Antimicrobial resistance tendency and collateral sensitivity of Staphylococcus aureus adapted to antibiotics or extracts of medicinal plants grown in Viet Nam.

Antimicrobial resistance has silently turned into one of the biggest threats to global health, marking the fall of the Golden age of antibiotics. In the search for antibiotic replacement or enhancement, plant-derived natural compounds have attracted lots of interest. Even though firmly believed, the low-resistance tendency of pathogenic bacteria against plant extracts has been scarcely demonstrated. In this study, we investigated the antibacterial activities of diethyl ether extracts from six medicinal plants grown in Viet Nam against Staphylococcus aureus and its variants, which were in vitro adapted to the same extracts. After 30 passages of S. aureus growing under sub-lethal concentrations of plant extracts or antibiotics, the bacteria slowly adapted to the extracts while rapidly resisting the antibiotics. Most of the resulting strains obtained from the adaptation to plant extracts were collaterally sensitive to antibiotics. In contrast, antibiotic-adapted strains showed cross-resistance to both antibiotics and extracts. The findings provided evidence of the low-resistance tendency of S. aureus to antimicrobial plant extracts. It is the first time a collateral antibiotic sensitivity of S. aureus adapted to natural compounds has been observed, suggesting an alternative approach to fight antibiotic resistance.

High prevalence of anti-Trichinella IgG in domestic pigs of the Son La province, Vietnam.

Although several outbreaks of Trichinella infection among humans have occurred in northwestern Vietnam, no information is available on the circulation of Trichinella among domestic pigs. The objective of the present study was to estimate the seroprevalence of anti-Trichinella IgG in free-roaming pigs (Sus scrofa) in the Son La province of northwestern Vietnam, where a human outbreak of trichinellosis occurred in June 2008. Serum samples were collected from free-roaming pigs of four communes of the Bac Yen district (Son La province) and tested for Trichinella antibodies with a commercial ELISA kit using excretory/secretory antigens. Of 1035 pigs from which serum samples were collected, 206 were positive (19.9%). There was a significant difference in the prevalence among communes (chi(2)=22.87, 3 d.f., p<0.0001). Muscle samples from 76 serologically positive pigs were tested by artificial digestion. Trichinella larvae were detected in 11 (14.5%) of them. The larvae were identified by multiplex PCR as Trichinella spiralis. This study provides the first data on the circulation of T. spiralis in domestic pigs reared in Vietnam, and the results are useful for evaluating the risk of infection for humans. The results indicate that pigs act as a reservoir and play an important role in the maintenance of the domestic cycle of T. spiralis in northwestern Vietnam.