军曹鱼养殖水体及其肠道异养细菌的耐药性研究

选用常用的15种抗生素,通过纸片扩散法(Kirby-Bauer纸片扩散法,简称K-B法),参照NCCLS抗生素敏感试验操作标准,并以金黄色葡萄球菌Staphylococcus aureus ATCC25923和大肠埃希菌Esсheriсhia coli ATCC25922为质控菌株,对周年监测分离自养殖军曹鱼水体及肠道的188株优势菌(包含9个菌属)进行了药物敏感性研究.结果显示,抑菌最强的是环丙沙星(耐药率为0),其次是氯霉素、诺氟沙星、庆大霉素、多粘菌素B、复方新诺明,耐药率均小于40%;抑菌效果最差的依次为羧苄青霉素、青霉素G、氨苄青霉素、痢特灵、利福平,耐药率均在40%以上,其中多重耐药的菌株(对4种或4种以上抗生素产生耐药性)共12株,包括水体菌9株和肠道菌3株.     

Interactive effects of multiscale diversification practices on farmland bird stress

Farmland diversification practices (i.e., methods used to produce food sustainably by enhancing biodiversity in cropping systems) are sometimes considered beneficial to both agriculture and biodiversity, but most studies of these practices rely on species richness, diversity, or abundance as a proxy for habitat quality. Biodiversity assessments may miss early clues that populations are imperiled when species presence does not imply persistence. Physiological stress indicators may help identify low-quality habitats before population declines occur. We explored how avian stress indicators respond to on-farm management practices and surrounding seminatural area (1-km radius) across 21 California strawberry farms. We examined whether commonly used biodiversity metrics correlate with stress responses in wild birds. We used ∼1000 blood and feather samples and body mass and wing chord measurements, mostly from passerines, to test the effects of diversification practices on four physiological stress indicators: heterophil to lymphocyte ratios (H:L), body condition, hematocrit values, and feather growth rates of individual birds. We then tested the relationship between physiological stress indicators and species richness, abundance, occurrence, and diversity derived from 285 bird point count surveys. After accounting for other biological drivers, landscape context mediated the effect of local farm management on H:L and body condition. Local diversification practices were associated with reduced individual stress in intensive agricultural landscapes but increased it in landscapes surrounded by relatively more seminatural area. Feathers grew more slowly in landscapes dominated by strawberry production, suggesting that nutritional condition was lower here than in landscapes with more crop types and seminatural areas. We found scant evidence that species richness, abundance, occurrence, or diversity metrics were correlated with the individual's physiological stress, suggesting that reliance on these metrics may obscure the impacts of management on species persistence. Our findings underscore the importance of considering landscape context when designing local management strategies to promote wildlife conservation.