AUTHOR=Li Xiaoliang , Zhou Yun , Zhan Xianlin , Huang Weichun , Wang Xing 

TITLE=Breast Milk Is a Potential Reservoir for Livestock-Associated Staphylococcus aureus and Community-Associated Staphylococcus aureus in Shanghai, China

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02639

DOI=10.3389/fmicb.2017.02639

ISSN=1664-302X

ABSTRACT=<p>Breast milk is the first choice in feeding newborn infants and provides multiple benefits for their growth and development. <italic>Staphylococcus aureus</italic> usually exists in breast milk and is considered one of the most important causative infective agents. To be effective in preventing and controlling <italic>S. aureus</italic> infections among infants, the aim of this study was to determine the occurrence and molecular characteristics of <italic>S. aureus</italic> isolated from 1102 samples of breast milk between 2015 and 2016 in Shanghai, China. Out of 71 <italic>S. aureus</italic> strains isolated, 15 (21.1%, 15/71) were MRSA and all the strains were characterized by <italic>spa</italic> typing, Multi-Locus Sequence Typing, SCC<italic>mec</italic> typing, antibiotic resistance testing and virulence-associated genes. A total of 18 distinct sequence types (STs) and 36 <italic>spa</italic> types were identified within the 71 isolates, among which the most frequently represented was ST398 (19.7%, 14/71), followed by ST7 (18.3%, 13/71), ST59 (16.9%, 12/71). The three predominant STs accounted for more than one half of all <italic>S. aureus</italic> isolates. The most prevalent <italic>spa</italic> types were <italic>t</italic>091 (12.7%, 9/71), followed by <italic>t</italic>571 (8.5%, 6/71), <italic>t</italic>189 (7.0%, 5/71), <italic>t</italic>034 (5.6%, 4/71), <italic>t</italic>437 (5.6%, 4/71), and <italic>t</italic>701 (4.2%, 3/71). All MRSA isolates belonged to SCC<italic>mec</italic> IV and V, accounting for 66.7 and 33.3% respectively. Notably, 23 (32.4%) <italic>S. aureus</italic> strains were multidrug resistance (MDR), including 4 (5.6%) MRSA and 19 (26.8%) MSSA strains, and MDR isolates were mostly resistant to penicillin, erythromycin and clindamycin. All isolates exhibited simultaneous carriage of at least 5 of 33 possible virulence genes and the most prevalent genes detected were <italic>icaA</italic> (100%), <italic>clfA</italic> (100%), <italic>hla</italic> (100%), <italic>sdrC</italic> (94.4%), <italic>hlg</italic>2 (88.7%), <italic>lukE</italic> (57.8%). 39 (54.9%, 39/71) isolates, including 9 (12.7%) of MRSA isolates, harbored ≥10 tested virulence genes evaluated in this study. The <italic>pvl</italic> gene was detected in 8 strains, which represented 5 different STs, with ST59 being the most one. Overall, our findings showed that <italic>S. aureus</italic> strains isolated from breast milk were mainly MSSA (78.9%, 56/71) and exhibited high genetic diversity in Shanghai area of China. Breast milk was a reservoir for LA-SA (ST398) and CA-SA (ST59), which was likely a vehicle for transmission of multidrug-resistant <italic>S. aureus</italic> and MRSA lineages. This is a potential public health risk and highlights the need for good hygiene practices to reduce the risk of infant infections.</p>