Prevalence of Staphylococcus aureus Contamination in Infant Foods and the Detection of Antibiotic Resistance Genes and New Enterotoxin Genes
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Abstract:
The prevalence of S. aureus contamination in infant formula milk powder (PIF) and infant rice cereal (IRC) was investigated in this study, and the corresponding antibiotic resistance genes and novel enterotoxin genes were detected. A total of 692 PIF and IRC samples of different brands were collected in the Shaanxi province of China in 2010 and 2012 and screened for S. aureus. Polymerase chain reaction (PCR) was employed to detect 31 antibiotic resistance genes and nine novel enterotoxin genes among the isolates. The overall positive rate for S. aureus in 692 samples was 7.80%, including 8.17% among the samples collected in 2010 and 7.38% among the samples collected in 2012. Among the 75 isolated strains of S. aureus, 12 types of antibiotic resistance genes and two novel enterotoxin gene profiles were detected. The resistance gene with the highest detection rate was tetK (72.00%), followed by blaZ (36.00%), ermC (29.33%), tet(K)F (21.33%), linA/linA (12.00%), dfrG (8.00%), tetL (6.67%), and acc(6') (5.33%), and the genes with the lowest detection rate were ermB, msrA, msrB, and drfK (all at 1.33%). Among the novel enterotoxin genes, only sen (44.00%) and ser (4.00%) were detected. No significant difference was found in the contamination rate of S. aureus among the samples from different sampling years and production months and with different shelf lives. Additionally, the primary antibiotic resistance genes that these strains carried conferred resistance to penicillin, tetracycline, and macrolide, and the main virulence gene was sen.
