., ST1635/CC5, ST72/CC5) are related to globally recognized epidemic clones (e.g., USA800/ST5, USA700/ST72).
Conclusions:
- Human milk can be colonized by MSSA and MRSA with molecular profiles similar to globally circulating infectious clones.
- These findings highlight the importance of monitoring bacterial strains in donor milk.
- This surveillance is critical to prevent the spread of potentially serious infections in vulnerable infants.
