Breast Milk Is a Potential Reservoir for Livestock-Associated and Community-Associated in Shanghai, China.

Breast milk is the first choice in feeding newborn infants and provides multiple benefits for their growth and development. usually exists in breast milk and is considered one of the most important causative infective agents. To be effective in preventing and controlling infections among infants, the aim of this study was to determine the occurrence and molecular characteristics of isolated from 1102 samples of breast milk between 2015 and 2016 in Shanghai, China. Out of 71 strains isolated, 15 (21.1%, 15/71) were MRSA and all the strains were characterized by typing, Multi-Locus Sequence Typing, SCC typing, antibiotic resistance testing and virulence-associated genes. A total of 18 distinct sequence types (STs) and 36 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 isolates. The most prevalent types were 091 (12.7%, 9/71), followed by 571 (8.5%, 6/71), 189 (7.0%, 5/71), 034 (5.6%, 4/71), 437 (5.6%, 4/71), and 701 (4.2%, 3/71). All MRSA isolates belonged to SCC IV and V, accounting for 66.7 and 33.3% respectively. Notably, 23 (32.4%) 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 (100%), (100%), (100%), (94.4%), 2 (88.7%), (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 gene was detected in 8 strains, which represented 5 different STs, with ST59 being the most one. Overall, our findings showed that 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 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.