The effect of lemongrass oil and its major components on clinical isolate mastitis pathogens and their mechanisms of action on Staphylococcus aureus DMST 4745

The aims of this study were to investigate the antibacterial activity of lemongrass oil (LG) and its major components which were citral, geraniol and myrcene, against four strains of clinically isolated bovine mastitis pathogens, including Staphylococcus aureus, Streptococcus agalactiae, Bacillus cereus and Escherichia coli by the broth microdilution method, as well as their activity on S. aureus biofilm formation. Attempts to clarify their mechanisms of action by investigation of the effects on intracellular material leakage and morphological changes of S. aureus DMST 4745 were also made. The results demonstrate that S. agalactiae and B. cereus are more susceptible to LG, citral and geraniol than S. aureus and E. coli. Moreover, they also inhibit S. aureus biofilm formation and exhibit effective killing activities on preformed biofilms. The LG appears to have multiple targets in the bacterial cell, depending on concentration used as well as the amount of its components.     

Prevalence of zoonotic Bartonella species among rodents and shrews in Thailand

We investigated the prevalence of Bartonella species in 10 rodent and one shrew species in Thailand. From February 2008 to May 2010, a total of 375 small animals were captured in 9 provinces in Thailand. Bartonella strains were isolated from 57 rodents (54 from Rattus species and 3 from Bandicota indica) and one shrew (Suncus murinus) in 7 of the 9 provinces, and identified to the species level. Sequence analysis of the citrate synthase and RNA polymerase β subunit genes identified the 58 isolates from each Bartonella-positive animal as B. tribocorum in 27 (46.6%) animals, B. rattimassiliensis in 17 (29.3%) animals, B. elizabethae in 10 (17.2%) animals and B. queenslandensis in 4 (6.9%) animals. R. norvegicus, R. rattus, and Suncus murinus carried B. elizabethae, which causes endocarditis in humans. The prevalence of Bartonella bacteremic animals by province was 42.9% of the animals collected in Phang Nga, 26.8% in Chiang Rai, 20.4% in Sa Kaeo, 16.7% in Nakhon Si Thammarat, 12.0% in Surat Thani, 9.1% in Mae Hong Son and Loei Provinces.