Prevalence and characterization of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus isolated from retail yak butter in Tibet, China

Abstract

This study aimed to investigate the prevalence, molecular characteristics and antibiotic resistance of Staphylococcus aureus isolates from yak butter in Tibet, China. A total of 218 yak butter samples were collected from retail stores in Tibet and screened for Staph. aureus. Furthermore, the virulence genes, resistance genes, antimicrobial susceptibility, and molecular typing [pulsed-field gel electrophoresis (PFGE), multilocus sequence typing, and staphylococcal protein A (spa) typing] of Staph. aureus isolates were detected. The results showed that 12.4% of yak butter samples were contaminated with Staph. aureus, including 5 samples positive for methicillin-resistant Staph. aureus (MRSA). Among all isolates, 96.3% harbored one or more virulence genes, including classical (sea and sec), novel enterotoxin-encoding genes (seh, sek, sel, and seq), and hemolysin genes (hla and hld). All isolates were resistant to at least 2 different antibiotic classes, and the isolates were most commonly resistant to sulfonamides, β-lactams, and erythromycin. For resistance genes, blaZ (74.1%) was most frequently detected, followed by dfrG (51.9%), erm(B) (22.2%), mecA (18.5%), tet(K) (14.8%), aph(2″)-Ia, aph(3′)-III, and ant(6)-Ia (11.1% for each), and erm(C) (7.4%). We detected 8 spa types, 6 sequence types (ST), and 5 clonal complex (CC) types. In addition, 1 isolate of Staph. aureus was nontypeable. We found that CC1-ST1-t559 (55.6%) was the most predominant clone, followed by CC59-ST59-t437 (11.1%), CC5-ST5-t002 (7.4%), CC1-ST1, CC1-ST1-t114, CC1-ST573-t4938, CC1-ST573-t8915, CC30-ST30-t021, and CC25-ST25-t167 (3.7% for each). For PFGE typing, a total of 5 clusters and 15 pulsotypes were generated, and some isolates from different samples showed indistinguishable pulsotypes. Our findings suggest that yak butter produced in Tibet, China, could be contaminated by Staph. aureus strains, including MRSA strains, carrying various virulence and resistance genes, representing multiple antimicrobial resistance phenotypes. The presence of potentially virulent and antibiotic-resistant Staph. aureus strains in yak butter poses a potential threat to consumers, and appropriate measures need to be taken in the production chain to reduce the occurrence of Staph. aureus in yak butter.

Exploring novel peptides in adzuki bean and mung bean hydrolysates with potent antibacterial activity

“…Similarly, in the research conducted by Zhang et al . (2023b), the segment with an MW ranging from 2000 to 3000 Da, derived by Flavourzyme from yak casein, exhibited superior antibacterial activity against S. aureus . The peptide fraction with a MW below 3000 Da demonstrated the higher antibacterial activity among all fractions.…”

“…In accordance with our findings, the antibacterial peptide APKHKEMPFPKYP derived from yak casein maintained a positive charge at neutral pH. This peptide was composed of 53.85% hydrophobic amino acids, with the K prominently featured within its sequence (Zhang et al ., 2023b). This peptide was predicted to have a strong affinity toward DNA gyrase and DHFR, two critical enzymes for sustaining bacterial growth, through various noncovalent bonds such as salt bridges, π–π stacking, hydrogen bonds and hydrophobic interactions.…”

Antimicrobial Usage and Detection of Multidrug-Resistant Staphylococcus aureus: Methicillin- and Tetracycline-Resistant Strains in Raw Milk of Lactating Dairy Cattle

“…In the neighboring country, India, Ganai et al [ 48 ] reported that 44.1% of the S. aureus isolates were MRSA. Other studies conducted in Turkey, Egypt, China, and Algeria reported 75.4%, 35.7%, 9.61%, and 4.1% prevalences of MRSA [ 49 , 50 , 51 , 52 ]. The main causes of increased MRSA prevalence are the irregular use of beta-lactam antibiotics and poor hygienic conditions during milking [ 35 ].…”

The novel fosfomycin resistance gene fosY is present on a genomic island in CC1 methicillin-resistant Staphylococcus aureus

“…In addition, several isolates collected from livestock were included in the evolutionary tree. These livestock-associated strains were almost all MSSA and distributed worldwide and were interspersed with human strains in the same clades, although some studies have reported that the livestock-associated ST1 strains emerged in China [ 10 , 39 , 40 ]. However, the lack of complete genome information is a limitation to further analyse the relationship between the livestock-associated ST1 in China and the clinical ST1 in our study.…”